Isomer discrimination

De Silva and Mabury [120] investigated the isomer distribution of PFCAs inhuman blood and observed linear isomers of PFCAs to be predominant. This observation is suggestive that organisms are more exposed to a linear source of PFCAs, such as linear FTOHs produced by the telomerization process [120]. It is important to note that isomeric distribution of PFCAs cannot yet provide conclusive evidence with regards to source, as PFCA isomer discrimination in biological samples is not yet fully understood. For example, it is possible that linear isomers are preferentially absorbed and/or branched isomers are more readily eliminated [120, 147]. Additional biomonitoring studies are required to characterize trends of human exposure better. 

Summons R. E. (1987) Branched alkanes from ancient and modern sediments isomer discrimination by GC/MS with multiple reaction monitoring. Org. Geochem. 11, 281-289. 

Bonchev, D., Mekenyan, O. and Trinajstic, N. (1981b). Isomer Discrimination by Topological Information Approach. J.Comput.Chem., 2,127-148. 

ST Fountain, DM Lubman. Wavelength-specific resonance enhanced multiphoton ionization for isomer discrimination via fragmentation and metastable analysis. Anal Chem 65 1257—1266, 1993. 

Electrochemical methods provide information on the coexistence of different topological redox isomers. Discrimination between different redox isomers can... 

Isomer Discrimination is the property of a molecular descriptor to distinguish between structural isomers. Ideally, this property is configurable. 

This equation is statistically significant at the 99.9% level, and the indexes are individually significant at the 99.95 and 95% level, respectively. The index gives good account of the dependence of on size, and the " X k index provides proper isomer discrimination. 

This equation is statistically significant at the 99.9% level the indexes are significant at the 99.95% level. The size of the benzenes is encoded in the index, whereas the isomer discrimination is in the Xc.h index, which is based on toluene-like skeletal fragments. 

An E-Z discrimination between isomeric oxaziridines (27) was made by NMR data (69JCS(C)2650). The methyl groups of the isopropyl side chains in the compounds (27) are nonequivalent due to the neighboring carbon and nitrogen centres of asymmetry and possibly due to restricted rotation around the exocyclic C—N bond in the case of the Z isomer. The chemical shift of a methyl group in (Z)-(27) appears at extraordinarily high field, an effect probably due to the anisotropic effect of the p-nitrophenyl group in the isomer believed to be Z. 

Z Arrangement was also ascribed to the isomer absorbing at higher field in the case of the ethyl compounds. CH and CH2 protons near the ring nitrogen are shielded by the aromatic ring in the Z compound. The protons at the ring carbon absorb at lower field (near 5.2 p.p.m.) in the Z compounds than in the E compounds (4.50-4.70 p.p.m.). The chemical shift of this proton may be used for E-Z discrimination in further substances. 

Additional adsorption sites are provided on open metal sites, when available. [Cu3(BTC)2] is performant in the selective adsorption and separation of olefinic compounds. The highly relevant separations of propene from propane and of isobutene from isobutane have been accomplished with separation factors of 2.0 and 2.1, respectively [101, 102]. [Cu3(BTC)2] also selectively takes up pentene isomers from aliphatic solvent in liquid phase, and even discriminates between a series of cis- and trans-olefin isomer mixtures with varying chain length, always preferring a double bond in cis-position. This behavior is ascribed to tt -complexation with the open Cu sites [100]. 

Gaziano, J.M. et al.. Discrimination in absorption or transport of (3-carotene isomers after oral supplementation with either all-trans or 9-cis (3-carotene, Am. J. Clin. Nutr., 61, 1248, 1995. 

To summarize the data in table 1, neither MDMA nor MBDB has hallu-cinogen-like discriminative stimulus properties. Symmetrical transfer of the MDMA and MBDB stimulus indicates that their primary discriminative stimulus effects are very similar. For both MDMA and MBDB, there is enantioselectivity for the S isomer, with about a twofold eudismic ratio. Finally, the substitution of (- )-amphetamine and cocaine in MDMA-trained rats may indicate that MDMA has some psychostimulant-like properties, while hffiDB seems to lack this activity. 

Based on the modest ability of the (+)-isomers of MDMA and MBDB to inhibit the reuptake of norepinephrine (NE) into hypothalamic synaptosomes (Steele et al. 1987). it seemed possible that noradrenergic pathways might be involved in the eue. In ano er series of drug discrimination experiments designed to test this hypothesis, the specific NE uptake inhibitor (-)-tomoxctine was tested for stimulus transfer in doses up to 10 mg/kg in MDMA-trained rats. At 5 mg/kg, 67 percent of the animals responded on, the drug lever. However, pretreatment with tomoxetine in six rats trained to discriminate MDMA from saline had no effect on the discrimination of a subsequent dose of MDMA. 

FIGURE 2. The effects of racemic 3,4-MDA (MDA) and its optical isomers in rats trained to discriminate DOM from saline... 

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