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PubMed2006

Identification of expressed sequence tags in an alkali grass (Puccinellia tenuiflora) cDNA library.

Alkali grass (Puccinellia tenuiflora), a monocotyledonous halophyte, can serve as a model of salt tolerance in monocotyledon crops. To elucidate the molecular events associated with salt tolerance in alkali grass, we generated a directional cDNA library from leaves treated with the alkali salt, NaHCO3. Large-scale sequencing of the cDNA library identified 2942 ESTs representing 2366 non-redundant transcripts. These have been deposited in the dbEST division of GenBank. BLASTX evaluation indicated that 1274 of the ESTs were homologous to various known genes/proteins in a broad range of organisms, especially gramineae species. The other 1092 ESTs, which showed little if any homology to known sequences, were considered novel. Based on the encoded proteins, the 1274 identified ESTs fell into 12 functional categories, of which four were abundant, namely metabolism (18.84%), transcription (12.48%), unclassified (11.22%) and cell rescue/defense (9.66%). The 162 unique transcripts corresponding to possible salt-related genes were also identified. This study provides an overview of gene expression in NaHCO3-stressed alkali grass, as well as useful information for further investigation of salt resistance in plants.

Cloning, Molecular↗
PubMed2003

Local suppression of IL-1 by receptor antagonist in the rat model of corneal alkali injury.

Proinflammatory cytokines, including interleukin-1 (IL-1) have been implicated in the inflammation that follows corneal alkali injury. The purpose of this series of experiments was to test whether topically applied interleukin-1 receptor antagonist (IL-1ra) could suppress corneal inflammation and promote transparency after alkali injury. Alkali injury was induced on day 0 by application of 1N NaOH to both eyes of Wistar rats (n = 28). Immediately thereafter, eyes received either topical IL-1ra (20 mg ml(-1)) in 0.2% sodium hyaluronate or vehicle alone three times daily during days 0-14. Biomicroscopic features including corneal opacity and neovascularization were assessed using a standard grading scheme. Inflammation was quantified histologically. Corneas excised at day 3 and 7 (randomly selected six eyes in each group per time point studied) were homogenized, and levels of IL-1alpha, IL-1beta, IL-6, IL-8, IL-10, and RANTES were quantified by enzyme-linked immunosorbent assay. Epithelial wound healing was examined by computed analysis of fluorescein stained corneal photographs taken daily until day 14. According to these evaluations, eyes treated with IL-1ra maintained corneal transparency with minimal neovascular invasion. Additionally, corneal damage and cell infiltration were reduced on day 7 (infiltration cells were almost 40% decreased). All cytokine/chemokine levels in IL-1ra treated eyes were significantly lower at day 3, and IL-6 and IL-10 remained significantly lower at day 7 compared to vehicle-treated eyes. IL-1ra treatment retarded epithelial wound healing in the early stage (day 1-4); however, subsequently IL-1ra treated eyes had enhanced healing with full epithelial closure at nearly the same time point as vehicle-treated eyes (day 10). We conclude that local antagonism of IL-1 after alkali injury can significantly decrease corneal inflammation and lead to enhanced corneal transparency.

Animals↗
PubMed1997

Effects of alkali metal cations on the labellar water receptor cell of the fleshfly, Boettcherisca peregrina.

Dose-response relationships of the labellar water receptor cells of the fleshfly, Boettcherisca peregrina, in response to alkali-metal ions were studied electrophysiologically. When cation concentration was raised, the frequency of spikes from the water receptor cells was decreased. We analyzed the data under the assumption that channels on the water receptor membrane open when stimulated with water and are closed by alkali cations or nonelectrolytes. Dose-response relationships of the water receptor for NaCl, KCl and LiCl were analyzed using the Hill equation. The Hill coefficients and the activities of salts eliciting the half maximal response differed considerably among these salts. It is concluded that the effectiveness of salts on the inhibition of the water receptor cell differs among alkali metal ions, and that alkali cations interact cooperatively with the receptor membrane.

Journal Article↗
PubMed1983

On the mode of the alkali light chain association to the heavy chain of myosin subfragment 1. Evidence for the involvement of the carboxyl-terminal region of the heavy chain.

Evidence is presented that the removal of the alkali light chain subunit from myosin subfragment 1 results in the exposure of a site (or sites) at the carboxyl-terminal region of the heavy chain that is rapidly digested by both trypsin and alpha-chymotrypsin. In the case of trypsin digestion, cleavage at this site proceeds at a much higher rate than cleavage at the two other sensitive regions located in the interior of the primary structure of this chain. This initial cleavage is responsible for the generation, on further digestion with trypsin, of a carboxyl-terminal fragment about 3000 daltons smaller than the corresponding fragment formed by digestion of subfragment 1. The ability of the heavy chain to reassociate with alkali light chain at 4 degrees C in the presence of MgATP is essentially abolished by cleavage at this exposed site by either trypsin or chymotrypsin. These observations indicate that the alkali light chain is binding to, or is capable of perturbing, a region of the heavy chain adjacent to the subfragment 1/subfragment 2 "hinge" region and support recent proposals that both the DTNB light chain and the alkali light chain may be interacting and may be modulating this flexible region of the cross bridge.

Actins↗
PubMed2006

Janus scorpionates: supramolecular tectons for the directed assembly of hard-soft alkali metallopolymer chains.

A new scorpionate ligand [HB(mtda)3-] containing mercaptothiadiazolyl (mtda) heterocyclic rings with both hard nitrogen donors and soft sulfur donors has been prepared. This new ligand, the Janus scorpionate, is a hybrid of a tris(pyrazolyl)borate and a tris(mercaptoimidazolyl)borate. The differential hard/soft character of the dissimilar donor groups in this bridging ligand was exploited for the controlled solid-state organization of homometallic and heterometallic alkali metal coordination polymers. Remarkably, in the case of sodium, coordination polymers with both acentric (with NaS3N3H kernels) and centric (with alternating NaN6 and NaS6H2 kernels) chains are found in the same crystal (where the centricity is defined by the relative orientations of the B-H bonds of the ligands along the lattice). For the homometallic potassium congener, the larger cation size, compared to sodium, induced significant distortions and favored a polar arrangement of ligands in the resulting coordination polymer chain. An examination of the solid-state structure of the mixed alkali metal salt system revealed that synergistic binding of smaller sodium cations to the nitrogen portion and of the larger potassium cations to the sulfur portion of the ligand minimizes the ligand distortions relative to the homometallic coordination polymer counterparts, a design feature of the ligand that likely assists in thermodynamically driving the self-assembly of the heterometallic chains. The effect of alkali metal complexation on the solution properties of the ligand was studied by comparing NMR chemical shifts, B-H stretching frequencies, and electrochemical properties with those of the noncoordinating tetrabutylammonium salt of the scorpionate. The similarity of these data regardless of cation indicates that the salts are likely dissociated in solution rather than maintaining their solid-state polymeric structures. This data is augmented by the ESI(+/-) mass spectral data for a series of mixed alkali metal tris(mercaptothiadiazolyl)borates that also indicate that dissociation occurs in solution.

Journal Article↗
PubMed2001

An insight into alkali promotion: a density functional theory study of CO dissociation on K/Rh(111).

The important role of alkali additives in heterogeneous catalysis is, to a large extent, related to the high promotion effect they have on many fundamental reactions. The wide application of alkali additives in industry does not, however, reflect a thorough understanding of the mechanism of their promotional abilities. To investigate the physical origin of the alkali promotion effect, we have studied CO dissociation on clean Rh(111) and K-covered Rh(111) surfaces using density functional theory. By varying the position of potassium atoms relative to a dissociating CO, we have mapped out the importance of different K effects on the CO dissociation reactions. The K-induced changes in the reaction pathways and reaction barriers have been determined; in particular, a large reduction of the CO dissociation barrier has been identified. A thorough analysis of this promotion effect allows us to rationalize both the electronic and the geometrical factors that govern alkali promotion effect: (i) The extent of barrier reductions depends strongly on how close K is to the dissociating CO. (ii) Direct K-O bonding that is in a very short range plays a crucial role in reducing the barrier. (iii) K can have a rather long-range effect on the TS structure, which could reduce slightly the barriers.

Journal Article↗
PubMed2006

Nonlinear optical properties of alkalides Li+(calix[4]pyrrole)M- (M = Li, Na, and K): alkali anion atomic number dependence.

A new type of alkalide compound, Li+(calix[4]pyrrole)M- (M = Li, Na, and K), is presented in theory, which may be stable at room temperature. It has been shown by our calculations that the first hyperpolarizability (beta) is considerably large by means of the density functional theory method. The beta values are determined at the B3LYP/6-311++G level (for the alkali atoms the 6-311++G(3df) basis set is employed) as 8.9 x 103, 1.0 x 104, and 2.4 x 104 au for M = Li, Na, and K, respectively. These beta values are much larger than that of electride Li+(calix[4]pyrrole)e- (beta = 7.3 x 103 au) by a factor of 1.2 to 3.4. Comparing to the cryptand calix[4]pyrrole, the beta values of Li+(calix[4]pyrrole)M- are enhanced by 20-60 times. It is revealed, for the first time, that the beta value of alkalide compounds depends on the atomic number of the alkali anion, and it can be enhanced by choosing the akali anions with larger atomic numbers. The alkali anion in the alkalide compound decreases the transition energy and also increases the oscillator strength of the main transition, consequently the beta value is enhanced. This study proposes such a novel way to synthesize and design new NLO materials by using the alkali atom with a larger atomic number to create an anion in alkalide compounds.

Journal Article↗
PubMed2000

Preparation and dynamic viscoelasticity characterization of alkali-solubilized collagen from shark skin.

Alkali-solubilized collagens, prepared by alkali-acid extraction and alkali direct extraction (abbreviated AASC and ALSC, respectively), were characterized by dynamic viscoelastic measurement of collagen solution (10 mg/mL). The optimum preparative conditions in terms of yield and polypeptide size are as follows: for the alkali-acid extraction, a pretreatment with 0.5 or 1 M NaOH containing 15% Na(2)SO(4) within 5 days at 20 degrees C followed by the subsequent acid extraction, and for the alkaline direct extraction, a treatment with 0.5 M NaOH containing 10% NaCl at 4 degrees C for 20-30 days. A major portion of the polypeptide sizes of AASC and ALSC is composed of alpha chains (alpha1 and alpha2). Dynamic viscoelasticity of collagen solution was measured as a function of temperature. AASC showed a greater contribution of elastic behavior rather than viscous behavior. On the contrary, ALSC exhibits a stronger viscous behavior than elastic behavior.

Animals↗
PubMed2005

Why h atom prefers the on-top site and alkali metals favor the middle hollow site on the Basal plane of graphite.

In this work, the different adsorption properties of H and alkali metal atoms on the basal plane of graphite are studied and compared using a density functional method on the same model chemistry level. The results show that H prefers the "on-top site" while alkali metals favor the "middle hollow site" of graphite basal plane due to the unique electronic structures of H, alkali metals, and graphite. H has a higher electronegativity than carbon, preferring to form a covalent bond with C atoms, whereas alkaline metals have lower electronegativity, tending to adsorb on the highest electrostatic potential sites. During adsorption, there are more charges transferred from alkali metal to graphite than from H to graphite.

Journal Article↗
PubMed2006

The electronic structure of alkali aurides. A four-component Dirac-Kohn-Sham study.

Spectroscopic constants, including dissociation energies, harmonic and anharmonic vibrational frequencies, and dipole moments, are calculated for the complete alkali auride series (LiAu, NaAu, KAu, RbAu, CsAu). The four-component formulation of relativistic density functional theory has been employed in this study, using the G-spinor basis sets implemented recently in the program BERTHA. The performance of four standard nonrelativistic density functionals employed is investigated by comparing the results with the best available theoretical and experimental data. The present work provides the first theoretical predictions on the molecular properties of RbAu. The intermetallic bond that occurs in the alkali auride series is highly polar and is characterized by a large charge transfer from the alkali metals to gold. The extent of this electron transfer has been investigated using several different charge analysis methods, enabling us to reach some general conclusions on their relative performance. We further report a detailed analysis of the topological properties of relativistic electron density in the bonding region, discussing the features of this approach which characterize the nature of the chemical bond. We have also computed the fully relativistic density for the alkali halides MBr and MI (M = Li, Na, K, Rb, and Cs). The comparative study shows that, on the basis of several topological properties and the variation in bond lengths, the gold atom behaves similarly to a halogen intermediate between Br and I.

Journal Article↗
PubMed2001

The influence of fuel additives on the behaviour of gaseous alkali-metal compounds during pulverised coal combustion.

The alkali-metal vapour release during pulverised hard (bituminous) coal combustion was investigated in a semi-technical drop flow reactor in the temperature range 1100-1400 degrees C. Absolute concentrations of total gas-phase sodium and potassium species were determined using the in situ/on-line excimer laser induced fragmentation fluorescence technique (ELIF). Alkali-metal concentrations measured for the untreated coals were found to be in the range 0.1 to 4.7 ppm, depending on the temperature. As well as observing the temperature dependence, the effect of co-feeding defined amounts of silica and clay minerals was studied. In addition, to assist interpretation of ELIF measurements, ash samples were taken and analysed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The additives lead to a pronounced binding of the alkali-metal species and suppression of the sharp temperature dependence observed without co-feeding. Therefore, the use of such getter materials can be confirmed as an effective way to remove corrosive alkali-metal species from the flue gas in pulverised coal combustion.

Journal Article↗
PubMed1998

The role of regulatory gene products in alkali sensitization by extracellular medium components in Escherichia coli.

Organisms of Escherichia coli 1829 become alkali sensitized on transfer from pH 7.0 to pH 5.5 but they also secrete extracellular agents which induce alkali sensitivity when added (in neutralized filtrates) to organisms growing at pH 7.0. In contrast, filtrates from cultures grown at pH 7.0 have no effect. Filtrates were inactivated by protease but not by heat treatment in a boiling water-bath, suggesting that a very heat-stable protein is involved in alkali sensitivity induction. A heat-stable low molecular weight component (or components) may also be needed for induction, or the induction protein itself may be of low molecular weight. Strains with lesions in hns, fur or himA produced almost inactive filtrates and it therefore appears that H-NS, Fur and IHF are involved in synthesis of the induction components. As the presence of protease during incubation at pH 5.5 totally abolished alkali sensitization of strain 1829 while inhibition of sensitization induction occurred if the induction components were removed by filtration or dialysis during pH 5.5 incubation, it is proposed that the extracellular induction components (EICs) are essential for the original sensitization response. These results suggest that sensitization induction occurs by a different mechanism to that which is believed to occur for most bacterial inducible response systems; these are claimed to involve exclusively intracellular reactions and components whereas the present response involves functioning of extracellular components.

Bacterial Proteins↗
PubMed2004

Ion dynamics in mixed alkali cadmium fluoride glasses.

We have investigated ion dynamics in cadmium fluoride nonoxide glasses, in the frequency range from 10 Hz to 2 MHz and in the temperature range from room temperature to just below the glass transition temperature. We have established the existence of mixed alkali effect for these glasses from different aspects of relaxation dynamics. We have observed lower dimensionality of the conduction pathways in mixed alkali cadmium fluoride glasses compared to that in the single alkali glasses. Although, both n and beta represent the interaction between the charge carriers, we have not found any theoretical correlation between them. Using different scaling approaches we have shown that the relaxation dynamics in mixed alkali cadmium fluoride glasses is independent of temperatures.

Journal Article↗
PubMed2006

Dynamic light scattering in mixed alkali metaphosphate glass forming liquids.

We report the first ever photon correlation spectroscopy performed on single alkali and mixed alkali metaphosphate glasses at refractory temperatures above the glass transition. We find not only a significant decrease in the glass transition temperature but also a decrease in fragility for the mixed alkali composition as compared with the single akali glasses. We argue that structural relaxation in these polymeric oxide glasses is largely controlled by the cross linking cations and that the changes in fragility that we observed are a reflection of changes in the cooperativity of structural relaxation wrought by the substantial decrease in the ion mobility that accompanies the mixing of alkali ions.

Journal Article↗
PubMed2000

Synthetic receptors as models for alkali metal cation-pi binding sites in proteins.

The alkali metal cations Na(+) and K(+) have several important physiological roles, including modulating enzyme activity. Recent work has suggested that alkali metal cations may be coordinated by pi systems, such as the aromatic amino acid side chains. The ability of K(+) to interact with an aromatic ring has been assessed by preparing a family of synthetic receptors that incorporate the aromatic side chains of phenylalanine, tyrosine, and tryptophan. These receptors are constructed around a diaza-18-crown-6 scaffold, which serves as the primary binding site for an alkali metal cation. The ability of the aromatic rings to coordinate a cation was determined by crystallizing each of the receptors in the presence of K(+) and by solving the solid state structures. In all cases, complexation of K(+) by the pi system was observed. When possible, the structures of the unbound receptors also were determined for comparison. Further proof that the aromatic ring makes an energetically favorable interaction with the cation was obtained by preparing a receptor in which the arene was perfluorinated. Fluorination of the arene reverses the electrostatics, but the aromaticity is maintained. The fluorinated arene rings do not coordinate the cation in the solid state structure of the K(+) complex. Thus, the results of the predicted electrostatic reversal were confirmed. Finally, the biological implications of the alkali metal cation-pi interaction are addressed.

Binding Sites↗
PubMed1999

Size and charge requirements for kinetic modulation and actin binding by alkali 1-type myosin essential light chains.

The alkali 1-type isoforms of myosin essential light chains from vertebrate striated muscles have an additional 40 or so amino acids at their N terminus compared with the alkali 2-type. Consequently two light chain isoenzymes of myosin subfragment-1 can be isolated. Using synthesized peptide mimics of the N-terminal region of alkali 1-type essential light chains, we have found by 1H NMR that the major actin binding region occurred in the N-terminal four residues, APKK. These results were confirmed by mutating this region of the human atrial essential light chain, resulting in altered actin-activated MgATPase kinetics when the recombinant light chains were hybridized into rabbit skeletal subfragment 1. Substitution of either Lys3 or Lys4 with Ala resulted in increased Km and kcat and decreased actin binding (as judged by chemical cross-linking). Replacement of Lys4 with Asp reduced actin binding and increased Km and kcat still further. Alteration of Ala1 to Val did not alter the kinetic parameters of the hybrid subfragment 1 or the essential light chain's ability to bind actin. Furthermore, we found a significant correlation between the apparent Km for actin and the kcat for MgATP turnover for each mutant hybrid, strengthening our belief that the binding of actin by alkali 1-type essential light chains results directly in modulation of the myosin motor.

Actins↗
PubMed1976

Effects of alkali-treated proteins: feeding studies with free and protein-bound lysinoalanine in rats and other animals.

To find out whether alkali-treated proteins posses nephrotoxic properties, feeding studies were conducted with drastically treated soybean protein and casein, and also with lysinoalanine (LAL), the amino acid known to be formed in protein subjected to high pH at elevated temperature. The feeding of synthesized LAL to rats at dietary levels of 100 ppm and above induced typical renal changes, called nephrocytomegalia. No such changes or any other indications of toxicity were observed, however, upon feeding much higher levels of LAL (up to 6,000 ppm) when provided as the protein-bound compound in alkali-treated casein or soybean protein. When set free by complete acid hydrolysis, LAL induced considerable renal activity, comparable to that of the synthetic compound. These results indicate that alkali treatment of proteins does not induce nephrotoxic properties provided that the compound remains protein-bound. Some nephrotoxic activity was observed, however, with peptide-boound LAL in break-down products (molecular weight less than 5,000) of alkali-treated casein, but considerably less than that of the free compound. LAL-analyses in blood, urine, and feces of rats fed free or protein-bound LAL indicated a positive correlation between intestinal absorption and nephrotoxic potential. No renal changes were encountered upon feeding diets with 1,000 ppm synthetic LAL to mice, hamsters, rabbits, quail, dogs or monkeys, which suggest a species specificity of LAL-induced renal changes in rats.

Animals↗
PubMed1977

Molecular architecture of cytochrome oxidase and its transition on treatment with alkali or sodium dodecyl sulfate.

In dimeric cytochrome oxidase [EC 1.9.3.1], one of the two heme a molecules of one monomeric unit has been proposed to be converted by the other unit, thus becoming latent in terms of catalytic functions (1). As the dimer was split into two monomers by treatment with alkali or sodium dodecyl sulfate (SDS), it was shown that the intensity of circular dichroism (CD) in the Soret region due to heme a decreased, probably reflecting release of the strain on the latent heme. On the other hand, the profile of magnetic circular dichroism (MCD) was nearly unchanged during this conversion, except for a weakening of the signal due to deprotonation of the heme during the alkali treatment. When the monomer was further dissociated into constituent subunits in strong alkali or at high concentrations of SDS, the CD spectrum disappeared almost completely, indicating loss of the asymmetric interactions of the chromophoric heme a with its immediate environments, consisting of the subunit assembly. The MCD pattern also suffered a small change as the dissociation proceeded, and a specific pattern appeared as the Schiff base was finally formed. The Schiff base formation of cytochrome oxidase in strong alkali proceeded in two steps whether the heme iron was in the oxidized or reduced state. As a consequence of the initial rapid reaction, the enzyme was suggested to have been disintegrated into constituent subunits with heme a being attached nonspecifically to either one, and structural characteristics dependent on the redox state were completely lost. The Arrehenius plot for this rapid change showed a break, indicating a transition in the structure of the cytochrome oxidase assembly, although no such phenomenon was observed during the slow reaction. Activation parameters in the rapid and slow reactions for the oxidized and reduced oxidase are given. Based on these findings, as well as other considerations, a molecular architecture of this enzyme is proposed; the role of heme a in anchoring four 14,000-dalton polypeptides into the minimal functional unit catalyzing the aerobic oxidation of ferrocytochrome c is emphasized.

Circular Dichroism↗