Basic Amino Acids z Hydrophillic nitrogenous bases z Positively charged at physiological pH z Histidine – imidazole ring protonated/ionized, only amino acid that functions as buffer in physiol range. z Lysine - diamino acid, protonated at pH 7.0 z Arginine - guianidinium ion always protonated, most basic amino acid +H : H+ pKa 6.0Basic Amino Acids z Hydrophillic nitrogenous bases z Positively charged at physiological pH z Histidine – imidazole ring protonated/ionized, only amino acid that functions as buffer in physiol range. z Lysine - diamino acid, protonated at pH 7.0 z Arginine - guianidinium ion always protonated, most basic amino acid +H : H+ pKa 6.0