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1.
Chicken erythrocyte chromatin was partially digested with micrococcal nuclease and separated into multimeric subunit fractions by gel permeation chromatography. The fractions were characterized by their Svedberg constant, diffusion coefficient, circular dichroism, and electrophoresis pattern of the extracted DNA. The molecular weight dependence of the sedimentation coefficient was found to be S20,w = .011 × M.554. The molecular weight dependence of rmffo is best represented in the Kirkwood theory by either a helical superstructure or a flexible coil withattractiveinteractions between nucleosome units. The dimer calculations of ffo suggest that the core particles are separated by spacer regions which contribute up to ~20% of the frictional properties of the molecule.  相似文献   

2.
A series of pullulan fractions with molecular weights in the range 5 × 103 to 8 × 105 were prepared. The weight-average molecular weight (Mw) of all the samples was determined by sedimentation equilibrium. The hydrodynamic properties of pullulan in aqueous solution were investigated by viscometry and ultracentrifugation. The experimental results indicate that pullulan molecules in water are fairly stable and behave as expanded random coils when Mw is above 2 × 104. The molecular weight distributions of the fractions were measured by gel filtration. The ratio Mw/Mn was close to 1·1, except for a sample with the highest Mw.It is concluded that the pullulan fractions prepared by the present work are well characterized and have a narrow molecular weight distribution. They may be useful as standard samples for studies of water-soluble polymers.  相似文献   

3.
The molecular weight (Mw) and molecular-weight distribution of the extracellular polysaccharide xanthan, synthesized by the bacterium Xanthomonas campestris, have been determined from measurements of the sedimentation coefficient, s20,itw, and the intrinsic viscosity, [η], with the aid of the Mandelkern-Flory-Scheraga equation. The sedimentation coefficient of native xanthan was measured by band-sedimentation of polysaccharide molecules that had been tagged with a fluorescent group; the fluorescent label permits the use of very low concentrations of polymer. A typical, native-xanthan sample has Mw  15 x 106; the polydispersity index Mw/Mn is 2.8. Measurement of s and [η] for a homologous series of five xanthan samples having Mw ranging from 0.40 to 15 X 106, prepared by sonication of native xanthan, shows that, for low molecular weight, the intrinsic viscosity [η] obeys the relation [η]  KM1.35. The high value of the Staudinger exponent in this relation demonstrates that xanthan is a rod-like molecule having stiffness similar to that of native DNA, which has a Staudinger exponent of 1.32. Moreover, the absolute values of [η] suggest that xanthan has a mass per unit length of about 1900 daltons/nm, which is twice the mass per unit length of the single-stranded structure proposed from X-ray work.  相似文献   

4.
The structure of the condensed tannins of the most common fodder legumes is described. The number- (Mn) and weight-average (Mw ) MW of the polymers have been determined and most legume tannins have an approximately normal distribution of MWs with Mn values of 2000–4000.  相似文献   

5.
The polysaccharides of cranical cartilge were isolated by ethanol precipitation after papain digestion and β-elimination procedures and were fractionated chromatographically on CPC-cellulose. In addition to the previously described, heavily oversulphated chondroitin sulphate, the tissue contained small amounts of hyaluronic acid, which, however, co-eluted with the chondroitin sulphate from the CPC-cellulose. Approx. 20% of the isolated polysaccharides consisted of an acidic polysaccharide which to our knowledge is not previously described. This polysaccharide consists mainly of glucuronic acid, galactose and mannose in a molar ratio of 1:2:1. Gel chromatography of the preparation indicated a polydisperse molecule with an apparent average molecular weight of 39200 on weight basis (Mw) and 31400 on number basis (Mn).  相似文献   

6.
The molecular weight of the adenovirus type 2 hexon was calculated from sedimentation equilibrium, light scattering and sedimentation and diffusion experiments. The extinction coefficient, E1 cm1%, was determined to be 14.3 at 279 nm, from quantitative nitrogen and carbon analyses combined with the N,C content calculated from the amino acid composition. Other parameters determined were: the partial specific volume, \?gn = 0.738 cm3 g?1; the refractive index increment, (?n?c)T,P = 0.193 cm3 g?1 at 435.8 nm; the sedimentation coefficient, s20,w0 = 13.0 S; and the diffusion constant, D20, w0 = 3.32 × 10?7 cm2 s?1. All molecular weights were between 355,000 and 363,000. Crystal density measurements were made on native and glutaraldehyde cross-linked crystals and the molecular weights calculated from these data were compared with the precise molecular weight determined by physico-chemical methods.Only one polypeptide of molecular weight 120,000 was found in reduced, or reduced and alkylated, hexon. Four or six organomercurial molecules were bound per 120,000 molecular weight of native hexon upon titration with 2-chloromercuri-4-nitrophenol and 2-chloromercuri-4,6-dinitrophenol, respectively. With 5,5′-dithiobis (2-nitrobenzoic acid) only one SH-group per 120,000 could be titrated in native hexon, but after denaturation in 1% sodium dodeeyl sulphate five more SH-groups reacted per 120,000 molecular weight. Thus there are three identical polypeptides of molecular weight 120,000 per hexon of total molecular weight 360,000.  相似文献   

7.
Different methods of precipitation of arabic acid from natural gum arabic are compared in terms of yield and molecular weight derived from gel chromatography experiments. All of the precipitation methods used gave products which were closely similar in terms of Mn, but precipitation with HCl/acetone and HAc/ethanol gave low yields (25 and 3%, respectively).  相似文献   

8.
Native calf thymus DNA was sheared by sonication in a viscous solvent to the molecular-weight range from 3 × 104 to 3 × 105 daltons, and fractionated by gel chromatography. Number and weight average molecular weights (M?n and M?w) were determined for individual fractions by electron microscopy; the ratio M?w/M?n for the peak fraction is approximately 1.1. Sedimentation coefficients (s020,w) of these fractionated samples show an approximately linear dependence on the logarithm of the molecular weight M?w. This behavior is that expected for rodlike molecules, and is in quantitative agreement with the theory of Yamakawa and Fujii [(1973) Macromolecules 6 , 407–415] for the sedimentation coefficient of a wormlike chain with a persistence length of 625 Å, a diameter of 25 Å, and a mass per unit length of 195 daltons/Å. It appears that the wormlike coil model, without excluded volume, can represent the sedimentation behavior of DNA over the entire conformational range from rigid rod to flexible coil, using the above parameters. Equilibrium melting curves were determined for various fractions in aqueous 2.4 M tetraethylammonium bromide. A substantial broadening of the transition and decrease of the melting temperature were observed with decreasing molecular weight. Empirical expressions have been obtained relating both the transition temperature and breadth in this solvent to molecular weight.  相似文献   

9.
Heterogeneity in molecular weight and degree of deacetylation (DDA) of chitosans from different sources and preparation methods were studied by fractionating chitosans, using semi-preparative SEC, and then determining molecular weight profiles of fractions by analytical SEC with multi-angle laser light scattering (SEC–MALLS), and degree of deacetylation (DDA) by 1H NMR. Fractionation of two high molecular weight chitosans from different manufacturers, produced fractions that spanned a wide range of molecular weight (number-average Mn), from 65 to 400 kDa in one case, that was not evident when unfractionated material was directly analyzed by SEC providing Mn = 188 kDa and PDI = Mw/Mn = 1.73. In a second case, fractions ranged from 20 to 600 kDa with unfractionated Mn = 145 kDa and PDI = 1.83. Fractionation of low molecular weight chitosans also showed a broad range of molecular weight in the original material, however, the fractions obtained with the TSKgel G4000W column in the Mn range of 5–100 kDa were essentially monodisperse with PDIs between 1.0 and 1.4. The DDA of one low molecular weight chitosan (10 kDa) produced by nitrous acid degradation was dependent on the Mn of the fraction. This semi-preparative fractionation procedure revealed important compositional heterogeneities of chitosans not evident in unfractionated material, and permitted the production of monodisperse low molecular weight chitosans with homogeneous properties.  相似文献   

10.
Molecular characteristics for pullulan, a polysaccharide produced by a fungus Aureobasidium pullulans, were measured by light scattering, viscometry, and gel-permeation chromatography. From the experimental data the Mark-Houwink-Sakurada viscosity equation in water at 25°C was determined for samples having the molecular weight M ranging from 48 × 103 to 2.18 × 106 g mol?1 as [η] = (1.91 ± 0.02) × 10?2Mw0.67±0.01 (in cm3 g?1); and as molecular weight decreased, the slope of the viscosity equation decreased, although the molecular weight values below 30 × 103 g mol?1 evaluated by gel-permeation chromatography were somewhat unreliable. The unperturbed dimensions 〈R201/2 of pullulan were estimated by determining the expansion factor αs, from the theoretical combination of theories for the interpenetration function Ψ and those for αs. The 〈R20/M value estimated from this procedure in 6.7 × 10?17 cm2 mol g?1. We concluded that the polysaccharide chain that is linked by the α-1,6-glucosidic linkage behaves like a flexible chain in aqueous solution.  相似文献   

11.
The insecticidal toxin of Bacillusthuringiensis subsp. kurstaki was isolated from parasporal crystals. The toxin, which is stable for several months, is a glycoprotein with an apparent molecular weight of 68,000 that is generated upon solubilization and activation of a higher molecular weight protoxin (MWapp = 1.3 × 105) at alkaline pH. The toxin was purified by gel filtation and anion exchange chromatography and its molecular weight was established by gel filtration chromatography and SDS polyacrylamide gel electrophoresis.  相似文献   

12.
This paper reports the first detailed study of the physicochemical properties of a fatty acid synthetase multienzyme complex from a mammalian liver. Fatty acid synthetase from pig liver was purified by a procedure including the following main steps: (i) preparation of a clarified supernatant solution (50,000 g), (ii) ammonium sulfate fractionation, (iii) DEAE-cellulose chromatography to separate 11 S catalase from the 13 S fatty acid synthetase, (iv) a preparative sucrose density gradient step to remove a 7 S impurity, and (v) a calcium phosphate gel step to remove an unusual yellow 16 S heme protein to yield a colorless preparation. The purified fatty acid synthetase was colorless and showed a single symmetrical peak in sucrose density gradient and conventional sedimentation velocity experiments. Fatty acid synthetase was very stable at 4 °C in the presence of 1 mm dithiothreitol and 25% sucrose. Extrapolation to zero protein concentration yielded values of So20,w = 13.3 S and Do20,w = 2.60 × 10?7cm2/s for the sedimentation and diffusion coefficients of the enzyme. Frictional coefficient values of 1.55 and 1.56 × 10?7 cm, respectively, were calculated from the values for the sedimentation and diffusion coefficients. Based on these frictional coefficient values, the Stokes radius of the enzyme was calculated to be 82.4 Å. Sedimentation and diffusion coefficient data yielded a molecular weight value of Mw (sD) = 478,000 and sedimentation equilibrium data yielded a value of Mw = 476,000. Preliminary intrinsic viscosity measurements at 20 °C gave a value of 7.3 ml/g, indicating that the enzyme is somewhat asymmetric. This is supported by the value of 1.58 calculated for the frictional ratio and by the fact that the values for the sedimentation and diffusion coefficients are both slightly lower than expected for a globular protein of molecular weight 478,000. The enzyme possesses about 90 SH groups per molecule, assuming a molecular weight of 478,000. The ultraviolet absorption spectrum of the enzyme shows a maximum at 280 nm and an unusual shoulder at 290 nm. The fluorescence spectrum of the enzyme is dominated by tryptophan fluorescence and, over the excitation range of 260–300 nm, there is a single emission maximum at 344 nm.  相似文献   

13.
Summary Biocatalytic synthesis of polyester of the type (AA-BB)h using a new diester, viz bis(2, 3 butane dione monoxime) alkane dioate by lipase catalysed transesterification with different primary diols has been studied. Weight average molecular weight (Mw) of the polyester was analysed by gel permeation chromatography (GPC). Number average molecular weight (Mn) of polyesters were measured by end group analysis and confirmed by vapour pressure osmometry (VPO). Solvent effect on the yield, Mn and Mw of the polymer was studied. The catalytic activity of different lipases are compared.  相似文献   

14.
Plasma membranes were isolated from HM7 melanoma cells grown in the presence of [3H]glucosamine and Na235SO4 or [3H]mannose and [14C]glucosamine. The labelled glucoconjugates were solubilized with 0.6 M lithium diiodosalicylate/0.5% Triton X-100. Fractionation of glycoconjugates by repeated chromatography on columns of Sepharose CL-6B and DEAE-Sepharose and by affinity chromatography on WGA-Sepharose yielded three radiochemically homogenous glycoproteins. One of these having an apparent molecular weight of 100 000 was found to contain clusters of (AcNeu)1 or in2 å [Gal å GalNAc] linked O-glycosidically to the protein. One other glycoprotein contained both O-glycosidically and N-glycosidically-linked oligosaccharides, and the third contained only N-glycosidically-linked carbohydrates. Preliminary results indicate that the 100 000 molecular weight mucin-type glycoprotein is present in significantly reduced quantities in cultured human fetal uveal melanocytes. Further, the bulk of the glycoproteins from the melanocytes were of lower molecular size compared to those from the melanoma cells.  相似文献   

15.
Sonicated calf thymus DNA was fractionated by rate zonal centrifugation into seven fractions with weight average molecular weights ranging from 0.28 to 1.3 × 106 daltons, as determined by sedimentation equilibrium and light scattering measurements (the latter are described in the accompanying paper). Electron microscopy and sedimentation equilibrium analysis revealed these fractions to be narrowly disperse with Mw/Mn ratios averaging about 1.06. Intrinsic viscosities and sedimentation rates were measured and found to vary linearly with molecular weight in double-logarithmic plots in fair agreement with previously published functions relating these parameters for low molecular weight DNA. The average value for β from the Mandelkern— Flory equation was 2.59 × l06, also agreeing with reported estimates of this parameter for short DNA. These data will be used in the second paper of this series to calculate the persistence length of the DNA fragments in each of the seven fractions by light scattering and hydrodynamic theories for the Kratky—Porod worm-like coil.  相似文献   

16.
A 0.5 × 106Mr RNA found in plastids of the aquatic angiosperm Spirodela, is synthesized at a much higher rate than any other rapidly labeling RNA species about 3–312 h after dark-grown plants are transferred to light. The pulse labeling kinetics of the 0.5 × 106Mr RNA after transfer to light, argue against its involvement in the biogenesis of plant rRNAs. Although poly(A) RNA is found in Spirodela, poly(A) sequences are not detected in the 0.5 × 106Mr RNA; yet a sucrose gradient fraction which includes RNA of this Mr stimulates amino acid incorporation by an E. coli cell free extract more than other RNA fractions. The possible involvement of the 0.5 × 106Mr RNA as a chloroplast messenger is discussed.  相似文献   

17.
The conformation and dilute solution properties of (2→1)-β-d-fructan in aqueous solution were studied by gel permeation chromatography, low-angle laser light-scattering photometry, viscometry, small-angle X-ray scattering and electron microscopy. Fractions covering a broad range of weight-average molecular weights (Mw) from 1.49 × 104 to 5.29 × 106 were obtained from a native sample by ultrasonic degradation and fractional precipitation. For Mw < 4 × 104, the intrinsic viscosity [η] varies with Mw0.71, indicating that the fructan chain behaves as a random coil expanded by an excluded-volume effect in this molecular weight region. For Mw > 105, [η] exhibits an unusually weak dependence on Mw and finally becomes almost independent of molecular weight. This behaviour is interpreted in terms of a globular conformation of the high-molecular-weight fructan molecules. Small-angle X-ray-scattering measurements and electron microscopic observations support this interpretation of the values of [η] observed.  相似文献   

18.
Quasi-elastic light scattering measurements have been carried out for (i) human and bovine fibrinogens under identical conditions, (ii) for a large number of fractionated and unfractionated fibrin intermediates at various pH (10.0 to 10.5), (iii) for three intermediates polymerized at pH 7.4 and stabilized at pH 10.5 and (iv) for a gelled clot. Human and bovine fibrinogen proved to have noticeably different diffusion coefficients (same Mw) indicating a longer rod on the average for the human than for the bovine fibrinogen. This finding is in agreement with measurements of the integrated light scattering from these fibrinogens where a mass per unit length MwLw of 3860 and 5460 g mol?1 nm?1 were found, respectively. No angular dependence of the apparent diffusion coefficient Dapp = Γ/q2 was found for the monomers and the fibrin clot; all other samples from (ii) showed an angular dependence if Mw ? 1.76 × 106, were Γ is the first cumulant of the time correlation function and q = (4π/λ) sin?/2. A plot of Dapp/D versus q2〈S2〉 gave curves which, for the low molecular weight samples, correspond to ellipsoids. For the longer fibrils a dynamic behaviour in between that of a long rigid rod and random coil was found and indicates a certain flexibility of the fibrils. The diffusion coefficients from (ii) decay with increasing molecular weight and can be described by Perrin's theory for ellipsoids when M2 < 2 × 106 while a beter agreement with Kirkwood's theory of long rods is obtained for the longer fibrils. The hydrodynamic behaviour of (iii) indicates short and unbranched rods of considerable thickness.  相似文献   

19.
A water soluble acidic heteropolysaccharide named WAF was isolated from Auricularia auricula‐judae by extracting with 0.9% NaCl solution. By using gas chromatography, gas chromatography‐mass spectrometry, and NMR, its chemical structure was determined to be composed of a backbone of α‐(1→3)‐linked D ‐mannopyranose residues with pendant side groups of β‐D ‐xylose, β‐D ‐glucose, or β‐D ‐glucuronic acid at position O6 or O2. Six fractions prepared from WAF with a weight‐average molecular mass (Mw) between 5.9 × 104 and 64.7 × 104 g/mol were characterized with laser light scattering and viscometry in 0.1M NaCl at 25°C. The dependence of intrinsic viscosity ([η]) and radius of gyration (Rg) on Mw for this polysaccharide were found to be [η] = 1.79 × 10?3Mw0.96 cm3 g?1 and Rg = 6.99 × 10?2 Mw0.54 nm. The molar mass per unit contour length (ML) and the persistence length (Lp) were estimated to be 1124 nm?1 and 11 nm, respectively. The WAF exhibited a semirigid character typical of linear polysaccharides. Molecular modeling was then used to predict the ordered and disordered states of WAF; the simulated ML and Lp were however much smaller than the experimental values. Taken altogether, the results suggested that WAF formed a duplex in solution. © 2010 Wiley Periodicals, Inc. Biopolymers 95: 217–227, 2011.  相似文献   

20.
A water‐soluble α‐(1→4)‐D ‐glucan heteropolysaccharide with 37% degree of branch extracted by base from Rhizoma Panacis Japonici, coded as RPS3, was fractionated into six fractions by the method of nonsolvent addition. Their weight‐average molecular mass (Mw), polydispersity index (Mw/Mn), and radius of gyration (〈s2z1/2) were determined with laser light scattering (LLS) and size exclusion chromatography combined with LLS. The structure of the fraction was determined by methylation analyses and 13C NMR. The dependences of intrinsic viscosity ([η]) and 〈s2z1/2 on Mw were established as [η] = 0.71 Mw0.27 ± 0.01 (cm3/g) and 〈s2z1/2 = 1.53 Mw0.27 ± 0.02 (nm) in the Mw range from 5.62 × 104 to 3.05 × 106 (g/mol) for RPS3 in 0.15M NaCl aqueous solution at 25°C. On the basis of the current theory of the polymer solution, the fractal dimension (df), unperturbed chain dimension (A), and characteristic ratio (C) were calculated to be 3.0, 1.48 Å, and 15.1, respectively. The results revealed that the RPS3 chains existed as spherical conformation in the aqueous solution. Transmission electron microscope further provided the evidence of the sphere shape of the RPS3 and its fractionated molecules in water. In vitro cytotoxicity assay indicated that the fractions could inhibit the tumor cells and showed no harm to normal cells at low dose. The bioactivity was relative with molecular mass of the samples. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 383–390, 2010. This article was originally published online as an acceptedpreprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office atbiopolymers@wiley.com  相似文献   

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