Insights into the activity and specificity of Trypanosoma cruzi trans-sialidase from molecular dynamics simulations.

Trypanosoma cruzitrans-sialidase (TcTS), which catalyzes the transfer or hydrolysis of terminal sialic acid residues, is crucial to the development and proliferation of the T. cruzi parasite and thus has emerged as a potential drug target for the treatment of Chagas disease. We here probe the origin of the observed preference for the transfer reaction over hydrolysis where the substrate for TcTS is the natural sialyl donor (represented in this work by sialyllactose).

An evaluation of the GLYCAM06 and MM3 force fields, and the PM3-D* molecular orbital method for modelling prototype carbohydrate-aromatic interactions.

The structures and interaction energies of 21 binary complexes of fucose and glucose with toluene, 3-methylindole or p-hydroxytoluene, evaluated at the DFT-D level, are used to judge the accuracy of the GLYCAM06 and MM3 force fields, and the PM3-D* molecular orbital method for modelling carbohydrate-arene interactions. The accuracy of the DFT-D method is substantiated by comparison with high level CCSD(T) calculations on a small number of representative complexes. It is found that a correct description of the intermolecular dispersive interactions is essential.

Binding of pollutant aromatics on carbon nanotubes and graphite.

The semiempirical PM3 method with dispersive corrections (PM3-D) is used to predict the interaction energy of a number of aromatic pollutants with a graphene surface and with carbon nanotubes. It is found that the dispersive interactions are dominant in determining the magnitude of the interaction and that electron transfer between the adsorbate and the surface is small. Good agreement is found between the calculated interaction energies and the experimental affinities measured in an aqueous environment.

Carbohydrate-aromatic pi interactions: a test of density functionals and the DFT-D method.

The performance of a number of computational approaches based upon density functional theory (DFT) for the accurate description of carbohydrate-pi interactions is described. A database containing interaction energies of a small number of representative complexes, computed at a high ab initio level, is described, and is used to judge 18 different density functionals including the M05 and M06 families as well as the DFT method augmented with empirical dispersive corrections (DFT-D). The DFT-D method and the M06 functionals are found to perform particularly well, whilst traditional functionals such as B3LYP perform poorly.

Carbohydrate-protein recognition probed by density functional theory and ab initio calculations including dispersive interactions.

Carbohydrate-protein recognition has been studied by electronic structure calculations of complexes of fucose and glucose with toluene, p-hydroxytoluene and 3-methylindole, the latter aromatic molecules being analogues of phenylalanine, tyrosine and tryptophan, respectively. We use mainly a density functional theory model with empirical corrections for the dispersion interactions (DFT-D), this method being validated by comparison with a limited number of high level ab initio calculations. We have calculated both binding energies of the complexes as well as their harmonic vibrational frequencies and proton NMR chemical shifts.