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)

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.
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PMID:Determination of the microscopic and macroscopic acid dissociation constants of glycyl-L-histidyl-L-lysine and related histidine peptides. 1 68

We have purified an acidic octapeptide from the neural ganglion of the protochordate Ciona intestinalis by a three-step procedure including C18 Sep-Pak fractionation, MonoQ ion-exchange chromatography, and C4 reversed-phase high-performance liquid chromatography. The purification was monitored by an immunoassay specific for the alpha-carboxyamidated COOH terminus common to the mammalian brain-gut hormones, cholecystokinin and gastrin. Automated Edman degradation revealed the sequence Asn-Tyr-Tyr-Gly-Trp-Met-Asp-Phe. In accordance with the high acidity of the peptide, amino acid analysis after cleavage with aminopeptidase M showed that both tyrosyl residues are sulfated. Hence, the structure is Asn-Tyr(SO3)-Tyr(SO3)-Gly-Trp-Met-Asp-Phe-NH2, as also confirmed by identity with the synthetic disulfated peptide in different chromatographic systems. The occurrence of two consecutively sulfated tyrosyl residues after a neutral residue challenges present concepts of consensus sites for tyrosyl sulfation. We conclude that the structure of the peptide, named cionin, suits that of a common ancestor for cholecystokinin and gastrin.
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PMID:Cionin: a disulfotyrosyl hybrid of cholecystokinin and gastrin from the neural ganglion of the protochordate Ciona intestinalis. 230 39

Factors affecting aspartimide formation, such as protecting groups, acidity, basicity, and temperature, were studied using the model tetrapeptide, Glu-Asp-Gly-Thr. The aspartyl carboxyl side chain in this tetrapeptide was either free or protected as a benzyl or cyclohexyl ester. Our results showed that the cyclohexyl ester led to far less aspartimide formation during acidic or tertiary amine treatment than the corresponding benzyl ester. The rate constants of aspartimide formation in HF-anisole (9:1, v/v) for the tetrapeptide protected as the benzyl ester were found to be 6.2 x 10(-6) and 73.6 x 10(-6) s-1 at -15 degrees and 0 degrees C respectively. These values were about three times faster than the corresponding free- or cyclohexyl ester-protected tetrapeptide. Little difference was seen when the studies were carried out at room temperature. The cyclohexyl protected tetrapeptide gave only 0.3% aspartimide in diisopropylethylamine treatment in 24 h, a 170-fold reduction of imide formation when compared with the benzyl protected tetrapeptide. Thus, using the cyclohexyl ester for aspartyl protection, our studies showed aspartimide formation could be significantly reduced to less than 2% under standard peptide synthesis conditions. Furthermore, with these model peptides, the mechanism of acid catalyzed aspartimide was studied in a range of HF concentrations. In dilute HF cleavage conditions (HF:dimethylsulfide 1:3, v/v), the mechanism was found to be of the AAC2 type, with the rate of aspartimide formation increasing very slowly with increasing acid concentration. In concentrated HF solutions (HF greater than 70% by volume), the rate of aspartimide formation increased rapidly with the increase in acid concentration. However, from model studies, the mechanism of aspartimide formation in concentrated HF was AAC2 rather than AAC1.
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PMID:Mechanisms of aspartimide formation: the effects of protecting groups, acid, base, temperature and time. 298 Jul 81

Acetaldehyde reacted with hemoglobin at neutral pH and 37 degrees C to form adducts that were stable to dialysis and that were not reduced by sodium borohydride. Hemoglobin tetramers having 2, 3, and probably 4 molar eq of bound aldehyde were isolated by cation exchange chromatography. The sites of attachment of the aldehyde were the free amino groups of the N-terminal valine residues of the alpha and beta chains of hemoglobin. Derivatization of the beta chains caused a greater increase in the acidity of the hemoglobin than did derivatization of the alpha chains. Derivatization of the beta chains was also preferred over that of the alpha chains. Acetaldehyde derivatives of the N-terminal octapeptide of hemoglobin S (beta sT-1 peptide), Val-Gly-Gly, and tetraglycine were formed readily, contained 1 M eq of acetaldehyde/mol of peptide, and were not reduced by sodium borohydride. In contrast, Ala-Pro-Gly failed to form a 1:1 adduct with acetaldehyde. 13C NMR analysis of the peptide adducts formed with [1,2-13C]acetaldehyde indicated that tetrahedral diastereomeric derivatives were produced. The 13C chemical shifts of the adducts formed between hemoglobin and [1,2-13C]acetaldehyde were identical to those of the peptide adducts although resonances from the individual diastereomeric adducts at each hemoglobin site could not be resolved. The results cited above as well as other evidence indicate that acetaldehyde reacts with the amino termini of hemoglobin to form stable cyclic imidazolidinone derivatives. An exchange of acetaldehyde residues between peptides was also documented.
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PMID:Reaction of acetaldehyde with hemoglobin. 370 Apr 16

Net transepithelial transport (and cellular accumulation) of the dipeptide glycylsarcosine (Gly-Sar), across the apical membrane of human intestinal Caco-2 epithelia, is driven by a proton gradient (Na(+)-free conditions) and displays saturation kinetics (Km 17.4 +/- 5.1 mM, Vmax of 92.8 +/- 15.6 nmol.cm-2.h-1). Net Gly-Sar transport is associated with the stimulation of an inward short-circuit current (Isc). This dipeptide-stimulated Isc is observed in both Na(+)-containing and Na(+)-free conditions, is stimulated by apical acidity, and displays saturation kinetics (in Na(+)-free media at apical pH 6.0, Km of 13.6 +/- 4.5 mM and a Vmax of 284.1 +/- 39.3 nmol.cm-2.h-1). The maximal capacities of Gly-Sar transport and Isc suggest a dipeptide/proton stoichiometry greater than unity (1:3).
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PMID:Transepithelial dipeptide (glycylsarcosine) transport across epithelial monolayers of human Caco-2 cells is rheogenic. 827 76

The objective of the present experiments was to study some properties of fowl spermatozoa which may play a role in the sperm storage and emptying mechanism of the uterovaginal sperm storage tubules (SST) of the hen. The effects exerted by different amino acids (aspartic acid, Asp; glutamic acid, Glu; gamma-aminobutyric acid, GABA; glycine, Gly) and by the pH of the environment at 24 and 39 degrees C on the motility and agglutination of cock spermatozoa were studied in vitro. The spermatozoa did not show agglutination in the presence of Asp and Glu, and became immobilised if the concentration of Glu or the acidity of the environment was increased. In neutral solutions of GABA and Gly or in a faintly alkaline solution characteristic plait-like conglomerations could be seen. The motility of spermatozoa immobilised by Glu could be restored in a varying degree by the addition of GABA or Gly. At a temperature of 24 degrees C, the spermatozoa became immobilised in a medium of pH 6.0 while showed maximum motility at pH 7.1. At 39 degrees C, the spermatozoa were immobilised at higher pH (6.2) and required a pH value as high as 7.4-7.5 to show the highest motility. Spermatozoa inactivated in an acidic solution could be immediately mobilised by alkalisation of the medium, irrespective of the Ca2+ content of the solution. Thus, Ca2+ was not found to play a role in the reactivation of spermatozoa. Nevertheless, marked differences were observed in the maintenance of sperm motility between solutions either containing or lacking Ca2+. As the concentration changes of the above-mentioned amino acids and the pH changes were found to affect the motility and agglutination of spermatozoa in vitro, they may influence also the regulatory mechanism of the uterovaginal SST during the egg-formation cycle in vivo.
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PMID:Motility and agglutination of fowl spermatozoa in media of different amino acid content and pH value in vitro. 890 46

Several clones containing DMP1 cDNA were isolated from a caiman tooth library by screening with a platypus DMP1 probe. The caiman DMP1 shows little amino acid sequence similarity to mammalian DMP1s for much of its length. A few highly conserved regions can, however, be identified that correspond to the slowly evolving parts of the corresponding mammalian genes. Southern blot analysis using probes comprising either conserved regions or longer segments of the gene indicates that only a single DMP1 locus exists. In coding regions, exon-intron boundaries and reading frames are shared by caiman and mammalian genes with the exception of exons 1 and 5, which are longer in the caiman. The repetitive sequence of the last exon is shared by mammals and caiman as are the high Ser content and acidity due to a high proportion of Asp and Glu residues. The conserved mammalian cell-attachment signal Arg-Gly-Asp is absent in the caiman DMP1. In contrast to the amelogenin gene, the DMP1 gene appears to evolve rapidly in vertebrates.
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PMID:Characterization of dentin matrix protein 1 gene in crocodilia. 1039 3

Effects on soil quality and crop establishment after incorporation of flue gas desulfurization by-product (FGD) into soil as an amendment was assessed in a mesocosm study. Mesocosm units received applications equivalent to 0, 2.5, 5.0, 7.5, and 10% FGD residue [0, 25, 50, 75, and 100 tons acre(-1)]. Germination, biomass production, and elemental composition of corn (Zea mays L. var. Dekalb DK-683), soybean [Glycine max (L.) Merr. var. Haskell Pupa 94], radish (Raphanus sativus L. var. Sparkler), and cotton (Gossypius hirsutus L. var. Deltapine 51) were determined. The quality of leachates and soil were also determined periodically. Flue gas desulfurization residue did not affect germination and all application rates stimulated aboveground biomass. Plants grown in FGD-amended soil contained significantly elevated tissue concentrations of As, B, Se, and Mo. The FGD residue elevated surface soil pH from 5.5 (Control) to 8.1 (at 10% FGD). Leachate pH was unaffected by FGD, but salinity rose sharply with increasing application rates of FGD. Leachates contained higher concentrations of B, with small increases in Se and As. Flue gas desulfurization residue application caused an increase in total B, As, Mo, Se, and extractable Ca in the soil, but decreased Mn and Zn. Using FGD residues could have beneficial effects on crop establishment without detrimental effects on soil or leachate quality, at an optimum rate of approximately 2.5%. This material could alleviate surface acidity, and B and Mo deficiencies in plants.
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PMID:Effect of flue gas desulfurization residue on plant establishment and soil and leachate quality. 1140 Dec 55

The rate of spontaneous degradations of asparagine and aspartyl residues occurring through succinimide intermediates is dependent upon the nature of the residue on the carboxyl side in peptides. For nonglycine residues, we show here that this effect can largely be attributed to the electrostatic/inductive effect of the side chain group on the equilibrium concentration of the anionic form of the peptide bond nitrogen atom that initiates the succinimide forming reaction. However, the rate of degradation of Asn-Gly and Asp-Gly containing peptides is about an order of magnitude greater than predicted solely using this explanation. To understand the nature of the glycine effect, ab initio calculations were performed on model compounds. These calculations indicate that there is little to no change in the stability of the transition state or the tetrahedral intermediate of succinimide formation with Asn-/Asp-Gly and Asn-/Asp-Ala derivatives. However, we have found that the acidity of the backbone peptide nitrogen NH is highly dependent upon the conformation of the molecule. Since glycine residues lack the beta-carbon common to all other protein amino acids, these residues can sample additional regions of conformational space where it is possible to further stabilize the backbone amide anion and thus increase the rate of degradation. These results provide the first rationale for the particular rate enhancement of degradation in peptidyl Asn-/Asp-Gly sequences. The results also can be applied to asparagine and aspartyl residues in proteins where the 3-dimensional structure provides additional constraints on conformation that can either increase or decrease the equilibrium concentration of the backbone amide anion and thus their rate of degradation via succinimide intermediates. Understanding this chemistry will assist attempts to minimize the deleterious effect of aging at the molecular level. The relationship between these results and proton exchange experiments is discussed in the Appendix.
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PMID:Neighboring side chain effects on asparaginyl and aspartyl degradation: an ab initio study of the relationship between peptide conformation and backbone NH acidity. 1147 22

A portable system of hydroponic culture was developed that maintained temperature, pH, and nutrient concentrations of circulating nutrient solutions. The hydroponic system is used within a controlled-environment room (CER) for control of aerial environment. The CER was equipped with an auto-calibrating system for atmospheric CO2 control. The control systems for the hydroponic chambers were able to maintain acidity within +/- 0.2 pH units and the temperature with +/- 0.5 degree C. Mixing time for the 200-liter volume of solution within a hydroponic chamber was less than 12 min. The CO2 control system was able to maintain aerial concentrations within +/- 10 ppm CO2 during the light period. The only gradient found to occur within the hydroponic chambers or CER was a slight gradient in aerial temperature along the length of hydroponic chambers. Growth of soybeans [Glycine max (L.) Merr.] was characterized during a 3-week period of vegetative development by leaf number and area, plant dry weight, total N content of plants, and N depletion from the nutrient solution. The growth characteristics among populations for three hydroponic chambers within the CER were not significantly different, and the percent standard errors of means of the measurements within populations from each chamber were nearly all less than 10%. Thus, the uniformity of plant growth reflected the uniformity of environmental conditions.
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PMID:Uniformity of environmental conditions and plant growth in a hydroponic culture system for use in a growth room with aerial CO2 control. 1153 44


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