[RASMB] frictional ratio

[Arthur Rowe]

Seasonal greetings, Holger, and to all RASMBers!

There is actually a simple formula which predicts the frictional ratio of a
protein in random coil form:

f/f0 = {(A*n^b/ M0)/(1.25*vbar)}^1/3

where n = number of aa residues in the protein, M0 is its average residue
weight, n is the number of residues, vbar is the partial specific volume,
and A and b are empirically determinable constants, estimated to be A = 77.3
and b = 0.666 for proteins (Tanford,C. Kawaharas, K. & Laopanje, S. (1967)
JACS 89 729). 

The formal proof of the above equation, together with a spreadsheet which
computes f/f0 for you are available from here, by simple request.

A nice little Christmas puzzle!

Arthur


--
*******************************************************
Arthur J Rowe
Professor of Biomolecular Technology
NCMH Business Centre
University of Nottingham
School of Biosciences
Sutton Bonington
Leicestershire LE12 5RD   UK

Tel:        +44 (0)115 951 6156
           +44 (0)116 271 4502
Fax:        +44 (0)115 951 6157
email:      arthur.rowe at nottingham.ac.uk
Web:        www.nottingham.ac.uk/ncmh/business
*******************************************************



Hi everybody,

I remember that the frictional ratio for a fully unfolded polypeptide
chain is around 2.3; but I can't remember the actual reference. Any hints?

A happy, peaceful and healthy 2006 to all!

Holger

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