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PubMed1981

Medroxyprogesterone on corneal ulceration. Its effects after alkali burns on rabbits.

The effect of medroxyprogesterone acetate treatment in preventing or retarding corneal ulceration after alkali burns was studied in rabbits in an attempt to correlate dose and response. The eyes were treated for 21 days with a 0.01% or 1% suspension administered topically four times a day or medroxyprogesterone acetate, 4 mg or 30 mg, given subconjunctivally on alternate days. None of these regimens was noticeably effective, although at times there was a trend toward retarding ulceration. Thus, it was not possible to confirm earlier reports of substantial efficacy of medroxyprogesterone. Corneal stroma with epithelial defects and/or ulcers persistently showed infiltration with neutrophils in the superficial stroma within the epithelial defect, implicating the tears as the source of the inflammatory cells.

Alkalies↗
PubMed1987

Systemic tetracycline treatment of alkali-induced corneal ulceration in rabbits.

Recent evidence has demonstrated a marked anticollagenolytic effect for the tetracycline antibiotics. We have examined the efficacy of systemic tetracycline hydrochloride in a rabbit model of corneal ulceration. A standard alkali burn (1N sodium hydroxide for 40 s) was delivered to 62 eyes (31 rabbits). Animals were then divided into three groups: group 1 (controls) (ten rabbits [20 eyes]) received no treatment; group 2 (ten rabbits [20 eyes]) received 10 mg/kg/d of tetracycline hydrochloride, given intramuscularly; and group 3 (11 rabbits [22 eyes]) received 50 mg/kg/d. Ulceration occurred in 85% (17/20) of control eyes. The higher dosage of tetracycline was more effective in preventing ulceration than the lower dosage (9.1% vs 55%). Eyes with higher levels of tetracycline in ocular tissues were less likely to ulcerate.

Alkalies↗
PubMed2000

Matrix effects on selectivities of poly(ethylene glycol)s for alkali metal ion complexation in matrix-assisted laser desorption/ionization.

The effect of the matrix on poly(ethylene glycol) (PEG) cationization was investigated using an equimolar mixture of CsCl and LiCl as cationizing agents. It was observed that for both carboxylic acid and non-carboxylic acid matrices used, PEG cationization by a given alkali metal ion depends on the matrix used. For example, cesiated PEG ion intensities were much stronger than those of the corresponding lithiated PEG ions when equimolar concentrations of Cs(+) and Li(+) were present and IAA (indolacrylic acid) was the matrix. However, an opposite result was obtained when the same experimental conditions were utilized, but with HABA (2-(4-hydroxyphenylazo)benzoic acid) in place of IAA as the matrix.

Acrylates↗
PubMed2000

Mechanism of cross-ring cleavage reactions in dirhamnosyl lipids: effect of the alkali ion.

Liquid secondary ion mass spectrometry and high-energy collision-induced dissociation were used to analyze a dirhamnosyl lipid mixture. The negative fast-atom bombardment spectrum reveals a mixture of four homologous dirhamnosyl lipids with the following general structure: Rha-Rha-Cn-Cm (where Cn and Cm denote 3-hydroxy fatty acid moieties). The mass region 450-600 u in the collision-induced dissociation spectra of the negative [M - H]- ions shows product ions that can be rationalized by terminal loss of a 3-hydroxyalkanoic acid residue; these ions can be used for the characterization of the fatty acid substituents. A unique effect of alkali-metal ions on the course of fragmentation of dirhamnosyl lipid attachment ions was observed. The strong chelation of sodium is revealed from the stability of the [M - H + 2Na]+ ion that does not lose a sodium ion with the eliminated neutrals, contrary to what is observed for the dilithium adduct. Cross-ring cleavages occur during high-energy collision-induced dissociation of both positively and negatively charged precursor ions. The results suggest a concerted decomposition pathway involving the six-membered rings of the monosaccharide residues. The formation of cross-ring cleavage products, which retain the C10-C10 moiety during high-energy collision-induced dissociation of all the precursor ions that contain sodium or lithium, strongly supports a retro [2 + 2 + 2] mechanism.

Alkalies↗
PubMed1999

Manipulation of separation selectivity for alkali metals and ammonium in ion-exchange capillary electrochromatography using a suspension of cation exchange particles in the electrolyte as a pseudostationary phase.

The viability of using ion-exchange particles as a pseudostationary phase in capillary electrochromatography for the separation of monovalent inorganic cations has been investigated. Using sulfonated polymeric particles (average diameter 225 nm) as the pseudostationary phase, the separation selectivity for alkali metals and ammonium was examined under a range of background electrolyte compositions and employing indirect absorbance detection. Addition of ion-exchange particles to the background electrolyte resulted in a reduction in the observed electrophoretic mobility of the analytes due to the establishment of ion-exchange interaction with the pseudostationary phase, with the decrease in mobilities following the ion-exchange interaction order for these analytes with a sulfonated stationary phase. Increasing the concentration of the particles resulted in a uniform reduction in the electrophoretic mobility of the analytes, similar to that observed in micellar electrokinetic chromatography. Conversely, increasing the concentration of the cationic indirect detection probe (which also acted as an ion-exchange competing cation) resulted in a decrease in the ion-exchange interaction with the particles and a reduction of the relative ion-exchange contribution to the overall separation mechanism. Plots of log[retention factor] versus log[electrolyte concentration] were linear, as is the case for ion-exchange chromatography, but the observed slopes were greater than predicted from ion-exchange theory. Indirect absorbance detection was found to give poor sensitivity due to light scattering effects caused by the particles of pseudostationary phase.

Cations↗
PubMed2000

Analysis of protonated and alkali metal cationized aminoglycoside antibiotics by collision-activated dissociation and infrared multi-photon dissociation in the quadrupole ion trap.

Nine aminoglycoside antibiotics were analyzed in two quadrupole ion trap mass spectrometers using electrospray ionization. Structural information was obtained via collision-activated dissociation (CAD) and infrared multi-photon dissociation (IRMPD) of the protonated species. Several of the compounds, having multiple basic sites, preferred the doubly protonated form while some existed in the singly charged state or were distributed between single and doubly protonated species, allowing comparison of the fragmentation patterns of the two charge states. In general, IRMPD is as efficient as CAD, produces more low-mass fragment ions, and is more universally applied owing to its low dependence on trapping, pressure and tuning conditions. Alkali metal complexation using Li(+) and Na(+) was probed as a means of producing different fragmentation patterns, but in most cases the resulting fragmentation patterns were simplified versions of those obtained for the protonated analogs.

Aminoglycosides↗
PubMed2002

Alkali metal ion binding to amino acids versus their methyl esters: affinity trends and structural changes in the gas phase.

The relative alkali metal ion (M(+)) affinities (binding energies) between seventeen different amino acids (AA) and the corresponding methyl esters (AAOMe) were determined in the gas phase by the kinetic method based on the dissociation of AA-M(+)-AAOMe heterodimers (M=Li, Na, K, Cs). With the exception of proline, the Li(+), Na(+), and K(+) affinities of the other aliphatic amino acids increase in the order AA AAOMe is already observed for K(+). Proline binds more strongly than its methyl ester to all M(+) except Li(+). Ab initio calculations on the M(+) complexes of alanine, beta-aminoisobutyric acid, proline, glycine methyl ester, alanine methyl ester, and proline methyl ester show that their energetically most favorable complexes result from charge solvation, except for proline which forms salt bridges. The most stable mode of charge solvation depends on the ligand (AA or AAOMe) and, for AA, it gradually changes with metal ion size. Esters chelate all M(+) ions through the amine and carbonyl groups. Amino acids coordinate Li(+) and Na(+) ions through the amine and carbonyl groups as well, but K(+) and Cs(+) ions are coordinated by the O atoms of the carboxyl group. Upon consideration of these differences in favored binding geometries, the theoretically derived relative M(+) affinities between aliphatic AA and AAOMe are in good overall agreement with the above given experimental trends. The majority of side chain functionalized amino acids studied show experimentally the affinity order AA AAOMe. The latter ranking is attributed to salt bridge formation.

Amino Acids↗
PubMed2002

Simultaneous determination of inorganic and organic anions, alkali, alkaline earth and transition metal cations by capillary electrophoresis with contactless conductometric detection.

Simultaneous separation of up to 22 inorganic and organic anions, alkali, alkaline earth and transition metal cations was achieved in less than 3 min in the capillary electrophoresis system with contactless conductometric detector. The sample was injected from both capillary ends (dual opposite end injection) and anionic and cationic species were detected in the center of the separation capillary. The parameters of the separation electrolyte, such as pH, concentration of the electrolyte, concentration of complexing agents and concentration of 18-crown-6 were studied. Best results were achieved with electrolytes consisting of 8 mM L-histidine, 2.8 mM 2-hydroxyisobutyric acid, 0.32 mM 18-crown-6 at pH 4.25 or 9 mM L-histidine, 4.6 mM lactic acid, 0.38 mM 18-crown-6 at pH 4.25. Other electrolytes containing complexing agents such as malic or tartaric acid at various concentrations could also be used. The detection limits achieved for most cations and anions were 7.5 - 62 micro gL(-1) except for Ba2+ (90 micro gL(-1)), Cd 2+, Cr 3+ and F- (125 micro gL(-1)), and fumarate (250 micro gL(-1)). The repeatability of migration times and peak areas was better than 0.4% and 5.9%, respectively. The developed method was applied for analysis of real samples, such as tap, rain, drainage and surface water samples, plant exudates, plant extracts and ore leachates.

Anions↗
PubMed2005

Study of alkali metal cations binding selectivity of beta-cyclodextrin by ESI-MS.

Cyclodextrins (CDs), cyclic oligosaccharides commonly composed of six, seven or eight (alpha, beta, and gamma respectively) D-glucopyranosyl units connected by alpha-(1,4)- glycosidic linkages, have the ability to form inclusion complexes with a wide range of substrates in aqueous solution. This property has led to their applications in different areas such as enzyme mimics, catalysis and the encapsulation. of drugs. ESI-MS has begun to be viewed as a useful tool for investigating the general area of molecular recognition thus providing a powerful mean for the analysis of a wide array of host-guest complexes and other non covalent complexes present in solution. The evaluation of the binding selectivity of beta-cyclodextrin towards the first group alkali cations is reported. The estimation of the affinity degrees has been achieved by competition ESI-MS experiments. In these experiments beta-CD was incubated at the presence of two different cations at the same time, and the ratio of the mass peaks corresponding to the two complexes was calculated. In general, it appears a much larger affinity of the beta-cyclodextrin molecule with sodium with respect to all the other alkaline cations, thus giving evidence that it is the size of the beta-cyclodextrin ring in relation with the cationic radius, which drives the formation of what, at this point, could be defined as an inclusion complex.

Carcinogens↗
PubMedDate not supplied

Alkali-labile luminol derivatives as labels for quantitative binding studies with polyionic macromolecules.

Acylated derivatives of luminol (5-amino-2,3-dihydro-1,4-phthalazinedione) bearing a carboxyl or amino group can be linked by amide bonds to a macromolecule requiring labelling. Though themselves of low quantum yield these compounds are alkali-labile and can be detected at a similar level of sensitivity to the parent compound luminol. These cheap, readily accessible compounds are less hydrophobic than other currently employed chemiluminescent labels. They also lack a positively charged nitrogen atom which could complicate their covalent linkage to polyanionic compounds. They thus appear well suited for labelling heparin and other macromolecules which interact with the luminal surface of blood vessels.

Alkalies↗
PubMed2006

Identification of isocephalomannine in the presence of cephalomannine isomers and alkali metal ion adducts in a paclitaxel active pharmaceutical ingredient using electrospray tandem mass spectrometry.

A strategy is developed for the identification of isocephalomannine in the presence of alkali metal ion adducts and other cephalomannine isomers in a paclitaxel active pharmaceutical ingredient. Intact molecular ion analyses and a sub-structural study have been performed for the differentiation of isocephalomannine (2-debenzoylpaclitaxel-2-pentenoate) from cephalomannine and 7-epi-cephalomannine. A comparative study of the cephalomannine isomers was carried out using molecular ions (MS) and fragmentation patterns (MS/MS) for sub-structural analysis. An attempt has been made to identify isocephalomannine in Cremophor(R) EL formulations.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Alkali metal ions protect mitochondrial rhodanese against thermal inactivation.

Incubation of bovine liver mitochondrial rhodanese in dilute, reducing solutions at temperatures ranging between 30 and 45 degreesC conduced to a rapid loss of enzymatic activity. This inactivation was substantially reduced in the presence of millimolar concentrations of alkali metal ions, divalent cations (including Mg2+, Ca2+, and Ba2+) were ineffective. The extent of protection afforded by monovalent cations was highly dependent on their ionic radii, with K+ and Na+ ions being the most effective protective agents. The protection afforded by a number of anions, including thiosulfate, could be totally ascribed to the presence of the accompanying monovalent cation. The overall results indicate that K+ and Na+, at concentrations and temperatures within the physiological range, substantially contribute to the stabilization of the functional structure of rhodanese.

Animals↗
PubMed1984

Protein-alkali reactions: chemistry, toxicology, and nutritional consequences.

Heat and alkali treatment of proteins catalyzes formation of crosslinked amino-acid side chains such as lysinoalanine, ornithino-alanine and lanthionine, and concurrent racemization of L-isomers of all amino acid residues to D-analogues. Factors that favor these transformations include high pH and temperature, long exposure, and certain inductive or steric properties of the various amino acid side chains. Factors that minimize crosslink formation include the presence of certain additives, such as cysteine or sulfite ions, and acylation of epsilon-NH2 groups of lysine side chains. Free and protein-bound lysinoalanine and D-serine induce nephrocytomegaly in rat kidney tissues. The presence of lysinoalanine and D-amino acid residues along a protein chain decreases its digestibility and nutritional quality. Understanding the factors that govern the formation of potentially harmful unnatural amino acid residues in food proteins and the toxic and nutritionally antagonistic action of these compounds in animals should lead to better and safer foods.

Alkalies↗
PubMed1984

DNA of Chinese hamster V79 cells newly synthesized after ultraviolet irradiation contains alkali-labile sites.

Pulse-labeled daughter DNA of UV-irradiated Chinese hamster V79 cells was denatured in alkaline or neutral conditions and analysed by sucrose gradient centrifugation. A comparison of the sedimentation profiles of DNA treated in alkaline or neutral conditions has shown that in UV-irradiated cells some alkali-labile sites are produced during replication of damaged templates.

Alkalies↗
PubMed1991

Acid and alkali as aids in differentiation of pathogenic Nocardia and for their isolation from clinical specimens.

The tolerance of Nocardia brasiliensis, Nocardia asteroides and Nocardia caviae to different concentrations of acids and alkalis was studied in this work. The purpose was to determine their use: (a) in the differentiation of species; (b) for decontamination of clinical materials during the isolation of pathogenic Nocardia. The results showed (1) that both 2 M NH3 and 0.05 M H2SO4 solutions are useful for differentiating species. They can also be used as a complementary method for identification. (2) That both 1 M NH3 and 0.05 M H2SO4 solutions were useful for decontamination of clinical materials during the isolation of pathogenic Nocardia.

Acetates↗
PubMed1984

Alkali metal ion selectivity of the hemocyanin channel.

The selectivity of the hemocyanin channel was measured for alkali metal ions and ammonium. Permeability ratios relative to K+ measured from biionic potentials were: NH4+ (1.52) greater than Rb+ (1.05) greater than K+ (1.0) greater than Cs+ (0.89) greater than Na+ (0.81) greater than Li+ (0.35). Single-channel ion conductance was a saturating function of ion concentration regardless of the cation present in the bathing medium. Maximal conductances were 270, 267, 215, 176, 170 and 37 ps for K+, Rb+, NH4+, Cs+, Na+ and Li+, respectively. Current-voltage curves for the different monovalent cations were measured and described using a three-barrier model previously used to explain the voltage dependence of the "instantaneous" channel conductance (Cecchi, Alvarez & Latorre, 1981). In this way, binding and peak energies were estimated for the different ions. Considering the energy peaks as transition states between the ion and the channel, it is concluded that they follow Eisenman's selectivity sequences XI (cis peak, i.e., Li+ greater than Na+ greater than K+ greater than Rb+ greater than Cs+; highest field strength), VII (central peak) and II (trans peak). The cis side was that to which hemocyanin was added and was electrically ground. The binding energies, on the other hand, follow Eisenman's series XI for strong electric field sites. Binding of NH4+ to the cis-well suggests that the orientation of the ligands in the site is tetrahedric.

Hemocyanins↗
PubMed1985

The alkali burned cornea: electron microscopical, enzyme histochemical, and biochemical observations.

The early phase of wound healing after small central alkali burns of the guinea pig cornea was studied using electron microscopical, enzyme histochemical, and biochemical techniques. In the first phase, which was morphologically characterized by the destruction of the epithelium and keratocytes and by the infiltration of the cornea with polymorphonuclear leukocytes, an increase in the activity of lysosomal phosphatases and glycosidases (beta-D-glucuronidase, acid beta-D-galactosidase, beta-D-N-acetylglucosaminidase) was noticed. In the second phase, the cornea was invaded by capillaries and fibroblasts. In this phase, the activity of proteases (aminopeptidase M, dipeptidyl peptidase IV) increased intra- and extracellularly, suggesting that these enzymes may be involved in the turnover of the collagenous matrix and the ground substance. Using synthetic 4-methoxy-2-naphthylamine substrates and fluorescence-band detection techniques after isoelectric focusing, an increase in the activity of endopeptidases was demonstrated. The decreased activity of gamma-glutamyl transpeptidase may be linked with the activation of latent collagenase.

Alkalies↗