Melting point equations for the ternary system water/sodium chloride/ethylene glycol revisited

Partial phase diagrams are of considerable utility in the development of optimized cryobiological procedures. Recent theoretical predictions of the melting points of ternary solutions of interest to cryobiology have caused us to re-examine measurements that our group made for the ethylene-glycol–sodium chloride–water phase diagram. Here we revisit our previous experiments by measuring melting points at five ethylene-glycol to sodium chloride ratios (R values; R = 5, 10, 15, 30, and 45) and five levels of concentration for each ratio. Melting points were averaged from three measurements and plotted as a function of total solute concentration for each R value studied. The new measurements differed from our original experimental values and agreed with predicted values from both theoretical models. Additionally, the data were fit to the polynomial described in our previous report and the resulting equation was obtained:T_m=(38.3-2.145×10^-1R)w+(81.19-2.909×10^-1R)w²,where w is the total solute mass fraction. This new equation provided good fits to the experimental data as well as published values and relates the determined polynomial constants to the R value of the corresponding isopleths of the three dimensional phase diagram, allowing the liquidus curve for any R value to be obtained.     

Electric-field orientation of sodium poly(l-glutamate) in methanol/water and ethylene glycol/water mixtures

Transient electric birefrinqence and circular dichroism measurements have been made on sodium poly(l-glutamate) in methanol/waer and ethylene glycol/water mixtures of various compositions. The specific Kerr constant increased upon the transition from coil to helix, but decreased with further increase in methanol or ethylene glycol content on the helix side.     

Simplified equations for the distribution of chloride in body water

According to the theory of Boyle and Conway, chloride leaves the extracellular fluid to enter cells, particularly muscle, when the plasma potassium concentrationK rises. Simplified equations are presented to describe in terms ofK the distribution of chloride expected when the quantity of the saltKp in the body fluids changes in health and disease.     

On the stability of the ripple phase in the DPPC/PLPC/water ternary system

The effect of incorporation of 1-palmitoyl-sn-glycero-3-phosphocholine (PLPC) on the structure of the P_β′ ripple mesophase in aqueous dispersions of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) has been studied by differential scanning calorimetry (DSC) and scanning dilatometry (SD). For samples containing 34 wt. % ²H₂O and 0–15 wt. % PLPC, a pretransition was observed by DSC. The pretransition disappears at 15 wt. % PLPC. The behavior of thermodynamic functions at the pretransition and main transition gives new insights on the structural changes produced by PLPC on bilayers of DPPC.     

Interrelation of ethylene glycol,urea and water transport in the red cell

The reflection coefficient, σ_j, which measures the coupling between the jth solute and water transport across a semipermeable membrane, varies between 0 and 1.0. Values of σ_j significantly less than 1.0 provide irreversible thermodynamic proof that there is coupling between the transport of solute and solvent and thus that they share a common pathway. We have developed an improved method for measuring σ and have used it to determine that σ_{ethylene glycol} = 0.71 ± 0.03 and σ_urea = 0.65 ± 0.03, in agreement with many, but not all, previous determinations. Since both of these values are significantly lower than 1.0, they show that there is a common ethylene glycol/water pathway and a common urea/water pathway. Addition of first one and then two methyl groups to urea increases σ to 0.89 ± 0.04 for methylurea and 0.98 ± 0.4 for 1,3-dimethylurea, consistent with passage through an aqueous pore with a sharp cutoff in the 6–7 Å region.     

Phase diagram of the system sodium alginate/water: a model for biofilms

Sodium alginate is a polyelectrolyte consisting of the monomer units β-d-mannuronate and -l-guluronate. Mainly based on the theory of Khokhlow et al., the state diagram of the binary system alginate/water has been calculated using different sets of parameters like degree of ionization, degree of polymerization and interaction function. The calculations comprise miscibility gaps, liquidus curves, eutectic points and the behaviour at temperatures below the melting point of water. Also gel and swelling curves have been treated, where gels are physically crosslinked. The DSC diagram of a 0.5 by wt.% polymer sol shows a double melting peak, which is explained by a heterogeneity above 0 °C. The crystallization of water seems to concentrate the gelled system irreversibly.     

Membrane permeability of the human granulocyte to water,dimethyl sulfoxide,glycerol, propylene glycol and ethylene glycol

Granulocytes are currently transfused as soon as possible after collection because they rapidly deteriorate after being removed from the body. This short shelf life complicates the logistics of granulocyte collection, banking, and safety testing. Cryopreservation has the potential to significantly increase shelf life; however, cryopreservation of granulocytes has proven to be difficult. In this study, we investigate the membrane permeability properties of human granulocytes, with the ultimate goal of using membrane transport modeling to facilitate development of improved cryopreservation methods. We first measured the equilibrium volume of human granulocytes in a range of hypo- and hypertonic solutions and fit the resulting data using a Boyle-van’t Hoff model. This yielded an isotonic cell volume of 378 μm³ and an osmotically inactive volume of 165 μm³. To determine the permeability of the granulocyte membrane to water and cryoprotectant (CPA), cells were injected into well-mixed CPA solution while collecting volume measurements using a Coulter Counter. These experiments were performed at temperatures ranging from 4 to 37 °C for exposure to dimethyl sulfoxide, glycerol, ethylene glycol, and propylene glycol. The best-fit water permeability was similar in the presence of all of the CPAs, with an average value at 21 °C of 0.18 μm atm⁻¹ min⁻¹. The activation energy for water transport ranged from 41 to 61 kJ/mol. The CPA permeability at 21 °C was 6.4, 1.0, 8.4, and 4.0 μm/min for dimethyl sulfoxide, glycerol, ethylene glycol, and propylene glycol, respectively, and the activation energy for CPA transport ranged between 59 and 68 kJ/mol.     

Optical absorption spectra of azurin and stellacyanin in glycerol/water and ethylene glycol/water solutions in the temperature range 290-20 K

We have measured the optical absorption spectra of azurin and stellacyanin in the wavelength range 1100-350 nm and in the temperature interval 290-20 K. Samples are protein aqueous solutions containing 65% (v/v) glycerol or ethylene glycol as cryoprotectants and remain homogeneous and transparent throughout the whole temperature range investigated. Spectra are deconvoluted into Gaussian components and the temperature dependence of the zeroth, first and second moments of the various bands is analyzed, within the harmonic Franck-Condon approximation, to obtain information on the stereodynamic properties of the active sites of these proteins. Sizable differences of the integrated intensities of all the bands with temperature are observed and are attributed to variations of the metal-ligand relative positions (i.e., deformations of the active site) that occur as the temperature is lowered. The mean effective frequency of the nuclear vibrations coupled to all the observed bands is about 150 cm(-1) for both proteins in both solvents used; this indicates that the electronic transitions from which the optical spectrum originates are substantially coupled with low-frequency vibrational modes, likely ligand-metal-ligand deformations. The relevance of the stereodynamic properties of azurin and stellacyanin, investigated in this work, to their functional behavior is also suggested.     

One-pot synthesis in aqueous system for water-soluble chitosan-graft-poly(ethylene glycol) methyl ether

Chitosan is functionalized with poly(ethylene glycol) methyl ether (mPEG) at the amino and hydroxyl groups via a single step reaction in a homogeneous aqueous system. A chitosan aqueous solution obtained from the mixture of chitosan and hydroxybenzotriazole (HOBt) in water is a key factor in providing mild conditions to conjugate mPEG by using a carbodiimide conjugating agent. The reaction at ambient temperature for 24 h gives chitosan-g-mPEG with water solubility with mPEG content as high as 42%. This work demonstrates that a water-soluble chitosan-HOBt complex is an effective system for the preparation of chitosan derivatives via the aqueous system without the use of acids or organic solvents.     

Phase equilibria of the ternary system 1-palmitoyl-sn-glycero-3-phosphocholine/oleic acid/water/studied by NMR

Part of a phase diagram for the system 1-palmitoyl-sn-glycero-3-phosphocholine (PamGroPCho)/oleic acid/water has been constructed from mainly ³¹P-NMR data and a previous determination of the phase equilibria of the binary PamGroPCHo/water system. It was found that the appearance of the phase diagram is very similar to those found for several simple soap/fatty acid/water or soap/long-chain alcohol/water systems. The most striking features observed are: (1) the lamellar phase can swell towards very high water contents (2) vesicles are formed after sonication and (3) the cubic liquid crystalline phase disappears upon addition of very small amounts of oleic acid. The self-association of the amphiphiles and the shape of the aggregates are discussed in terms of existing first-order approximative theories.     

Phase equilibria of the ternary system 1-palmitoyl-sn-glycero-3-phosphocholine/oleic acid/water studied by NMR

Part of a phase diagram for the system 1-palmitoyl-sn-glycero-3-phosphocholine (PamGroPCho)/oleic acid/water has been constructed from mainly 31P-NMR data and a previous determination of the phase equilibria of the binary PamGroPCHo/water system. It was found that the appearance of the phase diagram is very similar to those found for several simple soap/fatty acid/water or soap/long-chain alcohol/water systems. The most striking features observed are: (1) the lamellar phase can swell towards very high water contents (2) vesicles are formed after sonication and (3) the cubic liquid crystalline phase disappears upon addition of very small amounts of oleic acid. The self-association of the amphiphiles and the shape of the aggregates are discussed in terms of existing first-order approximative theories.     

Analysis of the phase behavior of the aqueous poly(ethylene glycol)-Ficoll system

The PEG-Ficoll polymer phase system is one that has been overlooked in the past for biotechnology applications because of the stability of its emulsions. However, new applications, such as emulsion coating of cells, are appearing that rely on this very property. Ficoll is highly polydisperse and multimodal with three distinct Ficoll peaks in gel permeation chromatography. As a result, the transition between one-phase and two-phase systems is blurred and the binodials obtained through turbidometric titration and tie-line analysis differ significantly. Moreover, since the three Ficoll peaks partition differently, tie-line analysis cannot be described by a simple model of the aqueous two-phase system. A simple modification to the model allowed for excellent fit, and this modification may prove well-suited for the many practical cases where aqueous two-phase systems fail to display parallel tie-lines as implicitly assumed in the simpler model.     

Growth, water content, and solute accumulation of two tobacco cell lines cultured on sodium chloride, dextran, and polyethylene glycol

Simulated drought tolerance was compared for an NaCl-adapted and a nonadapted cell line of tobacco (Nicotiana tabacum var. Samsum) to determine the relationship of salt and drought tolerances. The osmotic adjustment and growth of these two lines was followed when cultured on solid media which contained isosmotic concentrations of NaCl, KCl, polyethylene glycol (PEG) or dextran. One line was adapted to growth on 130 millimolar NaCl, but the other was not.