Proteins fragment condensation

Fe4(p3-S)3(p2-S)3, a 10-atom cluster present in the nitrogenase M center. Fragment condensation was used by the authors of reference 37 to synthesize [MoFe6S6(CO)i6 2 from the fragments Fe2S2(CO)612 and [Mo(CO)4I3] . None of the clusters mentioned so far mimic either the total structure or any function of those present in MoFe-protein. 

Of course, isotope filtering is not restricted to such binary systems, but can also be applied to multicomponent systems such as multiprotein complexes, or one or more ligands bound to proteins or protein complexes. It is also conceivable to construct single molecules from sections with different isotopic labeling in order to selectively observe one part by isotopic filtering. However, in these cases a specific synthetic approach has to be designed to allow for efficient incorporation of the isotope labels into the appropriate parts only (for example, by fragment condensation or inteins see also Chapt. 1) [5]. 

Note that proteins are now synthesized routinely by stepwise assembly or fragment condensation (see Vol. E22a, Section 4.1 ) 67 68 and chances of product contamination with shorter fragments that may have similar retention times under RP-HPLC should be considered 69 Additionally, size-exclusion HPLC was found to be particularly useful in distinguishing linear from cyclic peptides. 

Fragment condensation of peptides corresponds to a reverse protease reaction -peptide synthesis instead of cleavage - and this is well known in the hterature as well. In fact, proteases have been used extensively for peptide coupling (Jakubke etal, 1985 1996 Jakubke, 1987 1995 Luisi etal, 1977b). This work has shown that even small proteins can be synthesized by block-wise enzymatic couphng (see also Kullmann, 1987, and, for some more recent developments, Celovsky and Bordusa, 2000). 

The elongation step under a simulated environmental pressure is possible, as a never-born protein with 43 residues was obtained, although not by catalytic fragment condensation but by the Merrifield method (Chessari et al, unpublished data). 

The properties of protein fragments can Ik also used for the fluorometric assay of proteolytic activity. Curoffproposed that the increase in trichloroacetic acid-soluble tyrosine (both free and bound in small peptides) can be fluorometrically assayed after the condensation with nitrosonaphthol. 

Protein Synthesis on a Solid Support using Fragment Condensation... 

We chose to study the efficiency of the solid phase fragment condensation on the example of a type III antifreeze-protein (64 amino acids, 6.7 KDa), isolated... 

In the Table 2 the Fmoc-cleavage and times of fragment condensation for the AFP-type Ill-protein are given. 

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. 

The 2/HODhbt procedure has found widespread application for fragment condensation steps in the synthesis of proteins in solution (see Section... 

In order to synthesize longer polypeptides and small proteins, the condensation of suitable starting fragments is an essential prerequisite. Since chemical fragment condensations suffer from the danger of enantiomerization, enzymatic ligations are pronoising alternatives (see... 

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