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<TITLE>Re: [RASMB] frictional ratio</TITLE>
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<BLOCKQUOTE><B>Seasonal greetings, Holger, and to all RASMBers!<BR>
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There is actually a simple formula which predicts the frictional ratio of a protein in random coil form:<BR>
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f/f0 = {(A*n^b/ M0)/(1.25*vbar)}^1/3<BR>
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where n = number of aa residues in the protein, M0 is its <I>average</I> 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). <BR>
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The formal proof of the above equation, together with a spreadsheet which computes f/f0 for you are available from here, by simple request.<BR>
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A nice little Christmas puzzle!<BR>
<BR>
Arthur<BR>
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*******************************************************<BR>
Arthur J Rowe<BR>
Professor of Biomolecular Technology<BR>
NCMH Business Centre<BR>
University of Nottingham<BR>
School of Biosciences<BR>
Sutton Bonington<BR>
Leicestershire LE12 5RD UK<BR>
<BR>
Tel: +44 (0)115 951 6156<BR>
+44 (0)116 271 4502<BR>
Fax: +44 (0)115 951 6157<BR>
email: arthur.rowe@nottingham.ac.uk<BR>
Web: www.nottingham.ac.uk/ncmh/business<BR>
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<BLOCKQUOTE><TT>Hi everybody,<BR>
<BR>
I remember that the frictional ratio for a fully unfolded polypeptide <BR>
chain is around 2.3; but I can't remember the actual reference. Any hints?<BR>
<BR>
A happy, peaceful and healthy 2006 to all!<BR>
<BR>
Holger<BR>
<BR>
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