Ordering in a fluid inert gas confined by flat surfaces

High-resolution transmission electron microscopy images of room-temperature fluid xenon in small faceted cavities in aluminum reveal the presence of three well-defined layers within the fluid at each facet. Such interfacial layering of simple liquids has been theoretically predicted, but observational evidence has been ambiguous. Molecular dynamics simulations indicate that the density variation induced by the layering will cause xenon, confined to an approximately cubic cavity of volume approximately 8 cubic nanometers, to condense into the body-centered cubic phase, differing from the face-centered cubic phase of both bulk solid xenon and solid xenon confined in somewhat larger (>/=20 cubic nanometer) tetradecahedral cavities in face-centered cubic metals. Layering at the liquid-solid interface plays an important role in determining physical properties as diverse as the rheological behavior of two-dimensionally confined liquids and the dynamics of crystal growth.     

Requirement for DARPP-32 in progesterone-facilitated sexual receptivity in female rats and mice

DARPP-32, a dopamine- and adenosine 3',5'-monophosphate (cAMP)-regulated phosphoprotein (32 kilodaltons in size), is an obligate intermediate in progesterone (P)-facilitated sexual receptivity in female rats and mice. The facilitative effect of P on sexual receptivity in female rats was blocked by antisense oligonucleotides to DARPP-32. Homozygous mice carrying a null mutation for the DARPP-32 gene exhibited minimal levels of P-facilitated sexual receptivity when compared to their wild-type littermates. P significantly increased hypothalamic cAMP levels and cAMP-dependent protein kinase activity. These increases were not inhibited by a D1 subclass dopamine receptor antagonist. P also enhanced phosphorylation of DARPP-32 on threonine 34 in the hypothalamus of mice. DARPP-32 activation is thus an obligatory step in progestin receptor regulation of sexual receptivity in rats and mice.     

Ionization of liquids by radiation: measurement by charge scavenging

Pulse radiolysis of dilute solutions of triphenylcarbinol in saturated hydrocarbon gives spectra of the triphenylmethyl free radical, (C(6)H(5))(3)C., and cation, (C(6)H(5))(5)C(+). The yield of the ion is independent of the carbinol concentration, and is thought to measure the yield of free ions generated in the solvent. The relative yields of ions thus found in cyclohexane and 2,2,4-trimethylpentane agree with measurements made by the clearing-field method.     

The potential for grass-fed livestock: resource constraints

Using pasture and grazed forest-range for a system of producing live-stock by feeding grass alone reduces the inputs of energy about 60 percent and land resources about 8 percent, but also reduces by about half the production of animal protein in the United States. Under a system in which only grass was fed, livestock would be restricted to beef, milk, and lamb production. The amount of grain fed to U.S. livestock is about 135 million tons (metric) or about ten times the amount consumed by the U.S. population.     

The pentacovalent phosphorus intermediate of a phosphoryl transfer reaction

Enzymes provide enormous rate enhancements, unmatched by any other type of catalyst. The stabilization of high-energy states along the reaction coordinate is the crux of the catalytic power of enzymes. We report the atomic-resolution structure of a high-energy reaction intermediate stabilized in the active site of an enzyme. Crystallization of phosphorylated beta-phosphoglucomutase in the presence of the Mg(II) cofactor and either of the substrates glucose 1-phosphate or glucose 6-phosphate produced crystals of the enzyme-Mg(II)-glucose 1,6-(bis)phosphate complex, which diffracted x-rays to 1.2 and 1.4 angstroms, respectively. The structure reveals a stabilized pentacovalent phosphorane formed in the phosphoryl transfer from the C(1)O of glucose 1,6-(bis)phosphate to the nucleophilic Asp8 carboxylate.