Difference between revisions of "Ortho-PCBs"
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| + | '''Ortho-PCBs''': congeners of [[PCBs]] that have one or more chlorines in ''ortho''-position (positions 2 or 6). Position of a group in aromatic ring as related to some other group can be ''ortho''-, ''meta''- (positions 3 or 5), or ''para''- (position 4). In PCB congeners (see [[Congener]]) this is counted from the carbon-carbon bridge between the two phenyl rings. ''ortho''-Congeners mean congeners that have one (mono-''ortho'') or several (di-''ortho'', tri-''ortho'', tetra-''ortho'') chlorines in ''ortho'' positions. ''ortho''-Positions affect the conformation of the molecule; non-''ortho'' PCBs can assume a completely flat (planar) conformation, which is close to that of dioxins. Space-requiring ''ortho'' chlorines are a steric hindrance for the flat conformation, and therefore only non-''ortho'' or to some extent mono-''ortho'' PCBs can mimic PCDDs to have similar toxic effects based on binding to [[AH receptor]]. Chlorines in para-positions seem to be preferably biodegraded. This means easier degradation of non-''ortho'' congeners, and ''ortho''-congeners are present in the environment at higher concentrations than non-''ortho'' congeners.<ref> Tuomisto, Vartiainen, Tuomisto: Dioxin synopsis. Report / National Institute for Health and Welfare, ISSN 1798-0089 ; 14/2011 [http://lib.thl.fi:2345/lib4/src?PBFORMTYPE=01002&TITLEID=53321&SQS=1:FI:1::10:50::HTML&PL=0]</ref> | ||
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| + | ==References== | ||
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[[category:Dioxin synopsis]] | [[category:Dioxin synopsis]] | ||
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Ortho-PCBs: congeners of PCBs that have one or more chlorines in ortho-position (positions 2 or 6). Position of a group in aromatic ring as related to some other group can be ortho-, meta- (positions 3 or 5), or para- (position 4). In PCB congeners (see Congener) this is counted from the carbon-carbon bridge between the two phenyl rings. ortho-Congeners mean congeners that have one (mono-ortho) or several (di-ortho, tri-ortho, tetra-ortho) chlorines in ortho positions. ortho-Positions affect the conformation of the molecule; non-ortho PCBs can assume a completely flat (planar) conformation, which is close to that of dioxins. Space-requiring ortho chlorines are a steric hindrance for the flat conformation, and therefore only non-ortho or to some extent mono-ortho PCBs can mimic PCDDs to have similar toxic effects based on binding to AH receptor. Chlorines in para-positions seem to be preferably biodegraded. This means easier degradation of non-ortho congeners, and ortho-congeners are present in the environment at higher concentrations than non-ortho congeners.[1]
