"RKKH" peptides from the snake venom metalloproteinase of Bothrops jararaca bind near the metal ion-dependent adhesion site of the human integrin alpha(2) I-domain.
Integrin alpha(1)beta(1) and alpha(2)beta(1) are the major cellular receptors for collagen, and collagens bind to these integrins at the inserted I-domain in their alpha subunit. We have previously shown that a cyclic peptide derived from the metalloproteinase domain of the snake venom protein jararhagin blocks the collagen-binding function of the alpha(2) I-domain. Here, we have optimized the structure of the peptide and identified the site where the peptide binds to the alpha(2) I-domain. The peptide sequence Arg-Lys-Lys-His is critical for recognition by the I-domain, and five negatively charged residues surrounding the "metal ion-dependent adhesion site" (MIDAS) of the I-domain, when mu…
An MO study of neutral C8 high-symmetry clusters
Abstract Highly symmetric octacarbon clusters, i.e. a cube (O h ), a twisted cube (T d ), a tricyclic cage (C 3v ) and a planar (D 4h ) structure, were fully optimized at the HF, B3LYP and MP2(Full) levels of theory. These stationary points were shown to be local minima on the potential energy surface by frequency calculations. The stability of these clusters compared to the cyclic planar (C 4h ) ground state was found to be strongly dependent on the level of theory. MP2(Full) calculations suggest that cubic C 8 is a local minimum, its energy being 273 kJ/mol higher than the ground state. Structural parameters and fundamental vibrations are presented.
A linear open-chain piperazine-pyridine ligand and its meso-helical Co complex
Abstract An oligomeric ligand (HPPy) 2 P, N , N ′-bis[2-(6-( N -( N ′-(2-hydroxyethyl)piperazinyl)methyl)]piperazine, was designed to resemble structurally open-chain aza-crowns. Owing to the all- trans configuration of piperazine and pyridine free electron pairs, it should adopt a near linear overall structure in solvent. Theoretical calculations at ab initio level confirm the overall linear structure of free ligand. The crystal structure of the complex [(HPPy) 2 P][Co(NO 3 ) 2 ] 2 shows a contraction from ∼3 to 2 nm structure. Each coordination site creates either a Δ or Δ configuration around the metal ion, thus causing a ligand with an even number of coordination centres to be meso -hel…