Applicability of the critical-chromatography concept to proteomics problems: Separation of peptides modeled by a heterogeneous rod

The problems of separation of short peptides are considered in terms of the model of rigid rod adsorption. Analytical expressions relating the retention volume to the sequence of amino-acid residues in the gradient elution are obtained. The model of adsorption of a peptide as a rigid rod is compared with the model of its adsorption as a random-walk chain. The transition of rodlike peptides to the adsorbed state is more abrupt compared with the random-walk chain having the same sequence, while with an increase in the peptide length the random-walk chain model becomes more accurate. It is shown that the model of adsorption of a peptide as a rigid rod for short peptides fits the experimental data and correctly predicts the character of separation of peptides having equal lengths and identical amino-acid compositions but slightly differing in the alternation of residues in a chain.