Enantiomer-specific

Overall, there is excellent agreement between the three different experiments, and between the enantiomer specific measurements made at the LURE and Elettra synchrotrons. The PECO reaches its maximum magnitude... 

Jones KH, RT Smith, PW Trudgill (1993) Diketocamphane enantiomer-specific Bayer-Villiger monooxygenases from camphor-grown Pseudomonas putida ATCC 17453. J Gen Microbiol 139 797-805. 

Manifestation of specificity in maximal rate constants rather than in stability constants is illustrated particularly well by the cyclohexaamylose-accelerated release of fluoride ion from Sarin. Although the inclusion complex of (rate acceleration is much larger for the (—)-enantiomer. Specificity is equally dramatic in... 

Enantiomerically enriched samples of 1-indanol, used to determine the enantiomer specificity by GC, can be prepared by hydrogen transfer ruthenium-catalysed reduction, as described by Ursini et al ... 

Gao S, Wang J, Yu Z, Guo Q, Sheng G, Fu G (2011) Hexabromocyclododecanes in surface soils from e-waste recycling areas and industrial areas in South China concentrations, diastereoisomer-and enantiomer-specific profiles, and inventory. Environ Sci Technol 45 2093-2099... 

H., Solomon, K.R. and Muir, D.C.G. (2003) Enantiomer-specific biomagnification of alpha-hexachlorocyclohexane and selected chiral chlordane-related compounds within an Arctic marine food web. Environ Toxicol Chem, 22, 2482-2491. 

Tucker GT, Lennard MS. Enantiomer specific pharmacokinetics. Pharmacol Ther 1990 45 309. 

The racemization is apparently very simple, but the detailed mechanism remains unsolved. The reaction proceeds via either a one-base or a two-base mechainsm.30,313 In the one-base mechanism, an amino acid residue of the enzyme abstracts the substrate a-proton of the external Schiff base to form an anionic intermediate. The racemization results from the sterically random return of hydrogen to the a-carbon of the intermediate. In the two-base mechanism, two enantiomer-specific bases juxtaposed on either side of the chiral carbon exist in the active center. One base abstracts the a-proton from the external Schiff base, and the conjugated acid of the second base catalyzes protonation to the anionic intermediate from the other side. These roles are reversed for the racemization of the antipodal substrate. 

From the study with variable concentration of the amine, the yellow solution of (RRRR)-53 in chloroform remains unaltered by addition of the amine in a range of concentrations, 4.8 xlO-7 to 1.2xlO 6M, whereas the solution of (SSSS)-53 reveals a color change from yellow to reddish violet with the same concentration of the amine. In other words, enantiomer selective complexation and enantiomer specific coloration were realized by this finding. 

Janak, K., Covaci, A., Voorspoels, S., Becher, G. (2005) Hexabromocyclododecane in marine species from the Western Scheldt estuary diastereoisomer- and enantiomer-specific accumulation. Environ. ScL Technol, 39 1987-1994. 

Enantiomer-Specific Microbial Biotransformation of Chiral POPs... 

In laboratory microcosms, ira 5-permethrin was selectively degraded compared to the other diastereomer, cw-permethrin, by six bacterial strains [19]. These strains also preferentially biotransformed 15-cw-bifenthrin over their antipodal l/ -cw-enantiomers, which were more toxic to daphnids [19]. Enantioselectivity was more pronounced for cw-permethrin than for cw-bifenthrin, and was strain-dependent. The (—)-enantiomer of both pyrethroids was preferentially depleted in sediments adjacent to a plant nursery, suggesting that in situ microbial biotransformation was enantioselective [20]. Although all enantiomers of permethrin were hydrolyzed quickly in C-labeled experiments in soils and sediments, the degradates of both cis- and irara-permethrin s -enantiomers were mineralized more quickly than those of the 5-enantiomer, while degradation products of cA-permethrin were more persistent than those of the trans-isomex [185]. Enantioslective degradation of fenvalerate in soil slurries has also been reported [83]. These smdies underscore how enantiomer-specific biotransformation can affect pyrethroid environmental residues, the toxicity of which is also enantiomer-dependent [18-20]. 

Enantiomer-Specific Transformation and Processing of Chiral POPs by Biota... 

Invertebrates had been thought to have poor capability to biotransform many POPs, as shown by experiment [186-188]. This lack is likely from low CYP abundance and activity. Chirahty has shown that while it is likely that most aquatic invertebrates do indeed lack the capacity to biotransform POPs, some species are capable of metabolizing some POPs stereoselectively. This finding is significant, as invertebrates are a major component of lower food webs, and bioaccumulation of nonracemic POPs results in more significant enantiomer-specific exposure and toxicity to predator organisms, including humans. 

Pinnipeds (e.g., seals, walruses) are a key link in many marine food webs, in that they are commonly found, predate on fish, and are hunted in turn by sharks, polar bears, and Arctic Inuit peoples as part of their traditional diet. In these roles, pinnipeds play a significant role in bioaccumulating POPs and in transferring these contaminant burdens to higher trophic levels. Thus, an understanding of POP dynamics in pinnipeds is important in exposure and risk assessment, and an enantiomer-specific understanding is vital given that pinnipeds bioprocess POPs enantioselectively. 

Hoekstra, P.F. Bumison, B.K. NeheU, T. Muir, D.C.G., Enantiomer-specific activity of o,p -DDT with the human estrogen receptor Toxicol. Lett. 2001, 125, 75-81. 

Janak, K. Sellstrom, U. Johannsson, A.-K. Becher, G. deWit, C.A. Lindberg,R Helander, B., Enantiomer-specific accumulation of hexabromocyclododecanes in eggs of predatory birds Chemosphere 2008, 73, S193-S200. 

Herzke, D. Kallenbom, R. Nygard, T., Organochlorines in egg samples from Norwegian birds of prey Congener-, isomer- and enantiomer specific considerations Set Total Environ. 2002, 291, 59-71. 

Kallenbom, R. Planting, S. Haugen, J.-E., Congener-, isomer-, and enantiomer-specific distribution of organochlorines in dippers (Cinclus cinclus L.) from southern Norway Chemosphere 1998, 37, 2489-2499. 

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