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

Proton magnetic resonance studies of the acid-base chemistry of the glycyl ammonium, histidyl imidazolium, and lysyl ammonium groups of glycyl-L-histidyl-L-lysine and of the glycyl ammonium and histidyl imidazolium groups of glycyl-L-histidine and glycyl-L-histidylglycine are described. Chemical-shift data indicate that, at the molecular level, the glycyl ammonium and the histidyl imidazolium groups are titrated over the same pH range, with the acidity of the imidazolium group some 8 to 10 times that of the glycyl ammonium group, depending on the peptide. The lysyl ammonium group of Gly-His-Lys is much less acidic and is titrated over a higher pH range. Microscopic and macroscopic acid-dissociation constants were determined from chemical-shift data for each of the peptides. It is shown how microscopic formation constants for protonated metal complexes of these ligands, which are being used increasingly as models for the binding of metal ions by proteins, can be calculated from the macroscopic formation constants and the microscopic acid-dissociation constants. The acid-base chemistry of Gly-His-Lys is discussed with respect to its recently discovered biological activity.
 ...
PMID:Determination of the microscopic and macroscopic acid dissociation constants of glycyl-L-histidyl-L-lysine and related histidine peptides. 1 68

The effects of opaque-2 corn and the complementation with lupin flour on the sensory quality and nutritive value of "humitas" were evaluated. Moreover, the nutritional and quality changes which occur during the retorting of the product canned in two can sizes, were studied. Hybrid and opaque-2 corn were replaced with 6%, 8%, 10% and 12% lupin flour, being 8% the complementation level with the best sensory and nutritional quality. Heat penetration studies of the product canned in N2 and N6 tin cans, were carried out. Total process time at 121 degrees C was 73 min and 147 min, respectively. "Humitas" prepared with hybrid and opaque-2 corn, with and without 8% lupin flour, prior and after sterilization, were subjected to proximate analysis, pH, titratible acidity and available lysine determinations. Biological evaluation of the protein by the net protein ratio (NPR) and digestibility, as well as organoleptic quality and acceptability analyses were also determined. It was concluded that the complementation with 8% lupin flour improves significantly the nutritional value of hybrid corn "humitas", but not that of opaque-2 corn. The canning process affected lysine availability and was directly related to the amino acid concentration, and to the retorting duration. On the other hand, the thermal processing adversely affected the biological quality of protein and some sensory attributes. The 8% lupin complementation was also detrimental for the organoleptic quality of the product.
 ...
PMID:[Canning of "humitas" prepared with opaque-2 corn, supplemented with sweet lupine (Lupinus albus var. Multolupa). Nutritional and quality changes]. 248 29

The potential contribution of thiolimidate formation to the increased kinetic acidity of the alpha-proton of acetyl-CoA in the carbon-carbon bond forming reaction catalyzed by 3-ketoacyl-CoA thiolase (thiolase I) from porcine heart was assessed by chemical modification and isotope exchange experiments. Thiolase is only partially inactivated after the chemical modification of lysine residues by reductive methylation, pyridoxal phosphate, or o-phthaldehyde (specific for vicinal lysine and cysteine). The thiolase-catalyzed formation of acetyl-CoA from acetoacetyl-CoA and CoASH in 18OH2 is not accompanied by the appearance of 18O in the acetyl-CoA product. These experiments effectively rule out participation of thiolimidate formation in the thiolase reaction. Other mechanisms must be employed to facilitate the abstraction of the alpha-proton of acetyl-CoA by thiolase I.
 ...
PMID:Examination of the role of thiolimidate formation in the cleavage of acetoacetyl-CoA catalyzed by thiolase I from porcine heart. 256 19

The resorbable polymers polyglycolic acid (PGA) and polylactic acid (PLA) are gaining increasing importance in tissue engineering and cell transplantation. The present investigation was focused on the biocompatibility and cell retaining behavior of PGA/poly-L-lactide (PLLA) (90/10) and PLLA nonwoven structures for the in vitro development of chondrocyte-polymer constructs. The effect of the relevant monomers to chondrocytes was analyzed. Type II collagen and poly-L-lysine were compared to improve loading of PGA/PLLA and PLLA polymer nonwovens with chondrocytes. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetra-zoliumbrom ide (MTT) test was applied for quantification. At concentrations above 2 mg/mL, glycolic acid was more cytotoxic than lactic acid. As shown by pH equilibration, the cytotoxic effect is not due merely to the acidity of the alpha-hydroxy acids. Regarding the degradation products, glycolic acid, and L(+) lactic acid, nonwovens of PLLA are more biocompatible with chondrocytes than nonwovens of polyglycolide. Collagen type II and poly-L-lysine generally improved cell seeding on resorbable polymers in tissue engineering; however, their efficiency varies depending on the type of fiber structure.
 ...
PMID:Resorbable polyesters in cartilage engineering: affinity and biocompatibility of polymer fiber structures to chondrocytes. 873 23

Growth of, and acid production by Bifidobacterium lactis and Lactobacillus acidophilus using ovine and caprine milk as media were evaluated for their potential use in cheese-making. A protein hydrolysate (MHP, obtained from incubation of bovine milk with protease) or a mixture of free amino acids (FAA, similar to the amino acid fraction of MHP) was added as a nitrogen enrichment source. Bifidobacterium lactis and Lact. acidophilus were inoculated at 50 ml l-1 and incubated at 37 degrees C with growth supplements added at ratios in the range 25-50 ml l-1. The maximum viable counts of Bif. lactis were lower in plain ovine and caprine milk than in nitrogen-enriched milk, and MHP was a better growth promoter than FAA. A similar trend was observed with the acidity values developed, and attempts to correlate growth with acidity were successfully performed. The highest uptake rates of amino acids in ovine milk were observed for lysine, isoleucine, leucine and proline, but only isoleucine was taken up at a similar rate in caprine milk. Final bacterial viable counts of Lact. acidophilus in the plain and enriched forms of ovine milk did not differ greatly from each other, although FAA was statistically a better growth promoter than MHP. Unlike results in ovine milk, cultures of Lact. acidophilus in caprine milk exhibited drops of 1-1.5 log cycles in viable cell counts by 24 h of fermentation, irrespective of the nature of the nitrogen source. Parallel studies indicated that the excess of fatty acid residues in caprine milk could be responsible for the poor growth of Lact. acidophilus.
 ...
PMID:Use of small ruminants' milk supplemented with available nitrogen as growth media for Bifidobacterium lactis and Lactobacillus acidophilus. 983 Jan 19

Biochemical changes in wheat grains stored at 10, 25 and 45 degrees C for six months were studied. A significant decrease in pH and an increase in titratable acidity was observed during storage of wheat grains at 25 degrees C and 45 degrees C. Moisture contents of wheat grains decreased by 15% at 25 degrees C and 26% at 45 degrees C during six months of storage. A significant decrease in water soluble amylose (20-28%) along with an increase in insoluble amylose contents (7.6-17%) were observed during storage at 25 and 45 degrees C. Amylase activity of the samples showed a decrease as the storage progressed. Total soluble sugars increased by 9% at 10 degrees C and 12% at 25 degrees C; a 37% decrease was observed after six months storage at 45 degrees C. Total available lysine decreased by 18.0% and 22.6% at 25 and 45 degrees C, respectively, after six months storage. In vitro protein digestibility of wheat grains decreased by 5.00% at 25 degrees C and 10.28% at 45 degrees C during six months of storage. However, no significant biochemical changes occurred during storage at 10 degrees C.
 ...
PMID:Biochemical changes in wheat during storage at three temperatures. 1064 58

The effect of storage time on pH, titratable acidity, degrees Brix, organic acids, sugars, amino acids, and color of minimally processed cantaloupe melon (Cucumis melo L. var. reticulatus Naud. cv. Mission) was determined at 4 degrees C and 20 degrees C. Changes in most of the biochemical parameters with storage time were relatively slow at the lower temperature. At 20 degrees C, a 17% loss in soluble solids and a 2-fold increase in acidity occurred after 2 days. Organic acid content also increased considerably with time at this temperature as a result of the production of lactic acid. Oxalic, citric, malic, and succinic acids were the organic acids, and glucose, fructose, and sucrose were the sugars present in the freshly cut cantaloupe. Malic acid concentration decreased concurrently with lactic acid production indicating the possible involvement of anaerobic malo-lactic fermentation along with sugar utilization by lactic acid bacteria. The effect of storage on microbial growth was determined at 4, 10, and 20 degrees C. Gram-negative stained rods grew at a slower rate at 4 degrees C and 10 degrees C than the Gram-positive mesophilic bacteria that dominated microorganism growth at 20 degrees C. Eighteen amino acids were identified in fresh cantaloupe: aspartic acid, glutamic acid, asparagine, serine, glutamine, glycine, histidine, arginine, threonine, alanine, proline, tyrosine, valine, methionine, isoleucine, leucine, phenyl alanine, and lysine. The dominant amino acids were aspartic acid, glutamic acid, arginine, and alanine. Total amino acid content decreased rapidly at 20 degrees C, but only a slight decrease occurred at 4 degrees C after prolonged storage. Changes in lightness (L), chroma, and hue at both temperatures indicate the absence of browning reactions. The results indicate the potential use of lactic acid and lactic acid bacteria as quality control markers in minimally processed fruits.
 ...
PMID:Biochemical and microbial changes during the storage of minimally processed cantaloupe. 1114 Dec 66

Although gastric and intestinal contents from rats failed to show amino acid decarboxylase activity when tested against five different amino acids (glutamic acid, arginine, lysine, tyrosine, and histidine), the feces contained at least seven different amines, some known to be pharmacologically active. Putrescine, histamine, and tyramine were identified by means of paper chromatography in both intestinal material and mixed fecal cultures; four other spots were found, three of which had Rf values similar to agmatine, ethanolamine, and ephedrine. The formation of lysine and glutamic acid decarboxylases was not enhanced by an increased acidity during growth while increased oxygen tension was inhibitory to amino acid decarboxylase synthesis in these fecal cultures. The feeding of chlortetracycline to rats, or its presence at a very low concentration in media in which the mixed cultures were grown, reduced the capacity of intestinal microorganisms to produce amines. Cells from mixed fecal cultures grown in the presence of chlortetracycline lacked or contained but weak amino acid decarboxylase activities. The action of the enzymes themselves was unaffected by the presence of the antibiotic in the Warburg cup during assay. The results suggest that amines formed within the intestinal tract might be toxic to the rat, and that chlortetracycline accelerates animal growth by suppressing their production.
 ...
PMID:Formation of amines by intestinal microorganisms and the influence of chlortetracycline. 1436 75

Covalently linked films of the ferric heme protein myoglobin and poly-L-lysine on pyrolytic graphite electrodes reacted with tert-butylhydroperoxide (tBuOOH) to form ferryloxy protein species according to Michaelis-Menten enzyme kinetics. Rotating disk voltammetry data obtained in microemulsions, micellar solution, and buffers revealed a strong influence of water phase acidity on kinetic parameters. Microemulsion and surfactant type had a much smaller influence on reaction kinetics, possibly because the reaction takes place entirely in a water environment surrounding Mb in the films in all fluids. A large apparent Michaelis kcat in microemulsions with neutral water phases was offset by much weaker binding as shown by larger protein-substrate dissociation constants (Km). Acidic SDS microemulsions and pH 2 buffer provided the most efficient reaction conditions as judged by the ratio kcat/Km. Apparent kinetic constants are most likely governed by acidity-controlled protein conformations and their binding with tBuOOH in the intermediate protein-substrate complex.
 ...
PMID:Enzyme-like kinetics of ferryloxy myoglobin formation in films on electrodes in microemulsions. 1637 48

Previously we improved the neurotensin (NT)-polyplex by the coupling of HA2 fusogenic peptide (FP) and Vp1 SV40 karyophilic peptide (KP). We now report the proportion of [(125)I]-NT, [(3)H]-FP, and poly-l-lysine (PLL) in the NT-polyplex, and some of its biophysical properties. We concluded that the most efficient NT-polyplex comprised 1 NT, 4 FP, and 2 PLL molecules. Electrophoresis revealed that high acidity is detrimental for NT-polyplex stability. Electron microscopy and electrophoresis studies showed that 6 muM KP and 1% serum condensed the plasmid DNA (pDNA) before the appearance of toroid structures. Four plasmids were used to evaluate the transfection efficiency. In vitro, maximum expression was produced at molar ratios (pDNA : [(125)I]-NT-[(3)H]-FP-PLL conjugate) of 1:34 for pEGFP-N1 and 1:27 for pECFP-Nuc. Cotransfection of those plasmids was attained at their optimum molar ratios. In vivo, maximum expression of the pDAT-BDNF-flag in dopamine neurons was produced at a 1:45 molar ratio, whereas that of pDAT-EGFP was at 1:20. The NT-polyplex in the presence of 1 muM SR-48692, an NT-receptor specific antagonist, and untargeted polyplex did not cause transfection in vivo demonstrating the specificity of gene transfer via NT-receptor endocytosis. This information is essential for synthesizing an efficient NT-polyplex that can provide a useful tool for specific gene transfection.
 ...
PMID:Biophysical characteristics of neurotensin polyplex for in vitro and in vivo gene transfection. 1673 Sep 7


1 2 3 4 5 Next >>