Evidence for multiple forms of p-trifluoromethylbenzenesulfonyl-α-chymotrypsin

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Abstract
P-Trifluoromethylbenzenesulfonyl-.alpha.-chymotrypsin, an analog of tosylchymotrypsin, was prepared and was stable enough to permit fluorine NMR experiments. Up to 4 distinct trifluoromethyl resonances can be observed for the modified protein at 94.1 MHz, even when the enzyme derivative is prepared from protein which was purified by several methods. The resonances observed appear to represent proteins which are grossly similar as regards molecular size and the ability to bind and hydrolyze substrates, but distinctive enough in the active-site region to produce appreciable chemical-shift effects.