Polypeptides, sequential

The first successful synthesis of a biologically active cyclic peptide, gramicidin S, was accomplished by Schwyzer and Sieber[6,7l via the 4-nitrophenyl ester. The fact that -protected peptide esters can be deprotected to give the peptide active ester salts has made this approach popular not only in the synthesis of sequential polypeptides but also of cyclic peptides. Among the various active esters examined for this purpose, the pentafluorophenyl esters have emerged as the most reactive ones, although a high risk of epimerization is encountered when C-terminal chiral amino acids are involved. 

The most widely nsed method to construct polypeptides is the use of a polymeric substrate to achieve multiple reactions. The Merrifield polypeptide synthesis on a polymeric substrate (crosslinked polystyrene) as the solid phase, revolutionized the synthesis of sequential polypeptides. The initial attachment of a protected amino acid to chloromethyl group containing polystyrene is achieved with triethylamine followed by hydrolysis to give 679 (Scheme 2.338, Step A). After removal of the protecting group, coupling of... 

The absence of cyclization at an earlier stage is responsible for the unique property of these monomers in providing an easy and effective route to high polymers by aprotic base initiation. This contrasts with other synthetic routes which are mainly employed in preparing sequential polypeptides [40]. The behaviour of glycine in forming a cyclic hexa-peptide is not found with most other NCAs since the development of secondary chain structures in the tail of the intermediate precludes cyclization. 

Since the Ala-Gly sequence is the major one in Bombyx mori silk, the structure of this sequential polypeptide is of importance in understanding the structure of silk. In early studies of )3-(AlaGly) it was found that the X-ray powder diffraction pattern and the IR spectrum resembled that from die crystalline component of B. mori silk. The proposed APPS structure of silk (Marsh et al., 1955b) led to a more detailed analysis of the X-ray pattern of )3-(AlaGly) (Fraser et al., 1965, 1966). This, together with conformational energy analysis (Colonna-Cesari et al., 1975),... 

This article reviews recent progress in the preparative, structural, and the spectroscopic study of homo and sequential polypeptides containing optically active aromatic amino acids. 

There are several ways to prepare peptides, polypeptides, and artificial proteins carrying these aromatic amino acids as their constituents. Homopolypeptides can be prepared by the polymerization of amino acid N-carboxyanhydrides (NCAs) derived from the corresponding amino acids ( ). Sequential polypeptides of the form (ABC...W) are prepared by the polymerization of the corresponding oligopeptide active esters ABC...W-X. Small peptides of any sequence can be synthesized by a step-by-step procedure (5). Finally, cultivation of some bacteria in the presence of artificial amino acids will possibly incorporate them into the proteins produced by the bacteria. In the following, attention will be focused on homopolypeptides and sequential copolypeptides carrying one type of chromophore on a chain. 

As described above, there is a multiplicity in the interactions among chromophores in the aromatic homopolypeptides. One of the reasons for the multiplicity is that 1-4, 1-5, and other interactions are possible in the homopolypeptides. In this sense, the homopolypeptides are not true one-dimensional chromophoric systems. To attain one-dimensional systems, sequential polypeptides carrying one chromophore in each helix turn were prepared. 

It is interesting that the sequential polypeptide with two Lys(Z) units as a spacer (m=2) is more efficient than that with one Lys(Z) unit as a spacer (m=l), although the density of naphthyl chromophore is lower in the former polypeptide. The efficiency for m=l is similar to that of m=3. These findings can be interpreted again by the differences in the positions of the nearest pair of naphthyl groups 1-5 for m=l and 3, 1-4 for m=2, and 1-6 for m=4. 

Sequential Polypeptides Carrying Pyrenyl Groups, Ground-State Conformations Sequential polypeptides carrying pyrenyl chromophores (V) were also prepared (15). 

Collagen fibrils of Wister rat tail tendon (9 weeks, female) was used. Mono-dispersed sequential polypeptides [Ala-Gly]i2 and [Pro-Ala-Gly],... 

Higuchi M, Minoura N, Kinoshita T. 1994. Photocontrol of micellar structure of an azobenzene containing amphiphilic sequential polypeptide. Chem Lett (2) 227 230. 

Rydon, Norman (p. 243, Plate 36) born in 1912 studied chemistry at London (B.Sc. 1931, Ph.D. 1933, D.Sc. 1938), D. Phil., Oxford 1939. Chemical Defence Experimental Section, 1940-1945. From 1945-1947 Member of Scientific Staff of the Lister Institute, then Reader at Birkbeck College, London, until 1949 and from 1949-1952 Reader at Imperial College, London. Professor at Manchester College of Science and Technology 1952-1957, Professor and Head of Department, Exeter University 1957-1977. Rydon s work outside of peptide research was on natural substances peptide topics at Exeter included cysteine peptides, sequential polypeptides, synthetic studies of ferredoxins. Chlorination followed by starchh-potassium iodide for the detection of peptides is known as Rydon-Smith reagent. 

D.W. Urry, T.L. TVapane, H. Sugano, and K.U. Prasad, Sequential polypeptides of elastin cyclic conformational correlates of the linear polypentapep-tide. J Am Chem Soc 103,2080-2089,1981. 

D.W. Urry, C.M. Venkatachalam, S.A. Wood, and K.U. Prasad, (1985c) Molecular structures and librational processes in sequential polypeptides from ion channel mechanisms to bioelastomers. In E. dementi, G. Corongiu, M.H. Sarma, and R.H. Sarma (eds), Structure and Motion Membr, Nucleic Acids and Proteins (pp. 

S -tetrakis (4-carboxyphenyl) porphyrin (TPPC) is used as the model pigment. Synthetic sequential polypeptides (PP) / / composed from Lys, Leu, Ala,Gly are used as model part of complexes ... 

The syntheses of some eight Om-containing hexapeptides and two Lys-containing hexapeptides were received too late to be included in the tabular summary of this chapter. The Om peptides were obtained for configurational inspection and the Lys peptides for sequential polypeptide syntheses. 

Urry, D.W. (1984) Protein elasticity based on conformations of sequential polypeptides the biological elastic fiber./. Pwt. Chem., 3, 403-437. 

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