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Results 451 - 500 of 1100
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Houston Todd A - - 2003
Certain glycosidase inhibitors possess potent antiviral, antitumour and antidiabetic properties. Glyconic acid lactones, the earliest glycosidase inhibitors identified, have planar anomeric carbons that mimic the transition state of glycoside hydrolysis. Other classes include lactams, glycals, epoxides, halides and sulfonium ions, the latter based on the natural product salacinol from an ...
Perry S F - - 2003
In freshwater fishes, the gill and kidney are intricately involved in ionic and acid-base regulation owing to the presence of numerous ion channels, pumps, or exchangers. This review summarizes recent developments in branchial and renal ion transport physiology and presents several models that integrate epithelial ion and acid-base movements in ...
Lemann Jacob J - - 2003
The sources and rates of metabolic acid production in relation to renal net acid excretion and thus acid balance in humans have remained controversial. The techniques and possible errors in these measurements are reviewed, as is the relationship of charge balance to acid balance. The results demonstrate that when acid ...
Rõõm Eva-Ingrid - - 2003
The UV-vis spectrophotometric ion-pair acidity scale in heptane has been significantly expanded: it includes now 21 bulky CH and NH indicator acids and spans for about 10 pKip units. The phosphazene base t-Bu-P4 was used for deprotonating. The correlations between acidities in heptane versus gas-phase acidities or acidities in DMSO ...
Ganjali Mohammad Reza - - 2003
A novel imidazole membrane sensor based on 2,4,6-triphenyl thiopyrilium perchlorate (TTP) as an excellent charged carrier, poly(vinyl chloride) (PVC), the plasticizer dibutyl phthalate (DBP) and oleic acid as an additive is described. The sensor responds to imidazole over a wide concentration range from 1.0 x 10(-5) to 1.0 x 10(-1) ...
Boyle M - - 2003
The Stewart approach defines acid/base abnormalities as resulting from changes in PCO2, strong ion difference (SID), and weak acids (mainly albumin) but needs a computer for calculation. The base excess (BE) is a measure of the net effect of changes in SID and weak acids, therefore, metabolic acid/base balance can ...
Sun Chenhang - - 2003
In this work, various techniques for solid surface acid-base (AB) characterization are reviewed. Different techniques employ different scales to rank acid-base properties. Based on the results from literature and the authors' own investigations for mineral oxides, these scales are compared. The comparison shows that Isoelectric Point (IEP), the most commonly ...
Corey Howard E - - 2003
The Henderson-Hasselbalch equation and the base excess have been used traditionally to describe the acid-base balance of the blood. In 1981, Stewart proposed a new model of acid-base balance based upon three variables, the "strong ion difference" (SID), the total weak acids (ATot), and the partial pressure of carbon dioxide ...
Lengyel Z - - 2003
Holstein-Friesian bulls were slaughtered at 7, 14 and 19 months of age. Samples were collected from the psoas major, longissimus and semitendinosus muscles. The total lipids (TL) of the samples were extracted and the fatty acid compositions were analysed by gas chromatography. Both the slaughtering age and the type of ...
Murrieta C M - - 2003
Methanolic reagents containing acidic catalysts, HCl (0.5 M, 1 h, 80° C) or BF(3) (14%, 1 h, 80° C), or alkaline catalysts, KOH (0.2 M, 15-60 min, 50° C) or NaOCH(3) (0.5 M, 15-60 min, 50° C), were compared for use in preparation of fatty acid methyl esters for GC ...
van Ameijde Jeroen - - 2003
The convenient synthesis of novel trivalent amino acid glycoconjugates based on cyclotriveratrylene ('CTV') is described. These constructs consist of the CTV scaffold, three oligoethylene glycol spacers of variable length connected to a glyco amino acid residue which can also be varied. The resulting library of trivalent glycoconjugates can be used ...
Feriani Mariano - - 2003
The feedback between metabolic acid production and dialytic base gain ensures a neutral acid-base balance in patients on renal replacement therapy (RRT). Despite acid not accumulating continuously, clinical studies demonstrated that normalizing pre-dialysis serum bicarbonate results in nutritional and osteodystrophy improvements. Full correction of acidosis is not an easy task ...
Liu Yan - - 2003
Eumelanin was isolated from a sample of black, Indonesian human hair using three different published procedures: two different acid/base extractions and an enzymatic extraction. The morphology and spectroscopic properties of the isolated pigments differ significantly. The acid/base procedures both yield an amorphous material, while enzymatic extraction yields ellipsoidal melanosomes. Amino ...
Rini Matteo - - 2003
The neutralization reaction between an acid and a base in water, triggered after optical excitation, was studied by femtosecond vibrational spectroscopy. Bimodal dynamics were observed. In hydrogen-bonded acid-base complexes, the proton transfer proceeds extremely fast (within 150 femtoseconds). In encounter pairs formed by diffusion of uncomplexed photoacid and base molecules, ...
Zheng Jianzhong - - 2003
Interfacial tension, which is a critical variable affecting multiphase flow of nonaqueous phase liquids (NAPLs) in the subsurface, varies greatly with the composition of complex NAPLs recovered from field sites. Much of this variability stems from the presence of acid and base molecules in the NAPL mixture. The interfacial tension ...
Sarikaya Rabia - - 2003
A 96-h LC(50) values of 2,4-D [(2,4-dichlorophenoxy)acetic acid], a common contaminating agricultural herbicide, were determined on the adult common carp (Cyprinus carpio L., 1758; Pisces, Cyprinidae). The study was conducted in two stages using 130 carp. The data obtained were statistically evaluated by the use of the EPA computer program ...
Liu Wen-xin - - 2003
FT-IR, Raman microscopy, XRD, 29Si and 27Al MAS NMR, were used to investigate changes in surface properties of a natural illite sample after acid-base potentiometric titration. The characteristic XRD lines indicated the presence of surface Al-Si complexes, preferable to Al(OH)3 precipitates. In the microscopic Raman spectra, the vibration peaks of ...
Lin Y - - 2003
OBJECTIVE: To make a study of the detailed microanatomy of endoscope-assisted glabellar nasal keyhole approach (GNKA) to be used clinically. METHODS: 10 dry adult Chinese skulls were measured and 10 perfused cadaveric heads were dissected to mimic the GNKA. RESULTS: Average distances between bilateral supraorbital foramen/incisure, supratrochlear incisure, medial orbital ...
Wall Dennis P - - 2003
In this study we reconstruct the evolution of codon usage bias in the chloroplast gene rbcL using a phylogeny of 92 green-plant taxa. We employ a measure of codon usage bias that accounts for chloroplast genomic nucleotide content, as an attempt to limit plausible explanations for patterns of codon bias ...
Ozawa Y - - 2003
Translation termination is catalyzed by release factors that recognize stop codons. However, previous works have shown that in some bacteria, the termination process also involves bases around stop codons. Recently, Ito et al. analyzed release factors and identified the amino acids therein that recognize stop codons. However, the amino acids ...
Noguchi Yasushi - - 2003
In this short paper, we suggest some concepts and methods that may be useful in considering a metabolomic approach to the study of amino acid adequacy and safety. We suggest that the analysis of a metabolomic subset, such as amino acids, may yield useful information, and that correlation-based analyses could ...
Liu Ji-Kai - - 2003
A glucosylceramide with novel ceramide and three novel ceramide homologs were isolated from the basidiomycete Cortinarius umidicola and structurally characterized. The ceramide portion of the glucocerebroside consists of a rare (4E,8E)-9-methyl-4,8-sphingadienine sphingoid base. In contrast, the three ceramide homologs, while having the same sphingoid base, contain as FA residues 2-hydroxydocosanoic ...
Lou Yan - - 2003
Two new routes to hexafluorotropone have been developed, one from hexachlorotropone and a superior synthesis from hexafluorobenzene. Hexafluorotropone was found to be a very weak base, with a conjugate acid pK(a) of -6.2 +/- 0.5. The tropone adds in [6 + 4] fashion to cyclopentadiene and photocyclizes to hexafluorobicyclo[3.2.0]hepta-3,6-dien-2-one. Lithium ...
Goodwin Catherine E - - 2003
(3R)- and (3S)-Deuteriated forms of 5-aminolaevulinic acid have been synthesized and the (3R)-form shows a significantly larger isotope effect when incubated with porphobilinogen synthase from bovine liver and from Bacillus subtilis; based on this and on available crystal structures, a modified mechanism for the enzymic reaction is proposed.
Susan Md A B H - - 2003
Novel Brønsted acid-base ionic liquids, derived from a simple combination of a wide variety of organic amines with bis(trifluoromethanesulfonyl) amide are electroactive for H2 oxidation and O2 reduction at a Pt electrode under non-humidifying conditions, which shows the prospect of the use of protic ionic liquids as new materials for ...
Wang Wen-Qing - - 2003
Life is based on L-amino acids and D-sugars rather than the enantiomeric D-amino acids and L-sugars. This broken symmetry is now believed to be a feature of fundamental physics-a result of symmetry-breaking induced by the weak force, which makes one enantiomer slightly more stable than the other. An amplification mechanism ...
Gohier Frédéric - - 2003
Upon treatment of 3-chloro/bromobenzoic acids with hindered lithium dialkylamides (LDA or LTMP) at -50 degrees C, lithium 3-chloro/bromo-2-lithiobenzoates are generated. These dianions can be trapped as such to afford after electrophilic quenching a variety of simple 2-substituted-3-chloro/bromobenzoic acids. The 3-bromo-2-lithiobenzoate is less stable than the corresponding 3-chloro derivative and partly ...
Bevilacqua Philip C - - 2003
Several small ribozymes carry out self-cleavage at a specific phosphodiester bond to yield 2',3'-cyclic phosphate and 5'-hydroxyl termini. Prior mechanistic and structural studies on the HDV ribozymes led to the proposal that the pK(a) of C75 is shifted toward neutrality, making it an effective general acid. Recent mechanistic studies on ...
Umebachi Yoshishige - - 2003
Hypodermal injection of Toughmac-E, a digestive mixture composed of nine digestive components, or Molsin induced perturbation of the wing color pattern in 0- to 2-day-old pupae of Papilio xuthus, but had no effect on prepupae or 3- to 4-day-old pupae. The effective component in Toughmac-E was identified as Molsin, an ...
Doménech-Carbó A - - 2003
An electrochemical method for identifying anthraquinone-type dyes in microsamples from works of art, based in the voltammetry of microparticles approach, is reported. Upon attachment onto graphite/polyester composite electrodes, natural pigments aloe, henna, cochineal red, madder lake, kermes, shellac, and alizarin and purpurin taken as reference materials can be identified from ...
Alvarez-Romero Giaan A - - 2003
The traditional method of calculating equilibrium constants in glacial acetic acid medium was developed by Kolthoff and Bruckenstein in 1957; thenceforth, and even presently, few alternatives have been made available to undertake such studies. This paper presents the results obtained with the use of the program Superquad to assess the ...
Du Wu - - 2003
Thiol- or acid-promoted additions of silyl radicals to camptothecin are reported. At 105 degrees C, mixtures of 7-silyl (favored) and 12-silyl camptothecins are formed alongside substantial amounts of recovered camptothecin. At 160 degrees C, 12-silyl isomers are formed preferentially, but the total mass balance is substantially reduced. The silyl radical ...
Burke R M - - 2003
The effectiveness of organic acids (acetic, citric, lactic) and a citrus juice marinade as tenderising agents in shin beef muscle was investigated. At 0.2 M, citric acid was more effective as a tenderising agent than acetic or lactic acid. Immersion of shin beef strips in citric acid (0-0.05 M) showed ...
Alfieri Alessandra - - 2003
OBJECTIVE: The pterygopalatine fossa is a relatively small anatomic region. Because of its rich vasculonervous contents and its connections with several intracranial and extracranial compartments, it is of particular surgical interest. Because of its deep localization and despite its small size, however, it can require extensive anatomic approaches, especially for ...
Mong Tony Kwok-Kong - - 2003
The total synthesis of the sialic acid-containing antigenic epitope fucose GM(1) (Fuc-GM(1)) by an improved reactivity-based one-pot synthetic strategy is reported. Based on a thioglycoside reactivity database, three saccharide building blocks, 3, 4, and 5, were designed and prepared to incorporate a descending order of reactivity toward thiophilic activation. Using ...
Seela Frank - - 2003
6-Aza-5-methyl-2'-deoxyisocytidine (1a) and 6-aza-2'-deoxyisocytidine (1b) have been synthesized, converted into phosphoramidite building blocks, and incorporated into oligodeoxynucleotides. The glycosylic bond stability of 1a,b under acidic conditions increases compared to that of 5-methyl-2'-deoxyisocytidine (2a) and 2'-deoxyisocytidine (2b). Oligonucleotides incorporating 1a or 1b show an enhanced stability against the 3'-exonuclease snake-venom phosphodiesterase. ...
Swann Alan C - - 2003
Aggression results from the interaction of multiple systems. It can be classified as predatory, impulsive, or based on a medical condition. The likelihood of aggression is increased by environmental overstimulation or stress, transmitter balances favoring dopamine and excitatory amino acid transmission over serotonin and gamma-aminobutyric acid transmission, and the presence ...
Madias Nicolaos E - - 2003
Hypoventilation increases PaCO(2) (hypercapnia) and initiates the acid-base disorder known as respiratory acidosis. Hyperventilation decreases PaCO(2) (hypocapnia) and initiates the acid-base disorder known as respiratory alkalosis. The impact on acidity of these primary changes in PaCO(2) is ameliorated by secondary, directional changes in plasma bicarbonate concentration that occur in two ...
Mueller Udo - - 2003
Amino acids represent basic elements of proteins, which as a main source of nutrition themselves serve as a major reserve for maintaining essential functions of humans as well as animals. Taking the recent state of scientific knowledge into account, the industrial sector of amino acids is a priori "suitable" to ...
Kawano Shin - - 2002
Ribonuclease NW (RNase NW), the wound-inducible RNase in Nicotiana glutinosa leaves, preferentially cleaves guanylic acid. We expressed the cDNA encoding RNase NW in the methylotrophic yeast Pichia pastoris using the expression vector pPIC9K, and the resulting recombinant RNase NW (ryRNaseNW) secreted into medium was purified to apparent homogeneity using column ...
Maslarska Vania - - 2003
Based on precise analysis of the acid-base equilibrium, a new approach in the treatment of experimental data from a potentiometric titration is proposed. A new general formula giving explicitly the relation V=f([H(+)]) is derived, valid for every acid-base titration, which includes mono- and polyfunctional protolytes and their mixtures. The present ...
van Staden J Koos F - - 2002
A potentiometric SI titration system for the determination of total acidity in soft drinks is proposed. The concept is based on the aspiration of the acid soft drink sample between two base zones into a holding coil with the volume of the first base zone twice to that of the ...
Uhlmann Petra - - 2002
For a specific design of interfaces, i.e. in composites and blends, it is essential to know the surface thermodynamics of the components. Polyethylene grafted with maleic anhydride and maleic anhydride-styrene mixtures, respectively, was the component of interest of our investigations. Inverse gas chromatography (IGC) at infinite dilution was shown to ...
Cipolla Laura - - 2002
Bi- and tricyclic compounds were synthesized starting from fructose. The different hydroxyl groups present in fructose were exploited in the formation of a number of conformationally constrained sugar-based scaffolds, including azido acids. Introduction of an azido group and carboxy terminus into different bicyclic iodo ethers, allowed the synthesis of different ...
Schnabelrauch Matthias - - 2002
Novel linear and star-shaped oligolactide macromers were synthesized by ring-opening oligomerization of L-lactide in the presence of suitable initiators (di- and polyols, amino acid esters) and subsequent endgroup-functionalization of the formed oligolactides with methacrylate moities. The obtained liquid macromers are valuable building blocks for the preparation of biocompatible polymer networks. ...
Claiborne James B - - 2002
The mechanisms underlying acid-base transfers across the branchial epithelium of fishes have been studied for more than 70 years. These animals are able to compensate for changes to internal pH following a wide range of acid-base challenges, and the gill epithelium is the primary site of acid-base transfers to the ...
Taamasri Paanjit - - 2002
Blastocystis hominis is one of the most common intestinal parasites found in humans. The prevalence of B. hominis carriage in personnel who worked in the First Army Support Command, Chonburi, Thailand, was determined. Forty-four percent of 616 stool samples were positive for B. hominis using both simple smear and concentration ...
Lorenz John N - - 2002
ROMK is an apical K(+) channel expressed in the thick ascending limb of Henle (TALH) and throughout the distal nephron of the kidney. Null mutations in the ROMK gene cause type II Bartter's syndrome, in which abnormalities of electrolyte, acid-base, and fluid-volume homeostasis occur because of defective NaCl reabsorption in ...
Goeppert Alain - - 2002
The H/D exchange observed when methane is contacted with D(2)SO(4) at 270-330 degrees C shows that the alkane behaves as a sigma base and undergoes rapid and reversible protonation at this temperature. DFT studies of the hydrogen exchange between a monomer and a dimer of sulfuric acid and methane show ...
Munshi Pradip - - 2002
A trace amount of alcohol cocatalyst and a stoichiometric amount of base are required during the hydrogenation of CO(2) to formic acid catalyzed by ruthenium trimethylphosphine complexes. Variation of the choice of alcohol and base causes wide variation in the rate of reaction. Acidic, nonbulky alcohols and triflic acid increase ...
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