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KL Britton HF Rogers Y Asano T Dairi Y Kato TJ Stillman DW Rice 《Acta crystallographica. Section D, Biological crystallography》1998,53(4):124-126
The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres. 相似文献
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J. Hala G. F. W. Searle T. J. Schaafsma A. van Hoek P. Pancoska K. Blaha K. Vacek 《Photochemistry and photobiology》1986,44(4):527-534
Fluorescence-detected magnetic resonance of triplets in zero magnetic field (FDMR), fluorescence fading (FF) due to triplet-formation, both at 4.2 K, and prompt fluorescence decay kinetics (FDK) at room temperature have been measured for free pheophorbide- a (f-Pheo) and bound (b-Pheo) to a synthetic polypeptide (L-L ys -L-A la -L-A la )n , dissolved in dimethylformamide (DMF). Fluorescence decay kinetics measurements of f-Pheo in DMF yielded 1-5 ns lifetimes, for b-Pheo in DMF a ~ 50 ps decay-component was found emitting at 730–750 nm. Zero-field splitting parameters |D| and |E| of the lowest triplet state T1 were determined from FDMR spectra as (337 and 24) 10-4 cm-1 for f-Pheo and (359 and 25) 10-4 cm-1 for b-Pheo, both in DMF. Decay rate constants of the three spin levels of T1 of b-Pheo ( K x = 1200 50 s-1 , k y = 440 25 s-1 , k z = 80 5 s-1 ) and relative steady-state populations (Nx = 28 2%, Ny = 47 2%, Nz = 26 2%) determined from FF curves predict a fluorescence decrease at the D–E and D + E FDMR transitions, whereas experimentally a fluorescence increase is observed. The FDMR sign-inversion results from singlet-singlet energy transfer from b-Pheo monomers to their aggregates, followed by fast intersystem crossing to T1 . These results indicate that aggregates are formed by two or more b-Pheo molecules at different positions on the folded polypeptide chain. This situation resembles that in chlorophyll-proteins, containing low-lying traps, resulting from interaction of chromophores with other chromophores and with the protein environment. 相似文献
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F. G. H. Van Wijk C. B. Beijer P. Gast T. J. Schaafsma 《Photochemistry and photobiology》1987,46(6):1015-1019
The electron spin polarization (ESP) pattern of the donor-triplet state (PR ) of reaction centers (RC's) of the purple bacterium Rhodobacter (formerly Rhodopseudomonas) sphaeroides R-26 was investigated. δm =±1 triplet EPR spectra were recorded of unmodified RC's as well as of RC's from which Fe2+ or ubiquinone was removed, or ubiquinone was substituted by menaquinone.
The relative amplitude of the Y peaks in the triplet EPR powder spectrum of PR decreases when the temperature is increased from 8 K to 100 K in RC's with an intact quinone-iron complex. This decrease is more pronounced when the primary ubiquinone is substituted by menaquinone. These observations provide further support for the hypothesis that the observed lineshape of the PR triplet state EPR spectrum reflects the presence of a third electron spin, magnetically coupled to I- in the P+ I- radical pair, as suggested by Van Wijk et al. (1986) (Photobiochem. Photobiophys . 11, 95–100). Our observations suggest that this phenomenon may be general in purple bacteria. 相似文献
The relative amplitude of the Y peaks in the triplet EPR powder spectrum of P
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V. V. Apanasovich E. G. Novikov N. N. Yatskov R. B. M. Koehorst T. J. Schaafsma A. van Hoek 《Journal of Applied Spectroscopy》1999,66(4):613-616
Results of investigation of the optical properties of zinc complexes of mesotetraphenylporphyrin and monopyridyltriphenylporphyrin
in impurity-free organic solvent are presented. Analyses of absorption and emission spectra and fluoresence decay kinetics
in terms of both a sum of exponentials and using simulation of energy-transformation processes in a tetramer-type Zn-porphyrin
complex compound are carried out.
Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 549–552, July–August, 1999. 相似文献
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Poly(3,4‐ethylenedioxythiophene):GlycosAminoGlycan Aqueous Dispersions: Toward Electrically Conductive Bioactive Materials for Neural Interfaces 下载免费PDF全文
Daniele Mantione Isabel del Agua Wandert Schaafsma Javier Diez‐Garcia Begona Castro Haritz Sardon David Mecerreyes 《Macromolecular bioscience》2016,16(8):1227-1238
There is an actual need of advanced materials for the emerging field of bioelectronics. One commonly used material is the conducting polymer poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) due to its general use in organic electronics. However, depending on the application in bioelectronics, PEDOT:PSS is not fully biocompatible due to the high acidity of the residual sulfonate protons of PSS. In this paper, the synthesis and biocompatibility properties of new poly(3,4‐ethylenedioxythiophene):GlycosAminoGlycan (PEDOT:GAG) aqueous dispersions and its resulting films are shown. Thus, negatively charged GAGs as an alternative to PSS are presented. Three different commercially available GAGs, hyaluronic acid, heparin, and chondroitin sulfate are used. Indeed, PEDOT:GAGs dispersions are prepared through an oxidative chemical polymerization in water. Biocompatibility assays of the PEDOT:GAGs coatings are performed using SH‐SY5Y and CCF‐STTG1 cell lines and with ATP and Ca2+. Results show full biocompatibility and a pronounced anti‐inflammatory effect. This last characteristic becomes crucial if implanted in the body. These materials can be used for in vivo applications, as transistor or electrode for electrical recording and for all the possible situations when there is contact between electronic circuits and living tissues.
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N. N. Yatskov V. V. Apanasovich R. B. M. Koehorst A. van Hoek T. J. Schaafsma 《Journal of Applied Spectroscopy》2003,70(3):372-377
The photophysical properties of thin films of Zn-monopyridyltriphenylporphyrin (Zn(4-Py)TrPP) obtained by the method of centrifugation on a quartz film substrate have been investigated. The results of the analysis of the measured excitation and luminescence spectra and also of the kinetic curves of fluorescence depolarization, as they decay, of the Zn(4-Py)TrPP films permit the conclusion that Zn-meso-monopyridylporphyrins self-organize into aggregates. The symmetric closed tetramer ([Zn(4-Py)TrPP]4) seems to be the most probable aggregate of Zn-meso-monopyridylporphyrins. 相似文献
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The excited-state properties of heterodimers oftetra(4-carboxyphenyl)porphyrin (TPPC) and tetra(N-methylpyridyl) porphyrin (TMPyP) are studied by absorption and emission spectroscopy, EPR and zero-field ODMR. The excited singlet and triplet states of dimers formed by pairing H2TPPC with H2TMPyP or ZnTMPyP are localized on H2TPPC. The dimers formed by pairing H2TPPC with CuTMPyP and H2TMPyP with ZnTPPC or CuTPPC are non-fluorescent due to intramolecular electron transfer. 相似文献