Model studies for insect protein sclerotization: Oxidative loss of the side chain from 4-substituted catechols
✍ Scribed by Stephen G. Pyne; Roger J.W. Truscott; Maxwell M. Karin; Carmen Morales; Bernadette C. Walsh; Barbra L. Wynn
- Book ID
- 104203305
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- French
- Weight
- 511 KB
- Volume
- 46
- Category
- Article
- ISSN
- 0040-4020
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✦ Synopsis
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The oxidation of several 4-substituted catechols in aqueous solution, pH7 in the presence of aniline results in the formation of 4,5-dianilino-1,2benxoquinone 2 and the anil of 2 Q). The C-4 substituent is effkiently cleaved and mechanisms are proposed to account for this phenomenon based on HPLC and GC studies and the formation of N-methylaniline when these reactions were performed in the presence of sodium cyanoborohydride.
The evidence suggests that the initial step involves the addition of aniline to the catechol C-4 side chain.
Numerous 4-substituted 1,2-dihydroxybenxenes have been implicated in the crosslinking of protein during insect sc1erotixation.l a process in which the new insect cuticle is hardened and darkened. These catechol compounds are normally excreted from insect glands during ecdysis along with oxidase enzyme(s).
Mechanisms that have been suggested for insect protein tanning include: (i) quinone tanning.2 where it has been reasoned that catechols are first oxidized to o-quinones which may then cross-link protein possibly through lysine and histidine residues; (ii) P-sclerotization,3 a process assumed to involve crosslinking of proteins through the a and p carbons of the side chain of N-acetyldopamine;
(iii) quinone methide tanning,4 resulting from initial protein modification via p-quinone methides that arise from the tautomeric rearrangement of pquinones.
The modification of biopolymers by catechols has recently been reviewed by Peter.5