Stereoselective formation of cis ozonides by electron-transfer photooxygenation of naphthyl-substituted epoxides. Stereochemical assignments of ozonides by x-ray crystallography and chromatographic resolution

1984 ◽  
Vol 106 (20) ◽  
pp. 6087-6088 ◽  
Author(s):  
A. Paul Schaap ◽  
Shahabuddin Siddiqui ◽  
Girija Prasad ◽  
A. F. Magsudur Rahman ◽  
John P. Oliver
Keyword(s):  
Electron Transfer ◽  
X Ray ◽  
X Ray Crystallography ◽  
Chromatographic Resolution

Intercalation of Trioxatriangulenium Ion in DNA:  Binding, Electron Transfer, X-ray Crystallography, and Electronic Structure

2003 ◽  
Vol 125 (8) ◽  
pp. 2072-2083 ◽  
Author(s):  
Jóhannes Reynisson ◽  
Gary B. Schuster ◽  
Sheldon B. Howerton ◽  
Loren Dean Williams ◽  
Robert N. Barnett ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electronic Structure ◽  
Dna Binding ◽  
X Ray ◽  
X Ray Crystallography

A structural basis of light energy and electron transfer in biology1

1989 ◽  
Vol 9 (6) ◽  
pp. 635-673 ◽  
Author(s):  
Robert Huber
Keyword(s):  
Electron Transfer ◽  
Functional Data ◽  
Three Dimensional ◽  
Light Energy ◽  
Structural Basis ◽  
Reaction Centre ◽  
X Ray ◽  
X Ray Crystallography ◽  
Energy And Electron Transfer ◽  
And Function

Aspects of intramolecular light energy and electron transfer will be discussed for three protein cofactor complexes, whose three-dimensional structures have been elucidated by x-ray crystallography: Components of light harvesting cyanobacterial phycobilisomes, the purple bacterial reaction centre, and the blue multi-copper oxidases. A wealth of functional data is available for these systems which allow specific correlations between structure and function and general conclusions about light energy and electron transfer in biological materials to be made.

The photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 11: Involving (R)-(+)-α-terpineol and (R)-(+)-limonene, substituting on 1,4-dicyanobenzene

1996 ◽  
Vol 74 (4) ◽  
pp. 602-612 ◽  
Author(s):  
Donald R. Arnold ◽  
Dennis A. Connor ◽  
Kimberly A. McManus ◽  
Pradip K. Bakshi ◽  
T. Stanley Cameron
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Nmr Spectra ◽  
Radical Cations ◽  
Acetonitrile Solution ◽  
Aromatic Substitution ◽  
X Ray ◽  
X Ray Crystallography ◽  
Intramolecular Reactions ◽  
C Nmr

Irradiation of an acetonitrile–methanol (3:1) solution of 1,4-dicyanobenzene (1), biphenyl (5), and (R)-(+)-limonene (21) leads to formation of the 1:1:1 (methanol:21:1) photo-NOCAS adducts: 4-[(1R,2S,4R)-4-isopropenyl-2-methoxy-1-methylcyclohexyl]benzonitrile (23, 30%), 4-[(1S,2R,4R)-4-isopropenyl-2-methoxy-1-methylcyclohexyl]benzonitrile (24, 2%), 4-[(1R,2R,5R)-5-isopropenyl-2-methoxy-2-methylcyclohexyl]benzonitrile (25, 3%), and 4-[(1S,2S,5R)-5-isopropenyl-2-methoxy-2-methylcyclohexyl]benzonitrile (26, 1%). When an acetonitrile solution (no added methanol) of 1,4-dicyanobenzene (1), biphenyl (5), and (R)-(+)-α-terpineol (22) was irradiated under these conditions, the products were the cyclized 1:1 (22:1) photo-NOCAS adducts: (1R,2S,5R)-2-(4-cyanophenyl)-2,6,6-trimethyl-7-oxabicyclo[3.2.1]octane (27,21%) and (1S,4R,6R)-6-(4-cyanophenyl)-1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane (28, 2%). Structural assignments were based primarily upon detailed analysis of 1H and 13C nmr spectra and, for four of the products (24, 26, 27, and 28), structures were firmly established by X-ray crystallography. The mechanism for the formation of these products is discussed, with emphasis on the intramolecular reactions of the intermediate alkene radical cations. Molecular mechanics (MM3) calculations gave information regarding the structure and energy of the conformers of 21 and 22 that was useful for predicting/explaining the observed reactivity on the basis of approach vector analysis; the transition state for cyclization incorporates the nucleophile and the alkene radical cation carbon atoms at the vertices of an obtuse triangle orthogonal to the plane of the π-system. Key words: photoinduced electron transfer, radical cations, cyclization, terpenes.

Ion-Mediated Electron Transfer in a Supramolecular Donor-Acceptor Ensemble

Science ◽  
2010 ◽  
Vol 329 (5997) ◽  
pp. 1324-1327 ◽  
Author(s):  
Jung Su Park ◽  
Elizabeth Karnas ◽  
Kei Ohkubo ◽  
Ping Chen ◽  
Karl M. Kadish ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Ion Binding ◽  
Acceptor Pair ◽  
Initial Oxidation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Back Electron Transfer ◽  
Donor And Acceptor ◽  
Mediated Electron Transfer ◽  
Donor Acceptor

Ion binding often mediates electron transfer in biological systems as a cofactor strategy, either as a promoter or as an inhibitor. However, it has rarely, if ever, been exploited for that purpose in synthetic host-guest assemblies. We report here that strong binding of specific anions (chloride, bromide, and methylsulfate but not tetrafluoroborate or hexafluorophosphate) to a tetrathiafulvalene calix[4]pyrrole (TTF-C4P) donor enforces a host conformation that favors electron transfer to a bisimidazolium quinone (BIQ2+) guest acceptor. In contrast, the addition of a tetraethylammonium cation, which binds more effectively than the BIQ2+ guest in the TTF-C4P cavity, leads to back electron transfer, restoring the initial oxidation states of the donor and acceptor pair. The products of these processes were characterized via spectroscopy and x-ray crystallography.

Difference Fourier Analysis of Glucose Embedded and Frozen Hydrated Purple Membrane

1982 ◽  
Vol 40 ◽  
pp. 74-75
Author(s):  
Jules S. Jaffe ◽  
Robert M. Glaeser
Keyword(s):  
Purple Membrane ◽  
Data Set ◽  
High Resolution Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Fourier Techniques ◽  
Versus Protein ◽  
The Difference ◽  
Difference Fourier ◽  
Ideal Method

Although difference Fourier techniques are standard in X-ray crystallography it has only been very recently that electron crystallographers have been able to take advantage of this method. We have combined a high resolution data set for frozen glucose embedded Purple Membrane (PM) with a data set collected from PM prepared in the frozen hydrated state in order to visualize any differences in structure due to the different methods of preparation. The increased contrast between protein-ice versus protein-glucose may prove to be an advantage of the frozen hydrated technique for visualizing those parts of bacteriorhodopsin that are embedded in glucose. In addition, surface groups of the protein may be disordered in glucose and ordered in the frozen state. The sensitivity of the difference Fourier technique to small changes in structure provides an ideal method for testing this hypothesis.

3-D reconstruction of molecular shape from microcrystal thin sections

1983 ◽  
Vol 41 ◽  
pp. 748-749
Author(s):  
S. Cusack ◽  
J.-C. Jésior
Keyword(s):  
Three Dimensional ◽  
Molecular Shape ◽  
Biological Molecules ◽  
Fourier Space ◽  
Single Particles ◽  
Thin Sections ◽  
Standard Methods ◽  
X Ray ◽  
X Ray Crystallography ◽  
Dimensional Reconstruction

Three-dimensional reconstruction techniques using electron microscopy have been principally developed for application to 2-D arrays (i.e. monolayers) of biological molecules and symmetrical single particles (e.g. helical viruses). However many biological molecules that crystallise form multilayered microcrystals which are unsuitable for study by either the standard methods of 3-D reconstruction or, because of their size, by X-ray crystallography. The grid sectioning technique enables a number of different projections of such microcrystals to be obtained in well defined directions (e.g. parallel to crystal axes) and poses the problem of how best these projections can be used to reconstruct the packing and shape of the molecules forming the microcrystal.Given sufficient projections there may be enough information to do a crystallographic reconstruction in Fourier space. We however have considered the situation where only a limited number of projections are available, as for example in the case of catalase platelets where three orthogonal and two diagonal projections have been obtained (Fig. 1).

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