PubMed Health⌕ Search

Biomedical subjects

R B Shukla

Publications and source records attributed to R B Shukla.

9 recordsLinked to original sources
PubMed2005

Multidisciplinary investigation of atypical inclusion complexes of beta-cyclodextrin and a phospholipase-A2 inhibitor.

BMS-188184, an anthracene derivative, has been found to form at least two complexes with beta-cyclodextrin. The association/dissociation kinetics of the two complexes were extremely slow, with one complex requiring approximately 24 h, and the other complex requiring more than 8 weeks, to reach equilibrium. The stability constants of the two complexes were estimated at approximately 11,000 and 39,000 M(-1) under nonequilibrium conditions. The slow rates of dissociation allowed the complexes and the unbound BMS-188184 to be separated using high-performance liquid chromatography. Exact mass liquid chromatography/mass spectrometry, tandem mass spectrometry, and nuclear magnetic resonance techniques were used to characterize the stoichiometry of both complexes as 1:1. Because of the ability of the complexes to survive high-performance liquid chromatography analysis, their slow reaction rates, and 1:1 stoichiometry, the complexes were tentatively characterized as [2]-rotaxanes. The available data suggest that the two complexes are conformational isomers.

Blood Proteins↗
PubMed1997

Alteration of electronic relaxation in MR contrast agents through de-novo ligand design.

The longitudinal electronic state lifetime of the paramagnetic Gd metal within a macrocyclic ligand core can be increased by designing ligand frames that alter the vibronic interactions between the ligating atoms and the metal. We conducted the first pulsed EPR studies that demonstrated the increase in the longitudinal state lifetimes of the electronic subsystem at cryogenic temperatures. We also designed a simple sucrose/ water model that significantly increases the rotational correlation time in solution of the Gd chelate. This model system enables relaxivity studies at ambient temperatures that more readily interrogate exchange and electronic contributions to the inner-sphere relaxivity by effectively removing the rotational correlation time contribution. These results combined with water residence (Q) measurements suggest that rigidification of the macrocyclic core or that of the pendant arms increases the longitudinal electronic state lifetime of the paramagnetic Gd metal. This increased lifetime possibly contributes to the improved relaxivity for the rigid Gd chelates observed in the sucrose/ water model studies.

Chelating Agents↗
PubMed1982

Association of cold weather with testicular torsion.

A retrospective study of 46 patients who presented with proved testicular torsion over five years at two Dublin hospitals showed that in 40 cases torsion had occurred when the temperature was under 2 degrees C; the incidence of torsion was higher during the cold months of the year. Both of these findings were statistically significant. These and other results suggest that the ambient temperature may have some role in the incidence and aetiology of testicular torsion.

Adolescent↗