The proton magnetic resonance study of the structure of Na2Zn(SO4)2·4H2O

The proton magnetic resonance spectra of single crystals of Na2Zn(SO4)2·4H2O have been investigated and the orientations of the water molecules have been determined. Using the heavy atom structure determined by X-rays a system of hydrogen bonds between water and sulphate oxygens has been proposed.

Proton magnetic resonance study of the structure of two tutton's salts

Proton magnetic resonance spectra of single crystals of two Tutton's salts, K2Zn (SO4)2.6H22O and K2Mg (SO4)2.6H2O, have been studied and the orientations of the water molecules in the structure have been determined. Using the heavy-atom structure of (NH4) 2Mgt(SO4)2.6H2O as determined by x-ray diffraction, a system of hydrogen bonds between the water and sulfate oxygens in Tutton's salts has been proposed. It appears that the x-ray structure needs considerable refinement.

Search for new particles decaying into dijets in proton-antiproton collisions at √s=1.96 TeV

We present a search for new particles whose decays produce two jets (dijets) using proton-antiproton collision data corresponding to an integrated luminosity of 1.13 fb-1 collected with the CDF II detector. The measured dijet mass spectrum is found to be consistent with next-to-leading-order perturbative QCD predictions, and no significant evidence of new particles is found. We set upper limits at the 95% confidence level on cross sections times the branching fraction for the production of new particles decaying into dijets with both jets having a rapidity magnitude |y|

Disjunct eddy covariance measurements of volatile organic compound fluxes using proton transfer reaction mass spectrometry

Volatile organic compounds (VOCs) are emitted into the atmosphere from natural and anthropogenic sources, vegetation being the dominant source on a global scale. Some of these reactive compounds are deemed major contributors or inhibitors to aerosol particle formation and growth, thus making VOC measurements essential for current climate change research. This thesis discusses ecosystem scale VOC fluxes measured above a boreal Scots pine dominated forest in southern Finland. The flux measurements were performed using the micrometeorological disjunct eddy covariance (DEC) method combined with proton transfer reaction mass spectrometry (PTR-MS), which is an online technique for measuring VOC concentrations. The measurement, calibration, and calculation procedures developed in this work proved to be well suited to long-term VOC concentration and flux measurements with PTR-MS. A new averaging approach based on running averaged covariance functions improved the determination of the lag time between wind and concentration measurements, which is a common challenge in DEC when measuring fluxes near the detection limit. The ecosystem scale emissions of methanol, acetaldehyde, and acetone were substantial. These three oxygenated VOCs made up about half of the total emissions, with the rest comprised of monoterpenes. Contrary to the traditional assumption that monoterpene emissions from Scots pine originate mainly as evaporation from specialized storage pools, the DEC measurements indicated a significant contribution from de novo biosynthesis to the ecosystem scale monoterpene emissions. This thesis offers practical guidelines for long-term DEC measurements with PTR-MS. In particular, the new averaging approach to the lag time determination seems useful in the automation of DEC flux calculations. Seasonal variation in the monoterpene biosynthesis and the detailed structure of a revised hybrid algorithm, describing both de novo and pool emissions, should be determined in further studies to improve biological realism in the modelling of monoterpene emissions from Scots pine forests. The increasing number of DEC measurements of oxygenated VOCs will probably enable better estimates of the role of these compounds in plant physiology and tropospheric chemistry. Keywords: disjunct eddy covariance, lag time determination, long-term flux measurements, proton transfer reaction mass spectrometry, Scots pine forests, volatile organic compounds

Studies in sesquiterpenes-XVIII. The proton magnetic resonance spectra of some sesquiterpenes and the structure of humulene

The nuclear magnetic resonance spectra of longifolene, zerumbone, humulene, and their hydroderivatives have been studied in order to gauge the potentialities of this new tool in the field of sesquiterpenes. On the basis of present study, it has been possible to unequivocally fix the positions of the ethylene linkages in humulene and thus provide a straightforward solution of this hitherto unsolved problem.

Mycobacterium tuberculosis nucleoid-associated DNA-binding protein H-NS binds with high-affinity to the Holliday junction and inhibits strand exchange promoted by RecA protein

A number of studies have shown that the structure and composition of bacterial nucleoid influences many a processes related to DNA metabolism. The nucleoid-associated proteins modulate not only the DNA conformation but also regulate the DNA metabolic processes such as replication, recombination, repair and transcription. Understanding of how these processes occur in the context of Mycobacterium tuberculosis nucleoid is of considerable medical importance because the nucleoid structure may be constantly remodeled in response to environmental signals and/or growth conditions. Many studies have concluded that Escherichia coli H-NS binds to DNA in a sequence-independent manner, with a preference for A-/T-rich tracts in curved DNA; however, recent studies have identified the existence of medium- and low-affinity binding sites in the vicinity of the curved DNA. Here, we show that the M. tuberculosis H-NS protein binds in a more structure-specific manner to DNA replication and repair intermediates, but displays lower affinity for double-stranded DNA with relatively higher GC content. Notably, M. tuberculosis H-NS was able to bind Holliday junction (HJ), the central recombination intermediate, with substantially higher affinity and inhibited the three-strand exchange promoted by its cognate RecA. Likewise, E. coli H-NS was able to bind the HJ and suppress DNA strand exchange promoted by E. coli RecA, although much less efficiently compared to M. tuberculosis H-NS. Our results provide new insights into a previously unrecognized function of H-NS protein, with implications for blocking the genome integration of horizontally transferred genes by homologous and/or homeologous recombination.

Isoscalar axial-vector renormalization constant and polarized proton structure function

The isoscalar axial-vector renormalization constant is reevaluated using the QCD sum-rule method. It is found to be substantially different from the anomaly-free octet axial-vector u¯γμγ5+d¯γμγ5-2s¯γμγ5 coupling. Combining this determination with the known values of the isovector coupling GA and the F/D ratio for the octet current, we find the integral of the polarized proton structure function to be Gp=Fgp1(x)dx=0.135, in agreement with recent measurement by the European Muon Collaboration.

Proton NMR investigations of ferroelectricity in ammonium sulphate

Results of cw wide-line proton magnetic resonance investigations on ammonium sulphate and rubidium ammonium sulphate are presented. The pressure and temperature dependence of some of the properties of ammonium sulphate are explained stressing the importance of the role of the ammonium ions.

Proton-bifurcated C-H center dot center dot center dot(O,O) hydrogen bonds in 2,3-dichloro-6-nitrobenzylaminium chloride

In the crystal structure of the title salt, C7H7Cl2N2O2+ center dot Cl-, the chloride anions participate in extensive hydrogen bonding with the aminium cations and indirectly link the molecules through multiple N+-H center dot center dot center dot Cl- salt bridges. There are two independent molecules in the asymmetric unit, related by a pseudo-inversion center. The direct intermolecular coupling is established by C-H center dot center dot center dot O, C-H center dot center dot center dot Cl and C-Cl center dot center dot center dot Cl- interactions. A rare three-center (donor bifurcated) C-H center dot center dot center dot (O,O) hydrogen bond is observed between the methylene and nitro groups, with a side-on intramolecular component of closed-ring type and a head-on intermolecular component.

Affinity purification and characterization of 2,4-dichlorophenol hydroxylase from Pseudomonas cepacia

2,4-Dichlorophenol hydroxylase, a flavoprotein monooxygenase from Pseudomonas cepacia grown on 2,4-dichlorophenoxyacetic acid (2,4-D) as the sole source of carbon, was purified to homogeneity by a single-step affinity chromatography on 2,4-DCP-Sepharose CL-4B. The enzyme was eluted from the affinity matrix with the substrate 2,4-dichlorophenol. The enzyme has a molecular weight of 275,000 consisting of four identical subunits of molecular weight 69,000 and requires exogenous addition of FAD for its complete catalytic activity. The enzyme required an external electron donor NADPH for hydroxylation of 2,4-dichlorophenol to 3,5-dicholorocatechol. NADPH was preferred over NADH. The enzyme had Km value of 14 μImage for 2,4-dichlorophenol, and 100 μImage for NADPH. The enzyme activity was significantly inhibited by heavy metal ions like Hg2+ and Zn2+ and showed marked inhibition with thiol reagents. Trichlorophenols inhibited the enzyme competitively. The hydroxylase activity decreased as a function of increasing concentrations of Cibacron blue and Procion red dyes. The apoenzyme prepared showed complete loss of FAD when monitored spectrophotometrically and had no enzymatic activity. The inactive apoenzyme was reconstituted with exogenous FAD which completely restored the enzyme activity.