What is topological descriptor?
Topological indices (TIs) are two-dimensional descriptors which take into account the internal atomic arrangement of compounds, and which encode in numerical form information about molecular size, shape, branching, presence of heteroatoms and multiple bonds.
What is a descriptor in QSAR?
Descriptors are the chemical characteristic of a molecule in numerical form, used for QSAR/QSPR studies.
How do I select QSAR descriptors?
Descriptors must be chosen in order to be as few as possible (generally for QSAR you should have maximum 1 descriptor every 5 molecules, better if more, of the training set,) and need to be uncorrelated between them.
Which is a molecular descriptor for QSAR?
A molecular descriptor is a structural or physicochemical property of a molecule or part of a molecule. A QSAR model for predictive toxicology is a mathematical relationship between a chemical’s quantitative molecular descriptors and its toxicological endpoint [9,44].
How many topological indices are there?
Since then, over 3000 topological graph indices are registered in Chemical Data Bases. This research area is studied by mathematicians and chemists.
What is distance topological indices?
A topological index is said to be distance-based if its computation involves distance between vertices. Recently, the exact value of some distance-based topological indices namely Wiener, hyper-Wiener, and Schultz molecular topological index of the circulant network Cn(1, a) for a = 2, 3, 4, and 5 were computed.
What are 1D 2D and 3D descriptors?
The main classes of theoretical molecular descriptors are: 1) 0D-descriptors (i.e. constitutional descriptors, count descriptors), 2) 1D-descriptors (i.e. list of structural fragments, fingerprints),3) 2D-descriptors (i.e. graph invariants),4) 3D-descriptors (such as, for example, 3D-MoRSE descriptors, WHIM descriptors …
What are molecular descriptors and fingerprints?
Fingerprints or descriptors are an abstract representation of certain structural features of a molecule. These descriptors may represent a structural key within a molecule. This might be as simple as a count of a particular atom type, S, N etc, or halogen, or sp3.
What is virtual screening in drug discovery?
Virtual screening (VS) is a computational technique used in drug discovery to search libraries of small molecules in order to identify those structures which are most likely to bind to a drug target, typically a protein receptor or enzyme.
What are topological indices in graph theory?
A topological graph index, also called a molecular descriptor, is a mathematical formula that can be applied to any graph which models some molecular structure. From this index, it is possible to analyse mathematical values and further investigate some physicochemical properties of a molecule.
What are descriptors in chemistry?
A descriptor is in chemical nomenclature a prefix placed before the systematic substance name, which describes the configuration or the stereochemistry of the molecule.