X-ray studies on ternary complexes of maltodextrin phosphorylase.

We report crystal structures of ternary complexes of maltodextrin phosphorylase with natural oligosaccharide and phosphate mimicking anions: nitrate, sulphate and vanadate. Electron density maps obtained from crystals grown in presence of Al(NO3)3 show a nitrate ion instead of the expected AlF4- in the catalytic site. The trigonal NO3- is coplanar with the Arg569 guanidinium group and mimics three of the four oxygen atoms of phosphate.

Simulation of diffusion time of small molecules in protein crystals.

A simple model for evaluation of diffusion times of small molecule into protein crystals has been developed, which takes into account the physical and chemical properties both of protein crystal and the diffusing molecules. The model also includes consideration of binding and the binding affinity of a ligand to the protein. The model has been validated by simulation of experimental set-ups of several examples found in the literature.

Design and self-assembly of ditopic and tetratopic cavitand complexes.

The self-assembly of open ditopic and tetratopic cavitand complexes has been investigated by using monofunctionalized cavitand ligands and suitable metal precursors. In the case of ditopic complexes, self-assembly protocols, leading exclusively to the formation of both thermodynamically stable cis-Pt square-planar complexes 8 and 9 and the kinetically inert fac-Re octahedral complex 14, have been elaborated. The use of cis-[Pt(CH3)CN)2Cl2] as metal precursor led to the formation of monotopic trans-10 and ditopic trans-11 cavitand complexes, while cis-[Pt(dmso)2Cl2] afforded both cis-13 and trans-11 isomers.

Cavitand-based nanoscale coordination cages.

This communication reports design, self-assembly, solution, and solid-state characterization of nanoscale coordination cages formed by tetradentate cavitand ligands and appropriate metal precursors. The preorganization of the cavitand ligand in terms of structural rigidity and relative orientation of the pyridyl units leads to the exclusive formation of coordination cages in a wide temperature and concentration range. Desired features of the cage self-assembly process, such as reversibility in the presence of a competitive ligand and self-recognition of the cavitand components, have been assessed.