Peptides penta

In the work of Kurouski etcd. [57], the suppression was correlated with the spacing of amino acid side chains between metal and peptide backbone. This assumption was supported by SER spectra of short model peptides (penta-Gly penta-Ala hexa-Tyr and Trp-Arg-Trp-Trp-Trp-Trp) on 70 nm gold particles. The first two peptides show an enhanced amide I band in all spectra as they have short side chains and therefore the plasmon enhancement can reach the peptide bond. The latter two showed very heterogeneous spectra with 76% (hexa-Tyr) with amide I bands and 31% for (Trp-Arg-Trp-Trp-Trp-Trp). This supports the aforementioned hypothesis that a bulky side chain affects the interaction of enhancing field and peptide backbone. The same effect was observed in the respective SERS experiments, silver island films. The final answer to this phenomenon is not yet found, but as the amide I band is of crucial importance more experiments will certainly follow to unravel this effect. 

Tropoelastin is the soluble precursor of elastin and consists of alternating hydrophobic and hydrophilic peptide domains. The most common amino acids in the hydrophobic domains are Gly, Val, Ala, and Pro, which are often present in repeats of tetra-, penta-, and hexapeptides, such as Gly-Gly-Val-Pro, Gly-Val-Gly-Val-Pro, Gly-Val-Pro-Gly-Val, and Gly-Val-Gly-Val-Ala-Pro, respectively [3, 4]. The hydrophilic domains are mainly composed of lysines interspersed by alanines. 

Delta receptors are relatively selective for two related penta-peptides, methionine enkephalin and leucine enkephalin (met- and leu-enkephalin), which were isolated from porcine brain (Hughes 1975). Both met- and leu-enkephalin inhibit electrically induced contractions of guinea pig ileum, an effect that mimics those effects seen with opioid drugs, and is naloxone reversible. The enkephalins are processed posttranslational ly from proenkephalin, and secreted from central and peripheral neurons and endocrine cells in the adrenal medulla. 

Ni" forms square-planar bis-complexes with the amidate anions of L-Val, L-Phe, and L-Pro. The structure of bis(Gly)-bis(imidazole)nickel(ii) has been reported and the configuration around the metal atom is cis-O(carboxyl), cis-N(amine), cis-N(imidazole). Tetra- and penta-peptide complexes of nickel(ii) consume oxygen in neutral solutions as the metal ion catalyses peptide oxidation to give a number of products, including amides of amino-acids and peptides, oxo-acids, and C02- ... 

How many different ways can a penta-peptide be composed from the 20 natirral occurring amino acids. Answer the same question for a dodeca-peptide. 

Calcium in this case would coordinate with acyl oxygens from the polypeptide backbone of the protein, because of its unique amino acid sequences and potential conformations348). Non-polar peptides have been isolated from elastin which consists almost entirely of the three non-polar amino acids glycine, valine, and proline349). Portions of porcine tropoelastin have been partially sequenced350). Repeating tetra-, penta-, and hexapeptides have been observed. The tetrapeptide contains the sequence —Gly—Gly—L—Val—L—Pro— the pentapeptide —L—Val—L—Pro-... 

A number of methods for the synthesis of piperazic acid (7) and related derivatives are currently available as a result of growing interest in natural product chemistry and in their potential in medicinal chemistry. Their chemistry and conformational properties have been comprehensively reviewed. 2451 Racemic piperazic acid is obtained by condensation of penta-2,4-dienoic acid with phthalazinedione and subsequent reductive deprotection of the resulting A,A -bis(phthaloyl)-l,2,3,6-tetrahydropyridazine-3-carboxylic acid.12431 Resolution of racemic piperazic acid is achieved by fractional crystallization of the ephedrine salt of Nl-(benzyloxycarbonyl)piperazic acid from ethyl acetate. 246,2471 A typical route to enantiomerically pure (3S)-piperazic acid 56 starts from chiral 2-amino-5-hydroxyvaleric acid 55 as shown in Scheme 12.1248 Convenient stereoselective syntheses have been reported for 5-hydroxy- and 5-chloropiperazic acids as important constituents of natural cyclic peptides and depsipep-tides.1249,2521... 

Fig. (3). The structure of (prepro)-phytosulfokines. a) The amino acid sequence of prepro-phytosulfokines deduced from the sequence of the cDNA is shown. The signal peptide for secretion (dotted line) and the position of phytosulfokines within the precursor (bold, underlined) are indicated, b) Structures of the sulfated penta- (PSK-a) and tertrapeptides (PSK-P).

Biosynthesis of bacterial cell wall is remarkable in two respects (1) It entails the synthesis of a regularly cross-linked polymer and (2) Part of the synthesis takes place inside the cell and part outside the cell. The synthesis of cell wall is divided into three stages, which occur at different locations (1) synthesis of UDP-/V-acetylmuramyl-penta-peptide, (2) polymerization of IV-acetylglucosamine and N-acetylmuramyl-pentapeptide to form linear peptidoglycan strands, and (3) cross-linking of the peptidoglycan strands. 

This strategy was employed by Semple and co-workers [29] in the synthesis of the N(10)-C(17) fragment of cyclotheonamides, a family of 19-membered cyclic penta-peptides isolated from the sponge Theonella swinhoei, which are serine protease inhibitors. 

For all the substrates discussed so far the peptide catalysts employed had to differentiate between enantiomeric substrate molecules. Miller et al. subsequently screened peptide libraries for members able to selectively functionalize enantio-topic hydroxyl groups of meso inositols. In particular, they were able to convert myo-inositol 35 to either monophosphorylated D-myo-inositol-l-phosphate 37 or d-myo-inositol-3-phosphate ent-37 in high yield and excellent ee (98% Scheme 12.18) [38, 39], This remarkable result was achieved by use of either of the penta-... 

Serotonin transporter gene (5-HTTLPR) BRCA gene BRCA1 and 2 genes Viral DNA DMD gene Tetanus toxin C fragment Uracil Uracil ATP ATP Guanine Des-Tyr-Leu-enkephalin Des-Tyr-Leu-enkephalin Tri-, tetra-, penta-, octa-peptides... 

Cyclization of 1,4- and 3,4-disubstituted azetidinones are commonly used routes to /3-lactams and have been discussed (Sections 2.04.9.3 and 2.04.9.4), but cyclization of 1,3-disubstituted azetidinones is very unusual and one example can be included here. The /3-lactam 358, carrying an N-terminal dipeptide chain, reacts with the penta-fluorophenyl (Pfp) activated ester to give the cyclic peptide 359 containing a /3-lactam moiety in 93% yield <2004EJO4379>. 

Fig.20 MALDI-TOF mass spectrum of the oligopeptides obtained in the polymerization of (DL)-PheNCA at 22 °C, showing the m/z range from penta- to decapeptides. The two insets show expanded spectra of the octa- and nonapeptide ranges. The peaks at the wings of each group showing peptides of the same length represent molecules of homochiral sequence...

Langguth P, Bohner V, Biber J, Merkle HP (1994) Metabolism and transport of the penta-peptide metkephamid by brush-border membrane vesicles of rat intestine. J Pharm Pharmacol 46 34 40... 

A demonstration of liquid-phase combinatorial synthesis was recently introduced whereby the highly soluble, but highly crystalline, monomethyl polyethylene glycol (PEG) was employed to allow solution synthesis of a peptide library and solid phase-like purification by a change to a solvent where the PEG was insoluble. The demonstration penta-peptide library yielded the expected anti-P-endorphin binding sequence [65]... 

Various cyclization techniques have been used in the past, which include disulfide bond [61], side-chain lactam [59], and head-to-tail amide bond formation [62], In most cases, the readiness of an open-chain precursor to cyclize depends on the size of the ring and the sequence of the peptide to be cyclized. Usually, ring closure with hexa- and pentapeptides is somewhat hampered however, the cyclization may be enhanced by the presence of turn structure inducing amino acids such as glycine, proline, and D-amino acids, etc., as was the case in the study of McBride et al. [63], Spatola et al. [64] have recently conducted extensive studies in these aspects and several cyclic penta-, hexa-, and heptapeptide libraries were prepared and analyzed. Their results showed that rapid cyclization rates can be achieved with optimized synthesis and cyclization procedures, and many combinations of cyclic peptides can be formed in high quality if they contain structural features that make cyclization more facile. 

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