Synthesis and applications of novel, highly efficient HPLC chiral stationary phases: a chiral dimension in drug research analysis.

This review provides an overview of the synthesis and application of stable and versatile HPLC chiral stationary phases (CSPs), with emphasis placed on the binding strategies developed to anchor several structurally different chiral selectors to silica-gel microparticles. In addition, selected applications relating to the use of these CSPs for the direct resolution of racemates of biological and pharmaceutical relevance will be described. This review discusses enantioselective molecular recognition and dynamic stereochemistry of stereolabile compounds with reference to receptor-based chiral stationary phases (CSPs) and dynamic HPLC on CSPs, respectively.

Modifications of gamma-ray sensitivity of bacterial membrane by pre-exposure to light.

The exposure of E.coli B/r cells to ultraviolet (UV) or to visible light prior to irradiation with gamma-rays modifies the sensitivity of the cell membrane to the radiation damage responsible for the loss of intracellular K+ content. The experiments reported in the paper have shown: 1. exposure of bacterial cells to sublethal doses of UV light increases their sensitivity to gamma-ray-induced membrane damage, while exposure to visible light has the opposite effect; 2. in combined exposures, the visible light, either given before or after the UV always produces a strong photoprotective effect. In either case, the photosensitizing effect of UV is completely suppressed; 3. the photoprotection decays with time if cell suspensions are left in the dark before gamma-irradiation. At 0 degrees C, the half-life of the photoprotective effect is 25 min at pH 7 and 100 min at pH 7.5. The decay is due to the presence of oxygen; 4. the light band responsible for the induction of photoprotection has been estimated to lie in the wavelength region between 540 and 580 nm.