The rate of sedimentation of a recently isolated protein was monitored at 20°C and with a rotor speed of 50 000 r.p.m. The boundary receded as follows: 

Calculate the sedimentation constant and the molar mass of the protein on the basis that its partial specific volume is 0.728 cm³ g⁻¹ and its diffusion coefficient is 7.62 × 10⁻¹¹ m² s⁻¹ at 20°C, the density of the solution then being 0.9981 g cm⁻³. Suggest a shape for the protein given that the viscosity of the solution is 1.00 × 10⁻³ kg m⁻¹ s⁻¹ at 20°C.

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t/s 0 r/cm 6.127 300 600 6.153 6.179 900 6.206 1200 1500 1800 6.232 6.258 6.284