Comparative characteristics of a tryptophan molecule in the gas phase and water

The L and D isomers of the tryptophan (Trp) molecule and the (Trp)⁺ cation in the gas phase and water are calculated at the DFT level to reveal the effect of water considered in the dielectric continuum approximation on the electronic characteristics of the molecule. The distribution of effective atomic charges and bond lengths enables the prediction of the most probable parts of the chemical bond cleavage during the fragmentation of the molecule under the ionizing particle flux. These data are supplemented with a calculation of fragmentation energies. Zwitterionic structures characterized by the appearance of considerable dipole moments and a change in their orientation with respect to the ground state are distinguished among the possible isomeric forms in water.     

Migration of protons in a chain of tyrosine residues

This article deals with the proton migration in a tyrosine stack, which models the proton channels existing in a number of proteins, including tubulin. The magnesium ion Mg²⁺ within the complex with guanosine triphosphate facilitates dissociation of a water molecule through initiating a shift of protons along the chain composed of relatively distant tyrosine residues. The process is thermodynamically stable (ΔG₂₉₈<0). The energy barrier for the protein shift does not exceed 3.15 kJ/mole. A relatively weak electrostatic field mimicking electret properties of proteins facilitates long‐distance proton migration. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 409–415, 2001     

X-OH 2 + (X = C, O) cations: Vibrational spectra, stability, and electron capture reactions

Calculations of the potential energy surfaces of X-OH ₂ ⁺ cations (X = C, O) by the restricted and unrestricted Hartree-Fock methods (RHF, UHF) taking into account the correlation energy (MP-2) and by the CASSCF method are presented. All cations are found to be rather stable against X-O bond rupture and intermolecular rearrangement. The reaction of electron capture by these cations is studied.     

Aspect-ratio dependent oscillatory thermocapillary convection in the floating half zone

The dependency of the critical Marangoni number on the geometrical aspect ratio of the floating half zone is essential to predict the onset of oscillatory thermocapillary convection.The experimental studies in the microgravity conditions on floating half zones of several centimeters in diameter have predicted that the critical Marangoni number increases with the increasing aspect ratio,and the terrestrial experimental studies have predicted the contradictory conclusion for floating half zones of several mil...