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Acid O (acid + o)
Selected AbstractsDeamidation of labile asparagine residues in the autoregulatory sequence of human phenylalanine hydroxylaseFEBS JOURNAL, Issue 5 2003Structural, functional implications Two dimensional electrophoresis has revealed a microheterogeneity in the recombinant human phenylalanine hydroxylase (hPAH) protomer, that is the result of spontaneous nonenzymatic deamidations of labile asparagine (Asn) residues [Solstad, T. and Flatmark, T. (2000) Eur. J. Biochem.267, 6302,6310]. Using of a computer algorithm, the relative deamidation rates of all Asn residues in hPAH have been predicted, and we here verify that Asn32, followed by a glycine residue, as well as Asn28 and Asn30 in a loop region of the N-terminal autoregulatory sequence (residues 19,33) of wt-hPAH, are among the susceptible residues. First, on MALDI-TOF mass spectrometry of the 24 h expressed enzyme, the E. coli 28-residue peptide, L15,K42 (containing three Asn residues), was recovered with four monoisotopic mass numbers (i.e., m/z of 3106.455, 3107.470, 3108.474 and 3109.476, of decreasing intensity) that differed by 1 Da. Secondly, by reverse-phase chromatography, isoaspartyl (isoAsp) was demonstrated in this 28-residue peptide by its methylation by protein- l -isoaspartic acid O -methyltransferase (PIMT; EC 2.1.1.77). Thirdly, on incubation at pH 7.0 and 37 °C of the phosphorylated form (at Ser16) of this 28-residue peptide, a time-dependent mobility shift from tR,,34 min to ,,31 min (i.e., to a more hydrophilic position) was observed on reverse-phase chromatography, and the recovery of the tR,,34 min species decreased with a biphasic time-course with t0.5 -values of 1.9 and 6.2 days. The fastest rate is compatible with the rate determined for the sequence-controlled deamidation of Asn32 (in a pentapeptide without 3D structural interference), i.e., a deamidation half-time of ,,1.5 days in 150 mm Tris/HCl, pH 7.0 at 37 °C. Asn32 is located in a cluster of three Asn residues (Asn28, Asn30 and Asn32) of a loop structure stabilized by a hydrogen-bond network. Deamidation of Asn32 introduces a negative charge and a partial ,-isomerization (isoAsp), which is predicted to result in a change in the backbone conformation of the loop structure and a repositioning of the autoregulatory sequence and thus affect its regulatory properties. The functional implications of this deamidation was further studied by site-directed mutagenesis, and the mutant form (Asn32,Asp) revealed a 1.7-fold increase in the catalytic efficiency, an increased affinity and positive cooperativity of L-Phe binding as well as substrate inhibition. [source] An efficient O -dealkylation procedure for the synthesis of (3as,cis)-1,2,3,3a,8,8a-hexahydro-1,3a,8-trimethylpyrrolo[2,3- b]indol-5-yl-3,4-dihydro-2(1H)-isoquinolinecarboxylateJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2000Zhongli Gao The title compound is synthesized in high yields and purity from (-)-eserethole (2a) via a lithium bromide catalyzed hydrobromic acid O -dealkylation procedure as the key step. [source] Transferable intermolecular potentials for carboxylic acids and their phase behaviorAICHE JOURNAL, Issue 2 2010Amir Vahid Abstract Transferable step potentials are characterized for 39 carboxylic acids. The reference potential is treated with discontinuous molecular dynamics, including detailed molecular structure. Thermodynamic perturbation theory is used to interpret the simulation results and to provide an efficient basis for molecular modeling and characterization of the attractive forces. Four steps are used for representation of the attractive forces with only the first and last steps varied independently. The two middle steps are interpolated such that each site type is characterized by three parameters: the diameter, ,, the depth of the inner well, ,1, and the depth of the outer well, ,4. The depths of the attractive wells are optimized to fit experimental vapor pressure and liquid density data. Generally, the vapor pressure is correlated to an overall 43% average absolute deviation (% AAD) and the liquid density to 5% AAD. The deviations tend to be largest for the higher molecular weight acids. These deviations are larger than the errors previously encountered in characterizing organic compounds, but carboxylic acids present exceptional challenges owing to their peculiar dimerization behavior. Simultaneous correlation of vapor pressure, vapor compressibility factor, and phase equilibria of water + carboxylic acids place several constraints on the nature of the potential model, with the parameters of the present model representing a reasonable tradeoff. In other words, our model represents minimal deviations for vapor pressure, vapor compressibility factor, and phase equilibria of all acids simultaneously while varying the parameters ,, ,1, ,4, ,CC(dimerizing site bonding energy), ,AD(acceptor-donor bonding energy), and KHB(hydrogen bonding volume) for the acid O and OH site types. The present model is characterized by one acceptor and one dimerizing site on the carbonyl oxygen and one acceptor and one donor site on the hydroxyl oxygen. The acceptor and donor are capable of interacting with water while the dimerizing site is not. With this model, the saturated vapor compressibility factor of acids with seven or fewer carbons is near 0.5 while higher carbon ratios lead to a compressibility factor approaching 1.0. To compensate for the high vapor pressure deviations of the transferable potential model, a correction is introduced to customize the molecule-molecule self interaction energy. This adaptation results in deviations of 3.1% for vapor pressure of the pure acid database. To validate the behavior of the model for carboxylic acids in mixtures, 33 binary solutions were considered. Acids in this database ranged from formic to hexadecanoic. The average absolute deviation in bubble pressure for aqueous acid systems is 4.4%, 10.5% for acid + acid systems, and 4.7% for acid + n-alkane systems without a customized interaction correction. When applying the correction, deviations were 2.4% for aqueous systems, 2% for acid systems, and 2.8% for acid + n-alkane systems. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Putative-farnesoic acid O -methyltransferase (FAMeT) in medfly reproductionARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2010Laura Vannini Abstract A gene potentially involved in juvenile hormone (JH) biosynthesis was previously identified in Ceratitis capitata as the putative- farnesoic acid O-methyltransferase (FAMeT). Since JH is involved in insect reproduction, we silenced the putative-FAMeT expression by RNA interference in Ceratitis capitata to evaluate its implication in egg production. FAMeT gene expression was knocked down in females and males after eclosion and in 1- and 2-day-old females. Treated specimens were left to mate with each other or with untreated partners to evaluate the extent of each sex influencing egg production. Gene silencing was investigated by Real-Time PCR. Results unambiguously showed that FAMeT has a measurable role on the fertility of both medfly sexes. © 2010 Wiley Periodicals, Inc. [source] The putative-farnesoic acid O -methyl transferase (FAMeT) gene of Ceratitis capitata: characterization and pre-imaginal life expressionARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2010Laura Vannini Abstract Farnesoic acid O -methyl transferase (FAMeT) is the enzyme involved in the penultimate step of insect juvenile hormone (JH) biosynthesis and is thus a key regulator in insect development and reproduction. We report the characterization of the putative- FAMeT in the medfly or Mediterranean fruit fly, Ceratitis capitata. This gene was identified by suppressive subtractive hybridization and completely sequenced by the screening of a medfly cDNA library. The obtained sequence was analyzed for conserved protein domain identification and its expression profile was evaluated by quantitative Real-Time PCR in medfly pre-imaginal life. The tissue expression of the isolated gene was verified by in situ hybridization on third instar larvae sections. The characterization of the isolated gene pointed out several typical features of methyl transferase genes. The pre-imaginal putative- FAMeT expression levels were consistent with JH titer change in Diptera. As recognized in some crustaceans, this gene seems to be widely expressed in the medfly as well. Ceratitis capitata is one of the most relevant agricultural pests against which insecticides and the sterile insect technique (SIT) are extensively used in spite of the well-known limitations of these approaches. Although results are not conclusive for the physiological role of the isolated gene, they suggest the characterization of a new gene in the Mediterranean fruit fly potentially involved in JH biosynthesis and may, therefore, have implications for pest control. © 2010 Wiley Periodicals, Inc. [source] | ||||||||||