Lecture 18 - Wednesday, October 4, 2006 Lecture 18...

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Wednesday, October 4, 2006 Lecture 18 Announcements: Have a prelim conflict for Thursday 10/19? Meet briefly after class today to determine the date/time for the make-up prelim. (This meeting has now occurred. The make-up exam will be Saturday 10/21 from 3 - 5:30PM. Room to be announced. Send Prof. F. an e-mail! You MUST send an e-mail, describe your conflict, then you get onto “the list”) Monday's lecture: @ concept of the ‘efficient” enzyme: not the large turnover number (k cat ), but instead, the lowering of the TS G o compared with the uncatalyzed rxn ¸ use of enzyme inhibition X vary pH to find pKa’s of AA at the enzyme active site Xuse competitive inhibitor to bind to E where S binds Today's lecture: chymotrypsin mechanism, step-by-step In the discussion that follows, refer to LG pp. 124-131. p. 124 Some conventions for talking about enzyme mechanisms: Each drawn structure of substrate, intermediates, and products, has “some” stability, hence can be drawn as a low point on a G o vs progress of rxn diagram. Between these intermediates are higher free energy states, the transitions states between intermediates. The highest free energy state is the overall TS of the rxn. Catalysis happens between the intermediate states. A convention is to show the electron flows on a diagram in order to represent what is going to happen in the next step, leading to the next intermediate. Step 1.
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Lecture 18 - Wednesday, October 4, 2006 Lecture 18...

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