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Lo KKW. Molecular Design of Bioorthogonal Probes and Imaging Reagents Derived from Photofunctional Transition Metal Complexes. Acc Chem Res 2020; 53:32-44. [PMID: 31916746 DOI: 10.1021/acs.accounts.9b00416] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
For more than 15 years, bioorthogonal chemistry has received increasing attention due to its successful applications in the detection and imaging of biomolecules in their native biological environments. The method typically proceeds with the incorporation of a biological substrate appended with a bioorthogonal functional group (chemical reporter), followed by the introduction of the substrate to biological systems. Biomolecules containing the substrate are then recognized by an exogenously delivered bioorthogonal probe. Despite the fact that many useful chemical reporters and bioorthogonal reactions have been developed, most of the bioorthogonal probes reported thus far are fluorescent dyes. A limitation is that stringent washing is required due to the interference caused by the background fluorescence of unreacted probes. Thus, fluorogenic probes with turn-on emission properties upon bioorthogonal labeling have been designed as an alternative strategy. These probes are highly appealing because excellent images can be obtained without the need for washing steps. Nearly all fluorogenic bioorthogonal probes designed are essentially organic dyes, their emission is limited to fluorescence, and the utilization of the probes is confined to bioimaging applications. Recently, there has been a growing interest in the bioimaging and therapeutic applications of luminescent inorganic and organometallic transition metal complexes due to their intriguing photophysical and photochemical properties, high membrane permeability, controllable cellular uptake, intracellular localization, and cytotoxicity. We anticipate that photofunctional transition metal complexes can be exploited as valuable bioorthogonal probes due to these appealing advantages. In this Account, we introduce the molecular design, photophysical and photochemical properties, and biological applications of various bioorthogonal probes and imaging reagents based on photofunctional transition metal complexes. The presence of a cationic metal center significantly enhances the bioorthogonal reactivity of the probes, yet their stability in aqueous solutions can be maintained. Interestingly, some of these metal complexes are strategically modified to display phosphorogenic properties, that is, phosphorescence turn-on upon bioorthogonal labeling reactions. Importantly, these probes not only exhibit favorable photophysical properties after bioorthogonal labeling, but also efficient photoinduced singlet oxygen (1O2) generation. This interesting bioorthogonal reaction-triggered photosensitization capability allows the modulation of 1O2 generation efficiency and contributes to the development of controllable photocytotoxic agents. The exploration of transition metal complex-based probes not only significantly widens the scope of bioorthogonal labeling but also further highlights the unique advantages of these complexes in the design of theranostic reagents. The development of these innovative reagents is expected to contribute to the basic understanding of biological processes in living systems and provide exciting opportunities for new diagnostic and therapeutic applications.
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Affiliation(s)
- Kenneth Kam-Wing Lo
- Department of Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, P. R. China
- State Key Laboratory of Terahertz and Millimeter Waves, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, P. R. China
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Kataoka M, Ohi Y, Sakanoue K, Minami K, Higashino H, Yamashita S. Impact of Dietary Intake of Medium-Chain Triacylglycerides on the Intestinal Absorption of Poorly Permeable Compounds. Mol Pharm 2019; 17:212-218. [DOI: 10.1021/acs.molpharmaceut.9b00900] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Makoto Kataoka
- Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-Cho, Hirakata, Osaka 573-0101, Japan
| | - Yuriko Ohi
- Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-Cho, Hirakata, Osaka 573-0101, Japan
| | - Kana Sakanoue
- Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-Cho, Hirakata, Osaka 573-0101, Japan
| | - Keiko Minami
- Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-Cho, Hirakata, Osaka 573-0101, Japan
| | - Haruki Higashino
- Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-Cho, Hirakata, Osaka 573-0101, Japan
| | - Shinji Yamashita
- Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-Cho, Hirakata, Osaka 573-0101, Japan
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Yip AMH, Lo KKW. Luminescent rhenium(I), ruthenium(II), and iridium(III) polypyridine complexes containing a poly(ethylene glycol) pendant or bioorthogonal reaction group as biological probes and photocytotoxic agents. Coord Chem Rev 2018. [DOI: 10.1016/j.ccr.2018.01.021] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Effects of Chain Length and Saturability of Fatty Acids on Phospholipids and Proteins in Plasma Membranes of Bovine Mammary Gland. J Membr Biol 2016; 249:743-756. [DOI: 10.1007/s00232-016-9919-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Accepted: 07/16/2016] [Indexed: 10/21/2022]
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Schönfeld P, Wojtczak L. Short- and medium-chain fatty acids in energy metabolism: the cellular perspective. J Lipid Res 2016; 57:943-54. [PMID: 27080715 DOI: 10.1194/jlr.r067629] [Citation(s) in RCA: 585] [Impact Index Per Article: 73.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Indexed: 12/12/2022] Open
Abstract
Short- and medium-chain fatty acids (SCFAs and MCFAs), independently of their cellular signaling functions, are important substrates of the energy metabolism and anabolic processes in mammals. SCFAs are mostly generated by colonic bacteria and are predominantly metabolized by enterocytes and liver, whereas MCFAs arise mostly from dietary triglycerides, among them milk and dairy products. A common feature of SCFAs and MCFAs is their carnitine-independent uptake and intramitochondrial activation to acyl-CoA thioesters. Contrary to long-chain fatty acids, the cellular metabolism of SCFAs and MCFAs depends to a lesser extent on fatty acid-binding proteins. SCFAs and MCFAs modulate tissue metabolism of carbohydrates and lipids, as manifested by a mostly inhibitory effect on glycolysis and stimulation of lipogenesis or gluconeogenesis. SCFAs and MCFAs exert no or only weak protonophoric and lytic activities in mitochondria and do not significantly impair the electron transport in the respiratory chain. SCFAs and MCFAs modulate mitochondrial energy production by two mechanisms: they provide reducing equivalents to the respiratory chain and partly decrease efficacy of oxidative ATP synthesis.
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Affiliation(s)
- Peter Schönfeld
- Institute of Biochemistry and Cell Biology, Otto-von-Guericke University, Magdeburg, 39120 Magdeburg, Germany
| | - Lech Wojtczak
- Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland
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Meadows KE, Nadappuram BP, Unwin PR. A new approach for the fabrication of microscale lipid bilayers at glass pipets: application to quantitative passive permeation visualization. SOFT MATTER 2014; 10:8433-8441. [PMID: 25221789 DOI: 10.1039/c3sm51406d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A new method of planar bilayer lipid membrane (BLM) formation is presented that allows stable, solvent-free lipid bilayers exhibiting high seal resistances to be formed rapidly, easily and reproducibly. Using these bilayers the passive permeation of a series of carboxylic acids is investigated, to determine quantitatively the trend in permeability with lipophilicity of the acid. BLMs are formed at the tip openings of pulled theta pipets, and the rate of permeation of each carboxylic acid across the bilayer, from within the pipet into the bulk solution is determined. This is achieved through spatially-resolved measurements of the pH change that occurs upon the permeation of the weak acid, visualized using a pH-sensitive fluorophore with a confocal laser scanning microscope. The extracted fluorescence profiles are matched to finite element method (FEM) simulations, to allow the associated permeation coefficient for each weak acid to be determined with high accuracy, since this is the only adjustable parameter used to fit the experimental data. For bilayers formed in this way, the weak acids show increasing permeability with lipophilicity. Furthermore, the arrangement allows the effect of a trans-membrane electric field on permeation to be explored. For both propanoic and hexanoic acid it is found that an applied electric field enhances molecular transport, which is attributed to the formation of pores within the membrane.
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Running CA, Mattes RD. Different oral sensitivities to and sensations of short-, medium-, and long-chain fatty acids in humans. Am J Physiol Gastrointest Liver Physiol 2014; 307:G381-9. [PMID: 24924750 DOI: 10.1152/ajpgi.00181.2014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Fatty acids that vary in chain length and degree of unsaturation have different effects on metabolism and human health. As evidence for a "taste" of nonesterified fatty acids (NEFA) accumulates, it may be hypothesized that fatty acid structures will also influence oral sensations. The present study examined oral sensitivity to caproic (C6), lauric (C12), and oleic (C18:1) acids over repeated visits. Analyses were also conducted on textural properties of NEFA emulsions and blank solutions. Oral thresholds for caproic acid were lower compared with oleic acid. Lauric acid thresholds were intermediate but not significantly different from either, likely due to lingering irritating sensations that prevented accurate discrimination. From particle size analysis, larger droplets were observed in blank solutions when mineral oil was used, leading to instability of the emulsion, which was not observed when emulsions contained NEFA or when mineral oil was removed from the blank. Rheological data showed no differences in viscosity among samples except for a slightly higher viscosity with oleic acid concentrations above 58 mM. Thus, texture was unlikely to be the property used to distinguish between the samples. Differences in oral detection and sensation of caproic, lauric, and oleic acids may be due to different properties of the fatty acid alkyl chains.
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Affiliation(s)
- Cordelia A Running
- Department of Food Science, Purdue University, West Lafayette, Indiana; and
| | - Richard D Mattes
- Department of Nutrition Science, Purdue University, West Lafayette, Indiana
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Tucker RM, Mattes RD, Running CA. Mechanisms and effects of "fat taste" in humans. Biofactors 2014; 40:313-26. [PMID: 24591077 DOI: 10.1002/biof.1162] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 02/18/2014] [Indexed: 12/11/2022]
Abstract
Evidence supporting a "taste" cue from fat in the oral cavity continues to accrue. The proposed stimuli for fat taste, non-esterified fatty acids (NEFA), are released from food through hydrolytic rancidity and lipase activity derived from foods or saliva. NEFA must then be released from the food matrix, negotiate the aqueous environment to reach taste cell surfaces, and interact with receptors such as CD36 and GPR120 or diffuse across cell membranes to initiate a taste signal. Knowledge of these processes in non-gustatory tissues should inform understanding of taste responses to NEFA. Additionally, downstream effects of oral triglyceride exposure have been observed in numerous studies. Data specific to effects of NEFA versus triglyceride are scarce, but modified sham feeding trials with triglyceride document cephalic phase responses including elevations in serum lipids and insulin as well as potential, but debated, effects on gut peptides, appetite, and thermogenesis. In this review, we highlight the mechanisms by which NEFA migrate to and interact with taste cells, and then we examine physiological responses to oral fat exposure.
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Affiliation(s)
- Robin M Tucker
- Department of Nutrition Science, Purdue University, West Lafayette, IN, USA
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Royce LA, Boggess E, Fu Y, Liu P, Shanks JV, Dickerson J, Jarboe LR. Transcriptomic analysis of carboxylic acid challenge in Escherichia coli: beyond membrane damage. PLoS One 2014; 9:e89580. [PMID: 24586888 PMCID: PMC3938484 DOI: 10.1371/journal.pone.0089580] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 01/21/2014] [Indexed: 11/18/2022] Open
Abstract
Carboxylic acids are an attractive biorenewable chemical. Enormous progress has been made in engineering microbes for production of these compounds though titers remain lower than desired. Here we used transcriptome analysis of Escherichia coli during exogenous challenge with octanoic acid (C8) at pH 7.0 to probe mechanisms of toxicity. This analysis highlights the intracellular acidification and membrane damage caused by C8 challenge. Network component analysis identified transcription factors with altered activity including GadE, the activator of the glutamate-dependent acid resistance system (AR2) and Lrp, the amino acid biosynthesis regulator. The intracellular acidification was quantified during exogenous challenge, but was not observed in a carboxylic acid producing strain, though this may be due to lower titers than those used in our exogenous challenge studies. We developed a framework for predicting the proton motive force during adaptation to strong inorganic acids and carboxylic acids. This model predicts that inorganic acid challenge is mitigated by cation accumulation, but that carboxylic acid challenge inverts the proton motive force and requires anion accumulation. Utilization of native acid resistance systems was not useful in terms of supporting growth or alleviating intracellular acidification. AR2 was found to be non-functional, possibly due to membrane damage. We proposed that interaction of Lrp and C8 resulted in repression of amino acid biosynthesis. However, this hypothesis was not supported by perturbation of lrp expression or amino acid supplementation. E. coli strains were also engineered for altered cyclopropane fatty acid content in the membrane, which had a dramatic effect on membrane properties, though C8 tolerance was not increased. We conclude that achieving higher production titers requires circumventing the membrane damage. As higher titers are achieved, acidification may become problematic.
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Affiliation(s)
- Liam A. Royce
- Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa, United States of America
| | - Erin Boggess
- Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa, United States of America
| | - Yao Fu
- Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa, United States of America
| | - Ping Liu
- Interdepartmental Microbiology Program, Iowa State University, Ames, Iowa, United States of America
| | - Jacqueline V. Shanks
- Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa, United States of America
| | - Julie Dickerson
- Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa, United States of America
| | - Laura R. Jarboe
- Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa, United States of America
- Interdepartmental Microbiology Program, Iowa State University, Ames, Iowa, United States of America
- * E-mail:
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Jarboe LR, Royce LA, Liu P. Understanding biocatalyst inhibition by carboxylic acids. Front Microbiol 2013; 4:272. [PMID: 24027566 PMCID: PMC3760142 DOI: 10.3389/fmicb.2013.00272] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 08/20/2013] [Indexed: 11/13/2022] Open
Abstract
Carboxylic acids are an attractive biorenewable chemical in terms of their flexibility and usage as precursors for a variety of industrial chemicals. It has been demonstrated that such carboxylic acids can be fermentatively produced using engineered microbes, such as Escherichia coli and Saccharomyces cerevisiae. However, like many other attractive biorenewable fuels and chemicals, carboxylic acids become inhibitory to these microbes at concentrations below the desired yield and titer. In fact, their potency as microbial inhibitors is highlighted by the fact that many of these carboxylic acids are routinely used as food preservatives. This review highlights the current knowledge regarding the impact that saturated, straight-chain carboxylic acids, such as hexanoic, octanoic, decanoic, and lauric acids can have on E. coli and S. cerevisiae, with the goal of identifying metabolic engineering strategies to increase robustness. Key effects of these carboxylic acids include damage to the cell membrane and a decrease of the microbial internal pH. Certain changes in cell membrane properties, such as composition, fluidity, integrity, and hydrophobicity, and intracellular pH are often associated with increased tolerance. The availability of appropriate exporters, such as Pdr12, can also increase tolerance. The effect on metabolic processes, such as maintaining appropriate respiratory function, regulation of Lrp activity and inhibition of production of key metabolites such as methionine, are also considered. Understanding the mechanisms of biocatalyst inhibition by these desirable products can aid in the engineering of robust strains with improved industrial performance.
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Affiliation(s)
- Laura R Jarboe
- Department of Chemical and Biological Engineering, Iowa State University Ames, IA, USA ; Department of Microbiology, Iowa State University Ames, IA, USA
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MAISHI NAKO, KAWAMOTO TAISUKE, OHGA NORITAKA, YAMADA KOJI, AKIYAMA KOSUKE, YAMAMOTO KAZUYUKI, OSAWA TAKAHIRO, HIDA YASUHIRO, HIDA KYOKO. Application of POLARIC™ fluorophores in an in vivo tumor model. Oncol Rep 2013; 30:1695-700. [DOI: 10.3892/or.2013.2620] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 06/21/2013] [Indexed: 11/06/2022] Open
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12
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The use of mammalian cultured cells loaded with a fluorescent dye shows specific membrane penetration of undissociated acetic acid. Biosci Biotechnol Biochem 2012; 76:523-9. [PMID: 22451395 DOI: 10.1271/bbb.110824] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Acetic acid induces unique physiological responses in mammalian cells. Our previous study found that fura-2-loaded human embryonic kidney (HEK) 293T cells showed a robust intracellular fluorescence response immediately after stimulation with acetic acid, and no such response in the case of citric acid. In the present study, we aimed to identify the unique characteristics of acetic acid responsible for this phenomenon. We found that one such feature is its hydrophobicity. We also discovered that acetic acid induces cell responses by intracellular acidification. Of the components of acetic acid in solution (protons, acetate ions, and undissociated acetic acid), undissociated acetic acid might be the functional unit that penetrates the lipid bilayer of cell membranes to acidify the intracellular environment, thereby inducing cell responses. The method used in this study might be convenient in evaluating the intracellular acidification of cultured cells by acids in the external environment.
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Li S, Hu PC, Malmstadt N. Imaging molecular transport across lipid bilayers. Biophys J 2011; 101:700-8. [PMID: 21806938 DOI: 10.1016/j.bpj.2011.06.044] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 06/21/2011] [Accepted: 06/24/2011] [Indexed: 11/25/2022] Open
Abstract
Low-molecular-weight carboxylic acids have many properties common to small molecule drugs. The transport of these acids across cell membranes has been widely studied, but these studies have produced wildly varying permeability values. Recent reports have even claimed that the transport behavior of these drugs is contrary to the rule of thumb called Overton's rule, which holds that more lipophilic molecules transport across lipid membranes more quickly. We used confocal microscopy to image the transport of carboxylic acids with different lipophilicities into a giant unilamellar lipid vesicle (GUV). Fluorescein-dextran, which acts as a pH-sensitive dye, was encapsulated in the GUV to trace the transport of acid. The GUV was immobilized on the surface of a microfluidic channel by biotin-avidin binding. This microchannel allows the rapid and uniform exchange of the solution surrounding the GUV. Using a spinning-disk confocal microscope, the entire concentration field is captured in a short (<100 ms) exposure. Results show that more lipophilic acids cross the bilayer more quickly. A finite difference model was developed to simulate the experimental process and derive permeabilities. The permeabilities change with the same trend as literature oil-water partition coefficients, demonstrating that Overton's rule applies to this class of molecules.
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Affiliation(s)
- Su Li
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California, USA
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Kotova EA, Kuzevanov AV, Pashkovskaya AA, Antonenko YN. Selective permeabilization of lipid membranes by photodynamic action via formation of hydrophobic defects or pre-pores. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2252-7. [PMID: 21663731 DOI: 10.1016/j.bbamem.2011.05.018] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 04/19/2011] [Accepted: 05/23/2011] [Indexed: 01/09/2023]
Abstract
To gain insight into mechanisms of photodynamic modification of biological membranes, we studied an impact of visible light in combination with a photosensitizer on translocation of various substances across artificial (vesicular and planar) bilayer lipid membranes (BLMs). Along with induction of carboxyfluorescein leakage from liposomes, pronounced stimulation of lipid flip-flop between the two monolayers was found after photosensitization, both processes being prevented by the singlet oxygen quencher sodium azide. On the contrary, no enhancement of potassium chloride efflux from liposomes was detected by conductometry under these conditions. Illumination of planar BLMs in the presence of a photosensitizer led to a marked increase in membrane permeability to amphiphilic 2-n-octylmalonic acid, but practically no change in the permeability to ammonia, which agreed with selective character of the photosensitized leakage of fluorescent dyes from liposomes (Pashkovskaya et al., Langmuir, 2010). Thus, the effect on transbilayer movement of molecules elicited by the photodynamic treatment substantially depended on the kind of translocated species, in particular, on their lipophilicity. Based on similarity with results of previous electroporation studies, we hypothesized about photodynamic induction of "pre-pores" or "hydrophobic defects" permeable to amphiphilic compounds and less permeable to hydrophilic substances and inorganic ions.
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Affiliation(s)
- Elena A Kotova
- Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119991, Russia
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Quantitative visualization of passive transport across bilayer lipid membranes. Proc Natl Acad Sci U S A 2008; 105:14277-82. [PMID: 18787114 DOI: 10.1073/pnas.0803720105] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The ability to predict and interpret membrane permeation coefficients is of critical importance, particularly because passive transport is crucial for the effective delivery of many pharmaceutical agents to intracellular targets. We present a method for the quantitative measurement of the permeation coefficients of protonophores by using laser confocal scanning microscopy coupled to microelectrochemistry, which is amenable to precise modeling with the finite element method. The technique delivers well defined and high mass transport rates and allows rapid visualization of the entire pH distribution on both the cis and trans side of model bilayer lipid membranes (BLMs). A homologous series of carboxylic acids was investigated as probe molecules for BLMs composed of soybean phosphatidylcholine. Significantly, the permeation coefficient decreased with acyl tail length contrary to previous work and to Overton's rule. The reasons for this difference are considered, and we suggest that the applicability of Overton's rule requires re-evaluation.
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Pohl EE, Voltchenko AM, Rupprecht A. Flip-flop of hydroxy fatty acids across the membrane as monitored by proton-sensitive microelectrodes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1292-7. [PMID: 18313391 DOI: 10.1016/j.bbamem.2008.01.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2007] [Revised: 01/06/2008] [Accepted: 01/31/2008] [Indexed: 10/22/2022]
Abstract
Hydroxyl group-containing fatty acids play an important role in anti-inflammatory action, neuroprotection, bactericide and anti-cancer defense. However, the mechanism of long-chain hydroxy fatty acids (HFA) transport across plasma membranes is still disputed. Two main hypotheses have been suggested: firstly, that protonated HFAs traverse across the membranes spontaneously and, secondly, that the transport is facilitated by proteinaceous carriers. Here, we demonstrate that the protonated HFA are able to move across planar lipid bilayers without protein assistance. This transport step is accompanied by the acidification of the buffer in receiving compartment and the pH augmentation in the donating compartment. The latter contained liposomes doped with HFA. As revealed by scanning pH-sensitive microelectrodes, the pH shift occurred only in the immediate vicinity of the membrane, while bulk pH remained unchanged. In concurrence with the theoretical model of weak acid transport, the pH value at maximum proton flux was almost equal to the pK of the studied HFA. Intrinsic pKi values were calculated from the electrophoretic mobilities of HFA-containing liposomes and were 5.4, 6.5, 6.9 and 6.3 for 2-hydroxyhexadecanoic, 16-hydroxyhexadecanoic, 12-hydroxydodecanoic and 9,10,16-trihydroxyhexadecanoic acids, respectively.
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Affiliation(s)
- Elena E Pohl
- Institute of Cell Biology and Neurobiology, Charité-Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany.
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WILLIAMS CG, MACPHERSON JV, UNWIN PR, PARKINSON C. Laser Scanning Confocal Microscopy Coupled with Hydraulic Permeability Measurements for Elucidating Fluid Flow across Porous Materials: Application to Human Dentine. ANAL SCI 2008; 24:437-42. [DOI: 10.2116/analsci.24.437] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Kamp F, Hamilton JA. How fatty acids of different chain length enter and leave cells by free diffusion. Prostaglandins Leukot Essent Fatty Acids 2006; 75:149-59. [PMID: 16829065 DOI: 10.1016/j.plefa.2006.05.003] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Opposing views exist as to how unesterified fatty acids (FA) enter and leave cells. It is commonly believed that for short- and medium-chain FA free diffusion suffices whereas it is questioned whether proteins are required to facilitate transport of long-chain fatty acid (LCFA). Furthermore, it is unclear whether these proteins facilitate binding to the plasma membrane, trans-membrane movement, dissociation into the cytosol and/or transport in the cytosol. In this mini-review we approach the controversy from a different point of view by focusing on the membrane permeability constant (P) of FA with different chain length. We compare experimentally derived values of the P of short and medium-chain FA with values of apparent permeability coefficients for LCFA calculated from their dissociation rate constant (k(off)), flip-flop rate constant (k(flip)) and partition coefficient (Kp) in phospholipid bilayers. It was found that Overton's rule is valid as long as k(flip)<<k(off). With increasing chain length, the permeability increases according to increasing Kp and reaches a maximum for LCFA with chain length of 18 carbons or longer. For fast flip-flop (e.g. k(flip)=15s(-1)), the apparent permeability constant for palmitic acid is very high (P(app)=1.61 cm/s). Even for a slow flip-flop rate constant (e.g. k(flip)=0.3s(-1)), the permeability constant of LCFA is still several orders of magnitude larger than the P of water and other small non-electrolytes. Since polyunsaturated FA have basically the same physico-chemical properties as LCFA, they have similar membrane permeabilities. The implications for theories involving proteins to facilitate uptake of FA are discussed.
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Affiliation(s)
- Frits Kamp
- Laboratory of Alzheimer's and Parkinson's Disease Research, Institute of Metabolic Biochemistry, Ludwig-Maximilians-University, Schillerstrasse 44, D-80336 Munich, Germany.
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Erukova VY, Krylova OO, Antonenko YN, Melik-Nubarov NS. Effect of ethylene oxide and propylene oxide block copolymers on the permeability of bilayer lipid membranes to small solutes including doxorubicin. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1468:73-86. [PMID: 11018653 DOI: 10.1016/s0005-2736(00)00244-3] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The effects of ethylene oxide and propylene oxide block copolymers (pluronics) on the permeability of several weak acids and bases through bilayer lipid membranes have been studied by the methods of monitoring (1) pH shifts near planar bilayers, (2) doxorubicin fluorescence quenching inside liposomes, and (3) current transients in the presence of hydrophobic anions. It has been shown that pluronics facilitate the permeation of comparatively large molecules (such as 2-n-undecylmalonic acid and doxorubicin) across lipid bilayers, while the permeation of small solutes (such as ammonium and acetic acid) remains unaffected. Pluronics also accelerate the translocation of large hydrophobic anions (tetraphenylborate). The effect of pluronics correlates with the content of propylene oxide units: it is enhanced when the portion of polypropylene oxide block in the copolymer is increased. The action of the pluronic on lipid membrane permeability differs from the effect of the conventional detergent Triton X-100, which does not affect doxorubicin transport if added at concentrations similar to those used for pluronics. It has been proposed that pluronics accelerate the processes of solute diffusion within lipid bilayers (in a structure-dependent manner) rather than influencing the rate of solute adsorption/desorption on the membrane surface. We suppose that the effect of pluronics on doxorubicin permeation across lipid bilayers along with the known effect on the multidrug resistance protein determines its influence on the therapeutic activity of anthracycline drugs.
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Affiliation(s)
- V Y Erukova
- A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia
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Evtodienko VY, Bondarenko DI, Antonenko YN. Permeation of dicarboxylic acids with different terminal position of two carboxylic groups through planar bilayer lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1420:95-103. [PMID: 10446294 DOI: 10.1016/s0005-2736(99)00095-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Electrically silent hydrogen ion fluxes across a planar bilayer lipid membrane (BLM) induced by an addition of dicarboxylic (DC) acids at one side of BLM are monitored by measuring pH changes in the unstirred layers near the BLM surface via recording protonophore-dependent potentials. Two groups of DC acids are studied: (1) 2-n-alkylmalonic acids with an alkyl chain of different length which carry both carboxylic groups at one terminus of the hydrocarbon chain (alpha,alpha-DC acids); and (2) dicarboxylic acids of different linear chain length having carboxylic groups at the opposite ends of the hydrocarbon chain (alpha,omega-DC acids). It is shown that the pH optimum of hydrogen ion fluxes for the DC acids is shifted considerably to acidic pH values compared to monocarboxylic acids and is located near pH 5. For both types of DC acids at pH&z. Lt;5, the total transport is limited by diffusion of the anionic forms of the acids across the unstirred layers, while at pH&z.Gt;5 the transport is limited by diffusion of the neutral form across the membrane. The fluxes of alpha,alpha-DC acids are similar to those of alpha,omega-DC acids provided that the acids have the similar number of carbon atoms, the fluxes grow with the increase in the chain length of the alkyl radical.
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Affiliation(s)
- V Y Evtodienko
- A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russian Federation
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From self-assembled bilayer lipid membranes (BLMs) to supported BLMs on metal and gel substrates to practical applications. Colloids Surf A Physicochem Eng Asp 1999. [DOI: 10.1016/s0927-7757(98)00330-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Evtodienko VY, Antonenko YN, Yaguzhinsky LS. Increase of local hydrogen ion gradient near bilayer lipid membrane under the conditions of catalysis of proton transfer across the interface. FEBS Lett 1998; 425:222-4. [PMID: 9559652 DOI: 10.1016/s0014-5793(98)00233-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The measurements of pH profiles in the unstirred layers (USLs) near planar bilayer lipid membranes (BLM) were applied for the evaluation of the hydrogen ion fluxes which were induced by nigericin in the presence of potassium ion gradients. It was shown that at high concentrations of KCl the increase in the concentration of citrate buffer caused an anomalous effect, namely, an increase in the local pH shifts in the USLs. The hydrogen ion flux rose 50 times upon the increase in the citrate concentration from 1 mM to 20 mM. Phosphate stimulated the flux 7 times under these conditions. In agreement with our previous results, at low KCl concentrations, when the process is limited by the K+-nigericin interaction, an increase in the buffer concentration led to a reduction of the local pH shifts, under these conditions the usual concentration dependence was observed. The data obtained favor the model implying the existence of the kinetic barrier for proton transfer at the membrane-water interface.
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Affiliation(s)
- V Y Evtodienko
- A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russia
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