THE IONIZATION OF ACIDIC METMYOGLOBIN
THE IONIZATION OF ACIDIC METMYOGLOBIN
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DOI：
10.1042/bj0520517
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发表时间：
1952-01-01
影响因子：
4.1
通讯作者：
HANANIA, G
中科院分区：
文献类型：
--
作者：
GEORGE, P;HANANIA, G
本文测定了马酸肌红蛋白在不同pH值、离子强度和温度下的电离平衡常数（Fe+（H_2O）= FeOH+H+）。盐对这种平衡的影响是显著的。因此，加入NaCl有利于离子化，直到离子强度约为0.01，但超过此值，效果就相反了。外推至0离子强度，20[度]时pK[图像]为9.038 [正负] 0.030，37[度]时为8.803 [正负] 0.025。从2个温度下的平衡常数。发现电离吸热到5.75 [±] 0.67 kg的程度。cal./摩尔[DELTA] S[degree]20 = -21.7 [plus or minus] 2.4 cal./莫耳度只有在pH 7.8-9.2范围内才能测量该电离常数。在碱性或酸性溶液中。在这种平衡与分子中的其他电离之间可能发生显著的相互作用，电离常数福尔斯的值随着pH值的增加而稳定下降。这种作用在高离子强度下受到抑制，这表明溶液中电解质离子之间存在特定的相互作用。和蛋白质上的带电基团。
The equilibrium constant for the ionization of (horse) acid metmyoglobin which may be represented as Fe+ (H2O)= FeOH+H+ was measured over a range of pH, ionic strength and temp. The effect of salts on this equilibrium is marked. Thus, addition of NaCl favors ionization up to an ionic strength of about 0.01, but beyond this the effect is reversed. Extrapolation to 0 ionic strength gives pK[image]o 9.038 [plus or minus] 0.030 at 20[degree] and 8.803 [plus or minus] 0.025 at 37[degree]. From the equilibrium constant at 2 temps. the ionization is found to be endothermic to the extent of 5.75 [plus or minus] 0.67 kg. cal./mole. [DELTA] S[degree]20 = -21.7 [plus or minus] 2.4 cal./mole deg. It is only possible to measure this ionization constant within the pH range 7.8-9.2. In more alkaline or acidic solns. significant interaction takes place between this equilibrium and, presumably, other ionizations in the molecule, and the value of the ionization constant falls steadily with increasing pH. This effect is suppressed at high ionic strengths, which suggests specific interaction between electrolyte ions in soln. and the charged groups on the protein.