The NCI Drug Information System. 2. DIS Pre-Registry

The Pre-Registry Module of the Drug Information System (DIS) is a staging area through which all new compounds are passed prior to acquisition and testing. Several methods are available for the entry of structures into the Pre-Registry; all involve built-in data validation. Newly entered structures are examined by computer programs for structural novelty and potential for anticancer activity. For those compounds that proceed to acquisition, the various acquisition steps, such as letter writing and record updating, are performed automatically. When a sample is obtained, the entire Pre-Registry record is updated and moved forward into the permanent DIS chemistry files.     

Cyclodipeptides: Structure and conformation of cyclo(tyrosyl-prolyl)

The structure and conformation of the cyclodipeptide, cyclo(Tyrosyl-Prolyl), cyclo(Tyr-Pro) have been investigated with X-ray crystallographic and spectroscopic methods. Two conformations of cyclo(Tyr-Pro) crystallized in the space groupP2₁2₁2 with cell dimensionsa=11.890(3),b=12.057(1),c=18.528(4). Both these conformations are uncommon for cyclodipeptides containing a proline residue. The tyrosyl side chains of these conformers are folded towards the diketopiperazine (DKP) ring. The DKP ring adopts a flattened chair conformation in contrast to the typical boat conformation generally observed for DKP rings. The conformation of the pyrrolidine ring can be described as a pseudo C₂ symmetrical twist. One intermolecular hydrogen bond was observed for each of the two conformations of cyclo(Tyr-Pro). The hydrogen of the hydroxyl group of the tyrosyl residue is hydrogen bonded to the oxygen of the carbonyl group of the diketopiperazine ring, i.e., the carbonyl group originating from the tyrosyl residue. NMR spectroscopic studies indicated a different conformation for cyclo(Tyr-Pro) in solution similar to the generally observed conformation of cyclodipeptides, i.e., extended aromatic side chain and boat conformation for the DKP ring.     

A RHEED study of oxygen adsorbed on copper

The effect of oxygen adsorption on various clean, stepped copper surfaces at 300°C was examined by the use of Reflection High Energy Electron Diffraction (RHEED). The stability of a few high index planes is considered and the idea of this enhanced stability being due to a “fit” between the adsorption structure and the terrace width was extended. The interpretation of RHEED patterns from faceted surfaces was discussed so as to account for such features as the curving of the rods and the apparent existence of extra rods.     

Studies of reactive triple shock collision

Experimental studies have been performed on two-dimensional reactive blast waves in a diverging nozzle. Both blast and reaction wave loci have been measured and the results compared with numerical calculations.With the inclusion of additional wedges into the channel reactive Mach reflections were generated and the subsequent interactions of these waves have been observed and modelled using a full chemistry scheme. The results are in excellent agreement and the technique shows great promise for the study of the coupling between chemistry and gas dynamics under conditions similar to those obtaining within a single cell of a gaseous detonation.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.