Quantum chemical and molecular dynamics modeling of interaction of isomolecular dipeptides of α-l-alanyl-α-l-alanine and β-alanyl-β-alanine with sodium dodecyl sulfate micelles

Abstract

Quantum chemical investigation of α-l-alanyl-α-l-alanine and β-alanyl-β-alanine complexes with SDS dimer as an anion micelle fragment in polarizable continuum has been carried out by using of DFT method with B97-D/6-311++G(3d,3p) level. The variation of peptide structure and the difference in energies of free peptides, SDS dimer and their complexes have been analyzed. Optimized configurations of complexes are stabilized by hydrogen bonds of (H2)NH…O(S) type. The localization of α-l-alanyl-α-l-alanine among the charged groups of SDS dimer is more preferable. The localization of β-alanyl-β-alanine among the charged groups or in the dimer hydrophpbic canal results in close values of the complex formation energy. More favorite change of energy and shorter length of hydrogen bond of (H2)NH…O(S) type have been revealed for complex formation between SDS dimer and β-alanyl-β-alanine as opposed to α-l-alanyl-α-l-alanine. Molecular dynamics simulation of adsorption of the peptides on SDS micelle has been performed in NPT ensemble at 0.1 MPa and 298 K. The cell under study contained 14,678 water molecules, one peptide zwitter-ion, and the micelle including 64 SDS monomers. Most probable localization of peptide atoms relative the micelle has been analyzed. The peptide – SDS micelle interaction is accompanied by diminish of average number of peptide – water H-bonds and the formation of at the mean two H-bonds with SDS. Some peculiarities of adsorption of the isomolecular peptides on SDS micelle are appeared in different values of H-bond lifetimes, different probability of formation of H-bond of NH3+…−O3SO or NH3+…O(SO3−) types, and localization of peptide zwitter-ions outside or within double electrical layer of the micelle.