Interaction of water vapour with twenty different poly-L-amino acids and their excess hydration in presence of sodium chloride

Using the isopiestic vapour pressure technique, the magnitudes of excess binding of water and NaCl per mole of twenty different poly-L-amino acid residues, respectively in the presence of different bulk molefractions (X2) of NaCl have been evaluated from the mathematical expressions for the Gibbs surface excesses. At certain high ranges of NaCl concentration, the plot of -Gamma1 (2) versus X1/X2 becomes linear, so that moles of water and NaCl, respectively bound per mole of amino acid residue can be evaluated. -Gamma(2)1 is the excess moles of H20 per mole of amino acid residue and X1 and X2 stand for mole fractions of the water and NaCl, respectively in the sample system. Also, using the integrated form of the Gibbs absorption equation, the values of standard free energy change (deltaG(0)) for the excess adsorption of NaCl per kg of poly-L-amino acids have been evaluated. These values are all positive as a result of positive excess hydration of polyamino acids. The standard free energy of excess hydration deltaG(0)hy (equal to -deltaG(0)) is negative due to spontaneous excess hydration of polyamino acid in the presence of a salt.     

Low temperature conversion of rice husks, eucalyptus sawdust and peach stones for the production of carbon-like adsorbent

In this study, the feasibility of preparing effective adsorbents from unmitigated agroforestry wastes was investigated. Three different kinds of carbon-like materials were produced by low temperature pyrolysis (LTC, <500 degrees C) of the raw materials rice husks, eucalyptus sawdust and peach stones. The carbon-like materials were characterized by instrumental methods (SEM,X-RDS,BET,MAS-RMN,FTIR), physico-chemical adsorption (iodine-, methylene blue- and phenazone-number; acetic acid adsorption isotherm; textile dyes- and carbohydrate adsorption), and heat value determination. The produced materials, which showed appreciable adsorption capacity, can be considered as precursors for the production of active coal or even be used directly as well.     

Effect of sorbed water on the thermal stability of soybean protein

A soybean protein isolate (SPI), and its beta-conglycinin and glycinin componets were obtained from defatted soybean flour by applying dissolution and precipitation based on the difference in their solubility depending on each isoelectric point. The purity evaluated by SDS-PAGE of the beta-conglycinin and glycinin preparations was about 84% and 80%, respectively, resulting in a clear difference in the pH dependence on solubility. A BET plot derived from the water sorption isotherm at 25 degrees C showed that the amount of the monolayer adsorption of these preparations was about 6-9%, the value for the beta-conglycinin preparation being about 1.5 times higher than that for the glycinin preparation. The beta-conglycinin and glycinin preparations were respectively denatured at around 75 degrees C and 86 degrees C in the presence of excess water, whereas the denaturation temperature of both preparations was markedly increased by decreasing sorbed water content below 40%, corresponding well with the unfrozen water content.     

Fasting metabolism and thermoregulatory competence of the star-nosed mole, Condylura cristata (Talpidae: Condylurinae).

Metabolic and body temperature (Tb) responses of star-nosed moles (Condylura cristata) exposed to air temperatures ranging from 0 to 33 degrees C were investigated. The thermoneutral zone of this semi-aquatic mole extended from 24.5 to 33 degrees C, over which its basal rate of metabolism averaged 2.25 ml O2 g-1 h-1 (45.16 J g-1 h-1). This rate of metabolism is higher than predicted for terrestrial forms, and substantially higher than for other moles examined to date. Minimum thermal conductance was nearly identical to that predicted for similar-sized eutherians and may represent a compromise between the need to dissipate heat while digging and foraging in subterranean burrows, and the need to conserve heat and avoid hypothermia during exposure to cold. C. cristata precisely regulated Tb (mean +/- SE = 37.7 +/- 0.05 degrees C) over the entire range of test temperatures. Over three separate 24-h periods, Tb of a radio-implanted mole varied from 36.6 to 38.8 degrees C, and generally tracked level of activity. No obvious circadian variation in Tb and activity was apparent, although cyclic 2-4 h intervals of activity punctuated by periods of inactivity lasting 3-5 h were routinely observed. We suggest that the elevated basal metabolic rate and relatively high Tb of star-nosed moles may reflect the semi-aquatic habits of this unique talpid.     

Reaction mechanism of succinyl CoA synthetase from pigeon thoracic muscle

The ability of succinyl-CoA-synthetase from pigeon thoracic muscle to interact with ATP is investigated. gamma-32P-ATP and 8-14C-ATP were used in experiments. It is found that the enzyme, when reacting with ATP in the presence of Mg2+, forms a complex containing 2 moles of ATP residue and 2 moles of phosphoric acid residue (splitted from ATP) per 1 mole of protein. After 2 hours of incubation at 0-4 degrees C, the complex is converted into another one, containing 4 residues of phosphoric acid per 1 mole of @protein. Both complexes are active, and their incubation with succinate and CoA results in the formation of succinyl-CoA. The reaction capacity of these enzyme complexes with some reaction substrates is investigated. The enzyme complex containing 2 phosphoric acid residues and 2 nucleotide residues is found to interact neither with CoA, nor with succinate. The enzyme complex containing 4 phosphoric acid residues does not react with CoA, but it interacts with 14C-succinate, releasing inorganic phosphate in the amount equivalent to the equimolar amount of protein-binding succinic acid.     

Permeability and integrity properties of lecithin-sphingomyelin liposomes.

The properties of multibilayered liposomes formed from mixtures of sphingomyelin and phosphatidylcholine in varying mole ratio (all containing one mole dicetylphosphate per 10 moles of phospholipids) have been studied. The principal findings are: (1) Over the range 0 to 1 mole fraction sphingomyelin the liposomes exhibit multibilayer structure as visualized by electron microscopy using negative staining. (2) The two phospholipids differ in their interaction with dicetylphosphate in a bilayer structure. In mixtures of the two the effect of sphingomyelin is dominant. (3) The ability of sphingomyelin to form osmotically active liposomes depends on its fatty acid's composition. (4) Liposomes of all mole fractions of sphingomyelin are osmotically active if the C24: 1 fatty acid content of sphingomyelin exceeds 10% of the total acyl residues. The degree of osmotic activity, however, depends upon the molar ratio between the two phospholipids. The highest initial rate of water permeability was found for lecithin liposomes. The maximal change of volume by osmotic gradients was obtained for liposomes composed of 1:1 lecithin to sphingomyelin (mole ratio). (5) Permeability to glucose increased with increasing lecithin mole fraction. (6) Liposomes composed of 1:1 lecithin to sphingomyelin have the largest aqueous volume per mole of phospholipid as measured by glucose trapping. (7) The osmotic fragility of liposomes made of sphingomyelin is higher than for those made of lecithin but the highest osmotic fragility was obtained for liposomes containing lecithin and sphingomyelin in 1:1 molar ratio. (8) When the temperature is abruptly lowered to about 2 degrees C, lipsomes formed from phosphatidylcholine release about 20% of trapped glucose during a transient increase in permeability. Liposomes containing 0.5 mole fraction sphingomyelin release about 30% of the trapped glucose under these conditions. Liposomes composed of sphingomyelin alone do not exhibit this phenomenon.     

Effect of phenylmercury derivatives on human oxyhemoglobin

By the dynamics of human oxyhemoglobin coagulation in the presence of phenyl mercury acetate in tris-AcOH buffer, pH 7.2 the number of moles of PhHg+ stechiometrically bound with protein at different temperatures was estimated. Within the temperature range 15-30 degrees C this value is constant--32-34 mole per 1 mole of HBO2-tetramer. Within the range 30-40 degrees C it rises to approximately 40. Coagulation of oxyhemoglobin modified with PhHg+ cation is reversible in contrast to HBO2 coagulation modified with uncharged PhHgCl.     

Adsorption kinetics of azinphosmethyl from aqueous solution onto pyrolyzed Horseshoe sea crab shell from the Atlantic Ocean

The adsorption behavior of azinphosmethyl on pyrolyzed Horseshoe Crab (Limulus polyphemus) outer shell, as a residue, from the Atlantic Ocean, collected along the Maine coast, USA, has been studied with regards to its kinetic and equilibrium conditions, taking into account adsorbate concentrations of 2 x 10(-3), 4 x 10(-3), 6 x 10(-3), and 8 x 10(-3), as well as temperatures of 30 degrees C, 40 degrees C, 50 degrees C, and 60 degrees C. The yield of adsorption of azinphosmethyl from aqueous solution ranged from 56.1% to 61% with temperature increasing. Kinetic studies showed that adsorption rate decreased as the initial azinphosmethyl concentration increased. It was found, that the adsorption reaction obeyed first-order kinetics. The overall rate constants were estimated for different temperatures. The activation energy for adsorption was about 1.52 kJmol(-1), which implies that azinphosmethyl mainly adsorbed physically onto Horseshoe Crab outer shell. Langmuir and Freundlich isotherms were applied to the experimental data and isotherm constants were calculated. The thermodynamic parameters DeltaG0, DeltaH0 and DeltaS0 for the adsorption reaction were evaluated based on equilibrium data and in connection with this result the thermodynamic aspects of adsorption reaction were discussed. The adsorption was found to be endothermic in nature. The adsorbent used in this study proved highly efficient for the removal of azinphosmethyl.     

The equilibrium constants and enthalpy changes for the esterification of glycine by ethanol in water and ethanol- water mixtures

Equilibrium constants, defined on the basis of the moles of all reactants and products including water, were found to be 4.6, 1.0 and 0.8 for the esterification of the glycinc cation at 20 degrees in a dilute aqueous sytem, and systems having 0.5 : 1 and 1 : 1 molar ratios of ethanol to water, respectively. When corrections were made for deviations from ideality a value of 5 +/- 1 was obtained for all three systems. Enthalpy changes were determined calorimetrically for the dilute aqueous and equimolar ethanol-water systems, and in each case was close to 1 kcal mole(-). The entropy change was calculated as 6 cal mole(-1) deg(-1).DeltaG(0') for the hydrolysis of the glycine ethyl ester cation at 20 degrees and pH 7 was calculated as -7.5 kcal mole(-1).     

Physicochemical factors affecting ethanol adsorption by activated carbon

Powder and granular activated charcoal were evaluated for ethanol adsorptivity from aqueous mixtures using an adsorption isotherm. Ethanol adsorption capacity was more pronounced at 25 degrees C as compared to 5, 15, and 40 degrees C. When pH of the ethanol-buffer mixture (0.09 ionic strength) was changed from acidic (2.3) to neutral and then to alkaline (11.2), ethanol adsorption was decreased. Increasing ionic strength of the ethanol-buffer mixtures from 0.05 to 0.09 enhanced ethanol adsorption but a further increase to 0.14 showed no significant effect. Ethanol adsorption was more efficient from an aqueous ethanol mixture as compared to semidefined and nondefined fermentation worts, respectively. Heating granular charcoal to 400 degrees C for 1 h and 600 degrees C for 3 h in N(2) increased ethanol adsorptivity and heating to 1000 degrees C (1 h) in CO(2) decreased it when ethanol was removed from dilute solutions by simple pass adsorption in a carbon packed column. Granular charcoal was superior to powdered charcoal and an inverse relationship was noted between the weight of the granular carbon bed in the column and ethanol adsorbed/g carbon. Decreasing the column feed flow rate from 7.5 to 2.0 L aqueous ethanol/min increased the adsorption rate.     

Activated carbons from waste biomass by sulfuric acid activation and their use on methylene blue adsorption

Preparation of the activated carbons from sunflower oil cake by sulphuric acid activation with different impregnation ratios was carried out. Laboratory prepared activated carbons were used as adsorbents for the removal of methylene blue (MB) from aqueous solutions. Liquid-phase adsorption experiments were conducted and the maximum adsorption capacity of each activated carbon was determined. The effects of various process parameters i.e., temperature, pH, initial methylene blue concentration, contact time on the adsorption capacity of each activated carbon were investigated. The kinetic models for MB adsorption onto the activated carbons were studied. Langmuir isotherm showed better fit than Freundlich isotherm for all activated carbon samples. The rates of adsorption were found to conform to the pseudo-second-order kinetics with good correlation. The separation factor (R(L)) revealed the favorable nature of the isotherm of the MB activated carbon system.     

Adsorption of methylene blue from aqueous solution on pyrolyzed petrified sediment

The adsorption kinetics of methylene blue on pyrolyzed petrified sediment (PPS) has been performed using a batch-adsorption technique. The effects of various experimental parameters, such as initial dye concentration, contact time, and temperature were investigated. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data. The best correlation coefficient was obtained using the pseudo first-order kinetic model, which shows that the adsorption of methylene blue followed the pseudo-first-order rate expression and the rate constants were evaluated. The Langmuir and Freundlich adsorption isotherm models were applied to describe the equilibrium isotherms and the isotherm constants were determined. It was found that the data fitted well to Langmuir and Freundlich models. The activation energy of adsorption was also evaluated for the adsorption of methylene blue onto pyrolyzed sediment. It was found about 8.5 kJ mol(-1). Thermodynamics parameters DeltaG(o), DeltaH(o), DeltaS(o) were calculated, indicating that this process can be spontaneous and endothermic. The adsorption enthalpy and entropy were found as 14-18.5 kJ mol(-1) and 52.8-67 J mol(-1) K(-1), respectively. The results obtained from the adsorption process using PPS as adsorbent was subjected to student's t-test.     

Determination of refractive index increment ratios for protein-nucleic acid complexes by surface plasmon resonance

Three nucleic acid-protein complexes of 1:1 stoichiometry were analyzed by surface plasmon resonance on a Biacore biosensor to test whether or not proteins and nucleic acids yielded similar refractive index increments on binding. The expected maximum response in resonance units, (RU(exp))(max), and the observed one, (RU(obs))(max), on saturation of immobilized targets by interacting partners were compared to determine the ratio of (deltan/deltaC)(protein) to (deltan/deltaC)(nucleic acid), where n is the refractive index at the surface and C is the concentration of one partner. Our results suggest that proteins and nucleic acids behave similarly and that the discrepancy between the expected and observed maximum responses for such complexes reflects inaccurate evaluation of the binding responses. Therefore, no correction of the instrument response is required for protein and nucleic acid interaction studies on a Biacore biosensor.     

Separation of chlorogenic acid from honeysuckle crude extracts by macroporous resins

Chlorogenic acid, one of the most bioactive compounds rich in the Chinese medicinal herb honeysuckle, is a natural antioxidant and serves as anti-inflammatory, anti-tumor, anti-mutagenic and anti-carcinogenic agent. An efficient preparative separation process of chlorogenic acid from honeysuckle crude extracts has been developed in the present study. HPD-850 resin offers the best adsorption capacity, and adsorption and desorption ratios for chlorogenic acid among the nine macroporous resins tested, and its adsorption rate at 25 degrees C fit best to the Langmuir isotherm. The adsorption capacity of HPD-850 resin was found to depend strongly on the pH value of the initial adsorption solution. The dynamic adsorption and desorption experiments have been carried out on a HPD-850 resin packed column to optimize the separation process of chlorogenic acid from honeysuckle crude extracts. After one run treatment with HPD-850 resin, the chlorogenic acid content in the final product was increased 4.46-fold from 11.2% to 50.0%, with a recovery yield of 87.9%. The preparative separation of chlorogenic acid can be easily and efficiently achieved via adsorption and desorption on HPD-850 resin, and the method developed will provide a potential approach for large-scale separation and purification of chlorogenic acid for its wide pharmaceutical use.     

The binding of deoxyguanosine to polycytidylic acid: an application of the thermodynamic model of monomer-polymer complex formation.

The thermodynamic model (equation 1) for formation of monomer-polymer complexes developed for better interpretation of the sigmoidal isotherms for the binding of adenosine to polyuridylic acid (2) and chemically modified polyuridylic acids (3) has been successfully applied to reproduce the isotherms for both the duplex binding of deoxyguanosine (d-G) to polycytidylic acid (at pH 6.8) and the triplex binding at pH 4.1. The value for the equilibrium constant, K, of the triplex complex (per unit of C-G-C) is ～2000 at the optimum value of n = 5 (n is the number of d-G units in the smallest complex that can form). The value of K for the duplex complex is 555 and the optimum value of n is 4.The value of ΔG for the triple helical complex is 4.15 kcal/mole, the value of w (the stacking free energy of the d-G units in the complex) is 2.05 kcal/mole. For the double helical complex at pH 6.8, ΔG° is 3.45 kcal/mole, w = 1.55 kcal/mole.It is also shown that equation (1) predicts that the shape and mid-point slope (i.e., w) of a binding isotherm depends only on the value of n; and thus the isotherms for rA-poly U (n = 5) and dG-poly C (n = 5) have the same mid-point slopes, and thus the same values of w. The difference between ΔG° and w is taken as a relative measure of the free energy of hydrogen bonding; values are calculated for the rA-poly U, the dG-poly C triple helix, and the dG-poly C double helical complexes.     

Thermodynamics of statherin adsorption onto hydroxyapatite

Statherin is a salivary protein that inhibits the nucleation and growth of hydroxyapatite crystals in the supersaturated environment of the oral cavity. The thermodynamics of adsorption of statherin onto hydroxyapatite crystals have been characterized here by isothermal titration calorimetry and equilibrium adsorption isotherm analysis. At 25 degrees C, statherin adsorption is characterized by an exothermic enthalpy of approximately 3 kcal/mol that diminishes to zero at approximately 25% surface coverage. The initial heat of statherin adsorption increases with temperature, displaying a positive heat capacity change of 194 +/- 7 cal K(-)(1) mol(-)(1) at 25 degrees C. The heat of adsorption during this initial phase is strongly dependent on the buffer species, and from the differential heats of buffer ionization, it can be calculated that approximately one proton is taken up by the crystal or protein upon adsorption. The free energy of adsorption is dominated at all coverages by a large positive entropy (>or=23 cal K(-)(1) mol(-)(1)), which may be partially due to the loss of organized water that hydrates the protein and the mineral surface prior to adsorption. These results are interpreted using a two-site model for adsorption of statherin onto the hydroxyapatite crystals.     

Effect of Sorbed Water on the Thermal Stability of Soybean Protein

A soybean protein isolate (SPI), and its β-conglycinin and glycinin componets were obtained from defatted soybean flour by applying dissolution and precipitation based on the difference in their solubility depending on each isoelectric point. The purity evaluated by SDS–PAGE of the β-conglycinin and glycinin preparations was about 84% and 80%, respectively, resulting in a clear difference in the pH dependence on solubility. A BET plot derived from the water sorption isotherm at 25 °C showed that the amount of the monolayer adsorption of these preparations was about 6–9%, the value for the β-conglycinin preparation being about 1.5 times higher than that for the glycinin preparation. The β-conglycinin and glycinin preparations were respectively denatured at around 75 °C and 86 °C in the presence of excess water, whereas the denaturation temperature of both preparations was markedly increased by decreasing sorbed water content below 40%, corresponding well with the unfrozen water content.     

Adsorption of cationic dye from aqueous solutions by date pits: Equilibrium,kinetic, thermodynamic studies,and batch adsorber design

The retention profile of methylene blue from aqueous solutions onto the solid adsorbent date pits has been investigated in a batch system. The characterization and adsorption efficiency for methylene blue was evaluated using date pits. Fourier Transform Infra-Red, Scanning Electron Microscope, Brunauer–Emmett–Teller analysis were performed to determine the characteristics of the material. The effect of contact time, initial dye concentration, adsorbent dosage, temperature, and solution pH were investigated. The adsorption was found to increase with increasing time, decreasing concentration of dye, decreasing temperature and increasing dosage up to equilibrium values which was 20 min, 25°C, and 0.1 g adsorbent, respectively. The adsorption was favorable at high and low pH (pH 3, pH 7). The adsorption equilibrium data were best fitted by Freundlich isotherm. The adsorption kinetics was found to follow the pseudo second order kinetic model. Thermodynamic parameters such as free energy, enthalpy, and entropy were calculated and found to be ?4.6 kJ/mole, ?7.9 kJ/mole, and ?11.8 kJ/mole, respectively. The thermodynamic parameters of the uptake of methylene blue onto the date pits indicated that, the process is exothermic and proceeds spontaneously at low temperature. A single stage batch adsorber was designed for adsorption of methylene blue by Date Pits based on optimum isotherm.     

Domains and anomalous adsorption isotherms of dipalmitoylphosphatidylcholine membranes and lipophilic ions: pentachlorophenolate, tetraphenylborate, and dipicrylamine.

Dipalmitoylphosphatidylcholine (DPPC) vesicles acquire negative surface charge on adsorption of negatively charged pentachlorophenolate (PCP-), and lipophilic ions tetraphenylborate (TPhB-), and dipicrylamine (DPA-). We have obtained (a) zeta-potential isotherms from the measurements of electrophoretic mobility of DPPC vesicles as a function of concentration of the adsorbing ions at different temperatures (25-42 degrees C), and (b) studied the effect of PCP- on gel-to-fluid phase transition by measuring the temperature dependence of zeta-potential at different PCP- concentrations. The zeta-potential isotherms of PCP- at 25, 32, and 34 degrees C correspond to adsorption to membrane in its gel phase. At 42 degrees C the zeta-potential isotherm corresponds to membrane in its fluid phase. These isotherms are well described by a Langmuir-Stern-Grahame adsorption model proposed by McLaughlin and Harary (1977. Biochemistry. 15:1941-1948). The zeta-potential isotherm at 37 degrees C does not follow the single-phase adsorption model. We have also observed anomalous adsorption isotherms for lipophilic ions TPhB- and DPA- at temperatures as low as 25 degrees C. These isotherms demonstrate a gel-to-fluid phase transition driven by ion adsorption to DPPC membrane during which the membrane changes from weakly to a strongly adsorbing state. The anomalous isotherm of PCP- and the temperature dependence of zeta-potential can be described by a two-phase model based on the combination of (a) Langmuir-Stern-Grahame model for each phase, (b) the coexistence of gel and fluid domains, and (c) depression of gel-to-fluid phase transition temperature by PCP-. Within the anomalous region the magnitude of zeta-potential rapidly increases concentration of adsorbing species, which was characterized in terms of a Esin-Markov coefficient. This effect can be exploited in membrane-based devices. Comments are also made on the possible effect of PCP, as an uncoupler, in energy transducing membranes.