Protein Interactions in Solution Characterized by Light and Neutron Scattering: Comparison of Lysozyme and Chymotrypsinogen

 


Virial coefficient and crystallization patterns for chymotrypsinogen


 

Chymotrypsinogen virial coefficients
 

 

Chymotrypsinogen SANS nonaggregated

 
SANS measurements on chymotrypsinogen at pH 3 and two different electrolyte concentrations. The solid curve is the form factor function fitted by approximating the protein shape by a sphere. In agreement with the SLS data, positive deviations from this curve in the low q region indicate attractive interactions and vice versa.

 

Chymotrypsinogen SANS aggregated
SANS chymotrypsinogen data at pH 7. As the sample changes with time, the three sets of data are shown as separate plots. The data at pH 3 and I = 0.3 M are also shown for comparison.

 
 

Results of centrifugal crystallization experiments with chymotrypsinogen.

pH

Electrolyte conc., M

Crystals formed

Stable *

Rotate polarized light

3

0.005

Yes

No

Yes

3

0.3

No

-

-

5.25

0.005

Yes

Yes

Yes

5.25

0.3

Yes

Yes

Yes

7

0.005

Yes

Yes

No

7

0.3

No

-

-

* Insoluble in the remaining 0.5 ml of concentrated mother liquor

 

A variety of crystalline modifications are formed under the action of the external field, indicating the importance of both the interactions and the kinetic effects. The data indicate that the value of pH 5.2 (where as shown by the virial coefficient pattern the repulsive and attractive electrostatics are balanced) may be particularly suitable for crystallization.

 


    © Copyright O. D. Velev et al. 1999

 

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