lecture 3 - 3-1MCB354Lecture 3Reading in Lehninger:Chapter...

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Unformatted text preview: 3-1MCB354Lecture 3Reading in Lehninger:Chapter 3, pp. 81-89 Ionization of Amino AcidsPeptides3-2Ionization of Amino AcidsH+H+fully protonated:net charge:+1-1At pH 2.34, equal mixture of+H3N-CH2-COOH (+1) and+H3N-CH2-COO-(),so net +ve charge = 0.5Titration of glycine3-3Chemical environment affects pKa3-4net charge:+1-1-2H+H+H+Titration ofglutamic acid3-5pKas governing formationof the +1and -1formsgovern formation ofuncharged glutamate, andpI=2.19 + 4.252= 3.22H+net charge:+2+1-1H+H+Titration of histidine3-63-7peptide bondUnfavorable, becauseOH-poor leaving group3-8Formation of a peptide bondCondensationHydrolysisSer-Gly-Tyr-Ala-Leu(SGYAL) a pentapeptideN-terminusC-terminus3-9R-groups can ionize, and contributeto the acid-base behavior of thepeptide.But, interactions with other R-groupsand loss of the charges from the s-amino and -carboxyl groups canaffect R-group pKa....
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This note was uploaded on 01/29/2012 for the course MCB 354 taught by Professor Spees during the Spring '09 term at University of Illinois, Urbana Champaign.

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lecture 3 - 3-1MCB354Lecture 3Reading in Lehninger:Chapter...

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