Likeness concept

Mendeleev s Use of Triad-Like Concepts To Make Predictions... 

Hann, M.M. and Oprea, T.I. Pursuing the lead likeness concept in pharmaceutical research. Curr. Opin. Chem. 

A Nordic project has evaluated how different TTC-like concepts have been used, and assessed their potential usability in risk assessment of industrial chemicals within REACH (NCM 2005). The Nordic group considered that if the TTC concept is appropriately derived and used, it might imply a better focus of chemicals at risk. However, it was also stated that, independent of the approach used in risk assessment of industrial chemicals, it is important to maintain a sufficient level of protection and that application of the TTC concept in REACH would imply that limited data may be generated and thus that the level of protection might be influenced. 

Owing to drug developability requirements, design criteria such as Lipinski s rules of 5 (16), Veber s rotatable bond rule (17), and drug-likeness concept... 

Figure 2.1 The evolution of the drug-likeness concept. Drug-likeness evolved from empirical rules such as Lipinski s rule of 5 through more sophisticated data mining algorithms into utilization of preclinical profiling and safety pharmacology data [3].

Leeson, P.D. and Springthorpe, B. (2007) The infiuence of drug-like concepts on decision-making in medicinal chemistry. Nature Reviews. Drug Discovery, 6, 881-890. 

The Feynman path integral formalism " in quantum mechanics has proven to be an important vehicle for studying the quantum properties of condensed matter, both conceptually and in computational studies. Various classical-like concepts may be more easily introduced and, in the case of equilibrium properties, the formalism provides apowerful computer simulation tool. 

Harm, M. M., Oprea, T. I. (2004) Pursuing the lead-likeness concept in pharma-... 

The results of these static measurements can then be used to rate the probable usefulness of different adsorbents. However, the isotherm results from static water solutions do not apply to dynamic column situations in which equilibrium conditions may not occur. A better approach is to generate frontal breakthrough curves that can then be used to estimate the use of different polymers for different solutes dissolved in water. Theoretical and experimental reports (97, 143, 181, 286, 319-321, 537) discuss details about affinity measurements. These details are not included in this review because affinity is discussed only qualitatively in the sections on Theoretical Considerations and Generalized Methodology. These qualitative discussions suggest that neutral polymers such as the styrene-divinylbenzenes are efficient for adsorbing neutral hydrophobic solutes from water solutions but have little affinity for polar and ionic solutes. If the polarity of the polymer is increased to that of the acrylates, the affinity for neutral hydrophobic components will suffer but the more polar solutes will be better adsorbed. In the absence of actual test results under dynamic column flow conditions, the simple likes adsorb likes concept is invoked. 

Central to the stability and chemistry of complexes formed by mixed donor ligands are two key concepts of coordination chemistry. The first is the chelate effect, which applies to all polydentate ligands, and reflects the increase in stability of a type of complex as monodentate donor molecnles are replaced by polydentates with donors linked by chelate rings. The hard-soft acid-base theory is particnlarly relevant to mixed donor ligands where donors of distinctly different character may bind to a central metal ion. The like prefers like concept means hard nonpolarizable donor atoms (N and O, for example) bond preferentially to hard nonpolarizable metal... 

At the present time, the most likely concept of the mechanism of a heterogeneous polymerization catalyzed by a Ziegler-Natta catalyst involves a complex in which the organometallic component and the transition metal component—i.e., the A1 and Ti atoms—are joined by electron-deficient bonds. Natta, Corradini, and Bassi (13) have reported such a structure for the active catalyst prepared from bis (cyclopentadienyl) titanium dichloride and aluminum triethyl. Natta and Pasquon (14), Patat and Sinn (18), and Furukawa and Tsuruta (2) have proposed mechanisms for the stereospecific polymerization of a-olefins in terms of such electron-deficient complexes. 

Figure 2.13. Mierofibrils in the secondary wall, visualized using a trellis-like concept with inset of the tangential-longitudinal face in the S2 layer (Harrington, 2002). There is a broad distribution of microfihril angles about the mean. Most literature only quote the mean value.

Theobald characterizes a number of chemical concepts, including molecule, reactivity, equilibrium and transition state as "static, organizing, descriptive." He sees them as "more like concepts in biology than the dynamic causal concepts of so much of physics" (Theobald, 1976, p. 209). Theobald s view of physics seems to be diametrically opposed to that of Denbigh (1981, p. 6). This disjunction raises interesting questions about whether any science is inherently "static" or "dynamic," and the extent to which these (admittedly vague) attributes are context dependent. 

The studies on lead molecules and their optimisation are consistent with each other and together provide strong support for the lead-like concept as a central contributing component in achieving ultimate optimization success. The average changes in mol. wt and cLogP are consistent and in these studies are... 

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