[RASMB] Oligomerization of small peptides (20-30 aa)...

[Lake Paul]

Alternative to ESI methods:

Jeffrey A. Crank, Daniel W. Armstrong, Towards a Second Generation of Ionic
Liquid Matrices (ILMs) for MALDI-MS of Peptides, Proteins, and
Carbohydrates, Journal of the American Society for Mass Spectrometry, Volume
20, Issue 10, October 2009, Pages 1790-1800

The major issue here is the mass spec buffer compatibility and the stability
of the complex in that buffer. You will have to play with the ratios of
analyte to matrix to get a good signal. I would NOT go quantifying anything
you see in the MALDI spectra without some type of extensive isotopic
labeling. Again I use this to compliment the AUC results and to help in the
fitting of the data.

Lake

-----Original Message-----
From: rasmb-bounces at rasmb.bbri.org [mailto:rasmb-bounces at rasmb.bbri.org] On
Behalf Of Susumu UCHIYAMA
Sent: Wednesday, February 10, 2010 10:21 AM
To: Schoenfeld, Hans-J.
Cc: 'rasmb at rasmb.bbri.org'
Subject: Re: [RASMB] Oligomerization of small peptides (20-30 aa)...

Hi Hans-Joachim,

I have experienced a lot of tricky results when I was in Carol
Robinsons's lab and also my recent studies.
In MS, ionization efficiency depends on the size of oligomer and
electrostatic states of protein surface.
Also, other factors such as the method of spraying protein solution and
timing of buffer exchange for MS measurement influence the ionization
efficiency and charge state of proteins.
In addition, the sensitivity of the detector (MCP) does not show linear
response to the amount of charged proteins.
Thus, under non-denaturing condition, you can detect large oligomers but
rather qualitative compared to AUC.
However, resolution on molecular mass is extremely higher than AUC
(molecular weight in AUC).

Best regards, Susumu

-- 
////////////////////////////////////////////////////////
Susumu Uchiyama, Ph. D., Assistant Professor
Department of Biotechnology,
Graduate School of Engineering, Osaka University
2-1 Yamadaoka, Suita 565-0871, Osaka, Japan
TEL: 81-6-6879-4215
FAX: 81-6-6879-7442
E-mai : suchi at bio.eng.osaka-u.ac.jp
http://www.bio.eng.osaka-u.ac.jp/cl/biocladm/E_top.html
////////////////////////////////////////////////////////




> Dear RASMB colleagues,
> the methods of choice to characterize peptide oligomerization in
> solution so far in my view were AUC in equilibrium mode or static
> light scattering methods...
> Recently, I heart about attempts to investigate peptide
> oligomerization as function of pH, buffer composition, etc. by
> electron spray mass spectroscopy. Are there opinions around about how
> MS methods in doing that compare to the more classical methods as
> mentioned above. I can hardly believe how MS could work without
> significantly influencing weak interactions or change equilibria...
> Thanks for any comment on that topic.
> Best regards,
> Hans-Joachim.
> Ps: also grateful for any literature of review references on this topic...
> ============================================
> Dr. Hans-Joachim Scho"nfeld
> F. Hoffmann-La Roche Inc.
> Preclinical research, B93/5.44
> CH-4070 Basel
> Switzerland
> Tel. (+41) 61 688 28 95
> Fax. (+41) 61 688 90 60
> _mailto:hans-j.schoenfeld at roche.com_
> ------------------------------------------------------------------------
>
> _______________________________________________
> RASMB mailing list
> RASMB at rasmb.bbri.org
> http://rasmb.bbri.org/cgi-bin/mailman/listinfo/rasmb
>   

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