BIS102 Hilt W03 MT1

BIS102 Hilt W03 MT1 - 1 of 2 BIS 102 Winter, 2003 K. Hilt...

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1 of 2 BIS 102 Name _____________ Key ________________________ Winter, 2003 Last First K. Hilt First Midterm Score (100): ___________ Equations: pH = pK a + log {[b]/[a]} (K a ) (K b ) = 1 x 10 -14 K a = x 2 /y-x K b = x 2 /y-x Some possibly useful pK a ’s: Compound pK a ’s Phosphate 2.12, 7.21, 12.32 Amino acid side chains asp 3.9 glu 4.2 his 6.0 tyr 10.1 lys 10.5 cys 8.3 arg 12.5 Amino acid α -carboxyl group 2.1 Amino acid α -amino group 9.6 Oligopeptide N-terminal amino group 7.4 Oligopeptide C-terminal carboxyl group 3.6 1. ( 25 pts.) What is the net charge, to the nearest 0.1, of lys-glu-arg-asn-his-cys at pH 5.9? Show all calculations. By inspection: +1 +1 0 C-term. -1 Calculate: N-terminus Glu side chain His side chain pH = pKa + log {[b]/[a]} pH = pKa + log {[b]/[a]} pH = pKa + log {[b]/[a]} 5.9 = 7.4 + log b/a 5.9 = 4.2 + log b/a 5.9 = 6.0 + log b/a 1.5 = log a/b 1.7 = log b/a 0.1 = log a/b a/b = 31.6/1 b/a = 50.1/1 a/b = 1.26 a = 31.6/32.6 = 0.97 b = 50.1/51.1 = -0.98
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This note was uploaded on 10/07/2009 for the course BIS 52192 taught by Professor Enochbaldwin during the Winter '09 term at UC Davis.

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BIS102 Hilt W03 MT1 - 1 of 2 BIS 102 Winter, 2003 K. Hilt...

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