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At least 19 recordsLinked to original sources
PubMed2002

Efficient destruction of CF4 through in situ generation of alkali metals from heated alkali halide reducing mixtures.

Perfluorocarbons (PFCs) are the most potent green house gases that are very recalcitrant at destruction. An effective way of converting PFCs using hot solid reagents into safe products has been recently introduced. By investigating the thermal reductive destruction of tetrafluoromethane (CF4) we provided new insight and more physicochemical consideration on this novel process. The complete destruction of CF4was successfully achieved by flowing the gas through a heated reagent bed (400-950 degrees C) that contained powder mixtures of alkali halides, CaO, and Si. The silicon acted as a reducing agent of alkali halides for the in-situ production of alkali metals, and the calcium oxide played the role of a halide ion acceptor. The absence of any single component in this ternary mixture drastically reduced the destruction efficiency of CF4. The CF4 destruction efficiencies with the solid reagent containing the alkali halide, MX, increased in the order of Li approximately Na < K < Cs for alkali cations and I < Br < Cl < F for halide anions. This trend agreed with the endothermicity of the alkali metal generation reaction: the higher the endothermicity, the lower the destruction efficiency. Alkali metal generation was indirectly detected by monitoring H2 production from its reaction with water. The production of alkali metals increased with NaF, KF, and CsF in this order. The CsF/CaO/Si system exhibited the complete destruction of CF4 at as low as 600 degrees C. The solid product analysis by X-ray diffraction (XRD) showed the formation of CaF2 and the depletion of Si with black carbon particles formed in the solid reagent residue. No CO/CO2 and toxic HF and SiF4 formation were detected in the exhaust gas.

Air Pollution↗
PubMed1997

Mycobacterium smegmatis phosphoinositols-glyceroarabinomannans. Structure and localization of alkali-labile and alkali-stable phosphoinositides.

Lipoarabinomannans from fast growing Mycobacterium sp., namely AraLAMs, stimulate the early events of macrophage activation. The immunological activities of all of these AraLAMs drastically decrease with the loss of the mild alkali groups, which were believed to be restricted to the fatty acid residues from the phosphatidyl-myo-inositol anchor. This report reveals the presence and the structure of mild alkali-labile phosphoinositide units linked via the phosphate to the C-5 of the beta-D-Araf in the AraLAMs of Mycobacterium smegmatis, a fast growing mycobacterial species. Their structure was unambiguously established with a strategy based on both one-dimensional 31P and two-dimensional 1H-31P heteronuclear multiple quantum correlation spectroscopy (HMQC) and HMQC-homonuclear Hartmann-Hahn spectroscopy NMR experiments applied to native AraLAMs and to AraLAMs treated in mild alkali conditions. Next to these alkali-labile phosphoinositides estimated at three per molecule, two other mild alkali-stable phosphoinositide units were identified: the expected (myo-inositol-1)-phosphate-(3-glycerol) unit typifying the well known glycosylphosphatidylinositol anchor of the mannan core and, more surprisingly, one (myo-inositol-1)-phosphate-(5-beta-D-Araf) unit having the same structure as the alkali-labile ones. Moreover, these four phosphoinositide units were found capping the arabinan side chains. Thus, their different behavior toward mild alkaline hydrolysis was explained according to their accessibility to the alkali reagent. This novel class of LAMs, namely phosphoinositols-glyceroarabinomannans (PI-GAMs), are characterized by their phosphoinositide units but also by the absence of fatty acid residues. These PI-GAMs were found to elicit the secretion of tumor necrosis factor-alpha, suggesting that phosphoinositides are the major PI-GAM epitope involved in this process.

Antigens, Bacterial↗
PubMed2002

Comparative study of lignins isolated by alkali and ultrasound-assisted alkali extractions from wheat straw.

Treatment of the dewaxed wheat straw with 0.5 M KOH at 35 degrees C for 2.5 h without ultrasonic irradiation and with ultrasound assistance for 5, 10, 15, 20, 25, 30, and 35 min resulted in a dissolution of 43.9%, 43.9%, 43.9%, 44.4%, 44.4%, 45.6%, 46.8%, and 49.1% of the original lignin, respectively. Much better results were achieved under the ultrasonic irradiation time for 35 min where nearly 50% of the original lignin was solubilized at 35 degrees C for 2.5 h. The purity of the lignin preparations isolated by alkali with ultrasound assistance was higher than that of the lignin fraction obtained by alkali without ultrasonic irradiation, and their purity increased with an increment of irradiation time between 5 and 35 min, in which the content of associated polysaccharides in the former lignin preparations (0.87-1.06%) was lower than that of the latter lignin fraction (1.16%). In addition, the lignins isolated by alkali with ultrasonic irradiation time between 5 and 30 min showed a slightly higher molecular weight and thermal stability than the lignin obtained by alkali without ultrasound assistance. No substantial differences in the main structure features between the lignin preparations isolated by alkali and ultrasound-assisted alkali extractions were found.

Hydrogen-Ion Concentration↗
PubMed1983

Interaction of alkali light chain 1 with actin: effect of ionic strength on the cross-linking of alkali light chain 1 with actin.

To determine the spatial relationship between alkali light chain and actin in the actosubfragment-1 complex, we studied the cross-linking of actin and subfragment-1 with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. We found that (a) alkali light chain 1 was cross-linked to actin at two sites in the extrapeptide region, and (b) cross-linking of these two sites, especially the one which was very close to the NH2 terminal of the alkali light chain, to actin was inhibited drastically when the KCl concentration was increased from 0 to 100 mM. Since the inhibition of cross-linking with carbodiimide reagent means separation of amino and carboxyl groups in alkali light chain and actin, we suggest that this decrease in electrostatic attraction is the reason why subfragment-1 with alkali light chain 1 has higher affinity to actin than subfragment-1 with alkali light chain 2 at low ionic strength but has almost the same affinity at moderate ionic strength.

Actins↗
PubMed1984

Nephrocalcinosis and diets containing alkali- and non-alkali-treated soy protein.

Diets containing alkali-treated soy protein have been shown to cause nephrocalcinosis in rats. In order to determine if alkali-treated soy protein is the dietary component that induces nephrocalcinosis, the effects of a purified diet containing 20% alpha-protein (an alkali-treated soy protein) were compared with the effects of the same diet containing 20% promine-D (a non-alkali-treated soy protein) on renal morphology and renal calcium and phosphorus metabolism. After a 9-week feeding trial, light and transmission electron microscopy revealed that the animals fed either the alpha-protein or promine-D diet developed nephrocalcinosis. In fact, the type of nephrocalcinosis was the same in both groups of animals. Moreover, quantitative determinations of total renal calcium and phosphorus showed that the severity of nephrocalcinosis was also the same in the two groups. No signs of nephrocalcinosis were detected in rats fed a standard commercial laboratory diet. Since nephrocalcinosis was present in the animals fed the promine-D diet, and that it was identical to that found in the animals fed the alpha-protein diet, it appears that alkali-treated soy protein is not the factor responsible for nephrocalcinosis in rats fed a diet containing the protein.

Alkalies↗
PubMed1984

Drosophila melanogaster has only one myosin alkali light-chain gene which encodes a protein with considerable amino acid sequence homology to chicken myosin alkali light chains.

A chimeric lambda DNA molecule containing the myosin alkali light-chain gene of Drosophila melanogaster was isolated. The encoded amino acid sequence was determined from the nucleic acid sequence of a cDNA homologous to the genomic clone. The identity of the encoded protein was established by two criteria: (i) sequence homology with the chicken alkali light-chain proteins and (ii) comparison of the two-dimensional gel electrophoretic pattern of the peptides synthesized by in vitro translation of hybrid-selected RNA to that of myosin alkali light-chain peptides extracted from Drosophila myofibrils. There is only one myosin alkali light-chain in D. melanogaster; its chromosomal location is region 98B . This gene is abundantly expressed during the development of larval as well as adult muscles. The Drosophila protein appears to contain one putative divalent cation-binding domain (an EF hand) as compared with the three EF hands present in chicken alkali light chains.

Amino Acid Sequence↗
PubMed1980

Effects of pH on frog gustatory responses to chloride salts of alkali-metal and alkali-earth-metal.

The pH effects on frog gustatory responses to alkali-metal and alkali-earth-metal chloride salts were examined using single fungi-form papilla preparations. Responses to 0.1-0.5 M NaCl were clearly dependent upon the pH of the stimulating solutions. The responses increased as the pH decreased from 6.5 to 4.5 and were almost completely suppressed at pH's above 6.5. There was no significant difference in the pH dependency of the response among alkali-metal chlorides. HCl solutions elicited only a poor response under conditions in which the water response was suppressed by the simultaneous presence of a low NaCl concentration. Responses to alkali-earth-metal chlorides varied in their pH dependency. Response to CaCl2 was slightly affected by pH changes from 4.5 to 9.0, response to SrCl2 was considerably suppressed in the alkaline region, and responses to BaCl2 and MgCl2 were strongly suppressed at pH's above 6.5. BeCl2 solutions showed less marked stimulating effects over the pH range tested. The differences in pH dependency described above suggest the existence of two kinds of receptor sites, one being pH-insensitive sites responsible for the calcium response and the other pH-sensitive sites responsible for the sodium response. A cross-adaptation test appeared to support this possibility. Assuming that the pH effect mentioned is related to changes in the state of ionization of the receptor molecule, the pKa of the ionizable group responsible for the sodium response was determined to be approximately 5.5.

Animals↗
PubMed1977

[Socio-medical significance of alkalie resistance, alkalie neutralization and skin-surface lipid content in atopic neurodermatitis and ichthyosis vulgaris (author's transl)].

In individuals free from skin diseases, the resistance and the neutralisation to alkali, and the quantity of lipids at the surface of the skin, are constitltional factors; these idiotypically (genetically) controlled factors are subject to paratypical (environmental) variations. The frequency of a reduced alkali neutralisation and of sebostasis in case of neurodermitis atopica and of ichthyosis vulgaris is not dealt with in the literature, but it results from literature findings that a pathologic alkali resistance is a facultative feature in neurodermitis atopica, while it is an obligatory one in ichthyosis vulgaris. The difference seems to be conditioned genetically. In neurodermitis atopica, the genotype is in itself of no pathogenic importance since the disease is induced exclusively by exogenous and endogenous, non hereditary agents. In ichthyosis vulgaris, the reduced alkali resistance falls into the pleiotropic character of the disease.

Adolescent↗
PubMed2004

"Cooperativity blockage" in the mixed alkali effect as revealed by molecular-dynamics simulations of alkali metasilicate glass.

The relaxation dynamics of a complex interacting system can be drastically changed when mixing with another component having different dynamics. In this work, we elucidate the effect of the less mobile guest ions on the dynamics of the more mobile host ions in mixed alkali glasses by molecular-dynamics (MD) simulations. One MD simulation was carried out on lithium metasilicate glass with the guest ions created by freezing some randomly chosen lithium ions at their initial locations at 700 K. A remarkable slowing down of the dynamics of the majority mobile Li ions was observed both in the self-part of the density-density correlation function, Fs(k,t), and in the mean-squared displacements. On the other hand, there is no significant change in the structure. The motion of the Li ions in the unadulterated Li metasilicate glass is dynamically heterogeneous. In the present work, the fast and slow ions were divided into two groups. The number of fast ions, which shows faster dynamics (Levy flight) facilitated by cooperative jumps, decreases considerably when small amount of Li ions are frozen. Consequently there is a large overall reduction of the mobility of the Li ions. The result is also in accordance with the experimental finding in mixed alkali silicate glasses that the most dramatic reduction of ionic conductivity occurs in the dilute foreign alkali limit. Similar suppression of the cooperative jumps is observed in the MD simulation data of mixed alkali system, LiKSiO3. Naturally, the effect found here is appropriately described as "cooperativity blockage." Slowing down of the motion of Li ions also was observed when a small number of oxygen atoms chosen at random were frozen. The effect is smaller than the case of freezing some the Li ions, but it is not negligible. The cooperativity blockage is also implemented by confining the Li metasilicate glass inside two parallel walls formed by freezing Li ions in the same metasilicate glass. Molecular-dynamics simulations were performed on the dynamics of the Li ions in the confined glass. Slowing down of the dynamics is largest near the wall and decreases monotonically with distance away from the wall.

Journal Article↗
PubMed2000

Effect of alkali metal cationization and multiple alkali metal exchange on the collision-induced dissociation of loganic acid studied by electrospray ionization tandem mass spectrometry

Under electrospray ionization conditions loganic acid undergoes alkali metal (Li, Na and K) exchange and alkali metal cationization. Multiple exchanges of up to four alkali metal ions are observed. Different populations of metal exchanged species are produced during electrospray ionization. Collision-induced dissociation of ammonium cationized species is compared with that of metal cationized species to study the effect of metal cationization. Glycosidic cleavage and ring cleavages of aglycone and sugar moieties are the major fragmentation pathways observed during collision-induced dissociation. The fragmentations of the highly metal exchanged species indicate the opening of the pyran ring. Collision-induced dissociation of the various metal exchanged and metal cationized species also reveals the nature of the different populations. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1983

Preparation of the alkali and P light chains of chicken gizzard myosin. Amino acid sequence of the alkali light chain.

1. A simple method is described for the purification of the alkali and P light chains from chicken gizzard myosin. 2. The sequence of the alkali light chain has been unequivocally determined, except for the N-terminal dipeptide, by using the tryptic and CNBr peptides. 3. No evidence was obtained for any specific high-affinity Ca2+-binding sites on the alkali light chain. 4. Detailed evidence on which the sequence is based has been deposited as Supplementary Publication SUP 50120 (14 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7QB, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1983) 209, 5.

Amino Acid Sequence↗
PubMed2003

Photodesorption of alkali anions from alkali-halide cluster anions.

Using photoelectron spectroscopy, we have observed alkali anion photodesorption from alkali-halide cluster anions that contain two weakly bound electrons. In the alkali iodides, we have found this type of desorption in almost every (MI)(n)M- cluster we have studied (M=Na, K, Cs; n<9), although it depends on the probe laser frequency and cluster temperature. Using pump-probe techniques, we have shown that the process occurs on a picosecond time scale by way of an electronic excitation of the cluster's spin-paired electrons.

Journal Article↗
PubMed2004

The contribution of alkali soluble (humic acid-like) and unhydrolyzed-alkali soluble (core-humic acid-like) fractions extracted from maize plant to the formation of soil humic acid.

Alkali soluble (humic acid-like material) (HA-like) (yield of 132 gkgdm(-1)) and the unhydrolized-alkali soluble (core-humic acid-like material) (core-HA-like) (yield of 33.4 gkgdm(-1)) fractions were extracted from maize plants and characterized by C and N determinations, DRIFT, and 1H and 13C-NMR spectroscopy. Fresh plants were subsequently incubated for 6 months in an artificial mineral soil, and the HA-like and core-HA-like trends were monitored quantitatively (C fraction content) and qualitatively (spectroscopic approach) in order to study their contribution to the formation of soil humic acid. During incubation the HAC-like partially degraded (loss of 320 gkgHAC(-1)) and partially formed new fulvic-like acids (160 gkgHAC(-1)). On the contrary, the stable fraction of HAC, the core-HAC-like, was maintained (loss of 153 kgcore-HAC(-1)), representing, after incubation, 846 gkg(-1) of the initial core-HAC-like content. The core-HA-like fraction is composed of lignin residues, polysaccharides, lipids and proteins, probably structured into a well-defined network, i.e. the plant cell wall.

Alkalies↗
PubMed1982

[Alkali neutralization and alkali resistance in persons with healthy skin and in eczema patients].

Alkali resistance (AR) and alkali neutralisation (AN) time, according to Tronnier and Bussius, were measured at three month intervals on 77 people with healthy skin and compared with test results from 205 patients with occupational dermatitis for whom expert opinion had been given once or several times. It was established that AN and AR react independently of one another. No significant difference was noted in either of the groups with reference to sex, age, occupation and skin type, nor in the ill patients with reference to the duration of the dermatitis, reduction in earning capacity, sensitivity or state of illness at the time opinion was given. Both AN and AR changed usually in the course of occupational dermatitis, however not parallel to one another, nor in relation to the respective skin condition. An and AR results from the dermatitis patients are significantly worse than those from persons with healthy skin tested as comparison. 35% of the healthy persons had pathological AR. In spite of considerable variations in AN in individuals, a satisfactory reproduction of the test results was obtained both for the AN and AR in repeated investigations.

Adult↗
PubMed1980

Studies on acid protease fractions and gastric mucosal atrophy. 1. A modified simple method for separate determination of alkali labile pepsin in gastric juice by alkali treatment or by using a synthetic substrate.

A modified simple method applicable for clinical purpose for separate determination of "pepsin" and "gastricsin" by alkali treatment is reported. The method includes dialysis against 0.1 M acetate buffer, pH 5.3 and incubation in an equal volume of 0.1 M phosphate buffer, pH 7.8 to give a final pH of 7.25, at 25 degrees C for 20 minutes, and has a good reproducibility. N-acetyl-L-phenylalanyl-L-diiodotyrosine (APDT) hyprolysing activity and alkali labile pepsin activity are correlated very well. Nevertheless the former cannot completely be destroyed by the treatment.

Alkalies↗
PubMed1983

Alkali soluble and alkali insoluble fluoride retention in demineralized enamel in vivo.

Demineralization of enamel was induced by applying orthodontic bands in 15 patients having two of their premolars extracted for orthodontic reasons. After a 4-wk caries induction period, eight patients were instructed to rinse their teeth once daily with a neutral 0.05% NaF solution, whereas seven patients received a single treatment with a neutral 2% NaF solution. The bands were reattached to the teeth during the fluoride treatment period and the teeth were extracted after two more weeks. Three consecutive enamel layers were etched off, and a significant uptake of fluoride in all three layers were found in both treatment groups. A larger part of the deposited fluoride was retained in an alkali insoluble form (i.e. fluorapatite) compared with previous studies of sound enamel. It is suggested that the chemical conditions in the cariogenic milieu were favorable for transformation of the fluoride into a stable apatite structure.

Alkalies↗
PubMed1977

[Alkali treatment of proteins. I. Behavior of sulfhydryl and disulfide groups in alkali-treated beta-lactoglobulin and alpha-lactalbumin].

The alkali treatment of beta-lactoglobulin and alpha-lactalbumin results in the splitting of disulphide bonds in the protein molecules. When a 0.8-10(4) M beta-lactoglobulin solution in a 0.022 N sodium hydroxide solution (pH = 12) is heated at 90 degrees C for 30 min, 0-4 M disulphide groups, 2.2 M sulfhydryl groups and 1.8 M sulphide ions/M dimeric beta-lactoglobulin are detectable of the total of 4 M disulphide groups and 2 M sulfhydryl groups/M dimeric beta-lactoglobulin. The sulphide ions can be determined directly in the form of hydrogen sulphide or by calculating the difference between the values from the amperometric-argentometric titration and those from the method of ELLMAN (reaction with DTNB). The disulphide groups are determined with the aid of DTNB after reduction with sodium borohydride. The sulfhydryl groups obtained by reduction with sodium borohydride re-oxidize, the reaction velocity being of the second order. If the disulphide groups are reduced with sodium borohydride, the argentometric-amperometric determination of the sulfhydryl groups by means of the platinum rotating-disk electrode is disturbed by the presence of boric acid.

Chemical Phenomena↗