CHEM237 Lecture Notes - Lecture 5: Solvent, Selenocysteine, Silica Gel
18 May 2017
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Pro: instead of h attached to alpha, there"s another c attached. Positive when protonated, neutral when deprotonated (basic side chains, act like acids) Negative when protonated, neutral when deprotonated (acidic side chains, act like bases) Selenocysteine (sec, u) found in 15 human proteins, deiodinases, and peroxidases. Selenium is more reactive than sulfur and increases activity 1000x. There are selenocysteine specific trna and the deletion of the gene for sec trna is lethal. Peptide titration curves: only groups that titrate are the n terminal, c terminal, and side chains, there is one plateau for each ionisable group and the plateau"s ph = pka, polar solvent: when cooh deprotonate, they become negative. Calculating pi pi: isoelectric point where the net charge = 0. If there are 2 pka values, take the average of the two for the non charged aa side chains.
