A Comparison Between Experimental and Broken Symmetry Density Functional Theory (BS-DFT) Calculated Electron Paramagnetic Resonance (EPR) Parameters of the S2 State of the Oxygen Evolving Complex of Photosystem II in Its Native (Calcium) and Strontium Sub

Title A Comparison Between Experimental and Broken Symmetry Density Functional Theory (BS-DFT) Calculated Electron Paramagnetic Resonance (EPR) Parameters of the S2 State of the Oxygen Evolving Complex of Photosystem II in Its Native (Calcium) and Strontium Sub
Authors N.J. Beal; T.A. Corry; P.J. O'Malley
Journal J Phys Chem B
DOI 10.1021/acs.jpcb.7b09498
Abstract

A comparison between experimental and Broken Symmetry Density Functional Theory (BS-DFT) calculated hyperfine couplings for the S2 state of the oxygen evolving complex (OEC) has been performed. The effect of Ca substitution by Sr combined with the protonation state of two terminal hydroxo or water ligands, W1 and W2, on the calculated hyperfine couplings of 55Mn, 13C, 14N, 17O and 1H nuclei has been investigated. Our findings show best agreement for OEC models which contain a hydroxo group at the W2 position and a water molecule at W1. For this model the agreement between calculated and experimental data for all hyperfine couplings is excellent. Models with a hydroxo group at W1 are particularly poor models. Sr substitution has a minor influence on calculated hyperfine couplings in agreement with experimental determinations. The sensitivity of the hyperfine couplings to relatively minor changes in the OEC structure demonstrates the power of this methodology in refining the details of its steric and electronic structure which is an essential step in formulating a complete mechanism for water oxidation by the OEC.

Citation N.J. Beal; T.A. Corry; P.J. O'Malley.A Comparison Between Experimental and Broken Symmetry Density Functional Theory (BS-DFT) Calculated Electron Paramagnetic Resonance (EPR) Parameters of the S2 State of the Oxygen Evolving Complex of Photosystem II in Its Native (Calcium) and Strontium Sub. J Phys Chem B. 2017. doi:10.1021/acs.jpcb.7b09498

Related Elements

Strontium

See more Strontium products. Strontium (atomic symbol: Sr, atomic number: 38) is a Block S, Group 2, Period 5 element with an atomic weight of 87.62 . Strontium Bohr ModelThe number of electrons in each of Strontium's shells is [2, 8, 18, 8, 2] and its electron configuration is [Kr] 5s2. The strontium atom has a radius of 215 pm and a Van der Waals radius of 249 pm. Strontium was discovered by William Cruickshank in 1787 and first isolated by Humphry Davy in 1808. In its elemental form, strontium is a soft, silvery white metallic solid that quickly turns yellow when exposed to air. Elemental StrontiumCathode ray tubes in televisions are made of strontium, which are becoming increasingly displaced by other display technologies pyrotechnics and fireworks employ strontium salts to achieve a bright red color. Radioactive isotopes of strontium have been used in radioisotope thermoelectric generators (RTGs) and for certain cancer treatments. In nature, most strontium is found in celestite (as strontium sulfate) and strontianite (as strontium carbonate). Strontium was named after the Scottish town where it was discovered.

Calcium

See more Calcium products. Calcium (atomic symbol: Ca, atomic number: 20) is a Block S, Group 2, Period 4 element with an atomic weight of 40.078. The number of electrons in each of Calcium's shells is [2, 8, 8, 2] and its electron configuration is [Ar]4s2. Calcium Bohr ModelThe calcium atom has a radius of 197 pm and a Van der Waals radius of 231 pm. Calcium was discovered and first isolated by Sir Humphrey Davy in 1808. It is the fifth most abundant element in the earth's crust and can be found in minerals such as dolomite, gypsum, plagioclases, amphiboles, pyroxenes and garnets. In its elemental form, calcium has a dull gray-silver appearance. Calcium is a reactive, soft metal that is a member of the alkaline earth elements. Elemental CalciumIt frequently serves as an alloying agent for other metals like aluminum and beryllium, and industrial materials like cement and mortar are composed of calcium compounds like calcium carbonate. It is also an biologically essential substance found in teeth, bones, and shells. The name "calcium" originates from the Latin word "calics," meaning lime.

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