Peptides reaction

Fig. 34 Functionalisation of bait peptides. I Gold-labelled streptavidin is attached directly. 2 Biotin-labelled anti-FLAG antibody is bound to the FLAG on the peptide (reaction b) and this is used to attach gold-labelled streptavidin (reaction d). Reprinted with permission from Ryadnov and Woolfson [76]. Copyright 2004 American Chemical Society...

Amino acids activated at the amino group by a benzotriazolide moiety react with amino acids under elimination of benzotriazole and C02 to give peptides. Reaction is achieved by warming up equimolar amounts of the components in anhydrous acetonitrile or aqueous acetone.[45] The benzotriazolylcarbonylamino acids are prepared from benzo-triazolyl-1-carboxylic acid chloride and amino acids.[46]... 

The immobilized immunoprecipitates are washed twice with lysis buffer containing 0.5 MNaCl and twice with buffer A. The beads are resuspended in 20 /il of kinase buffer also containing the appropriate concentration of the specific peptide. Reactions should also be set up without peptide as a negative control for nonspecific or self-incorporation of radiolabel. To start the reactions, 5 /il of ATP is added (final concentration 0.1 mM unlabeled ATP, 1 /iCi [7 -32P]ATP (per assay) in kinase buffer). The assays are allowed to proceed for 15 to 30 min at 30° with constant shaking at 900 rpm, and stopped by spotting 20 /il of the sample (slurry) onto a square (1.5 X 1.5 cm) of phosphocellulose (P81) paper. The P81 papers are immediately immersed in 500 ml of 1% (v/v) orthophosphoric acid, and then washed 3 times with the same solution (to remove the excess ATP). The washes therefore contain almost all of the radiolabel and must be handled carefully and disposed of appropriately. The papers are briefly rinsed in ethanol and air-dried. The incorporation of 32P-label is measured by Cerenkov counting. 

For the preparation of N- 2-(methoxyphenyl)cthyl ]-4-mcthylbcn-zenesulfonamide (1) from Ameba resins A and Ba-Bd, 100 mg (0.089 mmol) Ameba resin A was added to a glass peptide reaction vessel, suspended in 3.0 mL 1,2-dichloroethane (DCE note 2), and treated with 26 pL (0.18 mmol, 2.0 Eq.) 2-(4-methoxy-phenyl)ethylamine (note 2) and 38 mg (0.178 mmol, 2.0 Eq.) sodium triacetoxyborohydride (note 2). The suspension was shaken for 1 h treated with 5 mL MeOH filtered on a glass frit and washed with DCM (2x5 mL), DMF (2x5 mL), MeOH (2 x 5 mL), and DCM (2x5 mL). The resin was dried under vacuum (0.5 torr) at room temperature overnight. The resin was suspended in 1.5 mL DCM, treated with 155 pL (0.89 mmol, 10.0 Eq.) N,N-diisopropylethylamine (note 2) and 85 mg (0.445 mmol, 5.0 Eq.) p-toluenesulfonyl chloride (note 2), and shaken for 3.5 h. The reaction mixture was filtered on a glass frit, washed with DCM (2 x 5 mL), DMF (2x5 mL), MeOH (2x5 mL), and DCM (2 x 5 mL), and dried under vacuum (0.5 torr) at room temperature for 2h. The resin was treated with 2.5 mL of a solution of 5% trifluoroacetic acid (note 2) in DCM, shaken for 15 min, filtered on a glass frit, and washed with DCM (3x5 mL). The combined filtrate and washings were concentrated and dried under vacuum (0.5 torr) at room temperature overnight to afford 18.0 mg (66%) N- [2-(methoxyphenyl)ethyl] -4-methylbenzenesulfonamide (1). 

Solid-Phase Synthesis of (53-Peptides Reaction of Fmoc-Protected Diazo Ketones with Concomitant (53-Peptide Formation on a Solid Support 1401... 

A number of complexes of the general type (CoN4(OH)(OH2)]2+ (N4 = a system of four nitrogen donors) stoichiometrically cleave the N-terminal amino acid from di-or tri-peptides. Reactions have been described for N4 = en2,164-165 trien166 167 and tren.168,186 In the case of trien complexes, the proposed mechanism for peptide hydrolysis is shown in Scheme 7. Hydrolysis can occur by two pathways (a) attack by external hydroxide on the O-bonded chelated peptide, and (b) intramolecular attack of coordinated hydroxide on the N-bonded peptide. 

The intramolecular addition of cysteine thiyl radicals (CysS ) to phenylalanine yielding alkylthio-substituted cyclohexadienyl radicals was observed in Cys-Phe and Phe-Gly-Cys-Gly peptides.CysS radicals were generated by pulse irradiation of aqueous solution containing the respective disuHide-linked peptide [reactions (11)-(14)] ... 

Figure 1 shows the influence of the solution pH on the yield and initial rate of synthesis of CBZ-Lys-Gly-OMe at a temperature of 25°C and [CBZ-Lys] = [Gly-OMe] = 20 mM. The maximum yield is achieved for pH values around 6-6.5. Under thermodynamically controlled conditions, the peptide synthesis occurs between the non-ionic forms of the acyl-donor (CBZ-Lys) and the nucleophile (Gly-OMe). The concentration of these nonionic forms depends on the pH, since an intermediate value between both pK (pHopt = V IpKa +pKb]) is needed in order to achieve high synthetic yields. On the other hand, the reaction rate increases up to pH 7, which is in agreement with the results obtained in the synthesis of the peptide benzoylarginine-leucinamide catalyzed by immobilized trypsin (10), where the authors suggest the nucleophihc attack of the non-ionic form of the nucleophile on the acyl-enzyme complex as the controlling step of the peptide reaction. 

A very interesting compound may be prepared via this method and used in the stereoselective syntheses of peptides. Ugi has found that asymmetrically induced four-component syntheses will form optically active peptides (Reaction 36) (42, 43). Compounds of the type R —NHL, must, to be useful in this synthesis, meet these criteria ... 

In proteomics, the technique can be used to investigate the products of enzyme-peptide reactions. These can be cleavage products" or newly formed products". An example of an application for LC-MS is shown in Figure 3.43, where the LC effects the separation of a mixture and then the mass spectrum for each peak can be obtained and displayed to confirm identity of the breakdown products. A peptide (Z-gly-pro-tyr-OH) was mixed with an enzyme and, following incubation the mixture was subjected to LC-MS... 

Figure 3.43 Results obtained for an enzyme-peptide reaction using the LC-MS technique.

V Hornik, E Hadas. Self-encoded, highly condensed solid phase-supported peptide library for identification of ligand-specific peptides. Reaction Polymers 22 213-220,... 

Peptides. Reaction of the heterocyclic compounds with amines gives peptides. 

Fruton (1950) has recently pointed out the possibility that trans-peptidation reactions may occur in the presence of proteolytic enzymes. Such reactions may be represented as follows ... 

Mitsunobu reaction of p-hydroxy-a amino acid peptides. Reaction of the Cbz-prolyl-threonine N-methyl amide 1 with P(C6Hs)3 and DIAD provides the peptide aziridine 2 in 84% yield. 

Acetylation is one of the most frequently used derivatization techniques in the mass spectral analysis of peptides. Reaction with freshly distilled acetic anhydride in methanol [27] results in acetylation of a-amino functionalities within one minute. Acetylation at other less reactive sites may be accelerated by the addition of a small amount of base, such as NaHC03 or triethylamine [28], Peptide hydroxyl and amino groups can be acety-lated by exposure to a 1 1 mixture of acetic anhydride/ pyridine for about 40 minutes. The net result of the reaction is a positive shift of 42 daltons for each acetyl group addition. The failure of an acetylation reaction in a peptide analysis may be diagnostic of a blocked N-terminus. 

Introduction Amino acids are activated as aminoacvl adenylates (I). Peptide synthesis occurs from stable thiolesters (II), where the cofactor 4 -phosphopantetheine has been proposed to function in trans-thiolation and peptidation reactions (VI). Reversibility of reactions has only been demonstrated for reactions (D - . 

The growing peptide chain is thioester linked to the enzyme during the peptidization reactions. 

Enzyme bound phosphopantetheine participates in the peptidization reactions as a mobile acceptor and donor of thioester linked intermediates. 

Under the above mentioned conditions of the formation and peptide reaction of symmetric anhydrides, we have no indications for over-reactions like self-acylation at the urethane-masked amino group of the activated compound [71], as was occasionally observed by Merrifield [149]. 

Each of the aforementioned modifications has undoubtedly provided improved crude products in a number of such syntheses. However, improved solvation of the polymer-peptide/reaction media, although extremely desirable, only aims to limit the effects and extent of p-sheet secondary structure formation. The potential for intermolecular backbone hydrogen bonding, the fundamental cause of the phenomenon, still exists. 

Cu(III)(peptide)], with [Cu(I)(dmp)2], where dmp is 2,9-dimethyl-1,10-phen-anthroline, are rapid, outer-sphere processes which show some adherence to Marcus behavior,although the [Cu(dmp)2] self-exchange rate appears to be very dependent on the cross reaction,a lower limit of 3 X 10" mol" liter s arising from the [Cu(III)(peptide)] reactions, while a value of 9 x 10 mol liter s" is obtained from reaction with [IrCle], both at 25°C and 0.10 M ionic strength.Reactions of the copper(I) complex of the sterically hindered phenyl sulfonate derivative of dmp, [Cu(dpmp)2], with [Cu(III) (peptide)] are complicated by limiting rate behavior which is ascribed to activation of the copper(III) complex [reaction (25)]... 

In the presence of D-serine, o-valine, D-threonine, or D-methionine, a number of bacteria synthesized modified peptidoglycan precursors having o-alanyl residues replaced by one of the other D-amino-adds. Many of the modified mucopeptides were not cross-linked, since they are poor substrates in the trans-peptidation reaction. 

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