Fragment substructure

Lines 4—18 form the connection table (Ctah), containing the description of the collection of atoms constituting the given compound, which can be wholly or partially connected by bonds. Such a collection can represent molecules, molecular fragments, substructures, substituent groups, and so on. In case of a Molfile, the Ctah block describes a single molecule. 

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. 

Atom and bond fragments Substructures (atom groups) Substructure environment Number of carbon atoms Number of rings (In polycyclic compounds) Molecular connectivity (extent of branching)... 

Assemble fragments/substructures from different, known homologous structures. 

A molecular structure can be encoded in terms of its fragments (substructures). In this representation an individual element of a representation vector shows the presence or absence of a particular fragment [ 10]. 

Clark M. Generalized fragment-substructure based property prediction method. I Chem Inf Model 2005 45 30-8. 

Assemble fragments/substructures from different, known homologous structures. Overlapping the main-chains of the target protein and the structure of the closely related protein of known structure. 

The 12-digit Code. To illustrate this procedure, let us look at the example used above in Fig. 2 the structure is input, and the operation of the Beilstein System on the connection table is then carried out- The structure is recognised as being composed of three fragments (substructures), namely ... 

A set of 160 barbiturates was coded using 46 molecular descriptors, including fragments, substructures, environmental descriptors, and a molecular connectivity index C287, 288, 2921. Classifiers were developed with a learning machine that recognizes the duration of the depressant effect- Predictive abilities of 94 % were reported for correct classifications of the duration time "less than t minutes". 

Much research has been done into similarity searching, and it is often assumed that diversity, or dissimilarity, is the converse (i.e, 1 — similarity). Any similarity measure involves three main components the structural descriptors that are used to characterize the molecules, the weighting scheme used to differentiate important from less important characteristics, and the similarity coefficient that is used to quantify the degree of similarity between pairs of molecules. Three types of descriptor have been used fragment substructures, topological indexes, and global physical properties. One of the most common similarity coefficients is that due to Tanimoto. There are three main methods of compound selection cluster-based, dissimilarity-based, and partition-based. 

Three main types of similarity measure have been used for quantifying the degree of resemblance between pairs of 2D chemical structures, these measures being based upon fragment substructures, topological indices, or maximal common subgraph (MCS) isomorphism algorithms. 

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