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Emulsification of lauric acid in an aqueous ethanol solution including lauric acid solute has been observed during cooling before crystallization of lauric acid occurs. The nature of two different solubility curves was explained for the system of lauric acid and aqueous ethanol solution. The mutual solubility of the two liquid phases controls emulsification; the solid solubility of lauric acid controls crystallization. The mutual solubility curve appears at relatively high temperature, and the solid solubility curve at relatively low temperature. Crystallization essentially generates a solid metastable zone under the solid solubility curve. A supersaturated solution can be obtained in the metastable zone. However, no nucleation occurs in the metastable zone. The metastable zone, therefore, still caused emulsification at low temperature before crystallization of lauric acid occurred. The hypothetical mutual solubility curve for the aqueous solution including hydrophobic solutes appeared invariably even at low temperature in the metastable zone under the solid solubility. Copyright 2001 Academic Press.
Phospholipid vesicles prepared by the freeze-thaw extrusion method contain internal solute concentrations which are much higher than the external values (entrapment ratios much greater than 1). This concentrating effect is a complex function of the total impermeant solute concentration in the medium used to prepare vesicles, the presence or absence of permeant solutes in the medium and the apparent competitive binding interactions between solutes and phospholipid. Increases in water phase solute concentration during freezing are thought to underlie the concentrating phenomenon, while osmotic pressure driven lysis of vesicles during thawing appears to limit its magnitude. By judicious selection of solute concentration and physical properties, further increases in the entrapment ratio should be obtainable, improving the usefulness of these vesicles as drug delivery vesicles and experimental systems.
BACKGROUND: Endothelium plays a key role in graft patency. My colleagues and I have developed a verapamil+nitroglycerin solution (balanced to pH 7.4) to prepare the radial artery without mechanical distention or dilation and have reported the efficacy of its antispastic action. This study was designed to investigate whether using this solution as part of the University of Hong Kong protocol to prepare the radial artery is more efficacious than papaverine solution in preserving endothelial function. METHODS: Ring segments of the radial artery taken from 25 patients undergoing coronary artery bypass grafting were studied in organ chambers. The endothelium-dependent relaxation, as the index of endothelial function, was examined by two mechanisms-receptor-mediated relaxation (by acetylcholine) and non-receptor-mediated relaxation (by calcium ionophore A23187) in U46619-induced contraction (10 nmol/L). RESULTS: In the relaxation induced by either acetylcholine (27.3% +/- 5.0% [n = 7] vs 23.9% +/- 3.9% [n = 6],p = 0.6) or A23187 (62.9% +/- 6.0% [n = 13] vs 62.3% +/- 8.4% [n = 6],p = 0.96), there was no significant difference between the control radial arteries and those treated with the verapamil+nitroglycerin solution. In the papaverine-treated rings, acetylcholine-mediated relaxation was abolished (3.3% +/- 2.6% vs 23.9% +/- 3.9%,p < 0.001) and A23187-mediated relaxation was significantly reduced (39.7% +/- 5.2% vs 62.3% +/- 8.4%, p = 0.02) compared with verapamil+nitroglycerin treatment. CONCLUSION: Use of verapamil+nitroglycerin solution to prepare the radial artery maximally preserves endothelial function. In contrast, papaverine impairs this function. Verapamil+nitroglycerin solution may be effectively and safely used to prepare the radial artery for coronary artery bypass grafting.
Electrospray ionization (ESI) is a soft ionization technique that is able to transfer intact ions, as well as solution phase non-covalent complexes into the gas phase. With small molecules that have a high tendency to form hydrogen bonds, the observation of non-covalent complexes by ESI-MS can be the result of a non-specific interaction, due to the nature of the electrospray process. Special precautions and additional steps should be performed to identify the origin of the complexes observed with ESI-MS, and we have utilized solution phase hydrogen/deuterium (H/D) exchange as a method to determine the specificity of the complexes. By comparing the average number of exchanges for the monomer subunits to the average number of exchanges for the complex, one can distinguish if a specific complex is formed in solution. In this paper we have investigated non-covalent complexes of some common chemotherapy agents: paclitaxel, doxorubicin, and etoposide by ESI-MS. By using the solution phase H/D exchange, we were able to identify several specific drug-drug complexes. Thus, solution phase H/D exchange combined with ESI-MS provides for a convenient method in ascertaining the specificity of non-covalent complexes as being formed in solution or in vacuo.
Spectroscopic and voltammetric features for the solution and solution-cast film of polyaniline (PANI) colloids prepared in the absence and presence of ultrasonic irradiation were examined. Significant differences in the color and absorption spectra between the solution of colloids prepared in the absence and presence of irradiation were observed. Effects of ambient atmosphere on the solution of colloids were also studied. A gradual decay in the absorption at approximately 365 nm was occurred upon ageing the solution in air for the colloid prepared under ultrasonic irradiation. PANI film, cast from its colloidal solution, exhibited excellent electroactivity. The films thus cast were applied to electrode modification to control electrochemical reaction. Clear voltammetric response was observed on the electrode modified with the colloid prepared in the presence of ultrasonic irradiation.
The conformations of enzyme inhibitors in solution and bound to the enzyme thermolysin are investigated as a convenient model for understanding the relationship between the conformation of drugs in solution and at the receptor. The solution conformations of carbobenzoxy-L-phenylalanine (I) and beta-phenylpropionyl-L-phenylalanine (II) are determined using nuclear magnetic resonance spectroscopy. These studies show that I and II have essentially the same conformation about both the alpha-beta bond and the C alpha-N bond in Me2SO-d6, acetone-d6, methanol-d4, chloroform-d, and D2O. In addition, the conformations of I and II are similar to phenylalanine and other phenylalanine derivatives. Comparison of the lowest energy solution conformer to that bound by the enzyme thermolysin shows that the lowest energy conformer (in solution) of carbobenzoxy-L-phenylalanine is bound by thermolysin; on the other hand, it is the highest energy conformer (in solution) of beta-phenylpropionyl-L-phenylalanine which is bound to the enzyme. This, to our knowledge, is one of the first experimental conformations of the hypothesis that an enzyme does not always bind the lowest energy conformer of an inhibitor.
The semi-ideal solution theory has been presented to describe the changes in thermodynamic properties accompanying the process of mixing the nonideal electrolyte solutions M(i)X(i)-(NY)sat-H2O (i = 1 and 2) at constant activities of NY and H2O, including concentration, chemical potential, activities of all M(i)X(i), Gibbs free energy, enthalpy, entropy, thermal properties, and volumetric properties. The theory states that, under the conditions of equal activities of NY and H2O, the average hydration numbers characterizing the ion-solvent interactions have the same values in the mixture as in the subsystems and the process of mixing these nonideal electrolyte solutions is as simple as that of mixing the ideal solutions if the contributions from the ion-ion interactions to the solvent activity are assumed to be the same in the mixture as in its subsystems, which has been justified by the calculations of the Pitzer equation. Therefore, a series of novel linear equations are established for the thermodynamic properties accompanying the process of mixing these nonideal solutions as well as mixing the ideal solutions M(i)X(i)-(NY)sat-H2O (i = 1 and 2) of equal mole fractions of NY and H2O. From these equations, the widely applied empirical Zdanovskii's rule is derived theoretically, and the important constant in the McKay-Perring equation under isopiestic equilibrium is determined theoretically, which has been substantiated by comparisons with the experimental results for 18 mixtures reported in the literature. Isopiestic measurements have been made for the systems BaCl2-LaCl3-H2O, NaCl-BaCl2-LaCl3-H2O, and NaCl-LaCl3-BaCl2.2H2O(sat)-H2O at 298.15 K. The results are used to test the novel linear concentration relations, and the agreement is excellent. The novel predictive equation for the activity coefficient of M(i)X(i) in M1X1-M2X2-(NY)sat-H2O has been compared with the calculations of the Pitzer equation, and the agreement is good.
This paper reports on investigations about the adsorption at the air-water surface, and for the sake of comparison at the silica-solution interface, of two 1-2 electrolytes, Pb(NO(3))(2) and PbCl(2), at first alone and then from a mixture with carbofuran or with benzene; all of them were at concentrations below 10(-2) M. The limited domain, where the Debye and Hückel formalism for solutions and the Wagner-Onsager-Samaras (WOS) model for surfaces are correct, is then respected. This study was aimed at trying to identify the part played in the surface by the different particles of the system components and in particular the role of water. When aqueous solutions of nonorganic salts are dilute enough, their surface tensions are known to be salt concentration-independent; however, the zero value of the resulting relative adsorption has never been the subject of analysis about water behavior. By combining experimental relative adsorptions and Gibbs excesses calculated from the WOS theory, we will show that, in well-known solutions such as KCl ones, where the negative excess in salt can be very precisely modeled by the WOS theory, the resulting water excess Gamma(W) is negative. The same result can be obtained by taking into account the Ray-Jones effect. This observation drove us to wonder about the results of a similar analysis done on solutions of unsymmetrical electrolytes and on mixtures of salt and organic molecules. Experiments showed that, for all of the systems, Gamma(W) was negative. For a given salt, Gamma(W) was more negative in the presence of organic molecules, and carbofuran was a more efficient water repellent than benzene; water repulsion was greater with nitrates than with chlorides. From these data, it seems that water was repelled toward the solution bulk, whereas ions probably took place between the bulk and a layer of organic molecules. These observations called for a more detailed modeling.
We investigated the effects of increased concentrations of the solutes, salicylic acid, benzoic acid, and o-, m-, and p-methoxy benzoic acids, on the anisotropic properties of a liquid crystal solvent. The lamellar liquid crystal was composed of 37% polyoxyethylene (20) isohexadecyl ether in aqueous buffer of pH 1. Phase change, transition temperature, refractive index, and specific resistance of the mesophase were studied in the presence of solutes. Transfer rates of the solutes from the bulk mesophase into aqueous buffer across a lipoidal barrier were used to determine their apparent permeability coefficients. The results indicate that a phase change occurred in the liquid crystal from a lamellar to a hexagonal structure, in the case of salicylic, benzoic, and m-methoxy benzoic acids. However, o- and p-methoxy benzoic acids showed no effect on the packing arrangement of the liquid crystal in the concentration range studied. The occurrence of the phase change was both solute and concentration dependent. Relative values of apparent permeability coefficients of solutes reflected the extent of solute-solvent interactions in the systems.
Mouse morulae were exposed in one step to a vitrification solution (EFS, a modified PBS containing 40% ethylene glycol, 18% Ficoll, and 0.3-M sucrose) at various temperatures, then cooled rapidly in liquid nitrogen, and then warmed rapidly. All of the embryos exposed to the EFS solution for 0.5 min at 25 degrees C before vitrification developed in culture. However, survival rates were lower if the duration of exposure was prolonged to 2, 5, or 10 min. At lower ambient temperatures (20, 10, and 5 degrees C), high survival rates were associated with longer exposure to the EFS solution. The toxicity of the EFS solution was also lower at lower temperatures. The toxic injury of morulae was manifested as decompaction of the blastomeres. Among the three additives in the EFS solution, ethylene glycol, which can cross cell membranes, was responsible for the toxicity. The results show that the optimum time for exposure of the embryos to the EFS solution before rapid cooling varies with the ambient temperature, i.e., 0.5 min at 25 degrees C, 0.5-5 min at 20 degrees C, 2-5 min at 10 degrees C, and 2-10 min at 5 degrees C. If they are exposed for an optimum period, almost all mouse morulae can survive vitrification (94-100%).
The study of nucleation and growth mechanisms of salts from aqueous solutions, as a function of supersaturation, is described using both macroscopic and microscopic experiments. In situ observations in a fluid cell in an atomic force microscope (AFM) reveal phenomena not accounted for in standard crystal-growth theories, specifically on the role of the crystal structure of the substrate in controlling spiral growth and two-dimensional nucleation. As a model example, the crystallization of two isostructural salts, BaSO(4) and SrSO(4), is described. The growth of solid-solution crystals is considerably more complex. The supersaturation of a given aqueous solution relative to a solid solution is different with respect to each solid composition, and it leads to the possibility that different compositions can simultaneously grow by different mechanisms on the same crystal face. Oscillatory compositional zoning is another consequence of the interplay between the thermodynamics and the kinetics of nucleation. The factors which control nucleation and growth of the solid solution (Ba,Sr)SO(4) from an aqueous solution are described. The predictions made from the theory are compared with direct observations of crystal growth in an AFM.
1. Although less than 150 mL of a 500 mL bottle of irrigating solution is typically used, it is not safe to respike the solution for another patient. 2. Presterilized, disposable, multi-use dispensing systems have been used for years to compound IV solutions; the same principle can now be used for irrigating solutions. 3. The Multi-Spike device can continuously deliver irrigation solution through three sterile ports after initial spiking of the solution bottle safely and at a lowered cost.
Gum arabic (GA) is a natural proteoglycan with proabsorptive capacity attributable to its physico-chemical properties. Previous experiments showed that in rats oral administration of GA in an isotonic solution had a generally positive effect. This study extends the investigation to include acetaminophen and to evaluate whether GA could also act under secretory conditions induced by theophylline. Test solutions were orally administered to rats under CO2 anesthesia and blood concentrations followed for 3 hr. The secretory effects of theophylline were clearly observed for sodium and zinc. Addition of GA resulted in a more rapid rate of glutamate absorption, under normal physiologic conditions, as indicated by the higher area under the curve (AUC). There were no differences in the presence of theophylline. Acetaminophen blood concentrations peaked about 30 min after administration, and the AUC in rats that received GA was higher than in those that got the solution without GA. AUCs for total body water distribution with time and those for glucose concentrations were indistinguishable whether the solutions contained or did not contain either GA or theophylline. The results confirm that oral administration of GA can accelerate absorption of some solutes, including pharmacologic agents.
For the storage of human transplanted organs, the benefit of "UW solution" has been proven especially in keeping a longer preservation time for the liver and pancrease; however, the value for kidney preservation was still debated. A total of 293 cases of renal transplantation were performed over 12 years in our hospital and 206 cases were cadaveric transplants. The latter ones were further divided into 3 groups, according to the immunosuppressive medication and preservation solution used. In the CsA treated groups, the ATN rates significantly decreased in those preserved with the UW solution than with the UR solution. Although the UW solution did not improve the graft survival in our series, it did save the cost for postoperative hemodialysis and shorten the hospital stay which made it cost effective.
Deuterium oxide solutions of schizophyllan, a triple-helical polysaccharide, undergoing an order-disorder transition centered at 17 degrees C, were studied by optical rotation (OR) and heat capacity (C(p)) to elucidate the molecular mechanism of the transition and water structure in the solution and frozen states. The ordered structure at low temperature consisted of the side chains and water in the vicinity forming an ordered hydrogen-bonded network surrounding the helix core and was disordered at higher temperature. In the solution state appeared clearly defined transition curves in both the OR and C(p) data. The results for three samples of different molecular weights were analyzed theoretically, treating this transition as a typical linear cooperative transition from the ordered to disordered states and explained quantitatively if the molecular weight polydispersity of the sample was considered. The excess heat capacity C(EX)(p) defined as the C(p) minus the contributions from schizophyllan and D(2)O was estimated. In the frozen state it increased with raising temperature above 150 K until the mixture melted. This was compared with the dielectric increment observed in this temperature range and ascribed to unfreezable water. From the heat capacity and dielectric data, unfreezable water is mobile but more ordered than free water. In the solution state, the excess heat capacity originates from the interactions of D(2)O molecules as bound water and structured water, and so forth. Thus the schizophyllan triple helix molds water into various structures of differing orders in solution and in the solid state.
Noncross-linked acrylamide (AA)-N-isopropylacrylamide (IPAAm) copolymers have been used as a buffer additive in capillary electrophoretic separation of structurally similar small solutes. Seven kinds of barbiturates and five kinds of dansylated (Dns) amino acids, which have different hydrophobic side chains, were separated on poly(AA-co-IPAAm)-filled columns and on AA polymer-filled columns under the condition of totally eliminating the contribution of electroosmotic flow (EOF). It is known that the copolymer containing IPAAm has thermosensitive properties, and the hydrophobicity of its surface changes with surrounding temperature. In this investigation, therefore, the effects of an isopropyl group in the copolymer on the electrophoretic separation of the small solutes were studied by comparing the two polymer-filled columns at ambient temperature and at elevated temperature. Although slight differences in migration behavior were observed at ambient temperature between the columns filled with these two polymer solutions, obvious differences in the separation of the solutes were observed at elevated temperature. The observed changes on the migration behavior might be caused by the interaction between copolymer chains exhibiting hydrophobic property and the solute.