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41.
Yusuke Yoshimura Ryuichiro Hibi Akiho Nakata Moeka Togashi Shoujiro Ogawa Takayuki Ishige Mamoru Satoh Fumio Nomura Tatsuya Higashi 《Biomedical chromatography : BMC》2019,33(7)
A liquid chromatography/electrospray ionization–tandem mass spectrometry‐based method was developed for the identification of the conjugation positions of the monoglucuronides of 25‐hydroxyvitamin D3 [25(OH)D3] and 24,25‐dihydroxyvitamin D3 [24,25(OH)2D3] in human urine. The method employed derivatization with 4‐(4‐dimethylaminophenyl)‐1,2,4‐triazoline‐3,5‐dione to convert the glucuronides into fragmentable derivatives, which provided useful product ions for identifying the conjugation positions during the MS/MS. The derivatization also enhanced the assay sensitivity and specificity for urine sample analysis. The positional isomeric monoglucuronides, 25(OH)D3‐3‐ and ‐25‐glucuronides, or 24,25(OH)2D3‐3‐, ‐24‐ and ‐25‐glucuronides, were completely separated from each other under the optimized LC conditions. Using this method, the conjugation positions were successfully determined to be the C3 and C24 positions for the glucuronidated 25(OH)D3 and 24,25(OH)2D3, respectively. The 3‐glucuronide was not present for 24,25(OH)2D3, unlike 25(OH)D3, thus we found that selective glucuronidation occurs at the C24‐hydroxy group for 24,25(OH)2D3. 相似文献
42.
Abstract— The photoreaction cycle of 13- cis -bacteriorhodopsin (13- cis -bR) was investigated by low temperature spectrophotometry using two different preparations; 13- cis -bR constituted from bacterioopsin and 13- cis -retinal, and dark-adapted bacteriorhodopsin (bRD ), which is an equi-molar mixture of 13- cis -bR and trans -bR.
By irradiation with 500 nm light at — 190°C, 13- cis -bR was converted to its batho-product, batho-13- cis -bR (batho-bR13 ), which is different from batho-product from trans -bR, batho-bRt . On warming batho-bR13 to -5°C in the dark, it completely changed to trans -bR. We estimated the composition of 13- cis -bR and trans -bR in the warmed sample spectrophotometrically and then the absorption spectrum of batho-bR13 was calculated. The absorption maximum lies at 608 nm, 1250 cm−1 longer than that of 13- cis -bR; the molar extinction coefficient (ε) is about 74000 M −1 cm−1 , larger than that of 13- cis -bR (52000 M −1 cm−1 ).
On the warming the sample containing batho-bR13 formed by irradiating 13- cis -bR or bRD at — 190°C, we could not detect other intermediates such as the lumi- or meta-intermediates seen in trans-bR system. 相似文献
By irradiation with 500 nm light at — 190°C, 13- cis -bR was converted to its batho-product, batho-13- cis -bR (batho-bR
On the warming the sample containing batho-bR
43.
The equilibrium geometry of disilyne is not linear, but is twisted. The potential surfaces of acetylene and disilyne have a critical internuclear distance between the central atoms, where the stable geometry changes from linear to twisted forms the R-dependence of the valence-shell electron energy causes the difference in the structure of the molecules. 相似文献
44.
Sogawa K Watanabe M Sato K Segawa S Ishii C Miyabe A Murata S Saito T Nomura F 《Analytical and bioanalytical chemistry》2011,400(7):1905-1911
In a clinical diagnosis microbiology laboratory, the current method of identifying bacterial isolates is based mainly on phenotypic
characteristics, for example growth pattern on different media, colony morphology, Gram stain, and various biochemical reactions.
These techniques collectively enable great accuracy in identifying most bacterial isolates, but are costly and time-consuming.
In our clinical microbiology laboratory, we prospectively assessed the ability of matrix-assisted laser desorption ionization–time
of flight mass spectrometry (MALDI–TOF MS) to identify bacterial strains that were routinely isolated from clinical samples.
Bacterial colonies obtained from a total of 468 strains of 92 bacterial species isolated at the Department of Clinical Laboratory
at Chiba University were directly placed on target MALDI plates followed by addition of CHCA matrix solution. The plates were
then subjected to MALDI–TOF MS measurement and the microorganisms were identified by pattern matching with the libraries in
the BioTyper 2.0 software. Identification success at the species and genus levels was 91.7% (429/468) and 97.0% (454/468),
respectively. MALDI–TOF MS is a rapid, simple, and high-throughput proteomic technique for identification of a variety of
bacterial species. Because colony-to-colony differences and effects of culture duration on the results are minimal, it can
be implemented in a conventional laboratory setting. Although for some pathogens, preanalytical processes should be refined,
and the current database should be improved to obtain more accurate results, the MALDI–TOF MS based method performs, in general,
as well as conventional methods and is a promising technology in clinical laboratories. 相似文献
45.
46.
Two steroidal compounds BR-1 (I) and ?2 (II) which had been obtained from the rhizomes of Baker, were isolated also from those of Roth. They were identified, respectively, by X-ray analysis and chemical correlation as 1β,2β,3β,4β,5β,7α-hydroxy-spirost-25(27)-en-6-one and its corresponding 6β-hydroxy compound. 相似文献
47.
Akiya Karen Noriaki Ikeda Noboru Mataga Fumio Tanaka† 《Photochemistry and photobiology》1983,37(5):495-502
Formation of singlet charge transfer (heteroexcimer) states in the course of the fluorescence quenching of lumiflavin and riboflavin tetrabutyrate by indole and N-methylindole have been directly observed by means of time-resolved absorption spectral measurements using a picosecond laser photolysis method. Similar transient spectra have been observed also in the case of a flavoenzyme, D-amino acid oxidase. 相似文献
48.
Daniel J. Sindhikara Norio Yoshida Fumio Hirata 《Journal of computational chemistry》2012,33(18):1536-1543
We have created a simple algorithm for automatically predicting the explicit solvent atom distribution of biomolecules. The explicit distribution is coerced from the three‐dimensional (3D) continuous distribution resulting from a 3D reference interaction site model (3D‐RISM) calculation. This procedure predicts optimal location of solvent molecules and ions given a rigid biomolecular structure and the solvent composition. We show examples of predicting water molecules near the KNI‐272 bound form of HIV‐1 protease and predicting both sodium ions and water molecules near the rotor ring of F‐adenosine triphosphate (ATP) synthase. Our results give excellent agreement with experimental structure with an average prediction error of 0.39–0.65 Å. Further, unlike experimental methods, this method does not suffer from the partial occupancy limit. Our method can be performed directly on 3D‐RISM output within minutes. It is extremely useful for examining multiple specific solvent–solute interactions, as a convenient method for generating initial solvent structures for molecular dynamics calculations, and may assist in refinement of experimental structures. © 2012 Wiley Periodicals, Inc. 相似文献
49.
Eiji Takahashi Fumio Sanda Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2002,40(8):1037-1046
Novel pyridinium salts [N‐(α‐phenylbenzyl)‐, N‐(1‐naphthylmethyl)‐, or N‐cinnamyl p‐ or o‐cyanopyridinium hexafluoroantimonates] were synthesized by the reaction of p‐ or o‐cyanopyridine and the corresponding bromides followed by anion exchange with KSbF6. These pyridinium salts polymerized epoxy monomers at lower temperatures than previously reported for N‐benzyl‐2‐cyanopyridinium hexafluoroantimonate. The o‐substituted pyridinium salts showed higher activity than the p‐substituted ones, and the crosslinked epoxy polymers cured with these initiators showed higher glass‐transition temperatures. These pyridinium salts photoinitiated radical polymerization as well as cationic polymerization. The photopolymerization was accelerated by the addition of aromatic ketones as photosensitizers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1037–1046, 2002 相似文献
50.
Chizuko Kabuto Yutaka Higuchi Tomohiro Niimi Fumio Hamada Nobuhiko Iki Naoya Morohashi Sotaro Miyano 《Journal of inclusion phenomena and macrocyclic chemistry》2002,42(1-2):89-98
X-Ray crystal structures of the mono-, di-, and tri(p-tert-butyl)-substituted thiacalix[4]arenes (TC4As; 1, 2, and 3, respectively) have beendetermined. TC4As 1–3 adopt a cone conformation and form dimeric self-inclusion units in such a manner that phenol moieties are inserted into the cavity of each molecule. In all the crystal structures of 1–3, lateralface-to-face interactions exist between the phenol rings that do not bear a tert-butyl substituent, and seemingly, this molecular assembly stabilizes the formation of self-inclusion. TC4As 1 and 2 adopt a cone conformation with C2 symmetry, leading to the formation of rim-to-rim intermolecular hydrogenbonds so as to link the dimeric units up and down. On the other hand, 3 adopts a regular cone conformation with C4 symmetry to form cyclic hydrogen bonds withinthe rim part of TC4A. 相似文献