scholarly journals An e.x.a.f.s. study of the manganese O2-evolving complex in purified Photosystem II membrane fractions. The S1 and S2 states

1992 ◽  
Vol 285 (2) ◽  
pp. 569-576 ◽  
Author(s):  
D J MacLachlan ◽  
B J Hallahan ◽  
S V Ruffle ◽  
J H A Nugent ◽  
M C W Evans ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Light Harvesting ◽  
Manganese Complex ◽  
X Ray ◽  
Bond Lengths ◽  
Detergent Treatment ◽  
S2 State ◽  
Triton X ◽  
Oxygen Bond

Manganese K-edge X-ray spectra have been obtained for Photosystem II samples isolated using Triton X-100 detergent and samples further purified by n-heptyl beta-D-thioglucoside detergent treatment to remove light-harvesting polypeptides and low-affinity calcium. The structure of the manganese complex is very similar for the two detergent preparations used. Analysis of the e.x.a.f.s. spectra for samples in the S1 and S2 states indicate changes in bond lengths for the shells of oxygen/nitrogen atoms. For the S1 state, oxygen shells at 0.181 and 0.193 nm (1.81 and 1.93 A) were observed and one manganese shell at 0.270 nm (2.70A). In the S2 state the oxygen bond lengths are longer at 0.184 and 0.200 nm (1.84 and 2.00 A). Additionally a shell of scatterers at 0.37 nm (3.7 A) was observed in both states which could be fitted to models with calcium scatterers at this distance.

Pentamethylcyclopentadienyl-Vanadium Complexes Containing Halogeno- and Oxo-Ligands

1987 ◽  
Vol 42 (12) ◽  
pp. 1520-1526 ◽  
Author(s):  
Max Herberhold ◽  
Walter Kremnitz ◽  
Markus Kuhnlein ◽  
Manfred L. Ziegler ◽  
Karl Brunn
Keyword(s):  
Crystal Structure ◽  
Mass Spectra ◽  
High Yield ◽  
Vanadium Complexes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bond Lengths ◽  
Oxygen Bond ◽  
Single Bonds ◽  
Oxo Ligands

AbstractA simple and high-yield preparation of the pentamethylcyclopentadienyl vanadium(IV) trihalides Cp*VX3 (X = CL, Br, I) from Cp*V(CO)4 as well as their conversion into the oxo-vanadium(V) compounds Cp*VOX2 (X = CL, Br) and [Cp*VOX]2(μ-O) (X = CL, Br, I) are described. The equilibrium between the two fluoride species Cp*VOF2 and [Cp*VOF]2(μ-O) has also been investigated. The complexes are characterized by their NMR (51V, l3C, 1H), IR, and mass spectra. The crystal structure of the binuclear chloro-oxo complex [Cp*VOCl]2(μ-O) has been determined by X-ray diffraction. The molecules contain two [Cp*VOCl] units combined via a bent oxo bridge (V-O-V angle of 142.2(2)°). The vanadium-oxygen bond lengths are 157.6(8) and 179.4(1) pm for the terminal and the bridging oxo ligands, respectively, corresponding to double and single bonds.

Orientation of the Oxygen-Evolving Manganese Complex in a Photosystem II Membrane Preparation: An X-ray Absorption Spectroscopy Study

Biochemistry ◽  
1994 ◽  
Vol 33 (32) ◽  
pp. 9712-9721 ◽  
Author(s):  
Ishita Mukerji ◽  
Joy C. Andrews ◽  
Victoria J. DeRose ◽  
Matthew J. Latimer ◽  
Vittal K. Yachandra ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Absorption Spectroscopy ◽  
Manganese Complex ◽  
Membrane Preparation ◽  
Spectroscopy Study ◽  
X Ray ◽  
Oxygen Evolving ◽  
X Ray Absorption

scholarly journals Neutron Diffraction Study of Tetragonal Zirconias containing Tetravalent Dopants

1998 ◽  
Vol 51 (3) ◽  
pp. 539 ◽  
Author(s):  
B. A. Hunter ◽  
C. J. Howard ◽  
D.-J. Kim
Keyword(s):  
Tetragonal Zirconia ◽  
Neutron Diffraction Study ◽  
Neutron Powder Diffraction ◽  
X Ray ◽  
Bond Lengths ◽  
Oxygen Ions ◽  
Vegard’S Law ◽  
Raman Study ◽  
Position Parameter ◽  
Oxygen Bond

In tetragonal zirconia, the cation is coordinated by two interpenetrating tetrahedra of oxygen ions, implying two different cation-oxygen bond lengths. Neutron powder diffraction was used to study tetragonal ZrO2–2 mol% Y2O3 incorporating various amounts of the different tetravalent ions Ge, Ti, Sn and Ce. Precise and accurate values for the lattice parameters and the variable oxygen position parameter have been obtained, and from these the bond lengths derived. The results are compared with those from an earlier X-ray and Raman study on the same materials. Of interest are the confirmation of the increase in cell volume occurring when Zr is replaced by the smaller Sn ion, and the observation of departures from Vegard’s law in the case of substitution of Zr by Ti.

Structure of the manganese complex of photosystem II upon removal of the 33-kilodalton extrinsic protein: an x-ray absorption spectroscopy study

Biochemistry ◽  
1987 ◽  
Vol 26 (19) ◽  
pp. 5967-5973 ◽  
Author(s):  
James L. Cole ◽  
Vittal K. Yachandra ◽  
Ann E. McDermott ◽  
R. D. Guiles ◽  
R. D. Britt ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Absorption Spectroscopy ◽  
Manganese Complex ◽  
Spectroscopy Study ◽  
X Ray ◽  
X Ray Absorption

scholarly journals Exafs Spectroscopic Studies of Uranium (VI) Oxide Precipitates

1996 ◽  
Vol 432 ◽  
Author(s):  
P.G. Allen ◽  
D.K. Shuh ◽  
J.J. Bucher ◽  
N.M. Edelstein ◽  
C.E.A. Palmer ◽  
...  
Keyword(s):  
Room Temperature ◽  
Nearest Neighbor ◽  
Spectroscopic Studies ◽  
X Ray ◽  
Bond Lengths ◽  
Curve Fitting Analysis ◽  
Low Ionic Strength ◽  
X Ray Absorption ◽  
Oxygen Bond ◽  
Precipitate Structure

AbstractWe have investigated the structures of U(VI) oxides precipitated from room temperature aqueous solutions at low ionic strength as a function of pH. Using the uranium LIII - edge extended x-ray absorption fine structure (EXAFS) as a probe of the local structure around the uranium, a trend is observed whereby the axial oxygen bond lengths from the uranyl groups increase from 1.80 Å at pH=7 to 1.86 Å at pH=11. A concomitant decrease in the equatorial oxygen and nearest-neighbor uranium bond lengths also occurs with increasing pH. Expansion of the linear O=U=O group is seen directly at the L111 absorption edge where multiple scattering resonances systematically shift in energy. EXAFS curve-fitting analysis on these precipitates and a sample of synthetic schoepite indicate that the structure of the species formed at pH=7 is similar to the structure of schoepite. At pH=11, the precipitate structure is similar to that of a uranate.

scholarly journals On the structure of the manganese complex of photosystem II: extended-range EXAFS data and specific atomic-resolution models for four S-states

2007 ◽  
Vol 363 (1494) ◽  
pp. 1237-1244 ◽  
Author(s):  
Holger Dau ◽  
Alexander Grundmeier ◽  
Paola Loja ◽  
Michael Haumann
Keyword(s):  
Photosystem Ii ◽  
Manganese Complex ◽  
Atomic Resolution ◽  
Range Data ◽  
Exafs Data ◽  
X Ray ◽  
Extended Range ◽  
The Individual ◽  
X Ray Absorption ◽  
S States

The water-oxidizing manganese complex bound to the proteins of photosystem II (PSII) was studied by X-ray absorption spectroscopy on PSII membrane particles. An extended range for collection of extended X-ray absorption fine-structure (EXAFS) data was used (up to 16.6 Å −1 ). The EXAFS suggests the presence of two Mn–Mn distances close to 2.7 Å (per Mn 4 Ca complex); the existence of a third Mn–Mn distance below 2.9 Å is at least uncertain. Interestingly, a distance of 3.7 Å is clearly resolved in the extended-range data and tentatively assigned to a Mn–Mn distance. Taking into account the above EXAFS results (inter alia), we present a model for the structure of the PSII manganese complex, which differs from previous atomic-resolution models. Emphasizing the hypothetical character, we propose for all semi-stable S-states: (i) a structure of the Mn 4 Ca(μ-O) n core, (ii) a model of the amino acid environment, and (iii) assignments of distinct Mn oxidation states to all the individual Mn ions. This specific working model may permit discussion, verification and invalidation of its various features in comparison with experimental and theoretical findings.

Sign in / Sign up

Export Citation Format

Share Document