Hypothesized structure

The trend toward decreased stability of compounds with increased lipophilicity and MW is obvious. This analysis can provide information about the roles of these two properties in contributing to clearance for this series. Again, the important question for hit triage decision making is how the hypothesized structure-clearance trends correlate to the property trends for other relevant biological properties. 

Much discussion about the photo-formation of the merocyanines is based on the possibility of four stable merocyanine isomers that are trans about the 13-bond on the methine bridge. Commonly, these are referred to as TTC, CTT, CTC, and TTT [6-8,28,36] and they are shown in Scheme 4. Note that these are possible or hypothesized structures. Corner et al. even suggest that isomers cis about the central 3-methine bond may have stability and equilibrate with the more planar isomers [14,46-51]. Certainly, the four isomers cis about the cental (3-methine bond could have transient stability. 

Bands are observed in the IR and Raman spectra of a molecule that correspond to normal modes of vibration of that particular structure. These normal modes can be calculated from knowledge of the three-dimensional structure of the molecule and of its vibrational force field. If a reliable force field is available, it is therefore possible to predict the vibrational frequencies of a known or hypothesized structure, and to draw significant structural conclusions on the basis of comparisons with observed IR and Raman bands. 

Figure 23 Hypothesized structure of the [Zn"(16)(trp)] adduct. Tryptophane (trp) is recognized by the Zn" tetramine receptor through (i) the formation of a metal-carboxylate coordinative bond (ii) the establishing of 7t-stacking interactions between the aromatic part of the amino acid and one of the facing polyaromatic substituents of the tripodal tetramine framework.

Much effort has been expended on the formulation of more quantitative approaches, including the deduction of precise distances, bond angles, conformations, and potential energy surfaces for internal motions. These approaches may rely on a priori calculation of expected spectral parameters from hypothesized structures, or empirical correla-... 

Comparison of parameters obtained with those calculated theoretically for hypothesized structures or with those observed in analogous compounds of known structure. 

Normal spectroscopic practice is to compare the observed parameters with those predicted from hypothesized structures. The a priori calculation of shifts and coupling constants for moderately complicated molecules is extremely difficult. Great advances have been made in the past... 

N aniline was used in a study of the reactions of aniline with humic and fulvic acids (Thorn et al. 1996), and the detection of resonances attributed to anilinoquinone, imines, and N-heterocyclic compounds are fully consistent with the foregoing hypotheses. Structures in which phenols are covalently linked to C3-guaiacyl residues have been examined as models for interaction between chlorophenols and lignin residues in humic acids (Zitzelsberger et al. 1987). 

Figure 9.16. Hypothesized structure (top) of a data matrix, X, as a bilinear model plus offsets constant over all elements. Centering by subtracting the grand mean of X (bottom) will not remove the offsets from the data. The scalar m holds the grand average of X.

Of the most recent of these constructs (15, 74-77)], structure 5 is particularly interesting. It is intended to represent a typical monomeric fragment of the macromolecule of a vitrinite-rich bituminous coal with 83-84% carbon, and is the first to embody a recognition that hypothesized structural elements must be reconciled with their known or suspected antecedents in living plants as well as with observations on coal itself. Structure 5 therefore... 

The set of methods currently used for characterization provides a set of strong inferences that can help to prove or disprove a hypothesized structure for an aggregate. They do not provide the type of unambiguous proof of structure on which much of organic chemistry is built, and the development of new techniques for the characterization of non-covalent aggregates would be a welcome and useful addition to the field. 

The mechanism of action of this drug is still under investigation. It has been postulated that the antiproliferative effect could be related to the inhibition exerted by SIBA on tRNA methyla-ses °, on protein methylase I and on S—adenosylhomocysteine hydrolase. These studies have been performed in view of a hypothesized structural similarity between SIBA and Ado-Hcy (see Fig. 11). 

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