Dynamic rheological measurements on heat‐induced myosin gels: Effect of ionic strength, protein concentration and addition of adenosine triphosphate or pyrophosphate

Abstract

AbstractMyosin solutions and suspensions have been monitored during heating at pH 6.0 by using dynamic rheological measurements. The storage modulus (G′), the loss modulus (G) and the phase angle (δ) all showed a marked dependence on ionic strength in the temperature range 25–75°C. The filamentous gels (ionic strength <0.34) displayed a temporary reduction in G′ at temperatures between 50 and 60°C, presumably due to denaturation in parts of the rod portion of the myosin molecule. In the same temperature region the concentration dependence of G′ changed by a power of 2. The loss modulus also showed a marked concentration dependence, while the phase angle varied with concentration primarily at low (<50°C) temperatures. For the final gels, heated to 75°C, only G′ indicated marked differences due to different protein concentrations and ionic strengths; all gels were almost completely elastic (δ⋍1°). Adenosine triphosphate was shown to have a pronounced temporary effect on the filamentous gel formed at low temperatures, i.e. on the gel with the highest concentration dependence, while pyrophosphate had no such effect. However, both adenosine triphosphate (or rather its hydrolysis product: adenosine diphosphate) and pyrophosphate appeared to have a small, lasting effect on the heat‐gelling ability of myosin: the former a detrimental effect, the latter an improvement.