Partial charge polypeptide

Energy Parameters in Polypeptides. IV. Semiempirical Molecular Orbital Calculations of Conformational Dependence of Energy and Partial Charge in Di- and Tripeptides. 

No, K. T., J. A. Grant, M. S. Jhon, and H. A. Scheraga. 1990. Determination of Net Atomic Charges Using a Modified Partial Equalization of Orbital Electronegativity Method 2. Application to Ionic and Aromatic Molecules as Models for Polypeptides. J. Phys. Chem. 94, 4740-4746. 

When the operating pH of fused capillaries is reduced to less than 3.0, silanol ionization drops to almost zero and the EOF is drastically reduced. Both peptides and proteins can be separated under these conditions. Note however, that they are partially denatured at extremes of pH range. This may cause dissociation of multimeric proteins into subunits, or multiple conform-ers may be formed. Below pH 3 or above pH 10, only basic or acidic amino acids are ionized, respectively. The reduction in charge diversity of proteins observed at or near physiological pH will diminish selectivity of electrophoretic separations. Polypeptides undergo ion pairing with the acid used to control the pH under acidic conditions. The relative hydrophilicity or hydrophobicity of this acid will have a strong influence on selectivity. 

Determination of Net Ionic Charges Using a Modified Partial Equalization of Orbital Electronegativity Method. 1. Application to Neutral Molecules as Models for Polypeptides. 

Energy Parameters in Polypeptides. VII. Geometric Parameters, Partial Atomic Charges, Nonbonded Interactions, Hydrogen Bond Interactions, and Intrinsic Torsional Potentials for the Naturally Occurring Amino Acids. 

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