Proteins, chemical synthesis folding

The field of synthetic enzyme models encompasses attempts to prepare enzymelike functional macromolecules by chemical synthesis [30]. One particularly relevant approach to such enzyme mimics concerns dendrimers, which are treelike synthetic macromolecules with a globular shape similar to a folded protein, and useful in a range of applications including catalysis [31]. Peptide dendrimers, which, like proteins, are composed of amino acids, are particularly well suited as mimics for proteins and enzymes [32]. These dendrimers can be prepared using combinatorial chemistry methods on solid support [33], similar to those used in the context of catalyst and ligand discovery programs in chemistry [34]. Peptide dendrimers used multivalency effects at the dendrimer surface to trigger cooperativity between amino acids, as has been observed in various esterase enzyme models [35]. 

Abstract Protein-like copolymers were first predicted by computer-aided biomimetic design. These copolymers consist of comonomer units of differing hydrophilicity/hydro-phobicity. Heterogeneous blockiness, inherent in such copolymers, promotes chain folding with the formation of specific spatial packing a dense core consisting of hydrophobic units and a polar shell formed by hydrophilic units. This review discusses the approaches, those that have already been described and potential approaches to the chemical synthesis of protein-like copolymers. These approaches are based on the use of macromolecular precursors as well as the appropriate monomers. In addition, some specific physicochemical properties of protein like copolymers, especially their solution behaviour in aqueous media, are considered. 

In addition to analyzing a protein for characteristics dictated by its specific nature, routine analytical assays are performed namely, amino acid analyses and amino- and carboxy-terminal sequencing. If necessary, disulfide assignments are made. A search is ordinarily conducted for oxidations and/or deamidations. In the case of recombinant proteins particular attention is paid to detecting signal sequences or proteolytically degraded species. In contrast, deletions and chemical modifications can be a consequence of proteins prepared by chemical synthesis. Lastly, tests are applied to determine if the protein is correctly folded into its native three dimensional structure. In addition, with recombinant proteins, sensitive immunological procedures are performed to ensure that host cell proteins have not been copurified with the protein of interest. 

Recently Richardson and Richardson (1987) have designed a protein that is intended to adopt an antiparallel /3-barrel structure similar to that of an immunoglobulin VL domain (Fig. 22). To aid in the chemical synthesis of the molecule, the protein was designed as a homodimer of two identical chains connected by an organic cross-linking moiety. The model for the designed protein is highly symmetrical (Fig. 22), with a 2-fold rotational... 

Fragment condensation on the solid support has been shown to be a feasible approach towards chemical synthesis of proteins. A progress report on the example of the TCR p-chain and AFP type III has been given. In the latter case a pure AFP type III peptide was obtained that however did not fold properly. 

T.M. Hackeng, J.A. Fernandez, P.E. Dawson, S.B. Kent, J.H. Griffin, Chemical synthesis and spontaneous folding of a multidomain protein anticoagulant microprotein S, Proc. Natl. Acad. Sci. U.S.A. 2000, 97,14074. 

Arrhenius, T., Lemer, R.A. and Satterthwait, A.C. (1987) The chemical synthesis of structured peptides using covalent hydrogen-bond mimics. In Oxender, D.L. (ed.). Protein Structure, Folding, and Design, vol. 2, pp. 453-465. Alan R. Liss, Inc. 

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