LISA: a new aerosol generation system for sampler evaluation.

A Large Inorganic Sampler Assembly (LISA) system has been built for the evaluation of particulate sampling devices, including the device used in the NIOSH method for respirable silica (Method 7500). Significant features of LISA are the following: 1) The accommodation of up to 30 filter cassettes or 12 cyclone samplers; 2) high precision of particulate deposition (Sr = 2.2%); 3) micro-computerized reduction of optical particle counter data; and 4) special design features to facilitate ease of operation. The system has been used to evaluate sampler systems for a number of different airborne dusts.

The electronic structure of platinum-guanine complexes.

Molecular orbital calculations using the SC-MEH method have been carried out on guanine and its mode of interaction with the anti cancer drug,cis-diamminodichloroplatinum(II) (DDP), in various geometrical bonding conformations. It is shown that if indeed a monomeric complex between DDP and guanine is formed, the N-7 and O-6 positions of guanine bond most strongly with DDP in both monodentate and bidentate chelation models. The influence of this bonding on the N-1--H-1 bond is studied in terms of atomic charge variations and orbital overlap population densities to determine if miss-pairing in DNA might occur via the loss of the guanine H-1 proton, as proposed in the mechanism of O-6 methylation. Preliminary findings do not support one of the proposed mechanisms for miss-pairing in DNA if a bidentated N-7, O-6 DNA-DDP chelate is formed. Interest in the cellular effects of square-planar platinum complexes began with Rosenberg's discovery in 1965 that DDP, inhibited cell division with inhibiting growth rate in Escherichia coli bacteria [u]. Shortly thereafter, the anti-cancer activity of DDP and a number of related platinum complexes was demonstrated [2]. Since then, DDP has been used effectively for a number of types of cancers including lung, head and neck, prostate, bladder, ovaran, and testicular cancers [3], and has recently been released in the United States for distribution as a prescribed drug in chemotherapy.