Molecular shape profiles

Randic, M. (1995b). Molecular Shape Profiles. J.Chem.Inf ComputScL, 35, 373-382. 

The stereochemistry of each enantiomer separated by the chiral HPLC has been studied after methanolysis of the epoxy ring. Examining the H NMR data of esters of the produced methoxyalcohols with (S)- and (R)-a-methoxy-a-(tri-fluoromethyl) phenylacetic acid by a modified Mosher s method [181], it has been indicated that the earlier eluting parent epoxides are (3S,4R)-, (6S,7R)-, and (9R,10S)-isomers (Table 7) [75, 76, 179]. The above three chiral HPLC columns show different resolution abilities but a different elution order is not observed. The resolution profile by the reversed-phase OJ-R column has been generalized with molecular shapes of the epoxy compounds considering the... 

As can be seen from Fig. 2, sila-substitution of rac-Sa (-> rac-Sh) substantially affects the pharmacological profile with respect to serotonin reuptake inhibition. The other (major) structural changes in the molecular shape of rac-5b (-> rac-6, rac-7) also influenced the pharmacological profile with respect to monoamine selectivity rac-1) and/or absolute potency rac-6). These results clearly demonstrate that the carbon/silicon switch strategy is a powerful tool for drug design. 

In this way, different types of profiOies can be derived, such as shape profiles, which are local profiles taking into account only atoms on the molecular periphery ... 

In the case of 3D space-filled molecular models, one can represent the molecule by contour profiles, which are shape profiles calculated for all individual contours used to map the molecule. Each contour profile is then defined by a sequence ... 

Several shape descriptors are defined within more general approaches to - molecular descriptors. This is the case of - Kier shape descriptors, -> shape profiles, -> shadow indices, -> WHIM shape descriptors, - Sterimol shape parameters L/Bj and B1/B5, molecular - periphery codes, and -> centric indices. Other approaches to the study of molecular surface and shape are Mezey 3D shape analysis and Hopfinger - molecular shape analysis. -> Triangular descriptors have also been used to characterize molecular shape to search for similarities among molecules. 

The release profiles suggest that the lysoPPC and PA hydrolysis products, which are formed in a 1 1 molar ratio by SPLA2, are incorporated into the target membranes [51], leading to the increase in the permeability of the target liposomal membranes. These hydrolysis products, due to their non-bilayer forming molecular shapes, induce a curvature stress [52, 53] and/or form small-scale lipid domains [33, 36], which lead to membrane defects and consequently increased membrane... 

Holte LL, Peter SA, Sinnwell TM. Gawrisch K. -H nuclear magnetic resonance order parameter profiles suggest a change of molecular shape for phosphatidylcholines containing a polyunsaturated acyl chain. Biophys J 1995 68 2396-2403. 

We will show that the interatomic distances and their powers offer a better characterization of molecular shapes. The shape of an object is defined by its exterior, surface, or contour in the case of 2D objects. Hence, when characterizing molecular shape one should consider only the interatomic separations between atoms at the molecular periphery, excluding atoms in the interior part of the structure. In the case of cflto-condensed benzenoids, all carbon atoms are on the periphery, hence the shape profile and the molecular profile of such compounds are the same. In the case of peri-condensed benzenoids, only carbon atoms at the periphery will be taken into account. 

We will consider a set of n = 16 benzenoid hydrocarbons for which an analysis of the gas Chromatographic retention indices Iff was reported. Among these thae are nine cato-condensed benzenoid hydrocarbons (illustrated in Figure 27) and seven / en-condensed benzenoids (of Figure 28) for which Chromatographic data were analyzed. In cato-condensed benzenoids all carbon atoms are on the molecular periphery, hence the shape profile and the molecular profile (based on all carbon atoms) are the same (Table 23). 

We want to discuss the differences of the characterization of benzenoid hydrocarbons by the molecular profiles and by the shape profiles. Let us consider pen-condensed benzenoids more closely. In Table 24 are listed for the selected peri-condensed benzenoids (illustrated in Figure 28) the numerical values for the molecular... 

It is instructive to compare the shape profiles of Table 26. The smallest profiles are found for pyrene (10), benzo(t/)pyrene (11), and peiylene (12), and the largest profiles appear to be those of benz(fl)pyrene (13) and anthanthrene (15). Why is this the case Why, for example, isn t the profile of coronene (16) the largest, when this molecule has the largest number of fused rings The answer is not difficult to find. The profile D does not directly depend on the molecular size, but on interatomic... 

Table 27. Comparison of the Regression Analysis Using the Shape Profile Descriptors 5 and Molecular Profile Descriptors D...

Several theories relating molecular properties to perceived odor quality have been advanced. Examples include the work of Wright (16,] ) who links odor quality to molecular vibrations in the far-infrared, and of Amoore (18) who links odor quality to molecular shape, size, and electronic nature and who introduced the concept of primary class. Beets (19) has discussed odor quality relative to molecular shape as represented by oriented profiles, chirality, and functional groups. In a recently published book (20) he has expanded these discussions. Theimer and coworkers (, , 23) have discussed the Importance of the molecular cross-sectional areas, free energies of desorption, and chirality in relation to odor. A discussion of musk odor quality and molecular structure has been presented by Teranishi (24). Laffort and coworkers ( ) have related odor quality to four molecular properties derived from gas chromatographic retention indices measured on four stationary phases. 

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