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Biomedical subjects

K Tsukida

Publications and source records attributed to K Tsukida.

14 recordsLinked to original sources
PubMed1992

Optical resolution of (+/-)-all-trans-3-hydroxyretinal by use of high-performance liquid chromatography.

Racemic all-trans-3-hydroxyretinal (3-OH-RAL) (1) was converted by a reaction with (-)-camphanic acid chloride (CpCl) into a diastereomixture of camphanates (2a) and (2b) which was separated by preparative high-performance liquid chromatography (HPLC) to give two esters (2a) and (2b) in pure state, respectively. Saponification of (2a) and (2b) independently afforded optically active (3S)- and (3R)-3-OH-RALs (3a) and (3b), respectively, whose absolute structures were determined by circular dichroism (CD) spectra. Racemic 3-OH-RAL was separated to two peaks by HPLC using chiral column (ChiraSpher, Merck). Cochromatography with authentic specimens (3a) and (3b) showed that the peak with a short retention time corresponded to (3R)-isomer and the other to (3S).

Chromatography, High Pressure Liquid↗
PubMed1979

Photochemical reaction of 9-cis-retro-gamma-rhodopsin at low temperatures.

9-cis-Retro-gamma-rhodopsin (lambda max = 420 nm) was prepared from 9-cis-retro-gamma-retinal and cattle opsin. After cooling to liquid nitrogen temperature (77 K), the pigment was irradiated with light at 380 nm. The spectrum shifted to the longer wavelengths, owing to formation of a batho product. This fact indicates that the conjugated double bond system from C-5 to C-8 of the chromophoric retinal in rhodopsin was not necessary for formation of bathorhodopsin. Reirradiation of the batho product with light at wavelengths longer than 520 nm yielded a mixture composed of presumably 9- or 11-cis forms of retro-gamma-rhodopsin. These three isomers are interconvertible by light at liquid nitrogen temperature. Thus the retro-gamma-rhodopsin system is similar in photochemical reaction at 77 K to cattle rhodopsin system. Each system has its own batho product. Based on these results, it was infered that the formation of batho-rhodopsin is due to photoisomerization of the chromophoric retinal of rhodopsin and is not due to translocation of a proton on the ring or on the side chain from C-6 to C-8 of the chromophoric retinal to the Schiff-base nitrogen.

Animals↗
PubMed1978

Mechanism for interference of hydrochlorothiazide with the Kober reaction for determination of urinary estriol in pregnancy.

Investigation of the mechanism of the lowering effect of hydrochlorothiazide, which was administered orally, in the determination of estriol from the pregnancy urine has been carried out. The isolation and determination of the structure of a copolymer formed from estriol and formaldehyde have suggested the mechanism by which, during the acid hydrolysis process of the glucuronide conjugate of estriol, some copolymers of estriol and formaldehyde generated from hydrochlorothiazide, were formed, thus lowering the observed values of the estriol contents in the urine.

Colorimetry↗
PubMed1978

Electrocyclization reaction of higher conjugated polyenals: photochemical behaviors of retinal (vitamin A1 aldehyde) homologues.

During the studies on a photoreaction of retinal, involving various kinds of (Z)-(E) isomerization, a heretofore unknown photoproduct of retinal was isolated in a pure state and was characterized unambiguously. Thus, direct irradiation of all-(E)-retinal (I) and of all-(E)-beta-ionylidenecrotonaldehyde (II) in acetonitrile solution gave the corresponding 6e-electrocyclized photoproducts, (III) and (IV), both via the possible 7-(Z)-isomer intermediates of the parent conjugated polyenals. Unlike the lower members in the retinal series, it was also confirmed that sigmatropic rearrangement or photo-Diels-Alder reaction hardly proceeds in these higher members of the series mentioned above.

Acetonitriles↗
PubMed1977

Simultaneous determination of cis-trans isomeric retinals by high-performance liquid chromatography.

A high-performance liquid chromatographic method for the simultaneous determination of geometric isomers of retinal in a mixture has been developed. The method can be applied to problems such as determination of optimal conditions for the preparation of a particular isomer, or the investigation of novel photoproducts from retinal. Aprotic solvent effects on cis-trans isomerization are discussed.

Chromatography, High Pressure Liquid↗
PubMed1976

Simultaneous determination of eight vitamin D2 isomers by high-speed liquid chromatography.

The simultaneous determination of vitamin D2 and its isomers by high-speed liquid chromatography (HSLC) is described. Preferred operating conditions for the resolution and quantitation of vitamin D2 5,6-trans-vitamin D2, ergosterol, lumisterol2, isovitamin D2, isotachysterol2, tachysterol2, and previtamin D2 are as follows: column, "Zorbax" SIL (25 cm x 2.1 mm i.d.); pressure, 100-120 kg/cm2; temperature, ambient; detector, UV 254 nm; mobile phase, 0.15% methanol + 2% ether in pentane (for the simultaneous determination), 10% ether in hexane (for quantitation of the practical sets of isomers), or 55% CHCl3 (distilled) in pentane (for separation of isovitamin D2 and 5,6-trans-vitamin D2); sample size, 1 mul (greater than 1-5 ng); internal standard, p-cresol or alpha-naphthol. High-speed, good resolution, precise and accurate trace analysis, greater analysis flexibility, no necessity for preparing derivatives, and gentle operating conditions are main potential advantages of our method which has proved to be very efficient and surpasses all analytical procedures hitherto proposed.

Chemical Phenomena↗
PubMed1976

Simultaneous determination of eight vitamin D2 isomers by proton magnetic resonance spectroscopy.

Simultaneous determination of vitamin D2 and its isomers, with the aid of pmr employing a paramagnetic shift reagent Eu (dpm)3, is presented. Thus, a mixture of vitamin D2 isomers is acetylated and its pmr spectra are run with and without the addition of the shift reagent. Relative paramagnetic shift values (gamma rel) of the acetoxyl protons of the acetylated isomers are estimated for solutions in CCl4 against the reference acetoxyl signal of vitamin D2 acetate. Estimated values are as follows: vitamin D2 acetate = 100, 5,6-trans-vitamin D2 acetate = 71 +/- 1, ergosteryl acetate = 86 +/- 1, lumisteryl2 acetate = 123 +/- 3, isovitamin D2 acetate = 82, isotachysteryl2 acetate = 97, tachysteryl2 acetate = 100 (105 +/- 1 in C6D6), and previtamin D2 acetate = 80 +/- 2. On the basis of a dramatic shift of an acetoxyl signal and a constancy of each gamma rel, this method permits immediate identification of the isomers and provides valuable information on their stereochemistry. This technique also facilitates a simultaneous determination of these isomers in a mixture by estimating each signal area.

Chemical Phenomena↗
PubMed1975

Carbon-13 nuclear magnetic resonance spectra of vitamins D and related compounds.

1. The natural abundance carbon-13 nmr of vitamins D (D2 and D3) and several isomers (5, 6-trans-vitamin D2, isotachysterol2 and isovitamin D2) have been completely assigned by employing off-resonance noise-decoupling, acetylation shifts, and lanthanide-induced shifts experiments. The last two techniques were especially useful for the present study. 2. Carbon-13 nmr spectral characteristics of the three main conjugated triene moieties (SE-Z-SZ, SE-E-SZ, or SE-E-SE), involved in the molecules of vitamin D and its isomers, were revealed. Thus, the striking dependence of the shieldings on molecular geometries and high sensitivity of the resonances to the environments of conjugated systems were surveyed. 3. Conformational preferences in solutions of the hydroxyl groups in vitamins D2 and D3 as well as 5, 6-trans-vitamin D2 were conveniently determined.

Carbon Isotopes↗