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蛋白质物理化学研究：第二部分：酪蛋白的溶解度与其与碱基结合能力的关系。含蛋白质和氢氧化钠的体系中酪蛋白的溶解度。

STUDIES IN THE PHYSICAL CHEMISTRY OF THE PROTEINS : II. THE RELATION BETWEEN THE SOLUBILITY OF CASEIN AND ITS CAPACITY TO COMBINE WITH BASE. THE SOLUBILITY OF CASEIN IN SYSTEMS CONTAINING THE PROTEIN AND SODIUM HYDROXIDE.

机构信息

Department of Physical Chemistry in the Laboratories of Physiology, Harvard Medical School, Boston.

出版信息

J Gen Physiol. 1923 May 20;5(5):521-54. doi: 10.1085/jgp.5.5.521.

DOI:10.1085/jgp.5.5.521
PMID:19872018
原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC2140591/
Abstract
  1. The solubility in water of purified, uncombined casein has previously been reported to be 0.11 gm. in 1 liter at 25 degrees C. This solubility represents the sum of the concentrations of the casein molecule and of the soluble ions into which it dissociates. 2. The solubility of casein has now been studied in systems containing the protein and varying amounts of sodium hydroxide. It was found that casein forms a well defined soluble disodium compound, and that solubility was completely determined by (a) the solubility of the casein molecule, and (b) the concentration of the disodium casein compound. 3. In our experiments each mol of sodium hydroxide combined with approximately 2,100 gm. of casein. 4. The equivalent combining weight of casein for this base is just half the minimal molecular weight as calculated from the sulfur and phosphorus content, and one-sixth the minimal molecular weight calculated from the tryptophane content of casein. 5. From the study of systems containing the protein and very small amounts of sodium hydroxide it was possible to determine the solubility of the casein molecule, and also the degree to which it dissociated as a divalent acid and combined with base. 6. Solubility in such systems increased in direct proportion to the amount of sodium hydroxide they contained. 7. The concentration of the soluble casein compound varied inversely as the square of the hydrogen ion concentration, directly as the solubility of the casein molecule, Su, and as the constants Ka(1) and Ka(2) defining its acid dissociation. 8. The product of the solubility of the casein molecule and its acid dissociation constants yields the solubility product constant, Su.Ka(1).Ka(2) = 2.2 x 10(-12) gm. casein per liter at 25 degrees C. 9. The solubility of the casein molecule has been estimated from this constant, and also from the relation between the solubility of the casein and the sodium hydroxide concentration, to be approximately 0.09 gm. per liter at 25 degrees C. 10. The product of the acid dissociation constants, Ka(1) and Ka(2), must therefore be 24 x 10(-12)N. 11. It is believed that these constants completely characterize the solubility of casein in systems containing the protein and small amounts of sodium hydroxide.
摘要

  1. 以前曾报道，在 25°C 下，纯净、未结合的酪蛋白在 1 升水中的溶解度为 0.11 克。该溶解度代表了酪蛋白分子的浓度以及其离解成的可溶性离子的浓度之和。

  2. 现在已经研究了在含有蛋白质和不同量氢氧化钠的系统中酪蛋白的溶解度。结果发现，酪蛋白形成了一种定义明确的可溶性二钠化合物，溶解度完全取决于（a）酪蛋白分子的溶解度，以及（b）二钠酪蛋白化合物的浓度。

  3. 在我们的实验中，每摩尔氢氧化钠与大约 2100 克酪蛋白结合。

  4. 这种碱的酪蛋白的当量结合重量正好是根据硫和磷含量计算出的最小分子量的一半，也是根据酪蛋白色氨酸含量计算出的最小分子量的六分之一。

  5. 通过研究含有少量氢氧化钠的蛋白质系统，我们能够确定酪蛋白分子的溶解度，以及它作为二价酸离解并与碱结合的程度。

  6. 在这些系统中的溶解度与它们所含的氢氧化钠量成正比。

  7. 可溶性酪蛋白化合物的浓度与氢离子浓度的平方成反比，与酪蛋白分子的溶解度 Su 成正比，与定义其酸离解的常数 Ka(1)和 Ka(2)成正比。

  8. 酪蛋白分子的溶解度与其酸离解常数的乘积产生溶解度积常数，Su.Ka(1).Ka(2) = 2.2 x 10(-12)克酪蛋白/升在 25°C。

  9. 根据该常数以及酪蛋白的溶解度与氢氧化钠浓度之间的关系，估计酪蛋白分子的溶解度约为 0.09 克/升在 25°C。

  10. 酸离解常数 Ka(1)和 Ka(2)的乘积必须为 24 x 10(-12)N。

  11. 据信，这些常数完全表征了在含有蛋白质和少量氢氧化钠的系统中酪蛋白的溶解度。

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STUDIES IN THE PHYSICAL CHEMISTRY OF THE PROTEINS : II. THE RELATION BETWEEN THE SOLUBILITY OF CASEIN AND ITS CAPACITY TO COMBINE WITH BASE. THE SOLUBILITY OF CASEIN IN SYSTEMS CONTAINING THE PROTEIN AND SODIUM HYDROXIDE.蛋白质物理化学研究：第二部分：酪蛋白的溶解度与其与碱基结合能力的关系。含蛋白质和氢氧化钠的体系中酪蛋白的溶解度。
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本文引用的文献

1
THE PROTECTIVE INFLUENCE OF BLOOD SERUM ON THE EXPERIMENTAL CELLFIBRIN TISSUE OF LIMULUS.血清对鲎实验性细胞纤维蛋白组织的保护作用
Science. 1920 Jan 2;51(1305):17-8. doi: 10.1126/science.51.1305.17.
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A contribution to the chemistry of proteids: Part I. A preliminary study of a hitherto undescribed product of tryptic digestion.蛋白质化学的一项贡献：第一部分。对一种迄今未描述的胰蛋白酶消化产物的初步研究。
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Caseinogen and its salts.酪蛋白原及其盐类。
J Physiol. 1901 Dec 23;27(4-5):398-406. doi: 10.1113/jphysiol.1901.sp000878.
4
Barger's Microscopical Method of determining Molecular Weights: Part II. Its Application to Caseinogen.巴杰尔测定分子量的显微镜法：第二部分。其在酪蛋白原上的应用。
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A New Method for Preparing Esters of Amino Acids. Composition of Caseinogen.一种制备氨基酸酯的新方法。酪蛋白原的组成。
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6
On Amino-acids.论氨基酸
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