barger@ils.nwu.edu (Jorn Barger) (09/26/90)
All the references I've checked always visualize muscle contraction in terms of ATP causing _conformation changes_ in cross-bridges that ratchet or somehow drag the myosin along the actin, rather like the guy in cartoons dragging himself across the desert sands... But if you acknowledge that most of the energy released by breaking a phosphate off ATP is released as kinetic repulsion, shouldn't there be a Newtonian recoil? Wouldn't that make a much neater mechanism, ATP's firing simultaneously and contraction looking like big anti-aircraft guns recoiling? Jet powered? Which visualization is more consistent with measurements? One big difference seems to me to be that the crossbridges idea implies that there will be an adhesive force _holding_ the muscle in its contracted state... How could you test this? Will ATP fire when bound to myosin in the absence of actin? Could you align a lot of myosin and detect the resulting pressure-pulse? ......................................................................... (when it's quiet/ i can hear the dolphins sing) .........................................................................