title: A new arylating agent, 2-carboxy-4,6-dinitrochlorobenzene. Reaction with model compounds and bovine pancreatic ribonuclease.
abstract: The reagent 2-carboxy-4,6-dinitrochlorobenzene (CDNCB) reacts with the imino, amino and sulfhydryl groups of model compounds. At pH 8.2, sulfhydryl groups react much faster than do amines. N alpha-Acetylhistidine, N alpha-acetyltyrosine and N alpha-acetyltryptophan do not react. Poly(L-Lysine) and poly(DL-lysine) react about 50 times as fast as does N alpha-acetyllysine. A dichloroanalog, 6-carboxy-2,4-dinitro-1,3-dichlorobenzene, shows stepwise reactivity with amines. With bovine pancreatic ribonuclease, which contains no sulfhydryl, CDNCB reacts preferentially with the epsilon-amino of Lys-41 at 450 times the rate with the epsilon-amino of N alpha-acetyllysine. The preferential reactivity at Lys-41 is discussed in relation to the pK of Ly-41, the cationic character of the active site cleft, and the mechanism of RNAase action on substrates.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002417:Cattle; D003461:Crystallography; D004137:Dinitrochlorobenzene / Q000031:analogs & derivatives; D004220:Disulfides; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007202:Indicators and Reagents; D008956:Models, Chemical; D009578:Nitrobenzenes / Q000031:analogs & derivatives; D010179:Pancreas / Q000201:enzymology; D010455:Peptides / Q000032:analysis; D012260:Ribonucleases / Q000032:analysis / Q000037:antagonists & inhibitors; D013997:Time Factors; D014357:Trypsin / Q000494:pharmacology; D014961:X-Ray Diffraction
chemical_list: D000596:Amino Acids; D004137:Dinitrochlorobenzene; D004220:Disulfides; D007202:Indicators and Reagents; D009578:Nitrobenzenes; D010455:Peptides; D012260:Ribonucleases; D014357:Trypsin