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<DIV><FONT face=Arial size=2>Dear colleauges, lets come back to
reality</FONT></DIV>
<DIV><FONT face=Arial size=2>At least for new-comers , but not only for
them, the subject of predicting or better , calculating the time to achieve
equilibrium makes no / or only very little sense , since as I
belive that every one of us use the</FONT></DIV>
<DIV><FONT face=Arial size=2>"overspeed procedure" discribed by Hexner,
Radford and Beams PNAS (1961), 47,1848 that reduces time to achieve equilibrium
to 50% or more. If so, I ask myself what means time to
equilibrium ? from the time rotor speed is achieved and not yet a
concentration gradient is established, or a steep graient at both
solution column ends? all non -sense ! I agree that for polydispersed or
selfassociating systems </FONT></DIV>
<DIV><FONT face=Arial size=2>using an overspeed procedure is difficult (and
dangrous especially it some parts are not reversible), but not less
difficult as to calculate time to equilibrium as you suggested of a non
monodispersed systeme.</FONT></DIV>
<DIV><FONT face=Arial size=2>In FRACTION N° 1 1967 issued by
Beckman Instruments ( may be based on the same equation</FONT></DIV>
<DIV><FONT face=Arial size=2>that Walter Stafford mentioned recently)
K.E Van Holde discribed a formula where the time depends on
Diffusion ! and here again to new-comers. If at all making the <U>exercise</U>
to calculate time to equilibrium.</FONT></DIV>
<DIV><FONT face=Arial size=2>It is to use D<FONT size=1>obs </FONT><FONT
size=2>and not D<FONT size=1>20w</FONT> that is correected for
Viscosity of water. There may be a huge
difference</FONT></FONT></DIV>
<DIV><FONT face=Arial size=2>between the two Diffusion values if per
example you use sucrose in the buffer as I do measuring </FONT></DIV>
<DIV><FONT face=Arial size=2>membrane proteins. The density has no
influence for Diffusion only the viscosity of the
solvent.</FONT></DIV>
<DIV><FONT face=Arial size=2>yours....ariel</FONT></DIV>
<DIV><FONT face=Arial size=2>ariel.lustig@bluewin.ch</FONT></DIV></BODY></HTML>