From: Walter Stafford <STAFFORD@bbri.harvard.edu> To : rasmb@bbri.harvard.edu Date: Sat, 30 May 1998 18:40:50 -0400 (EDT)

Dear RASMBers I have just been informed taht there is a serious typo in one of the readme files for dcdt. It concerns the equation for computing D from the g(s*) curve. The term in square barckets in the numerator shoudl be squared That section should read : The g(s*) vs. s* curves are essentially gaussian; The standand deviation, sigma, can be related to the diffusion coefficient: D = [ sigma * w^2*t * Rm ]^2/[2*t] <- error was in this eq'n where Rm, (w^2*t) and t are given in the header of the output file, Rm is the radius of the meniscus and sigma is defined by: g(s) = A * exp[ -0.5 * ( (s_peak - s)/(sigma) )^2 ] Use this equation for fitting to get sigma. The values of s and D can be substituted into the Svedberg equation to get the molecular weight.: M = [ R*T*s_peak ]/[ D*(1-vBar*rho)*w^2*t ] Sorry for any inconvenience that may have caused. Walter Stafford

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