Conformational integrity of human alpha-thrombin

Site-Specific and Trigger-Activated Modification of Proteins by Means of Catalytic Hemin/G-quadruplex DNAzyme Nanostructures

Catalytic nanostructures have the potency to mimic enzymatic features. In this paper, we show that the complex between hemin and G-quadruplex DNA efficiently catalyzes the modification of proteins with N-methyl luminol derivatives. Final conversions are reached within 15–30 min, and LC-MS analysis of tryptic digests of the proteins shows that the reaction proceeds with chemoselectivity for electron-rich aromatic residues (Tyr ≫ Trp), and the site-specificity of the modification depends on the sequence and secondary structure folding of the G-quadruplex nanostructure. Furthermore, the modification can be applied on proteins with different biomedical functions, and the nanostructure can be designed to contain a regulatory element in order to regulate protein modification by an external stimulus.

High-performance affinity chromatography of human thrombin on modified polystyrene resins

Cross-linked polystyrenes modified with L-arginyl methyl ester mimic the binding site of antithrombin III and thrombin substrates. They can be used as stationary phases in high-performance affinity chromatography of thrombin. Under isocratic conditions, thrombin is strongly adsorbed on the resins when the sodium chloride concentration is lower than 0.5 M. The bound enzyme can be selectively desorbed when the salt concentration is raised to about 1.2 M. With a linear salt gradient, the specific elution of thrombin can be effected with a high recovery of its enzymatic activity. The decomposition products of thrombin, when treated with sodium dodecyl sulphate, are not retained by the stationary phase. The effects of the flow-rate and salt gradient slope on the adsorption and desorption of alpha-thrombin demonstrate the importance of kinetic parameters.