[RASMB] peptide in DMSO (2)

[Harding Stephen]

Dear Andrew/Tom/Christine & co.
Thanks for this.
Just to point out that we used 12mm path length Kel-F cells, inert to
solvents like DMSO, GuHCl etc.  These were obtained in the old Model E
days, I'm not sure if Beckman still make them, if there is enough demand
maybe they will become available again?
However we've recently been using the new 20mm path length
centrepieces/cells made by Kristian Schilling's company in Potsdam.  The
cp's are aluminium and seem to be absolutely fine with DMSO.  But as Tom
said avoid the epon based centrepieces.

For carbohydrates dn/dc in 90% DMSO is approx half to a third that in
water, my guess is you will get a similar reduction for your peptide.
[I've looked in our Refractive Increment Data Book for anything on
proteins in DMSO but drawn a blank - but we did some AUC work some years
ago on gluten proteins in DMSO which never got written up, I will see if
I can dig this out]

The higher viscosity will slow things down considerably of course.  This
is not such a problem for amylopectin or amylose but for low molecular
weight peptides which will have small s-values in aqueous solvents this
may become  a major problem.

Kristian's excellent long path length cells - besides helping with the
starch work - have also made it possible at last to perform low speed
sedimentation equilibrium experiments at low concentration (nb in
aqueous solvents not DMSO) on polysaccharides and glycoconjugates,
enabling us to minimize the effects of the large non-ideality of these
substances (this is the first time we have been able to do this since
the Model E days with their wonderful 30mm path length centrepieces).   
Steve



Prof. Stephen Harding
University of Nottingham
Sutton Bonington
LE12 5RD, UK
http://www.nottingham.ac.uk/ncmh
  

-----Original Message-----
From: rasmb-bounces at rasmb.bbri.org [mailto:rasmb-bounces at rasmb.bbri.org]
On Behalf Of Leech, AP
Sent: 29 April 2008 15:06
To: rasmb at server1.bbri.org
Subject: Re: [RASMB] peptide in DMSO (2)

Sorry, I should have looked up the paper referenced by Arthur in the
archives before writing (Richard F Tester, Trushar Patel & Stephen E
Harding (2006) "Damaged starch characterisation by ultracentrifugation"
Carb Res 341 130-137). They used the interference optics with 8 mg/ml
starch solutions. Perhaps someone could comment on whether more dilute
solutions would be usable?

Andrew

Leech, AP wrote:
> Hi all,
> 
> Can I be the first to point out the viscosity of DMSO? I don't have 
> accurate figures but a quick web search implies >2 cp (twice that for 
> water) and variable with water content of the mixture. The other thing

> is, how will you detect your peptide?
> DMSO has quite a high UV absorbance so you might have difficulty if 
> your peptide doesn't have a decent extinction coefficient.
> (Has anyone ever tried the interference optics with DMSO?)
> 
> Andrew
> 
> Tom Laue wrote:
>> Hi Christine-
>> A couple of things to keep in mind-
>> The buoyancy of your peptide will be very small in 90% DMSO. See what

>> Steve, et al. used for the density at 90%.
>> DMSO is compressible, so you may need to include compressibility in 
>> your calculations (depending on rotor speed) Finally, DMSO is not 
>> entirely innocuous with epoxy. Your centerpieces may get softened.
>> Best wishes,
>> Tom
>>
>> Schar, Christine wrote:
>>> Hi
>>> I was hoping to get some advice about running a peptide (24mer, 2787

>>> Da) in 90% DMSO. I searched the archives and found Harding has used 
>>> 90% DMSO successfully for carbohydrates (not peptides) so I know my 
>>> centerpieces won't melt at least.
>>>
>>> The group I'm working with used this peptide in NMR.  They didn't 
>>> get a good signal in PBS so they switched to DMSO.  They're seeing 
>>> NOEs and they are interested in knowing if their peptide aggregates.

>>> Another possibility is it forms micelles.  Is it feasible to try a 
>>> run with this peptide in DMSO?  Are there any special 
>>> considerations?
>>>
>>> Thanks for any help.
>>> Christine Schar
>>>
>>>
>>> _______________________________________________
>>> RASMB mailing list
>>> RASMB at rasmb.bbri.org
>>> http://rasmb.bbri.org/mailman/listinfo/rasmb
>>>
>>>   
>>
> 

-- 
Dr Andrew Leech                   *  Laboratory Manager
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