High-Pressure Iron-Sulfur Compound, Fe3S2, and Melting Relations in the Fe-FeS System

An iron-sulfur compound (Fe3S2) was synthesized at pressures greater than 14 gigapascals in the system Fe-FeS. The formation of Fe3S2 changed the melting relations from a simple binary eutectic system to a binary system with an intermediate compound that melted incongruently. The eutectic temperature in the system at 14 gigapascals was about 400°C lower than that extrapolated from Usselman's data, implying that previous thermal models of Fe-rich planetary cores could overestimate core temperature. If it is found in a meteorite, the Fe3S2 phase could also be used to infer the minimum size of a parent body.     

The site of attachment in human rhinovirus 14 for antiviral agents that inhibit uncoating

WIN 51711 and WIN 52084 are structurally related, antiviral compounds that inhibit the replication of rhino (common cold) viruses and related picornaviruses. They prevent the pH-mediated uncoating of the viral RNA. The compounds consist of a 3-methylisoxazole group that inserts itself into the hydrophobic interior of the VP1 beta-barrel, a connecting seven-membered aliphatic chain, and a 4-oxazolinylphenoxy group (OP) that covers the entrance to an ion channel in the floor of the "canyon." Viral disassembly may be inhibited by preventing the collapse of the VP1 hydrophobic pocket or by blocking the flow of ions into the virus interior.     

Involvement of mammalian Mus81 in genome integrity and tumor suppression

Mus81-Eme1 endonuclease has been implicated in the rescue of stalled replication forks and the resolution of meiotic recombination intermediates in yeast. We used gene targeting to study the physiological requirements of Mus81 in mammals. Mus81-/- mice are viable and fertile, which indicates that mammalian Mus81 is not essential for recombination processes associated with meiosis. Mus81-deficient mice and cells were hypersensitive to the DNA cross-linking agent mitomycin C but not to gamma-irradiation. Remarkably, both homozygous Mus81-/- and heterozygous Mus81+/- mice exhibited a similar susceptibility to spontaneous chromosomal damage and a profound and equivalent predisposition to lymphomas and other cancers. These studies demonstrate a critical role for the proper biallelic expression of the mammalian Mus81 in the maintenance of genomic integrity and tumor suppression.     

Sexual selection can resolve sex-linked sexual antagonism

Sexual selection is a potent evolutionary force. However, very few models have considered the evolution of female preferences for traits expressed in both sexes. Here we explore how female preferences coevolve with sexually antagonistic traits, which involve alleles that are beneficial to one sex but harmful to the other. We show that with a sexually antagonistic trait on the X chromosome (males XY, females XX), females evolve to prefer mates carrying alleles beneficial to daughters. In contrast, with a Z-linked trait (males ZZ, females ZW), females more often evolve mating preferences for mates carrying alleles beneficial to sons (that is, flashy displays).     

Imaging nucleophilic substitution dynamics

Anion-molecule nucleophilic substitution (S(N)2) reactions are known for their rich reaction dynamics, caused by a complex potential energy surface with a submerged barrier and by weak coupling of the relevant rotational-vibrational quantum states. The dynamics of the S(N)2 reaction of Cl- + CH3I were uncovered in detail by using crossed molecular beam imaging. As a function of the collision energy, the transition from a complex-mediated reaction mechanism to direct backward scattering of the I- product was observed experimentally. Chemical dynamics calculations were performed that explain the observed energy transfer and reveal an indirect roundabout reaction mechanism involving CH3 rotation.     

A conserved family of enzymes that phosphorylate inositol hexakisphosphate

Inositol pyrophosphates are a diverse group of high-energy signaling molecules whose cellular roles remain an active area of study. We report a previously uncharacterized class of inositol pyrophosphate synthase and find it is identical to yeast Vip1 and Asp1 proteins, regulators of actin-related protein-2/3 (ARP 2/3) complexes. Vip1 and Asp1 acted as enzymes that encode inositol hexakisphosphate (IP6) and inositol heptakisphosphate (IP7) kinase activities. Alterations in kinase activity led to defects in cell growth, morphology, and interactions with ARP complex members. The functionality of Asp1 and Vip1 may provide cells with increased signaling capacity through metabolism of IP6.     

Amplification of acetylcholine-binding catenanes from dynamic combinatorial libraries

Directed chemical synthesis can produce a vast range of molecular structures, but the intended product must be known at the outset. In contrast, evolution in nature can lead to efficient receptors and catalysts whose structures defy prediction. To access such unpredictable structures, we prepared dynamic combinatorial libraries in which reversibly binding building blocks assemble around a receptor target. We selected for an acetylcholine receptor by adding the neurotransmitter to solutions of dipeptide hydrazones [proline-phenylalanine or proline-(cyclohexyl)alanine], which reversibly combine through hydrazone linkages. At thermodynamic equilibrium, the dominant receptor structure was an elaborate [2]-catenane consisting of two interlocked macrocyclic trimers. This complex receptor with a 100 nM affinity for acetylcholine could be isolated on a preparative scale in 67% yield.     

Synthesis of Novel Thin-Film Materials by Pulsed Laser Deposition

Pulsed laser deposition (PLD) is a conceptually and experimentally simple yet highly versatile tool for thin-film and multilayer research. Its advantages for the film growth of oxides and other chemically complex materials include stoichiometric transfer, growth from an energetic beam, reactive deposition, and inherent simplicity for the growth of multilayered structures. With the use of PLD, artificially layered materials and metastable phases have been created and their properties varied by control of the layer thicknesses. In situ monitoring techniques have provided information about the role of energetic species in the formation of ultrahard phases and in the doping of semiconductors. Cluster-assembled nanocrystalline and composite films offer opportunities to control and produce new combinations of properties with PLD.     

A slowly progressive retinopathy in the Shetland Sheepdog

Objective To describe a slowly progressive retinopathy (SPR) in Shetland Sheepdogs. Animals Forty adult Shetlands Sheepdogs with ophthalmoscopic signs of SPR and six normal Shetland Sheepdogs were included in the study. Procedure Ophthalmic examination including slit‐lamp biomicroscopy and ophthalmoscopy was performed in all dogs. Electroretinograms and obstacle course‐test were performed in 13 affected and 6 normal dogs. The SPR dogs were subdivided into two groups according to their dark‐adapted b‐wave amplitudes. SPR1‐dogs had ophthalmoscopic signs of SPR, but normal dark‐adapted b‐wave amplitudes. Dogs with both ophthalmoscopic signs and subnormal, dark‐adapted b‐wave amplitudes were assigned to group SPR2. Eyes from two SPR2 dogs were obtained for microscopic examination. Results The ophthalmoscopic changes included bilateral, symmetrical, greyish discoloration in the peripheral tapetal fundus with normal or marginally attenuated vessels. Repeated examination showed that the ophthalmoscopic changes slowly spread across the central parts of the tapetal fundus, but did not progress to obvious neuroretinal thinning presenting as tapetal hyper‐reflectivity. The dogs did not appear seriously visually impaired. SPR2 showed significantly reduced b‐wave amplitudes throughout dark‐adaptation. Microscopy showed thinning of the outer nuclear layer and abnormal appearance of rod and cone outer segments. Testing for the progressive rod–cone degeneration ( prcd )‐mutation in three dogs with SPR was negative. Conclusion Slowly progressive retinopathy is a generalized rod–cone degeneration that on ophthalmoscopy looks similar to early stages of progressive retinal atrophy. The ophthalmoscopic findings are slowly progressive without tapetal hyper‐reflectivity. Visual impairment is not obvious and the electroretinogram is more subtly altered than in progressive retinal atrophy. The etiology remains unclear. SPR is not caused by the prcd‐mutation.     

Predictions of soil water and crop growth dynamics using the agroecosystem models THESEUS and OPUS

The agroecosystem models THESEUS and OPUS were tested with data obtained from three agricultural experimental field plots on sandy soils without groundwater located at the moraine landscape in East Brandenburg, Germany. At each of these plots, a separate agricultural management practice was applied. Measurements of soil water contents, pressure heads, above‐ground crop biomass, and crop yield from these three plots were compared with the corresponding simulation results of both models. The comparisons of simulated with measured outputs were analyzed using the modeling‐efficiency index IA. According to these analyses, both models simulated adequately the time courses of volumetric soil water contents and above‐ground crop biomass, but the time courses of pressure heads were predicted with a lower quality by both models. As for the pressure heads, the yields simulated with both models showed greater discrepancies in comparison with the observed ones. This indicates the need of a site‐specific parameter calibration of the crop‐growth modules, especially for that included in OPUS .