Upon storage under aerobic conditions metallothioneins (MTs) form a new species, which is characterized by a molecular mass approximately twice the size of monomeric MT and shifted (113/111)Cd- and (1)H-NMR resonances. The investigation of this oxidative dimerization process by NMR spectroscopy allowed us to structurally characterize this MT species that has been described to occur in vivo and might be synthesized under conditions of oxidative stress. The oxidative dimer was characterized by the formation of an intermolecular cysteine disulphide bond involving the alpha-domain, and a detailed analysis of chemical shift changes and intermolecular nuclear Overhauser effects points towards a disulphide bond involving Cys(36). In contrast to the metal-bridged (non-oxidative) dimerization, the metal-cysteine cluster structures in both MT domains remain intact and no conformational exchange or metal-metal exchange was observed. Also in contrast to the many recently reported oxidative processes which involve the beta-domain cysteine groups and result in the increased dynamics of the bound metal ions in this N-terminal domain, we found no evidence for any increased dynamics in the alpha-domain metals following this oxidation. Therefore these findings provide additional corroboration that metal binding in the C-terminal alpha-domain is rather tight, even under conditions of a changing cellular oxidation potential, compared with the more labile/dynamic nature of the metals in the N-terminal beta-domain cluster under similar conditions.

The inhibition of receptor tyrosine kinases (RTKs) has become a successful approach in the development of anticancer agents. Many potent small-molecule kinase inhibitors have been discovered. We report herein a series of pyrrolo-fused-heterocycle-2-indolinone analogues as inhibitors of vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), and c-Kit. Among them, some pyrrolo-fused six- and seven-membered-heterocycle derivatives such as 9, 15, 23, and 25 are potent inhibitors of VEGFR, PDGFR, and c-Kit both enzymatically (<50 nM) and cellularly (<50 nM). Furthermore, compounds 9 and 25 possess favorable pharmacokinetic profiles and demonstrate good efficacies against human HT-29 cell colon tumor xenografts in nude mice. Further evaluations are in progress.

Upon storage under aerobic conditions metallothioneins (MTs) form a new species, which is characterized by a molecular mass approximately twice the size of monomeric MT and shifted ""$/"""Cd-and "H-NMR resonances. The investigation of this oxidative dimerization process by NMR spectroscopy allowed us to structurally characterize this MT species that has been described to occur in i o and might be synthesized under conditions of oxidative stress. The oxidative dimer was characterized by the formation of an intermolecular cysteine disulphide bond involving the α-domain, and a detailed analysis of chemical shift changes and intermolecular nuclear Overhauser effects points towards a disulphide bond involving Cys$'. In contrast to the metal-bridged (non-oxidative) dimerization, the metalcysteine cluster structures in both MT domains remain intact and

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