HYDRATION OF GELATIN IN SOLUTION

1. It was shown that the high viscosity of gelatin solutions as well as the character of the osmotic pressure-concentration curves indicates that gelatin is hydrated even at temperatures as high as 50°C. 2. The degree of hydration of gelatin was determined by means of viscosity measurements through the application of the formula See PDF for Equation. 3. When the concentration of gelatin was corrected for the volume of water of hydration as obtained from the viscosity measurements, the relation between the osmotic pressure of various concentrations of gelatin and the corrected concentrations became linear, thus making it possible to determine the apparent molecular weight of gelatin through the application of van''t Hoff''s law. The molecular weight of gelatin at 35°C. proved to be 61,500. 4. A study was made of the mechanism of hydration of gelatin and it was shown that the experimental data agree with the theory that the hydration of gelatin is a pure osmotic pressure phenomenon brought about by the presence in gelatin of a number of insoluble micellæ containing a definite amount of a soluble ingredient of gelatin. As long as there is a difference in the osmotic pressure between the inside of the micellæ and the outside gelatin solution the micellæ swell until an equilibrium is established at which the osmotic pressure inside of the micellæ is balanced by the total osmotic pressure of the gelatin solution and by the elasticity pressure of the micellæ. 5. On addition of HCl to isoelectric gelatin the total activity of ions inside of the micellæ is greater than in the outside solution due to a greater concentration of protein in the micellæ. This brings about a further swelling of the micellæ until a Donnan equilibrium is established in the ion distribution accompanied by an equilibrium in the osmotic pressure. Through the application of the theory developed here it was possible actually to calculate the osmotic pressure difference between the inside of the micellæ and the outside solution which was brought about by the difference in the ion distribution. 6. According to the same theory the effect of pH on viscosity of gelatin should diminish with increase in concentration of gelatin, since the difference in the concentration of the protein inside and outside of the micellæ also decreases. This was confirmed experimentally. At concentrations above 8 gm. per 100 gm. of H₂O there is very little difference in the viscosity of gelatin of various pH as compared with that of isoelectric gelatin.     

OCCURRENCE OF LOW MOLECULAR WEIGHT AND HIGH CYSTEINE CONTAINING ALBUMIN STORAGE PROTEINS IN OILSEEDS OF DIVERSE SPECIES

The proteins in the oilseeds of species from 11 families, including sunflower, mustard, linseed, almond, lupin, peanut, cucumber, Brazil nut, hazelnut, yucca, castor bean, and cottonseed were studied. Sucrose gradient centrifugation showed that a substantial proportion of the total seed protein from each species migrated with a 2S sedimentation coefficient. The 2S proteins, being water-soluble and thus termed albumins, comprised 20–60% of the total seed proteins, while faster migrating globulins comprised the rest. The amino acid compositions of the 2S proteins were characterisitic of storage proteins by having a high amide content. However, the 2S proteins are different from the classical globulin storage proteins in having a high content of cysteine. It is proposed that 2S albumins are seed storage proteins with a wide distribution and with chemical properties distinct from those of the globulin storage proteins. They play an additional and unique role of providing sulfur reserve for germination.     

DETERMINATION OF CERTAIN AMINO ACIDS IN CHYMOTRYPSINOGEN,AND ITS MOLECULAR WEIGHT

1. A preparation of chymotrypsinogen, obtained from Dr. M. Kunitz, was analyzed for sulfur, the sulfur amino acids, tyrosine, and tryptophane. 2. The protein sulfur of chymotrypsinogen was accounted for as methionine, cysteine, and cystine. 3. A method is presented for calculating the minimum molecular weight of a protein from the distribution of the sulfur amino acids. In the case of chymotrypsinogen, the calculated minimum molecular weight was found to be the actual molecular weight. 4. The molecular weight of chymotrypsinogen is 36,700 by amino acid analysis as compared to 36,000 by osmotic pressure measurements of Kunitz and Northrop. Chymotrypsinogen contains per mol 17 atoms of sulfur, 3 residues of methionine, 4 of cysteine, 10 of half-cystine (i.e. 5 S—S linkages), 6 of tyrosine, and 10 of tryptophane. 5. The tryptophane content of chymotrypsinogen (5.51 per cent) is the highest of any protein so far on record. 6. Chymotrypsinogen contains no reactive SH groups, although it yields cysteine on hydrolysis. This may be due either to preformed but unreactive SH groups or to S—X groups. The term S—X group is used to denote the substitution of the sulfhydryl hydrogen by a constituent X; hydrolysis yields SH groups: S—X + HOH = SH + X—OH.     

MOLECULAR WEIGHT AND ELECTROPHORESIS OF CRYSTALLINE RIBONUCLEASE

Electrophoretic studies on purified crystalline ribonuclease showed the absence of any impurities differing in mobility from the bulk of material. The isoelectric point of ribonuclease was found by electrophoresis to be at about pH 7.8. Ultracentrifuge studies indicated fair homogeneity of ribonuclease in solution. Only one moving component has been observed. The molecular weight of ribonuclease was found to be 12,700 from rate of sedimentation (S ²⁵ = 1.85 x 10^–13 in 0.5 M (NH₄)₂SO₄) and diffusion measurement (D = 1.36 x 10_–6 in 0.5 M (NH₄)₂SO₄), in good agreement with the average value of 13,000 found from equilibrium measurements. This low value for the molecular weight of a protein would seem to discredit the value 17,600 as representing a universal unit weight for proteins in general.     

火菇素的分离纯化及其分子量的测定*

火菇素是一种从金针菇FlammulinaVelutipes中分离纯化出来的具有抗癌活性的简单蛋白。用SDS-PAGE系统,通过与已知分子量的标准参照蛋白比较,确定火菇素的分子量为24kDa,这一结果与其氨基酸组成分析相比偏大,进一步通过电喷雾离子化质谱法(ESIMS)分析,精确测定火菇素的分子量为19891.13Da。推测由于火菇素蛋白与SDS的非正常结合是造成蛋白质在SDS-PAGE中迁移变慢导致偏差的原因。     

中国葡萄属植物叶绿体DNA的提取、纯化及分子量测定

分离出纯化的叶绿体ＤＮＡ｛ｃｐＤＮＡ）,基因组的文库便能建成,特定基因便能分离,其顺序便可进一步测定。然而,我们的研究经验表明,最常用制备纯化ｃｐＤＮＡ的方法很难应用于葡萄属的种类。本文提出了一个分离和提纯葡萄属ｃｐＤＮＡ的方法,这个方法不同于其它方法主要在于：１．偏重亚硫酸钠与巯乙醇和维生素Ｃ一起加在缓冲液中,使与溶液中的氧结合,以防止游离氧氧化单宁和其它次生物质呈显色反应;２．在高盐溶液中使用加热处理,达至８５℃为止,灭活氧化酶类,消除氧化条件。用其它科属的种类,菠菜和油菜作对比,提取和纯化了葡萄属不同类型种的ｃｐＤＮＡ,均取得了较好的结果。将提纯的中国葡萄各种的ｃｐＤＮＡ,用菠菜和油菜作比较,以λＤＮＡ作对照,经限制性酶ＢａｍＨＩ,ＳａｌＩ＋ＸｈｏＩ和ＰｓｔＩ＋ＫｐｎＩ酶解,电泳分离,扫描定量,采用描图法测定了ｃｐＤＮＡ各片段的分子量,总和约１３０ｋｂ,同时测定了菠菜和油菜的ｃｐＤＮＡ分子量。     

THE MOLECULAR WEIGHT AND ISOELECTRIC POINT OF THYROGLOBULIN

1. The sedimentation constant of hog thyroglobulin is 19.2ċ10^–13. That of human thyroglobulin is essentially the same. 2. The specific volume of hog thyroglobulin is 0.72. 3. The isoelectric point of native hog thyroglobulin is at pH 4.58, that of denatured thyroglobulin at pH 5.0. 4. The molecular weight of hog thyroglobulin is, in round numbers, 700,000, as calculated from the sedimentation and diffusion constants, or 650,000, as calculated from the sedimentation equilibrium data. 5. The thyroglobulin molecule deviates markedly from the spherical.     

叶绿体小分子RNA的分离纯化和鉴定

本文采用低速匀浆、过筛的方法从植物叶中分离得到了完整、纯净的叶绿体。将叶绿体与提取缓冲液、苯酚混合匀浆抽提叶绿体 RNA。通过聚丙烯酰胺凝胶电泳与文献已发表的已知酵母5S RNA、菠菜叶绿体4.5S RNA 及小麦5S RNA、4.5S RNA 的电泳迁移距离进行比较,发现芹菜叶绿体中小分子 RNA(沉降系数为5S 左右的 RNA)中除含有5S RNA 和4S RNA 外,还含有两种4.5S RNA。而水杉和银杏叶绿体小分子 RNA 中只含有5S RNA 和4S RNA。     

昆虫分子生物学的一些进展：胚胎发育飞丝蛋白与可诱导的抗菌蛋白

胚胎发育中的基因调控 从一个受精卵发育成一个多细胞的个体,涉及许多基因,其表达有时间上的程序和空间上的限制。调控果蝇(Drosophila melanogaster)胚胎发育的基因已研究得很详细,包括三大类调控基因——母体基因、分节基因和同源异形基因。在早期发育中,这三类基因相继起作用,前一类基因的产物依次调节下类基因的表达,组成一个调控等级网(或称     

运动后尿液蛋白质分子量与等电点的变化特征

通过对９名男性受试者在分别完成１００－２００ｍ,４００－８００ｍ和１ ５００－３ ０００ｍ跑步间歇训练后尿蛋白分子量和等电点的测定发现：①运动时尿液高、低分子量蛋白质排泄率均较运动前明显增加,但以高分子量蛋白质排泄为主;②运动时尿液高、低分子量蛋白质排泄率均以４００－８００ｍ间歇训练时最高,１００－２００ｍ间歇训练时次之,１ ５００－３ ０００ｍ间歇训练时最低;③运动时尿液排出的蛋白质以负离子为主     

三种寄生蜂虫体可溶性蛋白组成及蝶蛹金小蜂卵黄蛋白的分子特性分析(英文)

聚丙烯凝胶电泳PAGE和毛细管电泳分析结果表明 ,蝶蛹金小蜂雌蜂个体和卵巢中明显存在雌性特异蛋白 ,即卵黄蛋白。但茧蜂科的螟长距茧蜂Macrocentruslinears和菜蛾盘绒茧蜂Cotesiaplutella雌雄虫体可溶性蛋白间无明显差异。SDS PAGE梯度电泳结果表明 ,蝶蛹金小蜂卵黄原蛋白 (Vg)和卵黄磷蛋白 (Vt)均由二个分子量接近的亚基组成 ,分子量各为 74 4和 5 2 8KD。双向免疫扩散和PAGE梯度电泳都显示该蜂隐成蜂的雌性虫体及雌蜂血淋巴、脂肪体和卵巢中都有Vg或Vt,且卵黄原蛋白是由雌蜂脂肪体合成     

THE SWELLING OF GELATIN AND THE VOLUME OF SURROUNDING SOLUTION

The swelling of isoelectric gelatin added to various volumes of acid of different concentration at 5°C. has been determined. The swelling is determined only by the concentration of the supernatant solution at equilibrium and is independent of the volume of acid. Similar experiments with unpurified gelatin show that in this case, owing to the presence of neutral salts the swelling is a function of the volume as well as the concentration of acid. Both results are predicted by the Procter-Wilson-Loeb theory of the swelling of gelatin.     

ANALYSIS OF THE SOLUBLE PROTEINS IN THREE SPECIES OF PARASITOIDS AND MOLECULAR CHARACTERISTICS OF YOLK PROTEIN IN PTEROMALUS PUPARUM*

Abstract The results both from PAGE and capillary electrophoresis indicated that there was a female specific protein i.e. vitellogenin (Vg) or vitellin (Vt) in the female wasp of Pteromalus puparum (Hymenoptera: Pteromalidae). While there was no difference in the electrophoresis graph between soluble proteins of the female whole body and those of the male one both in two bracoids (Hymenoptera: Braconidae), i.e. Cotesia plutellae and Macrocentrus linears. According to the graph of the gradient SDS‐PAGE, it was clear that the Vg or Vt of P. puparum consisted of two subunits with approximate molecular weights, and their molecular weights were 74.4 and 52.8 KDa, respectively. Both immunological reactions between some main different tissues of the female wasps and the male whole body and the polyantibody against the Vt of this parasitoid, and the graph of the gradient SDS‐PAGE including soluble proteins sampled separately from hemolymph, fat body and ovary of the female and the whole body of the male demonstrated that Vg existed both in female fat body and hemolymph, and Vt deposited in the ovary, not in the male, as well as the Vg was synthesized in the female fat body.     

分子伴娘60类群的系统发育学分析

有充分的证据支持线粒体和叶绿体起源的内共生假说,即:紫色细菌、α—类群的成员是线粒体的祖先,而蓝细菌的成员是叶绿体的祖先。这一证据来自分子伴娘60蛋白为基础的系统发育学分析,并且与16S rRNA序列为基础的分析结果是完全一致的。这一结果还说明,嗜碱芽胞杆菌C-125菌株在系统发育地位上更接近枯草芽孢杆菌。