A computational study of vanadium peroxides (L n V(O 2 ) m ; m ) 0-4), important for their biochemical and catalytic activity, is reported. In the compounds studied, ancillary ligands (L n ) are generally the hard, oxygen-and nitrogenbased donor ligands, e.g., carboxylates and pyridines, prevalent in the coordination chemistry of vanadium peroxides. The utility of estimating missing metal-dependent molecular mechanics (MM) parameters from quantum calculations is demonstrated. Given the limited vibrational data for many families of transition metal complexes, quantum calculations are a viable source for parameters to use in development of force fields. A conformational search of [V(O 2 ) 3 F] 2using MM yielded a geometry inconsistent with experiment, but consistent with ab initio geometry optimizations. A reinvestigation of this structure is therefore of interest. Molecular mechanics provides a quick and accurate method for obtaining structural information. The level of agreement for structural prediction is competitive with that obtained using more computationally intensive methods in much less time. In most cases it was seen that MM and quantum predictions reinforced each other, lending greater confidence in modeling results. In other cases, classical and quantum results were in conflict, indicating the need for further higherlevel, quantum calculations. Hence, MM and low-level quantum calculations, when used together, provide a valuable method for quickly probing the conformational space of large coordination complexes.
Cereal Chem. 79(1):85-91The growth and brain development of laboratory rats fed typical indigenous tortilla-based diets were determined throughout two generations. The experiment compared three different types of tortilla-based diets: regular tortillas produced from dry masa flour (RDMF), tortillas obtained from fresh masa (FM), and tortillas produced from dry masa flour fortified with 6% defatted soybean and enriched with vitamins B 1 , B 2 , niacin, and folic acid and microminerals iron and zinc (FEDMF). Female rats were mated 58 days postweaning with males belonging to the same treatment with the objective of obtaining second generation pups that were further subjected to regular lactation and 28 day postweaned growth. A comparison between growth of first and second generation rats was determined. In addition, representative animals of each physiological stage were first exsanguineted for hematocrit determination and then slaughtered with the aim of obtaining femur and brain tissues. Cerebral DNA and number of neurons were determined in each of the brains sampled. Growth of rats fed FEDMF was significantly higher (P < 0.05) in both generations than counterparts fed RDMF or FM. The difference among treatments was more evident in second generation rats. Pregnancy rate, number of newborns per litter, litter weight, and pup's survival rate was higher for the control and FEDMF treatments. Femur growth was also higher (P < 0.05) for first-generation male adult rats fed control and FEDMF. The concentration and total content of cerebral DNA and number of neurons in males and females belonging to the first generation was similar. However, for second generation rats, these values were lower for animals fed regular tortilla diets. This data clearly demonstrates that the negative effects of malnutrition on brain development of pups occurred during gestation and lactation.
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