Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. The link between one amino acid residue and the next is an amidebond, and is sometimes referred to as a peptide bond. An amide bond is somewhat shorter than a typical carbon-nitrogen single bond, and has a partial double-bond character, because the participating carbon molecule is doubly bonded to an oxygen molecule and the nitrogen has a lone pair of electrons available for bonding.
Peptides (like proteins) occur in nature and are responsible for a wide array of functions, many of which are not yet understood. Antimicrobial peptides generally disrupt the membranes of a target cell, causing lysis of the cell. How this occurs, and what determines the activity and selectivity of these peptides, is currently only known approximately.
Peptides differ from proteins, which are also long chains of amino acids, by virtue of their size. Traditionally, those peptide chains that are short enough to make synthetically from the constituent amino acids are called peptides rather than proteins. The dividing line is at approximately 50 amino acids in length, since naturally-occurring proteins tend, at their smallest, to be hundreds of residues long. So, in essence, a peptide is a small protein.
Peptidomimetics (such as peptoids and β-peptides) are molecules related to peptides, but with different properties.
Notes on terminology
A polypeptide is a single linear chain of amino acids.
A protein is one or more polypeptides more than about 50 amino acids long.
An oligopeptide or (simply) a peptide is a polypeptide less than 30-50 amino acids long.
Oligopeptides which bind TAR are identified in this assay by their characteristic, retarded migration on the gel, relative to TAR RNA to which no oligopeptide has bound.
Oligopeptides which differ from the basic domain in terms of amino acid sequence, either by way of addition, deletion or replacement of one or more amino acids including replacement of an L-amino by a corresponding D-amino acid, are referred to herein as "analogues" of the tat basic domain.
vi) an oligopeptide comprising from 6 to 11 arginines and one glutamine; and
1 is a graph plotting the association constant of oligopeptides according to embodiments of this invention representative of the binding affinity of the oligopeptide to DNA vs. the length of the linking unit in the oligopeptide.
2 is a graph plotting the association constant of oligopeptides according to embodiments of this invention representative of the binding affinity of the oligopeptide to DNA vs. the length of the linking unit in the oligopeptide.
K.sub.a is an association constant of the DNA binding affinity of the oligopeptides in units of 10.sup.7 L.M.sup.-1.
Feeds |
Contact