The structure of neuromedin C, a 10‐residue bombesin‐like neuropeptide with the sequence Gly‐Asn‐His‐Trp‐Ala‐Val‐Gly‐His‐Leu‐Met‐NH2, has been investigated. Like human serum albumin, neuromedin C contains the amino‐terminal CuII‐, NiII‐binding (ATCUN) motif which has high affinity for CuII and NiII. The solution structure of the NiII‐peptide complex has been calculated based on 2D ROESY data obtained at 25°C, using a hybrid distance geometry‐simulated annealing approach. Comparison of H, 13C and 15N chemical shifts and ROESY data in the presence and absence of NiII demonstrates that the metal binds at the N‐terminus of the peptide, leading to a conformational change. The metal complex adopts a conformation comprising two connected turns including residues Gly to 3His and 5Ala to 8His. The first turn corresponds to the NiII coordination ligands in a square planar conformation, and the second reflects the interaction between 4Trp and 8His. The results may have important physiological implications in the phenomenon of neurotransmission. © Munksgaard 1997.

Phosphorus-31 NMR has been applied to the characterization of terminal phosphates on fragments of calf thymus DNA induced by three different nuclease systems: DNase I, DNase II and the artificial nuclease 'Mn-TMPyP/KHSO5'. In this last case, the oxidative damage to deoxyribose leads to two monophosphates esters (at the 3' and 5' ends) on both sides of the cleavage site. This method constitutes a promising approach to visualise the phosphate termini generated in DNA or RNA cleavage by cytotoxic drugs or chemical nucleases and provides a novel insight into the molecular aspects of their mechanism of action.

H-, 13C-and '95Pt-NMR spectroscopies are used to identify the complexes formed between the platinum salts cis-(NH3)2PtC12 (cis-DDP), truns-(NH3)zPtC12 (trans-DDP), cis-(en)Pt(ONO&, and [(dien)PtBr]Br and the tetrapeptide Boc-Cys1(SMe)-Ser2-Ala3-Cys4(SMe)-CONH2 (CSAC) containing the sequence Cys-X-Y-Cys (X, Y = amino acids) and being a model of metallothionein (MT) and/or a model for platinum binding to methionine type sulfur, known to occur in biological systems. MT, rich in cysteine is known to bind both in vivo and in vitro with the antitumor drug cis-DDP. The 'H-and 13C-NMR assignments were made by two-dimensional homoand heteronuclear experiments for the ligand CSAC. The S-CH3 groups coordinate through sulfur to Pt(I1) in all cases. The results show that cis-DDP forms a mixture of different diastereoisomers around the sulfur chiral centers and/or polymeric species with NH3 liberation, due to the strong trans-effect of sulfur. cis-Pt(en)(ONOz)z forms a monomeric (1: 1) chelate structure with CSAC, without en liberation, coordinated through both sulfur atoms. However, slow en liberation could take also place upon increasing temperature. Three signals are observed in the 'H-and 195Pt-NMR spectra of this complex in accordance with the proposed monomeric structure. truns-DDP, on the other hand, forms a 2:l complex with CSAC identical to the one formed by [Pt(dien)Br]Br, both coordinated to the -S-CH3 groups. No amine release was observed in the case of these two complexes.