SEDIMENTATION BEHAVIOR OF CHEMICALLY REACTING SYSTEMS
SEDIMENTATION BEHAVIOR OF CHEMICALLY REACTING SYSTEMS
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DOI：
10.1073/pnas.58.1.45
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发表时间：
1967-01-01
影响因子：
11.1
通讯作者：
BETHUNE, JL
中科院分区：
文献类型：
--
作者：
KEGELES, G;RHODES, L;BETHUNE, JL
由于对于分析沉降速度实验以及对于密度梯度实验2、3和带沉降实验，超离心器在中等至高速下操作，因此在池底部可产生100 - 500大气压量级的高压。已经表明，平衡常数的对数的梯度遵循反应的摩尔体积，这导致非常大的压力效应在高速反应的大分子。5表1举例说明了这些影响的程度。在所有的高速超离心中，必须考虑到凝聚系统中平衡常数如此巨大变化的后果。在此将指出三种类型的实验的一些影响。速度沉降。-该过程以高速进行，传统上以尽可能高的速度进行，以提高分辨能力。它是混合物分析的最标准化程序。1分离物种之间的化学反应所引起的并发症首先被定量地处理为异构化，6聚合，7和双分子复合物的形成。[8]这些作者没有考虑压力对反应的影响，也没有考虑随后的改进。因此，他们的处理直接适用于移动边界电泳，但不适用于超离心，而不进一步认真校正压力的影响。在逆流分布模拟计算的直接再应用中，我们现在通过根据In K（x）= In K（x0）-（AV/RT）p（w2/2）（x2-x02）计算每个位置x处化学反应的平衡常数K（x），包括了压力的影响。(1)这里x0代表液体顶面的旋转半径，AV是反应的摩尔体积，R是摩尔气体常数，T是绝对温度，p是溶液密度，w是转子的角速度。在每一个水平上，所有的组分浓度都必须满足平衡常数的局部值。
Since the ultracentrifuge is operated at moderate to high speeds for analytical sedimentation velocity experiments' as well as for density-gradient experiments2'3 and band-sedimentation experiments, 4 high pressures of the order of 100 500 atm may be generated at the cell bottom. It has been shown that the gradient of the logarithm of the equilibrium constant follows the molar volume of reaction, which leads to very large pressure effects for reacting macromolecules at high speeds. 5 Examples of the magnitude of these effects are shown in Table 1. The consequences of such enormous changes of the equilibrium constant in a condensed system must be taken into account in all high-speed ultracentrifugation. Some effects on three types of experiments will be pointed out here. Velocity Sedimentation.-This procedure is performed at high speeds, traditionally at as high a speed as attainable, to improve resolving power. It is the most standardized procedure for the analysis of mixtures. 1 The complications consequent upon chemical reactions between the separating species were first treated quantitatively for isomerizations, 6 polymerizations, 7 and bimolecular complex formation. 8 These authors did not take into account the effect of pressure on the reactions, nor did subsequent refinements. 9-'3 Thus their treatments apply directly to moving-boundary electrophoresis, but are inapplicable to ultracentrifugation without further serious correction for the effect of pressure. In a direct reapplication of the countercurrent distribution analogue calcula-tions,'3 we have now included the effect of pressure by calculating the equilibrium constant K (x) for the chemical reaction at each position x according to In K (x)= In K (xo)-(AV/RT) p (w2/2)(X2-x02).(1) Here xo represents the radius of rotation at the top surface of the liquid, AV is the molar volume of reaction, R the molar gas constant, T the absolute temperature, p the solution density, and w the angular velocity of the rotor. At each level, all species concentrations are required to satisfy the local valueof the equilibrium constant.