Effects of radiation on the structure of bothropstoxin-1

THESIS: P. J. Spencer submitted his thesis for his Doctor of Philosophy degree in Nuclear Technology publicly examined in the Institute for Energy and Nuclear Research/Instituto de Pesquisas Energéticas e Nucleares, University of São Paulo/Universidade de São Paulo, SP, Brazil, in 2000.

Advisor: Prof. Dr. José Roberto Rogero

ABSTRACT. Ionizing radiation has been widely employed to attenuate venoms and toxins, preserving and even enhancing their immunogenic properties. However, little is known about molecular changes in irradiated proteins. In this work, we compared native and irradiated bothropstoxin-1, with the aim of characterizing the structural modifications induced by radiation. Our results indicate that radiation promotes a transition from the multimeric to the monomeric state in a dose-dependent manner. Spectral and calorimetric analysis suggest that the irradiated molecules undergo oxidation and partially unfold the remaining elements being stabilized by the seven disulphide bonds. The binding pattern of monoclonal antibodies raised against irradiated bothropstoxin indicates that most of the recognized epitopes are linear present on the surface of both native and irradiated toxin. Also, irradiated toxin appears to be more immunogenic, inducing the formation of native toxin-binding antibodies.

KEY WORDS: Bothropstoxin-1, ionizing radiation, immunogenicity.

CORRESPONDENCE TO:

P. J. SPENCER – IPEN/CNEN, Travessa R, 400, Cidade Universitária, Caixa Postal 11049, CEP: 05508-900, São Paulo, SP, Brasil.

E-mail:pspencer@net.ipen.br

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