CHL-770 FROM GREEN BACTERIA 427 



SEDIMENTATION COEFFICIENT AND MOLECULAR WEIGHT 



The sedimentation coefficients at four different protein concentra- 

 tions were measured from the sedimentation velocity in the Spinco 

 analytical ultracentrifuge, Model E, The chlorophyll-protein was 

 dialyzed against 0.2 iV NaCl in 0.01 M Tris, pH 8.0, and sedimented at 

 59,780 rpm in a double-sector cell. The Schlieren pattern (see Fig, 4) 

 was Dhotographed at 8-minute intervals, and the distance of the peak 



Fig. 4. Schlieren pattern of the descending boundary in the double-sector cell 



after approximately 30 minutes of centrifugation at 59,780 rpm. A 

 cm-1, t - 25.6°C. 



809 



31.4 



from the center of rotation was plotted versus time on a semilog 

 scale. The sedimentation coefficient was calculated from the slope of 

 the best straight line fitted to the data according to the usual equation 

 and then corrected for solvent viscosity and temperature (9). The 

 corrected values for S2o w ''■^ '^ concentrations of material are shown 

 in Fig. 5, The linear extrapolation to zero concentration was fitted to 

 the experimental points by the method of least squares. In spite of the 



