Knowledge of carbon isotope fractionation is needed in order to discuss the formation and dissociation of naturally occurring CO hydrates. We investigated carbon isotope fractionation during CO hydrate formation and measured the three-phase equilibria of CO-HO and CO-HO systems. From a crystal structure viewpoint, the difference in the Raman spectra of hydrate-bound CO and CO was revealed, although their unit cell size was similar. The δC of hydrate-bound CO was lower than that of the residual CO (1.0-1.5‰) in a formation temperature ranging between 226 K and 278 K. The results show that the small difference between equilibrium pressures of ~0.01 MPa in CO and CO hydrates causes carbon isotope fractionation of ~1‰. However, the difference between equilibrium pressures in the CO-HO and CO-HO systems was smaller than the standard uncertainties of measurement; more accurate pressure measurement is required for quantitative discussion.
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http://dx.doi.org/10.3390/molecules26144215 | DOI Listing |
Biology (Basel)
December 2024
School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea.
In seasonally stratified marine environments, the dynamics of benthic-pelagic coupling plays a crucial role in shaping food web structures and fisheries production. We examined fish food web structures across three distinct shelf areas in the Southern Sea of Korea (SSK) during both stratified (summer) and mixed (spring) water conditions using stable isotopes of carbon (δC) and nitrogen (δN). In spring, fish communities exhibited a broader range of δC values compared with summer, indicating more diverse feeding strategies.
View Article and Find Full Text PDFBiology (Basel)
November 2024
Biology Department, University of New Mexico, Albuquerque, NM 87131-0001, USA.
Maps of (baseline) δC and δN values of primary producers or consumers near the base of food webs provide crucial information for interpreting patterns in the isotopic composition of consumers that occupy higher trophic levels. In marine systems, understanding how oceanographic variables influence these values enables the creation of dynamic isoscapes across time and space, providing insights into how ecosystems function. The San Jorge Gulf (SJG) in the southwest Atlantic Ocean (45° S-47° S) is an area of particular importance, as it is located on one of the most productive continental shelves in the world, supporting large fisheries and marine mammal and seabird populations.
View Article and Find Full Text PDFInt J Biol Macromol
January 2025
Key Laboratory of Organosilicon Chemistry and Materials Technology, Ministry of Education; College of Materials Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou, Zhejiang 311121, China. Electronic address:
Keto reductases are crucial NAD(P)H-dependent enzymes used for the enantioselective synthesis of alcohols from prochiral ketones. Typically, the NADPH cofactor is regenerated through a second enzyme and/or substrate. However, photocatalytic cofactor regeneration using water as a sacrificial electron and hydrogen donor presents a promising alternative, albeit a challenging one.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
January 2025
Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095.
The elemental and isotopic abundances of major species in the Martian atmosphere have been determined, but analyses often lack sufficient precision, and those of minor and trace species are frequently not well known. Many important questions about the evolution and current state of Mars require the kind of knowledge that can be gained from analysis of a returned sample of the Martian atmosphere. Key target species include the noble gases, nitrogen, and various species containing carbon, hydrogen, and oxygen, such as methane.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
January 2025
School of Physical Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom.
Much has been learned about Mars through data returned from space missions and analyses of martian meteorites. There are, however, many questions still outstanding which cannot currently be answered-including the issue of whether there is, or was, life on Mars. The return of a cache of samples-including of the atmosphere-from separate locations in Jezero Crater and with differing petrogeneses will provide the international community with the opportunity to explore part of the evolutionary history of Mars in great detail.
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