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Effects of pulsed electric fields and heat treatment on stability and secondary structure of bovine immunoglobulin G

Li, S.Q., Bomser, J.A., Zhang, Q.H.
Journal of agricultural and food chemistry 2005 v.53 no.3 pp. 663-670
cattle, cow colostrum, immunoglobulin G, protein secondary structure, heat treatment, pulsed electric fields, electrical treatment, circular dichroism spectroscopy, nonthermal processing, immunomodulators
Bovine immunoglobulin G (IgG) solutions were subjected to pulsed electric fields (PEF) or heat treatment to investigate the effect of processing on secondary structure monitored using circular dichroism spectrometry. Under heat treatment, the critical temperature for bovine IgG to change secondary structure at neutral pH in borate buffer is 72 degrees C. A conversion of the secondary structure from beta-sheets into random coils along with the loss of immunoactivity of bovine IgG was observed when heated at 82 degrees C for 120 s. In contrast, PEF treatment at 41.1 kV/cm for 54 microsecond with bipolar pulses (outlet at 43.8 degrees C) caused no detectable changes in the secondary structure or the thermal stability of secondary structure. A shape factor, S(200nm)217nm, ratio of magnitude of the positive CD band at 200 nm to that of the negative CD band at 217 nm, was closely correlated to the immunoactivity of bovine IgG (r2 = 0.99) and quantifies changes of secondary structure.