1
|
Meredith SA, Kusunoki Y, Connell SD, Morigaki K, Evans SD, Adams PG. Self-Quenching Behavior of a Fluorescent Probe Incorporated within Lipid Membranes Explored Using Electrophoresis and Fluorescence Lifetime Imaging Microscopy. J Phys Chem B 2023; 127:1715-1727. [PMID: 36802586 PMCID: PMC9986866 DOI: 10.1021/acs.jpcb.2c07652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Fluorescent probes are useful in biophysics research to assess the spatial distribution, mobility, and interactions of biomolecules. However, fluorophores can undergo "self-quenching" of their fluorescence intensity at high concentrations. A greater understanding of concentration-quenching effects is important for avoiding artifacts in fluorescence images and relevant to energy transfer processes in photosynthesis. Here, we show that an electrophoresis technique can be used to control the migration of charged fluorophores associated with supported lipid bilayers (SLBs) and that quenching effects can be quantified with fluorescence lifetime imaging microscopy (FLIM). Confined SLBs containing controlled quantities of lipid-linked Texas Red (TR) fluorophores were generated within 100 × 100 μm corral regions on glass substrates. Application of an electric field in-plane with the lipid bilayer induced the migration of negatively charged TR-lipid molecules toward the positive electrode and created a lateral concentration gradient across each corral. The self-quenching of TR was directly observed in FLIM images as a correlation of high concentrations of fluorophores to reductions in their fluorescence lifetime. By varying the initial concentration of TR fluorophores incorporated into the SLBs from 0.3% to 0.8% (mol/mol), the maximum concentration of fluorophores reached during electrophoresis could be modulated from 2% up to 7% (mol/mol), leading to the reduction of fluorescence lifetime down to 30% and quenching of the fluorescence intensity down to 10% of their original levels. As part of this work, we demonstrated a method for converting fluorescence intensity profiles into molecular concentration profiles by correcting for quenching effects. The calculated concentration profiles have a good fit to an exponential growth function, suggesting that TR-lipids can diffuse freely even at high concentrations. Overall, these findings prove that electrophoresis is effective at producing microscale concentration gradients of a molecule-of-interest and that FLIM is an excellent approach to interrogate dynamic changes to molecular interactions via their photophysical state.
Collapse
Affiliation(s)
- Sophie A Meredith
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U. K.,Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, U. K
| | - Yuka Kusunoki
- Graduate School of Agricultural Science, Kobe University, Rokkodaicho 1-1, Nada, Kobe 657-8501, Japan
| | - Simon D Connell
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U. K.,Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, U. K
| | - Kenichi Morigaki
- Graduate School of Agricultural Science and Biosignal Research Center, Kobe University, Rokkodaicho 1-1, Nada, Kobe 657-8501, Japan
| | - Stephen D Evans
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U. K.,Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, U. K
| | - Peter G Adams
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U. K.,Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, U. K
| |
Collapse
|
2
|
Paterson DA, Du X, Bao P, Parry AA, Peyman SA, Sandoe JAT, Evans SD, Luo D, Bushby RJ, Jones JC, Gleeson HF. Chiral nematic liquid crystal droplets as a basis for sensor systems. MOLECULAR SYSTEMS DESIGN & ENGINEERING 2022; 7:607-621. [PMID: 36876150 PMCID: PMC9972830 DOI: 10.1039/d1me00189b] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Accepted: 02/28/2022] [Indexed: 05/22/2023]
Abstract
For a series of phospholipid coated calamitic nematic liquid crystal droplets (5CB, 6CB, 7CB, E7 and MLC7023) of diameter ∼18 μm, the addition of chiral dopant leaves the sign of surface anchoring unchanged. Herein we report that for these chiral nematic droplets an analyte induced transition from a Frank-Pryce structure (with planar anchoring) to a nested-cup structure (with perpendicular anchoring) is accompanied by changes in the intensity of reflected light. We propose this system as both a general scheme for understanding director fields in chiral nematic liquid crystal droplets with perpendicular anchoring and as an ideal candidate to be utilised as the basis for developing cheap, single use LC-based sensor devices.
Collapse
Affiliation(s)
- Daniel A Paterson
- School of Physics and Astronomy, University of Leeds Leeds LS2 9JT UK
- School of Chemistry, University of Leeds Leeds LS2 9JT UK
| | - Xiaoxue Du
- School of Physics and Astronomy, University of Leeds Leeds LS2 9JT UK
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology Shenzhen 518055 China
| | - Peng Bao
- School of Physics and Astronomy, University of Leeds Leeds LS2 9JT UK
| | - Adele A Parry
- School of Physics and Astronomy, University of Leeds Leeds LS2 9JT UK
| | - Sally A Peyman
- School of Physics and Astronomy, University of Leeds Leeds LS2 9JT UK
- Leeds Institute of Medical Research, University of Leeds Leeds LS2 9JT UK
| | | | - Stephen D Evans
- School of Physics and Astronomy, University of Leeds Leeds LS2 9JT UK
| | - Dan Luo
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology Shenzhen 518055 China
| | | | - J Cliff Jones
- School of Physics and Astronomy, University of Leeds Leeds LS2 9JT UK
| | - Helen F Gleeson
- School of Physics and Astronomy, University of Leeds Leeds LS2 9JT UK
| |
Collapse
|
3
|
Paterson DA, Bao P, Abou-Saleh RH, Peyman SA, Jones JC, Sandoe JAT, Evans SD, Gleeson HF, Bushby RJ. Control of Director Fields in Phospholipid-Coated Liquid Crystal Droplets. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:6436-6446. [PMID: 32392071 DOI: 10.1021/acs.langmuir.0c00651] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In liquid crystal (LC) droplets, small changes in surface anchoring energy can produce large changes in the director field which result in readily detectable optical effects. This makes them attractive for use as biosensors. Coating LC droplets with a phospholipid monolayer provides a bridge between the hydrophobic world of LCs and the water-based world of biology and makes it possible to incorporate naturally occurring biosensor systems. However, phospholipids promote strong perpendicular (homeotropic) anchoring that can inhibit switching of the director field. We show that the tendency for phospholipid layers to promote perpendicular anchoring can be suppressed by using synthetic phospholipids in which the acyl chains are terminated with bulky tert-butyl or ferrocenyl groups; the larger these end-group(s), the less likely the system is to be perpendicular/radial. Additionally, the droplet director field is found to be dependent on the nature of the LC, particularly its intrinsic surface properties, but not (apparently) on the sign of the dielectric anisotropy, the proximity to the melting/isotropic phase transition, the surface tension (in air), or the values of the Frank elastic constants.
Collapse
Affiliation(s)
- Daniel A Paterson
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K
- School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K
| | - Peng Bao
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K
| | - Radwa H Abou-Saleh
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K
- Biophysics Group, Department of Physics, Faculty of Science, Mansoura University, Mansoura, Egypt
| | - Sally A Peyman
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K
- School of Medicine, University of Leeds, Leeds LS2 9JT, U.K
| | - J Cliff Jones
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K
| | - Jonathan A T Sandoe
- Leeds Institute of Medical Research, University of Leeds, Leeds LS2 9JT, U.K
| | - Stephen D Evans
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K
| | - Helen F Gleeson
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K
| | | |
Collapse
|
4
|
Bao P, Paterson DA, Harrison PL, Miller K, Peyman S, Jones JC, Sandoe J, Evans SD, Bushby RJ, Gleeson HF. Lipid coated liquid crystal droplets for the on-chip detection of antimicrobial peptides. LAB ON A CHIP 2019; 19:1082-1089. [PMID: 30785139 PMCID: PMC6484679 DOI: 10.1039/c8lc01291a] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 01/28/2019] [Indexed: 05/22/2023]
Abstract
We describe a novel biosensor based on phospholipid-coated nematic liquid crystal (LC) droplets and demonstrate the detection of Smp43, a model antimicrobial peptide (AMP) from the venom of North African scorpion Scorpio maurus palmatus. Mono-disperse lipid-coated LC droplets of diameter 16.7 ± 0.2 μm were generated using PDMS microfluidic devices with a flow-focusing configuration and were the target for AMPs. The droplets were trapped in a bespoke microfluidic trap structure and were simultaneously treated with Smp43 at gradient concentrations in six different chambers. The disruption of the lipid monolayer by the Smp43 was detected (<6 μM) at concentrations well within its biologically active range, indicated by a dramatic change in the appearance of the droplets associated with the transition from a typical radial configuration to a bipolar configuration, which is readily observed by polarizing microscopy. This suggests the system has feasibility as a drug-discovery screening tool. Further, compared to previously reported LC droplet biosensors, this LC droplet biosensor with a lipid coating is more biologically relevant and its ease of use in detecting membrane-related biological processes and interactions has the potential for development as a reliable, low-cost and disposable point of care diagnostic tool.
Collapse
Affiliation(s)
- Peng Bao
- School of Physics and Astronomy
, University of Leeds
,
Leeds
, UK
.
;
;
| | - Daniel A. Paterson
- School of Physics and Astronomy
, University of Leeds
,
Leeds
, UK
.
;
;
| | | | - Keith Miller
- Biomolecular Research Centre
, Sheffield Hallam University
,
Sheffield
, UK
| | - Sally Peyman
- School of Physics and Astronomy
, University of Leeds
,
Leeds
, UK
.
;
;
| | - J. Cliff Jones
- School of Physics and Astronomy
, University of Leeds
,
Leeds
, UK
.
;
;
| | - Jonathan Sandoe
- Leeds Institute of Biomedical & Clinical Science
, University of Leeds
,
Leeds
, UK
| | - Stephen D. Evans
- School of Physics and Astronomy
, University of Leeds
,
Leeds
, UK
.
;
;
| | - Richard J. Bushby
- School of Physics and Astronomy
, University of Leeds
,
Leeds
, UK
.
;
;
| | - Helen F. Gleeson
- School of Physics and Astronomy
, University of Leeds
,
Leeds
, UK
.
;
;
| |
Collapse
|
5
|
Sendecki AM, Poyton MF, Baxter AJ, Yang T, Cremer PS. Supported Lipid Bilayers with Phosphatidylethanolamine as the Major Component. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:13423-13429. [PMID: 29119796 DOI: 10.1021/acs.langmuir.7b02323] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Phosphatidylethanolamine (PE) is notoriously difficult to incorporate into model membrane systems, such as fluid supported lipid bilayers (SLBs), at high concentrations because of its intrinsic negative curvature. Using fluorescence-based techniques, we demonstrate that having fewer sites of unsaturation in the lipid tails leads to high-quality SLBs because these lipids help to minimize the curvature. Moreover, shorter saturated chains can help maintain the membranes in the fluid phase. Using these two guidelines, we find that up to 70 mol % PE can be incorporated into SLBs at room temperature and up to 90 mol % PE can be incorporated at 37 °C. Curiously, conditions under which three-dimensional tubules project outward from the planar surface as well as conditions under which domain formation occurs can be found. We have employed these model membrane systems to explore the ability of Ni2+ to bind to PE. It was found that this transition metal ion binds 1000-fold tighter to PE than to phosphatidylcholine lipids. In the future, this platform could be exploited to monitor the binding of other transition metal ions or the binding of antimicrobial peptides. It could also be employed to explore the physical properties of PE-containing membranes, such as phase domain behavior and intermolecular hydrogen bonding.
Collapse
Affiliation(s)
- Anne M Sendecki
- Department of Chemistry and ‡Department of Biochemistry and Molecular Biology, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Matthew F Poyton
- Department of Chemistry and ‡Department of Biochemistry and Molecular Biology, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Alexis J Baxter
- Department of Chemistry and ‡Department of Biochemistry and Molecular Biology, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Tinglu Yang
- Department of Chemistry and ‡Department of Biochemistry and Molecular Biology, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Paul S Cremer
- Department of Chemistry and ‡Department of Biochemistry and Molecular Biology, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| |
Collapse
|
6
|
Harb F, Giudici-Orticoni MT, Guiral M, Tinland B. Electrophoretic mobility of a monotopic membrane protein inserted into the top of supported lipid bilayers. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2016; 39:127. [PMID: 28012146 DOI: 10.1140/epje/i2016-16127-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 11/22/2016] [Indexed: 06/06/2023]
Abstract
We have studied the translational migration of a monotopic membrane protein, the bacterial sulfide quinone reductase (SQR) in supported n-bilayers ([Formula: see text]) under the influence of an electric field parallel to the membrane plane. The direction of the migration changes when the charge of the protein changes its sign. Measuring mobilities at different pH enables us to gain experimental physico-chemical data on SQR as its isoelectric point and its estimated oligomeric state (at least trimeric) when inserted in a lipid membrane. Consequently, in addition to the migration study of membrane proteins in a lipid environment, this experimental system, previously used with a transmembrane protein, is thus suitable to define membrane protein properties in conditions approaching the native ones (in the absence of detergent).
Collapse
Affiliation(s)
- Frédéric Harb
- Doctoral school for Science and Technology, platform for research in Nanosciences and Nanotechnology, Lebanese University, Campus Pierre Gemayel, BP 90239, Fanar-Metn, Lebanon
- Aix-Marseille Univ, CINaM-CNRS, UMR7325, 13288, Marseille, France
| | | | - Marianne Guiral
- Aix Marseille Univ, CNRS, BIP UMR 7281, 13402, Marseille, France
| | - Bernard Tinland
- Aix-Marseille Univ, CINaM-CNRS, UMR7325, 13288, Marseille, France.
| |
Collapse
|
7
|
van Weerd J, Karperien M, Jonkheijm P. Supported Lipid Bilayers for the Generation of Dynamic Cell-Material Interfaces. Adv Healthc Mater 2015; 4:2743-79. [PMID: 26573989 DOI: 10.1002/adhm.201500398] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 08/03/2015] [Indexed: 12/13/2022]
Abstract
Supported lipid bilayers (SLB) offer unique possibilities for studying cellular membranes and have been used as a synthetic architecture to interact with cells. Here, the state-of-the-art in SLB-based technology is presented. The fabrication, analysis, characteristics and modification of SLBs are described in great detail. Numerous strategies to form SLBs on different substrates, and the means to patteren them, are described. The use of SLBs as model membranes for the study of membrane organization and membrane processes in vitro is highlighted. In addition, the use of SLBs as a substratum for cell analysis is presented, with discrimination between cell-cell and cell-extracellular matrix (ECM) mimicry. The study is concluded with a discussion of the potential for in vivo applications of SLBs.
Collapse
Affiliation(s)
- Jasper van Weerd
- Bioinspired Molecular Engineering; University of Twente; PO Box 217 7500 AE Enschede The Netherlands
- Dept. of Developmental BioEngineering; MIRA Institute for Biomedical Technology and Technical Medicine; University of Twente; PO Box 217 7500 AE Enschede The Netherlands
- Molecular Nanofabrication Group, MESA+; University of Twente; Enschede 7500 AE The Netherlands
| | - Marcel Karperien
- Dept. of Developmental BioEngineering; MIRA Institute for Biomedical Technology and Technical Medicine; University of Twente; PO Box 217 7500 AE Enschede The Netherlands
| | - Pascal Jonkheijm
- Bioinspired Molecular Engineering; University of Twente; PO Box 217 7500 AE Enschede The Netherlands
- Molecular Nanofabrication Group, MESA+; University of Twente; Enschede 7500 AE The Netherlands
| |
Collapse
|
8
|
Cheng N, Bao P, Evans SD, Leggett GJ, Armes SP. Facile Formation of Highly Mobile Supported Lipid Bilayers on Surface-Quaternized pH-Responsive Polymer Brushes. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b00435] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- N. Cheng
- Department
of Chemistry, University of Sheffield, Sheffield S3 7HF, U.K
| | - P. Bao
- Molecular and Nanoscale Physics Group,
School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K
| | - S. D. Evans
- Molecular and Nanoscale Physics Group,
School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K
| | - G. J. Leggett
- Department
of Chemistry, University of Sheffield, Sheffield S3 7HF, U.K
| | - S. P. Armes
- Department
of Chemistry, University of Sheffield, Sheffield S3 7HF, U.K
| |
Collapse
|
9
|
van Weerd J, Krabbenborg SO, Eijkel J, Karperien M, Huskens J, Jonkheijm P. On-chip electrophoresis in supported lipid bilayer membranes achieved using low potentials. J Am Chem Soc 2014; 136:100-3. [PMID: 24345193 PMCID: PMC3901391 DOI: 10.1021/ja411287u] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Indexed: 01/10/2023]
Abstract
A micro supported lipid bilayer (SLB) electrophoresis method was developed, which functions at low potentials and appreciable operating times. To this end, (hydroxymethyl)-ferrocene (FcCH2OH) was employed to provide an electrochemical reaction at the anode and cathode at low applied potential to avoid electrolysis of water. The addition of FcCH2OH did not alter the SLB characteristics or affect biomolecule function, and pH and temperature variations and bubble formation were eliminated. Applying potentials of 0.25-1.2 V during flow gave homogeneous electrical fields and a fast, reversible, and strong build-up of a charged dye-modified lipid in the direction of the oppositely charged electrode. Moreover, streptavidin mobility could be modulated. This method paves the way for further development of analytical devices.
Collapse
Affiliation(s)
- Jasper van Weerd
- Molecular nanoFabrication group and BIOS lab-on-a-chip
group, MESA Institute for Nanotechnology, University
of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
- Developmental
Bioengineering, MIRA Biomedical Technology and Technical Medicine, University of Twente,
P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Sven O. Krabbenborg
- Molecular nanoFabrication group and BIOS lab-on-a-chip
group, MESA Institute for Nanotechnology, University
of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Jan Eijkel
- Molecular nanoFabrication group and BIOS lab-on-a-chip
group, MESA Institute for Nanotechnology, University
of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Marcel Karperien
- Developmental
Bioengineering, MIRA Biomedical Technology and Technical Medicine, University of Twente,
P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Jurriaan Huskens
- Molecular nanoFabrication group and BIOS lab-on-a-chip
group, MESA Institute for Nanotechnology, University
of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Pascal Jonkheijm
- Molecular nanoFabrication group and BIOS lab-on-a-chip
group, MESA Institute for Nanotechnology, University
of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| |
Collapse
|
10
|
Abstract
While electrophoresis in lipid bilayers has been performed since the 1970s, the technique has until now been unable to accurately measure the charge on lipids and proteins within the membrane based on drift velocity measurements. Part of the problem is caused by the use of the Einstein-Smoluchowski equation to estimate the electrophoretic mobility of such species. The source of the error arises from the fact that a lipid headgroup is typically smaller than the Debye length of the adjacent aqueous solution in most electrophoresis experiments. Instead, the Henry equation can more accurately predict the electrophoretic mobility at sufficient ionic strength. This was done for three dye-labeled lipids with different sized head groups and a charge on each lipid of -1. Also, the charge was measured as a function of pH for two titratable lipids that were fluorescently labeled. Finally, it was shown that the Henry equation also has difficulties measuring the correct lipid charge at salt concentrations below 5 mM, where electroosmotic forces are more significant.
Collapse
Affiliation(s)
- Matthew F Poyton
- Department of Chemistry, Department of Biochemistry and Molecular Biology, Penn State University , State College, Pennsylvania 16802, United States
| | | |
Collapse
|