Tandem Mass Spectrometry Measurement of the Collision Products of Carbamate Anions Derived from CO2 Capture Sorbents: Paving the Way for Accurate Quantitation

The reaction between CO2 and aqueous amines to produce a charged carbamate product plays a crucial role in post-combustion capture chemistry when primary and secondary amines are used. In this paper, we report the low energy negative-ion CID results for several anionic carbamates derived from primary and secondary amines commonly used as post-combustion capture solvents. The study was performed using the modern equivalent of a triple quadrupole instrument equipped with a T-wave collision cell. Deuterium labeling of 2-aminoethanol (1,1,2,2,-d4-2-aminoethanol) and computations at the M06-2X/6-311++G(d,p) level were used to confirm the identity of the fragmentation products for 2-hydroxyethylcarbamate (derived from 2-aminoethanol), in particular the ions CN−, NCO− and facile neutral losses of CO2 and water; there is precedent for the latter in condensed phase isocyanate chemistry. The fragmentations of 2-hydroxyethylcarbamate were generalized for carbamate anions derived from other capture amines, including ethylenediamine, diethanolamine, and piperazine. We also report unequivocal evidence for the existence of carbamate anions derived from sterically hindered amines (Tris(2-hydroxymethyl)aminomethane and 2-methyl-2-aminopropanol). For the suite of carbamates investigated, diagnostic losses include the decarboxylation product (−CO2, 44 mass units), loss of 46 mass units and the fragments NCO− (m/z 42) and CN− (m/z 26). We also report low energy CID results for the dicarbamate dianion (−O2CNHC2H4NHCO2−) commonly encountered in CO2 capture solution utilizing ethylenediamine. Finally, we demonstrate a promising ion chromatography-MS based procedure for the separation and quantitation of aqueous anionic carbamates, which is based on the reported CID findings. The availability of accurate quantitation methods for ionic CO2 capture products could lead to dynamic operational tuning of CO2 capture-plants and, thus, cost-savings via real-time manipulation of solvent regeneration energies

Expression profiles for six zebrafish genes during gonadal sex differentiation

<p>Abstract</p> <p>Background</p> <p>The mechanism of sex determination in zebrafish is largely unknown and neither sex chromosomes nor a sex-determining gene have been identified. This indicates that sex determination in zebrafish is mediated by genetic signals from autosomal genes. The aim of this study was to determine the precise timing of expression of six genes previously suggested to be associated with sex differentiation in zebrafish. The current study investigates the expression of all six genes in the same individual fish with extensive sampling dates during sex determination and -differentiation.</p> <p>Results</p> <p>In the present study, we have used quantitative real-time PCR to investigate the expression of ar, sox9a, dmrt1, fig alpha, cyp19a1a and cyp19a1b during the expected sex determination and gonadal sex differentiation period. The expression of the genes expected to be high in males (ar, sox9a and dmrt1a) and high in females (fig alpha and cyp19a1a) was segregated in two groups with more than 10 times difference in expression levels. All of the investigated genes showed peaks in expression levels during the time of sex determination and gonadal sex differentiation. Expression of all genes was investigated on cDNA from the same fish allowing comparison of the high and low expressers of genes that are expected to be highest expressed in either males or females. There were 78% high or low expressers of all three "male" genes (ar, sox9a and dmrt1) in the investigated period and 81% were high or low expressers of both "female" genes (fig alpha and cyp19a1a). When comparing all five genes with expected sex related expression 56% show expression expected for either male or female. Furthermore, the expression of all genes was investigated in different tissue of adult male and female zebrafish.</p> <p>Conclusion</p> <p>In zebrafish, the first significant peak in gene expression during the investigated period (2–40 dph) was dmrt1 at 10 dph which indicates involvement of this gene in the early gonadal sex differentiation of males.</p

Simulation of the early stages of thin SiO2 film growth

To gain a better understanding of the silicon oxidation process, we perform numerical simulation of thermal SiO2 thin-film growth. It is shown that the oxidation rate in the early stages of growth is governed by two processes: the rapid initial formation of the oxidation front and its subsequent diffusion. The resulting oxidation rate provides a rather good description of the experimental data with the minimum number of variable parameters, suggesting that the effect of external parameters (such as temperature and pressure) can be explained in terms of scaling concepts. The results of the simulation are also in agreement with the fitting of experimental data to a power law x(ox)=s+at(b) (where x(ox) is the measured SiO2 film thickness and t the oxidation time) predicted by a simple model for thin SiO2 film growth

Influence of the distribution of magnetic moments on the magnetization and magnetoresistance in granular alloys

In granular solids, the magnetoresistance is directly related to the macroscopic magnetization, but this relationship is extremelly complex due to the distribution of grain sizes and the intergranular magnetic interactions. The dependence of the magnetoresistance on the magnetization is here investigated by means of a theoretical. model that is developed taking explicitly into account the magnetic moment distribution and the spin-dependent electron-impurity scattering within magnetic grains and at the interface between the grains and the metallic matrix. Using this model, one can explain large experimental deviations from the parabolic behavior of the magnetoresistance vs magnetization curves that are typically expected for equal noninteracting superparamagnetic grains. The expressions for the magnetization and magnetoresistance, obtained for general distribution functions, are tested considering a log-normal-type distribution function by fitting on data obtained from melt-spun Cu90Co10 ribbons after annealing by de Joule heating. The experimental data are well traced using just three parameters that determine the particle size distribution, the particle density, and the ratio of the scattering cross section at the boundaries of the grains to the scattering cross section within the grains.56106086609

Rearranged limonoids from Khaya senegalensis

The stems of Khaya senegalensis yielded three limonoids which appear to be novel. These compounds were identified on the basis of spectroscopic analysis as methyl 1 alpha,6,8 alpha,14 beta,30 beta-pentahydroxy-3-oxo-[3.3.1(10,2).1(1,4)]-tricyclomeliac-7-oate; methyl 1 alpha,2 beta,3 alpha,6,8 alpha,14 beta-hexahydroxy-[4.2.1(10,30).1(1,4)]-tricyclomeilac-7-oate and methyl 1 alpha-acetoxy-2 beta,3 alpha,6,8 alpha,14 beta-pentahydroxy-[4.21(10,30).1(1.4)]-tricyclomeliac-7-oate. The two latter ones represent a novel group of methyl tricyclomeliac-7-oates. Scopoletin, scoparon, sitosterol, stigmasterol, Campesterol and 3 beta-O-beta-D-glucopyranosylsitosterol were also isolated.42383183

Actin acting at the Golgi

The organization, assembly and remodeling of the actin cytoskeleton provide force and tracks for a variety of (endo)membrane-associated events such as membrane trafficking. This review illustrates in different cellular models how actin and many of its numerous binding and regulatory proteins (actin and co-workers) participate in the structural organization of the Golgi apparatus and in traf- ficking-associated processes such as sorting, biogenesis and motion of Golgi-derived transport carriers

Local hopping mobile DNA implicated in pseudogene formation and reductive evolution in an obligate cyanobacteria-plant symbiosis.

BACKGROUND: Insertion sequences (ISs) are approximately 1 kbp long "jumping" genes found in prokaryotes. ISs encode the protein Transposase, which facilitates the excision and reinsertion of ISs in genomes, making these sequences a type of class I ("cut-and-paste") Mobile Genetic Elements. ISs are proposed to be involved in the reductive evolution of symbiotic prokaryotes. Our previous sequencing of the genome of the cyanobacterium 'Nostoc azollae' 0708, living in a tight perpetual symbiotic association with a plant (the water fern Azolla), revealed the presence of an eroding genome, with a high number of insertion sequences (ISs) together with an unprecedented large proportion of pseudogenes. To investigate the role of ISs in the reductive evolution of 'Nostoc azollae' 0708, and potentially in the formation of pseudogenes, a bioinformatic investigation of the IS identities and positions in 47 cyanobacterial genomes was conducted. To widen the scope, the IS contents were analysed qualitatively and quantitatively in 20 other genomes representing both free-living and symbiotic bacteria. RESULTS: Insertion Sequences were not randomly distributed in the bacterial genomes and were found to transpose short distances from their original location ("local hopping") and pseudogenes were enriched in the vicinity of IS elements. In general, symbiotic organisms showed higher densities of IS elements and pseudogenes than non-symbiotic bacteria. A total of 1108 distinct repeated sequences over 500 bp were identified in the 67 genomes investigated. In the genome of 'Nostoc azollae' 0708, IS elements were apparent at 970 locations (14.3%), with 428 being full-length. Morphologically complex cyanobacteria with large genomes showed higher frequencies of IS elements, irrespective of life style. CONCLUSIONS: The apparent co-location of IS elements and pseudogenes found in prokaryotic genomes implies earlier IS transpositions into genes. As transpositions tend to be local rather than genome wide this likely explains the proximity between IS elements and pseudogenes. These findings suggest that ISs facilitate the reductive evolution in for instance in the symbiotic cyanobacterium 'Nostoc azollae' 0708 and in other obligate prokaryotic symbionts