Classification molecular-based

Two very similar molecules are two different physical objects [40], Hence, chemical/ structural comparison of similarity is a subtle and relative concept that acquires significance in a well-defined reference physical context. In other words, it is necessary to define in what respect and to what extent two different molecules are similar. Molecular series of specific and selective ligands interacting, in vitro and in equilibrium conditions, with a specific receptor constitute a sophisticated example of chemical similarity-diversity classification. This classification is based on the experimental binding affinity (AG°) values that quantify a particular molecular recognition phenomenon, which is, essentially, a noncovalent process [41]. This implies,... 

Photochemical reactions of organic substrates with molecular oxygen have been extensively studied, with respect to both their preparative and mechanistic aspects. This article will be restricted to a certain type of these reactions which we may call type II (direct and indirect) photooxygenation reactions in solution. This classification is based on the following definitions. 

In this respect, a classification was reported whose basis is the nature of ligands together with the characteristic bonding and structural peculiarities of the metal complexes [112,113], This allowed the identification of four types of coordination compounds molecular complex compounds (MCC) metal-cyclic complex compounds, metal chelates (MC) complexes with multicenter coordination bonds (CMCB) and di- and polynuclear coordination compounds (DPCC). The expediency of such a classification is based on the following considerations. 

These classifications are based on the density difference between the released material and its surrounding medium (air). The classifications are influenced by release temperature, molecular weight, presence of aerosols, ambient temperature at release, and relative humidity. 

During natural evolution, a broad variety of enzymes has been developed, which are classified according to the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (IUBMB). Thus, for each type of characterized enzyme an EC (Enzyme Commission) number has been provided (see http // www.expasy.ch/enzyme/). For instance, all hydrolases have EC number 3 and further subdivisions are provided by three additional digits, e.g. all lipases (official name triacylglycerol lipases) have the EC number 3.1.1.3 and are thus distinguished from esterases (official name carboxyl esterases) having the EC number 3.1.1.1. This classification is based on the substrate (and cofactor) specificity of an enzyme only, however often very similar amino acid sequences and also related three-dimensional structures can be observed. 

From a practical standpoint, it is useful to have a classification scheme based on molecular formulas rather than parent polyhedra (which may not immediately be obvious). In addition, such a classification scheme should ideally be adaptable to other clusters, whether or not they involve the element boron. Here is one such scheme. 

Chemists have adopted from mathematicians a way of classifying molecules according to their symmetry. The classification is based on the idea that if a molecule is sufficiently symmetrical, then an action can be found that will leave the molecule looking the same as it did when you started. You have already met two such actions inversion through a centre of symmetry and rotation about the molecular axis of a diatomic molecule. Actions such as this are called symmetry operations, and a molecule can be placed in a category according to how many such operations you can perform and still leave the molecule looking the same. 

Identification of the primary anatomical site of tumor origin is very important for proper treatment of cancer of unknown origin. It is estimated that 4% of cancer patients present with metastatic tumors for which the origin of the primary tumor has not been determined [55]. To address this issue, Su et al. developed a multiclass molecular classification scheme based on genes whose expression was specific to tumor tissues of each anatomical site. The classifier showed 85% accuracy on test set predictions and 75% accuracy on metastasis sample predictions. Of note, an 11-gene classifier could predict the anatomical origin of up to 91% and 83% of the training and blinded tumor samples, respectively [56]. 

Another classification is based on the mechanical behaviour of the material as a function of temperature. This feature is associated with the molecular structure of the polymeric ingredient. 

We attempted to integrate the proposed classification system based on stmctural parameters (molecular simplexes). A classification tree was constmcted (Fig. 14.5) and could be used to correctly classify the whole set of benzodiazepines using only four stmctural parameters (S2, S5, S7, S76). 

Describe (i.e., give a schematic diagram) a classification system based on molecular characteristics, structure and isomeric states. 

Progress in molecular biology provides new classification criteria based on genome analysis. Molecular taxonomy consist of classifying bacteria according to similarities in their genome. Diverse methods exist, permitting several levels of classification. 

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