F. Martino

Hartree-Fock calculation for disordered polymers

Abstract A method is presented for treating the eigenspectrum of a finite size disordered polymer within a nearly SCF LCAO HF theory. Variants of the negative factor counting and inverse iteration techniques are presented for obtaining the eigenspectrum and eigenvectors. Model polymers and polyacetylene are specifically considered.

A theoretical study on the structure and stability of the nucleohistone complex. I. The interaction between the polypeptide backbone and single‐ and double‐stranded B‐DNA helices

The interaction energies between periodic single‐ and double‐stranded DNA models, using the structural parameters of B‐DNA, and polyglycine in various conformations are calculated with the help of the mutually consistent field method together with perturbation theoretical expressions. For the repeating units of DNA the four nucleotide bases adenine, guanine, thymine, and cytosine, the nucleotides adenylic acid and thymidine are chosen. The polypeptide component is represented by polyglycine assuming the fully extended β‐pleated sheet and the α‐helical conformations. In addition, several polyglycine helices are investigated, whose helix axes coincide with the one of DNA and whose turn lengths are a fraction, equal or a multiple of the length of a complete winding of B‐DNA. For all DNA–polyglycine complexes, the structure is optimized with respect to the total energy of the combined system. It turns out that the complex, in which the agreement between the helical symmetry of B‐DNA and polyglycine is realize...

Effects of disorder on the eigenstates of rings of hydrogen atoms

Abstract Reported are self-consistent field calculations on disordered rings of hydrogen atoms and studies of the spatial nature of the resulting localized eigenstates as a function of degree of disorder. This model represents the simplest hamiltonian having realistic electron-nucleus and electron-electron interactions, displaying both cellular and structural disorder.

Model calculation on DNA-protein interaction

As a model for DNA-protein interaction we have performed an STO-3G calculation on the hydrogen bonded methylguanidium + dihydrogen-orthophosphate − composite system and its constituent ions. The analysis of the change in the charge distribution due to the interaction shows that the calculated −2.55 eV interaction energy is nearly purely electrostatic.

Calculational Methods for Disordered Quasi-One-Dimensional Systems

The transport of entities such as electrons, excitons, and phonons in disordered media is affected greatly by the nature of the randomness. If the degree of randomness is sufficiently large, the electronic wave function is localized in a small region in a sense described by Anderson1 and transport of electrons takes place by hopping among these localized states. Even if we limit our consideration to quasi-one-dimensional systems the calculation of the density of states and the wave functions in long disordered chains is a formidable task. In what follows we shall describe a number of different approaches to the problem and present the results of recent calculations on various model systems. In all cases we are aiming at approximate methods for systems sufficiently complex that massive self consistent field calculations are at present completely out of the question.