Chemistry

With consideration to food hazards and its security, this research study was conducted to determine the concentration levels of some heavy metals in vegetables cultivated in Damboa, Nigeria. Fresh samples of vegetables; Cucumber (cucumis spp) and Onion (Allium cepa) were obtained from the farms in four villages, analysed by using Atomic Absorption Spectrophotometric (AAS) techniques. Results obtained showed variations in concentration in microgram per litre (µg / L). Eight heavy metals were determined; cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn). The analysis revealed that; Gumsuri – Ritawa village; the concentration levels in cucumber ranged from - 0.7 ± 0.06 to 5.7 ± 0.06, while in onion ranged from 0.2 ± 0.06 to 4.8 ± 0.06; highest is Cd (5.7 µg / L) in cucumber.  Gumsuri – Tolori village, concentration in cucumber ranged from -6.6 ± 0.06 to 0.82 ± 0.02, in onion is 0.27 ± 0.01; highest is Pb (0.9 µg / L) found in onio...

Replacing one or more of the carbon atoms in a fullerene cage with one or more non-carbon atoms is expected to result in a structure (heterofullerene) with significantly altered and potentially useful properties. While (C 59 N)-and (C 69 N)-based compounds can be synthesized via solution-phase modification of C 60 and C 70 , respectively, a general, high-yield method for producing heterofullerenes has not been identified. We report the results of a search for heterofullerenes using atmospheric pressure photo-ionization mass spectrometry on samples of fullerene soot produced in nitrogen and carbon monoxide via the Krätschmer-Huffman arc technique. Contrary to earlier reports, we found no evidence of the presence of heterofullerenes in any of the samples we examined. X-ray photoelectron spectroscopy of fullerene soot produced in nitrogen indicates that while nitrogen is incorporated into the carbon matrix, the observed nitrogen-carbon bonding configurations do not permit the formation of fullerenes. We also report the discovery of production conditions under which argon can be used as a buffer gas and the yield of soluble fullerenes is comparable to the best yield achievable using helium. These findings may shed light on the general problem of the fullerene formation process. =====================

Submonolayers of buckyball molecules (C~, 0) on a gold substrate, deposited under ultrahigh-vacuum (UHV) conditions, have been imaged in air using scanning tunneling microscopy (STM) and atomic force microscopy (AFM). STM images show intramolecular contrasts within mosl individual C~,~ molecules. AFM images of the C¢,I) molecules, often grouped in a hexagonal arrangement, show no atomic-scale features. A possible explanation for the presence or absence of the intramolecular contrasts in the images obtained with the STM and AFM, respectively, is given by a molecular orbital calculation.

The electronic interactions of fullerene molecules with metals, with other molecules, and with themselves are important to the chemical and conductive properties of these materials. We demonstrate high resolution scanning tunneling microscopy images of C, molecules condensed on epitaxial goid (111) films on mica, in which the C, molecules are isolated from each other. The C, molecules were locked in position to the gold substrate by an ordered layer of methyl isobutyl ketone. The images of the C, molecules exhibit intramolecular contrast indicating a significant electronic interaction with the gold substrate. Current versus voltage measurements show that both the Cso and the thin fii of methyl isobutyl ketone have conductances comparable to that of the gold substrate.

Carbon nanotubes, fabricated by the Ebbesen-Ajayan method, were imaged using scanning tunneling microscopy (STM) and atomic force microscopy (AFM) in air and were compared to images obtained with high-resolution transmission electron microscopy (HRTEM). The HRTEM images revealed an abundance of elongated structures ranging in diameter from 3.0 to 30 nm, and with lengths of up to 0.8/xm. Many of the structures possessed several graphitic shells as if the tubes were nested one in the other. Reproducible images of the tubular structures, typically 20 nm in diameter and with a large variation in length, were obtained with both STM and AFM when the nanotubes were deposited on hydrogen-terminated Si(111), confirming that the nested structures observed with HRTEM do indeed have a tubular morphology. No single-walled, bare nanotubes or spherical fullerenes (typical of the Kriitschmer-Huffman process) were observed.

The odd-numbered carbon clusters C 119 , C,2 and C, 39 have been observed in the mass spectra of toluene extacts of fullerene soots and of the products of ozone-fullerene reactions. Specifically, ozone-C6o reactions yield C 119 , and ozone-Cm reactions yield C 139 , and ozone-(%/C7C) reactions produce C 119 , C , 29, and C 139 . These unexpected species correspond to dimers of Cý0, C6/C7, and C7o, respectively, less one carbon atom, and are stable gas-phase ions with behavior similar to that of fullerenes. The results suggest a new route to functionalization and derivatization of fullerenes through controlled ozone-catalyzed cage-opening reactions.

The gas-phase infrared emission spectra of Cso and C,c were recorded by Fourier-transform spectroscopy. The measurements were carried out in the temperature range 500-950°C and the band positions were extrapolated to 0 K. In addition to the strong fundamental bands, numerous weak features were observed. We attribute these weak bands primarily to binary combination bands. Our measurements should prove useful for astronomical searches, low-temperature laboratory measurements and for detailed force-field calculations.

The Raman excitation profiles for CsO films grown on silicon reveal the existence of optical transitions near 2.4 eV, well below the lowest dipole-allowed absorption line predicted for isolated icosahedral molecules. These transitions are not observed in CeO dissolved in CSz. We propose an explanation in terms of a breakdown of the icosahedral inversion symmetry in ChO crystals.

As land is developed, the impervious surfaces that are created increase the amount of runoff during rainfall events, disrupting the natural hydrologic cycle, with an increment in volume of runoff and in pollutant loadings. Pollutants deposited or derived from an activity on the land surface will likely end up in stormwater runoff in some concentration, such as nutrients, sediment, heavy metals, hydrocarbons, gasoline additives, pathogens, deicers, herbicides and pesticides. Several of these pollutants are particulate-bound, so it appears clear that sediment removal can provide significant water-quality improvements and it appears to be important the knowledge of the ability of stromwater treatment devices to retain particulate matter. For this reason three different units which remove sediments have been tested through laboratory. In particular a roadside gully pot has been tested under steady hydraulic conditions, varying the characteristics of the influent solids (diameter, partic...

Indirect evidence suggests that nitric oxide inhibits sodium reabsorption by the collecting duct; however, direct evidence is lacking. It was hypothesized that endothelium-derived nitric oxide inhibits sodium flux in the cortical collecting duct by blocking amiloridesensitive . mm. Nitroglycerin did not significantly affect pump activity either. It was concluded that: ( 1) nitric oxide inhibits sodium flux in the cortical collecting duct, and (2) this occurs at least in part via amiloride-sensitive sodium channels.

The effect of endothelin-1 (ET-1) on the proximal tubule re- mains unclear. This may be due to a biphasic effect on transport in this segment. We hypothesized that ET-1 has a biphasic effect on fluid absorption (Jv) in the proximal straight tubule and that its inhibitory effect is superimposed on its stimulatory effect. ET-1 (10-13 M) stimulated Jv from 0.68±0.07 to 1.11±0.20 nl/mm/min, a 60% increase (P < 0.04). 10-12 and 1010 M ET-1 had no significant effect. 10-' M ET-1 reduced Jv from 0.81±0.19 to 0.44±0.15 nl/mm/min (P < 0.009). Staurosporine (STP, 10-s M) prevented both 10-9 and 10-13 M ET-1 from altering Jv significantly indicating that protein kinase C (PKC) is involved. Indomethacin (10 -M) blocked the inhibition produced by 10-9 M ET-1. ETI (10-' M), a lipoxygenase inhibitor, also blocked ET-1 inhibition of Jv. In- terestingly ET-1 (10-9 M) stimulated Jv in the presence of both indomethacin and ETI. When 10-9 M ET-1 was added in the presence of 10-' M quinacrine, a phospholipase (PL) inhib- itor, Jv also increased from 1.02±0.20 to 1.23±0.22 nl/mm/ min (P < 0.03). STP blocked this increase. We conclude that (a) 10-13 M ET-1 stimulates fluid absorption by activating PKC; (b) 10-9 M ET-1 decreases Jv by PKC-, PL-, cyclooxy- genase-, and lipoxygenase-dependent mechanisms; and (c) the inhibitory effect of ET-1 on Jv is superimposed on the stimula- tory effect. (

1. The role of synaptic activation of NMDA (N-methyl-D-aspartate) receptor-mediated conductances on CA1 hippocampal pyramidal cells in short-term excitability changes was studied with the use of a computational model. Model parameters were based on experimental recordings from dendrites and somata and previous hippocampal simulations. Representation of CA1 neurons included NMDA and non-NMDA excitatory dendritic synapses, dendritic and somatic inhibition, five intrinsic membrane conductances, and provision for activity-dependent intracellular and extracellular ion concentration changes. 2. The model simulated somatic and dendritic potentials recorded experimentally. The characteristic CA1 spike afterdepolarization was a consequence of the longitudinal spread of dendritic charge, reactivation of slow Ca(2+)-dependent K+ conductances, slow synaptic processes (NMDA-dependent depolarizing and gamma-aminobutyric acid-mediated hyperpolarizing currents) and was sensitive to extracellular po...

This study was carried out at PT Len Industri with the intention of examining the impact of corporate social responsibility (CSR) capital on MSME business development of Assisted Partners Pt. Len Industri (Persero) Bandung City, which is documented at the company PT Len Industri. In this study, a sample size of 37 Assisted MSEs was used to represent the population of 200 MSE Assisted Partners of PT Len Industri. A Likert scale is employed in the methodology, which is quantitative. In order to assess the validity of a study's findings and its reliability on the problems being examined, the data gathering approach employs samples from businesses that apply the Slovin formula. As evidenced by the (t) test study findings, the capital program The CSR Unit's work, which is largely carried out by PT Len Industri, has a substantial impact on the business growth of supported MSEs. by providing more capital help to MSME. The Social and Environmental Responsibility MSME Program gives priority to MSMEs that are still small but have the potential to grow. These MSMEs are developed through training and knowledge provision so that those who receive capital can use it properly and productively.

In the fields, it is commonly observed that fenugreek plants are not growing to their maturity in the vicinity of TrianthemaportlacastrumL. In this context, the present study was conducted in the laboratory to observe allelopathic interaction between Trianthemaand fenugreek. Aqueous extracts of seed, stem and leaf of Trianthemawere made. Treatment of these aqueous extracts was given to fenugreek seeds. Germination study was performed by using Petri plates. All the experiments were performed in triplicates. Pre-treatment of aqueous extracts of seed, stem and leaf of Trianthema. had caused a decline in germination percentage, fresh weight, radical and coleoptile length of fenugreek seeds when compared to untreated seeds. At the same time, mean germination time was found to be more in pre-treated seeds compared to control seeds. After 24 hrs of treatment, the enzymatic study was performed. Enzymes from antioxidant metabolism such as peroxidase, ascorbate peroxidase, superoxide dismutas...

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

In this study, we used proteomics in conjunction with microscopy to study differences in the proteome and hyphal morphology of the copper tolerant soft rot fungus Phialophora malorum grown in media containing 0.064, 0.64% Cu as CuSO 4 . Unique proteins were found in the control and the copper-treated (0.064% CuSO 4 ) samples. Of five unique proteins found in the 0.064% CuSO 4 treated cultures, ATP synthase subunit alpha is considered to play an important role in copper tolerance as it is involved in the biosynthesis of fatty acids and steroids and may relate to morphological changes associated with hyphal cell walls of the fungus when grown in the presence of copper. ICP-AES analyses showed total mycelial Cu to increase with media Cu with 5246-and 16535 μg Cu/g dry wt mycelia respectively found in 0.064 and 0.64% Cu-cultures after 6 weeks growth. Rubeanic acid staining of 0.064% mycelia showed Cu bound in intracellular bodies while most Cu was found as extracellular precipitates on the surfaces of hyphae in 0.64% Cu. SEM showed hyphal surfaces enrobed in fibrillar polysaccharides to which Cu was bound.

The effects of microbial pretreatment on hemp fibres were evaluated after microbial retting using the white rot fungi Ceriporiopsis subvermispora and Phlebia radiata Cel 26 and water retting. Based on chemical composition, P. radiata Cel 26 showed the highest selectivity for pectin and lignin degradation and lowest cellulose loss (14%) resulting in the highest cellulose content (78.4%) for the treated hemp fibres. The pectin and lignin removal after treatment with P. radiata Cel 26 were of the order 82% and 50%, respectively. Aligned epoxy-matrix composites were made from hemp fibres defibrated with the microbial retting to evaluate the effects on their ultrastructure. SEM microscopy of the composites showed low porosity on the fibre surfaces after defibration with P. radiata Cel 26 and C. subvermispora indicating good epoxy polymer impregnation. In contrast, fibres treated by water retting and the raw hemp fibres were badly impregnated due to porosity caused by surface impurities s...

Several 238Pu-doped Eu monazite single crystals stored at ambient conditions are monitored for 15 years using Scanning and Transmission electron microscopy, spectroscopy, diffraction and optical microscopy. Despite preservation of high crystalline quality, mechanical cracking and formation of small flakes is observed. After several month of aging, a new phase appeared on surfaces of the crystals, which later formed a continuous shell of most crystallographic faces. Electron diffraction indicated that the shell consists of submicron Pu-containing rhabdophanes. Its formation likely occurs due to combined action of atmospheric moisture and recrystallisation of radiation damage in monazite domains adjacent to external and internal surfaces. Extent of the rhabdophane formation appears to be influenced by crystallography and Pu content of corresponding growth sectors of the parent monazite. Whereas macroscopic rhabdophanes and monazites are relatively stable against irradiation, formation...

In a previous study, our laboratory reported that sildenafil citrate, a cyclic nucleotide phosphodiesterase type 5 inhibitor, reversed a learning impairment in rats induced by systemic inhibition of nitric oxide synthase (60 mg/kg, i.p., N ω -nitro-L-arginine methyl ester; L-NAME). To limit the peripheral effects of L-NAME and further localize the site of action of sildenafil, L-NAME (48 μg, i.c.v.) was infused bilaterally into the lateral cerebral ventricles 30 min prior to maze training. Saline or sildenafil citrate (1.5 or 3.0 mg/kg, i.p.) was administered systemically 15 min before training. Drug injections occurred 24 h after pretraining rats to avoid foot shock on a one-way active avoidance straight runway. Following drug treatment, the rats received 15 training trials on a 14-unit T-maze task that requires learning a complex sequence of turns to avoid mild foot shock. This complex maze paradigm is sensitive to aging and blockade of cholinergic, N-methyl-D-aspartate and nitric oxide signaling systems. Behavioral measures of performance included deviations from the correct pathway (errors), runtime from start to goal (latency), shock frequency and shock duration. Statistical analysis revealed that central infusion of L-NAME impaired maze performance and that sildenafil (3.0 mg/kg) significantly attenuated the impairment. These results suggest that sildenafil citrate may serve as a cognitive enhancer by modulating central nitric oxide/cGMP signal transduction following N-methyl-D-aspartate receptor activation. This pathway has been implicated in age-related cognitive decline and may be a useful target for pharmacological intervention of neurodegenerative disease.

The RAdiative transfer Model Intercomparison (RAMI) activity focuses on the benchmarking of canopy radiative transfer (RT) models. For the current fourth phase of RAMI, six highly realistic virtual plant environments were constructed on the basis of intensive field data collected from (both deciduous and coniferous) forest stands as well as test sites in Europe and South Africa. Twelve RT modelling groups provided simulations of canopy scale (directional and hemispherically integrated) radiative quantities, as well as a series of binary hemispherical photographs acquired from different locations within the virtual canopies. The simulation results showed much greater variance than those recently analysed for the abstract canopy scenarios of RAMI-IV. Canopy complexity is among the most likely drivers behind operator induced errors that gave rise to the discrepancies. Conformity testing was introduced to separate the simulation results into acceptable and non-acceptable contributions. More specifically, a shared risk approach is used to evaluate the compliance of RT model simulations on the basis of reference data generated with the weighted ensemble averaging technique from ISO-13528. However, using concepts from legal metrology, the uncertainty of this reference solution will be shown to prevent a confident assessment of model performance with respect to the selected tolerance intervals. As an alternative, guarded risk decision rules will be presented to account explicitly for the uncertainty associated with the reference and candidate methods. Both guarded acceptance and guarded rejection approaches are used to make confident statements about the acceptance and/or rejection of RT model simulations with respect to the predefined tolerance intervals.

The marine polyarsenical metabolite arsenicin A is the landmark of a series of natural and synthetic molecules characterized by an adamantane-like tetraarsenic cage. Arsenicin A and related polyarsenicals have been evaluated for their antitumor effects in vitro and have been proven more potent than the FDA-approved arsenic trioxide. In this context, we have expanded the chemical space of polyarsenicals related to arsenicin A by synthesizing dialkyl and dimethyl thio-analogs, the latter characterized with the support of simulated NMR spectra. In addition, the new natural arsenicin D, the scarcity of which in the Echinochalina bargibanti extract had previously limited its full structural characterization, has been identified by synthesis. The dialkyl analogs, which present the adamantane-like arsenicin A cage substituted with either two methyl, ethyl, or propyl chains, were efficiently and selectively produced and evaluated for their activity on glioblastoma stem cells (GSCs), a promi...

The vast majority of therapeutic approaches tested so far for prion diseases, transmissible neurodegenerative disorders of human and animals, tackled PrP Sc , the aggregated and infectious isoform of the cellular prion protein (PrP C ), with largely unsuccessful results. Conversely, targeting PrP C expression, stability or cell surface localization are poorly explored strategies. We recently characterized the mode of action of chlorpromazine (CPZ), an anti-psychotic drug known to inhibit prion replication and toxicity by inducing the relocalization of PrP C from the plasma membrane. Unfortunately, CPZ possesses pharmacokinetic properties unsuitable for chronic use in vivo, namely low specificity and high toxicity. Here, we employed HEK293 cells stably expressing EGFP-PrP to carry out a semi-automated high content screening (HCS) of a chemical library directed at identifying non-cytotoxic molecules capable of specifically relocalizing PrP C from the plasma membrane as well as inhibiting prion replication in N2a cell cultures. We identified four candidate hits inducing a significant reduction of cell surface PrP C , one of which also inhibited prion propagation and toxicity in cell cultures in a strain-independent fashion. This study defines a new screening method and novel anti-prion compounds supporting the notion that removing PrP C from the cell surface could represent a viable therapeutic strategy for prion diseases.

The absorption cross-sections at room temperature are reported for the first time, of Br 2 vapor in overlapping bound-free and bound-bound transition of A 3 1u ← X g + , X 1 1u ← X 1 g + and B 3 0u ← X 1 g + , using cavity ring down spectroscopy (CRDS) technique. We reported here, the A 3 1u ← X 1 g + , transition is included along with the two stronger X 1 1u ← X 1 g + and B 3 0u ← X 1 g transitions of Br 2 . We obtained discrete absorption cross-section in the rotational structure, the continuum absorption cross-sections, and were also able to measure the absorption cross-section in separate contribution of A 3 1u ← X 1 g + , 1 1u ← X 1 g + , and B 3 0u ← X 1 g + transitions using CRDS method to use quantum yield of Br * ( 2 P 1/2 ). We obtained absorption cross-section order 10 -19 cm 2 and detection 10 13 molecule cm -3 (1 mTorr) of Br 2 . The absorption cross-sections are increasing with increasing excitation energy in the wavelength region 510-535 nm.

The analytical figure of merit of the potential of laserinduced breakdown spectroscopy (LIBS) has been evaluated for detection of trace element in liquid. LIBS data of Mg, Cr, Mn, and Re were studied. Various optical geometries, which produce the laser spark in and at the liquid sample, were tested. The calibration curves for Mg, Cr, Mn, and Re were obtained at the optimized experimental conditions with bulk liquid and in liquid jet. It was found that measurements using a liquid jet provide better detection limits than bulk liquid measurements. The limits of detection (LOD) of Mg, Cr, Mn, and Re in the present liquid jet measurement are found to be 0.1, 0.4, 0.7, and 8 ppm, respectively. The LOD of Mg using Mg 279.55 nm was compared with the values found in other liquid work.

By using cavity ring-down spectroscopy technique, we have observed the channel leading to Br2 molecular elimination following photodissociation of bromoform at 248 nm. A tunable laser beam, which is crossed perpendicular to the photolysis laser beam in a ring-down cell, is used to probe the Br2 fragment in the B 3Πou+−X 1Σg+ transition using the range 515–524 nm. The ring-down time lasts 500 ns, so the rotational population of the Br2 fragment may not be nascent nature, but its vibrational population should be. The vibrational population ratio of Br2(v=1)/Br2(v=0)=0.8±0.2 implies that the fragmented Br2 is vibrationally hot. The quantum yield of the molecular elimination reaction is 0.23±0.05, consistent with the values of 0.26 and 0.16 reported in 234 and 267 nm photolysis of bromoform, respectively, using velocity ion imaging. A plausible photodissociation pathway is proposed, based upon this work and ab initio calculations. The Ã 1A2, B̃ 1E, and C̃ 1A1 singlet states of bromoform...

Laser induced fluorescence spectroscopy in the ultraviolet (UV-LIF) regime has been used for the detection of bio-chemicals like tyrosine, tryptophan, NADH through a fiber coupled CCD detector. It is observed that the spectrum of the mixture of these bio-chemicals resembles more with that of the tryptophan. The effect of concentration and laser excitation energy on the fluorescence spectra of tryptophan has been investigated. Detection limit with the proposed set-up is found to be one ppm. The study is a part of development of UV-LIF LIDAR system for the standoff detection of biological warfare agents.

The A 3 1u ← X 1 + g photoacoustic spectrum of Br 2 vapor has been studied and vibronic analysis performed using earlier data available for this system of bands from optical spectroscopy in the region 665-720 nm. The vibronic levels involved in these transitions are 4 v 21 and 1 v 4. The relative photoacoustic intensities of the vibronic bands have been used in estimating the non-radiative relaxation rate from vibrational levels of A 3 1u state. The non-radiative relaxation is found to be a nonlinear function of the upper state vibrational quantum number. The radiative rate constants for the A 3 1u state vibrational levels have been compared with the corresponding non-radiative constants obtained from present work. Non-radiative decay rate constants for the vibrational levels of A 3 1u state have been experimentally determined for the first time from photoacoustic spectrum of Br 2 vapor in the extreme red region.

The naturally and widely occurring sulfonium compound, S-adenosylmethionine (AdoMet), one of nature&#39;s most versatile molecules, is biosynthesized from methionine and ATP by AdoMet synthetase or methionine adenosyltransferase (MAT) in a 2-step reaction in which the energy-rich sulfonium compound is formed by dephosphorylation of ATP. All living cells, with the only exception of some parasites and infectious agents, express MAT.

5&#39;-Deoxy-5&#39;-methylthioadenosine phosphorylase from Sulfolobus solfataricus is a hexameric hyperthermophilic protein containing in each subunit two pairs of disulfide bridges, a CXC motif, and one free cysteine. The contribution of each disulfide bridge to the protein conformational stability and flexibility has been assessed by comparing the thermal unfolding and the limited proteolysis of the wild-type enzyme and its variants obtained by site-directed mutagenesis of the seven cysteine residues. All variants were catalyzed efficiently by MTA cleavage with specific activity similar to the wild-type enzyme. The elimination of all cysteine residues caused a substantial decrease of ΔHcal (850kcal/mol) and Tmax (39°C) with respect to the wild-type indicating that all cysteine pairs and especially the CXC motif significantly contribute to the enzyme thermal stability. Disulfide bond Cys200-Cys262 and the CXC motif weakly affected protein flexibility while the elimination of the di...

The neural circuitry underlying movement detection was inferred from studies of amacrine cells under whole-cell patch clamp in retinal slices. Cells were identified by Lucifer yellow staining. Synaptic inputs were driven by "puffing" transmitter substances at the dendrites of presynaptic cells. Spatial sensitivity profiles for amacrine cells were measured by puffing transmitter substances along the lateral spread of their processes. Synaptic pathways were separated and identified with appropriate pre-and postsynaptic pharmacological blocking agents. Two distinct amacrine cell types were found: one with narrow spread of processes that received sustained excitatory synaptic current, the other with very wide spread of processes that received transient excitatory synaptic currents. The transient currents found only in the wide-field amacrine cell were formed presynaptically at GABA B receptors. They could be blocked with baclofen, a GABA B agonist, and their time course was extended by AVA, a GABA B antagonist. Baclofen and AVA had no direct affect upon the wide-field amacrine cell, but picrotoxin blocked a separate, direct GABA input to this cell. The narrow-field amacrine cell was shown to be GABAergic by counterstaining with anti-GABA antiserum after it was filled with Lucifer yellow. Its narrow, spatial profile and sustained synaptic input are properties that closely match those of the GABAergic antagonistic signal that forms transient activity (described above), suggesting that the narrow-field amacrine cell itself is the source of the GABAergic interaction mediating transient activity in the inner plexiform layer (IPL). Other work has shown a GABA B sensitivity at some bipolar terminals, suggesting a population of bipolars as the probable site of interaction mediating transient action. The results suggest that two local populations of amacrine cell types (sustained and transient) interact with the two populations of bipolar cell types (transient forming and nontransient forming). These interactions underlie the formation of the change-detecting subunits. We suggest that local populations of these subunits converge to form the receptive fields of movement-detecting ganglion cells.

The neural circuitry underlying movement detection was inferred from studies of amacrine cells under whole-cell patch clamp in retinal slices. Cells were identified by Lucifer yellow staining. Synaptic inputs were driven by “puffing“ transmitter substances at the dendrites of presynaptic cells. Spatial sensitivity profiles for amacrine cells were measured by puffing transmitter substances along the lateral spread of their processes. Synaptic pathways were separated and identified with appropriate pre- and postsynaptic pharmacological blocking agents.Two distinct amacrine cell types were found: one with narrow spread of processes that sustained excitatory synaptic current, the other with very wide spread of processes that transient excitatory synaptic currents. The transient currents found only in the wide-field amacrine cell were formed presynaptically at GABAB receptors. They could be blocked with baclofen, a GABAB agonist, and their time course was extended by AVA, a GABAB antagon...

The fundamental problem of determining the phase equilibria of binary mixtures is discussed in the context of two-component phospholipid bilayer membranes of saturated phospholipids with different acyl-chain lengths. Results are presented from mean-field calculations and Monte Carlo simulations on a statistical mechanical model in which the interaction between lipid acyl chains of different length is formulated in terms of a hydrophobic mismatch. The model permits a series of binary phase diagrams to be determined in terms of a single ''universal'' interaction parameter. The part of the free energy necessary to derive phase equilibria is determined from the simulations using distribution functions and histogram techniques, and the nature of the phase equilibria is determined by a finite-size scaling analysis which also permits the interfacial tension to be derived. Results are also presented for the enthalpy and the compositional fluctuations. It is shown, in accordance with experiments, that the nonideal mixing of lipid species due to mismatch in the hydrophobic lengths leads to a progressively nonideal mixing behavior as the chain-length difference is increased. Moreover, indications are found that a phase transition in a strict thermodynamic sense may be absent in some of the short-chain one-component lipid bilayers, but a transition can be induced when small amounts of another species are mixed in, leading to a closed phase separation loop with critical points. The physical mechanism of inducing the transition is discussed in terms of the molecular properties of the lipid acyl chains. The results of the numerical model study are expected to have consequences for the interpretation of experimental measurements on lipid bilayer systems in terms of phase diagrams.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

S. lividans TK24 transformed with cosG9B3 6 S. lividans TK24(cosG9B3-P -) S. lividans TK24 transformed with cosG9B3-P - This study S. lividans TK24(cosG9B3-Q -) S. lividans TK24 transformed with cosG9B3-Q - This study S. lividans TK24(cosG9B3-pGilQ) S. lividans TK24-cosG9B3 transformed with pGilQ This study S. lividans TK24(cosG9B3-pGilQGilOIII) S. lividans TK24-cosG9B3 transformed with pGilQGilOIII This study

More and more post-PKS tailoring enzymes are recognized to be multifunctional and codependent on other tailoring enzymes. One of the recently discovered intriguing examples is MtmC, a bifunctional TDP-4-keto-D-olivose ketoreductase-methyltransferase, which -in codependence with glycosyltransferase MtmGIV -is a key contributor to the biosynthesis of the critical trisaccharide chain of the antitumor antibiotic mithramycin (MTM), produced by Streptomyces argillaceus. We report crystal structures of three binary complexes of MtmC with its methylation co-substrate SAM, its co-product SAH, and a nucleotide TDP as well as crystal structures of two ternary complexes, MtmC-SAH-TDP-4-keto-D-olivose and MtmC-SAM-TDP, in the range of 2.2-2.7 Å in resolution. The structures reveal general and sugar-specific recognition and catalytic structural features of MtmC. Depending on the catalytic function that is carried out by MtmC, it must bind either NADPH or SAM in the same co-factor binding pocket. A tyrosine residue (Tyr79) appears as a lid covering the sugar moiety of the substrate during the methyl transfer reaction. This residue swings out of the active site by about 180° in the absence of the substrate. This unique conformational change likely serves to release the methylated product and, possibly, to open up the active site for binding the bulkier co-substrate NADPH prior to the reduction reaction.

In our recent report of structural studies of urdamycins B to Fx), we published partial structures of urdamycins C and D, the two largest molecules amongthe complexof angucycline antibiotics produced by Streptomyces fradiae (strain Tu 2717)2). Nowwe can complete both structures, which are represented by the formulae 1 (urdamycin C) and 2 (urdamycin D).

Colorectal cancer (CRC) is a leading cause of cancer deaths in the United States. Currently, chemotherapy is a first-line treatment for CRC. However, one major drawback of chemotherapy is the emergence of multidrug resistance (MDR). It has been well-established that the overexpression of the ABCB1 and/or ABCG2 transporters can produce MDR in cancer cells. In this study, we report that in vitro, poziotinib can antagonize both ABCB1- and ABCG2-mediated MDR at 0.1–0.6 μM in the human colon cancer cell lines, SW620/Ad300 and S1-M1-80. Mechanistic studies indicated that poziotinib increases the intracellular accumulation of the ABCB1 transporter substrates, paclitaxel and doxorubicin, and the ABCG2 transporter substrates, mitoxantrone and SN-38, by inhibiting their substrate efflux function. Accumulation assay results suggested that poziotinib binds reversibly to the ABCG2 and ABCB1 transporter. Furthermore, western blot experiments indicated that poziotinib, at 0.6 μM, significantly dow...

To have an understanding of potential mechanistic effects, sublethal endpoints able to discriminate between nanomaterials with similar physical and chemical features need to be used. In this sense, quantitative PCR was used to measure a battery of genes linked to a wide array of different cellular processes. Gene expression was measured in Mytilus edulis hemocytes following an in vitro and in vivo exposure to pure silicon (40 nm) and carbon-coated silicon (40 and 75 nm) after 24 h. Partial least squares discriminant analysis and correlation analysis were used to develop an integrative model, describing the relationship between genes, to identify which genes were important in describing responses to engineered nanomaterial exposure. The results suggested that some discriminations could be made based on the presence of a carbon coating or the alteration of size which could inform industrial patterns on ways to reduce the ecotoxicological impact of their product. The results also indicate that HTS on Mytilus hemocytes may be integrated into a safer-by-design approach but additional characterization of nanomaterial behavior in media is required to determine if it is a suitable alternative to in vivo testing.

The expression of the sigB gene of Bacillus subtilis was analysed in response to a mild acid shock. This gene is subject to c fdependent regulation. It has been found that the expression of sigB is induced as part of the acid-tolerant response. In that respect sigB is similar to the previously described gene gsiB which is also a member of the c f regulon. Through this induction, the c f regulon provides protection against acid shock. Besides its protective role against acid shock, no other general function could be directly associated with the c f regulon. An acidification of the cytoplasmic environment induces synthesis of general stress proteins in B. subtilis.

The thermostable hydrogenase from Thiocapsa roseopersicina was examined by low-temperature ESR spectroscopy. Two types of signals were detected, from an oxidized iron-sulphur cluster and a nickel centre (Ni-A). In the oxidized protein additional signals were observed due to spin-spin interaction between the two paramagnetic centres. This interaction could be reversibly abolished by reduction to a redox potential below 105 mV. This implies that an additional redox centre is involved in the interaction, for which an Fe3' ion is suggested. Reduction with hydrogen induced a second type of nickel ESR signal (Ni-C), corresponding to an intermediate redox state seen in other nickel hydrogenases. The Ni-C species was light-sensitive at cryogenic temperatures. At temperatures near to 4.2 K the Ni-C signal showed evidence of interaction with another paramagnetic centre, presumably a second iron-sulphur cluster. On reoxidation a signal due to a third Ni(II1) species, Ni-B, increased in amplitude. These results establish that metal centres in the hydrogenase from T. roseopersicina are closely similar to those of the well-studied hydrogenase from Chromatium vinosum.