The rate of sedimentation of a recently isolated protein was monitored at 20C and with a

Chapter 19, Problem 19.28

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The rate of sedimentation of a recently isolated protein was monitored at \(20^{\circ} \mathrm{C}\) and with a rotor speed of 50000 r.p.m. The boundary receded as follows:

\(\begin{array}{llllllll}t / \mathrm{s} & 0 & 300 & 600 & 900 & 1200 & 1500 & 1800 \\ r / \mathrm{cm} & 6.127 & 6.153 & 6.179 & 6.206 & 6.232 & 6.258 & 6.284\end{array}\)

Calculate the sedimentation constant and the molar mass of the protein on the basis that its partial specific volume is \(0.728 \mathrm{~cm}^3 \mathrm{~g}^{-1}\) and its diffusion coefficient is \(7.62 \times 10^{-11} \mathrm{~m}^2 \mathrm{~s}^{-1}\) at \(20^{\circ} \mathrm{C}\), the density of the solution then being \(0.9981 \mathrm{~g} \mathrm{~cm}^{-3}\). Suggest a shape for the protein given that the viscosity of the solution is \(1.00 \times 10^{-3} \mathrm{~kg} \mathrm{~m}^{-1} \mathrm{~s}^{-1}\) at \(20^{\circ} \mathrm{C}\).