Jürgens K D, Peters T, Gros G
Zentrum Physiologie, Medizinische Hochschule, Hanover, Germany.
Proc Natl Acad Sci U S A. 1994 Apr 26;91(9):3829-33. doi: 10.1073/pnas.91.9.3829.
We report a method that allows us to determine the diffusion coefficient of native myoglobin in intact and mechanically unaffected red muscle fibers. The method is based on an optical recording of intracellular diffusion of metmyoglobin, which is produced inside the cells by photooxidation of oxymyoglobin with a UV light pulse. We find a myoglobin diffusivity of 1.2 x 10(-7) cm2/s (22 degrees C), which is only 1/10th of the value measured in very dilute myoglobin solutions and 1/5th of the value obtained from measurements in solutions of myoglobin at 18 g/dl. The latter value often has been used in model calculations of oxygen transport to tissue incorporating myoglobin-facilitated oxygen diffusion. Recalculating facilitated diffusion with the value obtained by us implies that its contribution to total intracellular oxygen transport is of minor importance. Furthermore, it shows that sterical hindrance to myoglobin diffusion is dominated by the muscle-cell architecture rather than by the overall protein concentration of the muscle fiber.
我们报告了一种方法，该方法使我们能够确定天然肌红蛋白在完整且未受机械影响的红色肌纤维中的扩散系数。该方法基于对高铁肌红蛋白细胞内扩散的光学记录，高铁肌红蛋白是通过用紫外光脉冲对氧合肌红蛋白进行光氧化在细胞内产生的。我们发现肌红蛋白的扩散率为1.2×10⁻⁷ cm²/s（22℃），这仅是在非常稀的肌红蛋白溶液中测得值的十分之一，也是在18 g/dl的肌红蛋白溶液中测得值的五分之一。后一个值经常被用于包含肌红蛋白促进氧扩散的组织氧运输模型计算中。用我们获得的值重新计算促进扩散意味着其对细胞内总氧运输的贡献微不足道。此外，这表明对肌红蛋白扩散的空间位阻主要由肌肉细胞结构决定，而非由肌纤维的整体蛋白质浓度决定。
