Exchangeable Hydrogen Research Articles

Depth-wise core sediment profile of tissue free and organic bound tritium in dynamic marine environment

Down core variation of tissue free and organic bound tritium in sediment cores was evaluated to assess the retention of tritium (H-3) by bottom sediment in the dynamic marine environment of Mumbai Harbour Bay. Tissue free water tritium (TFWT) was evaluated by extraction of H-3 from the sediment by extracting it in tritium free water whereas total H-3 by alkaline digestion of core sediment sample. OBT in various core fractions was evaluated by measuring the difference between total H-3 content and TFWT. Total H-3 content in the sediment core varies in the range of 0.41–8.01 Bq g−1 whereas OBT varies between 0.1 and 0.86 Bq g−1. Experimental results clearly indicate that total H-3 content in various fractions of the core sediment samples is dependent on the availability of exchangeable hydrogen which were either associated with clay minerals or organic molecule.

Revisiting the bilayer structures of fluid phase phosphatidylglycerol lipids: Accounting for exchangeable hydrogens

We recently published two papers detailing the structures of fluid phase phosphatidylglycerol (PG) lipid bilayers (Kučerka et al., 2012 J. Phys. Chem. B 116: 232–239; Pan et al., 2012 Biochim. Biophys. Acta Biomembr. 1818: 2135–2148), which were determined using the scattering density profile model. This hybrid experimental/computational technique utilizes molecular dynamics simulations to parse a lipid bilayer into components whose volume probabilities follow simple analytical functional forms. Given the appropriate scattering densities, these volume probabilities are then translated into neutron scattering length density (NSLD) and electron density (ED) profiles, which are used to jointly refine experimentally obtained small angle neutron and X-ray scattering data. However, accurate NSLD and ED profiles can only be obtained if the bilayer's chemical composition is known. Specifically, in the case of neutron scattering, the lipid's exchangeable hydrogens with aqueous D2O must be accounted for, as they can have a measureable effect on the resultant lipid bilayer structures. This was not done in our above-mentioned papers. Here we report on the molecular structures of PG lipid bilayers by appropriately taking into account the exchangeable hydrogens. Analysis indicates that the temperature-averaged PG lipid areas decrease by 1.5 to 3.8Å2, depending on the lipid's acyl chain length and unsaturation, compared to PG areas when hydrogen exchange was not taken into account.

The Influence of Long-Term Fertilization on Soil Acidification

Based on the long-term experimental field of Jilin Agricultural University as a platform. Aiming at groping for the influence of long-term fertilized of the acidity changes on soil in research area. The results show that: compared with CK group. The soil pH declined as a result of applying nitrogenous fertilizer chronically. Instead the content of exchangeable acid, exchangeable hydrogen and exchangeable aluminum increased. The content of soil organic matters reduced with the decrease of soil pH application of phosphate fertilizer and potassium fertilizer could achieve the same objective. But the Influence was not as significant as the one fertilized with N.

Effects of Composts from Co-Composting of Tree Pruning Waste, Cow Dung, and Biomass Fly Ash on Soil Acidity Neutralization and Growth of Chinese Cabbage

The objective of this research was to determine the application effects of compost produced from tree pruning waste and cow dung amended with biomass fly ash on soil acidity neutralization and Chinese cabbage growth. The acid soils were mixed with six different composts and fly ash, namely, Run 16: soil+composts produced from tree pruning waste, cow dung amended with fly ash ranged from 0% (control) to 4%, 8%, and 12%; Run 5: soil+control compost+fresh fly ash; and Run 6: soil+fresh fly ash. Thereafter, they were cured and placed in ten replicated diameter pots for growing Chinese cabbage (Brassica chinensis var. parachinensis). The composite samples of soils during curing and planting were taken and analyzed for their pH, exchangeable hydrogen, and aluminum ions. The height and weight of each vegetable were determined. The results showed that both fly ash and compost can neutralize the acid soil and decrease the quantity of exchangeable hydrogen and aluminum ions. The maximum growth of the Chinese cabbage was found in the soil mixed with the compost produced from compost mixes amended with 8% fly ash.

Addition of reagents to the sheath liquid: A novel concept in capillary electrophoresis-mass spectrometry

Conventional coupling of capillary electrophoresis with electrospray ionisation mass spectrometry typically relies on the use of a triaxial sheath-flow liquid interface to facilitate electrical contact and provide a stable electrospray. In this type of analysis, the use of additives in the sheath liquid itself can also be used to improve ionisation of analytes and even facilitate reactions between separation and detection steps (which we broadly term “sheath-flow chemistry”). In the present work, this concept is demonstrated using two types of sheath-flow reactions for CE coupled with quadrupole time-of-flight (Q-TOF) MS detection. Sheath liquid compositions containing deuterated solvents or DPPH (2,2-diphenyl-1-dipicrylhydrazyl) stable free-radicals yield useful additional structural information for separated analytes. Investigations of fundamental physical and chemical characteristics of the sheath liquid coupling show their direct influence on the efficiency and some of the products of the respective reactions. For example, reducing the capillary internal diameter from 75 to 25μm increased the relative abundance of fully deuterated ions detected by 63–65% (5 exchangeable hydrogens) using constant sheath-flow conditions. Addition of 0.05–0.2mM DPPH to the sheath liquid reduced the peak total ion count obtained for typical antioxidant species by 20 to >95% allowing strongly antioxidant species from mixtures to be readily identified and further studied. The presented approach allows a rapid and information-rich analysis to be performed with minimal reagent and sample consumption.

Mass Spectrometry Combinations for Structural Characterization of Sulfated-Steroid Metabolites

Steroid conjugates, which often occur as metabolites, are challenging to characterize. One application is female-mouse urine, where steroid conjugates serve as important ligands for the pheromone-sensing neurons. Although the two with the highest abundance in mouse urine were previously characterized with mass spectrometry (MS) and NMR to be sulfated steroids, many more exist but remain structurally unresolved. Given that their physical and chemical properties are similar, they are likely to have a sulfated steroid ring structure. Because these compounds occur in trace amounts in mouse urine and elsewhere, their characterization by NMR will be difficult. Thus, MS methods become the primary approach for determining structure. Here, we show that a combination of MS tools is effective for determining the structures of sulfated steroids. Using 4-pregnene analogs, we explored high-resolving power MS (HR-MS) to determine chemical formulae; HD exchange MS (HDX-MS) to determine number of active, exchangeable hydrogens (e.g., OH groups); methoxyamine hydrochloride (MOX) derivatization MS, or reactive desorption electrospray ionization with hydroxylamine to determine the number of carbonyl groups; and tandem MS (MS(n)), high-resolution tandem MS (HRMS/MS), and GC-MS to obtain structural details of the steroid ring. From the fragmentation studies, we deduced three major fragmentation rules for this class of sulfated steroids. We also show that a combined MS approach is effective for determining structure of steroid metabolites, with important implications for targeted metabolomics in general and for the study of mouse social communication in particular.

Liquid chromatography/quadrupole time‐of‐flight mass spectrometry in combination with online hydrogen/deuterium exchange technique for structural elucidation of phase I metabolites of iso‐phenylcyclopentylamine in rat bile

MS/MS experiment and accurate mass measurement are powerful tools in metabolite identification. However, sometimes these data do not provide enough information to assign an unambiguous structure to a metabolite. In combination with MS techniques, hydrogen/deuterium (H/D) exchange can provide additional information for structural elucidation by determination of the number of exchangeable hydrogen atoms in a structure. In this study, the principal phase I metabolites of iso-phenylcyclopentylamine in rat bile were identified by high-performance liquid chromatography with electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS). Since N-oxidation may occur because of the existence of the primary amino group in the structure, it was difficult to differentiate the hydroxylated metabolites from N-oxides by ESI-Q-TOF-MS alone. Therefore, online H/D exchange technique was applied to solve this problem. Finally, 25 phase I metabolites were detected and structurally described, in which 11 were confirmed to be N-oxides. This study demonstrated the effectiveness of high-resolution mass spectrometry in combination with an online H/D exchange technique in rapid identification of drug metabolites, especially in discriminating hydroxylated metabolites from N-oxides.

Discrimination of unprocessed cotton on the basis of geographic origin using multi-element stable isotope signatures

Cotton is the most commonly used natural plant product for the manufacture of yarns and textiles. Consumer perception regarding differences in textile quality in relation to geographic provenance of cotton as well as stringent product labelling requirements demand for the supply chain to furnish proof of geographic provenance beyond merely paper-based audit trails. We have applied isotope ratio mass spectrometry to generate multivariate data sets of raw cotton. A two-point equilibration process with water at ambient temperature was used to account for hydrogen exchange between free hydroxyl groups in the cellulose lattice at ambient humidity, prior to hydrogen isotope analysis. The molar fraction of exchangeable hydrogen in cotton at ambient temperature was found to be 0.046, which is in good agreement with the expected exchange fraction of 0.05. Hierarchical cluster analysis of multivariate stable isotope abundance data from 17 US cotton and 15 non-US cotton samples was able to cluster 15 of the 17 US cotton samples in one group. Hierarchical cluster analysis of multivariate stable isotope signatures of raw cotton showed great promise as an analytical tool to differentiate between US and non-US cotton and possibly even to be able to group unprocessed cotton according to geographic origin.

Kinetic and thermodynamic studies of hydrogen storage alloys as negative electrode materials for Ni/MH batteries: a review

This paper reviews the present performances of intermetallic compound families as materials for negative electrodes of rechargeable Ni/MH batteries. The performance of the metal-hydride electrode is determined by both the kinetics of the processes occurring at the metal/solution interface and the rate of hydrogen diffusion within the bulk of the alloy. Thermodynamic and electrochemical properties for each hydride compound family will be reported. The steps of hydrogen absorption/desorption such as charge-transfer and hydrogen diffusion for evaluating the electrochemical properties of hydrogen storage alloys are discussed. Exchange current density (I 0) and hydrogen diffusion coefficient (D H) are the two most important parameters for evaluating the electrochemical properties of metal hydride electrode. The values of the two parameters for a number of hydrogen storage alloys are compared. The relationship between alloy composition and electrochemical properties is noted and evaluated.

Effects of small interfering RNA-mediated hepatic glucagon receptor inhibition on lipid metabolism in db/db mice

Hepatic glucose overproduction is a major characteristic of type 2 diabetes. Because glucagon is a key regulator for glucose homeostasis, antagonizing the glucagon receptor (GCGR) is a possible therapeutic strategy for the treatment of diabetes mellitus. To study the effect of hepatic GCGR inhibition on the regulation of lipid metabolism, we generated siRNA-mediated GCGR knockdown (si-GCGR) in the db/db mouse. The hepatic knockdown of GCGR markedly reduced plasma glucose levels; however, total plasma cholesterol was increased. The detailed lipid analysis showed an increase in the LDL fraction, and no change in VLDL HDL fractions. Further studies showed that the increase in LDL was the result of over-expression of hepatic lipogenic genes and elevated de novo lipid synthesis. Inhibition of hepatic glucagon signaling via siRNA-mediated GCGR knockdown had an effect on both glucose and lipid metabolism in db/db mice.

Smooth muscle relaxation and activation of the large conductance Ca++ – activated K+ (BKCa) channel by novel oestrogens

Oestrogens can interact directly with membrane receptors and channels and can activate vascular BK(Ca) channels. We hypothesized that novel oestrogen derivatives could relax smooth muscle by an extracllular effect on the α and β1 subunits of the BK(Ca) channel, rather than at an intracellular site. We studied the effects of novel oestrogens on the tension of pre-contracted isolated rat aortic rings, and on the electrophysiological properties of HEK 293 cells expressing the hSloα or hSloα+β1 subunits. Two of the derivatives incorporated a quaternary ammonium side-chain making them membrane impermeable. Oestrone, oestrone oxime and Quat DME-oestradiol relaxed pre-contracted rat aorta, but only Quat DME-oestradiol-induced relaxation was iberiotoxin sensitive. However, only potassium currents recorded in HEK 293 cells over-expressing both hSloα and hSloβ1 were activated by oestrone, oestrone oxime and Quat DME-oestradiol. The novel oestrogens were able to relax smooth muscle, but through different mechanisms. In particular, oestrone oxime required the presence of the endothelium to exert much of its effect, whilst Quat DME-oestradiol depended both on NO and BK(Ca) channel activation. The activation of BK(Ca) currents in HEK 293 cells expressing hSloα+β1 by Quat DME-oestradiol is consistent with an extracellular binding site between the two subunits. The binding site resides between the extracellular N terminal of the α subunit and the extracellular loop between TM1 and 2 of the β1 subunit. Membrane-impermeant Quat DME-oestradiol lacks an exchangeable hydrogen on the A ring obviating antioxidant activity.

Electrochemical hydrogen property improved in nano-structured perovskite oxide LaFeO3 for Ni/MH battery

Perovskite oxide LaFeO3, as a novel candidate for the electrode of Ni/MH battery, holds high specific capacity and good cyclical durability at elevated temperatures. However, the poor electrochemical kinetics is a bottleneck for the application of this type of material. By use of nano-structured materials, there are greatly enhanced values of exchange current density I0 and hydrogen diffusion coefficient D, which resulted in an improvement of electrochemical kinetics, a much higher specific capacity and excellent stability during cycling for nano-structured LaFeO3. In theory, there is a significant possibility of further advancing the hydrogen reaction kinetics of perovskite type oxides for Ni/MH battery.

Characterization of stress degradation products of benazepril by using sophisticated hyphenated techniques

Benazepril, an anti-hypertensive drug, was subjected to forced degradation studies. The drug was unstable under hydrolytic conditions, yielding benazeprilat, which is a known major degradation product (DP) and an active metabolite. It also underwent photochemical degradation in acid and neutral pH conditions, resulting in multiple minor DPs. The products were separated on a reversed phase (C18) column in a gradient mode, and subjected to LC–MS and LC–NMR studies. Initially, comprehensive mass fragmentation pathway of the drug was established through support of high resolution mass spectrometric (HR-MS) and multi stage tandem mass spectrometric (MSn) data. The DPs were also subjected to LC–MS/TOF studies to obtain their accurate masses. Along with, on-line H/D exchange data were obtained to ascertain the number of exchangeable hydrogens in each molecule. LC–1H NMR and LC–2DNMR data were additionally acquired in a fraction loop mode. The whole information was successfully employed for the characterization of all the DPs. A complete degradation pathway of the drug was also established.

Influence of maceral composition on geochemical characteristics of immature shale kerogen: Insight from density fraction analysis

Abstract Variations in the relative proportions of individual macerals in shales can significantly influence the geochemical characteristics of bulk organic matter. Density fractions of kerogen from the thermally immature New Albany Shale (Devonian and Mississippian) with contrasting maceral compositions exhibit strong geochemical differences. The parental shale is characterized by a vitrinite reflectance (Ro) of 0.45%, a total organic carbon content of 13 wt.%, and a sulfur content of 6.2 wt.%. Organic matter is dominated by amorphinite and alginite, with vitrinite and inertinite accounting only for 1% by volume. Alginite-dominated density fractions (density ca. 1.0–1.15 g/cm3) contain significantly more aliphatic hydrogen, a stronger carboxyl/carbonyl contribution, and reduced Fourier transform infrared spectroscopy absorbance in the 1000 to 1100 cm− 1 region assigned to ether bonds (C O C), as compared to the amorphinite-dominated density fraction (density ca. 1.2–1.6 g/cm3). Aromaticity generally increases from alginite-dominated to amorphinite-dominated fractions. Density fractions dominated by amorphinite are more deuterium-depleted (δDn values of nonexchangeable hydrogen up to − 105‰) than alginite-rich density fraction (δDn values reach − 90‰). In contrast, changes in relative proportions of alginite and amorphinite in the New Albany Shale do not significantly affect the amount of isotopically exchangeable hydrogen in total hydrogen (i.e., hydrogen exchangeability). Alginite is relatively 13C-enriched, whereas density fractions having a high content of amorphinite are relatively 13C-depleted. Our results suggest that even small bulk geochemical and isotopic differences can gain relevance after deconvolution from maceral-related variability. The masking influence of maceral abundance patterns must be considered when interpreting bulk geochemical data as paleoenvironmental proxies. The findings of this study on shale and Type II kerogen are relevant for all types of kerogens in sediments and rocks.

Structural Characterization of the Voltage-Sensor Domain and Voltage-Gated K+-Channel Proteins Vectorially Oriented within a Single Bilayer Membrane at the Solid/Vapor and Solid/Liquid Interfaces via Neutron Interferometry

The voltage-sensor domain (VSD) is a modular four-helix bundle component that confers voltage sensitivity to voltage-gated cation channels in biological membranes. Despite extensive biophysical studies and the recent availability of X-ray crystal structures for a few voltage-gated potassium (Kv) channels and a voltage-gate sodium (Nav) channel, a complete understanding of the cooperative mechanism of electromechanical coupling, interconverting the closed-to-open states (i.e., nonconducting to cation conducting) remains undetermined. Moreover, the function of these domains is highly dependent on the physical-chemical properties of the surrounding lipid membrane environment. The basis for this work was provided by a recent structural study of the VSD from a prokaryotic Kv-channel vectorially oriented within a single phospholipid (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)) membrane investigated by X-ray interferometry at the solid/moist He (or solid/vapor) and solid/liquid interfaces, thus achieving partial to full hydration, respectively (Gupta et al. Phys. Rev. E2011, 84, 031911-1-15). Here, we utilize neutron interferometry to characterize this system in substantially greater structural detail at the submolecular level, due to its inherent advantages arising from solvent contrast variation coupled with the deuteration of selected submolecular membrane components, especially important for the membrane at the solid/liquid interface. We demonstrate the unique vectorial orientation of the VSD and the retention of its molecular conformation manifest in the asymmetric profile structure of the protein within the profile structure of this single bilayer membrane system. We definitively characterize the asymmetric phospholipid bilayer solvating the lateral surfaces of the VSD protein within the membrane. The profile structures of both the VSD protein and phospholipid bilayer depend upon the hydration state of the membrane. We also determine the distribution of water and exchangeable hydrogen throughout the profile structure of both the VSD itself and the VSD:POPC membrane. These two experimentally determined water and exchangeable hydrogen distribution profiles are in good agreement with molecular dynamics simulations of the VSD protein vectorially oriented within a fully hydrated POPC bilayer membrane, supporting the existence of the VSD's water pore. This approach was extended to the full-length Kv-channel (KvAP) at a solid/liquid interface, providing the separate profile structures of the KvAP protein and the POPC bilayer within the reconstituted KvAP:POPC membrane.

Kinetic studies on the removal of some metal ions from aqueous solution using modified orange mesocarp extract

This study examines the kinetics of the removal of zinc, copper, nickel and cobalt ions from aqueous solutions by Carboxylated-Toluene Di-isocyanate Orange Mesocarp Extract Resin (CTOR) and Sulphonated-Toluene Di-isocyanate Orange Mesocarp Extract Resin (STOR). Results from contact time experiments indicate that the rate of ion exchange was initially rapid and equilibrium was attained within 40 to 45 min. It was found that the uptake of Zn2+, Cu2+, Ni2+ and Co2+ ions by CTOR and STOR is related to the dissociation power of the exchangeable hydrogen and in sequence similar to the ionic radii of the metal ions. The Vermeulen’s particle diffusion model best described the ion exchange process. The fraction attainment of equilibrium (α) values increase with time and reaching constant value at about 40 to 45 min for the resins, indicating the time for saturation of the active sites. The rate constants for CTOR and STOR decreased with increase in temperature from 29 to 70°C. The negative values of the activation energy calculated using the Arrhenius equation showed that low temperatures favoured the exchange process. Key words: Kinetics, orange mesocarp, ion exchange, metal ions, resin, diffusion.

The internal cavities of pike α-parvalbumin probably contain water

The kinetics of hydrogen exchange of pike a-parvalbumin was investigated using the method of infrared spectroscopy (sensitive to the amide hydrogen atoms in the peptide) and radioisotope method (sensitive to all labile hydrogen atoms). Ultraslow exchangeable hydrogen atoms were found to be substantially less in the first case than in the second one. Taking into account that the internal cavities in the parvalbumin are formed by hydrophobic amino acid residues, devoid of labile hydrogen atoms, it is possible to make the most appropriate assumption, namely, these cavities contain water molecules, hydrogen atoms of which are ultraslow exchangeable.

Large glucosylthioureidocalixarenes: selective hosts for mono- and bisphosphonates

Non-covalent complexation of mono- and bisphosphonates by hexaglucosylthioureidocalix[6]arene and octaglucosylthioureidocalix[8]arene was studied by electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry. Glucosylthioureidocalix[8]arene formed 1:1 and 1:2 complexes with bisphosphonates, with a marked preference towards risedronate, clodronate, zoledronate and etidronate. In contrast, up to four guest molecules were bound in the case of monophosphonates, suggesting a different type of binding in comparison to bisphosphonates. Hexaglucosylthioureidocalix[6]arene also formed complexes with phosphonates with a somewhat similar binding selectivity. Interestingly, the addition of calcium ions into the sample of etidronate–glucosylthioureidocalix[8]arene complex resulted in a complete release of the guest due to the very high affinity between calcium and bisphosphonate. In the gas-phase hydrogen/deuterium exchange reactions, glucosylthioureidocalix[8]arene exhibited a number of exchangeable hydrogens and a bimodal exchange distribution was observed, suggesting a presence of multiple gas-phase conformations. Surprisingly, no exchange or very slow exchange for the complexes of glucosylthioureidocalix[8]arene was observed.

A sensing medium exchangeable hydrogen sensor using Lamb waves

A new type of hydrogen sensor using Lamb waves is proposed and fabricated. The sensor consists of an aluminum thin plate-based hydrogen sensing medium that can be easily replaced, a medium grip component, and a piezoelectric sensor. In addition to structural uniqueness, the proposed hydrogen sensor provides two wave parameters, peak amplitude and phase shift, to detect changes in hydrogen concentration. The proposed sensor can provide reliable sensitivity, decreased fabrication and operational costs, and significantly increased lifetime because its hydrogen sensing medium can be replaced when it shows low sensitivity.

An inter‐laboratory comparative study into sample preparation for both reproducible and repeatable forensic 2H isotope analysis of human hair by continuous flow isotope ratio mass spectrometry

Stable isotope analysis of organic materials for their hydrogen ((2)H), carbon ((13)C), nitrogen ((15)N) or oxygen ((18)O) isotopic composition using continuous flow isotope ratio mass spectrometry (CF-IRMS) is an increasingly used tool in forensic chemical analysis. (2)H isotopic analysis can present a huge challenge, especially when dealing with exhibits comprising exchangeable hydrogen such as human scalp hair. However, to yield forensic data that are fit for purpose, analysis of the (2)H isotopic composition of the same homogeneous human hair sample by any laboratory worldwide must yield the same isotopic composition within analytical uncertainty. This paper presents longitudinal (2)H isotope data for four human hair samples of different provenance, measured by three different laboratories whose sample preparation was based on a two-stage H exchange equilibration method. Although each laboratory employed varying means to comply with the generic features of the sample preparation protocol such as the (2)H isotopic composition of exchange waters or drying down of samples prior to analysis, within each laboratory the Principle of Identical Treatment (P.I.T.) was applied for each individual experiment. Despite the variation in materials and procedures employed by the three laboratories, repeatable and reproducible 'true' (2)H isotope values (δ(2)H(hair,true)) were determined by each laboratory for each of the four stock samples of human scalp hair. The between-laboratory differences for obtained δ(2)H(hair,true) values ranged from 0.1 to 2.5 ‰. With an overall 95% confidence interval of ±2.8 ‰, these differences were not significantly different, which suggests that the general method of two-stage exchange equilibration carried out at ambient temperature is suitable for accurately and reproducibly determining 'true' δ(2)H-values for hair and other proteins provided that certain key conditions are met.