Stable isotope ratios of hydrogen and oxygen in microbes have been shown to be functions of the corresponding isotope ratios of the water with which the culture medium was prepared, and thus to contain a potential geographic signal. Water can evaporate from agar (solid) media during culturing, changing its isotope ratios. Here we describe the effect of drying on the isotope ratios of water extr...

In order to study the initial as well as the final steps in the aromatization of androgens to estrogens, highspecific activity [ 19-CSHs]androstenedione and testosterone were synthesized. Incubations of [ 19-CSHs]androstenedione with human placental microsomes resulted in the generation of [‘Hlwater, as a result of the dual hydroxylation at (2-19, and [’Hlformic acid reflecting final aromatizat...

The synthesis of a unique isotope engineered system, double-wall carbon nanotubes with natural carbon outer and highly 13C enriched inner walls, is reported from isotope enriched fullerenes encapsulated in single-wall carbon nanotubes (SWCNTs). The material allows the observation of the D line of the highly defect-free inner tubes that can be related to a curvature induced enhancement of the el...

Muon-spin rotation (μSR) studies of the oxygen isotope (O/O) effect (OIE) on the in-plane magnetic field penetration depth λab in cuprate high-temperature superconductors (HTS) are presented. First, the doping dependence of the OIE on the transition temperature Tc in various HTS is briefly discussed. It is observed that different cuprate families show a similar doping dependence of the OIE on T...

Hydrogen atom transfer reactions between the substrate and coenzyme are key mechanistic features of all adenosylcobalamin-dependent enzymes. For one of these enzymes, glutamate mutase, we have investigated whether hydrogen tunneling makes a significant contribution to the mechanism by examining the temperature dependence of the deuterium kinetic isotope effect associated with the transfer of a ...

Ab initio simulations that account for nuclear quantum effects have been used to examine the order-disorder transition in squaric acid, a prototypical H-bonded antiferroelectric crystal. Our simulations reproduce the >100 K difference in transition temperature observed upon deuteration as well as the strong geometrical isotope effect observed on intermolecular separations within the crystal. We...

The numerical calculations of the standard Eliashberg-Nambu strong coupling theory and a formula of isotope effect derived in this paper provide direct evidences that an-harmonic vibrations of lattice enhance isotope effect with anomalous coefficient α > 1/2. The results in this paper explain very well the wide distributed α values for the samples with different ratios of substitutions of 12C b...