1
|
Taylor JM, Conboy JC. Issues with lipid probes in flip-flop measurements: A comparative study using sum-frequency vibrational spectroscopy and second-harmonic generation. J Chem Phys 2024; 161:085104. [PMID: 39185850 DOI: 10.1063/5.0226075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2024] [Accepted: 08/11/2024] [Indexed: 08/27/2024] Open
Abstract
Fluorescent lipid probes such as 1-palmitoyl-2-(6-[7-nitro-2-1,3-benzoxadiazol-4-yl]amino-hexanoyl)-sn-glycero-3-phosphocholine (C6 NBD-PC) have been used extensively to study the kinetics of lipid flip-flop. However, the efficacy of these probes as reliable reporters of native lipid translocation has never been tested. In this study, sum-frequency vibrational spectroscopy (SFVS) was used to measure the kinetics of C6 NBD-PC lipid flip-flop and the flip-flop of native lipids in planar supported lipid bilayers. C6 NBD-PC was investigated at concentrations of 1 and 3 mol. % in both chain-matched 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and chain-mismatched 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) to assess the ability of C6 NBD-PC to mimic the behavior of the surrounding matrix lipids. It was observed that C6 NBD-PC exhibited faster flip-flop kinetics compared to the native lipids in both DPPC and DSPC matrices, with notably accelerated rates in the chain-mismatched DSPC system. SFVS was also used to measure the acyl chain orientation and gauche content of C6 NBD-PC in both DPPC and DSPC membranes. In the DSPC matrix (chain mismatched), C6 NBD-PC was more disordered in terms of both gauche content and acyl tilt, whereas it maintained an orientation similar to that of the native lipids in the DPPC matrix (chain matched). In addition, the flip-flop kinetics of C6 NBD-PC were also measured using second-harmonic generation (SHG) spectroscopy, by probing the motion of the NBD chromophore directly. The flip-flop kinetics measured by SHG were consistent with those obtained from SFVS. This study also marks the first instance of phospholipid flip-flop kinetics being measured via SHG. The results of this study clearly demonstrate that C6 NBD-PC does not adequately mimic the behavior of native lipids within a membrane. These findings also highlight the significant impact of the lipid matrix on the flip-flop behavior of the fluorescently labeled lipid, C6 NBD-PC.
Collapse
Affiliation(s)
- Joshua M Taylor
- Department of Chemistry, University of Utah, 315 South 1400 East RM. 2020, Salt Lake City, Utah 84112, USA
| | - John C Conboy
- Department of Chemistry, University of Utah, 315 South 1400 East RM. 2020, Salt Lake City, Utah 84112, USA
| |
Collapse
|
2
|
Gh. MS, Wilhelm MJ, Dai HL. Observing mechanosensitive channels in action in living bacteria. BIOPHYSICAL REPORTS 2024; 4:100141. [PMID: 38189030 PMCID: PMC10765490 DOI: 10.1016/j.bpr.2023.100141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 12/07/2023] [Indexed: 01/09/2024]
Abstract
Mechanosensitive (MS) channels act to protect the cytoplasmic membrane (CM) of living cells from environmental changes in osmolarity. In this report, we demonstrate the use of time-resolved second-harmonic light scattering (SHS) as a means of experimentally observing the relative state (open versus closed) of MS channels in living bacteria suspended in different buffer solutions. Specifically, the state of the MS channels was selectively controlled by changing the composition of the suspension medium, inducing either a transient or persistent osmotic shock. SHS was then used to monitor transport of the SHG-active cation, malachite green, across the bacterial CM. When MS channels were forced open, malachite green cations were able to cross the CM at a rate at least two orders of magnitude faster compared with when the MS channels were closed. These observations were corroborated using both numerical model simulations and complementary fluorescence experiments, in which the propensity for the CM impermeant cation, propidium, to stain cells was shown to be contingent upon the relative state of the MS channels (i.e., cells with open MS channels fluoresced red, cells with closed MS channels did not). Application of time-resolved SHS to experimentally distinguish MS channels opened via osmotic shock versus chemical activation, as well as a general comparison with the patch-clamp method is discussed.
Collapse
Affiliation(s)
| | | | - Hai-Lung Dai
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania
| |
Collapse
|
3
|
Li B, Li J, Chen S, Yuan Q, Fang C, Gan W. Monitoring the response of a model protocell to dye and surfactant molecules through second harmonic generation and fluorescence imaging. Phys Chem Chem Phys 2024; 26:8148-8157. [PMID: 38380536 DOI: 10.1039/d4cp00009a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
Probing the interaction between molecules and protocells is crucial for understanding the passive transport of functional molecules in and out of artificial and real cells. Second-harmonic generation (SHG) has been proven to be a powerful method for analyzing the adsorption and cross-membrane transport of molecules on lipid bilayers. In this study, we used SHG and two-photon fluorescence (TPF) imaging to study the interaction of charged dye molecules (D289) with a lipid vesicle. Unexpectedly, it was observed that the transport of D289 at a relatively high concentration is not as efficient as that at a lower dye concentration. Periodic shrinking of the model protocell and discharging of D289 out from the vesicle were revealed by combined analyses of SHG and TPF images. The response of the vesicle to a surfactant was also analyzed with D289 as a probe. This work demonstrates that the combined SHG and TPF imaging method is a unique approach that can provide detailed information on the interaction of molecules and lipids (both morphology and molecular kinetics). Determining these subtle interfacial kinetics in molecules is important for understanding the mechanism of many biophysical processes occurring on lipids.
Collapse
Affiliation(s)
- Bifei Li
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, School of Science, Harbin Institute of Technology (Shenzhen), University Town, Shenzhen 518055, Guangdong, China.
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
| | - Jianhui Li
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, School of Science, Harbin Institute of Technology (Shenzhen), University Town, Shenzhen 518055, Guangdong, China.
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
| | - Shujiao Chen
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, School of Science, Harbin Institute of Technology (Shenzhen), University Town, Shenzhen 518055, Guangdong, China.
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
| | - Qunhui Yuan
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, School of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), University Town, Shenzhen 518055, Guangdong, China.
| | - Chao Fang
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, School of Science, Harbin Institute of Technology (Shenzhen), University Town, Shenzhen 518055, Guangdong, China.
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
| | - Wei Gan
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, School of Science, Harbin Institute of Technology (Shenzhen), University Town, Shenzhen 518055, Guangdong, China.
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
| |
Collapse
|
4
|
Influence of Phase Transitions on Diffusive Molecular Transport Across Biological Membranes. Angew Chem Int Ed Engl 2022; 61:e202205608. [DOI: 10.1002/anie.202205608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Indexed: 11/07/2022]
|
5
|
Wu T, Wilhelm MJ, Ma J, Li Y, Wu Y, Dai HL. Influence of Phase Transitions on Diffusive Molecular Transport Across Biological Membranes. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202205608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Tong Wu
- Temple University Department of Chemistry UNITED STATES
| | - Michael J. Wilhelm
- Temple University Department of Chemistry 1901 N. 13th Street 19122 Philadelphia UNITED STATES
| | - Jianqiang Ma
- Temple University Department of Chemistry UNITED STATES
| | - Yujie Li
- Temple University Department of Chemistry UNITED STATES
| | - Yuhao Wu
- Temple University Department of Chemistry UNITED STATES
| | - Hai-Lung Dai
- Temple University Department of Chemistry UNITED STATES
| |
Collapse
|
6
|
Observing the structural variations on binary complex vesicle surfaces and the influence on molecular transportation. Chem Phys 2021. [DOI: 10.1016/j.chemphys.2021.111250] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
|
7
|
Sharifian Gh M. Recent Experimental Developments in Studying Passive Membrane Transport of Drug Molecules. Mol Pharm 2021; 18:2122-2141. [PMID: 33914545 DOI: 10.1021/acs.molpharmaceut.1c00009] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The ability to measure the passive membrane permeation of drug-like molecules is of fundamental biological and pharmaceutical importance. Of significance, passive diffusion across the cellular membranes plays an effective role in the delivery of many pharmaceutical agents to intracellular targets. Hence, approaches for quantitative measurement of membrane permeability have been the topics of research for decades, resulting in sophisticated biomimetic systems coupled with advanced techniques. In this review, recent developments in experimental approaches along with theoretical models for quantitative and real-time analysis of membrane transport of drug-like molecules through mimetic and living cell membranes are discussed. The focus is on time-resolved fluorescence-based, surface plasmon resonance, and second-harmonic light scattering approaches. The current understanding of how properties of the membrane and permeant affect the permeation process is discussed.
Collapse
Affiliation(s)
- Mohammad Sharifian Gh
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908, United States
| |
Collapse
|
8
|
Wilhelm MJ, Dai HL. Molecule-Membrane Interactions in Biological Cells Studied with Second Harmonic Light Scattering. Chem Asian J 2019; 15:200-213. [PMID: 31721448 DOI: 10.1002/asia.201901406] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 11/12/2019] [Indexed: 12/13/2022]
Abstract
The nonlinear optical phenomenon second harmonic light scattering (SHS) can be used for detecting molecules at the membrane surfaces of living biological cells. Over the last decade, SHS has been developed for quantitatively monitoring the adsorption and transport of small and medium size molecules (both neutral and ionic) across membranes in living cells. SHS can be operated with both time and spatial resolution and is even capable of isolating molecule-membrane interactions at specific membrane surfaces in multi-membrane cells, such as bacteria. In this review, we discuss select examples from our lab employing time-resolved SHS to study real-time molecular interactions at the plasma membranes of biological cells. We first demonstrate the utility of this method for determining the transport rates at each membrane/interface in a Gram-negative bacterial cell. Next, we show how SHS can be used to characterize the molecular mechanism of the century old Gram stain protocol for classifying bacteria. Additionally, we examine how membrane structures and molecular charge and polarity affect adsorption and transport, as well as how antimicrobial compounds alter bacteria membrane permeability. Finally, we discuss adaptation of SHS as an imaging modality to quantify molecular adsorption and transport in sub-cellular regions of individual living cells.
Collapse
Affiliation(s)
- Michael J Wilhelm
- Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, PA 19122, USA
| | - Hai-Lung Dai
- Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, PA 19122, USA
| |
Collapse
|
9
|
Sharifian Gh M, Wilhelm MJ, Moore M, Dai HL. Spatially Resolved Membrane Transport in a Single Cell Imaged by Second Harmonic Light Scattering. Biochemistry 2019; 58:1841-1844. [PMID: 30912648 DOI: 10.1021/acs.biochem.9b00110] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We demonstrate that time-resolved second harmonic (SH) light scattering, when applied as an imaging modality, can be used to spatially resolve the adsorption and transport rates of molecules diffusing across the membrane in a living cell. As a representative example, we measure the passive transport of the amphiphilic ion, malachite green, across the plasma membrane in living human dermal fibroblast cells. Analysis of the time-resolved SH images reveals that membrane regions, which appear to be enduring higher stress, exhibit slower transport rates. It is proposed that this stress-transport relation may be a result of local enrichment of membrane rigidifiers as part of a response to maintain membrane integrity under strain.
Collapse
Affiliation(s)
- Mohammad Sharifian Gh
- Department of Chemistry , Temple University , 1901 N. 13th Street , Philadelphia , Pennsylvania 19122 , United States
| | - Michael J Wilhelm
- Department of Chemistry , Temple University , 1901 N. 13th Street , Philadelphia , Pennsylvania 19122 , United States
| | - Michael Moore
- Optical Science Center for Applied Research , Delaware State University , Dover , Delaware 19904 , United States
| | - Hai-Lung Dai
- Department of Chemistry , Temple University , 1901 N. 13th Street , Philadelphia , Pennsylvania 19122 , United States
| |
Collapse
|
10
|
Wilhelm MJ, Sharifian Gh M, Dai HL. Influence of molecular structure on passive membrane transport: A case study by second harmonic light scattering. J Chem Phys 2019; 150:104705. [PMID: 30876365 DOI: 10.1063/1.5081720] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present an experimental study, using the surface sensitive technique, second harmonic light scattering (SHS), to examine the influence of structure on the propensity of a molecule to passively diffuse across a phospholipid membrane. Specifically, we monitor the relative tendency of the structurally similar amphiphilic cationic dyes, malachite green (MG) and crystal violet (CV), to transport across membranes in living cells (E. coli) and biomimetic liposomes. Despite having nearly identical molecular structures, molecular weights, cationic charges, and functional groups, MG is of lower overall symmetry and consequently has a symmetry allowed permanent dipole moment, which CV does not. The two molecules showed drastically different interactions with phospholipid membranes. MG is observed to readily cross the hydrophobic interior of the bacterial cytoplasmic membrane. Conversely, CV does not. Furthermore, experiments conducted with biomimetic liposomes, constructed from the total lipid extract of E. coli and containing no proteins, show that while MG is able to diffuse across the liposome membrane, CV does not. These observations indicate that the SHS results measured with bacteria do not result from the functions of efflux pumps, but suggests that MG possesses an innate molecular property (which is absent in CV) that allows it to passively diffuse across the hydrophobic interior of a phospholipid membrane.
Collapse
Affiliation(s)
- Michael J Wilhelm
- Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, USA
| | - Mohammad Sharifian Gh
- Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, USA
| | - Hai-Lung Dai
- Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, USA
| |
Collapse
|
11
|
Kim JH. Two-step adsorption kinetics of malachite green on anionic polystyrene microspheres in aqueous solution probed by second harmonic generation. Phys Chem Chem Phys 2017; 19:21887-21892. [PMID: 28787062 DOI: 10.1039/c7cp03088f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Adsorption of organic cations of malachite green (MG) on an anionic microsphere surface was monitored in real time using a surface-specific second-harmonic generation (SHG) technique. This adsorption was found to consist of two processes of different timescales for all MG concentrations, which has not been considered in previous SHG experiments. The two-step adsorption can be well explained by our suggested model, which consists of an initial fast electrostatic alignment of weakly bound MG followed by slow non-electrostatic adsorption of MG on the surface of a microsphere. This study shows the importance of kinetics measurements in providing full understanding of adsorption of charged molecules on colloid surfaces.
Collapse
Affiliation(s)
- Joon Heon Kim
- Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea.
| |
Collapse
|
12
|
Sharifian Gh M, Wilhelm MJ, Dai HL. Label-Free Optical Method for Quantifying Molecular Transport Across Cellular Membranes In Vitro. J Phys Chem Lett 2016; 7:3406-3411. [PMID: 27518496 DOI: 10.1021/acs.jpclett.6b01483] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate a nonlinear optical method for the label-free quantification of membrane transport rates of small/medium size molecules in living cells. Specifically, second-harmonic generation (SHG) laser scattering permits surface-specific characterization of transport across membranes. Unfortunately, most biologically relevant molecules are SHG-inactive. In the interest of extending this methodology for characterizing transport of any molecule, we monitor the SHG produced from an SHG-active reference molecule, in the presence of an SHG-inactive target molecule-of-interest as both molecules compete to cross a membrane. Of significance, the SHG-inactive target transport rate can be deduced as a perturbation in the measured transport rate of the reference. As proof-of-principle, we examine competitive transport of the strongly SHG-active cation, malachite green (MG), in the presence of a weakly SHG-active dication, propidium (Pro), across the outer-membrane protein channels in living bacteria. Comparison of the extracted and directly measured Pro transport rates validates the effectiveness of the method.
Collapse
Affiliation(s)
- Mohammad Sharifian Gh
- Department of Chemistry, Temple University , 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Michael J Wilhelm
- Department of Chemistry, Temple University , 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Hai-Lung Dai
- Department of Chemistry, Temple University , 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| |
Collapse
|
13
|
Wilhelm MJ, Sheffield JB, Sharifian Gh. M, Wu Y, Spahr C, Gonella G, Xu B, Dai HL. Gram's Stain Does Not Cross the Bacterial Cytoplasmic Membrane. ACS Chem Biol 2015; 10:1711-7. [PMID: 25879387 DOI: 10.1021/acschembio.5b00042] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
For well over a century, Hans Christian Gram's famous staining protocol has been the standard go-to diagnostic for characterizing unknown bacteria. Despite continuous and ubiquitous use, we now demonstrate that the current understanding of the molecular mechanism for this differential stain is largely incorrect. Using the fully complementary time-resolved methods: second-harmonic light-scattering and bright-field transmission microscopy, we present a real-time and membrane specific quantitative characterization of the bacterial uptake of crystal-violet (CV), the dye used in Gram's protocol. Our observations contradict the currently accepted mechanism which depicts that, for both Gram-negative and Gram-positive bacteria, CV readily traverses the peptidoglycan mesh (PM) and cytoplasmic membrane (CM) before equilibrating within the cytosol. We find that not only is CV unable to traverse the CM but, on the time-scale of the Gram-stain procedure, CV is kinetically trapped within the PM. Our results indicate that CV, rather than dyes which rapidly traverse the PM, is uniquely suited as the Gram stain.
Collapse
Affiliation(s)
- Michael J. Wilhelm
- Department
of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Joel B. Sheffield
- Department
of Biology, Temple University, 1900 N. 12th Street, Philadelphia, Pennsylvania 19122, United States
| | - Mohammad Sharifian Gh.
- Department
of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Yajing Wu
- Department
of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Christian Spahr
- Department
of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Grazia Gonella
- Department
of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Bolei Xu
- Department
of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Hai-Lung Dai
- Department
of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States
| |
Collapse
|
14
|
Wilhelm MJ, Sheffield JB, Gonella G, Wu Y, Spahr C, Zeng J, Xu B, Dai HL. Real-time molecular uptake and membrane-specific transport in living cells by optical microscopy and nonlinear light scattering. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.05.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|