Effect of ionic strength on the binding of alpha-chymotrypsin to nanoparticle receptors.
Negatively charged carboxylate-functionalized mixed monolayer protected clusters (MMPCs) effectively bind and inhibit alpha-chymotrypsin based on complementary electrostatic surface recognition. We demonstrate that this binding can be disrupted by varying the ionic strength of the medium. Enzyme activity in the presence of MMPCs increases from 5% to 97% of native activity as salt concentration is increased from 0 to 1.5 M. Variation of ionic strengths after complete binding over 13 h results only in a modest restoration of enzymatic activity (< 35%). The conformation of chymotrypsin was characterized using circular dichroism and fluorescence spectroscopy, correlating structure with enzymatic activity. This work provides a useful insight of the electrostatic influence on protein--MMPC interactions and can be applied toward MMPC-based controlled release of proteins in vivo.
Verma
Ayush
A
Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Simard
Joseph M
JM
Rotello
Vincent M
VM
D000818:Animals; D002264:Carboxylic Acids; D002417:Cattle; D002918:Chymotrypsin / Q000737:chemistry* / Q000378:metabolism; D006046:Gold; D049329:Nanostructures / Q000737:chemistry*; D009994:Osmolar Concentration; D011485:Protein Binding; D011487:Protein Conformation; D055672:Static Electricity
D002264:Carboxylic Acids; D006046:Gold; D002918:Chymotrypsin; C117608:alpha-chymotrypsin