Changing activity of ribonuclease A during adsorption: a molecular explanation.
The activity of ribonuclease A (RNase A) during adsorption onto molecular smooth mica increases from 16% to 78% in a period of 24 h when compared to its activity in free solution at pH 5 and 20 +/- 0.5 degrees C. From electropotential plots, the tertiary structure of RNase A, the characteristics of the mica surface, and direct measurements of the intermolecular forces between two adsorbed enzyme layers, a molecular explanation is offered for the changing activity with time. Initially, the RNase A molecules lie flat-on the mica with their smallest axis perpendicular to and their active site facing the surface. As adsorption proceeds, the molecules slowly reorient until at long times they lie end-on with their largest axis perpendicular to the surface and their active site partially exposed to the free solution. A translational diffusion process is indicated for the phase transition and molecular reorientation of the RNase A molecules.
Lee
C S
CS
Department of Chemical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180-3590.
Belfort
G
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D000327:Adsorption; D000538:Aluminum Silicates; D004563:Electrochemistry; D007700:Kinetics; D008958:Models, Molecular; D011487:Protein Conformation; D012259:Ribonuclease, Pancreatic / Q000378:metabolism*
D000538:Aluminum Silicates; D012259:Ribonuclease, Pancreatic; C011934:mica