Biomedical subjects

Juske Horita

Publications and source records attributed to Juske Horita.

4 recordsLinked to original sources

PubMed2006

Liquid-vapor isotopic fractionation factors of diatomic fluids: a direct comparison between molecular simulation and experiment.

Liquid-vapor fractionation factors of molecular fluids are studied by molecular-based simulation, Gibbs ensemble Monte Carlo, and isothermal-isochoric molecular dynamics of realistic models for N(2), O(2), and CO. The temperature dependence of the fractionation factors for (15)N(14)N(14)N(2), (15)N(2)(14)N(2), (18)O(16)O(16)O(2), (18)O(2)(16)O(2), (13)C(16)O(12)C(16)O, and (12)C(18)O(12)C(16)O along the vapor-liquid coexistence curves as predicted by simulation is compared with the existing experimental data to assess the accuracy of Planck's(2)-order Kirkwood-Wigner free energy expansion for specific model parametrizations. Predictions of the fractionation factors for other isotopologue pairs, including (18)O(17)O(16)O(2), (16)O(17)O(16)O(2), and (17)O(2)(16)O(2), as well as tests of some approximations behind the microscopic interpretation of the fractionation factors are also given.

Journal Article↗

PubMed2005

Perchlorate isotope forensics.

Perchlorate has been detected recently in a variety of soils, waters, plants, and food products at levels that may be detrimental to human health. These discoveries have generated considerable interest in perchlorate source identification. In this study, comprehensive stable isotope analyses (37Cl/35Cl and 18O/17O/16O) of perchlorate from known synthetic and natural sources reveal systematic differences in isotopic characteristics that are related to the formation mechanisms. In addition, isotopic analyses of perchlorate extracted from groundwater and surface water demonstrate the feasibility of identifying perchlorate sources in contaminated environments on the basis of this technique. Both natural and synthetic sources of perchlorate have been identified in water samples from some perchlorate occurrences in the United States by the isotopic method.

Journal Article↗

PubMed2003

Stable-isotope fingerprints of biological agents as forensic tools.

Naturally occurring stable isotopes of light elements in chemical and biological agents may possess unique "stable-isotope fingerprints" depending on their sources and manufacturing processes. To test this hypothesis, two strains of bacteria (Bacillus globigii and Erwinia agglomerans) were grown under controlled laboratory conditions. We observed that cultured bacteria cells faithfully inherited the isotopic composition (hydrogen, carbon, and nitrogen) of media waters and substrates in predictable manners in terms of bacterial metabolism and that even bacterial cells of the same strain, which grew in media water and substrates of different isotopic compositions, have readily distinguishable isotopic signatures. These "stable-isotopic fingerprints" of chemical and biological agents can be used as forensic tools in the event of biochemical terrorist attacks.

Bacillus↗

PubMed2002

Carbon isotopic fractionations associated with thermophilic bacteria Thermotoga maritima and Persephonella marina.

Stable carbon isotopes can provide insight into carbon cycling pathways in natural environments. We examined carbon isotope fractionations associated with a hyperthermophilic fermentative bacterium, Thermotoga maritima, and a thermophilic chemolithoautotrophic bacterium Persephonella marina. In T. maritima, phospholipid fatty acids (PLFA) are slightly enriched in 13C relative to biomass (epsilon = 0.1-0.8 per thousand). However, PLFA and biomass are depleted in 13C relative to the substrate glucose by approximately 8 per thousand. In P. marina, PLFA are 1.8-14.5 per thousand enriched in 13C relative to biomass, which suggests that the reversed tricarboxylic acid (TCA) cycle or the 3-hydroxypropionate pathway may be used for CO2 fixation. This is supported by small fractionation between biomass and CO2 (epsilon = -3.8 per thousand to -5.0 per thousand), which is similar to fractionations reported for other organisms using similar CO2 fixation pathways. Identification of the exact pathway will require biochemical assay for specific enzymes associated with the reversed TCA cycle or the 3-hydroxypropionate pathway.

Carbon Dioxide↗