Nucleic electronic structure

Equation 4.9 has been extensively applied to study the mechanisms of electrophilic (e.g., protonation) reactions, drug-nucleic acid interactions, receptor-site selectivities of pain blockers as well as various other kinds of biological activities of molecules in relation to their structure. Indeed, the ESP has been hailed as the most significant discovery in quantum biochemistry in the last three decades. The ESP also occurs in density-based theories of electronic structure and dynamics of atoms, molecules, and solids. Note, however, that Equation 4.9 appears to imply that p(r) of the system remains unchanged due to the approach of a unit positive charge in this sense, the interaction energy calculated from V(r) is correct only to first order in perturbation theory. However, this is not a serious limitation since using the correct p(r) in Equation 4.9 will improve the results. 

Nucleic Acids and Proteins, Electronic Structure Nucleic Acids and Proteins, Influence of Physical Agents 7 3... 

Proteins, Solid, Adsorption of Water on (Eley Leslie). Proteins and Nucleic Acids, Electronic Structure Proteins and Nucleic Acids, Influence of Physical Agents on Purine-Pyrimidine Pairs, Steroids, and Polycyclic Aromatic Carcinogens (Pullman). ... 

The year 2003 is the tenth anniversary of the first Femtochemistry Conference and the fiftieth anniversary of Watson and Crick s celebrated discovery of the DNA double helix [1], Remarkable progress has been made in both fields femtosecond spectroscopy has made decisive contributions to Chemistry and Biology, and advances in the elucidation of static nucleic acid structures have profoundly transformed the biosciences. However, much less is known about the dynamical properties of these complex macromolecules. This is especially true of the dynamics of the excited electronic states, including their evolution toward the photoproducts that are the end result of DNA photodamage [2],... 

VII. Tautomerism, Electronic Structures, and Spectra of Rare Pyrimidine Bases of the Nucleic Acids. 312... 

The study of the reactivity of the nucleic acid bases utilizes indices based on the knowledge of the molecular electronic structure. There are two possible approaches to the prediction of the chemical properties of a molecule, the isolated and reacting-molecule models (or static and dynamic ones, respectively). Frequently, at least in the older publications, the chemical reactivity indices for heteroaromatic compounds were calculated in the -electron approximation, but in principle there is no difficulty to define similar quantities in the all-valence or allelectron methods. The subject is a very broad one, and we shall here mention only a new approach to chemical reactivity based on non-empirical calculations, namely the so-called molecular isopotential maps. 

N. V. Zholtovsky and V. I. Danilov, Quantum Mechanical Study of the Electronic Structure of the Nucleic Acids Bases by CNDO/2 Method. Preprint Inst. Phys. Acad. Sci. Ukr. SSR, Kiev, 1973. 

Nobel-laureate Richard Feynman once said that the principles of physics do not preclude the possibility of maneuvering things atom by atom (260). Recent developments in the fields of physics, chemistry, and biology (briefly described in the previous sections) bear those words out. The invention and development of scanning probe microscopy has enabled the isolation and manipulation of individual atoms and molecules. Research in protein and nucleic acid structure have given rise to powerful tools in the establishment of rational synthetic protocols for the production of new medicinal drugs, sensing elements, catalysts, and electronic materials. 

Nagata, C. A., A. Imamura, Y. Tagashira, and M. Kodama Semiempirical self-consistent field molecular orbital calculation of the electronic structure of the base components of nucleic acids. Bull. Chem. Soc. Japan 38, 1638 (1965). 

Some recent developments in the quantum-mechanical studies on the electronic structure of the nucleic acids. J. Chem. Phys. 43, S 233 (1965). 

Nucleic Acid Excited-State Electronic Structure... 

Carbene Complexes Carbonyl Complexes ofthe Transition Metals Cyanide Complexes of the Transition Metals Dinuclear Organometallic Cluster Complexes Electron Transfer in Coordination Compounds Electron Transfer Reactions Theory Electronic Structure of Organometallic Compounds Luminescence Nucleic Acid-Metal Ion Interactions Photochemistry of Transition Metal Complexes Photochemistry of Transition Metal Complexes Theory Polynuclear Organometallic Cluster Complexes. 

In principle, paramagnetic ions also may be used to induce hyperfine shifts in nucleic acids to aid detection of binding sites. Ions with high relative magnetic anisotropy and short unpaired electron relaxation times (i.e., Co Fe and trivalent lanthanide ions except for Gd ) are candidates for such studies. Indeed, Tb and Eu ions have been used as fluorescent probes of nucleic acid structures it is expected that NMR studies also would be informative. " ... 

As discussed earlier in the section on heterocyclic equilibria, heterocycles show large changes in electronic structure between the gas phase and solution, and thus the effects of aqueous solvation on nucleic acid bases is very interesting. 

Experimentally, the direction of a transition moment in a molecule can he evaluated by four methods (i) polarized spectra of single crystals, (ii) fluorescence or phosphorescence polarization, (iii) spectra of molecules embedded in stretched Aims, and (iv) spectra of molecules oriented by external fields. Only relative directions of the transition moment can be determined by means of the last three methods, whereas the polarized spectra of single crystals give the absolute direction of the moments if the crystal structure is known. The first method has been applied to the study of the electronic structure and spectra of several pyrimidine bases of nucleic... 

Pressures used to investigate biochemical systems range from 0.1 MPa to about 1 GPa (0.1 MPa = 1 bar, 1 GPa = 10 kbar). Such pressures only change intermolecular distances and affect conformations, but do not change covalent bond distances or bond angles. In fact, pressures in excess of 30 kbar are required to change the electronic structure of a molecule. The covalent structure of low molecular mass biomolecules (peptides, lipids, saccharides), as well as the primary structure of macromolecules (proteins, nucleic acids and polysaccharides), is not perturbed by pressures up to about 20 kbar. Pressure acts predominantly on the conformation and supramolecular structures of biomolecular systems. 

Transition metal ion incorporation in hybrid inorganic-nucleic acid structures adds another dimension to the field of DNA nanotechnology because metal ions, in particular those with unpaired d electrons, have a broad range of electronic and magnetic properties. In most applications in material science, DNA is used as a scaffold for uniform binding of metal ions either to nucleobases or to ligands attached to nucleobases. For example, Braun et al. 

It was clearly demonstrated in the many beautiful studies conducted on spectroscopically active metal centers in proteins, that the electronic structure of a metal center can provide a sensitive spectroscopic handle to examine the region to which the metal complex is bound. This same spectroscopic sensitivity can be utilized in studies of nucleic acids. 

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