Disulfide exchange using

Using this approach, EGF has been successfully conjugated by disulfide exchange to the A chain of diphtheria toxin (Shimisu et al., 1980). A cystaminyl derivative of insulin also could be conjugated to the A chain of diphtheria toxin by this method (Miskimins and Shimizu, 1979). Other references to disulfide exchange using cystamine include Oeltmann and Forbes (1981) and Bacha et al. (1983) who prepared antibody-toxin and peptide-toxin conjugates, respectively. 

A metal-iodine exchange has been carried out on all three diazine systems under very mild conditions using lithium tri- -butyl magnesate, although only one substrate from each system was used 3-iodo-6-phenylpyridazine, 4-iodo-2-methylthiopyrimidine and 2-iodopyrazine. The pyridazine example was most problematic, possibly due to solubility problems. Aldehydes, benzophenone and diphenyl disulfide were used as the electrophiles <06SL1586>. 

C. Paul, K. Kirschner and G. Haenisch, Anal. Biochem. 101, 442 (1980) determine the deadtime for a stopped-flow apparatus using a disulfide exchange reaction. 

Post-synthetic functionalization reactions have been reported that make it possible to introduce new groups into folded proteins and peptides using natural [24, 25] as well as non-natural amino acids [26-30]. The disulfide exchange... 

The DCL was created under standard disulfide exchange conditions at pH 7.5. After equilibration for 48 hours, each of the expected 15 disulfide products could be observed in the library using LC-MS analysis (Fig. 2.11). The library was then equilibrated in the presence of CaM, followed by a centrifugation filtration step to separate protein/bound components from free components in solution. Analysis of the filtrate was complicated by the filtration membrane affecting the composition of the library. The bound components, however, provided meaningful results. Denaturation and filtration afforded a mixture of all peptides that had bound to CaM in the course of the DCL. HPLC analysis indicated significant amplification of dimer cc (80%) and a small amplification of dimer ec (10%). Resynthesis of these two components and binding assay established values of 10 and... 

The two most used reversible covalent reactions are disulfide exchange and palladium-catalyzed olefin metathesis. We first probed the incorporation of olefin units into the H bonded duplexes by subjecting the modified duplexes to a Pd (Gmbb s) catalyst. Based on a duplex template with the same unsymmetrical H bonding sequence used for directing the formation of the /3-sheet structures, we prepared two groups (strands 17 and 18) of five olefins covalently linked to the two template strands (Fig. 9.13). Mixing each one of components 17 with each one of components 18 in a 1 1 fashion results in a small library of 25 (5 x 5) members. 

Dynamic combinatorial libraries (DCLs) are continuously interconverting libraries that evenmally evolve to an equilibrium distribution [61-65]. This approach has been used successfully in the discovery of stable supramolecular assemblies from mixtures. Due to the nearly endless possible peptide sequences that can potentially be synthesised, the DCL approach is attractive for the identification of supramolecular peptide interactions. Indeed, disulfide exchange between cysteine residues has been explored for this purpose [66, 67] as has peptide-metal binding [68]. We have recently demonstrated protease-catalysed amide exchange in this context, which allows for the evolution of the self-assembled peptide structures, and will therefore allow exploration of peptide sequence space for biomaterials design. 

Bowen, W.K., Hellewell, S B., Keleman, M., Huey, R., Stewart, D. Affinity labelling of 6-opiate receptors using [D-Ala2, Leu5, Cys6]enkephalin covalent attachment via thiol-disulfide exchange, J. Biol. Chem. 1987, 262, 13434-13439. 

---