COMPLEXATION OF TRYPSIN AND ALCOHOL-DEHYDROGENASE WITH POLY(DIALLYLDIMETHYLAMMONIUM CHLORIDE)

Complexation of alcohol dehydrogenase (ADH) and trypsin with poly(dial lyldimethyl-ammonium chloride) (PDADMAC) in dilute electrolyte solutio n was studied by turbidimetric titration, quasi-elastic light scatteri ng (QELS), and electrophoretic light scattering (ELS). Both QELS and t urbidimetric titration show that PDADMAC forms complexes with ADH and trypsin in 0.01M NaCl solution at pH greater than or equal to 6.8 and pH greater than or equal to 9.2, respectively. These complexes take th e form of stable coacervates in 0.01M, pH 11.0, phosphate buffer solut ion. QELS shows sizes of 400 and 315 nm for the coacervates of ADH-PDM DAAC and trypsin-PDMDAAC, respectively, while ELS reveals that these c oacervates carry a net positive charge. Activity measurements show tha t both ADH and trypsin are enzymatically active in their coacervated s tates. Complexation of trypsin and PDADMAC was also studied by fluores cence in 0.01M, pH 11.0, phosphate buffer, and the protein emission wa s found to be quenched by complexation. The fluorescence quenching dat a show that trypsin retains its three-dimensional structure in the com plex. These and other results are consistent with the quenching of the two tryptophans on the protein surface, but not the interior ones. (C ) 1997 John Wiley & Sons, Inc.