Similarity molecular structure

Contrera JF, Matthews EJ, Benz RD. Predicting the carcinogenic potential of pharmaceuticals in rodents using molecular structural similarity and E-state indices. Regul Toxicol Pharmacol 2003 38 243-59. 

Smooth muscles have molecular structures similar to those in striated muscle, but the sarcomeres are not aligned so as to generate the striated appearance. Smooth muscles contain a-actinin and tropomyosin molecules, as do skeletal muscles. They do not have the troponin system, and the fight chains of smooth muscle myosin molecules differ from those of striated muscle myosin. Regulation of smooth muscle contraction is myosin-based, unlike striated muscle, which is actin-based. However, like striated muscle, smooth muscle contraction is regulated by Ca. ... 

P. Willett and V. Winterman, A comparison of some measures for the determination of inter-molecular structural similarity. Measures of inter-molecular structural similarity. Quant. Struct.- Act. Relat., 5 (1986) 18-25. 

Plotting 1/V versus 1/[S], one obtains a straight line having a slope of Km/Vmax with a y-axis intercept of l/VmAX and an x-intercept of - 1/Km as shown in Figure 2.13. Lineweaver-Burk plots of enzyme activity in the presence of an inhibitor can distinguish the type of inhibitor. Competitive inhibitors have a molecular structure similar to that of the substrate and will alter Km but not VnrAX because they compete with the substrate for binding at the enzyme s active site but do not change the enzyme s affinity for substrate. Noncompetitive inhibitors bear no structural similarity to the substrate but bind the free enzyme or enzyme-substrate... 

The concept of the similarity of molecules has important ramifications for physical, chemical, and biological systems. Grunwald (7) has recently pointed out the constraints of molecular similarity on linear free energy relations and observed that Their accuracy depends upon the quality of the molecular similarity. The use of quantitative structure-activity relationships (2-6) is based on the assumption that similar molecules have similar properties. Herein we present a general and rigorous definition of molecular structural similarity. Previous research in this field has usually been concerned with sequence comparisons of macromolecules, primarily proteins and nucleic acids (7-9). In addition, there have appeared a number of ad hoc definitions of molecular similarity (10-15), many of which are subsumed in the present work. Difficulties associated with attempting to obtain precise numerical indices for qualitative molecular structural concepts have already been extensively discussed in the literature and will not be reviewed here. 

A molecular structure, similar to that of hexasilylated benzene derivative 229, was obtained from tetracyclic hexasilylbenzene 230 by Kira, Sakurai and coworkers, where the six silicon centres are incorporated in three five-membered ring systems (Scheme 80) °. In dimetalated compound 231, two lithium centres, coordinated by a quinuclidine ligand each, are capping the phenyl ring plane from both sides in the solid state. Moreover, it could be found that compound 231 has a thermally accessible triplet state, investigated by temperature-dependent ESR spectroscopy °°. 

Zidovudine (ZDV or AZT) is a nucleoside reverse transcriptase inhibitor (NRTI) and it was the first anti-HIV agent to be introduced. Other NRTIs include stavudine (d4T), lamivudine (3TC), didano-sine (ddl), abacavir (ABC) and zalcitabine (ddC). Recent additions to this class are emtricitabine (FTC) which has a molecular structure similar to 3TC and tenofovir (TDF) a nucleotide reverse transcriptase inhibitor. 

Compounds with molecular structures similar to those of the repeating units are called model compounds, and much information about the properties of polymecs may be derived from knowledge of these model compounds. Thus, a person who knows the chemical properties of ethane can fairly well extrapolate this to the chemistry of hdpe. Of course, the physical and thermal properties of hdpe are much different from those of ethane. 

Chitosan Chitosan has a molecular structure similar to cellulose. This material is produced from chitin, which is widely found in the exoskeleton of shellfish and crustaceans. Chitin is the second most abundant natural biopolymer after cellulose. Chitosan is a good adsorbent for all heavy metals. It has been estimated that chitosan can be produced from shellfish and crustaceans at a market price of 15.43 /kg. 

Drags which have structures similar to that of endogenous nutrients may be taken up by a specialized transport system (carrier-mediated transport, receptor-mediated transcytosis) existing in the brain endothelium for nutrients. For example, drags having a molecular structure similar to a large neutral amino acid may cross the BBB via the neutral amino acid carrier such drags include melphalan (phenylalanine mustard), L-dopa, a-methyldopa, and p-chlorophenylalanine. 

As discussed above, certain nutrients are taken up into the brain by carrier-mediated systems. If a dmg possesses a molecular structure similar to that of a nutrient which is a substrate for carrier-mediated transport (Table 13.1), the pseudo-nutrient dmg may be transported across the BBB by the appropriate carrier-mediated system. For example, the dmg L-dopa crosses the BBB via the neutral amino acid carrier system. Other neutral amino acid dmgs that are transported through the BBB on this transport system are a-methyldopa, a-methylparatyrosine, and phenylalanine mustard. 

The adverse reaction potential of an investigational new drug, to some extent, may be indicated by its molecular structural similarities to other drugs of known actions and by pharmacologic and toxicologic preclinical studies in appropriate species of laboratory animals. The full adverse reaction profile of a drug, how-... 

First, the current state of affairs is remarkably similar to that of the field of computational molecular dynamics 40 years ago. While the basic equations are known in principle (as we shall see), the large number of unknown parameters makes realistic simulations essentially impossible. The parameters in molecular dynamics represent the force field to which Newton s equation is applied the parameters in the CME are the rate constants. (Accepted sets of parameters for molecular dynamics are based on many years of continuous development and checking predictions with experimental measurements.) In current applications molecular dynamics is used to identify functional conformational states of macromolecules, i.e., free energy minima, from the entire ensemble of possible molecular structures. Similarly, one of the important goals of analyzing the CME is to identify functional states of areaction network from the entire ensemble of potential concentration states. These functional states are associated with the maxima in the steady state probability distribution function p(n i, no, , hn). In both the cases of molecular dynamics and the CME applied to non-trivial systems it is rarely feasible to enumerate all possible states to choose the most probable. Instead, simulations are used to intelligently and realistically sample the state space. 

Willett, P. and Winterman, V. A Comparison of Some Measures for the Determination of Inter-Molecular Structural Similarity. QSAR, 1986, 5, 18-25. 

Ketamine is a compound with a molecular structure similar to that of phencyclidine (Figure 4.2). The pharmaceutical versions of ketamine are clear, colorless liquids available in varying concentrations of 10,50, and 100 milligram/milliliter solutions (Figure 4.3). Many recreational users inject this liquid intramuscularly or intravenously. It is the liquid formulation that is used as a date rape drug. Liquid ketamine, which is clear and colorless, can easily be slipped into a drink without being detected. 

In the following, we shall attempt to obtain better estimate for oc, and thus for B, and point out the experimental difficulties inherent in such an endeavor. The estimates for B and fg so obtained wiU be examined for any discernible dependence on molecular structure. Similar studies of the Vogel equation for isolated systems have been undertaken by Williams (223) and more recently by Miller 153, 154, 155, 156). 

With molecular structures similar to the MEH-PPV CN-PPV system, the intensively studied M3EH-PPV CN-ether-PPV system—either as a blend or as a bilayer—resulted more recently in higher efficiencies under full AM 1.5 illumination (lOOmW/cm ) (Fig. 46) [35,223-225]. The first blend devices incorporated either a flat sintered titanium dioxide (Ti02) or a PEDOT PSS interlayer at the ITO interface. Blend devices with PEDOTiPSS and Ca electrodes led to power conversion efficiencies of 1% and EQEs of up to 23%. 

Fujiwara and Fukumori, 1996). Nitric oxide reductase is also known, which lacks heme C and uses quinol as the electron donor (Suharti et al., 2001 de Vries et al., 2003). The cytochrome ebb-type enzyme has a molecular structure similar to the structure of the Cub binding portion in cytochrome c oxidase (Saraste and Castresana, 1994 Van der Oost et al., 1994 Zumft et al., 1994). Moreover, quinol NO reductase from Bacillus azotoformans is known to contain Cua. Nitrous oxide is further reduced to nitrogen gas (N2) by the catalysis of nitrous oxide reductase (N20 reductase) which is a multi-copper protein (Zumft and Matsubara, 1982). The structure of the copper-binding portion in the enzyme has been reported also to be similar to the structure of the Cua binding portion of cytochrome c oxidase (Chamock et al., 2000). 

Ethylbenzene (eth-il-BEN-zeen) is a colorless flammable liquid with a pleasant aromatic odor. It is an aromatic hydrocarbon, that is, a compound consisting of carbon and hydrogen only with a molecular structure similar to that of benzene (C6H6). In 3004 it ranked fifteenth among chemicals produced in the United States. Its primary use is in the manufacture of another aromatic hydrocarbon, styrene (C6HSCH=CH2), widely used to make a number of polymers, such as polystyrene, styrene-butadiene latex, SBR rubber, and ABS rubber. 

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