title: A jump in an Arrhenius plot can be the consequence of a phase transition. The binding of ATP to myosin subfragment 1.
abstract: The temperature dependence of the kinetics of the binding of ATP to myosin subfragment-1 was studied by an ATP chase technique in a rapid-flow-quench apparatus: (formula; see text) A temperature range of 30 degrees C to -15 degrees C was obtained with ethylene glycol as antifreeze. The Arrhenius plot of k2 is discontinuous with a jump at 12 degrees C. Above the jump delta H+ = 9.5 kcal/mol, below delta H+ = 28.5 kcal/mol. Few such Arrhenius plots are recorded in the literature but they are predicted from theory. Thus, we explain our results as a phase change of the subfragment 1-ATP system at 12 degrees C. This is in agreement with certain structural studies.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011487:Protein Conformation; D011817:Rabbits; D013053:Spectrophotometry; D013696:Temperature; D013816:Thermodynamics
chemical_list: D015879:Myosin Subfragments; D010446:Peptide Fragments; D000255:Adenosine Triphosphate; D009218:Myosins