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Amino Acids - Found at turns or bends which are on surface...

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Less Polar / Indifferent more polar Amide > Acid > Alcohol > Amine > Ether > Alkane less polar Less Hydrophobic / Indifferent Hydrophobic / Non-Polar Hydrophilic / Polar e physiological pH of 7.34, thus it will predominantly exist in its neutral form. However at pH values below 6 the imidazole ring will be protonated (green). So His is considered less polar b/c it is only sometimes (+) char pKa = 8.2 ionizes to thiolate anion H + of Cys’s thiol is more acidic than the hydroxylic H + of Ser, making the nucleophilic thiol(ate) much more reactive than the hydroxyl of Ser. reason: 1) S has a low propensity to H bond 2) thiol group can react with other thiol groups in an oxidation rxn that yields a disulfide bond/bridge . Cys pKa = 6.04 H + His Indole Gly Ala Val Pro imino group can ionize when it takes on a proton biosynthetically derived from Glu can only act as H bond acceptor (not donor) b/c of lack of H on amide
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Unformatted text preview: Found at turns or bends, which are on surface of proteins. Aliphatic Ser Ile EX: very polar nonpolar Gln Asp Glu Ser Lys Ala Aromatic big greasy phenyl ring behind it is quite hydrophobic (nonpolar) and dominates its interactions. Thus it is essentially a hydrophobic nonpolar aa, but one that dabbles with polar H bonds. Trp Phe Tyr Thr pKa = 10.46 Hydroxyl pKa = 12.48 pKa = 10.5 Leu Metet Asn Gln Glu Asp Lys Arg are restricted in the conformation the chain can adopt. ***more difficult for these aa’s to adopt α-helical conformation, but it is easier and preferred for them to lie within beta sheets he S atom is largely non-reactive, thus Met effectively substitutes well with true aliphatic aa’s. pKa = 3.9 Acidic AA’s pKa = 4.07 side chain nearest to protein main chain (hydrocarbon tail) Charged Amides Basic AA’s...
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