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31.
Abstract An action spectrum was obtained for photoreactivation (PR) of morphological abnormality arising from ultraviolet (UV)-irradiation of sea urchin sperm. The wavelength dependence of PR was measured by the restoration of the formation of normal pluteus larvae after the exposure of fertilized eggs to various fluences of monochromatic PR light (313 to 500 nm). The PR action spectrum showed a maximum around 365 nm and a secondary peak somewhere above 400 nm. High PR activity beyond 400 nm wavelengths may reflect an advantageous or adaptational ability to cope with harmful effects of solar UV radiation. 相似文献
32.
3,4-Dhydro-6,7-dimethoxy-4-methyl-3-oxo-quinoxaline-2-carbonyl azide is a highly senstive fluorescence derivatization reagent for primary, secondary and tertiary alcohols for high-performance liquid chromatography. Reaction conditions are optimized with benzyl alcohol, n-hexanol, cyclohexanol and 2-methyl-2-butanol. The reagent reacts with the alcohols in benzene to produce the corresponding fluorescent carbamic acid esters, which can be separated on a reversed-phase column YMC Pack C8 with aqueous methanol as eluent. the detection limits for the alchols are 2–5 fmol per 10-μl njection. The reagent also reacts with hydroxysteroids with primary, secondary and/or tertiary alcoholic group(s) to form fluorescent derivatives. Hydroxycarboxylic acids and phenols do not give any chromatographic peaks. 相似文献
33.
Yuzuru Katagiri Kenzo Kanohta Kazuhiko Nagasawa Tadao Okusa Toshio Sakai Osamu Tsumura Yasuhiko Yotsui 《Analytica chimica acta》1981,133(4):535-543
A practical search system for proton n.m.r. spectra is reported. The coding rules and search algorithms are described in detail. Data for 8000 spectra have been converted into a computer-readable file from printed charts. Several search tests are used to evaluate the usefulness of the search system, and various effects of experimental conditions such as different instruments, frequencies and solvents on recall efficiency are described. The results presented indicate that the system should be applicable to routine analytical work. 相似文献
34.
A simple and sensitive method is described for the determination of biogenic indole compounds adsorbed on cellulose or alumina plates for thin-layer chromatography by room-temperature phosphorimetry. The optimum conditions were investigated for 5-hydroxyindole-3-acetic acid and indole-3-acetic acid. The compounds are spotted on the plates, which are then sprayed successively with sodium citrate or sodium acetate, and sodiu iodide solutions. The plates are dried completely under a stream of dry nitrogen, and immediately dipped in molten paraffin. The phosphorescence is stable for at least 3 h even in moist air. The limits of detection for nine biogenic indole compounds tested are between 2 and 300 pmol per sample spot. 相似文献
35.
Ptilomycalin A and crambescidins, novel marine guanidine alkaloids, have a unique pentacyclic guanidine structure, and exhibit a considerable array of biological activities. The first method developed for the synthesis of the pentacyclic guanidine core structure involved successive 1,3-dipolar cycloaddition reactions and resulted in the first total synthesis of crambescidin 359. The synthesis of other pentacyclic guanidine derivatives has been based on this methodology and applied as tools for studying biological activities, and as chemical reaction catalysts. 相似文献
36.
Hwang IW Park M Ahn TK Yoon ZS Ko DM Kim D Ito F Ishibashi Y Khan SR Nagasawa Y Miyasaka H Ikeda C Takahashi R Ogawa K Satake A Kobuke Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(12):3753-3761
The excitation-energy-hopping (EEH) times within two-dimensional cyclic zinc(II)-porphyrin arrays 5 and 6, which were prepared by intermolecular coordination and ring-closing metathesis reaction of olefins, were deduced by modeling the EEH process based on the anisotropy depolarization as well as the exciton-exciton annihilation dynamics. Assuming the number of energy-hopping sites N = 5 and 6, the two different experimental observables, that is, anisotropy depolarization and exciton-excition annihilation times, consistently give the EEH times of 8.0 +/- 0.5 and 5.3 +/- 0.6 ps through the 1,3-phenylene linkages of 5 and 6, respectively. Accordingly, the self-assembled cyclic porphyrin arrays have proven to be well-defined two-dimensional models for natural light-harvesting complexes. 相似文献
37.
Absorption and photoluminescence (PL) spectra, PL quantum efficiency, and PL lifetime have been investigated on bis(8-hydroxyquinoline)
zinc (Znq2) and magnesium (Mgq2) in solutions and powder. Znq2 and Mgq2 have the lowest-energy absorption band at 376 and 396 nm in acetonitrile solution, respectively, and emission band with peak
at 555 and 480 nm. The PL quantum efficiency is 0.03 and 0.45 for Znq2 and Mgq2 in the solution, respectively, while 0.45 and 0.36 in powder. Unlike the case of powders, two PL lifetimes are obtained in
solutions. The longer lifetime is attributed to molecule having interaction with its neighboring molecule, while the shorter
one to the isolated single molecule. 相似文献
38.
Ikuya Tagawa Yosuke UrakamiMaki Maeda Youji MaruyamaKazue Kudo Hiromi ShiinaMasafumi Mochizuki 《Journal of magnetism and magnetic materials》2012,324(3):327-329
To make the write-field much stronger with sharper cross-track field gradient in Shingled perpendicular Magnetic Recording (SMR), we have successfully developed asymmetric SMR heads with one-side shield design. Using these heads, higher track density capability on the shielded-side was demonstrated, which came from narrower erase-band width at shielded side. 相似文献
39.
40.
Tohru TakeiTakumi Ohki Yosuke HaradaNaoto Kumagai Hiroki FukumotoTake-aki Koizumi Akihiro MaedaTakahiro Kojima Yoshihisa SeiKohei Shiramizu Masahiro AbeMasashi Oota Takakazu Yamamoto 《Tetrahedron letters》2012,53(44):5907-5910
Dibromopyridines or dibromopyridone with -(CH2)m-SO3Na group(s) has been prepared via the reactions of the corresponding dibromopyridines with -OH and -NH2 groups with sultone. These compounds were converted into polymers with the -(CH2)m-SO3H groups via organometallic polycondensation. The polymer showed proton conducting properties and high stability toward oxidation. 相似文献