Integrated analysis of three-dimensional molecular dynamics of actin and myosin, and macro-dynamics of cardiac muscle and left ventricle

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The purpose of this project is to analyze the molecular interaction between actin and myosin in isolated cardiac muscle and whole heart with time- resolved way in one cardiac cycle.We assembled the short angle diffraction apparatus with x-ray energy 12.4keV and wave length 1 A at BL45XU beam line in Spring-8 (Super Photon Ring 8GeV). We measured x-ray diffraction pattern by using x-ray image intensifier and cooled CCD. For the measurement of diffraction pattern from the left ventricle we used BL40XU, which has higher energy than BL45XU. In this case the camera length was 3m and x-ray energy was 16keV. We controlled the x-ray energy to the suitable strength with changing the width of front-end slit. We measured the sarcomere length by laser diffraction pattern and compared it with lateral diffraction pattern by x-ray, and thus analyze the three-dimensional dynamics between molecular and cellular level.We got the equatorial diffraction from isolated and perfused papillary muscle from rig … More ht ventricle of rat. From the ratio between (1,0)/(1,1) diffraction the mass transfer from the myosin molecule to actin molecule, which is the index of crossbridge formation, was measured. We analyzed the change of molecular interaction between actin and myosin with the change of sarcomere length and afterload in isometric and isotonic contraction. In addition we analyzed the x-ray diffraction pattern from left ventricular wall in isolated Langendorff-perfusion heart.As the mass transfer from myosin molecular to actin increased with cardiac muscle length in isometric contraction, we concluded the amount of crossbridge formation is the molecular basis of the Starling mechanism of the heart. In isotonic contraction the developed force also increased with the amount of crossbridge formation. However, the amount of mass-transfer from the myosin molecular to actin in small afterloaded contraction was interestingly smaller than that at the same developed force in isometric contraction. The developed pressure in isovolumically contracting left ventricle was in accordance with the mass-transfer, indicating the molecular basis of the Staring mechanism of the heart in whole heart. The diffraction pattern from the left ventricular wall changed with regular manner depending on x-ray irradiation portion at subepicardium, mid wall and subendocardium. We concluded that the change of the three-dimensional molecular structure at the different portion of the left ventricular free wall could be estimated in time resolved manner in isovolumically contracting isolated and perfused heart. Less