Separation of Peptides on Chemically Bonded Reversed Phases

The maintenance of tertiary and quartemary structure of polypeptides and proteins, as well as their mechanisms of association with other cellular components, is known to be, in part, mediated by hydrophobic interactions. In fact, the most important single factor in the organization of the constituent molecules of living matter into complex structural entities and the subsequent transmission of the encoded information from one structure to another is probably the hydrophobic effect. Consequently, it is not surprising that separative methods should have been developed which exploit this phenomenon. 

Because agarose and derived amphiphilic supports show low efficiencies, they have attracted little interest for the high-resolution separation of 

Following the initial observations reported (27, 2Zci) in 1976 on the separation of a series of unprotected peptides, related to the hypothalamic- 

Several fundamental models have recently been proposed (//, I7a,b, 28) in order to quantitatively accommodate the influence of solution equilibria on the distribution process. Although application of these theoretical approaches has yet to provide a comprehensive general description of retention behavior for peptides, they have provided useful insight into those mobile-phase effects arising from changes in the nature and mole fraction of the organic solvent modifier. 

The basic model for the separation of peptidic solutes on nonpolar stationary phases assumes that reversible interactions of the solute molecules S, S2,. . . , S occur with the hydrocarbonaceous ligand L and that the interactions are due to hydrophobic associations and not to electrostatic or hydrogen bonding effects. Conceptually, the sorption of peptides to alkyl-bonded reversed phases under these conditions can be based either on partition or on adsorption processes. In a partition pro- 

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