Boundary centrifugation is performed at an angular velocity of 40,000. rpm to determine the sedimentation coefficient of cytochrome c (M = 13,400 g mol⁻¹) in water at 20°C (ρ = 0.998 g cm⁻³,η = 1.002 cP). The following data are obtained on the position of the boundary layer as a function of time:

Time (h)…………………x_b(cm)

0…………………………….4.00

2.5………………………… 4.11

5.2………………………….4.23

12.3………………………..4.57

19.1…………………………4.91

a. What is the sedimentation coefficient for cytochrome c under these conditions?

b. The specific volume of cytochrome c is 0.728 cm g⁻¹. Estimate the size of cytochrome c.