title: A model for predicting slopes S in the basic equation for the linear-solvent-strength theory of peptide separation by reversed-phase high-performance liquid chromatography.
abstract: A model for predicting the slope (S) in the fundamental equation of linear-solvent-strength theory for peptidic compounds was developed. Our approach is based on the novel assumption that three well-defined molecular descriptors: peptide length (N), charge (Z) and hydrophobicity index (HI) are the major contributors to the value of S. Following the definition of the model's variables, the retention of a number of Arg-terminated synthetic peptides was investigated under isocratic elution conditions (100 A pore size C18 phase, 0.1% trifluoroacetic acid as ion-pairing modifier). The peptide sequences were systematically designed to span the properties of the typical tryptic peptides that are analyzed in proteomic experiments. Experimental data show that slopes S increase with the independent increase in both peptide charge and peptide length when the two other parameters are held constant. The influence of peptide hydrophobicity is more complex: depending on peptide length and charge, stronger RP-HPLC retention can either decrease or increase the values of S. We postulate a general function to explain this behavior: S=C1 x Z(C2)+C3 x N(C4)+C5 x HI(C6)+C7/Z+C8/N+C9/HI+C10 x ZN+C11 x ZHI+C12 x NHI+B. A simple optimization using a "random walk" through parameter-space was used to determine the optimal coefficients compared to the measured S-values of 37 peptides. The model gives a approximately 0.97 R(2) correlation between the measured and predicted S-values: it was verified against previously published data on a human growth hormone protein tryptic digest and some synthetic analogues from that mixture.
authors.affiliation: Department of Physics and Astronomy, University of Manitoba, Winnipeg, R3T 2N2, Canada.
authors.forename: Hoangkim
authors.initials: H
authors.lastname: Vu
authors.forename: Vic
authors.initials: V
authors.lastname: Spicer
authors.forename: Alexander
authors.initials: A
authors.lastname: Gotfrid
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Krokhin
mesh_terms: D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D056148:Chromatography, Reverse-Phase / Q000379:methods*; D013006:Growth Hormone / Q000032:analysis; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008954:Models, Biological; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification*; D012997:Solvents
chemical_list: D010455:Peptides; D012997:Solvents; D013006:Growth Hormone