Dinuclear organoiridium(III) mono- and bis-intercalators with rigid bridging ligands: synthesis, cytotoxicity and DNA binding.

The DNA binding and in vitro cytotoxicity of the dinuclear Ir(III) polypyridyl complexes [{(eta(5)-C(5)Me(5))Ir(dppz)}(2)(mu-pyz)](CF(3)SO(3))(4)1 and [{(eta(5)-C(5)Me(5))Ir(pp)}(2)(mu-4,4'-bpy)](CF(3)SO(3))(4)2-4 (pp=dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), dipyrido[2,3-a:2',3'-c]phenazine (dppz), benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn)) with the rigid bridging ligands pyrazine (pyz) or 4,4'-bipyridine (4,4'-bpy) have been studied. Stable intercalative binding into CT DNA (calf thymus DNA) is indicated for the dppz complexes 1 and 3 by induced negative CD bands at about 300nm and large viscosity increases, with the individual measurements being in accordance with intrastrand bis-intercalation for 3 and mono-intercalation for 1. The observed interruption of specific interresidue NOE cross peaks from the relevant nucleobase H6/H8 protons to the sugar H2'/H2'' protons of the preceding nucleotide is in accordance with bis-intercalation of complex 3 between the C3G18 and G4C17 base pairs and the T5A16 and A6T15 base pairs of the decanucleotide d(5'-CGCGTAGGCC-3').

Structure of Psb27 in solution: implications for transient binding to photosystem II during biogenesis and repair.

Psb27 is a membrane-extrinsic subunit of photosystem II (PSII) where it is involved in the assembly and maintenance of this large membrane protein complex that catalyzes one of the key reactions in the biosphere, the light-induced oxidation of water. Here, we report for the first time the structure of Psb27 that was not observed in the previous crystal structures of PSII due to its transient binding mode. The Psb27 structure shows that the core of the protein is a right-handed four-helix bundle with an up-down-up-down topology.

Sequence-specific (1)H, (13)C, and (15)N backbone assignment of the 28 kDa PDZ2/PDZ3 tandem domain of the protein tyrosine phosphatase PTP-BL.

Protein tyrosine phosphatase-basophil like (PTP-BL) represents a large multi domain non-transmembrane scaffolding protein that contains five PDZ domains. Here we report the backbone assignments of the PDZ2/PDZ3 tandem domain of PTP-BL. These assignments now provide a basis for the detailed structural investigation of the interaction between the PDZ domains 2 and 3 of PTP-BL.