Search for structure

The search for structural fragments (substructures) is very important in medicinal chemistry, QSAR, spectroscopy, and many other fields in the process of perception of pharmacophore, chromophore, or other -phores. 

Smith, C.S. (1952, 1981) Grain shapes and other metallurgical applications of topology, in Metal Interfaces, ASM Seminar Report (American Society for Metals, Cleveland) p. 65. Grain shapes and other metallurgical applications of topology, in A Search for Structure, ed. Smith, C.S. (MIT Press, Cambridge, MA) p. 3. 

Sonquist, J., et ai, Searching for Structure. University of Michigan, Ann Arbor, Michigan, 1971. 

Baumann, K., Clerc, J. T. Computer-assisted IR spectra prediction - linked similarity searches for structures and spectra. Anal. Chim. Acta 1997, 348, 327-343. 

Savarese TM, Fraser CM. In vitro mutagenesis and the search for structure-function relationships among G protein-coupled receptors. Biochem J 1992 283 1-19. 

The scope for further developments in the chemistry of seven-membered heterocyclic systems is considerable, particularly with respect to multi-heteroatom component systems. New synthetic methods are needed for these systems and ring-fused derivatives. The demand for such systems is likely to be largely driven by the search for structurally novel drug leads. 

In the search for structural diversity, and novel therapeutic agents, unique ring structures like the 1,2,5-thiadiazole have always captured the imagination of chemists. Often, as in the case of timolol (4), the interest is rewarded. In the early 1990s, a simple thiadiazole was appended to a penem in the development of the structure-activity relationships for a series of ) -lactamase inhibitors. The result was enhanced penetration of the bacterial membrane and a broader spectrum of activity versus clavulanic acid <9lJAN33l>. 

C.S. Smith. Grain shapes and other metallurgical applications of topology. In A Search for Structure, pages 17-25, Cambridge, MA, 1981. MIT Press. 

Structure and Nomenclature Search System. This system links the collection of chemical databases found in the Chemical Information System (CIS), one of the first interactive systems for structure and substructure searching. References from the separate files can be retrieved by SANSS using CAS Registry Numbers, and the database of structures may be searched for structures or substructures. An adaptation of the SANSS software for substructure searching has been incorporated in the Dmg Information System of the National Cancer Institute for its own use (54). 

The search for structures able to be used as storage facilities differs from, and in a way is more complex than, the search for hydrocarbon deposits. In fact, just because a well has indicated a good, suitably covered reservoir does not mean that the structure is appropriate for storage purposes. It is necessary to prove that the gas to be stored there will not escape and therefore ensure the caprock s continuity and the closure of the structure. 

The presence of the regular repeated structure regions in proteins permits the comparison of their structural characteristics that display common features. A search for structural similarity of proteins can be processed at various levels of complexity depending upon the field of application. Two approaches are considered in the similarity comparison of protein sequences ... 

In the case of the HMO model the success of the search for structure-property relations is much enhanced by the possibility of applying the powerful mathematical apparatus of graph-spectral theory [18, 19]. There is hardly any application of graph (spectral) theory in more sophisticated molecular orbital models. 

In the first naive attempt a search for structures of compounds containing N—C—C grouping without any constraints on bond types or number of substituents at N and C atoms gave a huge amount of 7481 structures. This result prompted us to eliminate such formally enamine-like compounds as porphyrines, phthalocyanines, tetraazamacrocyclic compounds, purine and pyrimidine derivatives, as well as to formulate more precise conditions for selection of proper enamine groupings. To this end a new structural data retrieval from CSDS was performed in four stages. 

This discussion provides only an outline of the techniques that have been used to search for structure in compositional data matrices generated by the analysis of archaeological materials. Before many of the techniques are used, however, some pretreatment of the data may be necessary. 

The principal impetus to the study of zinc thiolates has undoubtedly been the search for structural models for the metal coordination in zinc metalloproteins such as the Zn(S-Cys)2(His)2 center in the transcription factor IIIA and other zinc fingers that feature in protein-DNA interactions (93, 94). The 2 1 complexes [M(SR)2l (M = Zn, Cd SR = TIPT, TEMT) were used as the principle precursors for the synthesis of such models for the Zn(S-Cys)2(His)2. Thus complexes of the types [Cd(TIPT)2(l-CH3-imid)2], [Zn(TIPT)2(bipy)], and [Zn(TEMT)2(l-CH3-imid)2l (imid = imidazole, bipy = bipyridine) were ssmthesized by addition of a nitrogeneous base to the precursor in MeCN. All of them have been characterized by X-ray crystallography and were found to have distorted tetrahedral geometries. It was noticed that the cobalt analogue binds a solvent molecule MeCN to form five-coordinate [Co(TIPT)2(bipy)(CH3CN)], whereas [Zn(TIPT)2(bipy)] does not 96,97). 

Hu ins (987, 988) 2-7-1 A zig-zag ribbon with R s opposite a two-residue spiral First extensive search for structures based on average distances and angles from simple molecules. Some were discussed as early as 1937 (see his footnote 2). Apparently, first suggestion of nonintegral spirals (p. 211) —not emphasized or pursued. 

The introduction of Valence Bond theory has motivated the search for structural regularities that can be interpreted by models of local electronic features, such as the powerful model of Valence Shell Electron Pair Repulsion [93,94] theory. Alternative approaches, based on Molecular Orbital theory, have led to the discovery of important rules, such as the Woodward-Hoffmann orbital symmetry rules [95] and the frontier orbital approach of Fukui [96,97], As a result of these advances and the spectacular successes of ab initio computations on molecular... 

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