Medium effects in action, visualized by the crystal structures of open and closed forms of a molecular receptor

Abstract

The water-solu ble macrobicyclic cyclophane molecule 16-has been crystallized in two very different shapes that display the operation of medium, especially hydrophobic effects: an inflated cage structure building up cylinders disposed in an hexagonal array; a flattened structure stacked in molecular layers separated by aqueous layers in a lamellar arrangement.

Structure of the biimidazole dimer obtained from a bridged N,N'-diimidazolyl sulfone

“…Bond distances, angles and torsion angles are given in Table 2. The average S--O bond distance, 1.414 (3)A, is essentially the same as the average [1.418 (3)/~] found in other N-arylsulfonylimidazole derivatives such as N-toluenesulfonylimidazole (Cesario & Guilhem, 1977) and 1-(4-imidazolylsulfonyl)-4-phenylimidazole (Guggenberger, 1975). The S--N(1) bond [1.645 (3)A] is statistically shorter (>_ 30-diff, OVdiff = 0.0042 A) than the S--N(4) bond [1.662 (3)A].…”

High-Resolution Structure (1.33 Å) of a HEW Lysozyme Tetragonal Crystal Grown in the APCF Apparatus. Data and Structural Comparison with a Crystal Grown under Microgravity from SpaceHab-01 Mission

“…This kind of octahedral and distorted geometry was also seen in the major grove site of a nucleic acid structure (Chevrier et al, 1986). In crystallography of small organic molecules, this type of geometry is frequently observed for Na ÷, showing a preference for oxygen donor ligands (Cesario et al, 1993).…”

“…In the ground structure, one of the position of N( atom is hydrogen-bonded with several water molecules and in interaction with Oc2 from residue Glu7; the The short distances (between 2.2 and 2.6.~) are particular to the Na + environment observed in structures of small molecules (Cesario et al, 1993) and in nucleotides (Black, Huang & Cowan, 1994). (b) The Na ÷ coordination geometry can be considered as a distorted octahedron.…”

Solvent Triggering between Conformational States in Amphiphilic Shape-Persistent Macrocycles

“…However, so far most investigations on solvent-induced conformational changes in artificial minimal model systems have been performed in solution . We have recently shown that amphiphilic shape-persistent macrocycles, like 1 , can adopt different conformations depending on the solvent and the presence of appropriate guest molecules in such a way that either the phenol-OH groups or the alkyloxy groups of the ring point inward (molecular reversible coats) .…”