Secondary structure of chorion proteins of the Lepidoptera Pericallia ricini and Ariadne merione by ATR FT-IR and micro-Raman spectroscopy

The gross morphological features of the eggs and eggshells (chorions) of two Lepidoptera species, Pericallia ricini and Ariadne merione were revealed for the first time by scanning and transmission electron microscopy. These two insect pests are extremely serious threats for many crops, mainly in India, but also in several other regions of the world. Micro-Raman and ATR FT-IR spectroscopy were also applied to study in detail the secondary structure of the eggshell (chorion) proteins of these Lepidoptera species. Both techniques indicate that the two species have nearly identical conformations of their chorion proteins with abundant antiparallel β-pleated sheet. These results are in support of our previous findings that the helicoidal architecture of the proteinaceous chorion of Lepidoptera and fishes is dictated by a common molecular denominator, the antiparallel β-pleated sheet secondary structure.