Chemicals detection ability, increase

Genotoxic effects have been reported in animals treated with 3,3 -dichlorobenzidine. A single dose of 3,3 -dichlorobenzidine (1,000 mg/kg) administered to male and pregnant female mice induced micronuclei in polychromatic erythrocytes in the bone marrow of the males and in the liver of the fetuses, but not in bone marrow of the dams (Cihak and Vontorkova 1987). A micronucleus test is performed to detect a chemical s ability to induce chromosomal aberrations. However, the relevance of micronuclei formation to human health is not known. The reason for the lack of effect of 3,3 -dichlorobenzidine on bone marrow micronuclei formation in the mothers is unclear, but it may be related to deficiencies in the metabolic activation of 3,3 -dichlorobenzidine in female mice. The relative importance of pregnancy is unknown since the study did not evaluate nonpregnant females. In another study, an increase in unscheduled deoxyribonucleic acid synthesis (UDS) was observed in cultured liver cells from male mice previously pretreated orally with single doses of 500 mg/kg 3,3 -dichlorobenzidine no response was observed at a dose of 200 mg/kg (Ashby and Mohammed 1988). 

The ability to detect small genetic changes becomes more difficult as mass increases. There is further an upper mass range where analysis is impractical. For low-resolution instruments this limit is around a 100 mer. Thus the mass has to be minimized or a high-resolution instrument employed. Alternatively, the smaller the piece of DNA analyzed, the more it chemically resembles a primer or nucleotide monomer thus separation of the two during cleanup is difficult to do. If the primers and nucleotides are not removed, they can provide a massive background on MS analysis or inhibit ionization of the PCR product by preferential ionization. Thus for practical reasons it is extremely difficult to employ a PCR product below a 40 to 50mer for direct ESI MS or ESI MS-MS analysis. 

When a cationic center becomes sufficiently electrophilic, it may draw on electrons from neighboring Jt- and o-bonds and thus delocalize positive charge density. The onset of participation of n- and o-bonds can be detected as a departure from linearity in a Hammett-type plot as the electron-withdrawing ability of the aryl substituent increases. In stable ion studies, 13C NMR chemical shifts are generally used as a structural probe reflecting the charge density at the cation center (in closely related homologous cations, other factors that may affect chemical shift may be assumed constant). 

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