From owner-biophysics@net.bio.net Sun Apr 17 23:00:00 1994
Newsgroups: bionet.biophysics
Path: biosci!agate!howland.reston.ans.net!torn!mcshub!muss.cis.mcmaster.ca!u9011500
From: u9011500@muss.cis.mcmaster.ca (C.T. Lemay)
Subject: Re: Model membranes/Domains/Lipid-Protein..
Message-ID: <1994Apr18.044123.17430@muss.cis.mcmaster.ca>
Organization: McMaster University, Hamilton, Ontario, Canada
References: <1994Apr12.201344.1@leif>
Date: Mon, 18 Apr 1994 04:41:23 GMT
Lines: 46

In article <1994Apr12.201344.1@leif> knag@kean.ucs.mun.ca writes:
>MODEL BIOLOGICAL MEMBRANES:: DOMAINS
>...
>2] Are there any techniques available to observe bilayer domains? Does 
>biological membrane have domains?
>
	Although i haven't experimented much on visual observation of 
bilayer domains, Dr. Richard Epand, me, and another student experimented 
with finding segregation of domains in lipids using DSC (Differential 
Scanning Calorimetry).  The solidus and liquidus lines on a phase diagram 
are parallel and almost horizontal when there are gel/Lc domains (ie., 
the bilayer melts in chunks ... or so i understand it in my simple 
mind).  Although this is well known, we were trying to find liquid/liquid 
domain segregation, also by using DSC.  We did not have all that much 
luck.

	The reason we were interested in such domains is because we
thought that they might be relevant to viral fusion.  In a previous study
with aliphatic alcohols, we found that eicosanol (20 carbon alcohol)
stimulated FLU fusion and also gave a liquid to hexagonal phase transition
profile (again, by DSC) that indicated liquid/liquid inhomogeneities.  We
thought the increased fusion and phase seperation might be physically
related.  Unfortunately, it is difficult to find lipid systems which
exhibit similar behaviour, so i was unable to conclusively disprove or
prove our hypothesis.  (I was unable to demonstrate any rise in fusion 
due to solid/liquid phase separation).  Any suggestions are welcome (even 
if any of you know of model systems which display liquid/liquid 
inhomogeneity at reasonable temperatures ...)

>4] When model membranes undergo thermal transition (gel to liquid 
>crystalline transitions or LE to LC) can the cooperative process be 
>visualized? I have not yet seen any references in this regard.
>

It would indeed be fascinating to actually _*see*_ the transition! 

This is a very interesting thread, let the discussion continue ....

						Chris Lemay


-- 
------------------------------------------------------------------------
Christian T. Y. Lemay		| Biochemistry Dept., McMaster Univ.
lemay@fhs.csu.mcmaster.ca  OR	| Hamilton, Ontario, CANADA    L8N 3Z5
u9011500@muss.cis.mcmaster.ca	| Telephone & Fax: (905) 527-3752

.