Proton-coupled electron-transfer processes in photosystem II probed by highly resolved g-anisotropy of redox-active tyrosine YZ

The oxidation of a redox-active tyrosine residue Y(Z) in photosystem II (PSII) is coupled with proton transfer to a hydrogen-bonded D1-His190 residue. Because of the apparent proximity of Y(Z) to the water-oxidizing complex and its redox activity, it is believed that Y(Z) plays a significant role in water oxidation in PSII. We investigated the g-anisotropy of the tyrosine radical Y(Z)(?) to provide insight into the mechanism of Y(Z)(?) proton-coupled electron transfer in Mn-depleted PSII. The anisotropy was highly resolved by electron paramagnetic resonance spectroscopy at the W-band (94.9 GHz) using PSII single crystals. The g(X)-component along the phenolic C-O bond of Y(Z)(?) was calculated by density functional theory (DFT). It was concluded from the highly resolved g-anisotropy that Y(Z) loses a phenol proton to D1-His190 upon tyrosine oxidation, and D1-His190 redonates the same proton back to Y(Z)(?) upon reduction.     

Enantiocontrolled total syntheses of breviones A, B, and C

Enantiocontrolled total syntheses of the breviones A, B, and C have been accomplished using a highly diastereoselective oxidative coupling of an α-pyrone with a tricyclic diene prepared from an optically pure Wieland-Miescher ketone derivative through the 7-endo-trig mode of acyl radical cyclization.     

Synthesis of core‐crosslinked carbosilane block copolymer micelles and their thermal transformation to silicon‐based ceramics nanoparticles

Carbosilane fine particles were synthesized by core‐crosslinking of carbosilane block copolymer micelles and they were pyrolytically transformed into silica nanoparticles. The carbosilane block copolymer, poly(1‐(3‐butenyl)‐1‐methylsilacyclobutane)‐block‐polystyrene, (polyBMSB‐b‐polySt), [(m, n) = (31, 16), (54, 30), and (75, 28)], was synthesized by anionic polymerization of BMSB and St, where m and n represent polymerization degrees of BMSB and St segments, respectively. The block copolymer formed micelles in N,N‐dimethylformamide (DMF). The hydrodynamic diameters (D_h) of the micelles evaluated by dynamic light scattering ranged from 40 to 158 nm depending on the copolymer molecular weight. The core of the micelle was cross‐linked by Pt‐catalyzed hydrosilation with 1,2‐bis(dimethylsilylethane). The D_h of the core‐cross‐linked micelles in THF ranged from 56 to 164 nm. These precursor particles were pyrolyzed at 850 °C under N₂ to give ceramic nanoparticles. The diameters of the spherical ceramic particles estimated by AFM ranged from 25 to 60 nm. X‐ray fluorescence analysis of the ceramic products revealed that it consisted of mainly SiO₂ rather than SiC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3778–3787, 2005     

2-D electron spin transient nutation spectroscopy of Lanthanoid ion Eu2+(8S7/2) in a CaF2 single crystal on the basis of FT-pulsed electron spin resonance spectroscopy: Transition moment spectroscopy

This work demonstrates the usefulness of pulsed electron spin resonance (ESR)-based two-dimensional electron spin transient nutation (2-D ESN) spectroscopy for complete assignments of complicated fine-structure hyperfine ESR spectra including hyperfine forbidden transitions from electronic and nuclear high-spin systems. The 2-D ESN spectroscopy is termed transition moment spectroscopy as spectra are acquired as a function of transition moment instead of transition energy used in conventional spectroscopy. We have applied the novel spectroscopic technique to Eu²⁺ ion (S=7/2,I=5/2), which has two isotopes (¹⁵¹Eu [47.9%] and¹⁵³Eu [52.1%]), in a CaF₂ single crystal as a model system. We have completely identified the complicated fine-structure hyperfine ESR spectra by invoking the spectral simulation of the 2-D ESN spectra on the basis of transition moment analyses. The analyses are based on exact numerical calculations of the transition moments as well as a perturbation-based analytical approach combined with reduced rotation matrices for the nuclear part of the transition moment. This is the first example of the spectral simulation for 2-D ESN spectra including the hyperfine allowed and forbidden transitions in high-spin systems. In addition, we have made simulation of the fine-structure forbidden transitions, which reproduces the angular variations of the observed spectra at liquid helium temperatures.     

The structure of the CT complex between 5,7,12,14-tetramethoxydibenzo[b,i]thianthrene with TCNQ

The structure of 1,4-dithiines obtained from orthodihalogeno heterocycles with thiocarbonyl compounds was determined by X-ray structure analysis of the intermolecular charge-transfer complex between 5,7,12,14-tetramethoxydibenzo[b,i]thianthrene and TCNQ. The formation of the thiazole ring has already been reported but the products were confirmed to be 1,4-dithiines by X-ray structure analysis and the previously reported results.     

Studies on vocal fold injection and changes in pitch associated with alcohol intake

The current study was carried out with particular emphasis on the association between phonetic function tests and alterations in the appearance of the hypopharyngeal and laryngeal mucosa, such as capillary dilatation, edema, and vocal fold injection after alcohol intake. The results demonstrated the occurrence of previously unrecognized pathophysiological changes associated with synchronous phonetic functions in the vocal pathway after alcohol intake. Serum ethanol and aldehyde concentration levels were evaluated hourly for 2.5 h after ingestion of alcohol. When an electronystagmogram showed the typical pattern of alcohol intake, the study was initiated. Occasionally, rhinography was performed on subjects complaining of a stuffy nose after alcohol intake.