1601
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Schanck A, Mingeot-Leclercq MP, Tulkens PM, Carrier D, Smith IC, Jarrell HC. Interactions of aminoglycoside antibiotics with phospholipids. A deuterium nuclear magnetic resonance study. Chem Phys Lipids 1992; 62:153-63. [PMID: 1423808 DOI: 10.1016/0009-3084(92)90093-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The effect of several aminoglycoside (AG) antibiotics on aqueous multilamellar dispersions of mixtures of phosphatidylinositol (PI) and deuterated phosphatidylcholine (PC) has been studied by deuterium (2H) NMR. Isepamicin and amikacin gave rise to no significant changes in 2H-NMR lineshape relative to that of the lipid mixture without antibiotic. Both kanamycin A and B, which have a greater affinity for PI than the other two antibiotics examined in this study, induced temperature-dependent changes in 2H-NMR lineshapes and associated spectral moments. The results are consistent with an antibiotic-induced lateral phase separation giving rise to PC-enriched domains free of drug and PI-AG domains. These effects are correlated with the inhibitory potency of aminoglycosides towards PC degradation.
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Affiliation(s)
- A Schanck
- Laboratoire de Chimie-Physique et de Cristallographie and Research Center for Advanced Materials, Université Catholique de Louvain, Belgium
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1602
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Johnson DA, Valenzuela CF, Zidovetzki R. A deuterium NMR and steady-state fluorescence anisotropy study of the effects of cholesterol on the lipid membrane-disordering actions of ethanol. Biochem Pharmacol 1992; 44:769-74. [PMID: 1510724 DOI: 10.1016/0006-2952(92)90415-f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We examined the effects of cholesterol on the membrane-disordering action of ethanol by using deuterium nuclear magnetic resonance (2H-NMR) and fluorescence spectroscopy. Specifically, the effects of ethanol were measured on the 2H-NMR spectra of di(perdeuteropalmitoyl)phosphatidylcholine (DPPC-d62) and on the steady-state emission anisotropy of diphenylhexatriene (DPH) incorporated into hydrated egg phosphatidylcholine (eggPC)/cholesterol dispersions. Analysis of the 2H-NMR spectra of DPPC-d62 incorporated into eggPC liposomes showed that the addition of cholesterol up to 30 mol% enhanced the ability of ethanol to disorder methylene groups all along the phospholipid acyl chains. This effect was somewhat greater toward the terminal methyl groups. However, above 30 mol% cholesterol, the bilayer-disordering action of ethanol on both the upper and lower portions of the acyl chains decreased to an apparent constant change up to the highest cholesterol content examined (50 mol%). Analysis of the fluorescence anisotropy of DPH, on the other hand, suggested that cholesterol attenuated the ability of ethanol to disorder the bilayers, which is in agreement with a previous EPR study [Chin and Goldstein, Mol Pharmacol 19: 425-431, 1981]. Re-analysis of our previous fluorescence anisotropy results with DPH incorporated into dispersions of brain-lipid extracts as a percent change [Johnson et al., Mol Pharmacol 15: 739-746, 1979] indicated that the chemical composition of the lipid bilayers also affects the apparent ability of cholesterol to modulate the membrane-disordering action of ethanol, because the addition of cholesterol to brain-lipid extracts had no significant effect on the membrane-disordering action of ethanol. Given the greater likelihood that the 2H-NMR probes accurately monitor bulk phospholipid properties, some caution is required in the analysis of the membrane-disordering actions of drugs using EPR and fluorescence spectroscopy.
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Affiliation(s)
- D A Johnson
- Division of Biomedical Sciences, University of California, Riverside 92521-0121
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1603
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Abstract
The glycolipids of Acholeplasma laidlawii AIH089 membranes were identified and purified. The effect of monoglucosyldiacylglycerol (MGDG) and diglucosyldiacylglycerol (DGDG) on the thermotropic behavior of multilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG) has been investigated by high sensitivity differential scanning calorimetry. The main transition peaks were broadened, the enthalpies were decreased. DGDG caused the decrease in the transition temperatures of DPPC, DPPG liposomes by 3.08 degrees C, 4.18 degrees C, respectively. MGDG did not cause the alteration of the transition temperature of DPPC liposomes but caused the decrease of the transition temperatures of DPPG liposomes by 2.20 degrees C. ESR experiments indicate that MGDG decreased the rotational correlation time of DPPC and DPPG liposomes.
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Affiliation(s)
- J W Chen
- Institute of Biophysics, Academia Sinica, Beijing, China
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1604
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Yamazaki M, Kashiwagi N, Miyazu M, Asano T. Effect of oligomers of ethylene glycol on thermotropic phase transition of dipalmitoylphosphatidylcholine multilamellar vesicles. Biochim Biophys Acta 1992; 1109:43-7. [PMID: 1504079 DOI: 10.1016/0005-2736(92)90184-n] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The effect of oligomers of ethylene glycol (EG) on thermotropic phase transitions of dipalmitoylglycerophosphatidylcholine multilamellar vesicles (DPPC-MLV) were investigated. Diethylene glycol (di-EG) had a biphasic effect on transition temperature, reducing pre-transition temperature (Tp) at low concentrations but increasing main transition temperature (Tm) and extinguishing pre-transition at high concentration. Results of the X-ray diffraction method and the excimer method indicated that di-EG induced interdigitated gel phase (L beta 1 phase) in the DPPC membranes at high concentration. Phase diagram of temperature-di-EG concentration for DPPC-MLV was determined by use of X-ray diffraction and differential scanning calorimetry, which was similar to that of temperature-EG concentration. The minimum concentration of di-EG where L beta 1 phase was induced was 42%(w/v), which was larger than that of EG (30%(w/v)). On the other hand, in the presence of triethylene glycol (tri-EG), Tm and Tp increased with an increased in tri-EG concentration, as well as poly(ethylene glycol). These differences, between the effects of di-EG and those of tri-EG, might be due to the differences of their sizes.
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Affiliation(s)
- M Yamazaki
- Department of Physics, Faculty of Science, Shizuoka University, Japan
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1605
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Abstract
High-pressure 31P NMR was used for the first time to investigate the effects of pressure on the structure and dynamics of the phosphocholine headgroup in pure 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) multilamellar aqueous dispersions and in DPPC bilayers containing the positively charged form of the local anesthetic tetracaine (TTC). The 31P chemical shift anisotropies, delta sigma, and the 31P spin-lattice relaxation times, T1, were measured as a function of pressure from 1 bar to 5 kbar at 50 degrees C for both pure DPPC and DPPC/TTC bilayers. This pressure range permitted us to explore the rich phase behavior of DPPC from the liquid-crystalline (LC) phase through various gel phases such as gel I (P beta'), gel II (L beta'), gel III, gel IV, gel X, and the interdigitated, Gi, gel phase. For pure DPPC bilayers, pressure had an ordering effect on the phospholipid headgroup within the same phase and induced an interdigitated Gi gel phase which was formed between the gel I (P beta') and gel II (L beta') phases. The 31P spin-lattice relaxation time measurements showed that the main phase transition (LC to gel I) was accompanied by the transition between the fast and slow correlation time regimes. Axially symmetric 31P NMR lineshapes were observed at pressures up to approximately 3 kbar but changed to characteristic axially asymmetric rigid lattice lineshapes at higher pressures (3.1-5.1 kbar).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- X Peng
- Department of Chemistry, School of Chemical Sciences, University of Illinois, Urbana 61801
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1606
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Roth LG, Chen CH. Thermodynamic elucidation of solute-induced lipid interdigitation phase: lipid interactions with hydrophobic versus amphipathic species. Arch Biochem Biophys 1992; 296:207-13. [PMID: 1605632 DOI: 10.1016/0003-9861(92)90564-d] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Comparative thermodynamic studies on the interactions of aqueous dispersions of dipalmitoyl phosphatidylcholine (DPPC) bilayer vesicles with hydrophobic and amphipathic species were conducted to elucidate the nature of the solute-induced interdigitated lipid phase. Cyclohexanol, a strong hydrophobic species, lowers the temperature (tm) of the lipid main phase transition from the gel to the liquid-crystalline phase. Unlike ethanol (an amphipathic species), as reported previously, cyclohexanol does not exert a biphasic effect on tm (lowering tm at lower concentrations and raising tm at higher concentrations). At cyclohexanol greater than or equal to 15.4 mg/ml or 0.154 M, the thermogram of DPPC vesicles exhibits a small transition adjacent to the main phase transition but at a lower temperature. In contrast, ethanol does not promote such a small transition. Furthermore, the enthalpy (delta H) of the transition is increased in the presence of cyclohexanol. The sign of the enthalpy change (delta H-delta Ho) is positive and that of the free energy change (delta G-delta Go) is negative, a characteristic of solute-solute hydrophobic interaction. In contrast, DPPC bilayer vesicles exhibit both (delta H-delta Ho) and (delta G-delta Go) greater than 0 in the presence of ethanol in a concentration range where lipid vesicles exist in an interdigitated phase. To support the above distinct thermodynamic observations, fluorescence steady-state polarization (P) measurements were also performed. At the temperature below tm, the value of P decreases as cyclohexanol concentration increases, while a biphasic effect on P was found in the presence of ethanol. These findings support the postulation that the solute-induced interdigitated lipid phase requires the solute molecule to be amphipathic in nature.
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Affiliation(s)
- L G Roth
- Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany
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1607
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Abstract
Increasing methylation of the headgroup in DPPE results in an increase of minimum area per molecule in highly compressed monolayers at the air-water interface. The shape of solid domains, as observed by epifluorescence microscopy, also exhibits marked changes upon increasing headgroup methylation. Branching domains are observed in DPPE and DP(Me)PE, whereas U-shaped or round domains are observed in DP(Me)2PE and DPPC under our experimental conditions. The domain shape is determined more by the headgroup methylatin than by the corresponding shift in critical temperatures, as shown by the study of PCs of different acyl chain moieties. In mixed lipid monolayers, PC (phosphatidylcholine) and PE (phosphatidylethanolamine) do not mix ideally, as indicated by the non-linear variation of the average area per molecule with composition, and by distinct domain shapes in LE/LC (liquid expanded/liquid condensed) coexisting phases representing PE-enriched or PC-enriched domains in those mixed monolayers.
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Affiliation(s)
- H Yu
- Department of Biophysics, Roswell Park Cancer Institute, Buffalo, NY 14263
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1608
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Pérez-Gil J, Nag K, Taneva S, Keough KM. Pulmonary surfactant protein SP-C causes packing rearrangements of dipalmitoylphosphatidylcholine in spread monolayers. Biophys J 1992; 63:197-204. [PMID: 1420867 PMCID: PMC1262137 DOI: 10.1016/s0006-3495(92)81582-5] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The hydrophobic pulmonary surfactant protein SP-C has been isolated from porcine lung surfactant, and it has been incorporated into monolayers of dipalmitoylphosphatidylcholine (DPPC). The monolayers, which contained 1 mol% of a fluorescently-labeled phosphatidylcholine, were observed under various states of compression in an epifluorescence surface balance. SP-C altered the packing arrangements of DPPC in the monolayer, causing the production of many more, smaller condensed lipid domains in its presence than in its absence.
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Affiliation(s)
- J Pérez-Gil
- Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada
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1609
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Abstract
Mastoparan-X, a tetradecapeptide from wasp venom, has been proposed to cause secretion from various kinds of cells by the direct activation of GTP-binding regulatory proteins (G proteins) that couple to phospholipase C. The mechanism of the activation has been shown to be very similar to that of G-protein-coupled receptors in vitro, and the interaction with membranes seems to be very important for the activation of G proteins that are membrane-bound [Higashijima, T., Uzu, S., Nakajima, T., & Ross, E. M. (1988) J. Biol. Chem. 263, 6491-6494]. We report here the precise vesicle-bound conformation of mastoparan-X in the presence of perdeuterated phospholipid vesicles, determined by two-dimensional 1H-NMR analyses of transferred nuclear Overhauser effects, combined with distance geometry and molecular dynamics calculations. Of 14 amino acid residues, the C-terminal 12 residues take an alpha-helical conformation upon binding to the phospholipid bilayer. The overall structure of the alpha-helix is amphiphilic, with three lysine side chains located on one side and with hydrophobic side chains on the other side. This conformation of mastoparan-X was maintained both in the gel and in the liquid-crystalline phases of the membranes. The conformation described herein will provide a useful basis for understanding conformation-activity relationships of mastoparan analogs as activators of G proteins. These studies will help to design novel potent analogs for the regulation of G proteins and to analyze receptor-G-protein interactions.
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Affiliation(s)
- K Wakamatsu
- Faculty of Engineering, Gunma University, Japan
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1610
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Yu SH, Possmayer F. Effect of pulmonary surfactant protein B (SP-B) and calcium on phospholipid adsorption and squeeze-out of phosphatidylglycerol from binary phospholipid monolayers containing dipalmitoylphosphatidylcholine. Biochim Biophys Acta 1992; 1126:26-34. [PMID: 1606172 DOI: 10.1016/0005-2760(92)90212-e] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The pulsating bubble technique was used to study the surface activity of binary phospholipid mixtures containing dipalmitoyl-phosphatidylcholine (DPPC) and an unsaturated acidic phospholipid such as egg phosphatidylglycerol (egg PG), 1-palmitoyl-2-oleoyl-PG (POPG) or egg phosphatidic acid (egg PA) in the presence of surfactant-associated protein B (SP-B) and calcium. The relative surface activities were DPPC/egg PG/SP-B (7:3:1%) greater than DPPC/POPG/SP-B (7:3:1%) greater than DPPC/egg PA/SP-B (7:3:1%). The Wilhelmy surface plate technique was utilized to investigate the interaction between pure SP-B in the bulk phase (0.9% NaCl/1.5 mM CaCl2) and preformed DPPC or phosphatidylglycerol (PG) monolayers. Although SP-B injected into the bulk phase reduces the surface tension of a clean surface, no evidence was obtained for the insertion of SP-B into surface monolayers at equilibrium surface tension. Surface radioactivity measurements and the Wilhelmy surface plate technique were also used to study the potential interactions between liposomes of DPPC/POPG (7:3) with or without SP-B and surface monolayers of [14C]DPPC or [14C]POPG. No exchange of phosphatidylcholine (PC) or PG was found between the monolayer and liposomes. We also compared the adsorption of pure POPG or 1-palmitoyl-2-oleoyl- phosphatidylcholine (POPC) and binary mixed liposomes with DPPC in the presence or absence of SP-B and calcium. DPPC/POPG/SP-B (7:3:1%) was found to be more surface active than pure POPG plus 1% SP-B in the presence of calcium. Injection of SP-B into the bulk phase promoted the adsorption of DPPC/POPG liposomes to a greater extent than POPG liposomes. The enhanced adsorption was dependent on the presence of calcium. In contrast to PG, DPPC/POPC/SP-B (7:3:1%) was less surface active than pure POPC plus 1% SP-B either in the presence or absence of calcium. Our findings suggested that the molecular composition and organization of mixed monolayers play an important role in the surface activity of the surfactant.
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Affiliation(s)
- S H Yu
- Department of Obstetrics and Gynaecology, University of Western Ontario, London, Canada
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1611
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Fujisawa S, Komoda Y, Kadoma Y. Hemolytic activity of a dental adhesive monomer (N-methacryloyloxy-5-aminosalicylic acid, MASA) and its interaction with phospholipid liposomes as studied by NMR and DSC. Dent Mater J 1992; 11:17-25. [PMID: 1395483 DOI: 10.4012/dmj.11.17] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
N-methacryloyloxy-5-aminosalicylic acid (MASA) has recently been used as an adhesive primer in restorative resin systems. To monitor the biological activity of MASA, we studied changes in NMR-chemical shifts (delta H) and the differential scanning calorimetry (DSC) phase transition temperature (Tm) of dipalmitoylphosphatidylcholine (DPPC)/MASA liposomes with or without the presence of albumin and collagen. The delta H and the Tm did not alter significantly and the interaction of MASA with DPPC was found to be small. Hemolytic activity of MASA was markedly smaller than that of the phosphate monomer (MDP) in bonding agents widely used. These findings suggest that using a MASA primer in resin systems has an acceptable biocompatibility for dentin-pulp, involving its adsorption and adhesion to hard tooth tissues.
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1612
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Kaminoh Y, Nishimura S, Kamaya H, Ueda I. Alcohol interaction with high entropy states of macromolecules: critical temperature hypothesis for anesthesia cutoff. Biochim Biophys Acta 1992; 1106:335-43. [PMID: 1596513 DOI: 10.1016/0005-2736(92)90014-d] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Nerve excitation generates heat and decreases the entropy (review by Ritchie and Keynes (1985) Q. Rev. Biophys. 18, 451-476). The data suggest the existence of at least two thermodynamically identifiable states: resting and excited, with a thermotropic transition between the two. We envision that nerve excitation is a transition between the two states of the excitation machinery consisting of proteins and lipids, rather than the sodium channel protein alone. Presumably, both proteins and lipids change their conformation at excitation. We proposed (Kaminoh et al. (1991) Ann. N.Y. Acad. Sci. 625, 315-317) that anesthesia occurs when compounds have a higher affinity to the resting state than to the excited state of excitable membranes, and that there is a critical temperature above which the affinity to the excited state becomes greater than to the resting state. When the temperature exceeds this critical level, compounds lose their anesthetic potency. We used thermotropic phase-transition of macromolecules as a model for the excitation process. Anesthetic alcohols decreased the main transition temperature of dipalmitoylphosphatidylcholine (DPPC) membranes and also the temperature of the alpha-helix to beta-sheet transition of poly(L-lysine). The affinity of alcohols to the high- and low-temperature states of the DPPC membranes were separately estimated. The difference in the affinity of n-alcohols to the liquid (high-temperature) and solid (low-temperature) states correlated with their anesthetic potency. It is not the total number of bound anesthetic molecules that determines the anesthesia, rather, the difference in the affinity between the higher and lower entropy states determines the effects. The critical temperatures of the long-chain alcohols were found to be lower than those of the short-chain alcohols. Cutoff occurs when the critical temperature of long-chain alcohols is below the physiological temperature, such that the anesthetic potency is not manifested in the experimental temperature range.
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Affiliation(s)
- Y Kaminoh
- Department of Anesthesia, University of Utah School of Medicine, Salt Lake City
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1613
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Ortiz A, Aranda FJ, Gómez-Fernández JC. Interaction of retinol and retinoic acid with phospholipid membranes. A differential scanning calorimetry study. Biochim Biophys Acta 1992; 1106:282-90. [PMID: 1596508 DOI: 10.1016/0005-2736(92)90007-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The influence of retinol and retinoic acid, two retinoids of major interest, on the main gel to liquid-crystalline phase transition of different phospholipid membranes has been studied by means of differential scanning calorimetry. Both compounds exerted perturbing effects on the phase transition of membranes composed of dipalmitoylphosphatidylcholine or dipalmitoylphosphatidylethanolamine. At concentrations up to 42.5 mol% of retinoid in the membrane, the delta H was not much affected with respect to the pure phospholipid, indicating a rather slight interaction. As the concentration of retinol was increased the Tc transition temperature decreased. A fluid-phase immiscibility was observed for the system DPPC/retinol at concentrations between 0 and 33 mol%. Almost ideal phase diagrams were obtained for the mixture DPPE/retinol. At concentrations of 33 mol% and higher retinol was able to induce phase separations in DPPC membranes, but not in DPPE. The effect of retinoic acid was much weaker, the Tc and delta H remaining almost unaltered and equal to that of the pure phospholipid up to concentrations of 30 mol%, at neutral pH. Retinoic acid exerted a pH-dependent effect. As the pH decreased, and therefore increased the extent of protonation of retinoic acid, the pertubation of the membrane induced by this compound was less. A strong effect, both on Tc and delta H, was observed at pH 10, where the retinoic acid moiety will be mainly unprotonated and the negative charge will generate repulsive forces thus destabilizing the membrane. The mixture DPPC/retinoic acid presents a region of fluid-phase immiscibility. At low pH, when the retinoic acid moiety was fully protonated, this fluid-immiscibility region extended from 0 to 36 mol% of retinoic acid, but its size decreased with increasing pH, and at pH 10 it was only found from 0 to 3 mol%. These results are discussed in terms of the possible retinoid/phospholipid interactions and the disposition of the retinoid moiety in the bilayer.
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Affiliation(s)
- A Ortiz
- Departamento de Bioquímica y Biología Molecular A, Facultad de Veterinaria, Universidad de Murcia, Spain
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1614
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Tadolini B, Motta P, Sechi AM. Phospholipid polar heads affect the generation of oxygen active species by Fe2+ autoxidation. Biochem Int 1992; 26:987-94. [PMID: 1632807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The possibility that phospholipid polar heads may influence Fe2+ reaction with molecular oxygen and, thus, the generation of oxygen active species was investigated. Dipalmitoyl phosphatidylcholine (DPPC) and DPPC/dipalmitoyl phosphatidic acid (DPPA) were utilized as model liposomes. Fe2+ oxidation, oxygen consumption, nitro blue tetrazolium reduction and 2-deoxyribose degradation were the parameters evaluated. Comparison of the results obtained clearly shows that the two types of polar heads differently affect iron chemistry. DPPC liposomes are ineffective. By contrast, Fe2+ oxidation by oxygen occurs in the presence of DPPC/DPPA liposomes. During this reaction, species able to reduce nitro blue tetrazolium and to degrade 2-deoxyribose are generated. The results obtained indicate that the polar heads of phospholipids, by influencing Fe2+ autoxidation, generate dangerous oxygen species which may exert an active role in the oxidation of the associated hydrophobic components of the phospholipids.
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Affiliation(s)
- B Tadolini
- Dipartimento di Biochimica, Università di Bologna, Italy
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1615
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Freisleben HJ, Blöcher D, Ring K. Calorimetry of tetraether lipids from Thermoplasma acidophilum: incorporation of alamethicin, melittin, valinomycin, and nonactin. Arch Biochem Biophys 1992; 294:418-26. [PMID: 1567197 DOI: 10.1016/0003-9861(92)90706-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The development and application of model membrane systems on the basis of tetraether lipids from Thermoplasma acidophilum has been proposed. In this respect incorporation of membrane proteins and ionophores is indispensable and is demonstrated in the case of alamethicin, melittin, nonactin, and valinomycin by calorimetry. Dipalmitoylphosphatidylcholine (DPPC) and dihexadecylmaltosylglycerol (DHMG) were chosen for comparison. Melittin and alamethicin prove to broaden the lipid phase transition and to reduce the melting temperature Tm and enthalpy change (delta H) of the main phospholipid from T. acidophilum (MPL) and DPPC. The decrease in Tm, however, is more pronounced in DPPC than in MPL. Valinomycin shows only a marginal effect on the temperature and width of the transition; delta H is reduced in MPL and remains constant in DPPC and DHMG. With nonactin the phase transition of DPPC is quenched, and delta H and the half-height width are increased. DHMG is affected to a lesser extent and MPL only marginally. The four ionophores exhibit different modulation of the phase transition behavior of the various lipids as expected from their varying molecular structures. Thus, the integral membrane protein alamethicin, the peripheral protein melittin, valinomycin, and nonactin interact primarily with lipid head groups and are readily incorporated into the tetraether lipid structures.
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Affiliation(s)
- H J Freisleben
- Gustav-Embden-Zentrum der Biologischen Chemie, Johann Wolfgang Goethe-Universität, Frankfurt/Main, Germany
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1616
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Testoff MA, Rudolph AS. Modification of dry 1,2-dipalmitoylphosphatidylcholine phase behavior with synthetic membrane-bound stabilizing carbohydrates. Bioconjug Chem 1992; 3:203-11. [PMID: 1520723 DOI: 10.1021/bc00015a001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Carbohydrates, particularly disaccharides, have been shown to accumulate in organisms as protective solutes during periods of stress such as freezing and desiccation. Cholesterol and lipid derivatives containing the protective carbohydrates galactose or maltose, O-[11-(1-beta-D-galactosyloxy)-3,6,9-trioxaundecanyl]ol (TEC-GAL), O-[11-(1-beta-D-maltosyloxy)-3,6,9-trioxaundecanyl]ol (TEC-MAL), and 14-(galactosyloxy)-N,N-dimethyl-O-(dipalmitoylphosphatidyl)- 6,9,12-trioxa-3- azoniatetradecanol (DP-GAL), have been synthesized to investigate the interaction of a protective carbohydrate moiety tethered to the 1,2-dipalmitoylphosphatidylcholine (DPPC) bilayer surface. Toward this goal, we have investigated the calorimetric and infrared spectroscopic behavior of mixtures of DPPC codried with these glycolipids. The synthetic glycolipids are shown to decrease significantly the main transition temperature (max Cp) of dry DPPC with a concomitant reduction in the cooperativity of the transition, as evidenced by a decrease in the enthalpy with increasing glycolipid. The decrease in transition temperature is shown to be related to chain melting monitored by the CH2 symmetric stretch frequency through the transition using FTIR. We also present evidence that the glycolipids interact with the interfacial region of DPPC, as shown by the decrease in the phosphate symmetric stretch intensity with increasing concentration of glycolipid. These observed effects are similar to the action of bulk protective sugars with DPPC; however, the concentration of glycolipid and the associated carbohydrate concentration needed to effect the observed changes are reduced compared to the quantity of bulk carbohydrate previously shown to give similar results with DPPC.
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Affiliation(s)
- M A Testoff
- Center for Biomolecular Science and Engineering, Naval Research Laboratory, Washington, D.C. 20375-5000
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1617
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Pérez-Gil J, Tucker J, Simatos G, Keough KM. Interfacial adsorption of simple lipid mixtures combined with hydrophobic surfactant protein from pig lung. Biochem Cell Biol 1992; 70:332-8. [PMID: 1497860 DOI: 10.1139/o92-051] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Hydrophobic pulmonary surfactant protein enriched in SP-C has been mixed in amounts up to 10% by weight with various phospholipids. The lipids used were dipalmitoyl phosphatidylcholine (DPPC), or DPPC plus unsaturated phosphatidylglycerol (PG), or phosphatidylinositol (PI) in molar ratios of 9:1 and 7:3. The protein enhanced the rate and extent of adsorption of each lipid preparation into the air-water interface, and its respreading after compression on a surface balance. Maximum surface pressures attained on compression of monolayers of mixtures of lipids were slightly higher in the presence of protein. The effects on rate and extent of adsorption were proportional to the amount of protein present. Mixtures containing 30 mol% PG or PI adsorbed more readily into the interface than those containing 10% acidic lipid or DPPC alone. Mixtures containing 30% PI were slightly more rapidly adsorbed than those containing 30% PG. The results suggest that mixtures of DPPC with either acidic lipid in the presence of surfactant protein could be effective in artificial surfactants.
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Affiliation(s)
- J Pérez-Gil
- Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada
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1618
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Affiliation(s)
- J Villalain
- Department of Biochemistry, Faculty of Veterinary Sciences, University of Murcia, Spain
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1619
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Abstract
The biophysical behaviour of the Meibomian gland secretion was tested under in vitro conditions. Thereby, simultaneous recording of surface pressure and surface potential was performed. The Meibomian lipid layer was compared with other surface-active components like polyvinylalcohol and polyvinylpyrrolidone. On the other hand, Eledoisin was tested as an example for a surface-inactive substance. An attempt was made to describe the biophysical interaction between a given artificial tear substitute and the Meibomian lipid layer. With respect to the surface potential Dipalmitoyl-phosphatidyl-choline was established as an analogue for Meibomian gland secretion. Fluorescence measurements in the presence of a cyanine dye (1 N,N'dioctadecyloxacarbocyanine) were used as a method to localize the site of the characteristic potential change. From the fluorescence spectra under compression we conclude that the molecular change takes place at the lipid-subphase interface of the Meibomian lipid layer.
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1620
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Gawrisch K, Ruston D, Zimmerberg J, Parsegian VA, Rand RP, Fuller N. Membrane dipole potentials, hydration forces, and the ordering of water at membrane surfaces. Biophys J 1992; 61:1213-23. [PMID: 1600081 PMCID: PMC1260386 DOI: 10.1016/s0006-3495(92)81931-8] [Citation(s) in RCA: 359] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We have compared hydration forces, electrical dipole potentials, and structural parameters of dispersions of dipalmitoylphosphatidylcholine (DPPC) and dihexadecylphosphatidylcholine (DHPC) to evaluate the influence of fatty acid carbonyl groups on phospholipid bilayers. NMR and x-ray investigations performed over a wide range of water concentrations in the samples show, that in the liquid crystalline lamellar phase, the presence of carbonyl groups is not essential for lipid structure and hydration. Within experimental error, the two lipids have identical repulsive hydration forces between their bilayers. The higher transport rate of the negatively charged tetraphenylboron over the positively charged tetraphenylarsonium indicates that the dipole potential is positive inside the membranes of both lipids. However, the lack of fatty acid carbonyl groups in the ether lipid DHPC decreased the potential by (118 +/- 15) mV. By considering the sign of the potential and the orientation of carbonyl groups and headgroups, we conclude that the first layer of water molecules at the lipid water interface makes a major contribution to the dipole potential.
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Affiliation(s)
- K Gawrisch
- DCRT and NIDDK, National Institutes of Health, Bethesda, Maryland 20892
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1621
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Reichert A, Ringsdorf H, Wagenknecht A. Spontaneous domain formation of phospholipase A2 at interfaces: fluorescence microscopy of the interaction of phospholipase A2 with mixed monolayers of lecithin, lysolecithin and fatty acid. Biochim Biophys Acta 1992; 1106:178-88. [PMID: 1581331 DOI: 10.1016/0005-2736(92)90237-g] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Fluorescence microscopy has recently been proven to be an ideal tool to investigate the specific interaction of phospholipase A2 with oriented substrate monolayers. Using a dual labeling technique, it could be shown that phospholipase A2 can specifically attack and hydrolyze solid analogous L-alpha-DPPC domains. After a critical extent of monolayer hydrolysis the enzyme itself starts to aggregate forming regular shaped protein domains (Grainger et al. (1990) Biochim. Biophys. Acta 1023, 365-379). In order to confirm that the existence of hydrolysis products in the monolayer is necessary for the observed aggregation of phospholipase A2, mixed monolayers of D- and L-alpha-DPPC, L-alpha-lysoPPC and palmitic acid in different ratios were examined. The phase behavior and the interaction of these films with phospholipase A2 were directly visualized with an epifluorescence microscope. Above a certain critical concentration of lysolecithin and palmitic acid in the monolayer, compression of these mixed films leads to phase separation and formation of mixed domains of unknown composition. Their high negative charge density is evidenced by preferential binding of a cationic dye to these phase-separated areas. Introduction of fluorescence-labeled phospholipase A2 underneath these mixed domains results in rapid binding of the protein to the domains without visible hydrolytic activity, regardless of whether the L-form or the D-form of the DPPC were used. In binary mixtures, only those with DPPC/palmitic acid show formation of phase-separated areas which can be specifically targeted by phospholipase A2 leading to a rapid formation (within 2 min) of protein domains. Experiments with pyrenedecanoic acid containing monolayers give the first direct evidence that acid is located above the enzyme domains. These results show that a locally high negative charge density of the phase-separated domains is one of the prerequisites for the binding of phospholipase A2. In addition, however, small amounts of D- or L-alpha-DPPC headgroups within the domains of the monolayer seem to be necessary for recognition followed by fast binding of the protein to the domains. This is confirmed by experiments with mixed monolayers of diacetylene carboxylic acid and D-alpha-DPPC. The acid--immiscible with lecithin--forms well defined pure acid domains in the monolayer. While the cationic dye can be docked rapidly to these phase separated areas, no preferential enzyme binding and thus no protein domain formation below these acid domains can be induced.
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Affiliation(s)
- A Reichert
- Institut für Organische Chemie, Universität Mainz, Germany
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1622
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Martí A, Armengol X, Estelrich J, Hernández-Borrell J. Encapsulation of doxorubicin in neutral liposomes by passive methods: evidence of drug-lipid interaction at neutral pH. J Microencapsul 1992; 9:191-200. [PMID: 1593403 DOI: 10.3109/02652049109021236] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Doxorubicin, an antineoplastic agent, was encapsulated in liposomes of dipalmitoylphosphatidylcholine with or without cholesterol, by the extrusion procedure. Doxorubicin was added to the lipid before drying, or was present in the rehydration buffer, and the influence of the method of encapsulation on size and polydispersity was determined by photon correlation spectroscopy. Results showed an important interaction between doxorubicin and liposomes, although cholesterol-containing vesicles were those that underwent the strongest insertion of the drug. One important parameter, which determined the extension of such interaction, was the curvature of the vesicle bilayer. So, liposomes extruded through a 50 nm membrane filter suffered the highest relative size variation in comparison with empty liposomes. Doxorubicin also produced an increase in polydispersity of vesicle population; therefore its presence resulted in some fusion and/or aggregation processes. The stability of liposomes was dependent on lipid content, on the method of drug trapping and on the presence or absence of such drug. Encapsulation efficiency seemed to be inversely related to liposome stability. Maximal values, which never exceed 0.015 +/- 0.005 mumol of drug per mumol of lipid, were obtained when the drug was dried together with the lipids.
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Affiliation(s)
- A Martí
- Unidad de Físicoquimica, Facultad de Farmàcia, Barcelona, Catalonia, Spain
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1623
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Fajer P, Watts A, Marsh D. Saturation transfer, continuous wave saturation, and saturation recovery electron spin resonance studies of chain-spin labeled phosphatidylcholines in the low temperature phases of dipalmitoyl phosphatidylcholine bilayers. Effects of rotational dynamics and spin-spin interactions. Biophys J 1992; 61:879-91. [PMID: 1316181 PMCID: PMC1260347 DOI: 10.1016/s0006-3495(92)81895-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The saturation transfer electron spin resonance (STESR) spectra of 10 different positional isomers of phosphatidylcholine spin-labeled in the sn-2 chain have been investigated in the low temperature phases of dipalmitoyl phosphatidylcholine (DPPC) bilayers. The results of continuous wave saturation and of saturation recovery measurements on the conventional ESR spectra were used to define the saturation properties necessary for interpreting the STESR results in terms of the chain dynamics. Spin labels with the nitroxide group located in the center of the chain tended to segregate preferentially from the DPPC host lipids in the more ordered phases, causing spin-spin interactions which produced spectral broadening and had a very pronounced effect on the saturation characteristics of the labels. This was accompanied by a large decrease in the STESR spectral intensities and diagnostic line height ratios relative to those of spin labels that exhibited a higher degree of saturation at the same microwave power. The temperature dependence of the STESR spectra of the different spin label isomers revealed a sharp increase in the rate of rotation about the long axis of the lipid chains at approximately 25 degrees C, correlating with the pretransition of gel phase DPPC bilayers, and a progressive increase in the segmental motion towards the terminal methyl end of the chains in all phases. Prolonged incubation at low temperatures led to an increase in the diagnostic STESR line height ratios in all regions of the spectrum, reflecting the decrease in chain mobility accompanying formation of the subgel phase. Continuous recording of the central diagnostic peak height of the STESR spectra while scanning the temperature revealed a discontinuity at approximately 14-17 degrees C, corresponding to the DPPC subtransition which occurred only on the initial upward temperature scan, in addition to the discontinuity at 29-31 degrees C corresponding to the pretransition which displayed hysteresis on the downward temperature scan.
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Affiliation(s)
- P Fajer
- Max-Planck-Institut für biophysikalische Chemie, Abteilung Spektroskopie, Göttingen, Germany
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1624
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Aoyagi H, Waki K, Kato T, Lee S, Yamasaki H, Furuya S. Interaction of amino acid-substituted partial extension peptides of adrenodoxin precursor with artificial membranes and isolated mitochondria. Pept Res 1992; 5:91-6. [PMID: 1581642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The N-terminal fragment Met-Ala-Ala-Arg-Leu-Leu-Arg-Val-Ala-Ser-Ala-Ala-Leu-Gly (PA1-14) of the adrenodoxin precursor was previously found to inhibit the import of the precursor into mitochondria. In order to obtain further information on the structure-function relationship, five analogs of PA1-14 ([Leu1]PA1-14 (1), [Leu1,Ala10]PA1-14 (2), [Leu1,Ser4]PA1-14 (3), [Leu1,Arg11]PA1-14 (4) and [Leu1,Ser7,Arg10]PA1-14 (5) were synthesized. The CD study showed that PA1-14 and all analogs were random in an aqueous solution and formed an alpha-helical structure in the solution containing acidic liposomes. Peptides 1 and 2 were found to cause dye leakage from lipid vesicles more strongly than other analogs and PA1-14. All analogs completely inhibited the import of the precursor into mitochondria at a concentration of 30 microM. However, 1 and 2 destroyed the mitochondrial membrane potential. These results indicate that an increase in hydrophobicity by replacement of the Met and Ser residues by Leu and Ala, respectively, participates in the perturbation of the membranes. Furthermore, the requirement for the number and position of the Arg residue was found to be not very strict, although its presence in the extension peptide is essential for the precursor to import into mitochondria.
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Affiliation(s)
- H Aoyagi
- Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan
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1625
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Zhang F, Rowe ES. Titration calorimetric and differential scanning calorimetric studies of the interactions of n-butanol with several phases of dipalmitoylphosphatidylcholine. Biochemistry 1992; 31:2005-11. [PMID: 1536843 DOI: 10.1021/bi00122a016] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The interactions of n-butanol with dipalmitoylphosphatidylcholine (DPPC) were studied using titration calorimetry and differential scanning calorimetry (DSC). DSC results indicated that n-butanol induces the interdigitated phase in DPPC above 10 mg/mL butanol. A new application of titration calorimetry for measuring partition coefficients of nonsaturating solutes into lipids was developed. The partition coefficients and the heat of binding of n-butanol into DPPC were measured for the L beta', P beta', L alpha, and L beta I phases of DPPC. The partition coefficients were temperature dependent and ranged from 70 to 110 for the L beta I phase, from 170 to 183 for the L alpha phase, and similar to that for the L beta I phase in the P beta' phase. The binding to the L beta' phase could not be detected, giving an upper limit for this partition coefficient of 23. The enthalpies for binding to the L beta I and L alpha phases were 1.0 and 1.5 kcal/mol, respectively. The van't Hoff enthalpy was in good agreement with the calorimetric enthalpy for the partitioning into the L alpha phase; however, it was greater than the calorimetric enthalpy for the L beta I phase, suggesting that the interaction of n-butanol with this phase is cooperative in some way.
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Affiliation(s)
- F Zhang
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City 66103
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1626
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Abstract
The fluorescence emission spectrum of N epsilon-dansyl-L-Lys undergoes a marked blue shift when incorporated from aqueous solution into phospholipid bilayers. This shift is greater for membranes composed of dipalmitoleoylphosphatidylcholine than for membranes of dipalmitoleoylphosphatidylethanolamine. With the latter but not the former lipid, the fluorescence emission from N epsilon-dansyl-L-Lys is markedly temperature-dependent. The marked temperature dependence of N epsilon-dansyl-L-Lys fluorescence in bilayers of dipalmitoleoylphosphatidylethanolamine is greatest as the sample is heated close to the bilayer to hexagonal phase transition temperature. The fluorescence emission properties of another probe of membrane surface hydrophobicity, Laurdan, also exhibit marked changes at temperatures just below the bilayer to hexagonal phase transition temperature. At these temperatures, the generalized polarization begins to increase rather than decrease with temperature, and the emission intensity decreases markedly. Such effects are not observed over the same temperature range with phosphatidylcholine. Thus, both dansyl-L-lysine and Laurdan provide probes to measure changes in the physical properties of membrane bilayers which occur when these bilayers are heated close to the temperature required for transition to the hexagonal phase.
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Affiliation(s)
- R M Epand
- Department of Biochemistry, McMaster University Health Sciences Centre, Hamilton, Ontario, Canada
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1627
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Abstract
The membrane M-protein of Newcastle disease virus is localized directly beneath the lipid bilayer. Although this protein is the major constituent of the virus, its structural relationship to the lipid or to the other viral component hemagglutinin-neuraminidase, the so called HN-glycoprotein, is still unknown. The effects of either M-protein alone or both M-protein and HN-glycoprotein on the lipid assemblies in reconstituted liposomes were determined by differential polarized phase fluorometry, steady-state fluorescence anisotropy and emission lifetime measurements. It is demonstrated that the degree of rotation of fluorophores in reconstituted liposomes is restricted by the molecular packing of lipids in the bilayer and this in turn can be correlated with the structural order of the lipids in the membrane. The experimental results show that the structural order parameters calculated from the fluorescence measurements are strongly influenced by the presence of both M-protein and HN-glycoprotein in the lipid assemblies.
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Affiliation(s)
- V Z Neitchev
- Central Laboratory of Biophysics, Bulgarian Academy of Sciences, Sofia
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1628
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Abstract
The interactions of a series of saturated diacylglycerols (DAGs) with fatty acid side chain lengths of 6-14 carbons with multilamellar phospholipid bilayers consisting either of dipalmitoylphosphatidylcholine (DPPC) or of a mixture of DPPC and bovine liver phosphatidylcholine (BL-PC) extracts were studied by 2H NMR spectrometry. We found that the perturbation induced by the DAGs into the bilayer structure strongly depends on the length of the DAG fatty acid side chain. Shorter chain 1,2-sn-dihexanoylglycerol and, to a larger degree, 1,2-sn-dioctanoylglycerol (diC8) induce transverse perturbation of the bilayer structure: the order parameters of the phospholipid side chains are increased by the intercalating DAG molecules in the region adjacent to the phospholipid headgroups and decreased toward the terminal methyls, corresponding to the bilayer interior. The longer chain DAGs (C greater than or equal to 12) studied in this and previous [De Boeck & Zidovetzki (1989) Biochemistry 28, 7439] work induce lateral phase separation of the lipids into DAG-enriched gellike domains and relatively DAG-free regions in the liquid-crystalline phase. Each of the DAGs studied induces a decrease in the area per phospholipid molecule, and a corresponding increase in the lateral surface pressure of the bilayers.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H De Boeck
- Department of Biology, University of California, Riverside 92521
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1629
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Abstract
In the first part of the present work the interaction of glycophorin with dimyristoylphosphatidylcholine (DMPC) is studied by freeze fracture electron microscopy, densitometry, calorimetry, and 90 degree static light scattering. An exothermic lipid/protein interaction energy of WP = 190 kJ.mol-1 was found by application of the well known Van Laar relation for the displacement of the freezing point and the Gibbs-Duhem relationship. Secondly, the effects of Ca2+ on the lipid/protein interaction were studied. Following Ca2+ addition a remarkable decoupling of the interaction of the glycophorin head group with the bilayer surface was revealed by densitometry and gold-labeling electron microscopy. It is estimated that about 80% of lipid once disturbed by the adsorption of glycophorin head groups is decoupled after addition of Ca2+. Thirdly, the selective interaction of glycophorin with binary lipid mixtures was studied, including the mixtures of DMPC with dimyristoylphosphatidylserine (DMPS) and dilauroylphosphatidylcholine (DLPC), and the mixture of dipalmitoylphosphatidylcholine (DPPC) with DLPC.
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Affiliation(s)
- S F Sui
- Department of Biological Science & Biotechnology, Tsinghua University, Beijing, P.R. China
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1630
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Affiliation(s)
- B A Wallace
- Department of Crystallography, Birkbeck College, University of London, U.K
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1631
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Gawrisch K, Janz S. The uptake of pristane (2,6,10,14-tetramethylpentadecane) into phospholipid bilayers as assessed by NMR, DSC, and tritium labeling methods. Biochim Biophys Acta 1991; 1070:409-18. [PMID: 1764453 DOI: 10.1016/0005-2736(91)90081-i] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Unilamellar dioleoylphosphatidylcholine (DOPC) liposomes (250 microM) incorporated 2 mol% of [3H]pristane at 37 degrees C after addition of 50 microM pristane solubilized with beta-cyclodextrin. Conventional solubilization in dimethyl sulphoxide resulted in much lower uptake. Premixing of perdeuterated pristane with DOPC and dipalmitoylphosphatidylcholine (DPPC) prior to the formation of multilamellar liposomes resulted in homogeneous incorporation of up to 5 mol% pristane at 22 degrees C and 50 degrees C, respectively, as observed by 2H-NMR. Lipid order parameters measured by 31P and 2H-NMR remained unchanged after pristane uptake. Pristane induced the transformation of part of the dioleoylphosphatidylethanolamine (DOPE)/DOPC (3:1, mol/mol) liquid crystalline lamellar phase into an inverse hexagonal phase. 5 mol% pristane in DPPC bilayers decreased the midpoint of the main phase transition temperature of DPPC from 41.5 degrees C to 40.9 degrees C. Upon cooling in the temperature range from 41 degrees C to 36 degrees C, pristane was either displaced from the DPPC bilayer or the mode of incorporation changed. These results may aid in defining the mechanisms whereby pristane, an isoprenoid C19-isoalkane, induces plasmacytomagenesis in mice.
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Affiliation(s)
- K Gawrisch
- Division of Computer Research and Technology, National Institutes of Health, Bethesda, MD 20892
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1632
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Matsuzaki K, Shioyama T, Okamura E, Umemura J, Takenaka T, Takaishi Y, Fujita T, Miyajima K. A comparative study on interactions of alpha-aminoisobutyric acid containing antibiotic peptides, trichopolyn I and hypelcin A with phosphatidylcholine bilayers. Biochim Biophys Acta 1991; 1070:419-28. [PMID: 1764454 DOI: 10.1016/0005-2736(91)90082-j] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Interactions of alpha-aminoisobutyric acid containing antibiotic peptides, trichopolyn I and hypelcin A with phosphatidylcholine bilayers were investigated to obtain some basic information on their bioactive mechanisms. Trichopolyn I as well as hypelcin A induced the leakage of a fluorescent dye, calcein, entrapped in sonicated egg yolk L-alpha-phosphatidylcholine vesicles. A quantitative analysis revealed that both the binding affinity and the 'membrane-perturbing activity' of trichopolyn I to the vesicles are about one-third of those of hypelcin A. The conformations and the orientations of the peptide and lipid molecules in the membranes were studied using polarized Fourier transform infrared-attenuated total reflection spectroscopy, circular dichroism, and differential scanning calorimetry. In phosphatidylcholine bilayers, both peptides mainly conformed to helical structures irrespective of the membrane physical state (gel or liquid-crystalline). The helix axes, penetrating the hydrophobic region of the bilayers, were oriented neither parallel nor perpendicular to the membrane normal. The disruption in the lipid packing induced by the peptide insertion seems to be responsible for the leakage by these peptides.
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Affiliation(s)
- K Matsuzaki
- Faculty of Pharmaceutical Sciences, Kyoto University, Japan
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1633
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Abstract
A vesicle simulation and computer analysis program, VESICA, is described which employs spherical projections of triangularly tessellated icosahedra to produce molecular graphics models of the three-dimensional structures of lipid vesicles. The program is used to analyze the molecular architecture of small unilamellar vesicles of dipalmitoyl-phosphatidylcholine and is demonstrated as a worthwhile investigative tool for determining the factors that govern the minimum vesicle size.
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Affiliation(s)
- S M Lawrence
- Department of Pharmacy, King's College, University of London, UK
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1634
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Abstract
Using a systematic approach for the acceptance of crystallographic phase assignment, based on the evaluation of triplet structure invariants, electron and x-ray diffraction data from phospholipid multilamellar arrays are analyzed by direct methods. After calculation of Fourier maps with a partial set of phased structure factor magnitudes, the structure is refined in real space by flattening of the hydrocarbon region of the bilayer and an optimal solution is sought either by the calculation of [delta rho 4] suggested by Luzzati, where rho is the structure density or by a test of density smoothness [magnitude of delta rho/ delta r magnitude of], where r positions are located along the normal to the lamellar surface. Reanalyses of previously determined structures sometimes lead to new conclusions (e.g., a possible similarity of the electron density profile for DL-DMPE and L-DMPE, and a clear indication of the fatty acid adduct in the mixed L-DPPC/palmitic acid bilayer). Because of presumed secondary scattering perturbations (primarily to the least intense reflections), the refinements of the electron diffraction intensities are less easily evaluated than those carried out with x-ray diffraction data.
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Affiliation(s)
- D L Dorset
- Electron Diffraction Department, Medical Foundation of Buffalo, Inc., New York 14203
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1635
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Abstract
Membrane bilayers of dipalmitoyl phosphatidylcholine (DPPC) and dipalmitoyl phosphatidylethanolamine (DPPE) adsorbed to a freshly cleaved mica substrate have been imaged by Atomic Force Microscopy (AFM). The membranes were mounted for imaging by two methods: (a) by dialysis of a detergent solution of the lipid in the presence of the substrate material, and (b) by adsorption of lipid vesicles onto the substrate surface from a vesicle suspension. The images were taken in air, and show lipid bilayers adhering to the surface either in isolated patches or in continuous sheets, depending on the deposition conditions. Epifluorescence light-microscopy shows that the lipid is distributed on the substrate surfaces as seen in the AFM images. In some instances, when DPPE was used, whole, unfused vesicles, which were bound to the substrate, could be imaged by the AFM. Such membranes should be capable of acting as natural anchors for imaging membrane proteins by AFM.
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Affiliation(s)
- S Singh
- Department of Chemistry, University of New Mexico, Albuquerque 87131
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1636
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Abstract
A method for determination of membrane partition coefficients of five fluorescent membrane probes, 1,6-diphenyl-1,3,5-hexatriene (DPH), p-((6-phenyl)-1,3,5-hexatrienyl) benzoic acid (DPH carboxylic acid), 3-(p-(6-phenyl)-1,3,5-hexatrienyl)phenylpropionic acid (DPH propionic acid), 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) and N-4-(4-didecylaminostyryl)-N-methylpyridinium iodide (4-di-10-ASP), was developed utilizing the fluorescence enhancement of a constant probe concentration by titration with excess phospholipid liposomes. The partition coefficients of DPH, DPH carboxylic acid, DPH propionic acid, TMA-DPH and 4-di-10-ASP into dipalmitoylphosphatidylcholine membranes were determined to be 1.3.10(6), 1.0.10(6), 6.5.10(5), 2.4.10(5) and 2.8.10(6) respectively. Knowledge of the partition coefficients may help select a lipid concentration for membrane studies that necessitate a probe's dominant incorporation into membranes.
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Affiliation(s)
- Z J Huang
- Molecular Probes, Inc., Eugene, OR 97402
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1637
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Abstract
To study the structural requirements of the molecular interactions between cholesterol and sphingomyelins in model membranes, sphingomyelin derivatives were synthesized in which (a) the 3-hydroxy group was replaced with a hydrogen atom or with a methoxy, ethoxy, or tetrahydropyranyloxy group, (b) the N-acyl chain length was varied, and (c) the N-acyl chain length contained an alpha-hydroxy group. The chemical syntheses of these derivatives from DL-erythro-sphingosine are reported. The properties of these sphingomyelin derivatives were examined in monolayer membranes at the air/water interface. The mean molecular area of the pure N-stearoylsphingomyelin derivatives was determined, and the effects of cholesterol on the condensation of sphingomyelin packing in the monolayer were recorded. It was observed that replacement of the 3-hydroxy group of sphingomyelin with a hydrogen atom or its substitution with a methoxy or ethoxy group did not affect the ability of cholesterol to condense the molecular packing in monolayers. Even when a bulky tetrahydropyranyloxy group was introduced at the 3-hydroxy position of egg sphingomyelin, cholesterol was still able to condense the molecular packing of this derivative. The condensing effect of cholesterol on derivatives of N-stearoyl-SPMs was significantly larger than the comparable effect observed with 1,2-distearoyl-sn-glycero-3-phosphocholine or 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. Our results with 3-hydroxysphingomyelins having differing N-acyl chain lengths (i.e., N-stearoyl, N-myristoyl, and N-lauroyl), and with 3-hydroxy-N-(alpha-hydroxypalmitoyl)sphingomyelin also indicated that cholesterol was able to induce condensation of the molecular packing.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L Grönberg
- Department of Biochemistry and Pharmacy, Abo Akademi University, Turku, Finland
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1638
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Biondi AC, Féliz MR, Disalvo EA. Surface changes induced by osmotic stress and its influence on the glycerol permeability in lipid bilayers. Biochim Biophys Acta 1991; 1069:5-13. [PMID: 1932049 DOI: 10.1016/0005-2736(91)90097-r] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The penetration rate of glycerol across lipid bilayers can be assayed dispersing liposomes filled with a 0.1 M glucose solution in an isotonic or a hypertonic solution of glycerol. The kinetic of glycerol permeation is found to be different in each of those cases. Liposomes dispersed above the phase transition temperature in hypertonic solutions show an increase in the surface polarization as measured by means of merocyanine 540. Under this condition, the permeation of glycerol shows a two-step kinetic which is indicative of a non-fickean diffusion process. In contrast, liposomes dispersed in isotonic solutions of the permeant show a fickean behavior. The changes in polarization of the membrane interface are ascribed to variations in the surface potential due to the osmotic collapse and the glycerol concentration in contact with the outer surface. The permeability of polar molecules can, in consequence, be considered as a function of the surface potential of the liposome which is congruent with previous data in literature reporting that water permeability increases as a function of the zeta potential of liposomes shrunken in hypertonic solutions.
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Affiliation(s)
- A C Biondi
- Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de Tucumán, Argentina
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1639
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Zeng JW, Chong PL. Interactions between pressure and ethanol on the formation of interdigitated DPPC liposomes: a study with Prodan fluorescence. Biochemistry 1991; 30:9485-91. [PMID: 1892848 DOI: 10.1021/bi00103a014] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Steady-state fluorescence of 6-propionyl-2-(dimethylamino)naphthalene (Prodan) has been employed to study the interacting effects between ethanol and pressure on the formation of the fully interdigitated dipalmitoylphosphatidylcholine (DPPC). At 1 atm and 20 degrees C, a dramatic change in the emission spectrum of Prodan fluorescence is observed at about 1.1-1.3 M ethanol. The emission maximum shifts to longer wavelengths, and the intensity ratio of Prodan fluorescence at 435 nm to that at 510 nm, F435/F510, decreases abruptly with increasing ethanol content. The spectral changes are correlated to the ethanol-induced phase transition of DPPC from the noninterdigitated gel state to the fully interdigitated gel state [Rowe, E.S. (1983) Biochemistry 22, 3299-3305; Simon, S.A., & McIntosh, T.J. (1984) Biochim. Biophys. Acta 773, 169-172]. The spectral changes are attributed to the probe relocation from a less polar environment to a more polar environment due to lipid interdigitation. This relocation is either due to the bulky terminal methyl group of the lipids or due to the partition of Prodan into the bulk solution or both. The present study demonstrates that Prodan is a useful probe in monitoring the formation of the ethanol-induced fully interdigitated DPPC gel phase. Pressure is found to produce spectral changes similar to those induced by ethanol when the ethanol content amounts to 0.8-1.1 M. At lower (e.g., less than 0.4 M) and higher ethanol (e.g., greater than 2.4 M) concentrations, pressure is unable to induce such spectral changes. The critical ethanol concentrations for the formation of the fully interdigitated DPPC gel phase (Cr) have been determined.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J W Zeng
- Department of Biochemistry, Meharry Medical College, Nashville, Tennessee 37208
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1640
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Abstract
The fluid-phase behavior of binary mixtures of cholesterol with phosphatidylcholines is investigated using magnetic resonance methods. Phospholipid biradicals provide the electron spin resonance spectroscopic resolution of two immiscible fluid phases in the dipalmitoylphosphatidylcholine-cholesterol system. Isotropic chemical shifts of the phospholipid carbonyl carbons in binary mixtures with cholesterol measured using solid-state high-resolution nuclear magnetic resonance methods furnish evidence for a putative hydrogen bond between the 3 beta-hydroxyl of cholesterol and the sn-2 carbonyl of the phospholipid. The location in the bilayer of cholesterol in the two fluid phases is determined by measuring spin label-enhanced spin-lattice relaxation rates of the 13C nuclei of both the phospholipid and cholesterol molecules. These results suggest, in a time-averaged sense, that in the cholesterol-poor fluid phase the cholesterol molecule essentially spans the bilayer, whereas in the cholesterol-rich fluid phase the molecule is present in both monolayers of the bilayer.
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Affiliation(s)
- M B Sankaram
- Department of Biochemistry, University of Virginia Health Sciences Center, Charlottesville 22908
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1641
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Nag K, Boland C, Rich N, Keough KM. Epifluorescence microscopic observation of monolayers of dipalmitoylphosphatidylcholine: dependence of domain size on compression rates. Biochim Biophys Acta 1991; 1068:157-60. [PMID: 1911829 DOI: 10.1016/0005-2736(91)90204-l] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A fluorescence microscopic technique was used to observe phase transitions in monolayers of DPPC. The sizes of the domain structures observed were found to be dependent on the rate of compression of the monolayer. The distribution of domain sizes for different rates of compression were unimodal, but the scatter in the sizes was greater during slow compressions.
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Affiliation(s)
- K Nag
- Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada
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1642
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Mendelsohn R, Davies MA, Schuster HF, Xu ZC, Bittman R. CD2 rocking modes as quantitative infrared probes of one-, two-, and three-bond conformational disorder in dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylcholine/cholesterol mixtures. Biochemistry 1991; 30:8558-63. [PMID: 1888722 DOI: 10.1021/bi00099a010] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The use of CD2 rocking modes in the IR spectrum as quantitative probes of phospholipid conformational disorder has recently been described for aqueous dispersions of 1,2-dipalmitoylphosphatidylcholine (DPPC) and DPPC/cholesterol mixtures [Mendelsohn et al. (1989) Biochemistry 28, 8934-8939; Davies et al. (1990) Biochemistry 29, 4368-4373]. Initial studies focused at the 4, 6, and 10 acyl chain positions of DPPC. In the current work, the method is extended to the 2, 3, 12, and 13 positions. Conformational disorder in the L alpha phase is approximately the same (about 20% gauche) at positions 4, 10, and 13, but an unexpected higher value is observed (about 30%) at the 6 position. Cholesterol (33 mol%) restricts gauche rotamer formation by factors ranging from 6 to 9 at positions 4 and 6, respectively, to 1.5-2 at positions 10, 12, and 13. Quantitative analysis for the DPPC/cholesterol "liquid-ordered" phase indicates the occurrence of 1.2 gauche bonds/chain, a marked reduction from the 3.6-4.2 gauche bonds/chain for DPPC alone. Proximity to the ester moiety at acyl chain position 3 perturbs the vibrational coupling patterns of the CD2 rocking modes and eliminates their sensitivity to conformational change. In addition, the feasibility of a method based on the conformation-dependent coupling between CD2 rocking frequencies of two successive CD2 groups for the quantitative detection of specific, position-dependent king (gtg') and isolated gauche (gtt) conformers is demonstrated. Finally, comparisons between IR measurements and explicit theoretical predictions of acyl chain conformational order are presented.
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Affiliation(s)
- R Mendelsohn
- Department of Chemistry, Newark College of Arts and Sciences, Rutgers University, New Jersey 07102
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1643
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Tchoreloff P, Gulik A, Denizot B, Proust JE, Puisieux F. A structural study of interfacial phospholipid and lung surfactant layers by transmission electron microscopy after Blodgett sampling: influence of surface pressure and temperature. Chem Phys Lipids 1991; 59:151-65. [PMID: 1742808 DOI: 10.1016/0009-3084(91)90004-u] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Monolayer studies of the lung surfactant extract (LSE), dipalmitoyl phosphatidilcholine (DPPC) and dioleyl phosphatidilcholine (DOPC) have been performed in the dynamic condition at various temperatures. These compounds were also studied by differential scanning calorimetry, and the Langmuir Blodgett films were examined by electron microscopy. The combination of these techniques allowed us to describe precisely the collapse process, which was found to be different above and below the transition temperature of the lipids. However, whereas a phase separation for DPPC/DOPC mixtures occurred at all temperatures studied, this separation was observed for LSE only at temperatures lower than that characteristic of the "rigid state" to "liquid-like state" transition temperature. The ability of LSE to rapidly respread upon decompression appears to be due to the formation of piled amorphous aggregates formed during compression of its monolayers.
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Affiliation(s)
- P Tchoreloff
- Physico-chimie des Surfaces et Innovation en Pharmacotechnie, URA CNRS 1218, UFR des Sciences pharmaceutiques, Paris XI, Chatenay Malabry, France
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1644
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Ambrosini A, Bertoli E, Tanfani F, Zolese G. Effect of the fungicides tributyltin acetate and tributyltin chloride on multilamellar liposomes: fluorescence studies. Chem Phys Lipids 1991; 59:189-97. [PMID: 1742811 DOI: 10.1016/0009-3084(91)90007-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The influence of tri-n-butyltin acetate (TBTA) and tri-n-butyltin chloride (TBTC) on the physico-chemical state of charged and neutral phospholipids was investigated using multilamellar liposomes. The thermal dependence of steady state fluorescence polarization of DPH and its charged derivative TMA-DPH was recorded. The two fungicides lowered DPPC phase transition temperature and broadened the temperature range of the transition in different ways. The effects were concentration-dependent. The results show that TBTC interacts more effectively with DPPC model membranes rather than TBTA. Moreover, TBTC broadens and shifts the main phase transition (Tm) more effectively in DPPC rather than in DMPC liposomes. Below Tm, TBTC decreases fluorescence polarization (P) in all phospholipids used. Above Tm P is almost constant in phospholipids with saturated acyl chains, except for DMPG. In fact, an increase of P is detectable in this lipid as in PLs with unsaturated acyl chains. It is suggested that the effects of TBT on liposomal membranes are dependent on the anion moiety and phospholipids characteristics.
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Affiliation(s)
- A Ambrosini
- Istituto di Biochimica, Facoltà di Medicina e Chirurgia, Università di Ancona, Italy
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1645
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Oosterlaken-Dijksterhuis MA, Haagsman HP, van Golde LM, Demel RA. Interaction of lipid vesicles with monomolecular layers containing lung surfactant proteins SP-B or SP-C. Biochemistry 1991; 30:8276-81. [PMID: 1868098 DOI: 10.1021/bi00247a024] [Citation(s) in RCA: 113] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Pulmonary surfactant contains two families of hydrophobic proteins, SP-B and SP-C. Both proteins are thought to promote the formation of the phospholipid monolayer at the air-fluid interface of the lung. The Wilhelmy plate method was used to study the involvement of SP-B and SP-C in the formation of phospholipid monolayers. The proteins were either present in the phospholipid vesicles which were injected into the subphase or included in a preformed phospholipid monolayer. In agreement with earlier investigators, we found that SP-B and SP-C, present in phospholipid vesicles, were able to induce the formation of a monolayer, as became apparent by an increase in surface pressure. However, when the proteins were present in a preformed phospholipid monolayer (20 mN/m) at similar lipid to protein ratios, the rate of surface pressure increase after injection of pure phospholipid vesicles into the subphase at similar vesicle concentrations was 10 times higher. The process of phospholipid insertion from phospholipid vesicles into the protein-containing monolayers was dependent on (1) the presence of (divalent) cations, (2) the phospholipid concentration in the subphase, (3) the size of the phospholipid vesicles, (4) the protein concentration in the preformed monolayer, and (5) the initial surface pressure at which the monolayers were formed. Both in vesicles and in preformed monolayers, SP-C was less active than SP-B in promoting the formation of a phospholipid monolayer. The use of preformed monolayers containing controlled protein concentrations may allow more detailed studies on the mechanism by which the proteins enhance phospholipid monolayer formation from vesicles.
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1646
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Piknová B, Hianik T, Shestimirov VN, Shnyrov VL. Thermodynamical characteristics and volume compressibility of dipalmitoylphosphatidylcholine liposomes containing bacteriorhodopsin. Gen Physiol Biophys 1991; 10:395-409. [PMID: 1769518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The effects of bacteriorhodopsin (BR) interaction with large dipalmitoylphosphatidylcholine (DPPC) liposomes (approx. 100 nm in diameter) were examined at various BR/DPPC ratios, using differential scanning calorimetry (DSC) and ultrasonic velocimetry (USV). On DSC, the lipid phase transition temperature, Tc, and the half-width of the phase transition peak, delta T1/2, showed significant non-monotonic changes with the increasing BR concentration. Two exponential segments could be distinguished in the dependence of the transition enthalpy change per mol of lipid (delta H/nL) on the BR/DPPC ratio: one corresponding to ratios between 0:1 and 1:64, and another corresponding to ratios between 1:44 and 1:16. A maximal value of delta H/nL was observed for BR/DPPC ratio 1:44, probably corresponding to maximal BR-lipid ordering with each BR molecule being surrounded by two layers of lipid molecules. The nonmonotonic changes of thermodynamical parameters suggest long-distance interactions between regions of altered bilayer structure which form around each BR molecule. The results obtained with USV provided support for the above conclusions. The dependence of ultrasound velocity increment A on BR concentration supplies information on relative changes of membrane volume compressibility. Decreasing volume compressibility is reflected in increasing values of parameter A. Within T less than Tc, the values of A increased with the increasing BR concentration; saturation was observed at BR/DPPC ratio 1:500 (A = A(BR/DPPC]. No significant BR-concentration dependent changes of A were observed at T greater than Tc. From these values the average diameter of the distorted region of lipid bilayer was estimated to be approximately 20 nm.
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Affiliation(s)
- B Piknová
- Department of Biophysics, Faculty of Mathematics and Physics, Comenius University, Bratislava, CSFR
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1647
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Bultmann T, Lin HN, Wang ZQ, Huang CH. Thermotropic and mixing behavior of mixed-chain phosphatidylcholines with molecular weights identical with that of L-alpha-dipalmitoylphosphatidylcholine. Biochemistry 1991; 30:7194-202. [PMID: 1854730 DOI: 10.1021/bi00243a022] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The thermotropic phase behavior of 10 mixed-chain phosphatidylcholines, in excess water, has been examined and compared with that of identical-chain C(16):C(16)PC by using high-resolution differential scanning calorimetry (DSC). The molecular weights (MW) of these 11 molecular species are the same, but their delta C/CL values, or the normalized chain length differences, vary considerably, ranging from 0.035 to 0.540. The thermodynamic parameters (Tm, delta H, and delta S) associated with the main phase transitions for these lipid dispersions exhibit biphasic V-shaped curves, when plotted against delta C/CL. Similar characteristic curves have been reported previously for aqueous dispersions of mixed-chain phosphatidylcholines with MW identical with that of C(17):C(17)PC [Lin et al. (1990) Biochemistry 29, 7063-7072]. The initial decrease in Tm (delta H or delta S) with increasing values of delta C/CL is attributed to the progressive increase in the magnitude of the chain-terminal perturbations on the conformational statistics of the adjacent hydrocarbon chains and hence the lateral chain-chain interactions of these mixed-chain phosphatidylcholines in the gel-state bilayer. At delta C/CL approximately equal to 0.42, the chain-end perturbation is presumably at its maximum; beyond this point, the highly asymmetric phosphatidylcholines are proposed to pack, at T less than Tm, into the mixed interdigitated bilayer. In this new packing mode, the methyl ends of the longer acyl chains are relocated at the interfaces between the hydrocarbon core of the bilayer and the aqueous medium. This disposition of the bulky chain ends releases a certain degree of chain-chain packing disorders, leading to an increase in Tm (delta H or delta S) with increasing delta C/CL.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- T Bultmann
- Department of Biochemistry, University of Virginia, Charlottesville 22908
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1648
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Tamura K, Kaminoh Y, Kamaya H, Ueda I. High pressure antagonism of alcohol effects on the main phase-transition temperature of phospholipid membranes: biphasic response. Biochim Biophys Acta 1991; 1066:219-24. [PMID: 1854785 DOI: 10.1016/0005-2736(91)90189-f] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The combined effects of high pressure (up to 300 bar) and a homologous series of 1-alkanols (ethanol C2 to 1-tridecanol C13) were studied on the main phase-transition temperature of dipalmitoylphosphatidylcholine (DPPC) vesicle membranes. It is known that short-chain alkanols depress and long-chain alkanols elevate the main transition temperature. The crossover from depression to elevation occurs at the carbon-chain length about C10-C12 in DPPC vesicle membranes coinciding with the cutoff chain-length where anesthetic potency suddenly disappears. Alkanols shorter than C8 linearly decreased the transition temperature and high pressure antagonized the temperature depression. Alkanols longer than C10 showed biphasic dose-response curves. High pressure enhanced the biphasic response. In addition, alkanols longer than the cutoff length depressed the transition temperature under high pressure at the low concentration range. These non-anesthetic alkanols may manifest anesthetic potency under high pressure. At higher concentrations, the temperature elevatory effect was accentuated by pressure. This biphasic effect of long-chain alkanols is not related to the 'interdigitation' associated with short-chain alkanols. The increment of the transition temperature by pressure was 0.0242 K bar-1 in the absence of alkanols. The volume change of the transition was estimated to be 27.7 cm3 mol-1. This value stayed constant to the limit of the present study of 300 bar.
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Affiliation(s)
- K Tamura
- Department of Anesthesia, University of Utah College of Medicine, Salt Lake City
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1649
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Abstract
We have investigated the interaction of solutes found to accumulate in biological systems during chilling, dehydration, and salt stress with fully hydrated multilamellar and unilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC). We have focused on a series of mono-, di-, and tri-substituted amines (glycine, 4-hydroxyproline, proline, and betaine) and contrasted the action of these solutes to trehalose, a protective disaccharide. Differential scanning calorimetry studies show that when DPPC is scanned in the presence of increasing concentrations of these solutes (up to 3 M), there is a moderate increase in the pre-transition temperature (1-6 degrees C) with a smaller increase (1-2 degrees C) in the main transition temperature of hydrated multilamellar vesicles of DPPC. Other calorimetric parameters (delta H, delta T1/2, Cpmax) determined for the pre-transition and main transition were similar independent of the solute. In each case, the main phase transition was broadened with increasing solute while the transition enthalpy was not significantly affected.
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Affiliation(s)
- A S Rudolph
- Bio/Molecular Engineering Branch, Naval Research Laboratory, Washington, DC 20375-5000
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1650
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Krull UJ, Brown RS, Vandenberg ET, Heckl WM. Determination of the physical structure of biological materials at biosensor interfaces by techniques of increasing magnification from microscopic to molecular scale. J Electron Microsc Tech 1991; 18:212-22. [PMID: 1880594 DOI: 10.1002/jemt.1060180303] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Chemical selectivity of biosensors is derived from biological materials interfaced to the surface of transducing devices. Molecular recognition events lead to macroscopic function suitable for analytical measurements. The structure-function relationships of biochemical species at interfaces must be established to characterize and optimize biosensor operation. The techniques of ellipsometry, fluorescence microscopy, electron microscopy, and scanning tunneling microscopy are used to investigate the structure of monolayers and multilayers of proteins and lipids at interfaces that are prepared by Langmuir-Blodgett techniques and by self-assembly from bulk solution. The relative merits and limitations of the measurement techniques in the determination of aspects of interfacial structure are considered.
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Affiliation(s)
- U J Krull
- Department of Chemistry, University of Toronto, Mississauga, Ontario, Canada
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