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HEAT‐INDUCED TRANSITIONS IN THE PROTEIN‐PROTEIN INTERACTION OF BOVINE NATURAL ACTOMYOSIN 1
Author(s) -
ZIEGLER G. R.,
ACTON J. C.
Publication year - 1984
Publication title -
journal of food biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 47
eISSN - 1745-4514
pISSN - 0145-8884
DOI - 10.1111/j.1745-4514.1984.tb00311.x
Subject(s) - chemistry , arrhenius equation , kinetics , activation energy , atmospheric temperature range , crystallography , thermodynamics , physics , quantum mechanics
Protein‐protein interaction of bovine natural actomyosin (NAM) was studied by means of optical density changes resulting from discrete particle formation in the temperature range of4°C to 70°C. From Arrhenius plots, the apparent heat of activation (ΔH a ) at pH 5.5 (17.1 kcallmole) was significantly (P<0.05) lower than activation energies in the pH range of 6.0 to 7.5. The lower Δ H a resulted in initiation of protein‐protein interaction at a temperature near 16°C at pH 5.5, whereas interaction did not proceed until the temperature approached 37°C at pH 6.0 and above. Derivative curves (dOD/dT) at pH 5.5 and 6.0 showed two distinct NAM thermal transition regions. Tm 1 occurred at 43.0°C at pH 5.5 and 48.5°C at pH 6.0, with the 5.5°C difference possibly arising from effects of proton binding in altering protein conformation. Only a 1.5°C difference in Tm 2 (56.0°C at pH 5.5 versus 57.5°C at pH 6.0) was found. Although the overall heat‐mediated NAM aggregation (in dilute solution) was found to follow first order kinetics by two evaluation methods, the existence of two thermal transitions supports a two‐step reaction mechanism proposed for the formation of protein gels (in higher concentration solutions).