Andreev O A, Andreeva A L, Borejdo J
Baylor Research Institute, Baylor University Medical Center, Dallas, Texas 75226.
Biophys J. 1993 Sep;65(3):1027-38. doi: 10.1016/S0006-3495(93)81161-5.
Fluorescently labeled myosin heads (S1) were added to muscle fibers and myofibrils at various concentrations. The orientation of the absorption dipole of the dye with respect to the axis of F-actin was calculated from polarization of fluorescence which was measured by a novel method from video images of muscle. In this method light emitted from muscle was split by a birefringent crystal into two nonoverlapping images: the first image was created with light polarized in the direction parallel to muscle axis, and the second image was created with light polarized in the direction perpendicular to muscle axis. Images were recorded by high-sensitivity video camera and polarization was calculated from the relative intensity of both images. The method allows measurement of the fluorescence polarization from single myofibril irrigated with low concentrations of S1 labeled with dye. Orientation was also measured by fluorescence-detected linear dichroism. The orientation was different when muscle was irrigated with high concentration of S1 (molar ratio S1:actin in the I bands equal to 1) then when it was irrigated with low concentration of S1 (molar ratio S1:actin in the I bands equal to 0.32). The results support our earlier proposal that S1 could form two different rigor complexes with F-actin depending on the molar ratio of S1:actin.
将荧光标记的肌球蛋白头部（S1）以不同浓度添加到肌肉纤维和肌原纤维中。通过一种从肌肉视频图像测量荧光偏振的新方法，计算染料吸收偶极相对于F - 肌动蛋白轴的取向。在该方法中，肌肉发出的光被双折射晶体分成两个不重叠的图像：第一个图像由平行于肌肉轴方向偏振的光形成，第二个图像由垂直于肌肉轴方向偏振的光形成。图像由高灵敏度摄像机记录，并根据两个图像的相对强度计算偏振。该方法允许测量用低浓度染料标记的S1灌注的单个肌原纤维的荧光偏振。取向也通过荧光检测线性二色性进行测量。当用高浓度的S1（I带中S1与肌动蛋白的摩尔比等于1）灌注肌肉时，其取向与用低浓度的S（I带中S1与肌动蛋白的摩尔比等于0.32）灌注时不同。结果支持了我们之前的提议，即S1可以根据S1与肌动蛋白的摩尔比与F - 肌动蛋白形成两种不同的强直复合物。
