A. V. Nemukhin

Predicting lanthanide cluster properties: a comparison with the observed optical spectra of Ho2

Abstract Ab initio pseudopotential calculations for Ho and Ho 2 have been carried out in order to support an assignment of the bands observed in UV-visible spectra of matrix isolated holmium species. SCF, MCSCF and configuration interaction (CI) procedures have been used with quasirelativistic pseudopotentials to compute the ground and excited state energies of Ho and Ho 2 , together with the dipole transition moments. For Ho 2 , using a Q = 11 pseudopotential (describing the holmium atom in the 4f 10 6s 2 5d 1 electronic state), two transitions from the ground state σ g 2 σ u 2 π u 2 to the states with principal excitations σ u → π g and π u → σ g ∗ are predicted at 499 and 524 nm. These two lines, with predicted close intensities, correlate nicely with the observed features at 498 504 and 558 563 nm in the spectrum of matrix-isolated Ho 2 .

Modeling chemical transformations at the active sites of cholinesterases by quantum-based simulations

The significance of the quantum-mechanical–molecular-mechanical (QM/MM) method in modeling chemical transformations at the active sites of cholinesterases is discussed. Diverse versions of the QM/MM approach are applied to understand the molecular mechanisms of the reactivation reaction of butyrylcholinesterase phosphorylated by the catalytic serine residue.

Computer simulation in molecular medicine and drug design

Achievements in genomics and proteomics, as well as the exponential growth of computing power, ensure qualitatively new opportunities in understanding the molecular nature of “living matter” and, as a consequence, the extension of the capabilities of medicine. This paper considers two scientific fields in which high-throughput computing is especially effective. The first is computer-aided design of drugs, and the second is analysis of human molecular polymorphism and individual sensitivity to drugs. General provisions are illustrated with specific examples, including the development of a new class of antimyasthenic drugs—cholinesterase inhibitors, research in the molecular polymorphism of brain aspartoacylase, the clarification of the nature of Canavan disease, and the study of individual sensitivity to drugs—cholinesterase inhibitors.

Modeling hydrolysis of the cyclic dimeric guanosine monophosphate by phosphodiesterases

The structures of intermediates of the reaction of enzymatic hydrolysis of the cyclic dimeric guanosine monophosphate are computed by using the quantum mechanics/molecular mechanics (QM/MM) method. Tentative mechanisms of transformations at the active site of catalytic domains of phosphodiesterases are suggested based on the results of simulations.

Semiempirical andab initio study of the structure of the alumophenylsiloxane complex and its fragments

The structures, spectra, and electron density distributions of the alumophenylsiloxane (APS) complex and its fragments have been calculated using semiempirical (AM1) and ab initio (SCF/3-21G and SCF/6-31G*) quantum chemical approximations. It has been shown that the local properties of the central fragment of alumophenylsiloxane, which is a slightly distorted tetrahedron AlO4, are described with the (LiO)2AlOBe(OH) cluster.