Given the task definition and input, reply with output. In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.

The aldehyde inhibitor Z-Ala-Ala-Phe-CHO has been synthesized and shown by 13 C-NMR to react with the active site serine hydroxyl group of alpha-chymotrypsin to form two diastereomeric hemiacetals. For both hemiacetals oxyanion formation occurs with a pK a value of~7 showing that chymotrypsin reduces the oxyanion pK a values by 5.6 pK a units and stabilizes the oxyanions of both diastereoisomers by~32 kJ mol 1 . As pH has only a small effect on binding we conclude that oxyanion formation does not have a significant effect on binding the aldehyde inhibitor. By comparing the binding of Z-Ala-Ala-Phe-CHO with that of Z-Ala-Ala-Phe-H we estimate that the aldehyde group increases binding~100 fold. At pH 7.2 the effective molarity of the active site serine hydroxy group is~6000 which is~7 less effective than with the corresponding glyoxal inhibitor. Using 1 H-NMR we have shown that at both 4 and 25C the histidine pK a is~7.3 in free chymotrypsin and it is raised to~8 when Z-Ala-Ala-Phe-CHO is bound. We conclude that oxyanion formation only has a minor role in raising the histidine pK a and that the aldehyde hydrogen must be replaced by a larger group to raise the histidine pK a N 10 and give stereospecific formation of tetrahedral intermediates. The results show that a large increase in the pK a of the active site histidine is not needed for the active site serine hydroxyl group to have an effective molarity of 6000.
Hemiacetal stabilization in a chymotrypsin inhibitor complex and the reactivity of the hydroxyl group of the catalytic serine residue of chymotrypsin