Applications of solids NMR to the analysis of insect sclerotized structures

This article reviews the solids NMR research conducted on insect sclerotized structures in the last 10 years and previews some of the experiments that will be conducted in the future, Solids MMR has been used as a noninvasive approach to investigate the chemical compositions of, and some covalent interactions that occur in, several types of sclerotized structures that are otherwise highly intractable to conventional chemical analyses, Sclerotization is a complex process used by insects to confer stability and mechanical versatility to their cuticular exoskeletons and certain other proteinaceous structures; Samples analyzed include cuticular exoskeletons, egg cases, egg shells, cocoons and peritrophic membranes, Cross polarization, dipolar decoupling, magic angle spinning, magnetization dephasing, and isotropic enrichment were used to obtain high resolution spectra that provide information about the types and relative concentrations of carbon atoms as well as internuclear distances and covalent bonds between carbon and nitrogen atoms, Relative amounts of protein, chitin, catechols, lipids, pigment, and oxalate were estimated, Covalent interactions between protein nitrogens and catechol carbons were detected in the stiff brown pupal cuticle of the tobacco hornworm, Manduca sexta, The results of these solids NMR studies support the hypothesis that sclerotization of insect structures occurs primarily when quinones derived from N-acylcatecholamines form cross-links and adducts with functional groups of proteins deposited in the structures, Future applications of solids NMR will utilize advanced techniques for further probing the covalent interactions of(13)C, N-15 and O-17-labeled catechols, chitin and protein in sclerotized structures.