Physicochemical Nature of Peptides

The characteristics of peptides are situated between those of amino acids and high molecular weight proteins. Oligopeptides containing up to 15 amino acids behave similarly to amino acids. Short peptide chains cannot create a complicated conformation. In contrast, very long polypeptides with chain lengths up to approximately 100 units behave like small proteins. They exhibit characteristic features of secondary and tertiary structure.

Peptides exist in aqueous solution as amphoteric ions. Therefore peptides possess isoelectric points (pI). The peptide has net electroneutral properties at the pI. The zwitterionic characteristics are influenced predominantly by the acidity of the medium. In acidic media the carboxyl group (pKa & 2.7-2.9) is proto-nated and the peptide behaves as a cation. In alkaline media the protonated ammonium group is eliminated and the zwitterionic form is converted into an anion. The degree of dissociation is determined by the dissociation constants of the functional groups yielding different net charges.

A further feature to be considered in elec-trophoretic behaviour is the sequence of the amino acids. The dissociation constants of the individual residues are affected by the arrangement of the amino acids in the chain. Mass-to-charge ratios are altered and the peptide exhibits a different mobility.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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