Search Results
Results 651 - 700 of 1403
< 9 10 11 12 13 14 15 16 17 18 19 >
Fotsch C - - 1999
On-resin macrocyclization via an SNAr reaction is employed in the synthesis of tocinoic acid analogs. Specifically, an N-terminal nitrofluorobenzene is attacked by a nucleophilic C-terminal sidechain. The remaining nitro group can be reduced and acylated. NMR is used to compare the conformation of the new macrocyclic peptides to tocinoic acid.
Anini Y - - 1999
Endocrine L-cells of the distal intestine synthesize both peptide YY (PYY) and proglucagon-derived peptides (PGDPs), whose release has been reported to be either parallel or selective. Here we compare the release mechanisms of PYY, glucagon-like peptide-1 (GLP-1), and oxyntomodulin-like immunoreactivity (OLI) in vivo. Anaesthetized rats were intraduodenally (ID) given either ...
Glover K J - - 1999
A general procedure for the reliable preparation of large quantities of insoluble transmembrane peptides has been developed. Optimal couplings were obtained during synthesis by using high-temperature couplings in conjunction with O-(7-azabenzotriazol-1-yl)-1,1,3, 3-tetramethyluronium hexafluorophosphate (HATU) activation. Improved purification schemes were developed that use reverse- phase HPLC on a C1 column and ...
Fukumizu A - - 1999
Pseudo-peptide analogs of trans-4-aminomethylcyclohexanecarbonyl-L-phenylalanyl-4-aminopheny l acetic acid (PKSI-527, plasma kallikrein selective inhibitor), in which an amide bond (peptide bond) has been replaced by a CH2-NH bond, i.e., trans-4-aminomethylcyclohexanecarbonyl-L-phenylalanyl-psi (CH2-NH)-4-aminophenyl acetic acid (I), trans-4-aminomethylcyclohexanecarbonyl-psi (CH2-NH)-L-phenylalanyl-4-aminophenyl acetic acid (II) and trans-4-aminomethylcyclohexanecarbonyl-D-phenylalanyl-psi (CH2-NH)-4-aminophenyl acetic acid (III) were synthesized. These pseudo-peptide analogs did not ...
Davis T A - - 1999
The flooding dose method, which is used to measure tissue protein synthesis, assumes equilibration of the isotopic labeling between the aminoacyl-tRNA pool and the tissue and blood free amino acid pools. However, this has not been verified for a phenylalanine tracer in an in vivo study. We determined the specific ...
Di Giulio M - - 1999
We have assumed that the coevolution theory of genetic code origin (Wong JT, Proc Natl Acad Sci USA 72:1909-1912, 1975) is essentially correct. This theory makes it possible to identify at least 10 evolutionary stages through which genetic code organization might have passed prior to reaching its current form. The ...
Schwope Ina - - 1999
Peptide-DNA hybrids are richly functionalized analogues of biomolecules that may have applications as hybridization probes and antisense agents with tunable binding and targeting properties. So far, synthetic efforts have mainly focused on hybrids bearing a single peptide chain, either at the 5'- or the 3'-terminus. Such singly modified analogues are ...
Jakubowski H - - 1999
Lysyl-tRNA synthetase (LysRS), a class II enzyme whose major function is to provide Lys-tRNALys for protein synthesis, also catalyzes aminoacylation of tRNALys with arginine, threonine, methionine, leucine, alanine, serine, and cysteine. The limited selectivity in the tRNA aminoacylation reaction appears to be due to inefficient editing of some amino acids ...
Taillades J - - 1999
Alpha-N-Carbamoyl amino acid (CAA), whose conditions of formation in a prebiotic hydrosphere have been described previously (Taillades et al. 1998), could have been an important intermediate in prebiotic peptide synthesis through reaction with atmospheric NOx. Nitrosation of solid CAA (glycine or valine derivative) by a 4/1 NO/O2 gaseous mixture (1 ...
Szathmáry E - - 1999
The genetic code, understood as the specific assignment of amino acids to nucleotide triplets, might have preceded the existence of translation. Amino acids became utilized as cofactors by ribozymes in a metabolically complex RNA world. Specific charging ribozymes linked amino acids to corresponding RNA handles, which could basepair with different ...
Agathangelou P - - 1999
The endothelins are a family of three potent vasoactive peptides, ET-1, -2 and -3, which comprise 21 amino acids and contain two disulfide bridges between cysteine residues. They were originally isolated from human vascular endothelial cells. Two endothelin receptor subtypes, A and B (ETA and ETB, respectively) have also been ...
Huang Y - - 1999
A method for amino acid sequence and D/L configuration identification of peptides by using fluorogenic Edman reagent 7-[(N, N-dimethylamino)sulfonyl]-2,1,3-benzoxadiazol-4-yl isothiocyanate (DBD-NCS) has been developed. This method was based on the Edman degradation principle with some modifications. A peptide or protein was coupled with DBD-NCS under basic conditions and then cyclized/cleaved ...
Fujita T - - 1999
In a computer modeling of transmembrane domains of human thrombin receptor, Lys-158 was found near the ligand binding site. To capture this basic residue, analogs of peptide ligand containing a series of acidic amino acids were synthesized and assayed for human platelet aggregation, and Ser-(p-F)Phe-Aad(= alphaaminoadipic acid)-Leu-Arg-Asn-Pro-NH2 was found to ...
Illangasekare M - - 1999
RNA 77, derived by selection amplification, accelerates its own conversion to Phe-RNA (relative to randomized RNA) more than 6 x 10(7)-fold, by using amino acid adenylates as substrate. A modified assay system allows measurement of slow rates of aa-RNA formation, which for disfavored amino acid substrates can be more than ...
Falb E - - 1999
This paper reports procedures for the straightforward in situ generation of Fmoc-amino acid chlorides using bis-(trichloromethyl)carbonate (BTC) and their utilization for difficult couplings during solid-phase peptide synthesis. The BTC-mediated coupling of all Fmoc-protected proteinogenic amino acids to a large variety of N-alkylated amino acid-peptidyl-resin was studied. The majority of the ...
Mirgorodskaya E - - 1999
In this study we present a method for determination of O-glycosylation sites in glycopeptides, based on partial vapor-phase acid hydrolysis in combination with mass spectrometric analysis. Pentafluoropropionic acid and hydrochloric acid were used for the hydrolysis of glycosylated peptides. The reaction conditions were optimized for efficient polypeptide backbone cleavages with ...
Wang B - - 1999
In an attempt to improve the membrane permeabilities of opioid peptides, we have synthesized cyclic prodrugs of [Leu5]-enkephalin and DADLE using a coumarinic acid or a phenylpropionic acid linker. The synthesis of the coumarinic acid- and phenylpropionic acid-based cyclic prodrugs followed similar strategies. Key intermediates were the compounds with the ...
Taupin C M - - 1999
The aminoacyl-tRNA synthetases are ubiquitous enzymes which catalyze a crucial step of the cell life, the specific attachment of amino acids to their cognate tRNA. The amino acid sequences of three archaeal seryl-tRNA synthetases (SerRS) from Haloarcula marismortui and Methanococcus jannaschii, both belonging to the group of Euryarchaeota, and from ...
Dinh T D TD Department of Chemistry, University of California, Irvine 92697-2025, - - 1999
In neat trifluoroacetic acid, tryptophan side chains cross-link to form a diastereomeric mixture of tryptophan dimers. Convergent oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) converts tryptophan dimers to ditryptophan. Since cross-link formation is under thermodynamic control, there has been no simple way of controlling the regiochemistry of the cross-linking process when more than ...
Nordin B E - - 1999
The fidelity of protein synthesis requires efficient discrimination of amino acid substrates by aminoacyl-tRNA synthetases. Accurate discrimination of the structurally similar amino acids, valine and isoleucine, by isoleucyl-tRNA synthetase (IleRS) results, in part, from a hydrolytic editing reaction, which prevents misactivated valine from being stably joined to tRNAIle. The editing ...
Stoev S - - 1999
We report the solid-phase synthesis and some pharmacological properties of 23 new analogs of arginine vasopressin (AVP) which have the Phe3 residue replaced by a broad variety of amino acids. Peptides 1-9 have at position 3: (1) the mixed aromatic/aliphatic amino acid thienylalanine (Thi) and the aliphatic amino acids; (2) ...
Ryadnov M G - - 1999
An epimerization-free system for coupling N-protected peptides with free amino acids was developed. A number of inorganic substances were tested as epimerization suppressant additives during the coupling by various methods (carbodiimide plus additives, uronium salts, Woodward's reagent-K, isobutyl-chloroformate, etc.). Some of them (ZnCl2, RbClO4, LiCl, SnCl4, AlCl3, etc.) in combination ...
Nyberg G B - - 1999
Metabolic flux analysis is a useful tool for unraveling relationships between metabolism and cell function. Material balancing can be used to provide estimates of major metabolic pathway fluxes, provided all significant metabolite uptake and production rates are measured. Potential sources of metabolizable material in many serum-free media formulations are low ...
Rival S - - 1999
Pseudomonas aeruginosa elastase was used to synthesize various N-protected dipeptide amides. The identity of the products was confirmed by FAB(+)-MS. After recrystallization, the yield of their synthesis was calculated, their purity was checked by RP-HPLC and their melting point was measured. With regard to the hydrolysis, it is well-established that ...
Onuoha G N - - 1999
Vasoactive intestinal peptide (VIP) is a peptide amide containing 28 amino acids which was first isolated from the intestine and is distributed over the entire body but primarily in the nervous system. It is released in response to the electrical stimulation of nerve fibres, stimulation of the vagus, prostaglandin E1, ...
Iiboshi Y - - 1999
In human T-lymphoblastoid cells, downstream signaling events of mammalian target of rapamycin (mTOR), including the activity of p70(s6k) and phosphorylation of eukaryotic initiation factor 4E-binding protein 1, were dependent on amino acid concentration in the culture media, whereas other growth-related protein kinases were not. Amino acid-induced p70(s6k) activation was completely ...
Yahalom D - - 1999
Transdermal delivery of peptidic drugs is usually inefficient, notably due to their hydrophilic character which makes it difficult to cross the hydrophobic layers of the skin. In order to obtain transdermally deliverable analogs of gonadotropin releasing hormone (GnRH), we have synthesized related hydrophobic derivatives by attaching various aliphatic acids to ...
Bahr U - - 1999
Exact mass determination is performed by electrospray ionization orthogonal time-of-flight mass analysis. For peptides in the mass range of 1200-1500 Da a mass error of < 5 ppm is achieved with internal calibration within a single mass measurement provided peak intensities are high. Peptides containing isobaric amino acids like glutamine ...
Zupkó I - - 1999
A set of oxytocin antagonists consisting of [Mpa1Sar7Arg8]-oxytocin substituted by various conformationally restricted or bulky D amino acids at position 2 were synthetized and biologically tested. In in vivo pharmacological investigations, the effects of these peptides were examined on the spontaneous motor activity of postpartum rat. Three of the newly ...
Hohsaka T - - 1999
A novel method of the in vitro incorporation of two nonnatural amino acids into proteins through extension of the genetic code was developed. The streptavidin mRNA containing AGGU and CGGG, and chemically aminoacylated tRNA(ACCU) and tRNA(CCCG) were prepared, then they were added into E. coli in vitro protein synthesizing system. ...
Kuwahara M - - 1999
Syntheses of N-Fmoc delta-amino acids with an ether linkage in the main chain and six different nucleobases on the side chain, Fmoc-NH-C*H(CH2-CH2-B)-CH2-O-CH2-COOH (B = N6-benzoyladenine, thymine, uracil, N-benzoylcytosine, guanine, and N2-isobutyrylguanine) are described. The delta-amino acids were prepared through 8-12 step synthesis starting from L-homoserine and could be linked together ...
Davis B K - - 1999
Comparative path lengths in amino acid biosynthesis and other molecular indicators of the timing of codon assignment were examined to reconstruct the main stages of code evolution. The codon tree obtained was rooted in the 4 N-fixing amino acids (Asp, Glu, Asn, Gln) and 16 triplets of the NAN set. ...
Falkiewicz B - - 1999
PNAs are relatively novel DNA analogues, intensively studied due to their potential as gene-targeted drugs with antigene and antisense properties. In 1996 we elaborated a new method of synthesis of PNA monomer backbones based on the Mitsunobu reaction with N-tosyl-protected (Tos) amino acid esters as acidic components of the reaction. ...
Romanovskis P - - 1998
Cyclic peptide mixtures represent a promising approach for drug lead discovery. Diversity can be expanded via changes in ring size, amide bond replacements, D- and L-natural and unnatural amino acids, and by the incorporation of beta-turn mimics and related conformational constraints. We expand the scope of our side-chain attachment/resin-bound cyclization ...
Meredith D - - 1998
1. 4-Aminomethylbenzoic acid, a molecule which mimics the special configuration of a dipeptide, competitively inhibits peptide influx in both Xenopus Laevis oocytes expressing rabbit PepT1 and through PepT1 in rat renal brush border membrane vesicles. 2. This molecule is not translocated through PepT1 as measured both by direct HPLC analysis ...
Becker H D - - 1998
Thermus thermophilus possesses an aspartyl-tRNA synthetase (AspRS2) able to aspartylate efficiently tRNAAsp and tRNAAsn. Aspartate mischarged on tRNAAsn then is converted into asparagine by an omega amidase that differs structurally from all known asparagine synthetases. However, aspartate is not misincorporated into proteins because the binding capacity of aminoacylated tRNAAsn to ...
Li Z - - 1998
Incubation of heat-denatured plasma from six species occupying different evolutionary positions within the Sarcopterygian lineage [the dipnoan, Protopterus annectens (African lungfish); the urodele, Amphiuma tridactylum (three-toed amphiuma); the colubrid snakes, Pituophis melanoleucus sayi (bullsnake) and Masticophis flagellum (coachwhip); and the lizards Heloderma suspectum (Gila monster) and Varanus Grayi (Gray's monitor)] ...
Câmpian E - - 1998
Omission libraries, synthesized by omitting one amino acid in all coupling positions, are very efficient tools for the rapid identification of the amino acid components of bioactive peptides. Based on the determined amino acids, an occurrence library can be defined and prepared which is much less complex than the full ...
Davydov O V - - 1998
Up-to-date knowledge is not yet enough to prove or reject completely one of the leading alternative hypotheses considering external or internal origin of the genetic code organization (term "internal" means a peculiarity of amino acids and nucleotides which can propose some logical basis for explanation why definite codons are assigned ...
Goodwin T E - - 1998
Problems were encountered during attempts to prepare N-terminal cysteine-substituted peptide nucleic acids (PNAs) from commercially available, Fmoc-protected monomers. These problems have been surmounted by the use of an S-t-butylmercapto protecting group on the cysteine moiety. The solid-phase syntheses are carried out via a simplified procedure which should be generally useful ...
Agou F - - 1998
The accuracy of protein synthesis essentially rests on aminoacyl-tRNA synthetases that ensure the correct attachment of an amino acid to the cognate tRNA molecule. The selection of the amino acid substrate involves a recognition stage generally followed by a proofreading reaction. Therefore, to change the amino acid specificity of a ...
Atasoglu C - - 1998
The influence of peptides and amino acids on ammonia assimilation and de novo synthesis of amino acids by three predominant noncellulolytic species of ruminal bacteria, Prevotella bryantii B14, Selenomonas ruminantium HD4, and Streptococcus bovis ES1, was determined by growing these bacteria in media containing 15NH4Cl and various additions of pancreatic ...
Caciagli V - - 1998
A preparative method for the preparation of large peptides is described. An advantageous theoretical weight of peptide/weight of starting resin ratio (tPw/Rw) of about 0.3 was successfully experimented. The esterification of the first amino acid was realized with a racemization of less than 1%. The study of the coupling conditions ...
Wolfson A D - - 1998
An improved quantitative assay for tRNA aminoacylation is presented based on charging of a nicked tRNA followed by separation of an aminoacylated 3'-fragment on an acidic denaturing polyacrylamide gel. Kinetic parameters of tRNA aminoacylation by Escherichia coli AlaRS obtained by the new method are in excellent agreement with those measured ...
Turchiello R F - - 1998
Ortho-aminobenzoic acid (o-Abz) has been used as a fluorescent probe in internally quenched fluorescent peptides for continuous protease assays. We investigated the fluorescent properties of the probe in order to verify if it can be used to monitor the interaction of peptides with micelles. Abz-aminoacyl-monomethyl amides (Abz-Xaa-NHCH(3), where Xaa=Arg, Phe, ...
Freist W - - 1998
Yeast aminoacyl-tRNA synthetases act in a multi-step process when recognizing their cognate amino acids; this identification event includes "physical" binding and "chemical" proof-reading steps. However, the various enzymes use these single steps at different degrees, and their specificities with regard to the 20 naturally occurring amino acids deviate considerably from ...
Barnes D - - 1998
We have isolated and characterized the Saccharomyces cerevisiae PTR3 gene by functional complementation of a mutant deficient for amino acid-inducible peptide transport. PTR3 is predicted to encode a protein of 678 amino acids that exhibits no similarity to any other protein in the database. Deletion of the PTR3 open reading ...
Adler M M Neurotoxicology Branch, Pharmacology Division, U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010, - - 1998
The novel inhibitor 7-N-phenylcarbamoylamino-4-chloro-3-propyloxyisocoumarin (ICD 1578) was tested for its ability to antagonize the zinc metalloprotease activity of botulinum toxin B (BoNT/B). The efficacy of this compound was tested in a cell-free system using a 50-mer synaptobrevin peptide as substrate. The peptide, designated as [Pya88] S 39-88, had a fluorescent ...
Karoyan P - - 1998
The asymmetric synthesis of (S)-Boc-N-methyl-p-benzoyl-phenylalanine was performed by alkylation of sultam Boc-sarcosinate. The levorotatory sultam led to (S)-Boc-N-methyl amino acids with high optical purity. This photoreactive amino acid was incorporated into the sequence of a Substance P peptide antagonist. Comparison of the affinity and antagonistic properties of Biotinyl-apa-[D-Pro9, MePhe(pBz)10, Trp11]SP ...
Aldrian-Herrada G - - 1998
A new simple solid-phase method has been developed for synthesizing Boc-protected peptide nucleic acid (PNA) monomers. An immobilized backbone 3 was built on Expansin resin using an ester disulphide handle: 2-hydroxypropyl-dithio-2'-isobutyric acid (HPDI). The base acetic acids of thymine 5, Z-cytosine 9, Z-adenine 12, and 6-O-benzyl guanine 17 were prepared ...
< 9 10 11 12 13 14 15 16 17 18 19 >