Direct x-ray observation of a single hexagonal myofilament lattice in native myofibrils of striated muscle.
A striated muscle fiber consists of thousands of myofibrils with crystalline hexagonal myofilament lattices. Because the lattices are randomly oriented, the fiber gives rise to an equatorial x-ray diffraction pattern, which is essentially a rotary-averaged "powder diffraction," carrying only information about the distance between the lattice planes. We were able to record an x-ray diffraction pattern from a single myofilament lattice, very likely originating from a single myofibril from the flight muscle of a bumblebee, by orienting the incident x-ray microbeam along the myofibrillar axis (end-on diffraction). The pattern consisted of a number of hexagonally symmetrical diffraction spots whose originating lattice planes were readily identified. This also held true for some of the weak higher order reflections. The spot-like appearance of reflections implies that the lattice order is extremely well maintained for a distance of millimeters, covering up to a thousand of approximately 2.5-microm-long sarcomeres connected in series. The results open the possibility of applying the x-ray microdiffraction technique to study many other micrometer-sized assemblies of functional biomolecules in the cell.
Life and Environment Division, SPring-8, Japan Synchrotron Radiation Research Institute, Hyogo 679-5198, Japan. iwamoto@spring8.or.jp
Hiroyuki
H
Iwamoto
Yukihiro
Y
Nishikawa
Jun'ichi
J
Wakayama
Tetsuro
T
Fujisawa
D000818:Animals; D001516:Bees; D005583:Fourier Analysis; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000648:ultrastructure*; D009132:Muscles / Q000378:metabolism; D014961:X-Ray Diffraction; D014965:X-Rays