Electron spin echo study of long-lived radicals which cause mutation in gamma-ray irradiated mammalian cells

Long-lived radicals, produced by gamma-ray irradiation of mammalian cells at room temperature, cause mutation and morphological transformation in the cells. The local environment near the long-lived radicals in irradiated cells was investigated here by the analysis of electron spin echo envelope modulation (ESEEM) spectra. The number of hydrogen (deuterium) atoms surrounding the long-lived radical, which may correspond to the number of water molecules, was estimated roughly as one or two. It is postulated that the long-lived radicals are generated in the interior of biopolymers. The radicals are not produced by the reaction of OH radicals, but mainly by the decomposition of biopolymer which absorbed directly the energy of the ionizing radiation.     

Determination of prostatic androgens in 10 mg of tissue using liquid chromatography–tandem mass spectrometry with charged derivatization

A practical liquid chromatography–tandem mass spectrometric (LC-MS-MS) method for the determination of prostatic 5-dihydrotestosterone (DHT) and testosterone (T) has been developed. The prostatic androgens were extracted with MeOH–H₂O (3: 7, v/v), purified with an Oasis HLB cartridge, derivatized with the permanently charged reagent 2-hydrazino-1-methylpyridine (HMP), and subjected to LC–MS-MS analysis using electrospray ionization (ESI) operated in the positive ion mode. The derivatization with HMP was very effective at increasing the detectability using the positive-ESI-MS. The method allowed the reproducible and accurate quantification of ng g^–1 tissue levels of prostatic androgens in 10 mg of tissue. That is, the intra- and inter-assay coefficients of variation were below 8.1 and 9.3%, respectively, and the analytical recoveries of the androgens were quantitative. The limits of quantitation for DHT and T were both 1.0 ng g^–1 tissue. The developed method was used to determine DHT and T in the prostates of patients with benign prostatic hyperplasia and prostate cancer, and satisfactory results were obtained.     

X-Ray Diffraction Studies of Bacteriorhodopsin. Determination of the Positions of Mercury Label at Several Engineered Cysteine Residues

Abstract— The single cysteine-containing bacteriorhodopsin mutants F27C, L100C, T170C, F171C and I222C were labeled with p -chloromercuribenzoic acid, which specifically reacts with sulfhydryl groups. These cysteines should be located at the cytoplasmic ends of the transmembrane helices A, C, F or G. We determined the positions of the bound mercury atoms by X-ray diffraction of purple membrane films, with better than 1 Å accuracy. The determined mercury positions were compared with the structural model from cryoelectron microscopy (N. Grigorieff, T. A. Ceska, K. H. Downing, J. M. Baldwin and R. Henderson, J. Mol. Biol 259, 393-421, 1996). Given that the distance between the mercury and the Cα atom of the cysteine in the xy plane must be shorter than 4.5 Å and that the mercury atom is located at the δ position, the positions obtained for the mercury labels agree with their expected positions from the structural model. The present results give a rationale for detecting structural changes upon illumination as shifts occur in the mercury label position.     

Oxidative cycloamination of olefins with aziridines as a versatile route to saturated nitrogen-containing heterocycles

Highly reactive [5,3] and [6,3] bicyclic aziridines can be readily prepared from the corresponding NH aziridines and N-bromosuccinimide by intramolecular oxidative cycloamination of olefins. These compounds, including surprisingly stable exo-methylene bicyclic aziridines, provide versatile synthetic entries into a wide range of pyrrolidine- and piperidine-containing heterocycles.     

Chromatographic determinations of a beta-lactam antibiotic, cefaclor by means of fluorescence, chemiluminescence and mass spectrometry

We report analytical informations on the quantification of cefaclor (CCL), a beta-lactam antibiotic by three detection methods. The methods were based on the chemical derivatization of the drug with 4-(2'-cyanoisoindolyl)phenylisothiocyanate (CIPIC) under the reaction conditions with heating at 80 degrees C for 7 min in the presence of pyridine. The CIPIC reagent could react with the primary amino group of the drug to form CIPIC-conjugated CCL. The derivative emitted not only fluorescence (FL) at maximum emission wavelength of 410 nm with the irradiation at 310 nm excitation, but also chemiluminescence (CL) in the presence of H(2)O(2), borate buffer (pH 9.5) and acetonitrile. After reversed-phase liquid chromatographic separation of the CIPIC-conjugated CCL in blood, the derivative could be monitored with a FL detector, indicating the detection limit (S/N=3) of 10 pmol/injection. The CIPIC-conjugated CCL was further monitored most sensitively by a CL detector after simply mixing H(2)O(2) and borate buffer with the column eluate. The CL detection limit was 1.0 pmol/injection. In addition, we attempted to detect the CIPIC-conjugated CCL by liquid chromatographic-mass spectrometry (LC/MS). The MS method permitted the specific detection of the CIPIC derivative of the drug, though the sensitivity was 10(4)-times lower than that of the CL detection.     

Mechanistic pathways for the photoisomerization reaction of the anchored,tethered chromophore of the photoactive yellow protein and its mutants

We show by way of physical organic reasoning that the currently known photochemical results of the chromophore of photoactive yellow protein (PYP) are consistent with that expected of a least volume-demanding process for an anchored, tethered chromophore. The primary photoreaction, interestingly, does not appear to involve a hula-twist process. However, the latter might be involved during subsequent transition of dark intermediates. Absorption data of intermediates obtained from a microsecond time-resolved spectroscopic study of three PYP mutants (E46Q, T50V and R52Q) are consistent with the above analyses.     

Synthesis of the axially substituted titanium Pc-C60 dyad with a convenient method

[structure: see text] We successfully synthesized the axially substituted titanium Pc-C(60) dyad with a convenient method that improves on the traditional asymmetrical phthalocyanine routine to covalently linked phthalocyanines with other functional molecules. The intramolecular photoinduced process between phthalocyanine donor and fullerene acceptor was preliminarily studied.