According to structure

The first requirement for threading is to have a database of all the known different protein folds. Eisenberg has used his own library of about 800 folds, which represents a minimally redundant set of the more than 6000 structures deposited at the Protein Data Bank. Other groups use databases available on the World Wide Web, where the folds are hierarchically ordered according to structural and functional similarities, such as SCOP, designed by Alexey Murzin and Cyrus Chothia in Cambridge, UK. 

The organization of Part Two is according to structural type. The first section, Chapter Seven, is concerned with the synthesis of macrocyclic compounds. Syntheses of a number of heterocyclic target structures appear in Chapter Eight. Sesquiterpenoids and polycyclic higher isoprenoids are dealt with in Chapters Nine and Ten, respectively. The remainder of Part Two describes syntheses of prostanoids (Chapter Eleven) and biologically active acyclic polyenes including leukotrienes and other eicosanoids (Chapter Twelve). 

Attempts to classify carbides according to structure or bond type meet the same difficulties as were encountered with hydrides (p. 64) and borides (p. 145) and for the same reasons. The general trends in properties of the three groups of compounds are, however, broadly similar, being most polar (ionic) for the electropositive metals, most covalent (molecular) for the electronegative non-metals and somewhat complex (interstitial) for the elements in the centre of the d block. There are also several elements with poorly characterized, unstable, or non-existent carbides, namely the later transition elements (Groups 11 and 12), the platinum metals, and the post transition-metal elements in Group 13. 

Rousseeuw [4]. Massart and Kaufman [5] and Bratchell [6] wrote specifically for chemometricians. Massart and Kaufman s book contains many examples, relevant to chemometrics, including the meteorite example [7]. More recent examples concern classification, for instance according to structural descriptions for toxicity testing [8] or in connection with combinatorial chemistry [9], according to chemical... 

FIGURE 50. Molecular structure of the alkinylborate anion-triorganolead cation complex according to structure A (Figure 49) with R = -Pr and R1 = Me. Reproduced from Reference 153 by permission of VCH Verlagsgesellschaft mbH... 

The oxazoline-derived P,N ligands can be classified into four groups according to structure phosphino-oxazolines phosphite- and phosphinite-oxazolines catalysts containing a P-N bond and structurally related non-oxazoline catalysts. 

The worldwide consumption of major surfactants classified according to structural type for 1998 is summarised in Table 1.9, with the breakdown by final use and geographical areas shown in Table 1.10. 

According to structural criteria, in particular, to the SINDOl-calculated (90JPC4467) values of RCI, the excited states of pyridine, as distinct from the ground state, do not possess aromatic character. This finding confirms the aromaticity antiaromaticity (nonaromaticity) inversion in the excited state relative to the ground state. 

As regards the second topic, namely that of phenylpropanoid reactions within plant cell walls, a more comprehensive discussion is possible and also timely, due to the recent increase in interest in this area. For the purpose of this review, the phenylpropanoids present in plant cell walls are first classified according to structural complexity (monomers, dimers, polymers, etc.), following which their main reactions are discussed. 

In the following we have broadly divided the available C(l) nucleophiles according to structure and reactivity. C(l)-Nucleophiles based on metallation at an sp -center are categorized in terms of the presence and, as appropriate, the nature of a hetero atom (O or N) substituent at C(2). C(l)-Lithiated glycals correspond to nucleophilic sp -centers, and variations on this theme (concerning the nature of the metal component) are covered in depth. 

We have described some of the general characteristics of polymers, and how they can be grouped according to structure, but we have not addressed any of the more quantitative aspects of polymer structures. For instance, we have stated that a polymer is made up of many monomer (repeat) units, but how many of these repeat units do we typically find in a polymer Do all polymer chains have the same number of repeat units These topics are addressed in this section on polymer molecular weight. Again, the kinetics of polymer formation are not discussed until Chapter 3—we merely assume here that the polymer chains have been formed and that we can count the number of repeat units in each chain. 

The nosology for CYP enzymes involves grouping into families and subfamilies according to structural similarity. All CYP enzymes in the same family have at least 40% structural similarity, and those in the same subfamily have at least 60% structural similarity. The family is designated by the first Arabic number, the subfamily by an alphabetic letter, and the trailing Arabic number designates the gene that codes for a specific CYP enzyme (10, 35, 51). 

According to structural indices AN and I, the aromaticity of non-condensed heterocycles varies in the sequence thiophene > pyrrole selenophene > tellurophene > furan. 

ABSTRACT This chapter provides a comprehensive overview of the sulfur-containing natural products that are non-sulfated and have been isolated from marine organisms. The overview covers the published literature from 1985 to 1999. A total of 482 compounds and 371 references are recorded. These secondary metabolites are organized in sections according to structural classifications by sulfur functional groups and by structural families of compounds. Comments on structural characterization, biogenesis, and biological activity have also been included. 

Saturated hydrocarbons were examined with a CEC-21-110B mass spectrometer. The standard ASTM method (19) was used to classify compounds according to structure. 

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