Molecular mass and chain conformation of carboxymethylated derivatives of beta-glucan from sclerotia of Pleurotus tuber-regium

Seven water-insoluble (1 --> 3)-beta-D-glucan fractions TM8-1 to TM8-7 with weight-average molecular mass M(w) ranged from 2.22 to 77.4 x 10(4) obtained from the sclerotia of Pleurotus tuber-regium were carboxymethylated to produce the water-soluble fractions CTM8-1 to CTM8-7 with M(w) ranged from 3.87 to 87.8 x 10(4). The degree of substitution (DS) of CTM8 fractions was analyzed by ir and elemental analysis (EA) to be 0.3-0.68. The M(w) and the intrinsic viscosity [eta] of the CTM8 fractions were measured by size-exclusion chromatography combined with multiangle laser light scattering (SEC-MALLS), MALLS, and viscometry in phosphate buffer solution (PBS) at 37 degrees C. The dependencies of [eta] and radius of gyration (z) (1/2) on M(w) for the CTM8 samples were found to be [eta] = (8.82 +/- 0.03) x 10(-3) M(w)(0.78 +/- 0.04) (cm(3) g(-1)) and (z) (1/2) = (3.09 +/- 0.05) x 10(-3) M(w)(0.75 +/- 0.06) (nm) in the M(w) range from 3.87 x 10(4) to 53.2 x 10(4). Based on current theories for wormlike chain model, the conformational parameters of the CTM8 were obtained to be 790 (nm(-1)) for M(L), 9.6 (nm) for q, which were higher than those of the native TM8 fractions, suggesting a more extended flexible chain of CTM8 in PBS. On the whole, the CTM8 fractions showed higher antitumor activity than their corresponding TM8 fractions. In view of data from molecular parameters and bioactivity, the antitumor activity of the CTM8 fractions may be correlated to its water solubility and relatively extended chain.     

Solution properties of an alpha-(1-->3)-D-glucan from Lentinus edodes and its sulfated derivatives

A water-insoluble alpha-(1-->3)-D-glucan (A) from Lentinus edodes was fractionated into 13 fractions in dimethyl sulfoxide containing 0.25 M lithium chloride (0.25 M LiCl-Me(2)SO). Five fractions were treated with sulfur trioxide-pyridine complex at 25 degrees C to synthesize water-soluble sulfated derivatives (S-A). The weight-average molecular weights, M(w), and intrinsic viscosities [eta], of the samples A and S-A were determined by multi-angler laser light scattering (MALLS), and viscosity. The M(w) dependence of [eta] and of the radius of gyration (z)(1/2), was found to be represented approximately by [eta]=4.9 x 10(-2) M(w)(0.67) (cm(3) g(-1)), and (z)(1/2)=4.8 x 10(-2) M(w)(0.54) (nm) for the alpha-glucan in 0.25 M LiCl-Me(2)SO in the M(w) range from 7.24 x 10(4) to 4.21 x 10(5), and by [eta]=6.8 x 10(-4) M(w) 1.06 (cm(3) g(-1)), and (z)(1/2)=9.4 x 10(-4) M(w)(0.92) (nm) for the sulfated alpha-glucan in aqueous 0.5 M NaCl in the M(w) range from 5.92 x 10(4) to 1.42 x 10(5) at 25 degrees C. The results indicate that the alpha-(1-->3)-D-glucan exists as a flexible chain in 0.25 M LiCl-Me(2)SO, and its sulfated derivative in 0.5 M NaCl aqueous has stiffer chains than the original. (13)C NMR indicated that intramolecular hydrogen bonding occurred in the sulfated alpha-glucan, causing the observed chain stiffness.     

Effects of excluded volume and polydispersity on solution properties of lentinan in 0.1 M NaOH solution

Seven lentinan fractions of various weight-average molecular weights (M(w)), ranging from 1.45 x 10(5) to 1.13 x 10(6) g mol(-1) were investigated by static light scattering and viscometry in 0.1M NaOH solution at 25 degrees C. The intrinsic viscosity [eta] - M(w) and radius of gyration s(2)(z) (1/2) - M(w) relationships for lentinan in 0.1M NaOH solution were found to be represented by [eta] = 5.1 x 10(-3)M(w) (0.81) cm(3) g(-1) and s(2)(z) (1/2) = 2.3 x 10(-1)M(w) (0.58) nm, respectively. Focusing on the effects of the M(w) polydispersity with the Schulz-Zimm distribution function, the data of M(w), s(2)(z) (1/2), and [eta] was analyzed on the basis of the Yoshizaki-Nitta-Yamakawa theory for the unperturbed helical wormlike chain combined with the quasi-two-parameter (QTP) theory for excluded-volume effects. The persistence length, molecular weight per unit contour length, and the excluded-volume strength were determined roughly to be 6.2 nm, 980 nm(-1), and 0.1, respectively. Compared with the theoretical value calculated by the Monte Carlo model, the persistence length is longer than that of the single (1 --> 3)-beta-(D)-glucan chain. The results revealed that lentinan exists as single-stranded flexible chains in 0.1M NaOH solution with a certain degree of expansion due to the electrostatic repulsion from the interaction between the OH(-) anions and lentinan molecules.     

Chain stiffness of heteropolysaccharide from Aeromonas gum in dilute solution by dynamic light scattering

Dynamic light scattering measurements have been made on 15 fractions of aeromonas (A) gum, an extracellular heteropolysaccharide produced by the strain Aeromonas nichidenii, with dimethylsulfoxide containing 0.2M lithium chloride as the solvent at 25 degrees C. Data for the translational diffusion coefficient D covering a molecular weight range from 4.5 x 10(5) to 2.1 x 10(6) and ratios of the z-average radius of gyration (z) (1/2) to the hydrodynamic radius R(H) (calculated with previous (z) data) suggest that the polymer behaves like a semiflexible chain in this solvent similar to the stiffness of cellulose derivatives. Thus the D data are analyzed on the basis of the Yamakawa-Fujii theory for the translational friction coefficient of a wormlike cylinder by coarse-graining the heteropolysaccharide molecule. Excluded-volume effects are taken into account in the quasi-two-parameter scheme, as was done previously for (z) and [eta] (the intrinsic viscosity) of A gum in the same solvent. The molecular weight dependence of R(H) is found to be explained by the perturbed wormlike chain with a persistence length of 10 nm, a linear mass density of 1350 nm(-1), an excluded-volume strength parameter of 1.3 nm, and a chain diameter of 2.8 nm. These parameters are in substantial agreement with those estimated previously from (z) and [eta] data, demonstrating that the solution properties (D, (z), and [eta]) of the heteropolysaccharide are almost quantitatively described by the current theories for wormlike chains in the molecular weight range studied.     

Solution properties of (1-->3)-alpha-D-glucan and its sulfated derivative from Poria cocos mycelia via fermentation tank

From Poria cocos mycelia yielded via a pilot scale facility-fermentation tank, a water-insoluble (1-->3)-alpha-D-glucan coded as Pi-PCM3-I was isolated by extraction with 0.5 M NaOH/0.01 M NaBH(4) aqueous solution. Nine fractions from F1 to F9 with a weight-average molecular mass (M(w)) range from 7.75 x 10(4) to 57.3 x 10(4) were prepared from the Pi-PCM3-I sample by a nonsolvent addition method. The fractions were reacted with chlorosulfonic acid-pyridine complex to product water-soluble sulfated derivatives coded as S1 to S8 with M(w) from 2.36 x 10(4) to 14.5 x 10(4) and degree of substitution (DS) of 0.86-1.38. M(w), z-average radius of gyration (s(2) (z) (1/2)), the second virial coefficient (A(2)), and the intrinsic viscosity ([eta]) of the native and sulfated Pi-PCM3-I were measured by laser light scattering (LLS), size-exclusion chromatography combined with LLS (SEC-LLS), and viscometry at 25 degrees C. The Mark-Houwink equations for Pi-PCM3-I in 0.25 M LiCl/dimethylsulfoxide (DMSO) (Me(2)SO) and for its sulfated derivative in 0.15 M NaCl aqueous solution at 25 degrees C were established to be [eta] = 1.33 x 10(-2) M(w) (0.75+/-0.01) (mL g(-1)) and [eta] = 1.46 x 10(-4) M(w) (1.13+/-0.01) (mL g(-1)), respectively. On the basis of theories for a wormlike cylinder model, the conformational parameters of the native and sulfated Pi-PCM3-I were calculated to be 760 +/- 50 and 1060 +/- 30 nm(-1) for the molar mass per unit contour length (M(L)), 6.3 +/- 0.5 and 13.1 +/- 1 nm for the persistence length (q), and 14.9 +/- 0.2 and 31.8 +/- 1 for the characteristic ratio (C( proportional, variant)), respectively. The results revealed that Pi-PCM3-I existed as an extended flexible chain in 0.25 M LiCl/Me(2)SO, and its sulfated derivative existed as a semistiff chain in 0.15 M NaCl aqueous solution. Furthermore, Pi-PCM3-I possessed similar structure and molecular parameters to wc-PCM3-I from a rotary shaker; this suggests promising industrialization of Poria cocos polysaccharides.     

Chemical structure and chain conformation of the water-insoluble glucan isolated from Pleurotus tuber-regium

A water-insoluble polysaccharide (TM8) was isolated from sclerotium of Pleurotus tuber-regium by extraction with 0.5M NaOH aqueous solutions at 120 degrees C. Its chemical structure was confirmed by infrared, high performance liquid chromatography, gas chromatography, and (13)C NMR in dimethylsulfoxide (DMSO) to be composed of beta-(1 --> 3)-D-glucan backbone chain linked with a branched glucose, one out of every three glycosyl units being substituted at C6 position. The glucan TM8 in DMSO was fractionated by nonsolvent addition method into ten fractions, and the solution properties were studied by size exclusion chromatography combined with multiangle laser light scattering (SEC-MALLS) and viscometry in DMSO at 30 degrees C. The dependencies of intrinsic viscosity [eta] and radius of gyration [(s(2)(1/2)(z-2)] on weight-average molecular mass M(w) for this glucan were found to be [eta] = (9.24 +/- 0.2) x 10(-2)M(w)(0.51 +/- 0.02) (cm(3)g(-1)) and [(s(2)(1/2)(z-2)] = (3.67 +/- 0.3) x 10(-2)M(w)(0.56 +/- 0.02) (nm) in the range of M(w) from 1.07 x 10(4) to 77.4 x 10(4). Based on current theories for a wormlike chain, the conformational parameters of the glucan TM8 were found to be 408 (nm(-1)) for M(L), 3.1 (nm) for q, and 16.8 for C(infinity), suggesting that the polysaccharide exists as a dense random-coil chain in DMSO, due to branched structure.     

Chain conformation of water-insoluble hyperbranched polysaccharide from fungus

Water-insoluble polysaccharide (TM3a), extracted from sclerotia of Pleurotus tuber-regium, was identified as a hyperbranched beta-d-glucan from the results of one- and two-dimensional NMR and GC-MS analysis. The degree of branching of TM3a is 65.5%. TM3a was fractionated by using a non-solvent addition method into 14 fractions, and its solution properties in 0.25 M LiCl/dimethylsulfoxide (DMSO) solution were studied systematically by using static laser light scattering, dynamic light scattering, and viscometry at 25 degrees C. The dependences among the values of intrinsic viscosity ([eta]), radius of gyration (z 1/2), and hydradynamic radius (Rh) on weight-average molecular weight (Mw) were found as the following: [eta] = 0.46Mw0.30+/-0.01, z 1/2 = 4.79 x 10-2Mw0.43+/-0.04, and Rh = 5.01 x 10-2Mw0.41+/-0.02 in the Mw range from 1.94 x 105 to 2.06 x 107 for TM3a in a 0.25 M LiCl/DMSO solution at 25 degrees C. The current theory of polymer solution was applied to explain the relationship among the fractal dimension, ratio of geometric to hydrodynamic radius (rho = z 1/2/Rh), and MwA2/[eta] of TM3a. The results indicated that TM3a existed as a compact chain conformation with a sphere-like structure in LiCl/DMSO solution. Furthermore, by using transmission electron microscopy, we observed directly the spherical molecules with an average diameter of 23.0 +/- 1.8 nm.     

Chain conformation of sulfated derivatives of beta-glucan from sclerotia of Pleurotus tuber-regium

Six water-insoluble (1-->3)-beta-D-glucan fractions TM8-1 to TM8-6 with weight-average molecular mass Mw ranging from 5.76 to 77.4x10(4) obtained from the sclerotia of Pleurotus tuber-regium were sulfated to produce the water-soluble fractions S-TM8-1 to S-TM8-6 with Mw from 6.0 to 64.8x10(4). The degree of substitution (DS) of S-TM8 fractions was analyzed by elemental analysis (EA) to be 1.14-1.74. The 13C NMR results indicated that the C-6 was fully substituted, and C-2, C-4 were partially substituted by the sulfo-groups. The Mw and the intrinsic viscosity [eta] of the S-TM8 fractions were measured, respectively, by size-exclusion chromatography combined with laser light scattering (SEC-LLS), LLS and viscometry in phosphate buffer solution (PBS) at 37 degrees C. The dependences of [eta] and radius of gyration z(1/2) on Mw for the S-TM8 samples were found to be [eta]=1.89x10(-2) Mw(0.70) (cm3/g) and z(1/2)=1.12x10(-4) Mw(0.81) (nm) in the Mw range tested. Based on current theories for a wormlike chain model, the molar mass per unit contour length ML and persistence length q of the S-TM8 were calculated to be 990 nm(-1) and 8.5 nm, respectively. The relatively higher q value suggested a more expanded flexible chain of S-TM8 in PBS. The water-solubility and relatively expanded chain conformation of the STM8 fractions were considered to be significant to their antiviral activity.     

Pressure cell assisted solution characterization of polysaccharides. 2. Locust bean gum and tara gum

Following the work carried out on guar gum in our first paper of a series, the "pressure cell" solubilization method was applied to two other less highly substituted galactomannans: locust bean gum (LBG) and tara gum. True molecular solution of the polymers was achieved using appropriate temperature, time, and pressure regimes. The technique of capillary viscometry was used to determine the intrinsic viscosity [eta] of the "pressure cell" treated and untreated samples. Molecular weight (M(w)) and radius of gyration (R(g)) were determined by light scattering. The data obtained for LBG and tara gum were compared statistically with reliable data found for guar gum in the literature. The variation in [eta] with M(w) followed the Mark-Houwink-Sakurada relationship, giving the exponent alpha = 0.74 +/- 0.01 for galactomannans consistent with random coil behavior. The characteristic ratio, C(infinity), and the chain persistence length, L(p), were both calculated for LBG and tara gum using the Burchard-Stockmayer-Fixman (BSF) method which is appropriate for flexible to semiflexible chains. A general value of 9 < C(infinity) < 16 and 3 < L(p) < 5 nm can now be estimated with statistical confidence for all galactomannans. According to our statistical analysis, the chain persistence length was found to be insensitive to the degree of galactose substitution.     

Thermally induced coil-to-helix transition of sodium gellan gum with different molar masses in aqueous salt solutions

Using 5 samples of well-purified Na-gellans (Na-gellans G1-G5, weight-average molar mass M(w) = 120 x 10(3)-32 x 10(3) at 40 degrees C), the effects of molar mass on the coil-to-double-helix transition in aqueous solutions with 25 mM NaCl were studied by light scattering and circular dichroism (CD) measurements, viscometry, and differential scanning calorimetry (DSC). From the temperature dependence of M(w), molar ellipticity at 201 nm [theta]201, intrinsic viscosity [eta], and DSC exothermic curves, it was found that the coil-to-double-helix transitions for G1-G5 samples took place at almost the same temperature. The [eta] and M(w) obtained in the temperature range from 40 to 25 degrees C can be explained by a simple coil/double-helix equilibrium model using the double-helix contents determined from CD data. The van't Hoff's transition enthalpy deltaH(vH) of Na-gellans depended on M(w). It is concluded that the coil-to-double-helix transitions of Na-gellans are all-or-none type transitions, and are accelerated with increasing M(w).     

Comparative rheological behavior of hyaluronan from bacterial and animal sources with cross-linked hyaluronan (hylan) in aqueous solution

Using a variety of rheological techniques, the behavior of hyaluronan (M(w) 0.8-2.2 x 10(6)), cross-linked hyaluronan (hylan) (M(w) 1.8-12.5 x 10(6)), and Healon (M(w) approximately 5 x 10(6)) (a proprietary hyaluronan) was studied over a large range of molecular weights. The object was to study the effect of the cross-links in hylan on the various rheological parameters, in comparison with linear hyaluronan. There are significant differences. The Huggins constant and the critical overlap parameter C*[eta] are considerably lower for hylan and an increase in moduli at low frequencies was observed for hylan compared with the hyaluronan samples at all molecular weights studied. The results point to a difference in structure in dilute solution for hylan due to the ability to form networks, which can be removed by pressure filtration. In contrast, we do not find an increase of the steady shear viscosity and elastic modulus at higher concentrations when a homogeneous entangled network is reached. We attribute this behavior to the semirigid character of the hyaluronan chain and to the predominance of entanglements over the cross-link points present in hylan in the semidilute domain. Due to the higher apparent molecular weights that are possible with hylan structures but not with the hyaluronans currently available, a wider range of applications can be achieved with hylans when viscoelasticity is required, particularly for the viscosupplementation of synovial fluid damaged by osteoarthritis.     

Characterization of pectin, flash-extracted from orange albedo by microwave heating, under pressure

Pectin was acid extracted from orange albedo by microwave heating under pressure. Extraction times ranged from 2.5 to 8 min. Solubilized pectin was characterized for molar mass (M), rms radius of gyration (Rg) and intrinsic viscosity [eta] by HPSEC with online light scattering and viscosity detection. M, Rg and [eta] all decreased with increasing extraction time. Nevertheless, at heating times of 2.5 and 3.0 min, M, Rg and [eta] were significantly higher than a commercial citrus pectin when the albedo:solvent ratio was 1:25 (w/v). At the heating time of 2.5 min Mw was 3.6 x 10(5), Rgz was 38 nm and [eta]w was 10.8 dL/g. Chromatography revealed that solubilized pectin distributions were bimodal in nature and that the low-molar-mass fraction increased at the expense of the high-molar-mass fraction with increasing extraction time. Scaling law exponents revealed that the high-molar-mass fraction was extremely compact in shape, whereas the low-molar-mass fraction was more asymmetric in shape. Possibly these results indicated that at short extraction times, pectin was solubilized as compact aggregated network structures that were broken down to their more asymmetric components with increased heating times.     

DWS microrheology of a linear polysaccharide

Diffusing wave spectroscopy has been used to measure the rheological behavior of pullulan (M(w) = 1 x 10(5)) aqueous solutions up to concentration of 40 g/dL. It was found that these solutions were mainly viscous, with the loss modulus G' higher than the elastic modulus G'. The plot of the specific viscosity eta(sp) as a function of pullulan concentration showed two critical concentrations c = 4 g/dL and c = 15 g/dL. For c < c, eta( sp) approximately c(1.25+/-0.05); for c < c < c, eta( sp) approximately c(2+/-0.05); and for c > c, eta( sp) approximately c(4.5+/-0.5). These results are in very good agreement with those reported in the literature.     

Evaluation of radius of gyration and intrinsic viscosity molar mass dependence and stiffness of hyaluronan

Nine hyaluronan (HA) samples were fractionated by size-exclusion chromatography, and molar mass (M), radius of gyration (Rg), and intrinsic viscosity ([eta]) were measured in 0.15 M NaCl at 37 degrees C by on-line multiangle light scattering and viscometer detectors. Using such method, we investigated the Rg and [eta] molar mass dependence for HA over a very wide range of molar masses: M ranging from 4 x 10(4) to 5.5 x 10(6) g/mol. The Rg and the [eta] molar mass dependence found for HA showed a meaningful difference. The Rg = f(M) power law was substantially linear in the whole range of molar masses explored with a constant slope of 0.6. In contrast, the [eta] = f(M) power law (Mark-Houwink-Sakurada plot) showed a marked curve shape, and a linear regression over the whole range of molar masses does not make sense. Also the persistence length (stiffness) for HA was estimated. The persistence length derived by using both the Odijk's model (7.5 nm from Rg vs M data) and the Bohdanecky's plot (6.8 nm from [eta] vs M data) were quite similar. These persistence length values are congruent with a semistiff conformation of HA macromolecules.     

The composition of the proteinaceous polysaccharides exuded by astragalus microcephalus,A. Gummifer and A. Kurdicus—The sources of turkish gum tragacanth

Gum tragacanth is a variable commodity because commercial samples may legitimately be admixtures, in any relative proportions, of the exudates from Asiatic Astragalus spp. Analytical data show that the exudates collected from the three major contributing Turkish spp., A. microcephalus, A. gummifer and A. kurdicus, differ extensively, particularly in terms of their fucose, xylose, galacturonic acid and methoxyl contents and in the relative proportions of their soluble (tragacanthin) and insoluble (bassorin) components. In addition, these three Astragalus exudates are shown to be proteinaceous polysaccharides; their amino acid compositions differ, particularly in terms of their hydroxyproline, histidine, aspartic acid and arginine content. In contrast, the amino acid compositions of the soluble and insoluble components of A. kurdicus do not differ extensively.     

Isolation and physical studies of the intact supercoiled, the open circular and the linear forms of ColE1-plasmid DNA.

For the study of DNA conformations, conformational transitions, and DNA-protein interactions, covalently closed supercoiled ColE1-plasmid DNA has been purified from cultures of Escherichia coli harboring this plasmid and grown in the presence of chloramphenicol according to the method of D.B. Clewell [J. Bact. 110 (1972)667]. The open circular and linear forms of the plasmid were prepared by digestion of the covalently closed, supercoiled form with pancreatic deoxyribonuclease and EcoRI-restriction endonuclease, respectively. The linear form was found to be very homogeneous by electron microscopy and sedimenting boundary analysis. Its physical properties (s0 20,w=16.3 S,D0 20,W=1.98 X 10(-8) cm2 s-1 and [eta]=2605 ml g-1) have been carefully determined in 0.2 M NaCl, 0.002 M NaPO4 pH 7.0,0.002 M EDTA, at 23 degrees C. Combination of s0 20, w (obtained by quasielastic laser light scattering) gave Ms,D=4.39 x 10(6). This value is in reasonable agreement with the molecular weight from total intensity laser light scattering M=4.30 x 10(6). The covalently closed and open circular forms of the ColE1-plasmid are less homogeneous due to slight cross-contamination and the presence of small amounts of dimers in these preparations. The weight fractions of the various components as determined by boundary analysis or electron microscopy are given together with the average quantities obtained in the same solvent for the supercoiled form ((s0 20,w)w=25.4 S, (D0 20,w)z=2.89 x 10(-8) cm2 s-1, [eta]= 788 ML G-1,Ms,D=4.69 x 10(6) and Mw=4.59 x 10(6)) and the open circular form (s0 20, w)w=20.1 S, (D0 20,w)z=2.45 x 10(-8) cm2 s-1, [eta]=1421 ml g-1,Ms,D=4.37 x 10(6) and Mw=4.15 x 10(6)). Midpoint analysis of the sedimenting boundaries allows unambiguous determination of the sedimentation coefficients of these two forms: s0 20,w=24.5 S and s0 20,w=18.8 S, respectively. Also deduced from total intensity light scattering were radii of gyration Rg (103.5, 134.2 and 186 nm) and second virial coefficients A2 (0.7, 4.8 AND 5.4 x 10(-4) mole ml/g2) for the supercoiled, the open circular and linear forms, respectively. The data presented are discussed in relation to the conformational parameters for the three forms in solution.     

Rheological properties of cashew gum

Solubilities and rheological properties of dissolved fractions of cashew gum from Anacardium occidentale were investigated. A fraction of gum (64.2%) dissolved in water at 30 °C. A further 13.4% dissolved when the remaining suspension was heated. The fraction that dissolved at 30 °C produced greater solution viscosity than the other fraction or the whole gum. When the pH was raised above 5.5, the solution viscosity dropped sharply.     

Correlation between antitumor activity, molecular weight, and conformation of lentinan

A (1-->3)-beta-D-glucan having (1-->6) branching (L-FV-IB) from Lentinus edodes in water was degraded into seven fractions of different molecular weights by ultrasonic irradiation, and each was further fractionated into three parts, by precipitation from water into acetone at room temperature. The weight-average molecular weight (M(w)), radius of gyration ((z)(1/2)), and intrinsic viscosity ([eta]) of lentinan and its fractions in 0.9% NaCl aqueous solution and dimethyl sulfoxide (Me(2)SO) were determined by size-exclusion chromatography combined with multi-angle laser light scattering (SEC-LLS), LLS, and viscometry. Analysis of M(w), [eta], and (z)(1/2) in terms of known theory for worm-like chains yielded 2240 +/- 100 nm(-1), and 100 +/- 10 nm for molar mass per unit contour length (M(L)), and persistence length (q), respectively, corresponding with theoretical data for triple-helical chains. The [alpha](D) of lentinan in water-Me(2)SO mixtures indicated an order-disorder transition. The results indicated that lentinan exists as a triple helix in 0.9% NaCl aqueous solution and as a single flexible chain in Me(2)SO. Assays in vivo and in vitro against the growth of Sarcoma 180 solid tumor as well as the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method for lentinan showed that the triple-helix sample exhibited a relatively high inhibition ratio. Interestingly, the triple-helix lentinan with M(w) of 1.49 x 10(6) exhibited the highest antitumor activity in vivo, having an inhibition ratio (xi) of 49.5%, close to that of 5-fluorouracil (xi = 50.5%), whereas the bioactivity (xi = 12.3%) of its single flexible chains almost disappeared. The triple-helix conformation plays an important role in enhancing the antitumor effects of lentinan.     

Flash extraction of pectin from orange albedo by steam injection

Pectin was acid extracted from orange albedo by steam injection heating under pressure. Extraction times ranged from 2 to 6 min at a pressure of about 15 psi. Solubilized pectin was characterized by HPSEC with online light scattering and viscosity detection. Molar mass (M), radius of gyration (R(g)), and intrinsic viscosity ([eta]) all decreased with increasing extraction time when heating temperature was 120 degrees C. At heating times of 3 min, M(w) ranged from 4.9 to 4.5 x 10(5), R(gz) was about 44 nm, and [eta](w) ranged from 8.4 to 7.9 dL/g. Chromatography revealed that solubilized pectin distributions were bimodal in nature at 3 min extraction time and trimodal when the extraction time was 6 min. Scaling law exponents obtained for the highest molar mass fractions were consistent with a very compact spherical structure. For the intermediate fraction, scaling law exponents were consistent with a less compact spherical structure comparable to a random coil. In the case of the low molar mass fractions, scaling law exponents were consistent with a structure more asymmetric in shape. These results are consistent with earlier results which indicated that pectin distributions were mixtures of two or more of the following due to disaggregation during extraction: spherical aggregates, hydrogen bonded network structures, and partially or fully disaggregated components of network structures which could include branched structures, rods, segmented rods, and kinked rods.     

Physicochemical properties and antitumor activities of water-soluble native and sulfated hyperbranched mushroom polysaccharides

A water-soluble hyperbranched beta-glucan, coded as TM3b, extracted from sclerotia of an edible fungus (Pleurotus tuber-regium) was fractioned into eight fractions coded as F1-F8 by a nonsolvent addition method. Five fractions were treated with chlorosulfonic acid at 35 degrees C to synthesize successfully sulfated derivatives coded as S-F2, S-F3, S-F4, S-F5, and S-F8 with degree of substitution of 0.28-0.54. The 13C NMR results of these sulfated beta-glucans indicated that while the C-6 position was fully substituted, C-2, C-3, and C-4 were only partially substituted by the sulfate groups. The weight-average molecular weights (Mw) and intrinsic viscosities ([eta]) of the native and sulfated TM3b fractions were determined using multi-angle laser light scattering and viscometry in 0.15M aq NaCl at 25 degrees C, respectively. The dependences of [eta] on Mw for TM3b and sulfated TM3b were found to be [eta]=0.18Mw(0.28+/-0.03) (Mw range from 3.30 x 10(4) to 3.90 x 10(7)) and [eta]=2.24 x 10(-2)Mw(0.52+/-0.06) (Mw range from 3.24 x 10(4) to 3.15 x 10(5)) in 0.15M aq NaCl at 25 degrees C, respectively. It revealed that both the native TM3b and its sulfated derivatives exist in a spherical chain conformation in 0.15M aq NaCl. Furthermore, the native and sulfated TM3b fractions showed potent antitumor activities in vivo and in vitro. The sulfated derivatives exhibited relatively higher in vitro antitumor activity against human hepatic cancer cell line HepG2 than the native TM3b. Water solubility and introduction of sulfate groups were the main factors in enhancing the antitumor activities.