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Tatulian SA. Analysis of protein-protein and protein-membrane interactions by isotope-edited infrared spectroscopy. Phys Chem Chem Phys 2024; 26:21930-21953. [PMID: 39108200 DOI: 10.1039/d4cp01136h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2024]
Abstract
The objective of this work is to highlight the power of isotope-edited Fourier transform infrared (FTIR) spectroscopy in resolving important problems encountered in biochemistry, biophysics, and biomedical research, focusing on protein-protein and protein membrane interactions that play key roles in practically all life processes. An overview of the effects of isotope substitutions in (bio)molecules on spectral frequencies and intensities is given. Data are presented demonstrating how isotope-labeled proteins and/or lipids can be used to elucidate enzymatic mechanisms, the mode of membrane binding of peripheral proteins, regulation of membrane protein function, protein aggregation, and local and global structural changes in proteins during functional transitions. The use of polarized attenuated total reflection FTIR spectroscopy to identify the spatial orientation and the secondary structure of a membrane-bound interfacial enzyme and the mode of lipid hydrolysis is described. Methods of production of site-directed, segmental, and domain-specific labeling of proteins by the synthetic, semisynthetic, and recombinant strategies, including advanced protein engineering technologies such as nonsense suppression and frameshift quadruplet codons are overviewed.
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Affiliation(s)
- Suren A Tatulian
- Department of Physics, University of Central Florida, Orlando, FL 32816, USA.
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2
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Chen X, Al-Mualem ZA, Baiz CR. Lipid Landscapes: Vibrational Spectroscopy for Decoding Membrane Complexity. Annu Rev Phys Chem 2024; 75:283-305. [PMID: 38382566 DOI: 10.1146/annurev-physchem-090722-010230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Cell membranes are incredibly complex environments containing hundreds of components. Despite substantial advances in the past decade, fundamental questions related to lipid-lipid interactions and heterogeneity persist. This review explores the complexity of lipid membranes, showcasing recent advances in vibrational spectroscopy to characterize the structure, dynamics, and interactions at the membrane interface. We include an overview of modern techniques such as surface-enhanced infrared spectroscopy as a steady-state technique with single-bilayer sensitivity, two-dimensional sum-frequency generation spectroscopy, and two-dimensional infrared spectroscopy to measure time-evolving structures and dynamics with femtosecond time resolution. Furthermore, we discuss the potential of multiscale molecular dynamics (MD) simulations, focusing on recently developed simulation algorithms, which have emerged as a powerful approach to interpret complex spectra. We highlight the ongoing challenges in studying heterogeneous environments in multicomponent membranes via current vibrational spectroscopic techniques and MD simulations. Overall, this review provides an up-to-date comprehensive overview of the powerful combination of vibrational spectroscopy and simulations, which has great potential to illuminate lipid-lipid, lipid-protein, and lipid-water interactions in the intricate conformational landscape of cell membranes.
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Affiliation(s)
- Xiaobing Chen
- Department of Chemistry, University of Texas at Austin, Austin, Texas, USA;
| | | | - Carlos R Baiz
- Department of Chemistry, University of Texas at Austin, Austin, Texas, USA;
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3
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Molugu TR, Thurmond RL, Alam TM, Trouard TP, Brown MF. Phospholipid headgroups govern area per lipid and emergent elastic properties of bilayers. Biophys J 2022; 121:4205-4220. [PMID: 36088534 PMCID: PMC9674990 DOI: 10.1016/j.bpj.2022.09.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 08/10/2022] [Accepted: 09/06/2022] [Indexed: 11/24/2022] Open
Abstract
Phospholipid bilayers are liquid-crystalline materials whose intermolecular interactions at mesoscopic length scales have key roles in the emergence of membrane physical properties. Here we investigated the combined effects of phospholipid polar headgroups and acyl chains on biophysical functions of membranes with solid-state 2H NMR spectroscopy. We compared the structural and dynamic properties of phosphatidylethanolamine and phosphatidylcholine with perdeuterated acyl chains in the solid-ordered (so) and liquid-disordered (ld) phases. Our analysis of spectral lineshapes of 1,2-diperdeuteriopalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE-d62) and 1,2-diperdeuteriopalmitoyl-sn-glycero-3-phosphocholine (DPPC-d62) in the so (gel) phase indicated an all-trans rotating chain structure for both lipids. Greater segmental order parameters (SCD) were observed in the ld (liquid-crystalline) phase for DPPE-d62 than for DPPC-d62 membranes, while their mixtures had intermediate values irrespective of the deuterated lipid type. Our results suggest the SCD profiles of the acyl chains are governed by methylation of the headgroups and are averaged over the entire system. Variations in the acyl chain molecular dynamics were further investigated by spin-lattice (R1Z) and quadrupolar-order relaxation (R1Q) measurements. The two acyl-perdeuterated lipids showed distinct differences in relaxation behavior as a function of the order parameter. The R1Z rates had a square-law dependence on SCD, implying collective mesoscopic dynamics, with a higher bending rigidity for DPPE-d62 than for DPPC-d62 lipids. Remodeling of lipid average and dynamic properties by methylation of the headgroups thus provides a mechanism to control the actions of peptides and proteins in biomembranes.
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Affiliation(s)
- Trivikram R Molugu
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona
| | | | - Todd M Alam
- Department of Organic Materials Science, Sandia National Laboratories, Albuquerque, New Mexico
| | - Theodore P Trouard
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona
| | - Michael F Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona; Department of Physics, University of Arizona, Tucson, Arizona.
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4
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Cheng V, Conboy JC. Inhibitory Effect of Lanthanides on Native Lipid Flip-Flop. J Phys Chem B 2022; 126:7651-7663. [PMID: 36129784 DOI: 10.1021/acs.jpcb.2c04039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The influence of ytterbium ions (Yb3+), a commonly used paramagnetic NMR chemical shift reagent, on the physical properties and flip-flop kinetics of dipalmitoylphosphatidylcholine (DPPC) planar supported lipid bilayers (PSLBs) was investigated. Langmuir isotherm studies revealed that Yb3+ interacts strongly with the phosphate headgroup of DPPC, evidenced by the increases in shear and compression moduli. Using sum-frequency vibrational spectroscopy, changes in the acyl chain ordering and phase transition temperature were also observed, consistent with Yb3+ interacting with the phosphate headgroup of DPPC. The changes in the physical properties of the membrane were also observed to be concentration dependent, with more pronounced modification observed at low (50 μM) Yb3+ concentrations compared to 6.5 mM Tb3+, suggesting a cross-linking mechanism between adjacent DPPC lipids. Additionally, the changes in membrane packing and phase transition temperatures in the presence of Tris buffer suggested that a putative Yb(Tris)3+ complex forms that coordinates to the PC headgroup. The kinetics of DPPC flip-flop in the gel and liquid crystalline (lc) phases were substantially inhibited in the presence of Yb3+, regardless of the Yb3+ concentration. Analysis of the flip-flop kinetics under the framework of transition state theory revealed that the free energy barrier to flip-flop in both the gel and lc phases was substantial increased over a pure DPPC membrane. In the gel phase, the trend in the free energy barrier appeared to follow the trend in the shear moduli, suggesting that the Yb3+-DPPC headgroup interaction was driving the increase in the activation free energy barrier. In the lc phase, activation free energies of DPPC flip-flop in the presence of 50 μM or 6.5 mM Yb3+ were found to mirror the free energies of TEMPO-DPPC flip-flop, leading to the conclusion that the strong interaction between Yb3+ and the PC headgroup was essentially manifested as a headgroup charge modification. These studies illustrate that the presence of the lanthanide Yb3+ results in significant modification to the lipid membrane physical properties and, more importantly, results in a pronounced inhibition of native lipid flip-flop.
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Affiliation(s)
- Victoria Cheng
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - John C Conboy
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
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5
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Tsuchikawa H, Monji M, Umegawa Y, Yasuda T, Slotte JP, Murata M. Depth-Dependent Segmental Melting of the Sphingomyelin Alkyl Chain in Lipid Bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:5515-5524. [PMID: 35477243 DOI: 10.1021/acs.langmuir.2c00092] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The chain melting of lipid bilayers has often been investigated in detail using calorimetric methods, such as differential scanning calorimetry (DSC), and the resultant main transition temperature is regarded as one of the most important parameters in model membrane experiments. However, it is not always clear whether the hydrocarbon chains of lipids are gradually melting along the depth of the lipid bilayer or whether they all melt concurrently in a very narrow temperature range, as implied by DSC. In this study, we focused on stearoyl-d-sphingomyelin (SSM) as an example of raft-forming lipids. We synthesized deuterium-labeled SSMs at the 4', 10', and 16' positions, and their depth-dependent melting was measured using solid-state deuterium NMR by changing the temperature by 1.0 °C, and comparing with that observed from a saturated lipid, palmitoylstearoylphosphatidylcholine (PSPC). The results showed that SSM exhibited a characteristic depth-dependent melting, which was not observed for PSPC. The strong intermolecular hydrogen bonds between the sphingomyelin amide moiety probably caused the chain melting to start from the chain terminus through the middle part and end in the upper part. This depth-dependent melting implies that the small gel-like domains of SSM remain at temperatures slightly above the main transition temperature. These sphingomyelin features may be responsible for the biological properties of SM-based lipid rafts.
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Affiliation(s)
- Hiroshi Tsuchikawa
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560- 0043, Japan
- Faculty of Medicine, Oita University, Oita, Oita 879-5593, Japan
| | - Mami Monji
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560- 0043, Japan
| | - Yuichi Umegawa
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560- 0043, Japan
- Project Research Center for Fundamental Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Tomokazu Yasuda
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560- 0043, Japan
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Tykistökatu 6A, Turku FIN-20520, Finland
| | - Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560- 0043, Japan
- Project Research Center for Fundamental Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
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6
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Insights into molecular mechanism of action of citrus flavonoids hesperidin and naringin on lipid bilayers using spectroscopic, calorimetric, microscopic and theoretical studies. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.118411] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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7
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Abstract
The interactions between lipids and proteins are one of the most fundamental processes in living organisms, responsible for critical cellular events ranging from replication, cell division, signaling, and movement. Enabling the central coupling responsible for maintaining the functionality of the breadth of proteins, receptors, and enzymes that find their natural home in biological membranes, the fundamental mechanisms of recognition of protein for lipid, and vice versa, have been a focal point of biochemical and biophysical investigations for many decades. Complexes of lipids and proteins, such as the various lipoprotein factions, play central roles in the trafficking of important proteins, small molecules and metabolites and are often implicated in disease states. Recently an engineered lipoprotein particle, termed the nanodisc, a modified form of the human high density lipoprotein fraction, has served as a membrane mimetic for the investigation of membrane proteins and studies of lipid-protein interactions. In this review, we summarize the current knowledge regarding this self-assembling lipid-protein complex and provide examples for its utility in the investigation of a large number of biological systems.
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8
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Kirsch SA, Böckmann RA. Coupling of Membrane Nanodomain Formation and Enhanced Electroporation near Phase Transition. Biophys J 2019; 116:2131-2148. [PMID: 31103234 PMCID: PMC6554532 DOI: 10.1016/j.bpj.2019.04.024] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 04/17/2019] [Accepted: 04/18/2019] [Indexed: 12/29/2022] Open
Abstract
Biological cells are enveloped by a heterogeneous lipid bilayer that prevents the uncontrolled exchange of substances between the cell interior and its environment. In particular, membranes act as a continuous barrier for salt and macromolecules to ensure proper physiological functions within the cell. However, it has been shown that membrane permeability strongly depends on temperature and, for phospholipid bilayers, displays a maximum at the transition between the gel and fluid phase. Here, extensive molecular dynamics simulations of dipalmitoylphosphatidylcholine bilayers were employed to characterize the membrane structure and dynamics close to phase transition, as well as its stability with respect to an external electric field. Atomistic simulations revealed the dynamic appearance and disappearance of spatially related nanometer-sized thick ordered and thin interdigitating domains in a fluid-like bilayer close to the phase transition temperature (Tm). These structures likely represent metastable precursors of the ripple phase that vanished at increased temperatures. Similarly, a two-phase bilayer with coexisting gel and fluid domains featured a thickness minimum at the interface because of splaying and interdigitating lipids. For all systems, application of an external electric field revealed a reduced bilayer stability with respect to pore formation for temperatures close to Tm. Pore formation occurred exclusively in thin interdigitating membrane nanodomains. These findings provide a link between the increased membrane permeability and the structural heterogeneity close to phase transition.
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Affiliation(s)
- Sonja A Kirsch
- Computational Biology, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen, Germany
| | - Rainer A Böckmann
- Computational Biology, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen, Germany.
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9
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Pezeshkian W, Khandelia H, Marsh D. Lipid Configurations from Molecular Dynamics Simulations. Biophys J 2018; 114:1895-1907. [PMID: 29694867 PMCID: PMC5937052 DOI: 10.1016/j.bpj.2018.02.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 02/09/2018] [Accepted: 02/13/2018] [Indexed: 01/10/2023] Open
Abstract
The extent to which current force fields faithfully reproduce conformational properties of lipids in bilayer membranes, and whether these reflect the structural principles established for phospholipids in bilayer crystals, are central to biomembrane simulations. We determine the distribution of dihedral angles in palmitoyl-oleoyl phosphatidylcholine from molecular dynamics simulations of hydrated fluid bilayer membranes. We compare results from the widely used lipid force field of Berger et al. with those from the most recent C36 release of the CHARMM force field for lipids. Only the CHARMM force field produces the chain inequivalence with sn-1 as leading chain that is characteristic of glycerolipid packing in fluid bilayers. The exposure and high partial charge of the backbone carbonyls in Berger lipids leads to artifactual binding of Na+ ions reported in the literature. Both force fields predict coupled, near-symmetrical distributions of headgroup dihedral angles, which is compatible with models of interconverting mirror-image conformations used originally to interpret NMR order parameters. The Berger force field produces rotamer populations that correspond to the headgroup conformation found in a phosphatidylcholine lipid bilayer crystal, whereas CHARMM36 rotamer populations are closer to the more relaxed crystal conformations of phosphatidylethanolamine and glycerophosphocholine. CHARMM36 alone predicts the correct relative signs of the time-average headgroup order parameters, and reasonably reproduces the full range of NMR data from the phosphate diester to the choline methyls. There is strong motivation to seek further experimental criteria for verifying predicted conformational distributions in the choline headgroup, including the 31P chemical shift anisotropy and 14N and CD3 NMR quadrupole splittings.
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Affiliation(s)
- Weria Pezeshkian
- MEMPHYS-Centre for Biomembrane Physics, University of Southern Denmark, Odense M, Denmark
| | - Himanshu Khandelia
- MEMPHYS-Centre for Biomembrane Physics, University of Southern Denmark, Odense M, Denmark
| | - Derek Marsh
- MEMPHYS-Centre for Biomembrane Physics, University of Southern Denmark, Odense M, Denmark; Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany.
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10
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Lonhus K, Budianska L, Lisetski L. Meaning of activation energy in phospholipid multibilayers phase transitions. Chem Phys Lipids 2017; 206:53-59. [PMID: 28596068 DOI: 10.1016/j.chemphyslip.2017.04.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 04/21/2017] [Accepted: 04/26/2017] [Indexed: 01/20/2023]
Abstract
The question of the activation energy of phase transitions in lyotropic liquid crystal phases of model phospholipid membranes was considered. In our experiments, we obtained DSC thermograms of hydrated DPPC and DMPC at different scanning rates, and activation energy values were determined by a modification of Kissinger non-isothermal kinetics method. Using this approach the equivalent order of reaction corresponding to the phase transition can be determined alongside the activation energy. The cooperativity of both main transition and pre-transition was shown to be strongly dependent on scanning rate, asymptotically tending to a certain value at high rates, which corresponds to the number of lipid molecules in two concentric layers of hexagonal tiling. Changes in pretransition activation energy are shown to be proportional to changes in the system volume during the pretransition process, while the tail-length dependent part of the main transition activation energy is proportional to the jump in the number of gauche isomers.
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Affiliation(s)
- K Lonhus
- V. N. Karazin Kharkiv National University, Kharkiv, Ukraine; Institute for Scintillation Materials, STC "Institute for Single Crystals" of National Academy of Sciences of Ukraine, Kharkiv, Ukraine.
| | - L Budianska
- Institute for Scintillation Materials, STC "Institute for Single Crystals" of National Academy of Sciences of Ukraine, Kharkiv, Ukraine
| | - L Lisetski
- Institute for Scintillation Materials, STC "Institute for Single Crystals" of National Academy of Sciences of Ukraine, Kharkiv, Ukraine
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11
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Sun L, Böckmann RA. Membrane phase transition during heating and cooling: molecular insight into reversible melting. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2017; 47:151-164. [PMID: 28725998 DOI: 10.1007/s00249-017-1237-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 06/18/2017] [Accepted: 06/28/2017] [Indexed: 11/25/2022]
Abstract
With increasing temperature, lipid bilayers undergo a gel-fluid phase transition, which plays an essential role in many physiological phenomena. In the present work, this first-order phase transition was investigated for variable heating and cooling rates for a dipalmitoylphosphatidylcholine (DPPC) lipid bilayer by means of atomistic molecular dynamics simulations. Alternative methods to track the melting temperature [Formula: see text] are compared. The resulting [Formula: see text] is shown to be independent of the scan rate for small heating rates (0.05-0.3 K/ns) implying reversible melting, and increases for larger heating (0.3-4 K/ns) or cooling rates (2-0.1 K/ns). The reported dependency of the melting temperature on the heating rate is in perfect agreement with a two-state kinetic rate model as suggested previously. Expansion and shrinkage, as well as the dynamics of melting seeds is described. The simulations further exhibit a relative shift between melting seeds in opposing membrane leaflets as predicted from continuum elastic theory.
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Affiliation(s)
- Liping Sun
- Computational Biology, Department of Biology, Friedrich-Alexander-University of Erlangen-Nürnberg, Staudtstrasse 5, Erlangen, 91058, Germany
| | - Rainer A Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander-University of Erlangen-Nürnberg, Staudtstrasse 5, Erlangen, 91058, Germany.
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12
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Allhusen JS, Kimball DR, Conboy JC. Structural Origins of Cholesterol Accelerated Lipid Flip-Flop Studied by Sum-Frequency Vibrational Spectroscopy. J Phys Chem B 2016; 120:3157-68. [PMID: 26978577 DOI: 10.1021/acs.jpcb.6b01254] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The unique structure of cholesterol and its role in modulating lipid translocation (flip-flop) were examined using sum-frequency vibrational spectroscopy (SFVS). Two structural analogues of cholesterol--cholestanol and cholestene--were examined to explore the influence of ring rigidity and amphiphilicity on controlling distearoylphosphocholine (DSPC) flip-flop. Kinetic rates for DSPC flip-flop were determined as a function of sterol concentration and temperature. All three sterols increased the rate of DSPC flip-flop in a concentration-dependent manner following the order cholestene > cholestanol > cholesterol. Rates of DSPC flip-flop were used to calculate the thermodynamic activation free energy barrier (ΔG(‡)) in the presence of cholesterol, cholestanol, and cholestene. The acyl chain gauche content of DSPC, mean lipid area, and membrane compressibility were correlated to observed trends in ΔG(‡). ΔG(‡) for DSPC flip-flop showed a strong positive correlation with the molar compression modulus (K*) of the membrane, influenced by the type and concentration of the sterol added. Interestingly, cholesterol is distinctive in maintaining invariant membrane compressibility over the range of 2-10 mol %. The results in this study demonstrate that the compression modulus of a membrane plays a significant role in moderating ΔG(‡) and the kinetics of native, protein-free, lipid translocation in membranes.
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Affiliation(s)
- John S Allhusen
- Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112, United States
| | - Dylan R Kimball
- Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112, United States
| | - John C Conboy
- Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112, United States
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13
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Dmitriev AA, Surovtsev NV. Temperature-Dependent Hydrocarbon Chain Disorder in Phosphatidylcholine Bilayers Studied by Raman Spectroscopy. J Phys Chem B 2015; 119:15613-22. [DOI: 10.1021/acs.jpcb.5b07502] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A. A. Dmitriev
- Novosibirsk State University, Novosibirsk, 630090, Russia
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14
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Mignolet A, Goormaghtigh E. High throughput absorbance spectra of cancerous cells: a microscopic investigation of spectral artifacts. Analyst 2015; 140:2393-401. [DOI: 10.1039/c4an01834f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Infrared spectra of cell smears change in shape with cell density.
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Affiliation(s)
- A. Mignolet
- Laboratory for the Structure and Function of Biological Membranes
- Center for Structural Biology and Bioinformatics
- Université Libre de Bruxelles (ULB)
- B-1050 Brussels
- Belgium
| | - E. Goormaghtigh
- Laboratory for the Structure and Function of Biological Membranes
- Center for Structural Biology and Bioinformatics
- Université Libre de Bruxelles (ULB)
- B-1050 Brussels
- Belgium
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15
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Poger D, Caron B, Mark AE. Effect of Methyl-Branched Fatty Acids on the Structure of Lipid Bilayers. J Phys Chem B 2014; 118:13838-48. [DOI: 10.1021/jp503910r] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- David Poger
- School of Chemistry and Molecular
Biosciences and ‡Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Bertrand Caron
- School of Chemistry and Molecular
Biosciences and ‡Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Alan E. Mark
- School of Chemistry and Molecular
Biosciences and ‡Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
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16
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Tripathy S, Sen R, Padhi SK, Mohanty S, Maiti NK. Upregulation of transcripts for metabolism in diverse environments is a shared response associated with survival and adaptation of Klebsiella pneumoniae in response to temperature extremes. Funct Integr Genomics 2014; 14:591-601. [PMID: 24890397 DOI: 10.1007/s10142-014-0382-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 05/17/2014] [Accepted: 05/26/2014] [Indexed: 11/28/2022]
Abstract
Klebsiella pneumoniae being ubiquitous in nature encounters wide differences in environmental condition. The organism's abundance in natural water reservoirs exposed to temperature variation forms the basis of its persistence and spread in the soil and other farm produce. In order to investigate the effect of temperature changes on the survival and adaptation of the bacteria, the transcriptional response of K. pneumoniae subjected to low (20 °C) and high (50 °C) temperature shock were executed using Applied Biosystems SOLiD platform. Approximately, 33 and 34% of protein coding genes expressed in response to 20 and 50 °C, respectively, displayed significant up- or downregulation (p < 0.01). Most of the significantly expressed transcripts mapped to metabolism, membrane transport, and cell motility were downregulated at 50 °C, except for protein folding, sorting, and degradation, suggesting that heat stress causes general downregulation of gene expression together with induction of heat shock proteins. While at 20 °C, the transcripts of carbohydrate, lipid, and amino acid metabolism were highly upregulated. Hypothetical proteins as well as canonical heat and cold shock proteins, viz. grpE, clpX, recA, and deaD were upregulated commonly in response to 20 and 50 °C. Significant upregulation of genes encoding ribosomal proteins at 20 and 50 °C possibly suggest their role in the survival of K. pneumoniae cells under low- and high-temperature stress.
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Affiliation(s)
- S Tripathy
- Microbiology unit, Division of Fish Health Management, Central Institute of Freshwater Aquaculture, Kausalyaganga, Bhubaneswar, Odisha, 751002, India
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17
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Meng X, Ye Q, Pan Q, Ding Y, Wei M, Liu Y, van de Voort FR. Total Phospholipids in Edible Oils by In-Vial Solvent Extraction Coupled with FTIR Analysis. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2014; 62:3101-3107. [PMID: 24654960 DOI: 10.1021/jf404880v] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A simple procedure for the determination of total phospholipids (TPL) in edible oils was developed by combining a single-step, in situ methanol/acetonitrile (MeOH/ACN) extraction of the oil sample followed by Fourier transform infrared (FTIR) spectroscopic analysis of the extract. Spectral analysis of extracts in a 25 μm CaF2 cell obtained using 1:1 MeOH/ACN added to oil in a 2:1 ratio indicated that measurements made using only the asymmetric phosphate diester PO2- stretching band at 1243 cm-1 in second-derivative spectra were sufficient for the accurate measurement of TPL with minimal coextracted triglyceride interferences being encountered. FTIR calibration spectra were devised using only phosphatidylcholine (PC) as a representative phospholipid standard, covering a range of 0-50000 μg/g TPL and spiked into 1:1 MeOH/ACN, capable of tracking the added PC with an SD of <200 μg/g. The FTIR method was initially validated using model PC-spiked degummed canola oil and subsequently with commercial crude and refined soy and rapeseed oils as well as a lecithin tablet with the FTIR TPL predictions compared to those of the AOCS Ca 12-55 molybdenate method. The FTIR method tracked the AOCS results well, being somewhat more reproducible than the reference method (±3.2 vs ±4.9%), which limited its accuracy relative to the AOCS reference procedure (±2.2%). The simple in-vial solvent extraction procedure, followed by FTIR analysis of the extract, is a simple, efficient, and rapid procedure that is also amenable to automation using an autosampler-equipped FTIR if multiple samples are to be analyzed.
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Affiliation(s)
- Xianghe Meng
- College of Biological and Environmental Engineering, Zhejiang University of Technology , Hangzhou 310014, China
| | - Qin Ye
- College of Biological and Environmental Engineering, Zhejiang University of Technology , Hangzhou 310014, China
| | - Qiuyue Pan
- College of Food Science and Nutritional Engineering, China Agricultural University , Beijing 100083, China
| | - Yang Ding
- College of Biological and Environmental Engineering, Zhejiang University of Technology , Hangzhou 310014, China
| | - Min Wei
- College of Biological and Environmental Engineering, Zhejiang University of Technology , Hangzhou 310014, China
| | - Yun Liu
- Beijing Key Laboratory of Bioprocess, The Biorefinery Research and Engineering Center of the Ministry of Education of China, College of Life Science and Technology, Beijing University of Chemical Technology , Beijing 100029, China
| | - Fred R van de Voort
- McGill IR Group, Department of Food Science and Agricultural Chemistry, Macdonald Campus of McGill University , Montreal H3A 0G4, Canada
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18
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Dickson CJ, Madej BD, Skjevik AA, Betz RM, Teigen K, Gould IR, Walker RC. Lipid14: The Amber Lipid Force Field. J Chem Theory Comput 2014; 10:865-879. [PMID: 24803855 PMCID: PMC3985482 DOI: 10.1021/ct4010307] [Citation(s) in RCA: 912] [Impact Index Per Article: 91.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Indexed: 11/29/2022]
Abstract
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The AMBER lipid force field has been
updated to create Lipid14,
allowing tensionless simulation of a number of lipid types with the
AMBER MD package. The modular nature of this force field allows numerous
combinations of head and tail groups to create different lipid types,
enabling the easy insertion of new lipid species. The Lennard-Jones
and torsion parameters of both the head and tail groups have been
revised and updated partial charges calculated. The force field has
been validated by simulating bilayers of six different lipid types
for a total of 0.5 μs each without applying a surface tension;
with favorable comparison to experiment for properties such as area
per lipid, volume per lipid, bilayer thickness, NMR order parameters,
scattering data, and lipid lateral diffusion. As the derivation of
this force field is consistent with the AMBER development philosophy,
Lipid14 is compatible with the AMBER protein, nucleic acid, carbohydrate,
and small molecule force fields.
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Affiliation(s)
- Callum J Dickson
- Department of Chemistry and Institute of Chemical Biology, Imperial College London , South Kensington SW7 2AZ, United Kingdom
| | - Benjamin D Madej
- San Diego Supercomputer Center, University of California San Diego , 9500 Gilman Drive MC0505, La Jolla, California 92093-0505, United States ; Department of Chemistry and Biochemistry, University of California San Diego , 9500 Gilman Drive MC0505, La Jolla, California 92093-0505, United States
| | - Age A Skjevik
- San Diego Supercomputer Center, University of California San Diego , 9500 Gilman Drive MC0505, La Jolla, California 92093-0505, United States ; Department of Biomedicine, University of Bergen , N-5009 Bergen, Norway
| | - Robin M Betz
- San Diego Supercomputer Center, University of California San Diego , 9500 Gilman Drive MC0505, La Jolla, California 92093-0505, United States
| | - Knut Teigen
- Department of Biomedicine, University of Bergen , N-5009 Bergen, Norway
| | - Ian R Gould
- Department of Chemistry and Institute of Chemical Biology, Imperial College London , South Kensington SW7 2AZ, United Kingdom
| | - Ross C Walker
- San Diego Supercomputer Center, University of California San Diego , 9500 Gilman Drive MC0505, La Jolla, California 92093-0505, United States ; Department of Chemistry and Biochemistry, University of California San Diego , 9500 Gilman Drive MC0505, La Jolla, California 92093-0505, United States
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19
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Lethu S, Matsuoka S, Murata M. Highly efficient preparation of selectively isotope cluster-labeled long chain fatty acids via two consecutive C(sp3)-C(sp3) cross-coupling reactions. Org Lett 2014; 16:844-7. [PMID: 24432759 DOI: 10.1021/ol4036159] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An efficient synthesis involving two copper-catalyzed alkyl-alkyl coupling reactions has been designed to easily access doubly isotope-labeled fatty acids. Such NMR- and IR-active compounds were obtained in excellent overall yields and will be further used for determining the conformation of an alkyl chain of lipidic biomolecules upon interaction with proteins.
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Affiliation(s)
- Sébastien Lethu
- JST ERATO, Lipid Active Structure Project and §Project Research Center for Fundamental Sciences, Osaka University , 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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20
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21
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Liu J, Brown KL, Conboy JC. The effect of cholesterol on the intrinsic rate of lipid flip–flop as measured by sum-frequency vibrational spectroscopy. Faraday Discuss 2013; 161:45-61; discussion 113-50. [DOI: 10.1039/c2fd20083j] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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22
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Recent Progress in Density Functional Methodology for Biomolecular Modeling. STRUCTURE AND BONDING 2013. [DOI: 10.1007/978-3-642-32750-6_1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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23
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Abstract
Nanodiscs are self-assembled discoidal fragments of lipid bilayers 8-16 nm in diameter, stabilized in solution by two amphipathic helical scaffold proteins. As stable and highly soluble membrane mimetics with controlled lipid composition and ability to add affinity tags to the scaffold protein, nanodiscs represent an attractive model system for solubilization, isolation, purification, and biophysical and biochemical studies of membrane proteins. In this chapter we overview various approaches to structural and functional studies of different classes of integral membrane proteins such as ion channels, transporters, GPCR and other receptors, membrane enzymes, and blood coagulation cascade proteins which have been incorporated into nanodiscs. We outline the advantages provided by homogeneity, ability to control oligomerization state of the target protein and lipid composition of the bilayer. Special attention is paid to the opportunities afforded by nanodisc system for the detailed studies of the role of different lipid properties and protein-lipid interactions in the functional behavior of membrane proteins.
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Affiliation(s)
- Mary A. Schuler
- Department of Biochemistry, University of Illinois, Urbana, IL 61801 USA
- Department of Cell and Developmental Biology, University of Illinois, Urbana, IL 61801 USA
| | - Ilia G. Denisov
- Department of Biochemistry, University of Illinois, Urbana, IL 61801 USA
| | - Stephen G. Sligar
- Department of Biochemistry, University of Illinois, Urbana, IL 61801 USA
- Department of Chemistry, University of Illinois, Urbana, IL 61801 USA
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24
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Wang L, Han X, Li J, Qin L, Zheng D. Preparation of modified mesoporous MCM-41 silica spheres and its application in pervaporation. POWDER TECHNOL 2012. [DOI: 10.1016/j.powtec.2012.07.044] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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25
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Lewis RNAH, McElhaney RN. Membrane lipid phase transitions and phase organization studied by Fourier transform infrared spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:2347-58. [PMID: 23098834 DOI: 10.1016/j.bbamem.2012.10.018] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 10/14/2012] [Indexed: 11/27/2022]
Abstract
Fourier transform infrared (FTIR) spectroscopy is a powerful yet relatively inexpensive and convenient technique for studying the structure and organization of membrane lipids in their various polymorphic phases. This spectroscopic technique yields information about the conformation and dynamics of all regions of the lipid molecule simultaneously without the necessity of introducing extrinsic probes. In this review, we summarize some relatively recent FTIR spectroscopic studies of the structure and organization primarily of fully hydrated phospholipids in their biologically relevant lamellar crystalline, gel and liquid-crystalline phases, and show that interconversions between these bilayer phases can be accurately monitored by this technique. We also briefly discuss how the structure and organization of potentially biologically relevant nonlamellar micellar or reversed hexagonal lipid phases can be studied and how phase transitions between lamellar and nonlamellar phases, or between various nonlamellar phases, can be followed as well. In addition, we discuss the potential for FTIR spectroscopy to yield fairly high resolution structural information about phospholipid packing in lamellar crystalline or gel phases. Finally, we show that many, but not all of these FTIR approaches can also yield valuable information about lipid-protein interactions in membrane protein- or peptide-containing lipid membrane bilayer model or even in biological membranes. This article is part of a Special Issue entitled: FTIR in membrane proteins and peptide studies.
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Affiliation(s)
- Ruthven N A H Lewis
- Department of Biochemistry, School of Translational Medicine, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2 H7
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26
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Jämbeck JPM, Lyubartsev AP. Derivation and systematic validation of a refined all-atom force field for phosphatidylcholine lipids. J Phys Chem B 2012; 116:3164-79. [PMID: 22352995 PMCID: PMC3320744 DOI: 10.1021/jp212503e] [Citation(s) in RCA: 418] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 02/18/2012] [Indexed: 11/29/2022]
Abstract
An all-atomistic force field (FF) has been developed for fully saturated phospholipids. The parametrization has been largely based on high-level ab initio calculations in order to keep the empirical input to a minimum. Parameters for the lipid chains have been developed based on knowledge about bulk alkane liquids, for which thermodynamic and dynamic data are excellently reproduced. The FFs ability to simulate lipid bilayers in the liquid crystalline phase in a tensionless ensemble was tested in simulations of three lipids: 1,2-diauroyl-sn-glycero-3-phospocholine (DLPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 1,2-dipalmitoyl-sn-glycero-3-phospcholine (DPPC). Computed areas and volumes per lipid, and three different kinds of bilayer thicknesses, have been investigated. Most importantly NMR order parameters and scattering form factors agree in an excellent manner with experimental data under a range of temperatures. Further, the compatibility with the AMBER FF for biomolecules as well as the ability to simulate bilayers in gel phase was demonstrated. Overall, the FF presented here provides the important balance between the hydrophilic and hydrophobic forces present in lipid bilayers and therefore can be used for more complicated studies of realistic biological membranes with protein insertions.
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Affiliation(s)
- Joakim P. M. Jämbeck
- Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, SE-10691, Sweden
| | - Alexander P. Lyubartsev
- Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, SE-10691, Sweden
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27
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Rana AA, Takafuji M, Ihara H. Effect of High Density Poly (Vinyl Octadecanoate) Grafted Silica Stationary Phase on Physiochemical Properties and Shape Selectivity Enhancement of Polycyclic Aromatic Hydrocarbons (PAHs) in RP-HPLC. SEP SCI TECHNOL 2012. [DOI: 10.1080/01496395.2011.623028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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28
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Schubert T, Schneck E, Tanaka M. First order melting transitions of highly ordered dipalmitoyl phosphatidylcholine gel phase membranes in molecular dynamics simulations with atomistic detail. J Chem Phys 2011; 135:055105. [PMID: 21823736 DOI: 10.1063/1.3615937] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Molecular dynamics simulations with atomistic detail of the gel phase and melting transitions of dipalmitoyl phosphatidylcholine bilayers in water reveal the dependency of many thermodynamic and structural parameters on the initial system ordering. We quantitatively compare different methods to create a gel phase system and we observe that a very high ordering of the gel phase starting system is necessary to observe behavior which reproduces experimental data. We performed heating scans with speeds down to 0.5 K/ns and could observe sharp first order phase transitions. Also, we investigated the transition enthalpy as the natural intrinsic parameter of first order phase transitions, and obtained a quantitative match with experimental values. Furthermore, we performed systematic investigations of the statistical distribution and heating rate dependency of the microscopic phase transition temperature.
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Affiliation(s)
- Thomas Schubert
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, Heidelberg, Germany
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29
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Sohn EH, Kim SH, Lee M, Lee JC, Song K. Surface properties and liquid crystal alignment behavior of poly(2-hydroxyethyl methacrylate) derivatives with alkyl ester side chains. J Colloid Interface Sci 2011; 360:623-32. [DOI: 10.1016/j.jcis.2011.04.070] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 04/13/2011] [Accepted: 04/19/2011] [Indexed: 11/30/2022]
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30
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Kapoor S, Werkmüller A, Denter C, Zhai Y, Markgraf J, Weise K, Opitz N, Winter R. Temperature-pressure phase diagram of a heterogeneous anionic model biomembrane system: results from a combined calorimetry, spectroscopy and microscopy study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:1187-95. [PMID: 21262194 DOI: 10.1016/j.bbamem.2011.01.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 01/17/2011] [Accepted: 01/19/2011] [Indexed: 01/13/2023]
Abstract
By using Fourier transform infrared (FT-IR) spectroscopy in combination with differential scanning calorimetry (DSC) coupled with pressure perturbation calorimetry (PPC), ultrasound velocimetry, Laurdan fluorescence spectroscopy, fluorescence microscopy and atomic force microscopy (AFM), the temperature and pressure dependent phase behavior of the five-component anionic model raft lipid mixture DOPC/DOPG/DPPC/DPPG/cholesterol (20:5:45:5:25 mol%) was investigated. A temperature range from 5 to 65 °C and a pressure range up to 16 kbar were covered to establish the temperature-pressure phase diagram of this heterogeneous model biomembrane system. Incorporation of 10-20 mol% PG still leads to liquid-ordered (l(o))-liquid-disordered (l(d)) phase coexistence regions over a wide range of temperatures and pressures. Compared to the corresponding neutral model raft mixture (DOPC/DPPC/Chol 25:50:25 mol%), the p,T-phase diagram is - as expected and in accordance with the Gibbs phase rule - more complex, the phase sequence as a function of temperature and pressure is largely similar, however. This anionic heterogeneous model membrane system will serve as a more realistic model biomembrane system to study protein interactions with anionic lipid bilayers displaying liquid-disordered/liquid-ordered domain coexistence over a wide range of the temperature-pressure plane, thus allowing also studies of biologically relevant systems encountered under extreme environmental conditions.
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Affiliation(s)
- Shobhna Kapoor
- Physical Chemistry I-Biophysical Chemistry, TU Dortmund University, Dortmund, Germany
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31
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Leftin A, Brown MF. An NMR database for simulations of membrane dynamics. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:818-39. [PMID: 21134351 DOI: 10.1016/j.bbamem.2010.11.027] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 11/18/2010] [Accepted: 11/22/2010] [Indexed: 10/18/2022]
Abstract
Computational methods are powerful in capturing the results of experimental studies in terms of force fields that both explain and predict biological structures. Validation of molecular simulations requires comparison with experimental data to test and confirm computational predictions. Here we report a comprehensive database of NMR results for membrane phospholipids with interpretations intended to be accessible by non-NMR specialists. Experimental ¹³C-¹H and ²H NMR segmental order parameters (S(CH) or S(CD)) and spin-lattice (Zeeman) relaxation times (T(1Z)) are summarized in convenient tabular form for various saturated, unsaturated, and biological membrane phospholipids. Segmental order parameters give direct information about bilayer structural properties, including the area per lipid and volumetric hydrocarbon thickness. In addition, relaxation rates provide complementary information about molecular dynamics. Particular attention is paid to the magnetic field dependence (frequency dispersion) of the NMR relaxation rates in terms of various simplified power laws. Model-free reduction of the T(1Z) studies in terms of a power-law formalism shows that the relaxation rates for saturated phosphatidylcholines follow a single frequency-dispersive trend within the MHz regime. We show how analytical models can guide the continued development of atomistic and coarse-grained force fields. Our interpretation suggests that lipid diffusion and collective order fluctuations are implicitly governed by the viscoelastic nature of the liquid-crystalline ensemble. Collective bilayer excitations are emergent over mesoscopic length scales that fall between the molecular and bilayer dimensions, and are important for lipid organization and lipid-protein interactions. Future conceptual advances and theoretical reductions will foster understanding of biomembrane structural dynamics through a synergy of NMR measurements and molecular simulations.
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Affiliation(s)
- Avigdor Leftin
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA
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32
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Anglin TC, Cooper MP, Li H, Chandler K, Conboy JC. Free energy and entropy of activation for phospholipid flip-flop in planar supported lipid bilayers. J Phys Chem B 2010; 114:1903-14. [PMID: 20073520 DOI: 10.1021/jp909134g] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Basic transition state theory is used to describe the activation thermodynamics for phospholipid flip-flop in planar-supported lipid bilayers (PSLBs) prepared by the Langmuir-Blodgett/Langmuir-Schaeffer method. The kinetics of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) flip-flop were determined as a function of temperature and lateral surface pressure using sum-frequency vibrational spectroscopy (SFVS). From the temperature and lateral pressure dependent DSPC flip-flop kinetics, a complete description of the activation thermodynamics for flip-flop in the gel state, including free energy of activation (DeltaG(++)), area of activation (Deltaa(++)), and entropy of activation (DeltaS(++)), was obtained. The free energy barrier for flip-flop of DSPC was determined to be DeltaG(++) = 105 +/- 2 kJ/mol at 40 degrees C at a deposition surface pressure of 30 mN/m. The free energy barrier was found to consist of large opposing entropic and enthalpic contributions. The influence of alkyl chain length on the activation thermodynamics of flip-flop was also investigated. Decreasing the alkyl chain length led to a decrease in DeltaG(++) due primarily to an increase in DeltaS(++). The values obtained here are compared to previous studies investigating flip-flop by vesicle based methods.
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Affiliation(s)
- Timothy C Anglin
- University of Utah, Department of Chemistry, 315 South 1400 East, Salt Lake City, Utah 84112, USA
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33
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Sobota M, Wang X, Fekete M, Happel M, Meyer K, Wasserscheid P, Laurin M, Libuda J. Ordering and Phase Transitions in Ionic Liquid-Crystalline Films. Chemphyschem 2010; 11:1632-6. [DOI: 10.1002/cphc.201000144] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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34
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Cholesterol modulates the exposure and orientation of pulmonary surfactant protein SP-C in model surfactant membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1907-15. [DOI: 10.1016/j.bbamem.2009.05.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Revised: 04/24/2009] [Accepted: 05/07/2009] [Indexed: 01/08/2023]
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35
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Liu J, Conboy JC. Phase Behavior of Planar Supported Lipid Membranes Composed of Cholesterol and 1,2-Distearoyl-sn-Glycerol-3-Phosphocholine Examined by Sum-Frequency Vibrational Spectroscopy. VIBRATIONAL SPECTROSCOPY 2009; 50:106-115. [PMID: 20361007 PMCID: PMC2846528 DOI: 10.1016/j.vibspec.2008.09.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The influence of cholesterol (CHO) on the phase behavior of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) planar supported lipid bilayers (PSLBs) was investigated by sum-frequency vibrational spectroscopy (SFVS). The intrinsic symmetry constraints of SFVS were exploited to measure the asymmetric distribution of phase segregated phospholipid domains in the proximal and distal layers of DSPC + CHO binary mixtures as a function of CHO content and temperature. The SFVS results suggest that cholesterol significantly affects the phase segregation and domain distribution in PSLBs of DSPC in a concentration dependent manner, similar to that found in bulk suspensions. The SFVS spectroscopic measurements of phase segregation and structure change in the binary mixture indicate that membrane asymmetry must be present in order for the changes in SFVS signal to be observed. These results therefore provide important evidence for the delocalization and segregation of different phase domain structures in PSLBs due to the interaction of cholesterol and phospholipids.
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36
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Kailasam K, Natile MM, Glisenti A, Müller K. Fourier transform infrared spectroscopy and solid-state nuclear magnetic resonance studies of octadecyl modified metal oxides obtained from different silane precursors. J Chromatogr A 2009; 1216:2345-54. [DOI: 10.1016/j.chroma.2009.01.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2008] [Revised: 12/29/2008] [Accepted: 01/02/2009] [Indexed: 10/21/2022]
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37
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Coppock PS, Kindt JT. Atomistic simulations of mixed-lipid bilayers in gel and fluid phases. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:352-359. [PMID: 19032029 DOI: 10.1021/la802712q] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The slow rate of diffusive mixing poses a challenge for molecular dynamics (MD) simulation studies of mixed-lipid bilayers. A mixed Monte Carlo-molecular dynamics (MC-MD) approach, which uses mutation moves to swap lipid types throughout the system within the semi-grand canonical ensemble, is here applied to a comparison of binary mixtures in the gel and liquid crystalline phases. The two lipid components modeled, distearoylphosphatidylcholine (DSPC) and dimyristoylphosphatidylcholine (DMPC), differ by four carbons in the lengths of their acyl tails and are investigated here at full hydration at a temperature (313 K) between their transition temperatures, where coexistence between a DSPC-rich gel phase and a DMPC-rich liquid crystalline phase is expected. An analysis of DSPC-DMPC mixtures in the gel phase indicates strong deviation from ideality in the thermodynamics of mixing, accompanied by a tendency of the shorter-tailed component DMPC to associate laterally and for DMPC headgroups to be displaced toward the bilayer midplane. The liquid crystal phase mixtures, in contrast, show more mild deviation from thermodynamically ideal mixing with no apparent tendency for similar lipids to cluster laterally and no difference in headgroup normal distribution profiles.
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Affiliation(s)
- Patrick S Coppock
- Emory University, Department of Chemistry, 1515 Dickey Drive, Atlanta, Georgia 30322, USA
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38
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Ordering effects of cholesterol and its analogues. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:97-121. [DOI: 10.1016/j.bbamem.2008.08.022] [Citation(s) in RCA: 450] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Revised: 08/27/2008] [Accepted: 08/31/2008] [Indexed: 12/12/2022]
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39
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Högberg CJ, Nikitin AM, Lyubartsev AP. Modification of the CHARMM force field for DMPC lipid bilayer. J Comput Chem 2008; 29:2359-69. [PMID: 18512235 DOI: 10.1002/jcc.20974] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The CHARMM force field for DMPC lipids was modified in order to improve agreement with experiment for a number of important properties of hydrated lipid bilayer. The modification consists in introduction of a scaling factor 0.83 for 1-4 electrostatic interactions (between atoms separated by three covalent bonds), which provides correct transgauche ratio in the alkane tails, and recalculation of the headgroup charges on the basis of HF/6-311(d,p) ab-initio computations. Both rigid TIP3P and flexible SPC water models were used with the new lipid model, showing similar results. The new model in a 75 ns simulation has shown a correct value of the area per lipid at zero surface tension, as well as good agreement with the experiment for the electron density, structure factor, and order parameters, including those in the headgroup part of lipids.
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Affiliation(s)
- Carl-Johan Högberg
- Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, SE-10691, Sweden
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40
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Krishnamurty S, Stefanov M, Mineva T, Bégu S, Devoisselle JM, Goursot A, Zhu R, Salahub DR. Density Functional Theory-Based Conformational Analysis of a Phospholipid Molecule (Dimyristoyl Phosphatidylcholine). J Phys Chem B 2008; 112:13433-42. [DOI: 10.1021/jp804934d] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- S. Krishnamurty
- UMR 5253 CNRS/ENSCM/UM2/UM1, Institut Charles Gerhardt Montpellier, 8 rue de 1ʼ Ecole Normale, 34296 Montpellier Cédex 5, France, Institute of Catalysis, Bulgarian Academy of Sciences, Georgi Bonchev Strasse 11, 1113 Sofia, Bulgaria, and Department of Chemistry and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - M. Stefanov
- UMR 5253 CNRS/ENSCM/UM2/UM1, Institut Charles Gerhardt Montpellier, 8 rue de 1ʼ Ecole Normale, 34296 Montpellier Cédex 5, France, Institute of Catalysis, Bulgarian Academy of Sciences, Georgi Bonchev Strasse 11, 1113 Sofia, Bulgaria, and Department of Chemistry and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - T. Mineva
- UMR 5253 CNRS/ENSCM/UM2/UM1, Institut Charles Gerhardt Montpellier, 8 rue de 1ʼ Ecole Normale, 34296 Montpellier Cédex 5, France, Institute of Catalysis, Bulgarian Academy of Sciences, Georgi Bonchev Strasse 11, 1113 Sofia, Bulgaria, and Department of Chemistry and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - S. Bégu
- UMR 5253 CNRS/ENSCM/UM2/UM1, Institut Charles Gerhardt Montpellier, 8 rue de 1ʼ Ecole Normale, 34296 Montpellier Cédex 5, France, Institute of Catalysis, Bulgarian Academy of Sciences, Georgi Bonchev Strasse 11, 1113 Sofia, Bulgaria, and Department of Chemistry and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - J. M. Devoisselle
- UMR 5253 CNRS/ENSCM/UM2/UM1, Institut Charles Gerhardt Montpellier, 8 rue de 1ʼ Ecole Normale, 34296 Montpellier Cédex 5, France, Institute of Catalysis, Bulgarian Academy of Sciences, Georgi Bonchev Strasse 11, 1113 Sofia, Bulgaria, and Department of Chemistry and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - A. Goursot
- UMR 5253 CNRS/ENSCM/UM2/UM1, Institut Charles Gerhardt Montpellier, 8 rue de 1ʼ Ecole Normale, 34296 Montpellier Cédex 5, France, Institute of Catalysis, Bulgarian Academy of Sciences, Georgi Bonchev Strasse 11, 1113 Sofia, Bulgaria, and Department of Chemistry and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - R. Zhu
- UMR 5253 CNRS/ENSCM/UM2/UM1, Institut Charles Gerhardt Montpellier, 8 rue de 1ʼ Ecole Normale, 34296 Montpellier Cédex 5, France, Institute of Catalysis, Bulgarian Academy of Sciences, Georgi Bonchev Strasse 11, 1113 Sofia, Bulgaria, and Department of Chemistry and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - D. R. Salahub
- UMR 5253 CNRS/ENSCM/UM2/UM1, Institut Charles Gerhardt Montpellier, 8 rue de 1ʼ Ecole Normale, 34296 Montpellier Cédex 5, France, Institute of Catalysis, Bulgarian Academy of Sciences, Georgi Bonchev Strasse 11, 1113 Sofia, Bulgaria, and Department of Chemistry and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
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41
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Watanabe S, Noda I, Ozaki Y. Thermally induced conformational changes in polyethylene studied by two-dimensional near-infrared–infrared hetero-spectral correlation spectroscopy. J Mol Struct 2008. [DOI: 10.1016/j.molstruc.2008.01.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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42
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Cieślik-Boczula K, Czarnik-Matusewicz B, Perevozkina M, Filarowski A, Boens N, De Borggraeve WM, Koll A. ATR-IR spectroscopic study of the structural changes in the hydrophobic region of ICPAN/DPPC bilayers. J Mol Struct 2008. [DOI: 10.1016/j.molstruc.2007.08.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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43
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Kuligowski J, Quintás G, Esteve-Turrillas FA, Garrigues S, de la Guardia M. On-line gel permeation chromatography-attenuated total reflectance-Fourier transform infrared determination of lecithin and soybean oil in dietary supplements. J Chromatogr A 2008; 1185:71-7. [PMID: 18272158 DOI: 10.1016/j.chroma.2008.01.048] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2007] [Revised: 01/07/2008] [Accepted: 01/10/2008] [Indexed: 11/28/2022]
Abstract
Gel permeation chromatography (GPC) with attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrometry detection has been proposed for the simultaneous determination of lecithin and soybean oil in dietary supplements. The method involves the extraction of analytes with dichloromethane in an ultrasound water bath and the injection of 2 ml of centrifuged and filtered extracts into the system integrated by two Envirogel GPC columns (19 mm x150 mm, 19 mm x 300 mm) coupled on-line. Dichloromethane was used as mobile phase. A method has been developed to select the most appropriated wavenumber to be used for the determination of each considered compound from the calculation of a factor which maximizes the analyte signal minimizing the interferent contributions, being selected the detection wavenumbers of 1034 and 1138 cm(-1) for lecithin and soybean oil, respectively in the first order derivative ATR-FTIR spectra. The method provides limits of detection of 2 and 4 mg ml(-1) for lecithin and soybean oil and repeatability values, measured as relative standard deviation, of 2.5% and 3.4% being extended the linear range till 100 mg ml(-1) for lecithin and up to 50 mg ml(-1) for soybean oil. Accurate results were found for 10 synthetic samples and 7 commercial dietary supplement preparations.
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Affiliation(s)
- J Kuligowski
- Analytical Chemistry Department, Universitat de València, Edifici Jeroni Muñoz, 50th Dr. Moliner, Burjassot, Spain
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44
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Allouche M, Castano S, Colin D, Desbat B, Kerfelec B. Structure and Orientation of Pancreatic Colipase in a Lipid Environment: PM-IRRAS and Brewster Angle Microscopy Studies. Biochemistry 2007; 46:15188-97. [DOI: 10.1021/bi701831f] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Maya Allouche
- INSERM, U476 “Nutrition Humaine et Lipides”, Marseille, F-13385 France, INRA, UMR1260, Marseille, F-13385 France, Université Méditerranée Aix-Marseille 2, Faculté de Médecine, IPHM-IFR 125, Marseille, F-13385 France, and CBMN, UMR5248, CNRS, Université Bordeaux I, ENITAB, 2, rue Robert Escarpit, 33607 Pessac, France
| | - Sabine Castano
- INSERM, U476 “Nutrition Humaine et Lipides”, Marseille, F-13385 France, INRA, UMR1260, Marseille, F-13385 France, Université Méditerranée Aix-Marseille 2, Faculté de Médecine, IPHM-IFR 125, Marseille, F-13385 France, and CBMN, UMR5248, CNRS, Université Bordeaux I, ENITAB, 2, rue Robert Escarpit, 33607 Pessac, France
| | - Damien Colin
- INSERM, U476 “Nutrition Humaine et Lipides”, Marseille, F-13385 France, INRA, UMR1260, Marseille, F-13385 France, Université Méditerranée Aix-Marseille 2, Faculté de Médecine, IPHM-IFR 125, Marseille, F-13385 France, and CBMN, UMR5248, CNRS, Université Bordeaux I, ENITAB, 2, rue Robert Escarpit, 33607 Pessac, France
| | - Bernard Desbat
- INSERM, U476 “Nutrition Humaine et Lipides”, Marseille, F-13385 France, INRA, UMR1260, Marseille, F-13385 France, Université Méditerranée Aix-Marseille 2, Faculté de Médecine, IPHM-IFR 125, Marseille, F-13385 France, and CBMN, UMR5248, CNRS, Université Bordeaux I, ENITAB, 2, rue Robert Escarpit, 33607 Pessac, France
| | - Brigitte Kerfelec
- INSERM, U476 “Nutrition Humaine et Lipides”, Marseille, F-13385 France, INRA, UMR1260, Marseille, F-13385 France, Université Méditerranée Aix-Marseille 2, Faculté de Médecine, IPHM-IFR 125, Marseille, F-13385 France, and CBMN, UMR5248, CNRS, Université Bordeaux I, ENITAB, 2, rue Robert Escarpit, 33607 Pessac, France
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45
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Denisov IG, McLean MA, Shaw AW, Grinkova YV, Sligar SG. Thermotropic phase transition in soluble nanoscale lipid bilayers. J Phys Chem B 2007; 109:15580-8. [PMID: 16852976 PMCID: PMC2518645 DOI: 10.1021/jp051385g] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The role of lipid domain size and protein-lipid interfaces in the thermotropic phase transition of dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) bilayers in Nanodiscs was studied using small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and generalized polarization (GP) of the lipophilic probe Laurdan. Nanodiscs are water-soluble, monodisperse, self-assembled lipid bilayers encompassed by a helical membrane scaffold protein (MSP). MSPs of different lengths were used to define the diameter of the Nanodisc lipid bilayer from 76 to 108 A and the number of DPPC molecules from 164 to 335 per discoidal structure. In Nanodiscs of all sizes, the phase transitions were broader and shifted to higher temperatures relative to those observed in vesicle preparations. The size dependences of the transition enthalpies and structural parameters of Nanodiscs reveal the presence of a boundary lipid layer in contact with the scaffold protein encircling the perimeter of the disc. The thickness of this annular layer was estimated to be approximately 15 A, or two lipid molecules. SAXS was used to measure the lateral thermal expansion of Nanodiscs, and a steep decrease of bilayer thickness during the main lipid phase transition was observed. These results provide the basis for the quantitative understanding of cooperative phase transitions in membrane bilayers in confined geometries at the nanoscale.
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Affiliation(s)
- Ilia G Denisov
- Departments of Biochemistry and Chemistry, College of Medicine, and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 505 South Goodwin Avenue, Urbana, Illinois 61801, USA
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46
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Subramanian S, Sampath S. Enhanced stability of short- and long-chain diselenide self-assembled monolayers on gold probed by electrochemistry, spectroscopy, and microscopy. J Colloid Interface Sci 2007; 312:413-24. [PMID: 17451727 DOI: 10.1016/j.jcis.2007.03.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 03/10/2007] [Accepted: 03/12/2007] [Indexed: 11/16/2022]
Abstract
Well-ordered, compact, self-assembled monolayers (SAMs) of hexyl and dodecyl diselenides have been formed on oriented (111) gold surfaces. Monolayer formation has been effected by adsorption from neat diselenides as well as millimolar solutions of diselenides in alcohol. The monolayer formation is confirmed using electrochemical quartz crystal microbalance studies. The stability and permeability of the monolayers at various temperatures have been probed using reflection absorption infrared spectroscopy (RAIRS) and electrochemistry. The RAIRS studies in the dry state show the formation of highly ordered, compact structures when adsorbed from neat compounds compared to the monolayers adsorbed in the presence of alcohol. The monolayers adsorbed from neat diselenide are quite stable as a function of temperature irrespective of the chain length. The electrochemical studies based on the blocking behavior of the monolayers toward electron transfer between a diffusing species and the electrode surface reflect the stability and the compactness of the structure. The results point out that the presence of solvent molecules during the SAM formation hinders the organization of the monolayer structure, especially in the case of short-chain diselenide monolayers.
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Affiliation(s)
- S Subramanian
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India
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47
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Meier RJ, Csiszár A, Klumpp E. On the interpretation of the 1100 cm(-1) Raman band in phospholipids and other alkyl-containing molecular entities. J Phys Chem B 2007; 110:5842-4. [PMID: 16553388 DOI: 10.1021/jp060420w] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The long-standing issue on the interpretation of a Raman band at 1100 cm(-1) is discussed. By combining observations from studies on lipid bilayers, alkanes, and polyethylenes, one can now definitely assign this band to the presence of isolated gauche bonds. In addition, we discuss the use of an order parameter S(trans) in lipid bilayer structures.
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48
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Kailasam K, Srinivasan G, Müller K. Solvents effects on the conformational order of triacontyl modified silica gels as evaluated by Fourier transform infrared spectroscopy. J Chromatogr A 2006; 1134:81-7. [PMID: 16965784 DOI: 10.1016/j.chroma.2006.08.062] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 08/15/2006] [Accepted: 08/21/2006] [Indexed: 11/26/2022]
Abstract
C30 alkyl modified silica gels have attracted much attention because of their enhanced shape selectivity for various types of analytes, which for instance cannot be separated with conventional C8 and C18 stationary phases. Since the retention processes strongly depend on the nature of solvents and composition of the stationary phases, a FTIR study was conducted to evaluate the influence of solvents on the conformational order of the alkyl chains in C30 alkyl modified silica gels. Variable temperature IR measurements are carried out between 273 and 353 K in the presence of polar and nonpolar solvents. Information about the conformational behavior of the tethered alkyl chains is derived from the analysis of the symmetric and antisymmetric CH2 stretching band regions. Polar solvents show both enhanced conformational order and disorder of the alkyl chains - irrespective of temperature - when compared to dry C30 alkyl modified silica gels, while nonpolar solvents in general give rise to enhanced conformational disorder in the alkyl chain region. Moreover, for polar solvents a correlation exists between the stretching band position, reflecting alkyl chain conformational order, and the solvent solvatochromic parameter pi*. Finally, both partition and adsorption models are considered to play an important role for the solvent-alkyl chain interactions which in turn determines the conformational order of the alkyl chains and thus the chromatographic properties of these phases.
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Affiliation(s)
- Kamalakannan Kailasam
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
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49
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Nicolini C, Kraineva J, Khurana M, Periasamy N, Funari SS, Winter R. Temperature and pressure effects on structural and conformational properties of POPC/SM/cholesterol model raft mixtures--a FT-IR, SAXS, DSC, PPC and Laurdan fluorescence spectroscopy study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:248-58. [PMID: 16529710 DOI: 10.1016/j.bbamem.2006.01.019] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 01/24/2006] [Accepted: 01/26/2006] [Indexed: 11/17/2022]
Abstract
We report on the effects of temperature and pressure on the structure, conformation and phase behavior of aqueous dispersions of the model lipid "raft" mixture palmitoyloleoylphosphatidylcholine (POPC)/bovine brain sphingomyelin (SM)/cholesterol (Chol) (1:1:1). We investigated interchain interactions, hydrogen bonding, conformational and structural properties as well as phase transformations of this system using Fourier transform-infrared (FT-IR) spectroscopy, small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC) coupled with pressure perturbation calorimetry (PPC), and Laurdan fluorescence spectroscopy. The IR spectral parameters in combination with the scattering patterns from the SAXS measurements were used to detect structural and conformational transformations upon changes of pressure up to 7-9 kbar and temperature in the range from 1 to about 80 degrees C. The generalized polarization function (GP) values, obtained from the Laurdan fluorescence spectroscopy studies also reveal temperature and pressure dependent phase changes. DSC and PPC were used to detect thermodynamic properties accompanying the temperature-dependent phase changes. In combination with literature fluorescence spectroscopy and microscopy data, a tentative p,T stability diagram of the mixture has been established. The data reveal a broad liquid-order/solid-ordered (lo+so) two-phase coexistence region below 8+/-2 degrees C at ambient pressure. With increasing temperature, a lo+ld+so three-phase region is formed, which extends up to approximately 27 degrees C, where a liquid-ordered/liquid-disordered (lo+ld) immiscibility region is formed. Finally, above 48+/-2 degrees C, the POPC/SM/Chol (1:1:1) mixture becomes completely fluid-like (liquid-disordered, ld). With increasing pressure, all phase transition lines shift to higher temperatures. Notably, the lo+ld (+so) phase coexistence region, mimicking raft-like lateral phase separation in natural membranes, extends over a rather wide temperature range of about 40 degrees C, and a pressure range, which extends up to about 2 kbar for T=37 degrees C. Interestingly, in this pressure range, ceasing of membrane protein function in natural membrane environments has been observed for a variety of systems.
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Affiliation(s)
- Chiara Nicolini
- University of Dortmund, Department of Chemistry, Physical Chemistry I-Biophysical Chemistry, Otto-Hahn-Strasse 6, D-44227 Dortmund, Germany
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50
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Srinivasan G, Sander LC, Müller K. Effect of surface coverage on the conformation and mobility of C18-modified silica gels. Anal Bioanal Chem 2005; 384:514-24. [PMID: 16315015 DOI: 10.1007/s00216-005-0161-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2005] [Revised: 09/29/2005] [Accepted: 09/29/2005] [Indexed: 11/26/2022]
Abstract
C18-modified silica gels with surface coverages of 2 to 8.2 micromol m(-2), were prepared by different synthetic pathways and characterized by Fourier Transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance (NMR) spectroscopy, and chromatographic measurements. The effects of temperature and bonding density on the conformational order of C18-modified silica gels were studied in detail by FTIR spectroscopy. The silane functionality and degree of cross-linking of silane ligands on the silica surface were evaluated by 29Si cross-polarization magic-angle spinning (CP/MAS) NMR and the structural order and mobility of the alkyl chains were investigated by 13C CP/MAS NMR spectroscopy. CH2 symmetric and anti-symmetric stretching bands and CH2 wagging bands were used as IR probes to monitor the conformational order and flexibility of the alkyl chains in the C18 phases. Qualitative information about the conformational order was obtained from frequency shifts of the CH2 symmetric and anti-symmetric stretching bands. The relative amounts of kink/gauche-trans-gauche, double-gauche, and end-gauche conformers in the alkyl chains were determined by analysis of CH2 wagging bands. These results indicate that surface coverage plays a dominant role in the conformational order of C18-modified silica gels. The FTIR and NMR data are discussed in the context of the chromatographic shape-selectivity differences.
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Affiliation(s)
- Gokulakrishnan Srinivasan
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
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