- Synthetic approach for unsaturated precursors for parahydrogen induced polarization of choline and its analogs
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Reported here are (i) a new synthetic approach for preparation of (ii) a new compound class, of -OH, for example, an -OH group is replaced with acetyl protecting group, protected 1,2-dehydrocholine analogs and (iii) a new synthetic route for betaine aldehyde. The C=C bond of 1,2-dehydrocholine moiety can be used for molecular addition of parahydrogen producing -OH protected hyperpolarized choline by parahydrogen-induced polarization (PHIP). The reported synthetic approach allows for incorporation of 15N and deuterium labels, which are necessary for preparation of highly polarized PHIP contrast agents. Isotope labeling with 15N and/or deuterium was conducted. Hyperpolarized 15N-choline enabled by the reported synthetic approach can be potentially used as an imaging biomarker of cancer similar to choline positron emission tomography tracers. Copyright
- Shchepin, Roman V.,Chekmenev, Eduard Y.
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p. 655 - 662
(2014/01/06)
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- Purification and characterization of an alkaliphilic choline oxidase of fusarium oxysporum
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A novel choline oxidase found in a fungus, Fusarium oxysporum strain V2, was purified to homogeneity as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme has a molecular mass of 128 kDa and consists of two identical subunits. The purified enzyme showed adsorption peaks at 340nm and 450 nm. It showed alkaliphilic pH characteristics: its optimum pH was 9.0-10.0, and it was stable at pH 8.0- 10.2. The Michaelis constant (Km) values for choline and betaine aldehyde were 0.28mM and 0.39mM respectively. Trimethylamino-alcohols, dimethylaminoalcohols, and diethylaminoethanol were substrates for the enzyme, but the Km values for them increased with decreasing numbers of methyl groups on the ammonium headgroup. A marked decrease in the maximum velocity (Vmax) and Vmax/Km values was observed when Nreplaced choline analogs were used as substrate instead of choline. The enzyme had a remarkably higher affinity for choline and betaine aldehyde than do previously reported enzymes. The enzyme oxidized these two substrates more quickly than a choline oxidase from Arthrobacter globiformis, and oxidation by the V2 enzyme was accompanied by an increase in the stoichometric amount of hydrogen peroxide.
- Enokibara, Shogo
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p. 2219 - 2224
(2013/02/25)
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