Abstract - Structural Characterisation of rubber from Lactarius mushrooms;1H-NMR anlysis of Terminal groups in the rubber chain


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	Publications of MRB Latest Publications MRB Digest Journal of Rubber Research 3^rd Qtr 2008 Vol 11(3) 2^nd Qtr 2008 Vol 11(2) 1^st Qtr 2008 Vol 11(1) 4^th Qtr 2007 Vol 10(4) 3^rd Qtr 2007 Vol 10(3) 2^nd Qtr 2007 Vol 10(2) 1^st Qtr 2007 Vol 10(1) 1^st Qtr 2006 Vol 9(1) 2^nd Qtr 2006 Vol 9(2) 3^rd Qtr 2006 Vol 9(3) 4^th Qtr 2006 Vol 9(4) Submit paper/article Order Form	Abstract Structural Characterisation of Rubber from Lactarius mushrooms; ¹H-NMR Anlysis of Terminal Groups in the Rubber Chain The initiating species and termination step of rubber biosynthesis have been identified by structural characterisation of both terminal groups with 1H-NMR for rubber from sporophores of Lactarius volemus. The sequence of trans- and cis-isoprene units along the chain was determined using polyprenol-18 and ficaprenol-11, containing two-trans and three-trans sequences, respectively, as models. The initial dimethylallyl-trans-trans sequence was observed in the rubber from L.volemus. This demonstrates that the initiating species of rubber formation in L.volemus is trans,trans-farnesyl diphosphate. The presence of hydroxyl and fatty-acid ester terminal groups in the rubber indicated that the termination reaction can be hydrolysis of polyprenyl diphosphate. The fraction corresponding to the highest molecular weight of L. volemus rubber had the trans-trans-(cic)_n-sequence, but contained only trace amounts of the dimethylallyl group. The occurrence of a selective modification of the dimethylallyl group after polymerisation was presumed for the highest molecular weight rubber. The mechanism of rubber formation in Hevea brasiliensis is discussed on the basis of the structural information obtained from Lactarius mushroom rubber.
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