Search Results - (Author, Cooperation:H. B. Gray)

2011-07-19

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

*Photosynthesis ; *Solar Energy ; Synthetic Biology

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] The Educational Factors of Imperialism. AMONG all civilis"d races and in all epochs of the world's history there has existed an inveterate belief that the particular age in which men live is fundamentally distinct from those that have preceded it. Even in the most stagnant periods the illusion has ...

Electronic Resource

1432-1327

Key words Solution structure ; Paramagnetic biomolecules ; NMR ; Cytochrome c

Springer Online Journal Archives 1860-2000

Biology

Chemistry and Pharmacology

Abstract  The availability of NOE constraints and of the relative solution structure of a paramagnetic protein permits the use of pseudocontact shifts as further structural constraints. We have developed a strategy based on: (1) determination of the χ tensor anisotropy parameters from the starting structure; (2) recalculation of a new structure by using NOE and pseudocontact shift constraints simultaneously; (3) redetermination of the χ tensor anisotropy parameters from the new structure, and so on until self-consistency. The system investigated is the cyanide derivative of a variant of the oxidized Saccharomyces cerevisiae iso-1-cytochrome c containing the Met80Ala mutation. The structure has been substantially refined. It is shown that the analysis of the deviation of the experimental pseudocontact shifts from those calculated using the starting structure may be unsound, as may the simple structure refinement based on the pseudocontact shift constraints only.

Electronic Resource

1432-1327

Springer Online Journal Archives 1860-2000

Biology

Chemistry and Pharmacology

Abstract  Analysis of electron-transfer (ET) kinetics data obtained from experiments on Ru-modified proteins (cytochrome c, azurin, myoglobin) reveals that distant donor-acceptor electronic couplings depend upon the secondary structure of the intervening polypeptide matrix. Rates of Fe2+→Ru3+ ET reactions in cytochrome c decay exponentially with tunneling-pathway length (decay constant 0.73 Å–1); these rates also decay exponentially with Ru-Fe distance (decay constant 1.1 Å–1). In azurin, a β-sheet protein, Cu+→Ru3+ rates exhibit an exponential Cu-Ru distance dependence with a decay constant of 1.1 Å–1. Comparison of distant couplings in azurin and myoglobin suggests that hydrogen bonds are better mediators across β sheets than through α helices.

Electronic Resource

1432-1327

Key words Electron transfer ; Tunneling pathways ; Azurin ; Cytochrome c ; Myoglobin

Springer Online Journal Archives 1860-2000

Biology

Chemistry and Pharmacology

Abstract  Analysis of electron-transfer (ET) kinetics data obtained from experiments on Ru-modified proteins (azurin, cytochrome c, myoglobin) and the bacterial photosynthetic reaction center reveals that distant donor-acceptor electronic couplings depend upon the secondary structure of the intervening polypeptide matrix. The β-sheet azurin structure efficiently and isotropically mediates coupling with an exponential distance-decay constant of 1.1 Å–1. The experimentally derived distance-decay constant of 1.4 Å–1 for long-range ET in myoglobin and the reaction center suggests that hydrogen-bond couplings are weaker through α helices than across β sheets. The donor-acceptor interactions of systems with comparable tunneling energies fall into two coupling zones: the β zone (bounded by distance-decay constants of 0.9 and 1.15 Å–1) includes all the β-sheet (azurin) couplings and all but one coupling in cytochrome c; the α zone (boundaries: 1.25 and 1.6 Å–1) includes less strongly coupled donor-acceptor pairs in myoglobin and the reaction center as well as a relatively weakly coupled pair in cytochrome c.

Electronic Resource

1432-2234

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Zusammenfassung Nach zwei verschiedenen Näherungen werden im Rahmen der Methode der Molekülbahnen dieπ-Elektronenzustände einiger Moleküle, die Nitrilgruppen enthalten, untersucht. Es werden der zweizähnige Ligand 2,3-Bis-methylmercapto-maleinsäuredinitril und verwandte Moleküle betrachtet. Die Elektronenspektren dieser Verbindungen lassen sich mit Hilfe der berechneten Termenergien deuten.

Résumé Pour quelques systèmes aux électronsπ itet possédant des groupes CN, y compris le ligande chélatant NC-C(SCH3)-C(SCH3)-CN et de molécules semblables, nous donnons et comparons les résultats de deux variantes de la méthode des orbitales moléculaires. Les spectres électroniques de ces molécules sont donnés et interprétés à l'aide des énergies calculées.

Abstract Results of two different types of molecular orbital calculations of severalπ-orbital systems containing nitrile groups are reported and compared. The bidentate ligandbis-(methylmercapto) maleonitrile and related molecules are included. Electronic spectra of these molecules are reported and assigned in terms of the calculated energies.

Electronic Resource