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PubMed2003

An isothermal titration calorimetry study on the binding of four volatile general anesthetics to the hydrophobic core of a four-alpha-helix bundle protein.

A molecular understanding of volatile anesthetic mechanisms of action will require structural descriptions of anesthetic-protein complexes. Previous work has demonstrated that the halogenated alkane volatile anesthetics halothane and chloroform bind to the hydrophobic core of the four-alpha-helix bundle (Aalpha(2)-L38M)(2) (Johansson et al., 2000, 2003). This study shows that the halogenated ether anesthetics isoflurane, sevoflurane, and enflurane are also bound to the hydrophobic core of the four-alpha-helix bundle, using isothermal titration calorimetry. Isoflurane and sevoflurane both bound to the four-alpha-helix bundle with K(d) values of 140 +/- 10 micro M, whereas enflurane bound with a K(d) value of 240 +/- 10 micro M. The DeltaH degrees values associated with isoflurane, sevoflurane, and enflurane binding were -7.7 +/- 0.1 kcal/mol, -8.2 +/- 0.2 kcal/mol, and -7.2 +/- 0.1 kcal/mol, respectively. The DeltaS degrees values accompanying isoflurane, sevoflurane, and enflurane binding were -8.5 cal/mol K, -10.4 cal/mol K, and -8.0 cal/mol K, respectively. The results indicate that the hydrophobic core of (Aalpha(2)-L38M)(2) is able to accommodate three modern ether anesthetics with K(d) values that approximate their clinical EC(50) values. The DeltaH degrees values point to the importance of polar interactions for volatile general anesthetic binding, and suggest that hydrogen bonding to the ether oxygens may be operative.

Anesthetics, General↗
PubMed1986

The influence of cholesterol on the main phase transition of unilamellar dipalmytoylphosphatidylcholine vesicles. A differential scanning calorimetry and iodine laser T-jump study.

The influence of cholesterol (CHOL) on the main phase transition in single shell dipalmytoylphosphatidylcholine (DPPC) vesicles was investigated in equilibrium and kinetic experiments. CHOL increases the optical density and causes a slight hysteresis in turbidity transition curves. Static fluorescence anisotropy measurements showed interesting differences for three probes sensing different parts in the hydrophobic region of the phospholipid bilayer. Differential scanning calorimetry (DSC) peaks can be separated into a narrow and a broad component. The narrow component, which decreases linearly with increasing CHOL content and disappears at 20 mol %, is attributed to the transition of free phospholipid, while the broad component, being associated with the transition of CHOL-lipid units, increases monotoniously from 0 to 20%. Kinetic experiments were performed on our iodine-laser T-jump arrangement with turbidity detection. Three cooperative relaxation signals in the microsecond and millisecond time range were detected for pure DPPC vesicles as well as vesicles containing 7.5 and 16.5 mol % CHOL. All three relaxation processes were changed by CHOL: the superposition of the three relaxation amplitudes can be separated into a narrow and a broad component, as in DSC experiments. A speculative model is presented which assumes an inhomogeneous CHOL distribution fluctuating on a millisecond time scale in the temperature region of the main phase transition.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1994

Differential scanning calorimetry of thermotropic phase transitions in vitaminylated lipids: aqueous dispersions of N-biotinyl phosphatidylethanolamines.

The thermotropic phase behavior of a homologous series of saturated diacyl phosphatidylethanolamines in which the headgroup is N-derivatized with biotin has been investigated by differential scanning calorimetry. In 1 M NaCl, derivatives with acyl chainlengths from C(12:0) to C(20:0) all exhibit sharp chain-melting phase transitions, which are reversible with a hysteresis of 1.5 degrees or less, except for the C(12:0) lipid which has a transition temperature below 0 degree C. The transition enthalpy and the transition entropy depend approximately linearly on the lipid chainlength, with incremental values per CH2 group that are very similar to those obtained for the corresponding underivatized phosphatidylethanolamines in aqueous dispersion. The chainlength-independent contribution to the transition enthalpy is significantly smaller than that for the underivatized phosphatidylethanolamines, and that for the transition entropy is much smaller; the latter suggesting that the N-biotinylated phosphatidylethanolamine headgroups are differently hydrated from those of the underivatized lipids. The gel-to-fluid phase transition temperatures of the N-biotinylated lipids are lower than those of the parent phosphatidylethanolamines, and their chainlength dependence conforms well with that predicted by assuming that the transition enthalpy and entropy are linearly dependent on chainlength. Although the chain-melting phase behavior is generally similar to that of the parent phosphatidylethanolamines, the gel phases (and the fluid phases in the case of chainlengths C(12:0) to C(16:0)) have a different lyotropic structure in the two cases, and this is reflected in the chainlength-independent contributions to the thermodynamic parameters. In the absence of salt, the thermotropic phase behavior of aqueous dispersions of the N-biotinyl phosphatidylethanolamines is considerably more complex. The transition temperatures are consistently lower than those in 1 M NaCI, but the transitions are broader, contain multiple peaks and exhibit a much larger hysteresis between heating and cooling scans. Additionally, the lipids with shorterchainlengths exhibit metastability in the absence of salt, converting from a micellar solution to a lamellar gel phase only after incubation at low temperature with freeze-thaw cycling.

Biotin↗
PubMed1995

Stages of the bilayer-micelle transition in the system phosphatidylcholine-C12E8 as studied by deuterium- and phosphorous-NMR, light scattering, and calorimetry.

The perturbation of phospholipid bilayer membranes by a nonionic detergent, octaethyleneglycol mono-n-dodecylether (C12E8), was investigated by 2H- and 31P-NMR, static and dynamic light scattering, and differential scanning calorimetry. Preequilibrated mixtures of the saturated phospholipids 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC), and 1,2-dilauroyl-sn-glycero-3-phosphorylcholine (DLPC) with the detergent were studied over a broad temperature range including the temperature of the main thermotropic phase transition of the pure phospholipids. Above this temperature, at a phospholipid/detergent molar ratio 2:1, the membranes were oriented in the magnetic field. Cooling of the mixtures below the thermotropic phase transition temperatures of the pure phospholipids led to micelle formation. In mixtures of DPPC and DMPC with C12E8, a narrow calorimetric signal at the onset temperature of the solubilization suggested that micelle formation was related to the disorder-order transition in the phospholipid acyl chains. The particle size changed from 150 nm to approximately 7 nm over the temperature range of the bilayer-micelle transition. The spontaneous orientation of the membranes at high temperatures enabled the direct determination of segmental order parameters from the deuterium spectra. The order parameter profiles of the phospholipid acyl chains could be attributed to slow fluctuations of the whole membrane and to detergent-induced local perturbations of the bilayer order. The packing constraints in the mixed bilayers that eventually lead to bilayer solubilization were reflected by the order parameters of the interfacial phospholipid acyl chain segments and of the phospholipid headgroup. These results are interpreted in terms of the changing average shape of the component molecules. Considering the decreasing cross sectional areas in the acyl chain region and the increasing hydration of the detergent headgroups, the bilayer-micelle transition is the result of an imbalance in the chain and headgroup repulsion. A neutral or pivotal plane can be defined on the basis of the temperature dependence of the interfacial quadrupolar splittings.

Calorimetry, Differential Scanning↗
PubMed1996

Evaluation of linked protonation effects in protein binding reactions using isothermal titration calorimetry.

A theoretical development in the evaluation of proton linkage in protein binding reactions by isothermal titration calorimetry (ITC) is presented. For a system in which binding is linked to protonation of an ionizable group on a protein, we show that by performing experiments as a function of pH in buffers with varying ionization enthalpy, one can determine the pK(a)'s of the group responsible for the proton linkage in the free and the liganded states, the protonation enthalpy for this group in these states, as well as the intrinsic energetics for ligand binding (delta H(o), delta S(o), and delta C(p)). Determination of intrinsic energetics in this fashion allows for comparison with energetics calculated empirically from structural information. It is shown that in addition to variation of the ligand binding constant with pH, the observed binding enthalpy and heat capacity change can undergo extreme deviations from their intrinsic values, depending upon pH and buffer conditions.

Calorimetry↗
PubMed1996

The effect of increasing membrane curvature on the phase transition and mixing behavior of a dimyristoyl-sn-glycero-3-phosphatidylcholine/ distearoyl-sn-glycero-3-phosphatidylcholine lipid mixture as studied by Fourier transform infrared spectroscopy and differential scanning calorimetry.

The phase transition behavior of a lipid bilayer of dimyristoyl-sn-glycero-3-phosphatidylcholine/distearoyl-sn-glycero-3- phosphatidylcholine (DMPC-d54/DSPC) (1:1) on a solid support with varying curvatures was investigated with differential scanning calorimetry, infrared spectroscopy, and model calculations. With increasing curvature the temperatures of the liquidus and solidus points are shifted to lower values by up to 7 degrees C and 15 degrees C, and the mixing of the two lipid species in the two phase region is altered. With increasing curvature the DSPC dominates the gel phase, whereas the DMPC-d54 is expelled to the fluid phase. Whereas the planar system shows a nearly simultaneous phase transition of DSPC and DMPC-d54, the spherical system with the highest curvature exhibits an almost complete separation of the phase transitions of the two lipids. Model calculations suggest that the shift of the liquidus point can be understood as a reduction of the lateral pressure in the bilayer with increasing curvature. The shift of the solidus line is interpreted as a result of the increased demixing of the two components in the two-phase region with increasing curvature due to lowering of the lateral pressure.

Biophysical Phenomena↗
PubMed1996

The interfacial structure of phospholipid bilayers: differential scanning calorimetry and Fourier transform infrared spectroscopic studies of 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine and its dialkyl and acyl-alkyl analogs.

The thermotropic phase behavior of aqueous dispersions of dipalmitoylphosphatidylcholine (DPPC) and its 1,2-dialkyl, 1-acyl 2-alkyl and 1-alkyl 2-acyl analogs was examined by differential scanning calorimetry, and the organization of these molecules in those hydrated bilayers was studied by Fourier transform infrared spectroscopy. The calorimetric data indicate that substitution of either or both of the acyl chains of DPPC with the corresponding ether-linked hydrocarbon chain results in relatively small increases in the temperature (< 4 degrees C) and enthalpy (< 1 kcal/mol) of the lipid chain-melting phase transition. The spectroscopic data reveal that replacement of one or both of the ester-linked hydrocarbon chains of DPPC with its ether-linked analog causes structural changes in the bilayer assembly, which result in an increase in the polarity of the local environments of the phosphate headgroups and of the ester carbonyl groups at the bilayer polar/apolar interface. The latter observation is unexpected, given that ester linkages are considered to be intrinsically more polar that ether linkages. This finding cannot be satisfactorily rationalized unless the conformation of the glycerol backbones of the analogs containing ether-linked hydrocarbon chains differs significantly from that of diacyl glycerolipids such as DPPC. A comparison of the alpha-methylene scissoring bands and the methylene wagging band progressions of these lipids with the corresponding absorption bands of specifically chain-perdeuterated analogs of DPPC also supports the conclusion that replacement of the ester-linked hydrocarbon chains of DPPC with the corresponding ether-linked analog induces conformational changes in the lipid glycerol backbone. The suggestion that the conformation of glycerol backbones in the alkyl-acyl and dialkyl derivatives of DPPC differs from that of the naturally occurring 1,2-diacyl glycerolipid suggests that mono- and di-alkyl glycerolipids may not be good models of their diacyl analogs. These results, and previously published evidence that DPPC analogs with ether-linked hydrocarbon chains spontaneously form chain-interdigitated gel phases at low temperatures, clearly indicate that the properties of lipid bilayers can be substantially altered by small changes in the chemical structures of their polar/polar interfaces, and highlight the critical role of the interfacial region as a determinant of the structure and organization of lipid assemblies.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1997

Partitioning of octyl glucoside between octyl glucoside/phosphatidylcholine mixed aggregates and aqueous media as studied by isothermal titration calorimetry.

Stepwise dilution of lipid-surfactant mixed micelles first results in extraction of surfactant from the mixed micelles into the aqueous medium. Subsequently mixed micelles transform into vesicles, within a range of compositions that corresponds to equilibrium coexistence between these two types of aggregates. Further dilution results in extraction of surfactant from the resultant mixed vesicles. In the present study, we have investigated the heat evolution of these processes, as they occur in mixed systems composed of egg phosphatidylcholine (PC) and the nonionic surfactant octylglucoside (OG). A combined use of isothermal titration calorimetry (ITC) and photon correlation spectroscopy (PCS), capable of monitoring phase transformations, revealed that 1) The sum of all of the studied processes (i.e., extraction of OG from mixed micelles and vesicles and the phase transformation) is isocaloric at approximately 40 degrees C throughout the whole dilution. At lower temperatures, all of the dilution steps are exothermic, whereas at higher temperatures all of them are endothermic. 2) At all temperatures, the absolute value of the heat associated with each dilution step within the range of coexistence of micelles and vesicles is almost constant and larger than in either the micellar or the vesicular range. We give an interpretation of these calorimetric data in terms of the relationship between the composition of the mixed aggregates Re and the aqueous concentration of surfactant monomers Dw. Assuming that the main contribution to the heat evolution is due to extraction of surfactant from mixed aggregates to the aqueous solution, we deduce the relationship Dw(Re) characterizing the system over the whole range of compositions. We find that, in accord with thermodynamic expectations, Dw is almost constant throughout the range of coexistence of mixed micelles and vesicles.

Absorptiometry, Photon↗
PubMed1997

Differential scanning calorimetry of chain-melting phase transitions of N-acylphosphatidylethanolamines.

Phosphatidylethanolamines in which the polar headgroup is N-acylated by a long-chain fatty acid (N-acyl PEs) are present in many plasma membranes under normal conditions, and their content increases dramatically in response to membrane stress in a variety of organisms. The thermotropic phase behavior of a homologous series of saturated N-acyl PEs, in which the length of the N-acyl chain is equal to that of the O-acyl chains attached at the glycerol backbone, has been investigated by differential scanning calorimetry (DSC). All fully hydrated N-acyl PEs with even chain lengths from C-12 to C-18 exhibit sharp endothermic chain-melting phase transitions in the absence of salt and in 1 M NaCl. Cooperative chain-melting is demonstrated directly by the temperature dependence of the electron spin resonance spectra from probe phospholipids bearing a spin label group in the acyl chain. The calorimetric transition enthalpy and the transition entropy obtained from DSC depend approximately linearly on the chain length with incremental values per CH2 group that exceed those of normal diacyl phosphatidylethanolamines, but to an extent that underrepresents the additional N-acyl chain. A thermodynamic model is constructed for the chain-length dependences and end effects of the calorimetric quantities, which includes a deficit proportional to the difference in O-acyl and N-acyl chain lengths for nonmatched chains, as is found and justified structurally for mixed-chain diacyl phospholipids. From data on the chain-length dependence of N-acyl diC16PEs, it is then deduced that the N-acyl chains are less well packed than the O-acyl chains and, from the data on the matched-chain N-acyl PEs, that the O-acyl chain packing is similar to that in normal diacyl PEs. The gel-to-fluid phase transition temperatures of the N-acyl PEs in the absence of salt are practically the same as those of the normal diacyl PEs of the corresponding chain lengths, although the transition enthalpies and entropies are appreciably greater, indicating entropy-enthalpy compensation. In 1 M NaCl, the transition temperatures are 3-4.5 degrees higher than in the absence of salt, representing the contribution of the electrostatic surface potential of the N-acyl PEs.

Acylation↗
PubMed1997

Titration calorimetry of anesthetic-protein interaction: negative enthalpy of binding and anesthetic potency.

Anesthetic potency increases at lower temperatures. In contrast, the transfer enthalpy of volatile anesthetics from water to macromolecules is usually positive. The transfer decreases at lower temperature. It was proposed that a few selective proteins bind volatile anesthetics with negative delta H, and these proteins are involved in signal transduction. There has been no report on direct estimation of binding delta H of anesthetics to proteins. This study used isothermal titration calorimetry to analyze chloroform binding to bovine serum albumin. The calorimetrically measured delta H cal was -10.37 kJ.mol-1. Thus the negative delta H of anesthetic binding is not limited to signal transduction proteins. The binding was saturable following Fermi-Dirac statistics and is characterized by the Langmuir adsorption isotherms, which is interfacial. The high-affinity association constant, K, was 2150 +/- 132 M-1 (KD = 0.47 mM) with the maximum binding number, Bmax = 3.7 +/- 0.2. The low-affinity K was 189 +/- 3.8 M-1 (KD = 5.29 mM), with a Bmax of 13.2 +/- 0.3. Anesthetic potency is a function of the activity of anesthetic molecules, not the concentration. Because the sign of delta H determines the temperature dependence of distribution of anesthetic molecules, it is irrelevant to the temperature dependence of anesthetic potency.

Anesthetics↗
PubMed1999

Ice premelting during differential scanning calorimetry.

Premelting at the surface of ice crystals is caused by factors such as temperature, radius of curvature, and solute composition. When polycrystalline ice samples are warmed from well below the equilibrium melting point, surface melting may begin at temperatures as low as -15 degrees C. However, it has been reported (Bronshteyn and Steponkus, 1993. Biophys. J. 65:1853-1865) that when polycrystalline ice was warmed in a differential scanning calorimetry (DSC) pan, melting began at about -50 degrees C, this extreme behavior being attributed to short-range forces. We show that there is no driving force for such premelting, and that for pure water samples in DSC pans curvature effects will cause premelting typically at just a few degrees below the equilibrium melting point. We also show that the rate of warming affects the slope of the DSC baseline and that this might be incorrectly interpreted as an endotherm. The work has consequences for DSC operators who use water as a standard in systems where subfreezing runs are important.

Calorimetry, Differential Scanning↗
PubMed1999

A "release" protocol for isothermal titration calorimetry.

Isothermal titration calorimetry (ITC) has become a standard method for investigating the binding of ligands to receptor molecules or the partitioning of solutes between water and lipid vesicles. Accordingly, solutes are mixed with membranes (or ligands with receptors), and the subsequent heats of incorporation (or binding) are measured. In this paper we derive a general formula for modeling ITC titration heats in both binding and partitioning systems that allows for the modeling of the classic incorporation or binding protocols, as well as of new protocols assessing the release of solute from previously solute-loaded vesicles (or the dissociation of ligand/receptor complexes) upon dilution. One major advantage of a simultaneous application of the incorporation/binding and release protocols is that it allows for the determination of whether a ligand is able to access the vesicle interior within the time scale of the ITC experiment. This information cannot be obtained from a classical partitioning experiment, but it must be known to determine the partition coefficient (or binding constant and stochiometry) and the transfer enthalpy. The approach is presented using the partitioning of the nonionic detergent C12EO7 to palmitoyloleoylphosphatidylcholine vesicles. The release protocol could also be advantageous in the case of receptors that are more stable in the ligand-saturated rather than the ligand-depleted state.

Biophysical Phenomena↗
PubMed1976

Studies on the isothermal crystallization of D-glucose and cellulose oligosaccharides by differential scanning calorimetry.

Isothermal crystallization from the glassy state of D-glucose and cellulose oligosaccharides (e.g., cellobiose, cellotriose, and cellotetraose) has been studied by differential scanning calorimetry. The crystallization of amorphous D-glucose and oligosaccharides was very difficult in the absence of traces of water. Amorphous cellobiose and cellotetraose crystallized far more rapidly than amorphous D-glucose and cellotriose. The activation energy for the crystallization of cellobiose and cellotetraose was approximately 10-12 kJ. mol(-1), while that for D-glucose and cellotriose was approximately 1-2 kJ. mol(-1). An odd-even effect seemed to be associated with the crystallization process of these saccharides.

Calorimetry↗
PubMed2003

Microscopy and calorimetry as complementary techniques to analyze sugar crystallization from amorphous systems.

A comparison of microscopic and macroscopic techniques to evaluate sugar crystallization kinetics is presented using amorphous lactose and lactose-trehalose mixtures. Polarized light video microscopy (PLV) and differential scanning calorimetry (DSC) were applied to measure crystallization kinetics, induction times and time for complete sugar crystallization at different storage temperatures (60-95 degrees C). DSC was also employed to measure the glass transition temperature (T(ag)) of the systems. PLV permitted direct observation, in real time, of growth of individual crystals and morphological aspects at a scale not detected by DSC. Taking the average of several microscopic observations, the results for temperature dependence of crystallization rate and time to complete lactose crystallization were similar to those obtained by DSC. Both PLV and DSC techniques showed that the presence of trehalose delayed lactose crystallization, without affecting the T(ag) value. For the analysis of sugar crystallization in amorphous systems, PLV and DSC proved to be complementary techniques. Validation of results obtained by PLV with results from DSC opens a new area of microstructural analysis of crystallizing systems.

Calorimetry, Differential Scanning↗
PubMed1999

A differential scanning calorimetry study of the interaction of lasalocid antibiotic with phospholipid bilayers.

Interaction of lasalocid sodium salt (Las-Na) with dipalmitoylphosphatidylcholine (DPPC) as a membrane model was investigated by highly-sensitive differential scanning calorimetry (DSC). The insertion properties of the antibiotic were studied both in multilamellar suspensions and unilamellar vesicles, for Las-Na/DPPC molar ratios (r) ranging from 0.005 to 0.1. The effect of the antibiotic on the lipid thermotropic behavior is concentration dependent and drastically changes at a critical r of 0.04 in both model membranes. Below this ratio, Las-Na molecules interact with DPPC bilayers without disrupting the global organization of the membrane. In the multilamellar systems only the transition cooperativity is affected whereas for the mixed vesicles, a decrease in the enthalpy change suggests a different mode of insertion. Above this ratio, implantation of the antibiotic give rise to lateral phase separation in multilamellar systems. These structural modifications have repercussions on the formation of mixed LAS-Na/DPPC vesicles which seems limited to an r value of 0.04.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2002

N-Myristoylethanolamine-cholesterol (1:1) complex: first evidence from differential scanning calorimetry, fast-atom-bombardment mass spectrometry and computational modelling.

The interaction of N-myristoylethanolamine (NMEA) with cholesterol is investigated by differential scanning calorimetry (DSC), fast-atom-bombardment mass spectrometry (FAB-MS) and computational modelling. Addition of cholesterol to NMEA leads to a new phase transition at 55 degrees C besides the chain-melting transition of NMEA at 72.5 degrees C. The enthalpy of the new transition increases with cholesterol content up to 50 mol%, but decreases thereafter, vanishing at 80 mol%. The enthalpy of the chain-melting transition of NMEA decreases with an increase in cholesterol; the transition disappears at 50 mol%. FAB-MS spectra of mixtures of NMEA and cholesterol provide clear signatures of the formation of ([NMEA+cholesterol]+) ([NMEA+cholesterol+Na]+). These results are consistent with the formation of a 1:1 complex between NMEA and cholesterol. Molecular modelling studies support this experimental finding and provide a plausible structural model for the complex, which highlights multiple H-bond interactions between the hydroxy group of cholesterol and the hydroxy and carbonyl groups of NMEA besides appreciable dispersion interaction between the hydrocarbon domains of the two molecules.

Calorimetry, Differential Scanning↗
PubMed1998

Thermally induced chain exchange of smooth muscle tropomyosin dimers studied by differential scanning calorimetry.

The thermal unfolding of duck gizzard tropomyosin dimers, alphabeta, alphaalpha, and betabeta, and of a 1:1 mixture of alphaalpha and betabeta homodimers was studied by differential scanning calorimetry (DSC). Both alphaalpha and betabeta homodimers demonstrated a broad thermal transition with maxima at 37.4 degrees C and 44.6 degrees C, respectively. However, a sharp cooperative thermal transition at 41.5 degrees C characteristic for alphabeta heterodimer appeared on the thermogram of the mixture of homodimers. The appearance of this transition was prevented by disulfide cross-linking of polypeptide chains in the homodimers. Thus, DSC studies clearly demonstrate formation of tropomyosin heterodimers during heating of the mixture of homodimers and in agreement with earlier published reports indicate thermally induced chain exchange between tropomyosin dimers.

Animals↗
PubMed2003

Liquid chromatography and differential scanning calorimetry studies on the states of water in polystyrene-divinylbenzene copolymer gels.

The thermal phase transition behavior of water incorporated in crosslinked polystyrene-divinylbenzene copolymer (PS-DVB) gel packings for liquid chromatography was investigated by differential scanning calorimetry. Free or bulk water, freezable bound or intermediate water, and nonfreezing water were observed for TSKgel Styrene-250 samples, while only free water and nonfreezing water were observed for TSKgel Styrene-60 samples. Freezable bound water and nonfreezing water in these gel samples were considered to be water confined in pores of the polymer gels. A liquid chromatographic method for determination of the amounts of stationary phase water was applied to the characterization of water in the PS-DVB beads in the columns and it was found out that any water in the PS-DVB gels did not function as the stationary phase contrary to the water sorbed in hydrophilic polymer gels; not only freezable bound water but also nonfreezing water in hydrophobic PS-DVB gels are similar to bulk water with respect to the affinity to the solute compounds.

Calorimetry, Differential Scanning↗