lecture 3

lecture 3 - Lecture 3 Background reading Assignment Segel...

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Unformatted text preview: Lecture 3 1/12/10 Background reading: Assignment: Segel Page 93: Problems 48 and 49 Garrett and Grisham: Chapter 4: Pages 86 - 103 Outline ¡ Amino acids with positively charged R groups ¡ Amino acids with negatively charged R groups ¡ Nonprotein amino acids ¡ Chemical reactivity of amino acids ¡ Peptide bond formation ¡ Peptides ¡ Complementarity ¡ Neuropeptides ¡ Amino acids with positively charged R groups Arg R His H Guanidinium group Imidazole group H + Lys K H H 2 N H 2 N NH pK a1 = 2.2 pK a2 = 9.0 pK a3 = 12.5 pH 1 2 3 If began titration with .1 mmole amino acid in fully protonated form, would require .3 mmole base to titrate it to the totally unprotonated form. +2 +1 +0-1 NaOH ¡ Amino acids with negatively charged R groups Asp D Glu E ¡ Nonprotein amino acids There are about 150 other amino acids that are not found in proteins. H Histamine (derived from histidine) Examples: COOH CH 2 CH 2 CH 2 NH 3 + γ-aminobutyric acid (GABA) potent neurotransmitter COOH CH 2 CH 2 NH 3 + β-alanine a component of pantothenic acid ¡ Chemical reactivity of amino acids All amino acids can undergo the typical carboxyl and amino group reactions In addition, the R groups of the amino acids can undergo specific reactions characteristic of the functional groups they contain....
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lecture 3 - Lecture 3 Background reading Assignment Segel...

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