Simplifications, unexpected

Computational modeling is a powerful tool to predict toxicity of drugs and environmental toxins. However, all the in silico models, from the chemical structure-related QSAR method to the systemic PBPK models, would beneht from a second system to improve and validate their predictions. The accuracy of PBPK modeling, for example, depends on precise description of physiological mechanisms and kinetic parameters applied to the model. The PBPK method has primary limitations that it can only predict responses based on assumed mechanisms, without considerations on secondary and unexpected effects. Incomplete understanding of the biological mechanism and inappropriate simplification of the model can easily introduce errors into the PBPK predictions. In addition values of parameters required for the model are often unavailable, especially those for new drugs and environmental toxins. Thus a second validation system is critical to complement computational simulations and to provide a rational basis to improve mathematical models. 

Part of our sense of dissatisfaction comes from some unexpected simplifications in the f analysis, which indicate - or at least strongly suggest - that some unknown structure in the analysis is being overlooked. For example, the energy spacings between terms of maximum multiplicity, which can be found very easily from eqs. (21)-(25), are all simple multiples of the single linear combination... 

Once the idea of quasi-spin had been introduced, it did not take long for all kinds of properties to be put in perspective. For example, Racah s observation that every W occurs in the f shell with two pairs (S, i i) and (S2,V2) turns out to correspond to a spin-quasi-spin pair (Si,Qi) and its companion (S2,02) for which S2 = Qi and Q2 = Si. Other properties of the spin-quasi-spin interchange have recently been developed to explain, among other things, the inversion of the octets and sextets of P compared to the terms of corresponding L in P (Judd et al. 1986). Similar methods can be used to account for some of the properties of 2 mentioned in section 11, note (a), above. However, not all of the unexpected simplifications listed in section 11 yield to this approach. 

At least as far as the halides are concerned the model is internally consistent and, considering the gross over-simplification and approximations involved, appears to be a promising approach and will it is hoped stimulate further structural studies of these gels. In the case of the non-electrolytes, 1-pentanol, 1-hexanol (data not shown) and isomaltose, although the predicted values exhibited the same trend as the observed values, the fit was not so good as with the halides (Fig 5). This is perhaps not so unexpected as these non-electrolytes are much more complicated structures than simple ions. Further, in the quasineutral gel anion behaviour is not complicated by ion exchange. 

The described protein matrix-assisted inorganic synthesis provides an interesting pathway for the formation of novel hetero metal containing clusters. A particular interestet in this field arises from the possibility of forming new biocataiysts with unexpected properties. Also the introduction of a differentiated site into a cubane-type structure with intrinsic properties enables to explore magnetism in vaience - deiocalized /locaiized systems as well as the simplification of the spectral analysis. Synthesis of reievant modei compounds via the formation of hetero metal cubane-type... 

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