We thank Michael J. Bruno, Radda Rusinova and Jon T. Sack for many stimulating discussions. Financial support from NIH, R01GM021342 and ARRA supplement R01GM021342-35S1, and the Josiah Macy, Jr. Foundation to OSA; the Tri-I CMB program for HII; and The Iris L. and Leverett S. Woodworth Medical Scientist Fellowship and NIH MSTP grant GM07739 for RK.

1. Generate ANTS-filled Liposomes
<ol>
 <li>On day 1, remove organic solvent from lipids.</li> 
	<li>Remove lipid from freezer and let it equilibrate to room temperature.</li> 
	<li>Add 0.6 mL of 25 mg/mL (1,2-dierucoyl-sn-glycero-3-phosphocholine) lipid in chloroform solution to a 25 mL round bottom flask.</li> 
	<li>Continually rotate the flask while drying under nitrogen, until all the chloroform has evaporated and a thin white film of lipid coats the entire lower half of the flask.</li> 
	<li>Dry in a des...

<ol>
	<li>Andersen, O. S., Giebisch, G. H., Purcel, E. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ion+transport+through+simple+membranes.">Ion transport through simple membranes.</a> Renal Function. , (1978).</li><li>Andersen, O. S., Koeppe, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bilayer+thickness+and+membrane+protein+function:+An+energetic+perspective.">Bilayer thickness and membrane protein function: An energetic perspective.</a> Annu. Rev. Biophys. Biomol. Struct. 36, 107-130 (2007).</li><li>Andersen, O. S., Koeppe, R. E., Roux, B., Chung, S. -. H., Andersen, O. S., Krishnamurthy, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gramicidin+channels.+Versatile+tools.">Gramicidin channels. Versatile tools.</a> Biological Membrane Ion Channels: Dynamics, Structure, and Applications. , (2007).</li><li>Berberan-Santos, M. N., Bodunov, E. N., Valeur, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mathematical+functions+for+the+analysis+of+luminescence+decays+with+underlying+distributions+1.+Kohlrausch+decay+function+(stretched+exponential.">Mathematical functions for the analysis of luminescence decays with underlying distributions 1. Kohlrausch decay function (stretched exponential.</a> Chem. Phys. 315, 171-182 (2005).</li><li>Bruggemann, E. P., Kayalar, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+the+molecularity+of+the+colicin+E1+channel+by+stopped-flow+ion+flux+kinetics.">Determination of the molecularity of the colicin E1 channel by stopped-flow ion flux kinetics.</a> Proc. Natl. Acad. Sci. USA. 83, 4273-4276 (1986).</li><li>Bruno, M. J., Koeppe, R. E., Andersen, O. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Docosahexaenoic+acid+alters+bilayer+elastic+properties.">Docosahexaenoic acid alters bilayer elastic properties.</a> Proc. Natl. Acad. Sci. USA. 104, 9638-9643 (2007).</li><li>Buboltz, J. T., Feigenson, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+strategy+for+the+preparation+of+liposomes:+rapid+solvent+exchange.">A novel strategy for the preparation of liposomes: rapid solvent exchange.</a> Biochim. Biophys. Acta. 1417, 232-245 (1999).</li><li>Gutknecht, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cadmium+&#38;+thallous+ion+permeabilities+through+lipid+bilayer+membranes.">Cadmium &#38; thallous ion permeabilities through lipid bilayer membranes.</a> Biochim. Biophys. Acta. 735, 185-188 (1983).</li><li>Ing&#243;lfsson, H. I., Koeppe, R. E., Andersen, O. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Curcumin+is+a+modulator+of+bilayer+material+properties.">Curcumin is a modulator of bilayer material properties.</a> Biochemistry. 46, 10384-10391 (2007).</li><li>Keser&#252;, G. M., Makara, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+lead+discovery+strategies+on+the+properties+of+drug+candidates.">The influence of lead discovery strategies on the properties of drug candidates.</a> Nat. Rev. Drug Discov. 8, 203-212 (2009).</li><li>Leeson, P. D., Springthorpe, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+drug-like+concepts+on+decision-making+in+medicinal+chemistry.">The influence of drug-like concepts on decision-making in medicinal chemistry.</a> Nat. Rev. Drug Discov. 6, 881-890 (2007).</li><li>Lundb k, J. A., Collingwood, S. A., Ing&#243;lfsson, H. I., Kapoor, R., Andersen, O. S., S, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lipid+bilayer+regulation+of+membrane+protein+function:+gramicidin+channels+as+molecular+force+probes.">Lipid bilayer regulation of membrane protein function: gramicidin channels as molecular force probes.</a> J. R. Soc. Interface. 7, 373-395 (2010).</li><li>Moore, H. P. &. a. m. p. ;. a. m. p., Raftery, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+spectroscopic+studies+of+cation+translocation+by+Torpedo+acetylcholine+receptor+on+a+time+scale+of+physiological+relevance.">Direct spectroscopic studies of cation translocation by Torpedo acetylcholine receptor on a time scale of physiological relevance.</a> Proc. Natl. Acad. Sci. USA. 77, 4509-4513 (1980).</li><li>Neher, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ionic+specificity+of+the+gramicidin+channel+and+the+thallous+ion.">Ionic specificity of the gramicidin channel and the thallous ion.</a> Biochim. Biophys. Acta. 401, 540-544 (1975).</li><li>O'Connell, A. M., Koeppe, R. E., Andersen, O. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetics+of+gramicidin+channel+formation+in+lipid+bilayers:+transmembrane+monomer+association.">Kinetics of gramicidin channel formation in lipid bilayers: transmembrane monomer association.</a> Science. 250, 1256-1259 (1990).</li><li>S&#248;gaard, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GABAA+receptor+function+is+regulated+by+lipid+bilayer+elasticity.">GABAA receptor function is regulated by lipid bilayer elasticity.</a> Biochemistry. 45, 13118-13129 (2006).</li><li>Waring, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defining+optimum+lipophilicity+and+molecular+weight+ranges+for+drug+candidates-Molecular+weight+dependent+lower+logD+limits+based+on+permeability.">Defining optimum lipophilicity and molecular weight ranges for drug candidates-Molecular weight dependent lower logD limits based on permeability.</a> Bioorg. Med. Chem. Lett. 19, 2844-2851 (2009).</li></ol>

A provisional patent application that covers the methods described in the manuscript has been filed. The co-inventors are HII and OSA.

We have demonstrated a fast fluorescence-based assay for determining the bilayer modifying potential of drugs and other small amphiphiles. Compounds that modify bilayer properties are likely to alter membrane protein function in an indirect, nonspecific manner, possibly contributing to "off-target" drug effects. The assay exploits the power of gramicidin channels as probes for changes in bilayer properties 12 that are sensed by bilayer-spanning proteins. The results obtained using the fluorescence-based ass...

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">	
		
		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>ANTS</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>A-350</td>
<td>&nbsp;</td>
<tr>
<td>gramicidin</td>
<td>&nbsp;</td>
<td>Sigma Chemical Co</td>
<td>G-5002</td>
<td>&nbsp;</td>
<tr>
<td>1,2-dierucoyl-sn-glycero-3-phosphocholine</td>
<td>&nbsp;</td>
<td>Avanti Polar Lipids</td>
<td>850398C</td>
<td>&nbsp;</td>
<tr>
<td>Mini-Extruder kit</td>
<td>&nbsp;</td>
<td>Avanti Polar Lipids</td>
<td>610000</td>
<td>&nbsp;</td>
<tr>
<td>PD-10 Desalting column</td>
<td>&nbsp;</td>
<td>Sigma-Aldrich Made by GE Healthcare</td>
<td>54805</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

gramicidin-based fluorescence assay; for determining small molecules potential for modifying lipid bilayer properties

Many drugs and other small molecules used to modulate biological function are amphiphiles that adsorb at the bilayer/solution interface and thereby alter lipid bilayer properties. This is important because membrane proteins are energetically coupled to their host bilayer by hydrophobic interactions. Changes in bilayer properties thus alter membrane protein function, which provides an indirect way for amphiphiles to modulate protein function and a possible mechanism for "off-target" drug effects. We have previously developed an electrophysiological assay for detecting changes in lipid bilayer properties using linear gramicidin channels as probes 3,12. Gramicidin channels are mini-proteins formed by the transbilayer dimerization of two non-conducting subunits. They are sensitive to changes in their membrane environment, which makes them powerful probes for monitoring changes in lipid bilayer properties as sensed by bilayer spanning proteins. We now demonstrate a fluorescence assay for detecting changes in bilayer properties using the same channels as probes. The assay is based on measuring the time-course of fluorescence quenching from fluorophore-loaded large unilamellar vesicles due to the entry of a quencher through the gramicidin channels. We use the fluorescence indicator/quencher pair 8-aminonaphthalene-1,3,6-trisulfonate (ANTS)/Tl+ that has been successfully used in other fluorescence quenching assays 5,13. Tl+ permeates the lipid bilayer slowly 8 but passes readily through conducting gramicidin channels 1,14. The method is scalable and suitable for both mechanistic studies and high-throughput screening of small molecules for bilayer-perturbing, and potential "off-target", effects. We find that results using this method are in good agreement with previous electrophysiological results 12.

Watch this Scientific Journal Video about Gramicidin-based Fluorescence Assay; for Determining Small Molecules Potential for Modifying Lipid Bilayer Properties at JoVE.com

Gramicidin-based Fluorescence Assay; for Determining Small Molecules Potential for Modifying Lipid Bilayer Properties

We introduce a fast fluorescence-based assay that monitors the rate of fluorescence quenching as a measure of gramicidin channel activity. The gramicidin channels are used as molecular force transducers to monitor changes in lipid bilayer properties as sensed by bilayer spanning proteins.

Many drugs and other small molecules used to modulate biological function are amphiphiles that adsorb at the bilayer/solution interface and thereby alter ...

gramicidin-based-fluorescence-assay-for-determining-small-molecules

Research

JoVE Journal

Biology

12.7K 조회수.  Weill Cornell Medical College. 우리는 그램이시딘 채널 활동의 조치로 형광 담금질의 속도를 모니터링 빠른 형광 기반의 분석을 소개합니다. 그램이시딘 채널 지질 이중층 속성의 변화로 이중층 스패닝 단백질에 의해 감지를 모니터링하는 분자 힘 변환기로 사용됩니다.