Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Conformational states of fibrinogen and fibrin monomer were studied by methods of differential and solvent-perturbation spectrophotometry and ultraviolet fluorescence at about neutral pH (6.5) and in the region of lower pH, 3.2 to 4.0. To prevent repolymerization of fibrin monomer at pH 6.5, urea was added in a non-denaturing concentration of 1.7 M. In the acid region specified, the immediate environment of tyrosine and tryptophan residues was found to be more polar and the accessibility to perturbants higher than at pH 6.5. Much more drastic changes of the same type occurred at pH less than 3 when denaturation of the protein takes place. The conformation of fibrinogen altered progressively upon lowering pH from 4.0 to 3.2. This acidity increase, practically, did not influence the conformation of fibrin monomer. Thus the tolerance of the latter to the appearance of the new positively changed groups seems to be comparably high. The bulk of the conformational changes subsequent upon neutralization of an acid fibrin monomer solution proceeds at a higher rate than the activation transition, i.e. the acquirement of a state of polymerization readiness by fibrin monomer molecules.
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PMID:[Fibrinogen and fibrin monomer conformation changes dependent of pH magnitude]. 0 45

A new method specific for the determination of subpicomole quantities of tryptophan has been developed by elaboration of the Pictet-Spengler reaction. It permitted reproducible quantitation of tryptophan in less than 1 microliter of plasma ultrafiltrate or 1 mg of brain tissue. Samples deproteinized by trichloroacetic acid were boiled for 15 min with formaldehyde and potassium ferricyanide at controlled acidity, where tryptophan was converted to a single new product identified as 9-hydroxymethyl-beta-carboline. It was quantitated by either direct spectrofluorometry or a reversed-phase HPLC system developed for beta-carbolines. Under our conditions, peptides containing N-terminal tryptophan such as Trp-Leu and delta sleep-inducing peptide gave N-(9-hydroxymethyl-beta-carboline-3-carbonyl) peptides which retained all amino acid residues except tryptophan.
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PMID:Picomole analyses of tryptophan by derivatization to 9-hydroxymethyl-beta-carboline. 662 80

The stability of amino acids and the availability of acid from total parenteral nutrition (TPN) solutions containing hydrochloric acid were studied. Hydrochloric acid in the concentrations of 40 (TPN 1), 60 (TPN 2), and 100 (TPN 3) meq/liter was added to TPN solutions (4.25% amino acids, 25% dextrose monohydrate) containing various electrolytes (TPN control). Amino acid concentrations were determined from one sample of each solution using a Technicon Automatic Amino Acid Analyzer. Samples were analyzed 24 hours after mixing and compared with the TPN control at 24 hours. Tryptophan was assayed using a specific colorimetric assay at 0, 6, 24, and 48 hours. The concentrations of proline (76.2 of control) and histidine (85.7% of control) wee decreased in TPN 3. This phenomenon appeared to be dependent upon the concentration of hydrochloric acid in the TPN solution. There was no appreciable loss of any of the other amino acids in the test solution as compared with the control. Tryptophan levels fell in both the TPN control and the test solutions independent of the hydrochloric acid concentration. The pH of the solutions decreased with increasing concentrations of hydrochloric acid from 5.87 in the TPN control to 3.18 in TPN 3. The titratable acidity increased with increasing concentrations of hydrochloric acid (28.21 meq/liter in the TPN control to 115.54 meq/liter in TPN 3). Concentrations of some amino acids decreased in the presence of hydrochloric acid. Because of the short-time period in which these solutions will usually be infused (4-24 hours), this probably has a negligible effect on patients' nutritional therapy. The availability of acid from these solutions makes this combination useful in treating severe metabolic alkalosis.
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PMID:Stability of amino acids and the availability of acid in total parenteral nutrition solutions containing hydrochloric acid. 679 23

Proteins induced by acid or base, during long-term aerobic or anaerobic growth in complex medium, were identified in Escherichia coli. Two-dimensional gel electrophoresis revealed pH-dependent induction of 18 proteins, nine of which were identified by N-terminal sequencing. At pH 9, tryptophan deaminase (TnaA) was induced to a high level, becoming one of the most abundant proteins observed. TnaA may reverse alkalinization by metabolizing amino acids to produce acidic products. Also induced at high pH, but only in anaerobiosis, was glutamate decarboxylase (GadA). The gad system (GadA/GadBC) neutralizes acidity and enhances survival in extreme acid; its induction during anaerobic growth may help protect alkaline-grown cells from the acidification resulting from anaerobic fermentation. To investigate possible responses to internal acidification, cultures were grown in propionate, a membrane-permeant weak acid which acidifies the cytoplasm. YfiD, a homologue of pyruvate formate lyase, was induced to high levels at pH 4.4 and induced twofold more by propionate at pH 6; both of these conditions cause internal acidification. At neutral or alkaline pH, YfiD was virtually absent. YfiD is therefore a strong candidate for response to internal acidification. Acid or propionate also increased the expression of alkyl hydroperoxide reductase (AhpC) but only during aerobic growth. At neutral or high pH, AhpC showed no significant difference between aerobic and anaerobic growth. The increase of AhpC in acid may help protect the cell from the greater concentrations of oxidizing intermediates at low pH. Isocitrate lyase (AceA) was induced by oxygen across the pH range but showed substantially greater induction in acid or in base than at pH 7. Additional responses observed included the induction of MalE at high pH and induction of several enzymes of sugar metabolism at low pH: the phosphotransferase system components ManX and PtsH and the galactitol fermentation enzyme GatY. Overall, our results indicate complex relationships between pH and oxygen and a novel permeant acid-inducible gene, YfiD.
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PMID:Acid- and base-induced proteins during aerobic and anaerobic growth of Escherichia coli revealed by two-dimensional gel electrophoresis. 1009

Iron can react with citric acid, interfering with the Krebs cycle, hence with oxidative phosphorylation. Free iron (Fe) can cause considerable oxidative damage both through Fenton reactions and by activating xanthine oxidase, which produces both superoxide (O(2-)) and uric acid (abundant in many cancers). It can also react with lactic acid, reducing its elimination and increasing the acidity of the cytoplasm. Fe can also wreak havoc by reacting with tryptophan, the least abundant and most delicate essential amino acid, which is necessary for the production of serotonin and other substances required by the immune system to fight cancer. On the other hand, in the presence of iron, the tryptophan metabolite quinolinate causes intense lipid peroxidation. Similarly, several other carcinogenic metabolites of tryptophan are particularly dangerous in the presence of Fe. Excess Fe may also interfere with manganese superoxide dismutase and impair the initiation of apoptosis by the mitochondrion, rendering the cells impervious to all the signals to undergo apoptosis from without and from within the cell. Moreover, Fe may also play a crucial role on telomere repair, by activating telomerase. Therefore, by inhibiting apoptosis and enhancing chromosome repair, Fe may bestow immortality upon the cancer cell. Furthermore, Fe is one of the triggers for mitosis. Therefore, increased Fe levels may be essential for the rapid growth characteristic of many malignancies. In turn, the rapid growth further depletes resources from the healthy tissues, exacerbating the deficiencies of the other elements and reducing the ability to fight the malignancy.
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PMID:The possible crucial role of iron accumulation combined with low tryptophan, zinc and manganese in carcinogenesis. 1173 7

The influence of different denaturants on the phosphorescence spectrum and lifetime decay of Escherichia coli alkaline phosphatase (AP) was investigated. Phosphorescence intensity and lifetime of tryptophan residue (Trp-109) decrease upon addition of guanidine hydrochloride, ethylene diamine tetraacetic acid, and urea or decreasing acidity. The experiments show that AP undergoes different pathways with different denaturants and that the activation energy data, DeltaS degrees (not equal) and deltaH degrees (not equal) further confirm that there is a stable intermediate state between the folded and unfolded AP states in solution.
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PMID:Study on Escherichia coli alkaline phosphatase conformation by phosphorimetry in the presence of denaturant. 1458 94

Procedures are described for the determination of organic compounds with iodine trichloride under Andrews's titration conditions. Samples are directly titrated with iodine trichloride or first reacted with an excess of iodine monochloride, with subsequent titration of the iodine formed. The direct titration is done initially in feebly acid medium, then the acidity is raised (biotin, methionine, cystine and thiomersal). Pre-oxidation with iodine monochloride is used if the organic compound reacts slowly [tryptophan and arsenic(III) compounds] or is determined in bicarbonate medium (hydroxylamine and thiosemicarbazide). The ferrocyanide formed by the reduction of ferricyanide (by thiourea and allylthiourea) can also be titrated. Arsenic(V) compounds are determined after reduction to arsenic(III), and iodine in organic compounds is converted into iodide by alkaline fusion into iodide and the iodide titrated.
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PMID:Iodine trichloride as an analytical reagent for determination of some organic compounds. 1896 22

Extractive fermentation using aqueous biphasic systems (ABS) is a promising separation process since it provides a nondenaturing environment for biomolecules and improves the stability of cells. Due to environmental concerns and toxicity issues related with common volatile organic solvents, ionic liquids (ILs), a new class of nonvolatile alternative solvents, are being currently investigated for extraction purposes. In this work, a wide range of imidazolium-based ILs was studied aiming at obtaining new insights regarding their ability toward the formation of ABS and their capacity to the extraction of biomolecules. On the basis of the IL cations 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium, the IL anion influence on ABS formation was assessed through their combination with chloride, bromide, acetate, hydrogensulfate, methanesulfonate, methylsulfate, ethylsulfate, trifluomethanesulfonate, trifluoroacetate, and dicyanamide. Ternary phase diagrams (and respective tie-lines) formed by these hydrophilic ILs, water, and the inorganic salt K(3)PO(4), were measured and are reported. The results indicate that the ability of an IL to induce ABS closely follows the decrease in the hydrogen bond accepting strength or the increase in the hydrogen bond acidity of the IL anion. In addition, the extraction capacity of the studied ABS was evaluated through their application to the extraction of an essential amino acid, L-tryptophan. It is shown that the partition coefficients obtained between the IL and the K(3)PO(4)-aqueous rich phases were substantially larger than those typically obtained with polymers-inorganic salts or polymers-polysaccharides aqueous systems.
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PMID:Evaluation of anion influence on the formation and extraction capacity of ionic-liquid-based aqueous biphasic systems. 1951 15

By research, it was found that the Amsacrine (AMSA) can interact with bovine serum albumin (BSA). In this work, the AMSA was adopted as a sonosensitizer and the Metronidazole (MET) was used as a sensitizer to further damage BSA molecules under ultrasonic irradiation. It could be concluded that the damage degree of BSA molecules in the presence of AMSA and MET was more serious than in the presence of pure AMSA. That is, MET could aggravate the damage to BSA molecules under ultrasonic irradiation combined with AMSA. Meanwhile, the damage degree of BSA molecules was also influenced by some factors, such as ultrasonic irradiation time, MET concentration and solution acidity. In addition, the damage site of BSA molecules was estimated by synchronous fluorescence spectra. It was found that the tyrosine (Tyr) and tryptophan (Typ) residues were damaged almost averagely. Perhaps, these research results are of great significance for driving sonodynamic method to treat tumor in clinic application.
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PMID:Assisted sonodynamic damage of bovine serum albumin by metronidazole under ultrasonic irradiation combined with photosensitive antitumor drug-Amsacrine. 2000 32

Four novel alanine-based indolicidin peptide derivatives were designed containing one WPW motif and two alanine residues, resulting in peptides of similar sequence. The separation of these peptides with identical physicochemical properties including molar mass, charge, and secondary structure as characterized by circular dichroism spectroscopy is very difficult; and the separation of peptides with differing physicochemical properties has only previously been reported. Capillary electrophoresis parameters such as separation buffer concentration, separation buffer pH, capillary length, and separation voltage were investigated to optimize the analysis. Using optimized conditions of a background electrolyte containing 5 mM formic acid of pH 2.0, total capillary length of 51 cm and a voltage of 10 kV enabled a baseline separation of the four peptides. The relative standard deviation of the peak areas and migration times for method repeatability (n = 3) were found to be lower than 8% and 3%, respectively. In addition, reasoning for the separation of these peptides is proposed based on the acidity of the formic acid buffer and the hydrophobic grouping of the tryptophan residues in the peptide primary sequence.
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PMID:The design and synthesis of alanine-based indolicidin derivatives with identical physicochemical properties and their separation using capillary electrophoresis. 2092 63


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