Atrial natriuretic factor: atrial conversion of high to low molecular weight forms

The atrial natriuretic factor elutes by gel filtration in high and low molecular weight fractions. Extraction and elution of rat atria in 1.0 M acetic acid yielded a predominance of the high molecular weight form(s); whereas when these procedures were carried out in 0.1 M acetic acid, there was a predominance of the low molecular weight forms. When partially purified high molecular weight natriuretic activity was eluted in 0.1 M acetic acid, the high molecular weight form(s) remained intact. When partially purified high molecular weight natriuretic activity was mixed with crude atrial extract in 0.1 M acetic acid, there was an apparent conversion to the low molecular weight forms. Extraction of rat atria in boiling 0.1 M acetic acid blocked this conversion. It is concluded that rat atria contain a heat labile factor that converts high molecular weight natriuretic activity to the low molecular weight forms.     

Molecular distribution of zinc in biliary and pancreatic secretions

Rat bile and pancreatic fluid were examined for the presence of low molecular weight zinc complexes. Fluids were collected separately by cannulation, and zinc distribution in collected samples was analyzed by gel filtration on Sephadex G-50. Most of the zinc in bile was associated with low molecular weight zinc complexes; only a small amount of zinc was present in the high molecular weight fraction. In contrast, pancreatic secretions did not contain low molecular weight zinc complexes, but there were considerable amounts of zinc bound to high molecular weight compounds. The addition of zinc to bile resulted in an increased amount of zinc in the low molecular weight fraction, while the addition of zinc to pancreatic fluid resulted primarily in an increase in zinc bound to the high molecular weight components. Like pancreatic fluid, homogenates of pancreatic tissue had no low molecular weight zinc complex. In rats whose bile and pancreatic fluid were removed and not returned into the intestine, the amount of zinc bound to low molecular weight complexes in intestinal homogenates was reduced. This alteration of the molecular distribution of zinc in intestinal homogenates by removal of bile and pancreatic fluid suggests the potential importance of low molecular weight zinc complexes for zinc homeostasis.     

Directional Ca2+ effect on stimulation of secretion of common mucins and unique sulphate-rich components from chicken trachea in vitro

High submucosal Ca2+ (3.6-18 mM) significantly increased the secretion of a common high molecular weight fibrillar mucin (approx. Mr is greater than 2.10(6)) and also elicited the secretion of an additional low molecular weight component (approx. Mr 325,000). Low luminal Ca2+ (0.018 mM) also significantly increased the secretion of a common high molecular weight gelatinous mucin (approx. Mr is greater than 2.10(6)) and elicited the secretion of an additional low molecular weight component (approx. Mr 46,200). The additional low molecular weight components were more heavily sulphated (6.7 and 4.2%) than common high molecular weight mucins (2.1 and 1%). The low molecular weight components and high molecular weight mucins were secreted as aggregates which could be dissociated by EGTA. The low molecular weight components and high molecular weight mucins were different in the number of their glycoprotein constituents and in the ion-exchange chromatographic profiles and the carbohydrate and ester sulphate residue content of their acidic glycoproteins.     

Viscosimetric studies on molecular weight fractions of fulvic and humic acids of aquatic,terrestrial and microbial origin

Summary Viscosities were investigated of solutions of fulvic and humic acid molecular weight fractions of aquatic, terrestrial and microbial origin. Aquatic fulvic and humic acid molecules were, at pH 7, more voluminous than other types of humic compounds of similar molecular weight. It would appear that in low molecular weight non-aquatic humic matter, more inter- than intra-molecular bonding is present, with increasing molecular weight the bonding becomes more intra-molecular. Differences between average molecular weight values as obtained by an ultrafiltration method (Amicon) and by viscosimetry ranged from –18.7 to 18.5%. The largest deviations were in the low molecular weight range (<5,500 daltons). Higher molecular weight humics (in particular humic acids) appeared to have a more elongated structure than lower molecular weight material (in particular fulvic acids). Indications were obtained that on hydration humic moleculars become more elongated.     

Yeast RNA partition accompanying adsorption in salt/PEG two-phase system

Summary Partitioning of yeast total RNA in a salt/PEG two-phase system, i.e., a potassium phosphate/PEG system and a ammonium sulfate/PEG system, was characterized with regard to the dependence on the molecular weights of PEG and RNA. The shift in RNA partitioning was investigated for a PEG molecular weight range from 300 to 20000. RNA was partitioned mainly to the top phase in the system with PEG of a molecular weight up to 1000, mainly at the interface or almost equally to both phases in the system with PEG of a molecular weight 1000–2000, and mainly to the bottom phase in the system with PEG of more than 2000 in a molecular weight . The effect of PEG molecular weight on partitioning of low molecular weight RNA, less than 5.8S molecule, was qualitatively similar to that of high molecular weight RNA, more than 17S molecule. However, partitioning of high molecular weight RNA was more one-sided than that of low molecular weight RNA. In the system with PEG1000–2000, remarkable adsorption of high molecular weight RNA at the interface was investigated; more than 90% of the high molecular weight RNA added was concentrated. Adsorption of RNA at the interface was quantitatively demonstrated as a novel example of adsorption of a soluble macromolecule in an aqueous two-phase system.     

Multiple molecular forms of glia maturation factor.

Glia maturation factor from the pig brain can be detected in two molecular forms: the high molecular weight form which is 200 000 dalton in size and the low molecular weight form which is 40 000 dalton in size, as determined by Sephadex gel filtration. The former accounts for 85% of the total biological activity extracted at physiologic pH. The proportion of the low molecular weight form increases following freeze-thawing and ion-exchange chromatography. In addition to the morphological effects, both forms possess mitogenic activity but no esteropeptidase activity. Both forms show similar enzyme susceptibility, being inactivated by papain, ficin and pronase but resistant to subtilisin, thermolysin and trypsin. The high molecular weight form is more resistant to denaturation by low pH, heating and urea than the low molecular weight form. The high molecular weight factor has an isoelectric point of 4.27 whereas the low molecular weight factor has one of 5.04.     

Subcellular localization of high- and low-molecular weight acid phosphatases from chicken liver

The subcellular localization of high and low molecular weight acid phosphatases in chicken liver was studied. The high molecular weight acid phosphatase is mainly associated with the particulate fraction, particularly with the mitochondrial-lysosomal fraction, whereas the low molecular weight form seems to be a soluble cytoplasmic enzyme. Biochemical properties including optimal pH, molecular weight determination and the effect of some modifier substances indicate that mitochondria-lysosomes and microsomes contain the same high molecular weight acid phosphatase form.     

Calcification inhibitors in rat and human serum and plasma

Rat and human serum and plasma were shown to contain considerable amounts of calcium phosphate precipitation inhibitors. Two general classes of inhibiting molecules were observed for both species: high molecular weight (approx. 30 000-200 000) and low molecular weight (less than 1000). The high molecular weight components eluted from a Bio-Gel P-200 column in two peaks, one at approx. 158 000 and a broader peak at approx. 43 000. The identity of these inhibitors is unknown at present. Low molecular weight inhibitors include magnesium, pyrophosphate, and citrate ions and at least one unidentified component that coelutes with pyrophosphate and citrate on a Bio-Gel P-4 column. Quantitatively, most of the inhibitor activity resides in the high molecular weight components and it is possible that it is this activity which is responsible for maintaining the metastability of the circulating fluids. The role of the low molecular weight components may be to regulate calcification at sites inaccessible to high molecular weight molecules.     

The influence of humic substances on the molecular weight distributions of phosphate and iron in epilimnetic lake waters

1. The influence of humic substances on the association of free inorganic iron and phosphate with material of larger molecular weight was investigated in epilimnetic samples from two humus‐rich lakes of contrasting ionic strength. After modification of the molecular weight distribution of the humic substances in the samples using dialysis and ultrafiltration, the molecular weight distribution of added radioisotopes ( Fe3+ and PO43?) was assessed using gel filtration chromatography.
2. The association of Fe3+ and PO43? with larger molecular weight fractions (>50 000 and 10 000–50 000 Da) was not in general related to the quantity of humic substances of the same molecular weight in the samples. However, the proportions of Fe3+ and PO43? observed in higher molecular weight peaks were strongly correlated to the quantity of humic substances of the same molecular weight in (a) the 10 000–50 000 Da peak in the sample of low ionic strength at pH 5.5 and pH 7.0, and (b) the> 50 000 Da peak in the sample of higher ionic strength at pH 4.0.
3. It was concluded that humic substances promote the association of Fe3+ and PO43? with higher molecular weight fractions primarily by acting as peptizing agents for inorganic colloids containing Fe and P. Association of Fe3+ and PO43? with material of higher molecular weight via the formation of humic substance‐Fe3+–PO43? complexes was identified but only at specific pH and within specific molecular weight ranges for each of the epilimnetic lake water samples studied.     

Yeast pheromone alpha-factor is synthesized as a high molecular weight precursor

The sex pheromone alpha-factor of Saccharomyces cerevisiae, a tridecapeptide of approx. 1,700 molecular weight, was found to be synthesized in vivo as a high molecular weight precursor of Mr = 28,000. Inhibition of N-linked glycosylation by tunicamycin leads to three precursor species of lower molecular weight indicating three carbohydrate residues linked to the alpha-factor precursor molecule. A molecular weight of 18,000 was determined for the unglycosylated molecule.     

Molecular weight of Escherichia coli β-galactosidase in concentrated solutions of guanidine hydrochloride

The molecular weight of Escherichia coli beta-galactosidase was determined in 6m- and 8m-guanidine hydrochloride by meniscus-depletion sedimentation equilibrium, sedimentation velocity and viscosity. Sedimentation equilibrium revealed heterogeneity with the smallest component having a molecular weight of about 50000. At lower speeds, the apparent weight-average molecular weight is about 80000. By use of a calculation based on an empirical correlation for proteins that are random coils in 6m-guanidine hydrochloride, sedimentation velocity gave a molecular weight of 91000, and the intrinsic viscosity indicated a viscosity-average molecular weight of 84000. Heating in 6m-guanidine hydrochloride lowered the viscosity of beta-galactosidase in a variable manner.     

The molecular weight of J chains derived from human immunoglobulin M

J chain was isolated from sulphonated human immunoglobulin M molecules by electrophoresis on polyacrylamide gels. When determined by electrophoresis in sodium dodecyl sulphate-polyacrylamide gels, the molecular weight of the protein was about 27000. After suspension in 5m-guanidine hydrochloride solution for 21 days, two groups of three bands appeared on the gels. Most of the protein dissociated to components of molecular weight 15000. The molecular weight of purified J chain was also determined by ultracentrifugation. In borate-saline solution the average weight-average molecular weight was about 29000. The molecular weight slowly decreased upon prolonged exposure to guanidine hydrochloride, and after 14 days the minimum molecular weight was about 15000. Some association between chains still existed. These data suggest that J chain derived from the paraprotein exists in borate-saline solution as dimers held by strong non-covalent forces.     

壳聚糖对植物病原细菌的抑制作用研究

本文通过测定最小抑制浓度和相对抑制率,观察了分子量和脱乙酰度对壳聚糖抑制植物病原细菌(胡萝卜软腐欧文氏菌Erwinia cartovara Var carotovara、油菜黄单孢菌绒毛草致病菌Xanthamonas campestris Pv holcicola、丁香假单孢菌黍致病变种Pseudomonas spyings Pv panici)作用的影响。结果表明：在一定范围内,随分子量和脱乙酰度的增大,壳聚糖的抑菌效果相应降低,而且各种病原细菌对不同,壳聚糖的敏感性也有很大差异。     

Isolation, fractionation, and preliminary characterization of a novel class of sulfated glycans from the tunic of Styela plicata (Chordata Tunicata)

The sulfated glycans in the tunic of Styela plicata differ from the glycosaminoglycans of animal tissues and also from the sulfated polysaccharides isolated from marine algae. The ascidian glycans occur primarily as three fractions that differ markedly in molecular weight and chemical composition. The high molecular weight fraction encompasses a broad range of molecular weights but is chemically homogeneous and contains an unusual amount of galactose. The 20,000 molecular weight polysaccharide is rich in galactose and glucose while the 8,000 molecular weight fraction is rich in amino sugars and contains the neutral hexoses galactose, glucose, and mannose. All fractions contain large amounts of sulfate esters. The ascidians polysaccharides can be extracted from the tissue by proteolytic enzyme or by guanidine hydrochloride solutions. The high molecular weight fraction is preferentially extracted by papain while guanidine hydrochloride removes mainly the low molecular weight polysaccharides. We speculate that these sulfated glycans are essential for maintaining the structural integrity of the tunic, in analogy with the glycosaminoglycans of vertebrate connective tissues.     

Molecular weight distribution of carrageenans by size exclusion chromatography and low angle laser light scattering

A procedure to determine the absolute weight average molecular weight and molecular weight distribution of carrageenans by high pressure aqueous size exclusion chromatography coupled with low angle laser light scattering is described. Experimental parameters are successively discussed, particular attention being focused on the absence of shear degradation during elution. The distribution curves were highly reproducible in time and weight average molecular weights integrated along the chromatogram were in good agreement with static light scattering results. A large difference in the molecular weight range between native (food-grade) and acidic degraded carrageenan samples was observed. Weight average molecular weights were found to be in good correlation with viscosity values, for degraded as well as undegraded products. It is also shown that the method described can help people using carrageenans in pharmacological studies by providing information on the real molecular weight distribution of the products they are employing.     

Application of sodium dodecyl sulfate-gel electrophoresis to low molecular weight polypeptides

Experiments with nine polypeptides with molecular weights between 2000 and 10,760 confirm the value of sodium dodecy sulfate (SDS)-gel electrophoresis for separating polypeptides in this molecular weight range. In one case, electrophoretic blotting and microsequencing were successfully carried out. However, molecular weight determination in the low molecular weight range (less than 10,000) is much less reliable than that in the conventional molecular weight range (greater than 10,000) for SDS gels. Information provided by suppliers of horse heart myoglobin fragment kits is potentially misleading.     

DNA分子量标准制备技术：方法与进展

DNA分子量标准是一组分子量大小已知的DNA片段混合物,用于指示核酸电泳中未知样品的分子量大小,从而帮助实验人员判断DNA样品的性质。因而DNA分子量标准成为目前分子生物学和基因工程领域不可或缺的一种电泳耗材。综述了目前各种DNA分子量标准产品的制备方法和技术原理及近年来该领域的一些技术进展情况。     

Kallikrein activation of a high molecular weight atrial peptide

Mammalian atrial extracts contain bioactive peptides that exert profound effects upon renal function and isolated smooth muscle preparations. Gel filtration chromatography of rat atrial extract separates the activity into two peaks having apparent molecular weights of 20,000 to 30,000 and less than 10,000. Mild proteolytic treatment (trypsin 1 U/ml) of the high molecular weight fraction enhances the smooth muscle relaxant activity of this fraction and concomitantly reduces the apparent molecular weight of this fraction to less than 10,000. In this report we show that urinary and submaxillary kallikrein enhances the activity of rat atrial extracts in a similar fashion. Pretreatment of the high molecular weight fraction with either kallikrein (1 microgram/ml) enhances the smooth muscle relaxant activity of this fraction. Similar treatment of the low molecular weight fraction had no effect. The enhancement of the bioactivity of the high molecular weight substance(s) by the kallikreins was abolished by aprotinin but was unaffected by soybean trypsin inhibitor. These results suggest that exogenous addition of tissue kallikrein activates a high molecular weight peptide by limited proteolysis. Analysis of the kallikrein-treated high molecular weight peptide fraction by gel filtration indicates that the biological activity comigrates with the low molecular weight peptides present in the original atrial extract.     

Combination of affinity chromatography and analytical polyacrylamide gel electrophoresis for rapid measurement of human serum high-density lipoprotein apoproteins

Heparin of an average molecular weight of 13,000 was fractionated on the basis of size into five fractions of different weight-average molecular weight ranging from 8500 to 20,000. The heparin was also degraded using microbial heparinase resulting in products ranging from a disaccharide of molecular weight 500 to an oligosaccharide of molecular weight 3100. These products were also size fractionated. The individual heparin fractions and products were tested for metachromatic activity with Azure A. The metachromatic activity of the heparin fractions was independent of molecular weight, while the metachromatic activity of the products was dependent on molecular weight. Metachromatic activity was found in a fragment as small as a tetrasaccharide. Anticoagulant activity was found in fragments of tetrasaccharide or larger by a Factor Xa clotting assay and in fragments of hexasaccharide or larger by a Factor Xa amidolytic chromogenic assay.     

低分子硫酸软骨素在兔软骨修复过程中对IL-1β、TNF-α和TGF-β及钙磷的影响(英文)

目的:探讨低分子量硫酸软骨素(CS)在兔软骨修复过程中对于IL-1β、TNF-α和TGF-β及血液中钙磷含量的影响。方法:36只成年新西兰大白兔,随机分成6组,分别为对照组、模型组、低分子量CS低剂量组、低分子量CS高剂量组、高分子量CS低剂量组、高分子量CS高剂量组,每组6只。通过在实验兔股骨髁关节面部位,钻出直径3mm,深度3mm的缺孔,造成其关节软骨的缺损。术后次日给予药物进行灌胃,每日1次,5周后取材。采用酶联免疫法测定关节液中IL-1β、TNF-α和TGF-β的含量,同时用全自动生化分析仪及其配套的试剂盒来测定兔血清中钙,磷含量。结果:低分子量CS和高分子量CS都能够减少关节液中炎性因子的含量和增加TGF-β的含量,且与模型组相比具有统计学意义(P0.05);同时低分子量CS与高分子量CS相比效果较好(P0.05);而高低剂量之间无统计学意义(P0.05)。与模型组相比,给予CS的组别,其血清中的钙磷含量相对较少(P0.05),但都高于对照组。结论:高、低分子量的CS都可以增加TGF-β的含量,降低IL-1β、TNF-α和血清中钙、磷的含量。而对于软骨修复,这可能是通过对上述因子的影响,从而产生积极的作用。