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Acid Interactions (acid + interaction)
Selected AbstractsPharmacoepidemiologic investigation of a clonazepam-valproic acid interaction by mixed effect modeling using routine clinical pharmacokinetic data in Japanese patientsJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 6 2003E. Yukawa Summary Non-linear Mixed Effects Modeling (NONMEM) was used to estimate the effects of clonazepam,valproic acid interaction on clearance values using 576 serum levels collected from 317 pediatric and adult epileptic patients (age range, 0·3,32·6 years) during their clinical routine care. Patients received the administration of clonazepam and/or valproic acid. The final model describing clonazepam clearance was CL = 144·0 TBW,0·172 1·14VPA, where CL is total body clearance (mL/kg/h); TBW is total body weight (kg); VPA = 1 for concomitant administration of valproic acid and VPA = zero otherwise. The final model describing valproic acid clearance was CL (mL/kg/h) = 17·2 TBW,0·264 DOSE0·159 0·821CZP 0·896GEN, where DOSE is the daily dose of valproic acid (mg/kg/day); CZP = 1 for concomitant administration of clonazepam and CZP = zero otherwise; GEN = 1 for female and GEN = zero otherwise. Concomitant administration of clonazepam and valproic acid resulted in a 14% increase in clonazepam clearance, and a 17·9% decrease in valproic acid clearance. [source] Catalytic effect of dissolved humic acids on the chemical degradation of phenylurea herbicidesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 7 2008Stefano Salvestrini Abstract BACKGROUND: Although biodegradation seems to be the main cause of herbicide degradation, abiotic degradation can also be important for chemicals such as phenylureas, which are subject to catalysed soil reactions. The aim of this work is to investigate the effect of dissolved humic acids (HAs), normally present in natural waters, on the hydrolysis of phenylurea herbicides, and it presents a kinetic model that takes into account the role of adsorption. RESULTS: The linearity of the adsorption isotherms indicates that phenylurea,humic acid interaction can be considered in terms of a repartition-like equilibrium of phenylurea between water and HAs. Kinetic experiments show that the degradation rates of phenylureas increase with HA concentration. CONCLUSION: The kinetic equation adopted adequately describes the experimental data trend, allowing the evaluation of the catalytic effect of HAs on the chemical degradation of phenylureas. Carboxyl groups of HAs seem to play a leading role in the catalysis. The kinetic equation derived in this work could be helpful in predicting the persistence of phenylureas and of related compounds in natural water. Copyright © 2008 Society of Chemical Industry [source] Minerals and phytic acid interactions: is it a real problem for human nutrition?INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2002H. Walter Lopez Summary Because of its high density of negatively charged phosphate groups, phytic acid (PA) forms very stable complexes with mineral ions rendering them unavailable for intestinal uptake. Indeed, the first step in mineral absorption requires that the mineral remains in the ionic state. As the PA content of the diet increases, the intestinal absorption of zinc, iron and calcium decreases. The inhibitory effects of PA on magnesium or copper are more controversial. Nevertheless, PA does not occur alone in foods and is often consumed with various compounds. Phytates are always present in vegetal matrix composed of fibres, minerals, trace elements and other phytomicronutrients. Thus, in order to evaluate mineral absorption from phytate-rich products, all components of diet and food interactions should be considered and it is hard to predict mineral bioavailability in such products by using only the phytate content. [source] Lipid,nucleic acids interactions as base for organization and expression of cellular genomeINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2010V. V. Kuvichkin Abstract Although lipid,nucleic acid interactions have been studied, with certain or little progress, for more than 30 years, it is only in recent years that the problem has received particular attention. It should, however, be noted that most studies deal with DNA-cationic surfactants interactions, whereas DNA-zwitterionic interactions, which are more complex and close to nature, are poorly investigated. The long-standing studies of the triple complexes: DNA,phosphatidylcholine liposomes,divalent metal cations allow us to confirm that these complexes are responsible for the formation of not only the structures existing in DNA,cationic liposome complexes but also some other cellular structures. The author proposed hypothesis about the involvement of direct DNA,lipid interactions in the nuclear pore assembly. Only taking into account interactions between DNA and lipids of cellular membrane, one can explain the origin of such structures as nucleoid, nuclear pore, and nuclear matrix. The formation of triple complexes was accompanied by the aggregation and partial fusion of liposomes as was shown by cryo-TEM technique. The author has presented new data on the structure of triple complexes, which were obtained by phase contrast cryo-TEM. Biophysical data on the liposomes fusion during triple complex formation and perspective of their computer simulation are also presented. DNA acts as a fusogen in this process and it unwinds in the region of liposomes fusion. The nuclear envelope and pore complexes assembly is provided by membrane vesicles fusion. Author has proposed that the DNA-induced fusion of zwitterionic liposomes in vitro may suggest the involvement of direct lipids,DNA interaction in nuclear envelope assembly. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Theoretical study of interactions between cysteine and perfluoropropanoic acid in gas and aqueous phaseINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2009Tiffani M. Holmes Abstract The interaction of perfluoropropanoic acid (PFPA) with the amino acid cysteine was investigated using density functional theory. Previous studies suggest that the peroxisome proliferator chemical, perfluorooctanoic acid, is circulated throughout the body by way of sulfur-containing amino acids. We present conformational analysis of the interactions of PFPA, a small model of perfluorooctanoic acid, with the sulfur-containing amino acid which occur by the process of hydrogen bonding, in which the hydrogen of the sulfhydryl group interacts with the carboxyl oxygen, and the amino nitrogen forms a hydrogen bond with the hydrogen of the OH group of the fluorinated alkyl. We also show in our structures a recently characterized weak nonbonded interaction between divalent sulfur and a main chain carboxyl oxygen in proteins. B3LYP calculated free energies and interaction energies predict low-energy, high-interaction conformations for complex systems of perfluorinated fatty acid interactions with cysteine. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Efficient synthesis and comparative studies of the arginine and N,,N, -dimethylarginine forms of the human nucleolin glycine/arginine rich domainJOURNAL OF PEPTIDE SCIENCE, Issue 1 2005Dr Sotir Zahariev Abstract The Gly- and Arg-rich C -terminal region of human nucleolin is a 61-residue long domain involved in a number of protein,protein and protein,nucleic acid interactions. This domain contains 10 aDma residues in the form of aDma-GG repeats interspersed with Phe residues. The exact role of Arg dimethylation is not known, partly because of the lack of efficient synthetic methods. This work describes an effective synthetic strategy, generally applicable to long RGG peptides, based on side-chain protected aDma and backbone protected dipeptide Fmoc-Gly-(Dmob)Gly-OH. This strategy allowed us to synthesize both the unmodified (N61Arg) and the dimethylated (N61aDma) peptides with high yield (,26%) and purity. As detected by NMR spectroscopy, N61Arg does not possess any stable secondary or tertiary structure in solution and N,,N, -dimethylation of the guanidino group does not alter the overall conformational propensity of this peptide. While both peptides bind single-stranded nucleic acids with similar affinities (Kd = 1.5 × 10,7M), they exhibit a different behaviour in ssDNA affinity chromatography consistent with the difference in pKa values. It has been previously shown that N61Arg inhibits HIV infection at the stage of HIV attachment to cells. This study demonstrates that Arg-dimethylated C -terminal domain lacks any inhibition activity, raising the question of whether nucleolin expressed on the cell-surface is indeed dimethylated. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source] Energetics of galactose, and glucose,aromatic amino acid interactions: Implications for binding in galactose-specific proteinsPROTEIN SCIENCE, Issue 9 2004Mannargudi S. Sujatha Abstract An aromatic amino acid is present in the binding site of a number of sugar binding proteins. The interaction of the saccharide with the aromatic residue is determined by their relative position as well as orientation. The position-orientation of the saccharide relative to the aromatic residue was found to vary in different sugar-binding proteins. In the present study, interaction energies of the complexes of galactose (Gal) and of glucose (Glc) with aromatic residue analogs have been calculated by ab initio density functional (U-B3LYP/ 6-31G**) theory. The position-orientations of the saccharide with respect to the aromatic residue observed in various Gal-, Glc-, and mannose,protein complexes were chosen for the interaction energy calculations. The results of these calculations show that galactose can interact with the aromatic residue with similar interaction energies in a number of position-orientations. The interaction energy of Gal,aromatic residue analog complex in position-orientations observed for the bound saccharide in Glc/Man,protein complexes is comparable to the Glc,aromatic residue analog complex in the same position-orientation. In contrast, there is a large variation in interaction energies of complexes of Glc- and of Gal- with the aromatic residue analog in position-orientations observed in Gal,protein complexes. Furthermore, the conformation wherein the O6 atom is away from the aromatic residue is preferred for the exocyclic ,CH2OH group in Gal,aromatic residue analog complexes. The implications of these results for saccharide binding in Gal-specific proteins and the possible role of the aromatic amino acid to ensure proper positioning and orientation of galactose in the binding site have been discussed. [source] A sensitive two-color electrophoretic mobility shift assay for detecting both nucleic acids and protein in gelsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 7 2003Debra Jing Abstract DNA-binding proteins are key to the regulation and control of gene expression, replication and recombination. The electrophoretic mobility shift assay (or gel shift assay) is considered an essential tool in modern molecular biology for the study of protein-nucleic acid interactions. As typically implemented, however, the technique suffers from a number of shortcomings, including the handling of hazardous 32P-labeled DNA probes, and difficulty in quantifying the amount of DNA and especially the amount of protein in the gel. A new detection method for mobility-shift assays is described that represents a significant improvement over existing techniques. The assay is fast, simple, does not require the use of radioisotopes and allows independent quantitative determination of: (i) free nucleic acid, (ii) bound nucleic acid, (iii) bound protein, and (iv) free protein. Nucleic acids are detected with SYBR® Green EMSA dye, while proteins are subsequently detected with SYPRO® Ruby EMSA dye. All fluorescence staining steps are performed after the entire gel-shift experiment is completed, so there is no need to prelabel either the DNA or the protein and no possibility of the fluorescent reagents interfering with the protein-nucleic acid interactions. The ability to independently quantify each molecular species allows more rigorous data analysis methods to be applied, especially with respect to the mass of protein bound per nucleic acid. [source] Nucleotide,amino acid interactions in the l -His,IMP·MeOH·H2O complexACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010Katarzyna, lepokura In the crystal structure of the methanol-solvated monohydrated complex of l -histidine (His) with inosine 5,-monophosphate (IMP), namely l -histidinium inosine-5,-phosphate methanol solvate monohydrate, C6H10N3O2+·C10H12N4O8P,·CH3OH·H2O, most of the interactions between IMP anions (anti/C3,- endo/gauche,gauche conformers) are realized between the riboses and hypoxanthine bases in a trans sugar-edge/sugar-edge geometry, and between the phosphate groups. The base Watson,Crick edge is involved in additional methanol-mediated IMP...MeOH...IMP contacts. Specific and nonspecific nucleotide,amino acid (IMP...His) interactions engage the Hoogsteen edges of the base and phosphate group, respectively. Additional stabilization of His...IMP contacts is provided by ,,, stacking between the imidazolium ring of His and the hypoxanthine base of IMP. The results may indicate the possible recognition mechanism between His and IMP. [source] Thermodynamic Analysis of Receptors Based on Guanidinium/Boronic Acid Groups for the Complexation of Carboxylates, ,-Hydroxycarboxylates, and Diols: Driving Force for Binding and CooperativityCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2004Sheryl L. Wiskur Dr. Abstract The thermodynamics of guanidinium and boronic acid interactions with carboxylates, ,-hydroxycarboxylates, and diols were studied by determination of the binding constants of a variety of different guests to four different hosts (7,10). Each host contains a different combination of guanidinium groups and boronic acids. The guests included molecules with carboxylate and/or diol moieties, such as citrate, tartrate, and fructose, among others. The Gibbs free energies of binding were determined by UV/Vis absorption spectroscopy, by use of indicator displacement assays. The receptor based on three guanidinium groups (7) was selective for the tricarboxylate guest. The receptors that incorporated boronic acids (8,10) had higher affinities for guests that included ,-hydroxycarboxylate and catechol moieties over guests containing only carboxylates or alkanediols. Isothermal titration calorimetry revealed the enthalpic and entropic contributions to the Gibbs free energies of binding. The binding of citrate and tartrate was investigated with hosts 7,10, for which all the binding events were exothermic, with positive entropy. Because of the selectivity of hosts 8,10, a simple boronic acid (14) was also investigated and determined to be selective for ,-hydroxycarboxylates and catechols over amino acids and alkanediols. Further, the cooperativity of 8 and 9 in binding tartrate was also investigated, revealing little or no cooperativity with 8, but negative cooperativity with 9. A linear entropy/enthalpy compensation relationship for all the hosts 7,10, 14, and the carboxylate-/diol-containing guests was also obtained. This relationship indicates that increasing enthalpy of binding is offset by similar losses in entropy for molecular recognition involving guanidinium and boronic acid groups. [source] Lipid,nucleic acids interactions as base for organization and expression of cellular genomeINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2010V. V. Kuvichkin Abstract Although lipid,nucleic acid interactions have been studied, with certain or little progress, for more than 30 years, it is only in recent years that the problem has received particular attention. It should, however, be noted that most studies deal with DNA-cationic surfactants interactions, whereas DNA-zwitterionic interactions, which are more complex and close to nature, are poorly investigated. The long-standing studies of the triple complexes: DNA,phosphatidylcholine liposomes,divalent metal cations allow us to confirm that these complexes are responsible for the formation of not only the structures existing in DNA,cationic liposome complexes but also some other cellular structures. The author proposed hypothesis about the involvement of direct DNA,lipid interactions in the nuclear pore assembly. Only taking into account interactions between DNA and lipids of cellular membrane, one can explain the origin of such structures as nucleoid, nuclear pore, and nuclear matrix. The formation of triple complexes was accompanied by the aggregation and partial fusion of liposomes as was shown by cryo-TEM technique. The author has presented new data on the structure of triple complexes, which were obtained by phase contrast cryo-TEM. Biophysical data on the liposomes fusion during triple complex formation and perspective of their computer simulation are also presented. DNA acts as a fusogen in this process and it unwinds in the region of liposomes fusion. The nuclear envelope and pore complexes assembly is provided by membrane vesicles fusion. Author has proposed that the DNA-induced fusion of zwitterionic liposomes in vitro may suggest the involvement of direct lipids,DNA interaction in nuclear envelope assembly. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] | ||||||||||