Topographical similarity

Chemical Space. A loosely defined concept that all the known or possible chemical structures define some multidimensional syace in which the structures are points. Structures that are topologically or topographically similar to each other (i.e., look similar), cluster in chemical space, and by the principle of chemical similarity, should show similar physicochemical and biological properties. This is the basis for diversity analysis of chemical libraries. The challenge is to select or discover properties of the structures that define the chemical space and can be used. 

Table 12-14 shows several dibenzazepines. Of the two dibenzoxazepines (where X = O) loxapine, marketed in 1975, is antipsychotic. The topographical similarity of this tricyclic antipsychotic to the others may be appreciated when viewed as presented in Table 12-15. Its pharmacology, including side effects, mimics those of the phenothiazines as well as...

Therefore the sites for the bond shift and cyclic mechanisms must be topographically similar, located either both on the face or both on the edge of the metal particles. Since isomerization also takes place on very dispersed catalysts (a >0.5), when edge atoms predominate, we may conclude that both types of isomerization sites include edge atoms. 

It is noted that backing the Knoxville frequencies by 60 would result in the maxima occurring together. This is tabulated in the fifth column of Table 21-6. The difference between Nashville and this artificial frequency is then obtained (the sixth column). The sum of the absolute values of the differences expressed as a percentage of the total is 30.2 the differences have been reduced by more than half. This does not prove that the frequencies are similar except that the winds at Knoxville are channeled by the major topographical features in the vicinity, but it does imply that this is an explanation. 

A similar concern due to lateral motion also applies to purely qualitative imaging. Sugisaki et al. [38] observed an artifact in their simultaneously topographic and adhesion... 

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