Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: HUMANGGP:018016 (TFA)
 1,480 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The synthon for O-thiophosphotyrosine, Fmoc-Tyr[PS(OBzl)2]-OH (1c), was prepared in 63% yield from Fmoc-Tyr-OH by first transient protection as the tBuMe2Si-ester and phosphinylation with (BzlO)2PNiPr2/tetrazole followed by oxidation of P(III) to P(V) with S8 in CS2. Building block 1c was incorporated in the Fmoc solid-phase synthesis of two O-thiophosphotyrosine-containing peptides H-Thr-Glu-Pro-Gln-Tyr(PS)-Gln-Pro-Gly-Glu-OH (2) and H-Thr-Arg-Asp-Ile-Tyr(PS)-Glu-Thr-Asp-Phe-Phe-Arg-Lys-OH (3), corresponding to sequences of the p60src (523-531) protein and an insulin receptor (IR) (1142-1153) analogue, respectively. An alternative approach of synthesis, the global phosphorylation of a resin-bound peptide, also proved useful. Thus, the free tyrosyl side-chain containing-peptide IR (1142-1153) on support was phosphinylated with the above phosphoramidite reagent followed by oxidation with either S8/CS2 or tetraethylthiuram disulfide/CH3CN solutions. Deprotection and peptide-resin cleavage was performed with a TFA/thiophenol (H2O) mixture. Crude peptides 2 and 3 were stable to the acidolytic deprotection. Preparative RP(C18)HPLC was initially performed using 0.1% TFA(aq)/EtOH solvents. However, analyses of fractions resulting from the purification step indicated significant decomposition of thiophosphopeptide in solution. Stability measurements both as a function of time and pH, further confirmed this initial finding. Purifications performed at intermediate pH using a triethylammonium acetate (pH 7.5)/CH3CN solvent system overcame this problem.
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PMID:Chemical synthesis of O-thiophosphotyrosyl peptides. 820 Jul 32

Cionin, a protochordate-derived octapeptide amide related to the gastrin/cholecystokinin family of peptides, contains two consecutive tyrosine sulfate residues. In order to gain insight into the role of the respective tyrosine sulfate residue in biological activity, cionin and its derivatives in which one of the two tyrosine sulfate residues was replaced by tyrosine, were prepared by two Fmoc-based solid-phase approaches. In approach (1) Fmoc-Tyr(SO3Na)-OH was employed as a building block to assemble the Tyr(SO3Na)-containing peptide-resin, and a global deprotection/cleavage was conducted with 90% aqueous TFA in the presence of m-cresol and 2-methylindole at 4 degrees C. In approach (2) the Tyr(Msib) [Msib = p-(methylsulfinyl)benzyl] derivative was used for the peptide-chain assembly to achieve sulfation on the selective Tyr residue. Partially protected peptide with the Msib/Msz protecting groups [Msz = p-(methylsulfinyl)benzyloxycarbonyl], obtained after peptide-resin cleavage, was treated with DMF-SO3 complex in the presence of ethanedithiol to achieve the sulfation of free Tyr residue and the reduction of the Msib/Msz groups to TFA-labile Mtb/Mtz groups [Mtb = p-(methylthio)benzyl, Mtz = p-(methylthio)benzyloxycarbonyl]. Final deprotection of the Mtb/Mtz groups with 90% aqueous TFA in the presence of m-cresol and 2-methylindole gave the desired cionin derivative, which contains the tyrosine sulfate residue at the selective position. Yields obtained with approach (2) were considerably higher than those obtained with approach (1). Cionin and mono-Tyr(SO3H)-containing derivatives were assayed on exocrine pancreas in dogs.
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PMID:Solid-phase synthesis of cionin, a protochordate-derived octapeptide related to the gastrin/cholecystokinin family of peptides, and its mono-tyrosine-sulfate-containing derivatives. 820 Jul 39

The acetamidomethyl (Acm) group is a widely used protecting group for the thiol of cysteine during the SPPS process. We prepared the amino terminal loop of the snake alpha-neurotoxin, [Cys3,Cys23, Ser17](1-24) amide, from the linear peptide [Cys(Acm)3,23,Ser17](1-24) amide obtained by SPPS. Three different methods of deprotection of Cys(Acm) and disulfide bond formation were used: iodine, thallium(III) trifluoroacetate and mercuric acetate/potassium ferricyanide. The iodine method failed to yield the expected peptide, and gave instead the mono-iodinated tyrosine analog. The disulfide cyclized peptide obtained by thallium (III) or Hg(II) procedures displayed a MW value observed by mass spectrometry that was higher than the calculated value. The difference (MWobs-MWcalc) corresponded to a multiple of the Acm moiety, which is shifted intra- and/or intermoleculary. Furthermore, we observed, in addition to the Acm shift in the disulfide cyclized decapeptide with a highSer and Thr content (model peptide II), the dimerization phenomenon in the Tl(TFA)3 process. Therefore we conclude that a side reaction, a S--O(Ser,Thr) Acm shift, occurred during the Cys(Acm) deprotection. This shift was supported by the demonstration of Ser(O-Acm) formation in the reaction of Boc-(L)-Cys(Acm) with Tl(TFA)3 in the presence of an equimolar amount of (L)Ser. We report here the efficiency of a trivalent alcohol, glycerol, as scavenger in the both Tl(TFA)3 and mercuric/ferricyanide methods, in an attempt to circumvent this side-reaction during the disulfide bond formation step starting from a bis-Cys(Acm) peptide with a high Ser and Thr content, such as the N-terminal loop of neurotoxin, model peptide II or a similar peptide.
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PMID:Side reaction during the deprotection of (S-acetamidomethyl)cysteine in a peptide with a high serine and threonine content. 843 50

A novel class of silyl-based protective groups compatible with the Bpoc/t-Bu strategy has been developed for the side chain of tyrosine. Carbobenzyloxy (CBZ) and biphenylisopropyloxy (Bpoc)-O-beta-trimethylsilylethyl-tyrosine (10 and 12) and CBZ-O-beta-dimethylphenylsilylethyl-tyrosine 14 were prepared in reasonable yields and in very high purity. The trimethylsilylethyl (TMSE) group proved to be 3-4 times more stable than the tert-butyl ether group towards 0.5% TFA. The latter is removed up to 4% during the acidolysis of the Bpoc group. As expected, the dimethylphenylsilylethyl (DMPSE) group was even more resistant towards 0.5% TFA (five time greater than the TMSE analog). Both silyl protective groups were found to be resistant towards a variety of reagents used in peptide synthesis, such as trialkylamines, hydroxybenzotriazole, trialkylphosphine and nucleophiles. They are readily removed in neat TFA in 5-20 min in the absence of cation scavengers, without any detectable alkylation of the phenolic ring. The application of the new silyl-based protective group was demonstrated by the synthesis of the C-terminal 29 amino acid peptide of the basic pancreatic trypsin inhibitor by the prior thiol capture methodology. The protected octapeptide BocC(Acm)QT)(tBu)FVY(TMSE)GG-PO-dibenzofuranthiol++ + was synthesized by solid-phase peptide synthesis using Bpoc-(O-TMSE)-Tyr-OH in greater than 90% yield and coupled to an unprotected 21-mer. The partially blocked, purified peptide was deprotected quantitatively in neat TFA in 1 h.
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PMID:Novel class of silicon-based protective groups for the side chain of tyrosine. 845 89

We used a microbore reversed phase column for acetonitrile/0.1% aqueous TFA gradient elution separation of peptides with the detection of their copper complexes by electrochemical detection. The copper complexes are formed in a short (1 or 1.5 min) postcolumn reactor following mixing of the eluent with the postcolumn reaction phase. Detection can be at an upstream anode or a downstream cathode of a dual-electrode electrochemical detector. The following parameters have been investigated for their effect on the sensitivity and the selectivity of the procedure: postcolumn pH, buffer type, temperature, reaction time, and anode potential. Of the 23 bioactive peptides used, there are several that fall into classes according to their chemical and electrochemical behavior with copper(II): those with a blocked terminal amine, those with aspartate in the third position, those that have an electroactive amino acid, and those that have a cyclic structure formed by the amide backbone through a Cys-Cys disulfide bridge. Depending on these attributes, the operating parameters have an influence on the sensitivity of the determination. Among the more well-defined results are the following. Uncomplicated peptides with a free amine terminus react rapidly in the postcolumn reactor and give signals in the range predicted by theory. There is evidence that longer peptides, and those with a blocked amine terminus, have a sensitivity limited by kinetic factors. The oxidations of tyrosine and tryptophan in peptides are dramatically influenced by buffer type at pH 9.8. At pH 8.0, there is no signal from several peptides in phosphate buffer, while in borate there is a signal.
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PMID:Detection of bioactive oligopeptides after microbore HPLC with electrochemical detection of their Cu(II) complexes: effect of operating parameters on sensitivity and selectivity. 868 5

The seven phosphopeptide derivatives based on the native -NEYTA- sequence of the pp60src protein kinase family, Asn-Glu-Tyr(P)-Ser-Ala, Ala-Glu-Tyr(P)-Ser-Ala, Ala-Ser-Tyr(P)-Ser-Ala, Ala-Ser(P)-Tyr-Ser-Ala, Ala-Thr-Tyr(P)-Ser-Ala, Ala-Thr(P)-Tyr-Ser-Ala and Ala-Ser(P)-Tyr(P)-Ser-Ala, were prepared in good yield using the "global' "phosphite-triester' phosphorylation method. The peptide resins were assembled using the Fmoc mode of solid phase peptide synthesis (PyBOP coupling method) with specific Ser-, Thr-, or Tyr-residues incorporated as their side chain free Fmoc-derivatives. The final "global' phosphorylation of the peptide resins was accomplished using di-tert-butyl N, N-diethylphosphoramidite followed by m-chloroperoxybenzoic acid oxidation of the resultant di-t-butyl phosphite triester intermediate. Subsequent resin cleavage and deprotection of the phosphorylated peptide resins was effected by treatment with 5% anisole: TFA and gave the seven phosphopeptides in high yield and purity. The use of the seven synthetic phosphopeptides in enzymatic (casein kinase-2) phosphorylation studies showed that, (A) the change of the target Thr site to Ser resulted in markedly improved phosphorylation of the peptide substrates, (B) that the Tyr(P) residue in the - 1 position was significantly more important than the Ser(P)/Thr(P) residue in the - 2 position for efficient seryl phosphorylation, and (C) that an acidic residue in the - 2 position relative to the target site facilitated phosphorylation of the downstream seryl residue irrespective of the nature of the acidic residue in the -Xxx-Tyr(P)-Ser- and -Xxx-Tyr-Ser- sequences {Xxx = Ser(P), Thr(P), Glu}. In addition to the Tyr(P) residue directing phosphorylation to the +1 position, the good phosphorylation of both ASY(P)SA and ATY(P)SA by casein kinase-2 indicated that the Tyr(P) residue was also able to direct phosphorylation to a Ser/Thr in the - 1 position.
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PMID:Solid phase synthesis of pp60src-related phosphopeptides via 'global' phosphorylation and their use as substrates for enzymatic phosphorylation by casein kinase-2. 881 74

We have previously described the conditions by which peptide synthesis by the solid-phase fragment condensation approach can be carried out using crown ethers as non-covalent protection for the N alpha-amino group. Here we demonstrate that the procedure can be extended to large, partially protected peptide fragments possessing free Lys and/or Arg residues. The first step was to ensure that complex formation on the side chain of amino acids was not detrimental to the methodology and exhibited the same solubility and coupling properties as N alpha-complexed peptides. Thus, a model hexapeptide was synthesized using Fmoc chemistry containing Lys and Arg residues, which, when complexed with 18-Crown-6, was readily soluble in DCM and coupled quantitatively to a resin-bound tetrapeptide. Two tripeptides were then prepared, one containing a free Ser residue, the other free Tyr, to examine the possible occurrence of side reactions. After coupling using standard conditions only the former tripeptide exhibited the formation of the O-acylation by-product (5%). Another model hexapeptide containing Lys, Tyr, Ser and Asp protected with a TFA-stable adamantyl group was complexed with 18-Crown-6 and coupled to the resin-bound tetrapeptide with near quantitative yield. Extending the length of the peptide to 21 and 40 residues, which represent sequences Gly52 to Leu72 (21-mer) and Pro33 to Leu72 (40-mer) from Rattus norvegicus chaperonin 10 protein, respectively, resulted in partially protected fragments that were readily soluble in water, thus enabling purification by RP-HPLC. Complexation with 18-Crown-6 gave two highly soluble products that coupled to resin-board tetramer with 68% and 50% coupling efficiencies for the 21-mer and 40-mer, respectively. Treatment with 1% DIEA solutions followed by acidolytic cleavage and purification of the major product confirmed that the correct product has been formed, when analysed by amino acid analysis and ESI-MS. These results served to extend the methodology of non-covalent protection of large partially protected peptide fragments for the stepwise fragment condensation of polypeptides.
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PMID:The use of crown ethers in peptide chemistry-V. Solid-phase synthesis of peptides by the fragment condensation approach using crown ethers as non-covalent protecting groups. 923 Apr 65

A series of Pro peptides containing the sequence of the oostatic hormone 3d and its shorter analogues 3a-3c differing in a number of the C-terminal Pro residues was prepared for a study of its effect on oogenesis in Sarcophaga bullata Parker (Diptera). Peptides 3a-3d were synthesized in solution by the fragment condensation of Boc-Tyr-Asp(OtBu)-Pro-Ala-Pro-OH (2f) with Pro oligopeptides H-(Pro)2-5-OtBu. The amino-terminal protected pentapeptide acid 2f was prepared by a stepwise procedure from TFA.H-Ala-Pro-OMe using Boc-Pro-OH, Z-Asp(OtBu)-OSu and Boc-Tyr-OSu. The H(Z)-(Pro)2-5-OtBu oligopeptides 1a-1h were synthesized from Z-Pro-OH and H-Pro-OtBu by a combination of stepwise procedure and fragment condensation. The 125I-labeled molecules of the octapeptide 3b and decapeptide 3d were used for radiotracer distribution studies. Evidence of content of the labeled peptide material in various parts of the insect body (ovaries, head, intestine) is presented. The time distribution of the labeled material in the insect organs was correlated with results of histological analysis of ovaries treated by nonlabeled peptides. The peptides assayed affected processes of egg development in 20-60% of ovarioles. The decapeptide 3d caused changes consisting in some resorbed egg chambers and normal appearance of vitellogenic eggs, whereas the octapeptide 3b caused abnormal yolk deposition and formation of big eggs with irregular yolk granules, proliferation of follicular epithelium in some egg chambers and about the same amount of resorbed egg chambers as decapeptide. These structural differences are complementary to the different values of organ radioactivities.
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PMID:Synthesis, radiolabeling and biological activity of peptide oostatic hormone and its analogues. 930 78

Boc-Cys(S-Pyr)-OH and Z-Cys(S-Pyr)-OH were prepared by addition of their cysteine derivatives to 3 equiv of 2,2'-dipyridyldisulfide in one portion. 2-Mercaptopyridine was removed by addition of 0.1 M Cu(NO3)2 to the solution. Both derivatives are white solids and can be used to facilitate the formations of heterodisulfide bonds. Two methods of synthesizing peptides with N-terminal Cys(S-Pyr) were also provided. Two peptide thiocarboxylic acids H-Tyr-Ser-Ala-Glu-Leu-Val-SH and H-Tyr-Ser-Ala-Glu-Leu-Gly-SH were prepared on the thioester benzhydryl resin with the cleavage condition of 1.0 M TFMSA/TFA instead of HF. From the orthogonal couplings of these peptides with H-Cys(S-Pyr)-Tyr-Ser-Glu-Leu-Ala-NH2, both intramolecular acyl transfers finished at pH 7 at about 15 to 20 min. The intermediate acyl disulfide peptide was collected by high-performance liquid chromatography and identified by liquid chromatography-mass spectrometry.
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PMID:Preparations of Boc-Cys(S-Pyr)-OH and Z-Cys(S-Pyr)-OH and their applications in orthogonal coupling of unprotected peptide segments. 956 4

We synthesized and characterized new chimera peptides by inserting an epitope of the mucin 1 glycoprotein (MUC1) as a 'guest' sequence in the 'host' structure of alpha-conotoxin GI, a 13-residue peptide (ECCNPACGRHYSC) isolated from the venom of Conus geographus. The Pro-Asp-Thr-Arg (PDTR) sequence of MUC1 selected for these studies is highly hydrophilic and adopts a beta-turn conformation. The alpha-conotoxin GI also contains a beta-turn in the 8-12 region, which is stabilized by two disulphide bridges in positions 2-7 and 3-13. Thus, the tetramer sequence of alpha-conotoxin, Arg9-His-Tyr-Ser12, has been replaced by PDTR, comprising the minimal epitope for MUC1 specific monoclonal antibodies (MAbs) HMFG1 (PDTR) and HMFG2 (DTR). Synthesis of the chimera peptide was carried out by Fmoc strategy on (4-(2',4'-dimethoxyphenyl-aminomethyl)phenoxy) (Rink) resin and either 5,5'-dithio-bis-(2-nitrobenzoic acid) (DTNB) or air oxidation was applied for the formation of the first Cys3-Cys13 or Cys2-Cys7 disulphide bridge, respectively. For the second disulphide bridge, three different oxidation procedures (iodine in acetic acid, 10% DMSO/1 M HCl or tallium trifluoroacetate (Tl(tfa)3) in TFA) were utilized. The HPLC purified peptides were characterized by electrospray mass spectrometry (ES-MS) and amino acid analysis. The CD spectra of the bicyclic MUC1-alpha-[Tyr1]-conotoxin chimera peptide showed partially ordered conformation with turn character. In antibody binding studies, the RIA data showed that both the linear and the bicyclic forms of MUC1-alpha-[Tyr1]-conotoxin chimera were recognized by MAb HMFG1 specific for PDTR sequence, while no binding was observed between MAb HMFG2 and various forms of the chimera. MAb HMFG1, using synthetic epitope conjugates or native MUC1 as target antigens, recognizes the PDTR motif more efficiently in the linear than in the bicyclic compound, but no reactivity was found with the monocyclic forms of MUC1-alpha-[Tyr1]-conotoxin chimera, underlining the importance of certain conformers stabilized by double cyclization.
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PMID:Synthesis and antibody recognition of mucin 1 (MUC1)-alpha-conotoxin chimera. 1080 90


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