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  • Author or Editor: J. Duda x
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Abstract  

The effect of phalloidin on the thermal stability of skeletal actin filaments polymerized from ADP-binding monomers was investigated with the method of differential scanning calorimetry. Phalloidin shifted the melting temperature of the ADP-F-actin from 59.1±1.0 to 80.0±1.2°C. The stabilizing effect of phalloidin propagated cooperatively along the filament. The cooperativity factor according to the applied model was 1.07±0.11. With these measurements it was possible to demonstrate that the binding of phalloidin has lower influence on the adjacent protomers in ADP- (k=1) than in ATP-actin filaments (k=3).

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Abstract  

The effect of phalloidin on filaments polymerized from ADP-actin monomers of the heart muscle was investigated with differential scanning calorimetry. Heart muscle contains α-skeletal and α-cardiac actin isoforms. In the absence of phalloidin the melting temperature was 55°C for the α-cardiac actin isoform and 58°C for the α-skeletal one when the filaments were generated from ADP-actin monomers. After the binding of phalloidin the melting temperature was isoform independent (85.5°C). We concluded that phalloidin stabilized the actin filaments of α-skeletal and α-cardiac actin isoforms to the same extent when they were polymerized from ADP-actin monomers.

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