5′,8-Cyclopurine-2′-deoxynucleosides: Molecular structure and charge distribution – DFT study in gaseous and aqueous phase

Oxidatively generated damage to DNA frequently appears in the human genome as an effect of aerobic metabolism or as the result of exposure to exogenous oxidizing agents. Due to these facts, it has been decided to present the structural propriety and charge distribution of 5′,8-cyclo-2′-deoxyadenosine/guanosine (cdA, cdG) in their 5′R and 5′S diastereomeric forms. For all points of quantum mechanics studies presented, the density functional theory (DFT) with B3LYP parameters on 6-311++G** basis set level was used. The 2-deoxyribose moiety of cyclopurines has adopted the ₀T¹ conformation in their cationic, neutral and anionic forms. The natural population analysis (NPA) of charge distribution between purine/2-deoxyribose moieties exhibited positive/positive value for cations, positive/negative for neutral molecules. NPA data for anionic forms showed negative/negative values in gas (exclude (5′S)cdG) and positive/negative in water. The dipole moments of 5′,8-cyclopurine-2′-deoxynucleosides were found as follows: 7.83(5′R)cdG, 6.86(5′S)cdG, 3.99(5′R)cdA, 1.99(5′S)cdA in the gaseous phase, 11.29(5′R)cdG, 9.99(5′S)cdG, 6.44(5′R)cdA, 4.14(5′S)cdA in the aqueous phase.     

Geminals in Dirac–Coulomb Hamiltonian eigenvalue problem

The applicability of the Dirac–Coulomb model in computational analysis of the properties of many-electron systems has been, since many years, a subject of dispute and controversy. The most common and numerically safe approach, based on the restriction of the variational space to the many-electron spinors spanning a subspace of the positive-energy part of the complete Hilbert space has been challenged by alternative models in which carefully selected both positive and negative energy functions are taken into account. However, these constructions are not possible when one goes beyond the one-electron model, e.g. when geminal-containing trial functions are used. Then the problem becomes particularly difficult and subtle. In this report several aspects specific for the geminal-based variational approach to the Dirac–Coulomb eigenvalue problem are discussed.     

Fuzzy approach in psychophysical modeling of human operator-manual lifting system

A fuzzy representation of the human operator decision-making process of selecting the maximum acceptable weight of manual lift is developed. Measures of acceptability are expressed in terms of membership functions which describe the degree to which the combined effect of biomechanical and physiological stresses is acceptable to the human operator. It is assumed that the combination of these two stresses has a synergistic effect on the individual's performance, and that the perception of this effect is reflected in an operator's choice when selecting the preferable weight of lift. The combined acceptabilities of a lifting task are compared to the subjective capacity norms established by the subjects in a psychophysical experiment. The conditions under which the distance between acceptability measures of the combined and the psychophysical stresses can be minimized are established. It is concluded that at a certain level of similarity between the acceptability measures of these stresses, a decision is made, and the preferred weight of lift selected.     

Momentum transfer in 30–200 MeV 4H induced reaction with 59Co

Thick-target recoil ranges of radioactive nuclei produced in 30–200 MeV alpha-particle bombardment of ⁵⁹Co have been used to deduce the longitudinal momentum transfer per projectile nucleon (p₆/A) as a function of residue mass and bombarding energy. The average value of p₆/A increases monotonically with bombarding energy and reaches a maximum value of ≈ 160 MeV/c at ≈ 23 MeV/u, and decreases thereafter. The maximum value of p₆/A is equal to the incident momentum up to ≈ 23 MeV/u and saturates at a value of ≈ 220 MeV/c beyond this energy.     

A Note on Nonlinear Parameters in Variational Methods

The dependence of the eigenvalues of matrices representing a quantum-chemical Hamiltonian in a model space on the nonlinear parameters of the trial functions is analyzed. Several theorems useful in determining the dependence of the matrix eigenvalues on the parameters are presented and their implications on the choice of the orbital basis sets are briefly discussed. A simple method of optimization of the parameter values is formulated.     

Trace representation of weights on partial O-algebras

The purpose of this paper is to investigate when a weight ? on a partial O^∗-algebra is a trace weighted by a positive self-adjoint operator Ω, that is, whenever s.t. X†∈L(X) and ?(X†□X)<∞. It is shown that if contains the inverse N of a positive compact operator such that the weak multiplication N□N is defined, then every weight ? on satisfying ?(N□N)<∞ is a trace weighted by some positive trace operator.     

An effective quasirelativistic hamiltonian

Several ways of introducing effective relativistic potentials into the Schrödinger equation are discussed. A detailed study of a potential, which leads to the radial electron density exhibiting the same asymptotic behaviour as the Dirac density is performed. This potential, which is a j-dependent correction to the radial Schrödinger equation and which retains exactly the analytical form of the equation, may be easily implemented in atomic and molecular calculations.     

Symmetric group approach to relativistic CI. I. General formalism

General formulas for matrix elements of spin-dependent operators in a basis of spin-adapted antisymmetrized products of orthonormal orbitals are derived. The resulting formalism may be applied to construction of the Hamiltonian matrices both for Pauli and for projected no-pair relativistic configuration interaction methods. From a formal point of view, it is a generalization of the symmetric group approach to the CI method for the case of spin-dependent Hamiltonians. © 1997 John Wiley & Sons, Inc.