On Uniform Representations of Molecules

As we have seen, there have been diverse approaches to the design of molecular codes, some of which had different specific goals in mind. Here we will outline one such approach which is aimed at a uniform representation of molecules. Good structure representations for modeling should fulfill the following demands [74]  

Each compound should have one and only one code, with different codes for different structures (uniqueness). 

Each compound should be represented by the same number and type of variables (uniformity). 

One should be able to retrieve the structure from the code (reversibility). 

Code should be independent of translation or rotation of a structure (translational and rotational invariance). 

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With this, we will end this section on uniform representations of molecules. As one can see, the spectral representation may vary with increased resolution. In Figure 2.17, one can easily delect 20 peaks and possibly two shoulders, but the total number of atoms in this molecule is 33, so about a dozen atomic centers overlap or are too close to the same projection lines to be sufficiently discriminated, but as already mentioned, molecular structures can always be reconstructed from the spectral representation. This is one of the important features showing that there is no loss of information accompanying spectral-like uniform representations of molecules. For more on spectral-like uniform representations of molecules one should consult references listed in this section. 

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