Publications by authors named "Noriaki Yamauchi"

Screening is a fundamental strategy for early detection, treatment, and prevention of progression of oral disease and those at high risk for oral disease. While numerous screening tools exist, questionnaires, and saliva tests are often suitable for screening. The questionnaire based on the PRECEDE-PROCEED model was developed, validated, and elucidated on the structural interrelationship between these two methods.

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Rationale: Archaea have characteristic membrane lipids including diether and/or tetraether isoprenoidal core lipids with various polar head groups. Since the polar group is removed soon after the end of archaeal activity, the occurrences of core and polar lipids are regarded as dead and active signals, respectively. The core and polar lipids have generally been analyzed separately using atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI), respectively, coupled with mass spectrometry.

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The stereochemical reaction course for the two C-3 hydrogens of leucine to produce a characteristic isoprenoidal lipid in halophilic archaea was observed using incubation experiments with whole cell Halobacterium salinarum. Deuterium-labeled (3R)- and (3S)-[3-H]leucine were freshly prepared as substrates from 2,3-epoxy-4-methyl-1-pentanol. Incorporation of deuterium from (3S)-[3-H]leucine and loss of deuterium from (3R)-[3-H]leucine in the lipid-core of H.

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L-Gulose is a very rare sugar, but appears as a sugar component of the main polar lipids characteristic in such a thermophilic archaeon as Thermoplasma acidophilum that lives without cell walls in a highly acidic environment. The biosynthesis of L-gulose in this thermophilic organism was investigated with deuterium-labeling experiments. L-Gulose was found to be biosynthesized from D-glucose via stepwise stereochemical inversion at C-2 and C-5.

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The pathway of leucine to mevalonate, which has attracted attention in the study of the biosynthesis of isoprenoid in parasitic protozoa and myxobacterium, was observed in the biosynthesis of the lipid core in halophilic archaea. The involvement of isovaleryl-CoA dehydrogenase was strongly suggested, with stereospecific conversion of the diastereotopic methyl group of leucine to isoprenoidal lipid.

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Two isotopomers of deuterium-labeled leucine in the diastereotopic methyl group were synthesized from inexpensively available (R)- and (S)-citronellol in a more convenient way than by previous methods.

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The structural features of humic acid (HA) at the sediment surface of the tideland at the Hayatsuegawa-river mouth at the Ariake Sea were investigated for the utilization of HA toward an environmental indicator of the features of the river basin and coastal region. 1H NMR analysis revealed a high-content hydrocarbon residue with a similar type of terrigenous HA. Direct and methylation-pyrolysis-GC analysis suggested the incorporation of long-chain carboxylate in HA in the tidelands.

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Calditocaldarchaeol (neutral tetraether lipid) from Sulfolobus acidocaldarius (acidothermophilic archaea) and intact total lipid from the thermoacidophilic archaea Sulfolobus sp. was examined by electrospray ionization time-of-flight mass spectrometry in the negative-ion mode using high resolution. When the sample was injected as a solution in a 3:1 mixture of methanol (MeOH) and chloroform (CHCl(3)) using an infusion system, the total ether lipid afforded molecular-related ions as [M - H](-) for acidic polar lipids containing a phosphoric or sulfuric group, and as [M + Cl](-) ion for neutral glycolipids.

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