Chapter 4 - Chapter 4 1 Chemical Characteristics of...

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Chapter 4 1. Chemical Characteristics of R-groups that distinguish 20 AA. a. The hydrophobic AA—essentially nonpolar side chains that interact very weakly or not at all w/ water i. Alanine (Ala), Valine (Val), leucine (Leu), isoleucine (ile), Phenyalanine (Phe), Methionine (Met), tryptophan(trp), Proline (Pro) b. Polar AA—can interact with water b/c the contain h-bonding groups (vary in size) i. Serine (Ser), Threonine(Thr), Tyrosine (Tyr) –hydroxyl groups ii. Cysteine (Cys) –thiol iii. Asparagine (Asn) and Glutamine (Gln) –amide groups iv. Histidine (ring) v. Glycine(Cly)--- polar by default—neither charged nor hydrophobic vi. Depending on presence of nearby groups that increase polarity, some side chains can ionize at physiological pH (e.g., His) vii. Disulfide bonds—cysteines thiol group oxidizes with another c. Charged AA i. Four AA have side chains that are virtually always charged 1. Aspartate (Asp) and Glutamate (Glu) (-) charge and bear carboxylate group 2. Lysine (Lys) and Arginine (Arg) are positively charged
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This note was uploaded on 03/20/2008 for the course CH 369 taught by Professor Kbrowning during the Spring '07 term at University of Texas.

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Chapter 4 - Chapter 4 1 Chemical Characteristics of...

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