On the hydrodynamics and temperature dependence of the solution conformation of human serum albumin from viscometry approach

The paper presents the results of viscosity determinations on aqueous solutions of human serum albumin (HSA) at a wide range of concentrations and at temperatures ranging from 5 to 45 degrees C. On the basis of a modified Arrhenius formula and Mooney's equation, the viscosity-temperature and viscosity-concentration dependence of the solutions are discussed. The effective specific volume, the activation energy and entropy of viscous flow for hydrated HSA were calculated. Different models of HSA molecule are discussed and the best one-from the hydrodynamic point of view-was established. At low concentration limit, such rheological quantities as the intrinsic viscosity and Huggins coefficient were obtained. Using the dimensionless parameter [eta]c, the existence of three characteristic ranges of concentrations: diluted, semi-diluted and concentrated, was shown.     

A comparison of solution conformation and hydrodynamic properties of equine, porcine and rabbit serum albumin using viscometric measurements

This paper presents the results of viscosity determinations on aqueous solutions of equine, porcine and rabbit serum albumin over a wide range of concentrations and at temperatures ranging from 5 degrees C to (42-45) degrees C. The results are compared with human and bovine serum albumin previously studied. Viscosity-temperature dependence is discussed on the basis of the modified Arrhenius formula. The effective specific volume, the activation energy and entropy of viscous flow for all investigated albumins are compared. Viscosity-concentration dependence, in turn, is discussed on the basis of Mooney equation. Based on the assumption that theoretical and experimental values of Simha factor--at high temperature limit--are equal to each other, the hydrodynamic volume of the studied albumins has been calculated. The numerical values of a self-crowding factor were also obtained. At low concentration limit, the numerical values of the intrinsic viscosity and of Huggins coefficient were compared.     

Viscosity analysis of the temperature dependence of the solution conformation of ovalbumin

The viscosity of ovalbumin aqueous solutions was studied as a function of temperature and of protein concentration. Viscosity-temperature dependence was discussed on the basis of the modified Arrhenius formula at temperatures ranging from 5 to 55 degrees C. The activation energy of viscous flow for hydrated and unhydrated ovalbumin was calculated. Viscosity-concentration dependence, in turn, was discussed on the basis of Mooney equation. It has been shown that the shape parameter S decreases with increasing temperature, and self-crowding factor K does not depend on temperature. At low concentration limit the numerical values of the intrinsic viscosity and of Huggins coefficient were calculated. A master curve relating the specific viscosity etasp to the reduced concentration c[eta], over the whole range of temperature, was obtained and the three ranges of concentrations: diluted, semi-diluted and concentrated, are discussed. It has been proved that the Mark-Houvink-Kuhn-Sakurada (MHKS) exponent for ovalbumin does not depend on temperature.     

Viscosity of alpha-crystallin solutions

Accommodation in the mammalian lens requires flexure of lens fibres and some redistribution of their contents involving limited viscous flow. Shear-dependent viscosity of bovine alpha-crystallin solutions was determined with the Contraves Low-Shear Rheometer between 4.4 and 347 mg ml(-1), and at 15.5, 25, 30, and 37 degrees C. All solutions showed significant shear thinning, with markedly higher viscosity at physiological levels of approximately 300 mg ml(-1). Viscosity-concentration graphs were similar at low (1.0 s(-1)) and high (94.5 s(-1)) shear rates, indicating low molecular interaction in solution. Arrhenius plots which might have indicated the size of the energy barrier to displacement of molecules or aggregates were inconclusive.     

Determination of Some Hydrodynamic Parameters of Ovine Serum Albumin Solutions Using Viscometric Measurements

The influence of protein concentration and temperature on the viscosity of ovine serum albumin (OSA) solutions was studied. The Mooney equation and a modified Arrhenius formula were used to described the viscosity-concentration and viscosity-temperature dependence of the solutions, respectively. The effective specific volume, the activation energy and entropy of viscous flow for hydrated OSA were calculated. The axial ratio and the dimensions of the main semi-axes of hydrated OSA were established. At low concentration limit, the temperature dependence of the intrinsic viscosity and Huggins coefficient is presented. Comparison of some hydrodynamic parameters obtained for different proteins has been made.     

Rheological characterization of levan polysaccharides from Microbacterium laevaniformans

Levan polysaccharides were produced from Microbacterium laevaniformans and its rheological behaviors were characterized as a function of concentration and temperature. The intrinsic viscosity of the purified levan was determined to be 0.38dL/g at 25 degrees C which was relatively higher than that of levans from other microbial sources. The flow behaviors of the levan solutions were characterized by the increase in the shear stress, giving more increments in the shear rate. Thus, the levan solutions exhibited the pseudoplastic behavior, which was characterized by the power law model. In addition, the flow behaviors of the levans were satisfactorily fitted to the Arrhenius equation where the activation energy of flow (Ea) decreased from 24.07 to 13.53kJ/mol (R2=0.98-0.99) with increasing concentrations. Moreover, the exponential equation was favorably applied to describe the effect of concentration on the apparent viscosity of the levan polysaccharides.     

Rheology of concentrated isotropic and anisotropic xanthan solutions: 3. Temperature dependence

The oscillatory rheology of one rodlike and one semiflexible xanthan sample has been investigated as a function of temperature in the range of xanthan concentrations where the polymer forms a lyotropic liquid crystalline phase in aqueous NaCl solutions. Readily observed changes in the rheological observables at temperatures corresponding to phase boundaries permit construction of the biphasic chimney region of the temperature-composition phase diagram. The chimney region leans toward larger values of the polymer concentration with increasing temperature, presumably as a consequence of a reduction in the effective axial ratio of the helical polymer with increasing temperature. The results permit construction of plots of the rheological observables as a function of polymer concentration at temperatures T in the range 20 相似文献   

A jump in an Arrhenius plot can be the consequence of a phase transition. The binding of ATP to myosin subfragment 1

The temperature dependence of the kinetics of the binding of ATP to myosin subfragment-1 was studied by an ATP chase technique in a rapid-flow-quench apparatus: (formula; see text) A temperature range of 30 degrees C to -15 degrees C was obtained with ethylene glycol as antifreeze. The Arrhenius plot of k2 is discontinuous with a jump at 12 degrees C. Above the jump delta H+ = 9.5 kcal/mol, below delta H+ = 28.5 kcal/mol. Few such Arrhenius plots are recorded in the literature but they are predicted from theory. Thus, we explain our results as a phase change of the subfragment 1-ATP system at 12 degrees C. This is in agreement with certain structural studies.     

Pullulan-sodium alginate based edible films: Rheological properties of film forming solutions

Rheological properties of pullulan, sodium alginate and blend solutions were studied at 20 °C, using steady shear and dynamic oscillatory measurements. The intrinsic viscosity of pure sodium alginate solution was 7.340 dl/g, which was much higher than that of pure pullulan (0.436 dl/g). Pure pullulan solution showed Newtonian behavior between 0.1 and 100 s⁻¹ shear rate range. However, increasing sodium alginate concentration in pullulan-alginate blend solution led to a shear-thinning behavior. The effect of temperature on viscosities of all solutions was well-described by Arrhenius equation. Results from dynamical frequency sweep showed that pure sodium alginate and blend solutions at 4% (w/w) polymer concentration were viscoelastic liquid, whereas the pure pullulan exhibited Newtonian behavior. The mechanical properties of pure sodium alginate and pullulan-alginate mixture were analyzed using the generalized Maxwell model and their relaxation spectra were determined. Correlation between dynamic and steady-shear viscosity was analyzed with the empirical Cox-Merz rule.     

Temperature-dependent abnormalities of the erythrocyte membrane in porcine malignant hyperthermia

The temperature dependence of ATPase activities and stearic acid spin label motion in red blood cells of normal and MH-susceptible pigs have been examined. Arrhenius plots of red blood cell ghost Ca-ATPase and calmodulin-stimulable Ca-ATPase activities were identical for both normal and MH erythrocyte ghosts. Arrhenius plots of Mg-ATPase activity exhibited a break (defined as a change in slope) at 24 degrees C in both MH and normal erythrocyte ghosts. However, below 24 degrees C the apparent activation energy for this activity was less in MH than normal ghosts. To determine whether breaks in ATPase Arrhenius plots could be correlated with changes in the physical state of the red blood cell membrane, the spin label 16-doxyl-stearate was introduced into the bilayer of both erythrocyte ghosts and red blood cells. With both ghosts and intact cells, at each temperature examined, the mobility of the probe in the lipid bilayer, as measured by electron paramagnetic resonance, was greater in normal than in MH membranes. While there were no breaks in Arrhenius plots for probe motion in the erythrocyte ghosts, the apparent activation energy for probe motion was significantly greater in normal than in MH ghost membranes. While there was no break in the Arrhenius plot of probe motion in normal intact red blood cell membranes, there were breaks in the Arrhenius plot of probe motion at both 24 and 33 degrees C in intact MH red blood cell membranes. Based on the altered temperature dependence of Mg-ATPase activity and spin probe motion in membranes derived from MH red blood cells, we conclude that there may be a generalized membrane defect in MH pigs which is reflected in the red blood cell as an altered membrane composition or organization.     

Effect of growth temperature on membrane dynamics in a thermophilic cyanobacterium: a spin label study

A strain of Synechococcus sp. was grown at its optimal growth temperature (58 degrees C) and at 38 degrees C, in order to investigate possible adaptations of membrane-related properties to growth temperature. Light-induced electron transport in thylakoid membranes from both types of cells showed linear Arrhenius plots with the same activation energy (48 kJ/mol). Membranes from cells grown at 58 degrees C had a higher temperature optimum (53 degrees C) than those from cells grown at 38 degrees C (41 degrees C). Growth at 38 degrees C caused an increase in the proportion of unsaturated fatty acids compared to growth at 58 degrees C. The fluidity of the membranes was investigated by measuring the temperature dependence of the parameters derived from electron spin resonance spectra of the spin-labels 5-doxyldecane, 5-doxylstearate and 16-doxylstearate. Only small differences between the dynamic properties of the membranes from cells grown at different temperatures could be detected. This suggests that the observed change in fatty acid composition of the membranes following the change in growth temperature does not serve to maintain a constant viscosity at the growth temperature.     

Complex viscosity of bovine red blood cells in suspensions

The complex viscosity eta* has been measured of bovine red blood cells suspended in a medium of isotonic NaCl solutions including dextran and buffered with potassium phosphate at pH 7.0. A multiple lumped resonator apparatus was used at the frequencies of 144, 572, 1491, 3742, and 8026 Hz at 20.0 degrees C. Due to the high molecular weight of dextran the medium also exhibited some visco-elasticity eta s*. So we adopted the complex specific viscosity eta sp* = (eta*-eta s*)/[eta s*]. At 20.0 degrees C eta sp* decreased with the frequency where the hematocrit was 0.233 and eta s 0.34 poise. The measurements were made for the medium with different viscosity at 5.0 degrees C and 25.0 degrees C. The results are compared with the theory of elastic shells.     

Changes in the form of Arrhenius plots of the activity of glucagon-stimulated adenylate cyclase and other hamster liver plasma-membrane enzymes occurring on hibernation.

1. Arrhenius plots of the glucagon-stimulated adenylate cyclase, 5'-nucleotidase, (Na+ + K+)-stimulated adenosine triphosphatase and Mg2+-dependent adenosine triphosphatase activities of control hamster liver plasma membranes exhibited two break points at around 25 and 13 degrees C, whereas Arrhenius plots of their activities in hibernating hamster liver plasma membranes exhibited two break points at around 25 and 4 degrees C. 2. A single break occurring between 25 and 26 degrees C was observed in Arrhenius plots of the activities of fluoride-stimulated adenylate cyclase, basal adenylate cyclase and cyclic AMP phosphodiesterase of liver plasma membranes from both control and hibernating animals. 3. Arrhenius plots of phosphodiesterase I activity showed a single break at 13 degrees C for membranes from control animals, and a single break at around 4 degrees C for liver plasma membranes from hibernating animals. 4. The temperature at which break points occurred in Arrhenius plots of glucagon- and fluoride-stimulated adenylate cyclase activity were decreased by about 7--8 degrees C by addition of 40 mm-benzyl alcohol to the assays. 5. Discontinuities in the Arrhenius plots of 4-anilinonaphthalene-1-sulphonic acid fluorescence occurred at around 24 and 13 degrees C for liver plasma membranes from control animals, and at around 25 and 4 degrees C for membranes from hibernating animals. 6. We suggest that in hamster liver plasma membranes from control animals a lipid phase separation occurs at around 25 degrees C in the inner half of the bilayer and at around 13 degrees C in the outer half of the bilayer. On hibernation a change in bilayer asymmetry occurs, which is expressed by a decrease in the temperature at which the lipid phase separation occurs in the outer half of the bilayer to around 4 degrees C. The assumption made is that enzymes expressing both lipid phase separations penetrate both halves of the bilayer, whereas those experiencing a single break penetrate one half of the bilayer only.     

SP-B and SP-C alter diffusion in bilayers of pulmonary surfactant

The hydrophobic proteins SP-B and SP-C promote rapid adsorption of pulmonary surfactant to an air/water interface by an unknown mechanism. We tested the hypothesis that these proteins accelerate adsorption by disrupting the structure of the lipid bilayer, either by a generalized increase in fluidity or by a focal induction of interfacial boundaries within the bilayer. We used fluorescence recovery after photobleaching to measure diffusion of nitrobenzoxadiazolyl-dimyristoyl-phosphatidylethanolamine between 11 and 54 degrees C in multilayers containing the complete set of lipids and proteins in calf lung surfactant extract (CLSE), or the complete set of neutral and phospholipids without the proteins. Above 35 degrees C, Arrhenius plots of diffusion were parallel for CLSE and neutral and phospholipids, but shifted to lower values for CLSE, suggesting that the proteins rigidify the lipid bilayer rather than producing the proposed increase in membrane fluidity. The slopes of the Arrhenius plots for CLSE were steeper below 35 degrees C, suggesting that the proteins induce phase separation at that temperature. The mobile fraction fell below 27 degrees C, consistent with a percolation threshold of coexisting gel and liquid-crystal phases. The induction of lateral phase separation in CLSE, however, does not correlate with apparent changes in adsorption kinetics at this temperature. Our results suggest that SP-B and SP-C accelerate adsorption through a mechanism other than the disruption of surfactant bilayers, possibly by stabilizing a high-energy, highly curved adsorption intermediate.     

Rheological properties of barley β-glucan

Health benefits of cereal β-glucan are linked to its high viscosity. Although viscosity of β-glucan gum solutions has been reported previously, there are conflicting reports about its behavior at elevated temperatures. Therefore, the viscosity behavior of barley β-glucan gum obtained in a pilot plant (PP) or in a laboratory (LAB) was determined at different shear rates (1.29–129 s⁻¹) and temperatures (0.1–75 °C) in this study. Viscosity decrease with temperature was demonstrated for both gums and activation energy E_a was calculated from the Arrhenius equation. None of the fresh gum solutions exhibited thixotropic behavior at ≤1% (w/w) concentration, but the measurement demonstrated that increased shear rate is not applicable to polymer solutions of low viscosity. Information about rheological properties of β-glucan will lead to better understanding of its behavior under physiological and processing conditions.     

Time-temperature relationships for L1A2 cells step-down heated from 38 to 45 degrees C in vitro

The in vitro response of L1A2 cells to a single exposure to one temperature and to step-down heating was investigated. Single heating consisted of heating for a specified time at a constant temperature in the range 38.0-45.0 degrees C, whereas step-down heating involved a pretreatment of either 45.0 degrees C for 10 min or 42.0 degrees C for 90 min. The pretreatments were adjusted to give the same survival level. The survival curves for single heating had an initial shoulder followed by an exponential region, whereas for step-down heating they were strictly exponential and had no shoulder. The time-temperature relationship for cells exposed to single heating showed a biphasic Arrhenius curve with a downward inflection at 40.5 degrees C. Biphasic Arrhenius curves were also observed for step-down heating, but both the 45 degrees C/10 min and the 42 degrees C/90 min pretreatment showed an upward inflection that broke at 42.5 degrees C and 40.5 degrees C, respectively. The downward inflection on the Arrhenius curve for single heating has been attributed to thermotolerance development and the effect of step-down heating to a temporary inhibition of thermotolerance development. However, the present shape of the Arrhenius curves for step-down heating cannot be explained by inhibition of thermotolerance. It is therefore reasonable to assume that step-down heating is more than just the inhibition of thermotolerance, and that step-down heating and thermotolerance are distinct phenomena which act independently.     

Temperature effect of cholesterol association with synaptosomal plasma membranes of rabbit brain.

Association of exogenous cholesterol with rabbit brain synaptosomal plasma membranes follows an exponential path described by the general formula y = a X ebx. The co-operative nature of this association was shown when increasing amounts of unlabelled cholesterol glucoside (up to 0.5 mM) were added to a fixed amount (5 microM) of [14C]cholesterol, when a biphasic curve of the binding of [14C]cholesterol into the membranes was obtained. Arrhenius plots of this association revealed two break points which occur at 25 degrees C and 42 degrees C. The first break apparently corresponds to the transition from the crystalline to the gel phase. The second break may be due to the (continuously) increasing entropy of the system which creates at a certain point difficulties in the binding of cholesterol into the lipid bilayer.     

Effects of temperature on cytochrome oxidase activity in solubilized form and in lipid vesicle systems.

Isolated mammalian cytochrome oxidase gave an Arrhenius plot with a break (Tb) at about 20 degrees C when assayed in a medium containing Emasol. The activation energies above and below 20 degrees C were 9.3 (EH) and 18.9 kcal/mol (EL), respectively. Isolated cytochrome oxidase was also incorporated into vesicles of dipalmitoyl phosphatidylcholine (DPPC, phase transition temperature Tt = 40 degrees C), dimyristoyl phosphatidylcholine (DMPC, Tt = 23 degrees C) and dioleoyl phosphatidylcholine (DOPC, Tt = -22 degrees C). The DPPC system showed a nearly linear Arrhenius plot between 9 and 36 degrees C with E = 22.8 kcal/mol. When cytochrome oxidase was resolubilized from the DPPC vesicles and assayed in solution a biphasic plot was obtained again. Cytochrome oxidase-DOPC was more active than the solubilized enzyme and exhibited a biphasic Arrhenius plot with Tb = 23 degrees C. EH and EL were 6.6 and 15.8 kcal/mol, respectively. The plot for the oxidase-DMPC also showed a break (Tb = 26 degrees C) with EH = 6.6 and EL = 26.6 kcal/mol. These results indicate that the break in the Arrhenius plot reflects primarily a structural transition in the cytochrome oxidase molecule between the "hot" and "cold" conformations, as proposed previously. This transition, as well as the molecular state of cytochrome oxidase, is affected by the physical state of the membrane lipids as reflected by changes in the kinetic properties.     

Features of temperature dependence of the Na+,K+-ATPase reaction in normal and tumorous brain tissue

It has been shown that in the enzyme preparations (EP) from normal brain tissue (NBT) a typical break on the Arrhenius plot appeared at 20-22 degrees C, nH for Na+ and K+ exceeding 1.7 and 1.4, respectively. In EP from tumoural brain tissue (TBT) no break on the Arrhenius plot at 20-22 degrees C was revealed, but it appeared at 27.5 + 30.5 degrees C. The nH for Na+ with Na+,K+-ATPase from TBT was only 0.9, but the cooperative binding of K+ was preserved (nH = 1.3). Electrophoregrams (EP) from TBT showed additional protein bands. The urea and digitonin treatment of EP from NBT induced a break on the Arrhenius plot at 27.5-30.5 degrees C. It is suggested that the break at 27.5-30.5 degrees C is, probably, accompanied by local changes in the conformation of protein components of the enzyme.     

Hepatic plasma membranes from genetically obese (ob/ob) mice: studies on fluorescence polarization, phospholipid composition and 5'-nucleotidase activity

Hepatic plasma membrane lipids of lean (+/?) and obese (ob/ob) mice have been investigated using 1,6-diphenylhexatriene (DPH). Arrhenius plots of DPH fluorescence polarization in membranes showed the breakpoint in obese mice was reduced from 21 to 15 degrees C, whereas the breakpoint of 5'-nucleotidase activity was raised from 23 to 32 degrees C. Arrhenius break temperatures of DPH polarization and 5'-nucleotidase activity responded differently to housing mice at 34 degrees C and triiodothyronine (T3) treatment. Studies of DPH polarization in liposomes and phospholipid fatty acid composition suggested that differences in sphingomyelin acyl composition determine Arrhenius characteristics of hepatic 5'-nucleotidase in lean and obese mice.