Evaluation of diffusion coefficients by means of an approximate steady-state condition in sedimentation velocity distributions

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• 作者：David J. Scott^a ; ^b ; ^{david.scott@nottingham.ac.uk" class="auth_mail" title="E-mail the corresponding author} ; Stephen E. Harding^a ; Donald J. Winzor^c
• 关键词：Diffusion coefficient ; Sedimentation velocity ; Ultracentrifugation
• 刊名：Analytical Biochemistry
• 出版年：2015
• 出版时间：1 December 2015
• 年：2015
• 卷：490
• 期：Complete
• 页码：20-25
• 全文大小：1072 K

文摘

This investigation examined the feasibility of manipulating the rotor speed in sedimentation velocity experiments to spontaneously generate an approximate steady-state condition where the extent of diffusional spreading is matched exactly by the boundary sharpening arising from negative s–c dependence. Simulated sedimentation velocity distributions based on the sedimentation characteristics for a purified mucin preparation were used to illustrate a simple procedure for determining the diffusion coefficient from such steady-state distributions in situations where the concentration dependence of the sedimentation coefficient, s = s⁰/(1 + Kc), was quantified in terms of the limiting sedimentation coefficient as c → 0 (s⁰) and the concentration coefficient (K). Those simulations established that spontaneous generation of the approximate steady state could well be a feature of sedimentation velocity distributions for many unstructured polymer systems because the requirement that Kc_o蠅²s⁰/D be between 46 and 183 cm⁻² is not unduly restrictive. Although spontaneous generation of the approximate steady state is also a theoretical prediction for structured macromolecular solutes exhibiting linear concentration dependence of the sedimentation coefficient, s = s⁰(1 − kc), the required value of k is far too large for any practical advantage to be taken of this approach with globular proteins.