Circularly polarized luminiscence as a probe of metal ions binding sites in calmodulin

Circularly polarized luminiscence (CPL) from dilute solutions of Tb(III) bound to the Ca-binding protein calmodulin is reported. The dissymmetry ratio, gem, at 543.5 nm can be monitored as a function of equivalents of metal ion concentration. Competitive and consecutive addition of Ca(II) versus Tb(III) yield results which are consistent with previous results that suggest that Tb(III) and Ca(II) have a preferred affinity for different metal-ion binding sites in this protein.

Real-Time Particle Size Measurements in Laser-Generated Plumes by Mie Scattering

We report the application of a light scattering technique for the determination of particle sizes in a laser-generated plume. This procedure is based on the dissymmetry ratio obtained for observation at different angles relative to the excitation source. Good spatial and temporal resolution is achieved. The plume can be probed repeatedly during its lifetime. Large carbon particles, on the order of 85 nm and larger, are observed in a plume generated from pyrolytic carbon.

INFECTION OF MYCOBACTERIUM SMEGMATIS WITH D29 PHAGE DNA

DNA extracted from D29 mycobacteriophage produced plaques when plated on Mycobacterium smegmatis 607. The host bacterium did not require alternation such as conversion to protoplasts; cells susceptible to infection with intact phage were susceptible to DNA. The bases found in calf thymus DNA constituted the bases of D29 DNA, adenine being paired with thymine and guanine with cytosine. The dissymmetry ratio (A + T/G + C) was 0.56, and the buoyant density in CsCl was 1.722 with a GC content of 63.77 per cent. The efficiency of plating of the DNA is very much lower than that of intact D29, and it penetrates the host at a slower rate. As does intact phage, D29 DNA requires calcium ions for productive infection of 607. D29 DNA is significantly inactivated by incubation with RNAase, but the inactivation probably results from a complexing with the DNA rather than from enzyme hydrolysis.