Effect of myofibrillar proteins of sea salmon (Pseudopercis semifasciata) - malonaldehyde interaction on microstructure and functionality

V. A. TIRONI, M.C. TOMÁS Y M.C. AÑÓN

Montreal, Canada

Congreso; 93rd AOCS Annual Meeting and Expo; 2002

AOCS

Malonaldehyde (MDA), a secondary breakdown product of lipid oxidation, can react with proteins producing modifications such as polymerization, cross–linking, insolubilization. The main aim of the present work was to study the influence of this interaction on the structure and functionality of myofibrillar proteins  of sea salmon in order to evaluate the possible negative impact according to technological requirements. Myofibrillar proteins of sea salmon (Pseudopercis semifasciata) were incubated with MDA (protein : MDA  3.5 : 1) at  27°C, from  0 – 8 h, moderate agitation. Then, samples were treated with different buffer systems: 1) 0.6M NaCl, 0.03M Tris, pH 7.0; 2) 0.6M NaCl, 0.03M Tris, 0.5%  SDS, 8 M urea, pH 7.0 and 3) 0.6M NaCl, 0.03M Tris, 0.5% SDS, 8 M  urea, 5 % b-mercaptoethanol (ME), pH 7.0 and protein solubility was determined after centrifugation (17000 g, 15 min, 10°C) by a modified Lowry method. SDS-PAGE of the soluble protein fractions were carried out . On the other hand, Transmission Electron Microscopy (TEM) images of the different systems were also obtained. Microscopic analysis evidenced that protein structure suffer important changes due to the interaction with MDA in comparison with the control system. The formation of new irregular networks related to the appearance of agreggates was relevant, particularly after a contact time of 4 and 8 h when was possible to detect significant protein agglomerations. In presence of the different chaotropic agents used (SDS, urea and b-mercaptoethanol) these protein agreggates could not be totally redisolved, indicating that   the interaction  mainly involved non disulfide covalent bridges.   This information also correlate with the results obtained by the electrophoretic patterns, evidencing that myosin heavy chain (MHC) and other protein species (40, 53 and 81 kDa) would be associated with the changes previously described.