Solution behavior, circular dichroism and 220 MHz PMR studies of the bovine myelin basic protein

Bovine myelin basic protein has been investigated with regard to its solution behavior, circular dichroism and 220 MHz PMR spectral properties.At pH 4.8 [gamma]/2 = 0.1 acetate buffer, light scattering yielded a Mr of 17 700 and a virial coefficient of 1.0[middle dot]10-4 mol[middle dot]ml/g2. Above pH 7.0 the protein was found to aggregate to higher mol. wt species.Sedimentation experiments at pH 4.8 yielded s[deg]20,w of 1.27 S at [gamma]/2 = 0.1 and 1.46 S at [gamma]/2 = 0.35. The diffusion coefficient determined from ultracentrifugal experiments was 7.25[middle dot]10-7 cm2/s at [gamma]/2 = 0.1 and 0.35. The value of [function of (italic small f)]/[function of (italic small f)]0 from diffusion at pH 4.8 and [gamma]/2 = 0.35 was 1.64, corresponding to an axial ratio of 11 to 1. The radius of gyration was calculated as 4.28 nm and the root mean square end to end distance was 10.5 nm. At pH 9.0, [gamma]/2 = 0.1, s[deg]20,w was 1.71 S and D[deg]20,w was estimated at 7.4[middle dot]10-7 cm2/s. The behavior at pH 9.0 reverted to the behavior at pH 4.8 when the pH was readjusted. The E1cm1% = 5.64 at 276.4 nm and 225 at 196 nm.Titration of the protein with trifluoroethanol elicited three distinct regions of conformational stability having increasing helical content as the mol fraction of trifluoroethanol increased.The results of the present study have permitted some comparison of analogous properties and conformational behavior with the basic membrane protein cytochrome c.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21990/1/0000400.pd

Bestimmung des Molekulargewichtes der 20-β-Hydroxy-steroid-dehydrogenase

The enzyme 20-β-Hydroxy-steroid-dehydrogenase obtained from the culture of Streptomyces hydrogenans and dissolved in 0.05 M Tris puffer, pH 7.3, has been investigated by means of a ultracentrifuge at 20 °C. The sedimentation- as well as the diffusion-coefficients obtained from various solutions at different concentrations were extrapolated to the concentration c = 0. The resulting zero-value for the sedimentation coefficient is s0 = 6.64 s and for the diffusion coefficient is D0 = 5.51 × 10-7 cm2/sec. Supposing the partial specific volume of the enzyme under consideration analogously to other similar proteins is V+=0.749 ml/g, the molecular weight has been estimated as M = 118 400