The nonequilibrium phase and glass transition behavior of beta-lactoglobulin

Concentrated solutions of bovine beta-lactoglobulin were studied using osmotic stress and rheological techniques. At pH 6.0 and 8.0, the osmotic pressure was largely independent of NaCl concentration and could be described by a hard sphere equation of state. At pH 5.1, close to the isoelectric point, the osmotic pressure was lower at the lower NaCl concentrations (0 mM, 100 mM) and was fitted by an adhesive hard sphere model. Liquid-liquid phase separation was observed at pH 5.1 at ionic strengths of 13 mM and below. Comparison of the liquid-liquid and literature solid-liquid coexistence curves showed these solutions to be supersaturated and the phase separation to be nonequilibrium in nature. In steady shear, the zero shear viscosity of concentrated solutions at pH 5.1 was observed at shear rates above 50 s(-1). With increasing concentration, the solution viscosity showed a progressive increase, a behavior interpreted as the approach to a colloidlike glass transition at approximately 60% w/w. In oscillatory shear experiments, the storage modulus crossed the loss modulus at concentrations of 54% w/w, an indication of the approaching glass transition. Comparison of the viscous behavior with predictions from the Krieger-Dougherty equation indicates the hydrodynamic size of the protein decreases with increasing concentration, resulting in a slower approach to the glass transition than a hard sphere system.     

Viscoelastic properties of solutions of ovine submaxillary mucin

The linear viscoelastic and rheological properties of high molecular weight ovine submaxillary mucin (OSM) solution have been investigated in terms of the Newtonian steady-flow viscosity [eta(gamma)], the complex oscillatory viscosity [eta*(omega)], and the storage and loss shear moduli [G'(omega) and G"(omega)]. It was observed that tau(gamma), eta*(omega), and G'(omega) are always higher when OSM is dissolved in 0.1M NaCl than when at the same concentration in 6M GdnHCl. This is consistent with previous observations that submaxillary mucins self-associate in 0.1M NaCl to form large aggregates, which are disrupted in 6M GdnHCl. As the OSM concentration increases, the appearance of a plateau shear modulus indicates the formation of a gel network in both solvents. The results suggest gelation involves specific intermolecular interactions, perhaps due to hydrophobic forces between interdigitated oligosaccharide side chains. The viscoelastic behavior of OSM solution at high concentration is thus similar to that reported in the literature for porcine gastric mucin (PGM). However, the OSM gels are mechanically weaker, having moduli that are an order of magnitude lower than those for PGM gels of comparable concentration. The oligosaccharide side chains of OSM consist of only 1-2 sugar units compared to 10-15 for PGM, but it appears that this is sufficient to allow for intermolecular interaction and the formation of weak gels.     

Effect of concentration and temperature on the rheological behavior of collagen solution

Dynamic viscoelastic properties of collagen solutions with concentrations of 0.5-1.5% (w/w) were characterized by means of oscillatory rheometry at temperatures ranging from 20 to 32.5 degrees C. All collagen solutions showed a shear-thinning flow behavior. The complex viscosity exhibited an exponential increase and the loss tangent decreased with the increase of collagen concentration (C(COL)) when the C(COL)> or =0.75%. Both storage modulus (G') and loss modulus (G') increased with the increase of frequency and concentration, but decreased with the increase of temperature and behaved without regularity at 32.5 degrees C. The relaxation times decreased with the increase of temperature for 1.0% collagen solution. According to a three-zone model, dynamic modulus of collagen solutions showed terminal-zone and plateau-zone behavior when C(COL) was no more than 1.25% or the stated temperature was no more than 30 degrees C. The concentrated solution (1.5%) behaved being entirely in plateau zone. An application of the time-temperature superposition (TTS) allowed the construction of master curve and an Arrhenius-type TTS principle was used to yield the activation energy of 161.4 kJ mol(-1).     

Rheological characterization of bioadhesive binary polymeric systems designed as platforms for drug delivery implants

This study describes the formulation and characterization of binary interactive polymeric systems, designed as platforms for improved drug delivery to mucosal sites. Binary interactive systems were manufactured containing hydroxyethylcellulose (HEC; 1-5% w/w) and polycarbophil (PC; 1-5% w/w) at pH 7, and their rheological (flow and dynamic), mechanical, and mucoadhesive properties were characterized, both before and after dilution with phosphate buffered saline (designed to mimic dilution by biological fluids). Physical interactions between HEC and PC were confirmed by the observed rheological synergy. Within the binary interactive systems increasing polymer concentration increased the storage modulus (G'), loss modulus (G' '), dynamic viscosity (eta'), hardness, compressibility, consistency, and mucoadhesion yet decreased the loss tangent. This was attributed to enhanced entanglements and interactions between adjacent polymer chains. Dilution with PBS altered the above properties; however, the binary interactive systems, particularly those containing higher concentrations of HEC, still exhibited predominantly elastic properties (high G', low tan delta). In light of this, it is suggested that the rheological and mucoadhesive properties of binary interactive systems composed of HEC (5% w/w) and PC (1-3% w/w) offered particular promise as platforms for topical mucosal drug delivery systems.     

Dynamic shear properties of the porcine molar periodontal ligament

The role of the periodontal ligament (PDL) is to support the tooth during function and resist external forces applied to it. The dominant vertical component of these forces is associated with shear in the PDL. Little information, however, is available on the dynamic behavior of the PDL in shear. Therefore, the present study was designed to determine the dynamic shear properties of the PDL in the porcine molar (n=10). From dissected mandibles transverse sections of the mesial root of the first molar were obtained at the apical and coronal levels and used for dynamic shear tests. Shear strain (0.5%, 1.0%, and 1.5%) was applied in superoinferior direction parallel to the root axis with a wide range of frequencies (0.01-100 Hz). The dynamic complex and storage moduli increased significantly with the loading frequency, the dynamic loss modulus showed only a small increase. The dynamic elasticity was significantly larger in the coronal region than in the apical region although the dynamic viscosity was similar in both regions. The present results suggest that non-linearities, compression/shear coupling, and intrinsic viscoelasticity affect the shear material behavior of the PDL, which might have important implications for load transmission from tooth to bone and vice versa.     

Rheological properties of water-soluble spruce O-acetyl galactoglucomannans

The thermal and rheological properties of spray-dried, ethanol-precipitated, purified, and deacetylated spruce galactoglucomannans (GGM) were investigated by rheological measurements and differential scanning calorimetry. The shear rate dependence of viscosity and the effects of the drying method, temperature, ionic strength, and deacetylation on rheological properties were studied. GGM solutions exhibited a shear thinning behaviour. GGM solutions did not obey the Cox–Merz rule. The storage modulus of GGM solutions increased with an increase in concentration; gradually until a concentration of 5%, but rapidly at higher concentrations. Ethanol-precipitated GGM solutions showed a more elastic behaviour than spray-dried GGM solutions. Deacetylation caused an increase in apparent viscosity and more significantly in storage modulus. The storage modulus increased slightly with a decrease in temperature. A small amount addition of NaCl slightly changed the oscillatory behaviour. The effects of above factors were discussed in terms of molecular interactions. The rheological measurements of GGM solutions provide the basis of functionalities of GGM solutions.     

Rheological properties of suspensions containing cross-linked starch nanoparticles prepared by spray and vacuum freeze drying methods

The rheological behavior of suspensions containing vacuum freeze dried and spray dried starch nanoparticles was investigated to explore the effect of these two drying methods in producing starch nanoparticles which were synthesized using high pressure homogenization and mini-emulsion cross-linking technique. Suspensions containing 10% (w/w) spray dried and vacuum freeze dried nanoparticles were prepared. The continuous shear viscosity tests, temperature sweep tests, the frequency sweep and creep-recovery tests were carried out, respectively. The suspensions containing vacuum freeze dried nanoparticles showed higher apparent viscosity within shear rate range (0.1-100s(-1)) and temperature range (25-90°C). The suspensions containing vacuum freeze dried nanoparticles were found to have more shear thinning and less thixotropic behavior compared to those containing spray dried nanoparticles. In addition, the suspensions containing vacuum freeze dried particles had stronger elastic structure. However, the suspensions containing spray dried nanoparticles had more stiffness and greater tendency to recover from the deformation.     

魔芋葡甘聚糖水溶胶的粘度行为研究

对魔芋葡甘聚糖(KGM)水溶胶在不同剪切速率、浓度、放置时间、温度等条件下的粘度行为进行了研究.结果表明,水溶胶的粘度随着剪切速率的增加而呈指数降低,属于非牛顿流体,1%的KGM水溶胶粘度η(10-4mpa·s)与剪切速率γ(s-1)的经验公式为η=1.41+9.04e-γ/0.107;粘度η(10-4mpa·s)随KGM质量分数ω(%)增加而呈指数增加,二者关系符合η=3.88eω/0.632;1%的KGM水溶胶粘度η(10-4mpa·s)随放置时间t(h)的增加而下降,可用多项关系式η=4.93+0.027t-5.15×10-4t2来拟合;温度升高则粘度会下降,1%的KGM水溶胶的粘流活化能为14.90 kJ/mol.此外,还分别探讨了不同电解质(如NaCl,NaOH,HCl)及表面活性剂(如CTAB,SDS,Tween 80)等对KGM水溶胶粘度的影响规律.     

Effects of sodium chloride,guanidine hydrochloride,and sucrose on the viscoelastic properties of sodium hyaluronate solutions

Effects of sodium chloride (NaCl), guanidine hydrochloride (GuHCl), or sucrose on the viscoelasticity of sodium hyaluronate (NaHA) solutions were studied. NaCl and GuHCl decreased both storage and loss moduli, while sucrose increased both moduli. The critical concentration C* was determined as an inflection point in the plot of zero shear specific viscosity vs concentration for NaHA solutions with and without NaCl, GuHCl, or sucrose. It is suggested that sodium ions or guanidinium ions shield the electrostatic repulsion of NaHA molecules, hence reduce the coil dimension, and C* shifted to higher concentrations. However, sucrose enhances the entanglement coupling between NaHA molecules and retards the disentanglement of molecular chains or promotes to create hydrogen bonds, and then C* for NaHA solutions with sucrose shifts to lower concentrations. This is in agreement with the results of light scattering measurements in the presence of 0.2M NaCl. Both the radius of gyration and hydrodynamic radius of NaHA were reduced in dilute solutions by the addition of sucrose, and added sucrose enhances the interaction between NaHA monomer units. In the case of concentrated NaHA solution, such interactions result to increase the storage and loss moduli because of the enhancement of temporary network formation. © 1999 John Wiley & Sons, Inc. Biopoly 50: 23–34, 1999     

Viscoelastic properties of human tracheobronchial mucin in aqueous solution

Human tracheobronchial mucin isolated from cystic fibrosis patients (CF HTBM) was purified using a combination of gel filtration and density gradient centrifugation. The resulting mucin was fractionated to reduce polydispersity and to facilitate studies of the molecular weight dependence of mucin viscoelasticity in concentrated solution. The viscoelastic properties of CF HTBM were examined in distilled water, 0.1M salt solutions and chaotropic solvents. In controlled strain experiments (strain ≥ 5%) with increasing mucin concentration, a crossover from sol to gel behavior is observed. The gel strength, as measured by the magnitude of the storage modulus at comparable mucin concentrations, is greatest for distilled water, intermediate for 0.1M NaCl, and lowest far 6M GdnHCl. In distilled water, high molecular weight mucin undergoes a sol-gel transition at ～ 12 mg/mL, and shows evidence of a plateau modulus at higher concentrations. The storage and loss moduli of concentrated high molecular weight fractions in 6M GdnHCl exhibit a power law dependence on frequency typical of weak gels near the sol–gel transition at 20 mg/mL. Similar rheology is observed in 0.1M NaCl and 0.091M NaCl/3 mM CaCl₂, but with evidence for additional weak associations at low frequency. The power law exponent in these systems is 0.70 ± 0.02, in good agreement with prediction for networks formed by a percolation mechanism. Low molecular weight fractions in these solvents exhibit a fluid-like viscoelastic response. However, low molecular weight mucin in distilled water shows a strain-dependent increase in elasticity at low frequency indicative of weak intermolecular associations. Comparison of the rheological behavior of CF HTBM with our earlier studies of ovine submaxillary mucin lends support to the idea that carbohydrate side-chain interactions are important in the gelation mechanism of mucins. © 1995 John Wiley & Sons, Inc.     

Viscoelastic evaluation of topical creams containing microcrystalline cellulose/sodium carboxymethyl cellulose as stabilizer

The purpose of this study was to examine the viscoelastic properties of topical creams containing various concentrations of microcrystalline cellulose and sodium carboxymethyl cellulose (Avicel(R) CL-611) as a stabilizer. Avicel CL-611 was used at 4 different levels (1%, 2%, 4%, and 6% dispersion) to prepare topical creams, and hydrocortisone acetate was used as a model drug. The viscoelastic properties such as loss modulus (G"), storage modulus (G'), and loss tangent (tan delta) of these creams were measured using a TA Instruments AR 1000 Rheometer and compared to a commercially available formulation. Continuous flow test to determine the yield stress and thixotropic behavior, and dynamic mechanical tests for determining the linear viscosity time sweep data, were performed. Drug release from the various formulations was studied using an Enhancer TM Cell assembly. Formulations containing 1% and 2% Avicel CL-611 had relative viscosity, yield stress, and thixotropic values that were similar to those of the commercial formulation. The elastic modulus (G') of the 1% and 2% formulation was relatively high and did not cross the loss modulus (G"), indicating that the gels were strong. In the commercial formulation, G' increased after preshearing and broke down after 600 seconds. The strain sweep tests showed that for all formulations containing Avicel CL-611, the G' was above G" with a good distance between them. The gel strength and the predominance of G' can be ranked 6% > 4% > 2%. The strain profiles for the 1% and 2% formulations were similar to those of the commercial formulation. The delta values for the 1% and 2% formulations were similar, and the formulations containing 4% Avicel CL-611 had lower delta values, indicating greater elasticity. Drug release from the commercial preparation was fastest compared to the formulations prepared using Avicel CL-611, a correlation with the viscoelastic properties. It was found that viscoelastic data, especially the strain sweep profiles of products containing Avicel CL-611 1% and 2%, correlated with the commercial formulation. Rheological tests that measure the viscosity, yield stress, thixotropic behavior, other oscillatory parameters such as G' and G" are necessary tools in predicting performance of semisolids.     

Physicochemical characterization of bioactive polyacrylic acid organogels as potential antimicrobial implants for the buccal cavity

This study describes the formulation and physicochemical characterization of poly(acrylic acid) (PAA) organogels, designed as bioactive implants for improved treatment of infectious diseases of the oral cavity. Organogels were formulated containing a range of concentrations of PAA (3-10% w/w) and metronidazole (2 or 5% w/w, representing a model antimicrobial agent) in different nonaqueous solvents, namely, glycerol (Gly), polyethylene glycol (PEG 400), or propylene glycol (PG). Characterization of the organogels was performed using flow rheometry, compressional analysis, oscillatory rheometry, in vitro mucoadhesion, moisture uptake, and drug release, methods that provide information pertaining to the nonclinical and clinical use of these systems. Increasing the concentration of PAA significantly increased the consistency, compressibility, storage modulus, loss modulus, dynamic viscosity, mucoadhesion, and the rate of drug release. These observations may be accredited to enhanced molecular polymer entanglement. In addition, the choice of solvent directly affected the physicochemical parameters of the organogels, with noticeable differences observed between the three solvents examined. These differences were accredited to the nature of the interaction of PAA with each solvent and, importantly, the density of the resultant physical cross-links. Good correlation was observed between the viscoelastic properties and drug release, with the exception of glycerol-based formulations containing 5 and 10% w/w PAA. This disparity was due to excessive swelling during the dissolution analysis. Ideally, formulations should exhibit controlled drug release, high viscoelasticity, and mucoadhesion, but should flow under minimal stresses. Based on these criteria, PEG 400-based organogels composed of 5% or 10% w/w PAA exhibited suitable physicochemical properties and are suggested to be a potentially interesting strategy for use as bioactive implants designed for use in the oral cavity.     

Viscoelastic behavior and in vivo release study of microgel dispersions with inverse thermoreversible gelation

The dispersion of microgels with two interpenetrating polymer networks of poly( N-isopropylacrylamide) and poly(acrylic acid) (PNIPAM-IPN-PAAc) has been studied for its viscoelastic behavior, biocompatibility, and in vivo release properties. The IPN microgels in water had an average hydrodynamic radius of about 85 nm at 21 degrees C, measured by dynamic light scattering method. The atomic force microscope image showed that the particles were much smaller after they were dried but remained spherical shape. The storage and loss moduli ( G' and G') of dispersions of IPN microgels were measured in the linear stress regime as functions of temperature and frequency at various polymer concentrations using a stress-controlled rheometer. For dispersions with polymer concentrations of 3.0 and 6.0 wt % above 33 degrees C, the samples behave as viscoelastic solids and the storage modulus was larger than the loss modulus over the entire frequency range. The loss tangent was measured at various frequencies as a function of temperature. The gelation temperature was determined to be 33 degrees C at the point where a frequency-independent value of the loss tangent was first observed. At pH 2.5, when heated above the gelation temperature, IPN microgels flocculate by pumping a large amount of water from the gel. When the pH value was adjusted to neutral, deprotonation of -COOH groups on PAAc made the microgel keep water even above the gelation temperature. Using an animal implantation model, the biocompatibility and drug release properties of the IPN microgel dispersion were evaluated. Fluorescein as a model drug was mixed into an aqueous microgel dispersion at ambient temperature. This drug-loaded liquid was then injected subcutaneously in Balb/C mice from Taconic Farms. The test results have shown that the IPN microgels did not adversely promote foreign body reactions in this acute implantation model and the presence of gelled microgel dispersion substantially slowed the release of fluorescein.     

Rheological characterization of the galactomannan from Leucaena leucocephala seed

A water soluble galactomannan isolated from Leucaena leucocephala seeds gave an intrinsic viscosity of 3.5dl/g and viscosity average molecular mass, M(v), of 6.98×10(5)g/mol. This was in reasonably good agreement with the value of the weight average molecular mass, M(w), of 5.44±0.20×10(5)g/mol determined by GPC-MALLS coupled to RI. The onset of polymer coil overlap occurred at c*[η] of 2.1, with slope of 3.0 above and 1.3 below the point of polymer coil overlap. The shear viscosity of the polysaccharide was temperature dependent and decreased with increasing temperature. The activation energy for viscous flow of 3.0% polysaccharide concentration obtained by Arrhenius plot of zero shear viscosity as a function of temperature was 26.4kJ/mol. Both the storage modulus (G') and loss modulus (G″) showed strong dependence on frequency indicating the presence of entangled coils. The Cox-Merz plot gave close superimposition of the complex and shear viscosities.     

Synthesis and Fungicidal Activity of Diaryl 1,1 -Dichloroethyl-phosphonates

Non-Newtonian behavior and dynamic viscoelasticity of a series of aqueous mixed solutions of xanthan and locust bean gum were measured using a rheogoniometer, and the rheological properties were analysed. A gelation occurred in the mixture at the concentration of 0.2% total gums at room temperature. The flow curves of the mixture solutions showed a yield value and approximated to plastic behavior at 50°C. The maximum dynamic modulus was obtained when the mixing ratio of xanthan to locust bean gum was 1:2, while comparable high moduli were also obtained in the mixing ratio of 1: 3 or 1:4. A mixture of deacetylated xanthan and locust bean gum showed the highest dynamic modulus, about two times that of the mixture of native or Na-form xanthan. The dynamic modulus of the mixtures decreased rapidly with increasing temperature. In contrast, the dynamic viscosity was scarcely changed during increasing temperature in the mixing ratio of 2: 1. The dynamic modulus was decreased by addition of urea (4.0 M), NaCl (0.1%) and MgCl₂. We concluded that the intermolecular interaction between xanthan and locust bean gum might occur between the side chains of the former and backbone of the latter, as in a lock-and-key effect.     

Sclerotium rolfsii scleroglucan: the promising behavior of a natural polysaccharide as a drug delivery vehicle, suspension stabilizer and emulsifier

Gel matrices of scleroglucans from Sclerotium rolfsii ATCC 201126 (EPS I and EPS II, from 48-h and 72-h fermentations, respectively) were evaluated on their release kinetics of theophylline (Th). Equivalent polymer (2%, w/w) and Th (0.2%, w/w) concentrations showed almost coincident drug release patterns, independently of polymer molecular weight or the microstructural properties of gel matrices. Dynamic rheological studies of scleroglucan hydrogel structures (storage, G', and loss, G', moduli) indicated a solid-like behavior. Differences on pore size dimensions (EPS I=20 microm and EPS II=7 microm) were in accordance to the differences in G' (EPS I=113 Pa and EPS II=161 Pa), a fact likely related to variations in the cross-linking density of polymer networks. Compared to already known biopolymers, EPS I and EPS II at 0.5 g/L showed a good dispersing ability against particulate suspensions of activated charcoal, bentonite, CaCO(3), celite and quartz powder. Emulsifying ability of both EPSs at 2g/L was high (E=56-60%) when tested with kerosene, moderate ( approximately 30%) with hexadecane, and negligible in the presence of olive oil-in-water emulsions.     

Changes of the dynamic properties of tamarind (Tamarindus indica) gel with different saccharose and polysaccharide concentrations

The dynamic properties (storage moduli, G′ and loss moduli, G″) of tamarind gels and the influence of saccharose and polysaccharide concentrations were studied using model rings of 3 mm thickness and 20 mm diameter, prepared with three saccharose (55, 60 and 65% w/v) and three polysaccharide concentrations (1.5, 2.0 and 2.5% w/v). Small amplitude oscillatory measures were taken at 25°C in a PHYSICA LS 100 rheometer with parallel plate geometry. Results for the 9 gels showed the zone of linear viscoelasticity between 0.637 and 6.37 Pa of oscillatory shear stress. The mechanical spectra obtained after 24, 48 and 72 h evidenced the presence of syneresis with an increase in G′ as a function of time. The effects of polysaccharide concentrations on gel viscoelasticity were greater than those of saccharose.     

Viscoelastic shear properties of the corneal stroma

The cornea is a highly specialized transparent tissue which covers the front of the eye. It is a tough tissue responsible for refracting the light and protecting the sensitive internal contents of the eye. The biomechanical properties of the cornea are primarily derived from its extracellular matrix, the stroma. The majority of previous studies have used strip tensile and pressure inflation testing methods to determine material parameters of the corneal stroma. Since these techniques do not allow measurements of the shear properties, there is little information available on transverse shear modulus of the cornea. The primary objectives of the present study were to determine the viscoelastic behavior of the corneal stroma in shear and to investigate the effects of the compressive strain. A thorough knowledge of the shear properties is required for developing better material models for corneal biomechanics. In the present study, torsional shear experiments were conducted at different levels of compressive strain (0–30%) on porcine corneal buttons. First, the range of linear viscoelasticity was determined from strain sweep experiments. Then, frequency sweep experiments with a shear strain amplitude of 0.2% (which was within the region of linear viscoelasticity) were performed. The corneal stroma exhibited viscoelastic properties in shear. The shear storage modulus, G′, and shear loss modulus, G″, were reported as a function of tissue compression. It was found that although both of these parameters were dependent on frequency, shear strain amplitude, and compressive strain, the average shear storage and loss moduli varied from 2 to 8 kPa, and 0.3 to 1.2 kPa, respectively. Therefore, it can be concluded that the transverse shear modulus is of the same order of magnitude as the out-of-plane Young's modulus and is about three orders of magnitude lower than the in-plane Young's modulus.     

Local rheology of human neutrophils investigated using atomic force microscopy

During the immune response, neutrophils display localized mechanical events by interacting with their environment through the micro-vascular transit, trans-endothelial, and trans-epithelial migration. Nano-mechanical studies of human neutrophils on localized nano-domains could provide the essential information for understanding their immune responsive functions. Using the Atomic Force Microscopy (AFM)-based micro-rheology, we have investigated rheological properties of the adherent human neutrophils on local nano-domains. We have applied the modified Hertz model to obtain the viscoelastic moduli from the relatively thick body regions of the neutrophils. In addition, by using more advanced models to account for the substrate effects, we have successfully characterized the rheological properties of the thin leading and tail regions as well. We found a regional difference in the mechanical compliances of the adherent neutrophils. The central regions of neutrophils were significantly stiffer (1,548 ± 871 Pa) than the regions closer to the leading edge (686 ± 801 Pa), while the leading edge and the tail (494 ± 537 Pa) regions were mechanically indistinguishable. The frequency-dependent elastic and viscous moduli also display a similar regional difference. Over the studied frequency range (100 to 300 Hz), the complex viscoelastic moduli display the partial rubber plateau behavior where the elastic moduli are greater than the viscous moduli for a given frequency. The non-disparaging viscous modulus indicates that the neutrophils display a viscoelastic dynamic behavior rather than a perfect elastic behavior like polymer gels. In addition, we found no regional difference in the structural damping coefficient between the leading edge and the cell body. Thus, we conclude that despite the lower loss and storage moduli, the leading edges of the human neutrophils display partially elastic properties similar to the cell body. These results suggest that the lower elastic moduli in the leading edges are more favorable for the elastic fluctuation of actin filaments, which supports the polymerization of the actin filaments leading to the active protrusion during the immune response.     

Characterization of a novel bioflocculant, p-KG03, from a marine dinoflagellate, Gyrodinium impudicum KG03

The flocculating activity of an exopolysaccharide, p-KG03, produced by a marine dinoflagellate Gyrodinium impudicum KG03 was investigated. The p-KG03 was a highly sulfated exopolysaccharide that showed strong antiviral activity against encephalomyocarditis virus (EMCV) and immunostimulating activity by NK cell activation. For the industrial applications of p-KG03, as the bioflocculant agent, p-KG03 showed that more than 90% of the flocculating activity in kaolin suspension occurred at concentrations of 0.5 mg/l with the maximum at 1.0 mg/l. However, flocculation decreased from 2.5 mg/l. The flocculation rate increased linearly with concentration and was higher than that observed in commercial products such as polyacrylamide (approximately 1.0 mg/l) or zooglan (approximately 3.0 mg/l). The p-KG03 was an effective flocculant under acidic conditions (pH 3-6) and over a wide temperature range (4-90 degrees C). The presence of cations did not enhance flocculating activity. The average molecular mass, as determined by gel filtration chromatography, was about 1.87 x 10(3) KDa. Galactose was the main sugar in p-KG03, which also contained uronic acid (2.9%, w/w) and sulfate groups (10.3%, w/w). The infrared spectrum of p-KG03 showed absorption bands of carboxylate groups. Thermogravimetric analysis indicated a degradation temperature (T(d)) of 250 degrees C. Several other properties of p-KG03 such as intrinsic viscosity, the rheological behavior, consistency index (k) and flow behavior index (eta) were also studied.