“…In the absence of nucleotide, only one of myosin's reactive sulfhydryls, Cys-707, is easily modified (11,16,17 buffer" or "Ni 2ϩ buffer," respectively), chelating agent in the absence of metal ion (50 mM KCl, 50 mM Mops, 1 mM EGTA: "EGTA buffer"), or both metal ion and chelating agent (50 mM KCl, 50 mM Mops, 1 mM EGTA, 2 mM MgCl 2 or various concentrations of FeCl 3 or NiCl 2 : "Mg 2ϩ /EGTA buffer," "Fe 3ϩ /EGTA buffer," or "Ni 2ϩ /EGTA buffer"). The pH was adjusted to 7.2 at the temperature appropriate for each sample.…”