5,791 research outputs found
Copper clusters built on bulky amidinate ligands: spin delocalization via superexchange rather than direct metal-metal bonding
No full textEntry into a new class of tetra- and dicopper clusters was assisted by a fine steric tuning of bulky amidinate ligands that provide spin-delocalizing superexchange pathways in class III mixed-valence clusters, the properties of which are best understood without invoking metal-metal bonding
Synchronous division induced in Escherichia coli K12 by gemts mutants of phage Mu.
No full textInfection with the bacteriophage mutant Mu c+ gemts2 at 42 degrees C induces synchrony in cell division in cultures of Escherichia coli K12. This synchrony may last for several cycles and is not only due to selection since synchronization is observed even when bacterial survival to the infection is over 80% as in lysogens for Mu c+ gemts2. The mechanism by which synchrony is induced is not known, but since the product of Mu gene gem (previously called lig) has been shown to interact with the enzymatic system in the bacteria controlling the degree of DNA supercoiling, the phenomenon could be a consequence of this interaction
Opioid mediated activity and expression of mu and delta opioid receptors in isolated human term non-laboring myometrium
No full textThe existence of opioid receptors in mammalian myometrial tissue is now widely accepted. Previously enkephalin degrading enzymes have been shown to be elevated in pregnant rat uterus and a met-enkephalin analogue has been shown to alter spontaneous contractility of rat myometrium. Here we have undertaken studies to determine the effects of met-enkephalin on in vitro human myometrial contractility and investigate the expression of opioid receptors in pregnant myometrium. Myometrial biopsies were taken from women undergoing elective caesarean delivery at term. Organ bath experiments were used to investigate the effect of the met-enkephalin analogue [d-Ala 2, d-met 5] enkephalin (DAMEA) on spontaneous contractility. A confocal immunofluorescent technique and real time PCR were used to determine the expression of protein and mRNA, respectively for two opioid receptor subtypes, mu and delta. DAMEA had a concentration dependent inhibitory effect on contractile activity (1×10−7 M–1×10−4 M; 54% reduction in contractile activity, P<0.001 at 1×10−4 M concentration). Mu and delta opioid receptor protein sub-types and their respective mRNA were identified in all tissues sampled. This is the first report of opioid receptor expression and of an opioid mediated uterorelaxant action in term human non-labouring myometrium in vitroSB. 21/03/201
Hydrogen transfer between ligands: A density functional study of the rearrangement of M(eta(6)-C7H8)(2) into M(eta(7)-C7H7)(eta(5)-C7H9) [M = Mo, Mo+, Zr]
No full textThe electronic structure of the family of sandwich complexes M(eta(6)-C7H8)(2) and M(eta(7)-C7H7)-(eta(5)-C7H9) (M = Mo, Mo+, Zr) was investigated using density functional theory, and their geometries were accounted for. The mechanism for conversion of M(eta(6)-(CH8)-H-7)(2) into M(eta(7)-C7H7)(eta(5)-C7H9) by hydrogen transfer was investigated, and the experimental trends were reproduced. The neutral Mo species was calculated to have an activation free energy 13 kJ mol(-1) lower than the cationic Mo+. The rate-limiting step for the transfer in the neutral molybdenum species is breaking of the C-H bond to form a molybdenum hydride intermediate, which rapidly converts into the rearranged product. The transition state is late on the reaction coordinate, and C-H bond breaking occurs after ring slippage to form an (eta(6), eta(4)) 16-electron species. The cationic molybdenum species has a similar reaction profile. The zirconium species is found to have two competing pathways both with higher activations energies: one with an (eta(7), eta(5)) Zr-H intermediate, the other occurring by direct transfer of the hydrogen without forming Zr-H species. The effect of adding PH3 to the zirconium system has also been studied, which has the effect of lowering the barrier to the direct transfer of hydrogen between the ligands
A validated model of serum Anti-Müllerian hormone from conception to menopause
No full text<p><b>Background:</b> Anti-Mullerian hormone (AMH) is a product of growing ovarian follicles. The concentration of AMH in blood may also reflect the non-growing follicle (NGF) population, i.e. the ovarian reserve, and be of value in predicting reproductive lifespan. A full description of AMH production up to the menopause has not been previously reported.</p>
<p><b>Methodology/Principal Findings:</b> By searching the published literature for AMH concentrations in healthy pre-menopausal females, and using our own data (combined n=3,260) we have generated and robustly validated the first model of AMH concentration from conception to menopause. This model shows that 34% of the variation in AMH is due to age alone. We have shown that AMH peaks at age 24.5 years, followed by a decline to the menopause. We have also shown that there is a neonatal peak and a potential pre-pubertal peak. Our model allows us to generate normative data at all ages.</p>
<p><b>Conclusions/Significance:</b> These data highlight key inflection points in ovarian follicle dynamics. This first validated model of circulating AMH in healthy females describes a transition period in early adulthood, after which AMH reflects the progressive loss of the NGF pool. The existence of a neonatal increase in gonadal activity is confirmed for females. An improved understanding of the relationship between circulating AMH and age will lead to more accurate assessment of ovarian reserve for the individual woman.</p>
Analysis of Plasmodium falciparum diversity in natural infections by deep sequencing.
No full textMalaria elimination strategies require surveillance of the parasite population for genetic changes that demand a public health response, such as new forms of drug resistance. Here we describe methods for the large-scale analysis of genetic variation in Plasmodium falciparum by deep sequencing of parasite DNA obtained from the blood of patients with malaria, either directly or after short-term culture. Analysis of 86,158 exonic single nucleotide polymorphisms that passed genotyping quality control in 227 samples from Africa, Asia and Oceania provides genome-wide estimates of allele frequency distribution, population structure and linkage disequilibrium. By comparing the genetic diversity of individual infections with that of the local parasite population, we derive a metric of within-host diversity that is related to the level of inbreeding in the population. An open-access web application has been established for the exploration of regional differences in allele frequency and of highly differentiated loci in the P. falciparum genome
Low-Threshold Continuous-Wave Operation of Distributed-Feedback Quantum Cascade Laser at lambda similar to 4.6 mu m
No full textRoom-temperature continuous-wave (CW) operation of distributed-feedback quantum cascade laser (DFB-QCL) emitting at 4.6 mu m is presented. Strain-compensation combined with two-phonon resonance in active region design promises low-threshold current density. A record low-threshold current density of 1 kA/cm (2) for DFB-QCL operated in CW mode at 30 degrees C is realized without a high-reflectivity coating on the rear facet. Reliable dynamic single-mode emission with a sidemode suppression ratio of about 30 dB is achieved from 10 to 50 degrees C
Terminal vanadium - Neopentylidyne complexes and intramolecular cross-metathesis reactions to generate azametalacyclohexatrienes
No full textTerminal and four-coordinate vanadium(IV) phosphinidene complexes. A pseudo Jahn-Teller effect of second order stabilizing the V-P multiple bond
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