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1.
During the course of investigation of haloalkalophilic bacteria, we screened some heavily polluted soil samples from the mudflats surrounding the city of Inchon, Korea, for their bioflocculant producing ability. Based on the screening, one isolate no. 450 tentatively identified as Bacillus sp. produced an extracellular polysaccharide having flocculation activity. The isolate produced the polysaccharide during the late logarithmic growth phase. The polymer could be recovered from the supernatant of the fermented medium by cold ethanol precipitation and purified by treating with cetylpyridinium chloride (CPC). The polymer was identified as an acidic polysaccharide containing neutral sugars, namely, galactose, fructose, glucose and raffinose, and uronic acids as major and minor components, respectively. The amount of neutral sugars, uronic acid and amino sugars were 52.4, 17.2 and 2.4%, respectively. The molecular weight of the polysaccharide was found to be 2.2×106 Da. The Fourier transform infrared spectrophotometer (FT-IR) revealed typical characteristics of polysaccharides. 1H NMR spectrum showed that the polymer is a heteroglycan. Thermogravimetric (TGA) analysis indicated the degradation temperature (Td) at 290 °C. The rheological analysis of the polymer 450 revealed the pseudoplastic property with shear-thinning effect, while the compression test indicated that the polymer had high gel strength, and the S.E.M. studies showed that the polymer has a porous structure with small pore-size distribution indicating the compactness of the polymer.  相似文献   

2.
To clarify the radical-scavenging activity of butylated hydroxytoluene (BHT), a food additive, stoichiometric factors (n) and inhibition rate constants (kinh) were determined for 2,6-di-tert-butyl-4-methylphenol (BHT) and its metabolites 2,6-di-tert-butyl-p-benzoquinone (BHT-Q), 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHA-CHO) and 3,5-di-tert-butyl-4-hydroperoxy-4-methyl-2,5-cyclohexadiene-1-one (BHT-OOH). Values of n and kinh were determined from differential scanning calorimetry (DSC) monitoring of the polymerization of methyl methacrylate (MMA) initiated by 2,2′-azobis(isobutyronitrile) (AIBN) or benzoyl peroxide (BPO) at 70 °C in the presence or absence of antioxidants (BHT-related compounds). The n values declined in the order BHT (1–2) > BHT-CHO, BHT-OOH (0.1–0.3) > BHT-Q (0). The n value for BHT with AIBN was approximately 1.0, suggesting dimerization of BHT. The kinh values declined in the order BHT-Q ((3.5–4.6)×104 M−1 s−1) > BHT-OOH (0.7–1.9×104 M−1 s−1) > BHT-CHO ((0.4–1.7)×104 M−1 s−1) > BHT ((0.1–0.2)×104 M−1 s−1). The kinh for metabolites was greater than that for the parent BHT. Growing MMA radicals initiated by BPO were suppressed much more efficiently by BHT or BHT-Q compared with those initiated by AIBN. BHT was effective as a chain-breaking antioxidant.  相似文献   

3.
A method for determination of carboxymethyl cellulose (CMC) molecular weight (MW) and chemical heterogeneity (degree of oxidation (DO)) using a bi-detector HPSEC (UV-detector online with refractometer) has been developed. It has been found that the use of 0.5 N NaOH or 0.4 M acetate buffer as the eluent ensures CMC separation according to MW. It has been revealed that the universal calibration for the polyelectrolyte CMC and the neutral polymer dextran is valid under the conditions applied. The Mark–Houwink equations for CMC in 0.5 N NaOH and 0.4 M acetate buffer have been estimated to be [η]=5.37×10−4 MW0.73 and [η] =2.24×10−4 MW0.83 dl g−1, respectively. The equation log K=1.64−4.00 ml g−1 for CMC has been estimated. An approach for determining DO from adsorption at 290 or 313 nm has been developed.  相似文献   

4.
The hydrodynamic characteristics of the polysaccharide pullulan (polymaltotriose) in water have been investigated and its molecular characteristics have been determined. Experimental values varied over the following ranges: velocity sedimentation coefficient (S): 0.9 < S < 11.2, translational diffusion coefficient (107 cm2 s−1): 1.1 < D < 14.7 and intrinsic viscosity (cm3 g−1): 6.7 < [η] < 164, which corresponds to a change in molecular weight (× 103) in the range 3.9 < MSD < 644. On the basis of analysis of the literature and our experimental data, excluded volume effects have been shown to have a prevailing influence on the chain length of these polysaccharides. The equilibrium rigidity and hydrodynamic chain diameter of pullulan were evaluated on the basis of the theory of hydrodynamic properties of a wormlike necklace, taking into account excluded volume effects. At low M (< 30 × 103) the translation friction data (in contrast to viscometric data) cannot be described in the framework of the theory of linear molecules.  相似文献   

5.
It is well accepted that estradiol (E2) plays an important role in the genesis and evolution of breast cancer. Quantitative evaluation indicates that in human breast tumor, estrone sulfate (E1S) ‘via sulfatase’ is a much more likely precursor for E2 than is androstenedione ‘via aromatase’. In previous studies, it was demonstrated that in isolated MCF-7 and T-47D breast cancer cell lines, estradiol can block estrone sulfatase activity. In the present study, the effect of E2 was explored using total normal and cancerous breast tissues. This study was carried out with post-menopausal patients with breast cancer. None of the patients had a history of endocrine, metabolic or hepatic diseases or had received treatment in the previous 2 months. Each patient received local anaesthetic (lidocaine 1%) and two regions of the mammary tissue were selected: (A) the tumoral tissue and (B) the distant zone (glandular tissue) which was considered as normal. Samples were placed in liquid nitrogen and stored at –80 °C until enzyme activity analysis. Breast cancer histotypes were ductal and post-menopausal stages were T2. Homogenates of tumoral or normal breast tissues (45–75 mg) were incubated in 20 mM Tris–HCl, pH 7.2 with physiological concentrations of [3H]-E1S (5 × 10−9 M) alone or in the presence of E2 (5 × 10−5 to 5 × 10−7 M) during 30 min or 3 h. E1S, E1 and E2 were characterized by thin layer chromatography and quantified using the corresponding standard. The sulfatase activity is significantly more intense with the breast cancer tissue than normal tissue, since the concentration of E1 was 3.20 ± 0.15 and 0.42 ± 0.07 pmol/mg protein, respectively after 30 min incubation. The values were 27.8 ± 1.8 and 3.5 ± 0.21 pmol/mg protein, respectively after 3 h incubation. Estradiol at the concentration of 5 × 10−7 M inhibits this conversion by 33% and 31% in cancerous and normal breast tissues, respectively and by 53% and 88% at the concentration of 5 × 10−5 M after 30 min incubation. The values were 24% and 18% for 5 × 10−7 M and 49% and 42% for 5 × 10−5 M, respectively after 3 h incubation. It was observed that [3H]-E1S is only converted to [3H]-E1 and not to [3H]-E2 in normal or cancerous breast tissues, which suggests a low or no 17β-hydroxysteroid dehydrogenase (17β-HSD) Type 1 reductive activity in these experimental conditions. In conclusion, estradiol is a strong anti-sulfatase agent in cancerous and normal breast tissues. This data can open attractive perspectives in clinical trials using this hormone.  相似文献   

6.
Low-molecular-weight chitosan were prepared using 85% phosphoric acid at different reaction temperatures and reaction time. At room temperature, the viscosity average-molecular weights (Mv) of chitosan decreased to 7.1×104 from 21.4×104 after 35 days treatment. The degradation rate decreased with increasing hydrolysis time. The yields of chitosan also continuously decreased from 68.4 to 40.2% after 35 days. At 40, 60 and 80 °C, the molecular weight decreased to 3.70×104, 3.50×104 and 2.00×104 on 8 h hydrolysis, respectively. The yields of chitosan remain at a high level compared with that at room temperature and were 86.5, 71.4 and 61.3% at 40, 60 and 80 °C treatment, respectively. The different reaction time gave chitosan with different molecular weights. At 60 °C, the molecular weight of products decreased to 7.40×104 from 21.4×104 within 4 h, then decreased slowly to 1.90×104 in 15 h. It was also found that the water-solubility of chitosan increased as the molecular weight decreased. Results show the changes in yields and molecular weight of chitooligomers were strongly dependent on the reaction temperature and reaction time.  相似文献   

7.
Synthesis of chitosan sulfates with low molecular weight (Mv 9000–35,000 Da) was carried out by sulfation of low molecular weight chitosan (Mv 10,000–50,000 Da). The oleum was used as sulfating agent and dimethylfornamide as medium. The chitosans were prepared by enzymatic and acidic hydrolysis of initial high molecular weight chitosan as well as by extrusion solid-state deacetylation of chitin. As was shown by FT-IR and NMR-methods and elemental analysis, the sulfation occurred at C-6 and C-3 positions and substitution degree is 1.10–1.63. The molecular weight sulfated chitosan was determined by viscometric method and the Mark–Houwink equation [η]=10−5 4.97 M0.77. Study of anticoagulant activity showed that chitosan sulfates with lowered molecular weight demonstrated a regular increase of anti-Xa activity like heparins.  相似文献   

8.
Human fibroblast culture on a crosslinked dermal porcine collagen matrix   总被引:1,自引:0,他引:1  
The use of a novel porcine-derived collagen biomaterial as a dermal tissue engineering matrix was examined. The matrix is derived from porcine dermis, and is processed to retain the native collagen (Type 1) and elastin structure. Human primary fibroblasts were cultured on the matrix to examine its potential for creating a dermal replacement. Attachment of fibroblasts on the collagen was compared to tissue culture plastic and PET membranes. Cell proliferation was assessed using the MTT assay and DAPI staining. For seeding densities of 5×104 and 1×105 cells cm−2, PET and plastic demonstrated >95% attachment of seeded numbers after 3 h. The collagen matrix reached levels >80% after 3–4 h with no influence of the seeding density. Matrix samples with perforating pores of 40 μm diameter were also studied. After 216 h culture in static culture, with media replacement every 3 days, the final cell numbers reached 2.1×105 (perforated) and 2.0×105 cells cm−2 (unperforated). In comparison fibroblast culture in a perfusion bioreactor, with continuous media replacement, reached 2.3×105 (unperforated) and 2.5×105 cells cm−2 (perforated) after 216 h.  相似文献   

9.
We report spectrophotometric equilibrium studies of both the self-association of the new antibiotic iremycin and of its binding to calf thymus DNA in solution (ionic strength 0.2 M; pH 6.0). Iremycin forms dimers in this solution with a dimerization constant K4=(1.19 ± 0.10) × 103 M−1. This equilibrium is taken into account in the evaluation of the interaction of iremycin with DNA. The binding behaviour can be completely described by a single binding mechanism of monomeric iremycin to DNA with allowance both for neighbour exclusion and for cooperativity of interaction. The three intrinsic binding parameters for the homogeneous model were determined simultaneously by a least squares fit of the original titration data: equilibrium constant of cooperative binding K = (2.72 ± 0.66) × 105 M−1 cooperativity parameter σ=0.38±3.27 ± 0.32. The binding parameters of iremycin and adriamycin and their microbial activities are compared.  相似文献   

10.
Static light scattering of high amylopectin waxy maize starch gently dispersed in 90% dimethyl sulfoxide–water yielded a weight average molecular weight Mw and radius of gyration Rg of 560×106 g/mol and 342 nm, respectively. To obtain an independent hydrodynamic characterization of these solutions, we measured the sedimentation coefficient for the main component in an analytical ultracentrifuge. The value of s0, the infinite dilution sedimentation coefficient, was 199 S. The translational diffusion coefficient D0 in very dilute solutions was measured by dynamic light scattering at 90° and found to be 2.33×10−9 cm2/s. An effective hydrodynamic radius Rh was calculated from this diffusion constant using the Stokes–Einstein equation and found to be 348 nm. The structure-related parameter ρ=Rg/Rh was calculated to be 0.98. The weight average molecular weight calculated from the Svedberg equation using the values measured for s0 and D0 was 593×106 g/mol. This result is in reasonable agreement with the light scattering results. As light scattering results are subject to experimental errors due to the possibility of dust contamination, the presence of microgel or aggregates, and the questionable applicability of light scattering theory to interpret results for macromolecular sizes approaching the wave length of light used as a source for scattering, it is advisable to have corroborating hydrodynamic data when possible to further validate light scattering results in this very high molecular weight range.  相似文献   

11.
Aqueous solutions of fractions of an extracellular linear mannan formed by Rhodotorula rubra yeast have been investigated by hydrodynamic methods (high-speed sedimentation, translation isothermic diffusion and viscometry). The molecular weight was determined according to Svedberg ( ) and the polydispersity parameters of the initial sample were also determined (Mw/Mn = 1·20 and Mz/Mw = 1·21). Relationships between the molecular weight (M) and so, Do and [η] in the range were: [η] = 2·33 × 10−2 M0.75, Do = 1·65 × 10−4 M0·58, so = 2·24 × 10−15 M0·43. The equilibrium rigidity and hydrodynamic diameter of chains representing mannan molecules were evaluated.  相似文献   

12.
Amylovoran, the acidic exopolysaccharide (EPS) of Erwinia amylovora, and stewartan, the capsular EPS of E. stewartii, were characterized by analytical ultracentrifugation and by size exclusion chromatography connected to dual detection of light scattering and mass. The average molecular weights of amylovoran and stewartan were determined as 1.0×106 and 1.7×106 Da, with polydispersity values (Mw/Mn) of 1.5 and 1.4, respectively. Based on the sugar composition and their molecular weight, both exopolysaccharides consist of approximately 1000 repeating units per molecule, this suggests a similar mechanism for chain length determination during biosynthesis of EPS in both organisms.  相似文献   

13.
Intermolecular self-association of hylan chains can be observed in hylan of molecular weight ca. 1×107, with an indication of specific cross-linking protein points and inter-chain cross-links of molecular weight of between 10,000 and 80,000. When this high molecular weight hylan is autoclaved to Mw 1.8×106, to yield a molecular size of the same order as a conventional hyaluronan, the structural features of hylan are retained, with regions of network disintegration having single chains to which one or two chains are joined. After degradation by OH radicals, extended linear chains are found with some of the straight chains having branch points. These can be attributed to the unwinding of the hylan coils by the movement of a droplet of water across the mica surface. The effect of filtration by 1 μm filter does not reduce the measured Mw (corresponding to an intrinsic viscosity of 8188 at low shear rate). However, when stressed through a 0.45 μm filter the Mw falls to a quarter of its previous value. The cross-linked structure of the original hylan is shown to be equivalent to a hyaluronan of ca. 10×106, based on rheological measurements. The cross-linked structure confers stability to degradation by OH radicals not observed for hyaluronan. This distinctive behaviour of hylan is maintained for the entire range of molecular weights studied. The results confirm the tendency of hylan chains to readily undergo chain–chain association.  相似文献   

14.
Crude water-soluble polysaccharides (ASP) were separated from Angelica sinensis (Oliv.) Diels by hot water extraction. They were fractionated into neutral and acidic polysaccharides by anion-exchange chromatography. The neutral polysaccharide (ASP1) was rich in glucose, galactose, and arabinose suggesting a mixture of glucan and arabinogalactan. The acidic polysaccharide (ASP2, ASP3) consisted mainly of galacturonic acid along with rhamnose, arabinose, and galactose indicating a pectic polysaccharide. The degree of esterification of ASP and ASP3 were 54.06% and 47.14% for the crude and purified sample, respectively. ASP3, with a molecular weight of 3.4 × 104 Da determined by high-performance size-exclusion chromatography (HPSEC), was the major constituent for the crude extracts. The radioprotective effect of the pectic polysaccharide ASP3 was studied in murine models. ASP3 pretreated mice exhibited a significant decrease of apoptosis (P < 0.05, dosage of 200 mg/kg d body weight) in peripheral lymphocytes compared to the irradiated control. The results showed that ASP3 can protect leucocytes and lymphocytes of mice against radiation induced damage, which has potential radioprotective effect on acute radiation injured mice.  相似文献   

15.
The interaction of a structurally characterized Sr–Fe nitrosyl complex with DNA has been studied by UV–vis and fluorescence spectroscopy, viscometric, and gel electrophoresis techniques. From the absorption titration studies the intrinsic binding constant of the complex with DNA was calculated to be 1.6 × 104 M−1. Fluorimetric studies indicate that the complex compete with EB in binding to DNA. The complex shows nuclease activity on pUC19 supercoiled DNA in presence of H2O2.  相似文献   

16.
Rhizopus nigricans (R. nigricans) transforms fungitoxic progesterone into the less toxic 11-hydroxyprogesterone which is then able to exit the mycelia into the surrounding water. Hydroxylation of progesterone is an inducible process in which cytosolic progesterone receptors could be involved. In the present study, we characterised receptors with respect to ligand specificity and to their involvement in progesterone induction of hydroxylase. EC50 values of different ligands (steroids, xenobiotic arylhydrocarbons and natural flavonoids) were determined by competition studies using 40 nM (3H)progesterone. C21 and C19 3-oxo-4-ene steroids were good competitors (EC50 of progesterone 2.3 ± 0.1 × 10−7 M, EC50 of androsten-3,17-dione 24 ± 2 × 10−7 M). The presence of hydroxyl groups in steroids significantly decreased the affinity for receptors. The arylhydrocarbons -naphthoflavone and ketoconazole exhibited EC50 values of 0.3 ± 0.01 × 10−7 M and 27 ± 5 × 10−7 M, respectively, whereas β-naphthoflavone and benzo(a)pyrene were not able to displace labelled progesterone completely. The competition curves obtained by natural flavonoids also did not reach the bottom level of non-labelled progesterone, indicating the interaction at some allosteric binding site(s) of progesterone receptors. All ligands were examined for their involvement in progesterone-hydroxylase induction. Steroid agonists induced the enzyme in a dose-dependent manner in accordance with their affinity for receptors, whereas arylhydrocarbons and natural flavonoids did not induce the enzyme. The agonistic action of steroids, together with the antagonistic action of -naphthoflavone, strongly suggests the involvement of progesterone receptors in progesterone signalling resulting in the induction of progesterone-hydroxylase.  相似文献   

17.
The oxidation of TEMPO (2,2,6,6-tetramethyl-piperidine-1-oxyl radical) has been studied in the presence of recombinant laccases (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) from Polyporus pinsitus (rPpL), Myceliophthora thermophila (rMtL), Coprinus cinereus (rCcL) and Rhizoctonia solani (rRsL) in buffer solution pH 4.5–7.3 and at 25 °C. At pH 5.5 the oxidation constant calculated from the initial rate of TEMPO oxidation was 1.7 × 104, 1.4 × 103, 7.8 × 102 and 5.2 × 102 M−1 s−1 for rPpL, rRsL, rCcL and rMtL, respectively. The maximal activity of rPpL-catalysed TEMPO oxidation was at pH 5.0. The pKa obtained in neutral pH range was 6.2. The reactivity of laccases is in a good agreement with laccases copper type I redox potential.

TEMPO oxidation rate increased 541 times in the presence of 10-(3-propylsulfonate) phenoxazine (PSPX). The model of synergistic TEMPO and PSPX oxidation was proposed. Experimentally obtained rate constants for rPpL-catalysed PSPX oxidation were in a good agreement with those calculated from the synergistic model, therefore confirming the feasibility of the model. The acceleration of TEMPO oxidation with high reactive laccase substrates opens new possibilities for TEMPO application as a mediator.  相似文献   


18.
Crystal structures of Co2(CO)6(dppm) (1) and Co2(CO)5(CHCO2Et)(dppm) (2) (dppm = Ph2PCH2PPh2) show asymmetry with respect to the orientation of the phenyl groups in 1 and owing to the bridging ethoxycarbonylcarbene ligand in 2. The effect of this asymmetry was recognized in the solid-state 31P NMR spectra of 1 and 2 and in the solid-state and solution 13C NMR spectra of 2 as well, but not in the solid-state and solution 13C NMR spectra of 1. In CH2Cl2 solution under an atmosphere of 13CO, the CO ligands of both complexes exchange with 13CO. The overall rate of 13CO exchange at 10 °C was found to be kobs = 0.107 × 10−3 s−1 for 1 and kobs = 0.243 × 10−3 s−1 for 2. Two-layered ONIOM(B3LYP/6-31G(d):LSDA/LANL2MB) studies revealed fluxional behavior of 1 with rather small barriers of activation of the rearrangements. Four possible isomers have been computed for 2, close to each other energetically.  相似文献   

19.
Shear flow, dynamic oscillation and extensional viscosity measurements were used to compare the rheological performance of several hylan samples (Mv 1.6, 3.2, 3.7, 4.7 and 5.6×106) and hyaluronan (Mv 1.4 and 1.8×106) before and after hydroxyl radicals (√OH) induced degradation. It was found that the higher molecular weight cross-linked structure of hylan was more resistant to degradation than hyaluronan and that this superior stability was reflected in various rheological parameters. The √OH degradation of the initial hylan and hyaluronan samples produced a range of polysaccharides based on hylan and hyaluronan with molecular weight covering a range from 0.5–5.6×106. The rheological parameters associated with the polysaccharides could then also be studied. Zero shear values of the complex viscosity (η*), dynamic viscosity (η′) and shear viscosity (η) were calculated using the method of Morris1 and shown to approach the same value at zero shear or frequency. An adaptation of the method of Gibbs et al.2 gave a ‘master curve’ for the storage and loss modulus of hyaluronan and hylan, which encompasses a 10-fold molecular weight and a 5-fold concentration variation. In all instances for hylan, the storage modulus predominates over the loss modulus, whereas for hyaluronan, the reverse is true, demonstrating the greater elasticity of hylan throughout the whole experimental range of molecular weights and concentrations.  相似文献   

20.
Studies on the molecular chain morphology of konjac glucomannan   总被引:2,自引:0,他引:2  
The chain geometry and parameters of konjac glucomannan were studied by using laser light scatter (LLS), gel permeation chromatography (GPC) and viscosimetry. The weight-average molecular weight (Mw), root-mean-square ratio of gyration (S21/2), second viral coefficient (A2) and polydispersity index (Mw/Mn) were 1.036×106, 105±0.9 nm, (−1.587±0.283)×10−3  mol ml g−2 and 1.015±0.003 respectively. Mark-Houwink equation was established as , and the molecular chain parameters were as follows: ML=982.82 nm−1, q=27.93 nm, d=0.74 nm, h=0.26 nm, L=1054.11 nm. To confirm the above results, konjac glucomannan was observed by using atomic force microscopy (AFM) and transmission electron microscope (TEM). The physical image showed directly that the konjac glucomannan molecule was an extending semi-flexible linear chain without branches, and than the molecular dimension also conformed to the parameters above. Therefore the image of molecular chain geometry confirmed the deduction drawn by Mark-Houwink equation and molecular chain parameters magnificently.  相似文献   

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