[Clusters of nonsolvent water in partially destroyed Saccharomyces cerevisiae yeast cells].

The state of water in partially destroyed dry yeast cells has been studied using low-temperature 1H NMR spectroscopy. It has been shown that the residual water is in the form of clusters of strongly and weakly associated water (SAW and WAW, respectively). Three or more types of SAW different in the chemical shift values have been found. It has been established that the interfacial water poorly dissolves hydrochloric and trifluoroacetic acids as well as DMSO and CD3CN. Hydrochloric acid on a surface of biomaterials can be separated into HCl and water. This process is stabilized by polar co-solvents (DMSO and CD3CN) added to the CDCl3 dispersion medium.

Low-temperature 1H-NMR spectroscopic study of doxorubicin influence on the hydrated properties of nanosilica modified by DNA.

The effect of the anticancer drug--doxorubicin (Dox) on hydration properties of a nanocomposite material deposited on silica and modified by small amount of DNA (0.6 wt%) was studied by means of (1)H NMR spectroscopy at low temperatures (in the range of 200-280 K). Signals of either weakly (WAW) or strongly (SAW) associated water, as well as water associated with electrondonor groups of the composite surface (ASW), were observed. The findings reveal that, depending on the temperature and the composition of the dispersion medium, fast molecular exchange takes place between different forms of interphase water. The presence of Dox (0.1-0.2 wt%) in the dispersion medium leads to change of the relative concentrations of different forms of water.

Polymethylsiloxane alone and in composition with nanosilica under various conditions.

Disperse polymethylsiloxane (PMS) alone and in a mixture with highly disperse nanosilica A-300 was studied as a dry powder and a hydrogel located in various dispersion media (air, chloroform alone and with addition of trifluoroacetic acid) using low-temperature 1H NMR spectroscopy, cryoporometry, thermogravimetry, nitrogen adsorption, microscopy, infrared spectroscopy, and quantum chemistry. The powders of dried PMS and PMS/A-300 can be easily rehydrated upon strong stirring with added water. The slurry properties depend on mechanical treatment features due to stronger compaction of the secondary structures with increasing mechanical loading. The organization of bound water (at a constant hydration degree h = 1 g/g) depends strongly on the dispersion media (because chloroform can displace water from narrow interparticle voids into broader ones or into pores inaccessible for larger CDCl3 molecules) and mechanical loading reorganizing aggregates of PMS and A-300 nanoparticles (<1 µm in size) and agglomerates (>1 µm) of aggregates. The PMS/nanosilica blends could be of interest from a practical point of view due to additional control of the textural and structural characteristics determining efficiency of sorbents with respect to low- and high-molecular weight compounds depending on the dispersion media that is of importance, e.g., for medical applications.

Structural features of polymer adsorbent LiChrolut EN and interfacial behavior of water and water/organic mixtures.

The structural and adsorption characteristics of polymer adsorbent LiChrolut EN and the behavior of adsorbed water and water/organic mixtures were studied using adsorption, microcalorimetry, transmission and scanning electron microscopy, mass spectrometry, infrared spectroscopy, 1H NMR spectroscopy with layer-by-layer freezing-out of liquids (190-273 K), and thermally stimulated depolarization current method (90-265 K). This adsorbent is characterized by large specific surface area (approximately 1500 m2/g) and pore volume (0.83 cm3/g) with a major contribution of narrow pores (R<10 nm) of a complicated shape (long hysteresis loop is in nitrogen adsorption-desorption isotherm). The adsorbent includes aromatic and aliphatic structures and oxygen-containing functionalities and can effectively adsorb organics and water/organic mixtures. On co-adsorption of water and organics (dimethyl sulfoxide, chloroform, methane), there is a weak influence of one on another adsorbate due to their poor mixing in pores. Weakly polar chloroform displaces a fraction of water from narrow pores. These effects can explain high efficiency of the adsorbent in solid-phase extraction of organics from aqueous solutions. The influence of structural features of several carbon and polymer adsorbents on adsorbed nitrogen, water and water/organics is compared on the basis of the adsorption and 1H NMR data.

Bonding of doxorubicin to nanosilica and human serum albumin in various media.

Interaction of doxorubicin hydrochloride (DOX) (anti-cancer drug) with hydro-compacted nanosilica A-300 (cA-300) alone or cA-300/human serum albumin (HSA) at a small content of water (h = 0.4 g per gram of dry silica) in different dispersion media (air, chloroform, and chloroform/trifluoroacetic acid) was analyzed using low-temperature 1H NMR spectroscopy, NMR cryoporometry and quantum chemistry to elucidate specific changes in the interfacial layers. Initial (bulk density ρb ≈ 0.046 g/cm3) and hydro-compacted (ρb ≈ 0.051-0.265 g/cm3 as a function of the hydration degree) nanosilicas were analyzed using nitrogen adsorption-desorption, gelatin adsorption, small angle X-ray scattering (SAXS), TEM, and infrared (FTIR) spectroscopy. Equilibrium adsorption of DOX onto cA-300 and cA-300/HSA was analyzed using ultraviolet-visible light spectroscopy. Photon correlation spectroscopy was used to analyze the particle size distribution in aqueous suspensions with various contents of components. DOX more strongly bound to HSA than silica also affects structure of interfacial water layers that depends on dispersion media because chloroform as immiscible with water changes the water organization to enlarge water structures. In aqueous media, DOX alone remains mainly in the form of nano/microparticles (50 nm-2 µm in size). However, with the presence of cA-300, cA-300/HSA, and HSA alone DOX transforms into pure nano-sized structures. These effects are explained by effective bonding of DOX to HSA having good transport properties with respect to drug molecules/ions that exceed similar properties of nanosilica alone, but cA-300/HSA can be a more effective composite as a drug carrier.

TSDC spectroscopy of relaxational and interfacial phenomena.

Applications of thermally stimulated depolarisation current (TSDC) technique to a variety of systems with different dispersion phases such as disperse and porous metal oxides, polymers, liquid crystals, amorphous and crystalline solids, composites, solid solutions, biomacromolecules, cells, tissues, etc. in gaseous or liquid dispersion media are analysed. The effects of dipolar, direct current (dc) and space charge relaxations are linked to the temperature dependent mobility of molecules, their fragments, protons, anions, and electrons and depend on thermal treatment, temperature and field intensity of polarisation, heating rate on depolarisation or cooling rate on polarisation. Features of the relaxation mechanisms are affected not only by the mentioned factors but also by morphological, structural and chemical characteristics of materials. The interfacial phenomena, especially the role of interfacial water, received significant attention on analysis of the TSDC data. Comparison of the data of TSDC and dielectric relaxation spectroscopy (DRS), differential scanning calorimetry (DSC), 1H NMR spectroscopy with layer-by-layer freezing-out of bulk and interfacial water, adsorption/desorption of nitrogen, water and dissolved organics demonstrates high sensitivity and information content of the TSDC technique, allowing a deeper understanding of interfacial phenomena.

Comparative characterization of polymethylsiloxane hydrogel and silylated fumed silica and silica gel.

Polymethylsiloxane (PMS) hydrogel (C(PMS)=10 wt%, soft paste-like hydrogel), diluted aqueous suspensions, and dried/wetted xerogel (powder) were studied in comparison with suspensions and dry powders of unmodified and silylated nanosilicas and silica gels using (1)H NMR, thermally stimulated depolarization current (TSDC), quasielastic light scattering (QELS), rheometry, and adsorption methods. Nanosized primary PMS particles, which are softer and less dense than silica ones because of the presence of CH(3) groups attached to each Si atom and residual silanols, form soft secondary particles (soft paste-like hydrogel) that can be completely decomposed to nanoparticles with sizes smaller than 10 nm on sonication of the aqueous suspensions. Despite the soft character of the secondary particles, the aqueous suspensions of PMS are characterized by a higher viscosity (at concentration C(PMS)=3-5 wt%) than the suspension of fumed silica at a higher concentration. Three types of structured water are observed in dry PMS xerogel (adsorbed water of 3 wt%). These structures, characterized by the chemical shift of the proton resonance at delta(H) approximately 1.7,3.7, and 5 ppm, correspond to weakly associated but strongly bound water and to strongly associated but weakly or strongly bound waters, respectively. NMR cryoporometry and QELS results suggest that PMS is a mesoporous-macroporous material with the textural porosity caused by voids between primary particles forming aggregates and agglomerates of aggregates. PMS is characterized by a much smaller adsorption capacity with respect to proteins (gelatin, ovalbumin) than unmodified fumed silica A-300.

[Effect of sugars on the hydration of serum albumin at low temperatures].

The influence of sugars (glucose, fructose, and sucrose) on the hydration characteristics of serum albumin was studied using 1H NMR spectroscopy in combination with layer-by-layer freezing-out of bulk and interfacial water. It was found that the presence of sugars in protein solution leads to a considerable decrease in the concentration of bound water at T < 273 K; i. e., sugars cause the dehydration of protein molecules, which may be caused by those alterations in albumin structure that are associated with the formation of more compact globular structures. The most considerable effect was recorded in case of sucrose, which causes a decrease in the dehydration of albumin by at least one order of magnitude. The interfacial energy values for the protein/water system were calculated.

Weakly and strongly associated nonfreezable water bound in bones.

Water bound in bone of rat tail vertebrae was investigated by 1H NMR spectroscopy at 210-300 K and by the thermally stimulated depolarization current (TSDC) method at 190-265 K. The 1H NMR spectra of water clusters were calculated by the GIAO method with the B3LYP/6-31G(d,p) basis set, and the solvent effects were analyzed by the HF/SM5.45/6-31G(d) method. The 1H NMR spectra of water in bone tissue include two signals that can be assigned to typical water (chemical shift of proton resonance deltaH=4-5 ppm) and unusual water (deltaH=1.2-1.7 ppm). According to the quantum chemical calculations, the latter can be attributed to water molecules without the hydrogen bonds through the hydrogen atoms, e.g., interacting with hydrophobic environment. An increase in the amount of water in bone leads to an increase in the amount of typical water, which is characterized by higher associativity (i.e., a larger average number of hydrogen bonds per molecule) and fills larger pores, cavities and pockets in bone tissue.

Integral equation for calculation of distribution function of activation energy of shear viscosity.

A new technique of calculation of a distribution function of activation energy (f(E)) of shear viscosity based on a regularization procedure applied to the Fredholm integral equation of the first kind has been developed using the Baxter-Drayton and Brady model for concentrated and flocculated suspensions. This technique has been applied to the rheological data obtained at different shear rates for aqueous suspensions with fumed silica A-300 and low-molecular (3,4,5-trihydroxybenzoic acid and 1,5-dioxynaphthalene) or high-molecular (poly(vinyl pyrrolidone) of 12.7 kDa and ossein of 20-29 kDa) compounds over a wide concentration range (up to 25 wt% of both components) and at different temperatures. Monomodal f(E) distributions are observed for the suspensions with individual A-300 or A-300 with a low amount of adsorbed organics. In the case of larger amounts of nanosilica and organics the f(E) distributions are multimodal because of stronger structurization and coagulation of the systems that require a high energy to break the coagulation structures resisting to the shear flow.

Interfacial phenomena at a surface of individual and complex fumed nanooxides.

Investigations of interfacial and temperature behaviors of nonpolar and polar adsorbates interacting with individual and complex fumed metal or metalloid oxides (FMO), initial and subjected to various treatments or chemical functionalization and compared to such porous adsorbents as silica gels, precipitated silica, mesoporous ordered silicas, filled polymeric composites, were analyzed. Complex nanooxides include core-shell nanoparticles, CSNP (50-200nm in size) with titania or alumina cores and silica or alumina shells in contrast to simple and smaller nanoparticles of individual FMO. CSNP could be destroyed under high-pressure cryogelation (HPCG) or mechanochemical activation (MCA). These treatments affect the structure of aggregates of nanoparticles and agglomerates of aggregates, resulting in their becoming more compacted. The analysis shows that complex FMO could be more sensitive to external actions than simple nanooxides such as fumed silica. Any treatment of 'soft' FMO affects the interfacial and temperature behaviors of polar and nonpolar adsorbates. Rearrangement of secondary particles and surface functionalization affects the freezing-melting point depression of adsorbates. For some adsorbates, open hysteresis loops became readily apparent in adsorption-desorption isotherms. Clustering of adsorbates bound in textural pores in aggregates of nanoparticles (i.e., voids between nanoparticles in secondary structures) causes reduced changes in enthalpy during phase transitions (freezing, fusion, evaporation). Freezing point depression and melting point elevation cause significant hysteresis freezing-melting effects for adsorbates bound to FMO in the textural pores. Relaxation phenomena for both low- and high-molecular weight adsorbates or filled polymeric composites are affected by the morphology of primary particles, structural organization of secondary particles of differently treated or functionalized FMO, content of adsorbates, co-adsorption order, and temperature.

Unusual properties of water at hydrophilic/hydrophobic interfaces.

The behaviour of water at mosaic hydrophilic/hydrophobic surfaces of different silicas and in biosystems (biomacromolecules, yeast cells, wheat seeds, bone and muscular tissues) was studied in different dispersion media over wide temperature range using 1H NMR spectroscopy with layer-by-layer freezing-out of bulk water (close to 273 K) and interfacial water (180 < T < 273 K), thermally stimulated depolarization current (TSDC) (90 < T < 270 K), infrared (IR) spectroscopy, and quantum chemical methods. Bulk water and water bound to hydrophilic/hydrophobic interfaces can be assigned to different structural types. There are (i) weakly associated interfacial water (1H NMR chemical shift delta(H) = 1.1-1.7 ppm) that can be assigned to high-density water (HDW) with collapsed structure (CS), representing individual molecules in hydrophobic pockets, small clusters and interstitial water with strongly distorted hydrogen bonds or without them, and (ii) strongly associated interfacial water (delta(H) = 4-5 ppm) with larger clusters, nano- and microdomains, and continuous interfacial layer with both HDW and low-density water (LDW). The molecular mobility of weakly associated bound water is higher (because hydrogen bonds are distorted and weakened and their number is smaller than that for strongly associated water) than that of strongly associated bound water (with strong hydrogen bonds but nevertheless weaker than that in ice Ih) that results in the difference in the temperature dependences of the 1H NMR spectra at T < 273 K. These different waters are also appear in changes in the IR and TSDC spectra.

Structured water in partially dehydrated yeast cells and at partially hydrophobized fumed silica surface.

Nonfreezable water structured due to interaction with endocellular objects in yeast cells (endocellular water) or with partially hydrophobic fumed silica (interfacial water) was studied by means of (1)H NMR spectroscopy with layer-by-layer freezing-out of bulk water and quantum chemical methods applied to water clusters in the gas and liquid (chloroform and cyclohexene) phases and adsorbed on silylated silica. Variation in cell hydration as well as in amount of water adsorbed on modified fumed silica leads to changes in the ratio between contributions of two water states characterized by NMR chemical shifts at delta(H)=1.1-1.7 and 4-5 ppm. Lowering of hydration and temperature results in an enhancement of the first signal, and the opposite result is observed for the second signal. These effects may be explained by structured water distribution in the form of relatively large nanodroplets (delta(H)=4-5 ppm is close to that for bulk water) and small clusters of the 2D structure, in which the fraction of hydrogen atoms out of the hydrogen bonds (delta(H)=1.1-1.7 ppm) is larger than that in nanodroplets.

Morphology and surface properties of fumed silicas.

Several series of fumed silicas and mixed fumed oxides produced and treated under different conditions were studied in gaseous and liquid media using nitrogen and water adsorption-desorption, mass spectrometry, FTIR, NMR, thermally stimulated depolarization current (TSDC), photon correlation spectroscopy (PCS), zeta potential, potentiometric titration, and Auger electron spectroscopy methods. Aggregation of primary particles and adsorption capacity (Vp) decrease and hysteresis loops of nitrogen adsorption-desorption isotherms becomes shorter with decreasing specific surface area (S(BET)). However, the shape of nitrogen adsorption-desorption isotherms can be assigned to the same type independent of S(BET) value. The main maximum of pore size distribution (gaps between primary nonporous particles in aggregates and agglomerates) shifts toward larger pore size and its intensity decreases with decreasing S(BET) value. The water adsorption increases with increasing S(BET) value; however, the opposite effect is observed for the content of surface hydroxyls (in mmol/m2). Associative desorption of water (2(SiOH)-->SiOSi+H2O) depends on both the morphology and synthesis conditions of fumed silica. The silica dissolution rate increases with increasing S(BET) and pH values. However, surface charge density and the modulus of zeta-potential increase with decreasing S(BET) value. The PCS, 1H NMR, and TSDC spectra demonstrate rearrangement of the fumed silica dispersion depending on the S(BET) value and the silica concentration (C(SiO2)) in the aqueous suspensions. A specific state of the dispersion is observed at the C(SiO2) values corresponding to the bulk density of the initial silica powder.

Application of 1H NMR spectroscopy method for determination of characteristics of thin layers of water adsorbed on the surface of dispersed and porous adsorbents.

The paper presents 1H NMR spectroscopy as a perspective method of the studies of the characteristics of water boundary layers in the hydrated powders and aqueous dispergated suspensions of the adsorbents. The method involves measurements of temperature dependence proton signals intensity in the adsorbed water at temperatures lower than 273 K. Free energy of water molecules at the adsorbent/water interface is diminished due to the adsorption interactions causing the water dosed to the adsorbent surface freezes at T < 273 K. Thickness of a non-freezing layer of water can be determined from the intensity of the water signal of 1H NMR during the freezing-thawing process. Due to a disturbing action of the adsorbent surface, water occurs in the quasi-liquid state. As a result, it is observed in the 1H NMR spectra as a relatively narrow signal. The signal of ice is not registered due to great differences in the transverse relaxation times of the adsorbed water and ice. The method of measuring the free surface energy of the adsorbents from the temperature dependence of the signal intensity of non-freezing water is based on the fact that the temperature of water freezing decreases by the quantity which depends on the surface energy and the distance of the adsorbed molecules from the solid surface. The water at the interface freezes when the free energies of the adsorbed water and ice are equal. To illustrate the applicability of the method under consideration the series of adsorption systems in which the absorbents used differed in the surface chemistry and porous structure. In particular, the behaviour of water on the surface of the following adsorbents is discussed: non-porous and porous silica (aerosils, silica gels); chemically and physically modified non-porous and porous silica (silanization, carbonization, biopolymer deposition); and pyrogeneous Al2O3 and aluminasilicas. The effect of preliminary treatment of the adsorbent (thermal, high pressure, wetting with polar and non-polar solvents) on the characteristics of the structurized water layers was discussed. The influence of the adsorbent porous structure on the free energy of the adsorbed water was also studied. The discussion of the obtained results was made.

Influence of organics on the structure of water adsorbed on activated carbons.

The influence of organics on the structure of water adsorbed on activated carbons was studied using adsorption of nitrogen, benzene, and water, and by (1)H NMR spectroscopy with freezing out of bulk water with the presence of benzene-d(6) or chloroform-d. It was found that interactions of water with the activated carbon surface depend on both structural characteristics (contributions of micro- and mesopores, pore size distributions) of adsorbents and chemical properties (changed by oxidation or reduction) of the adsorbents. Moreover, the interfacial behavior of water is affected by water-insoluble organics such as benzene and chloroform. Changes in the Gibbs free energy of water adsorbed on carbons exposed to air, water, chloroform-d, or benzene-d(6) are related to textural properties of adsorbents and the degree of their oxidation. Since chloroform-d and benzene-d(6) are strongly adsorbed on activated carbons and immiscible with water they replace a significant portion of adsorbed water in micropores, on the walls of mesopores, and in the transport pores of carbons causing changes in the Gibbs free energy and other characteristics of water.

[The effect of serum albumin on the temperature of eutectic formation in binary solutions of organic compounds]. / Vliianie syvorotochnogo al'bumina na temperaturu obrazovaniia évtektikv binarnykh rastvorakh organicheskikh soedinenii.

The freezing water solutions of serum albumin in presence of additives of several organic compounds have been studied by 1H NMR spectroscopy. Freezing of the solutes in the protein solvation shells occurs at temperatures 30-50 degrees C higher in analogous double solutions.

[Study of alcohol binding with serum albumin by NMR spectra of frozen aqueous solutions]. / Izuchenie sviazyvaniia spirtov s syborotochnym al'buminom po spektram PMR zamorozhennykh vodnykh rastvorov.

Interaction of alcohols (methanol, glycerol, sorbitol) with human serum albumin (HSA) was studied by the use of NMR spectroscopy in frozen aqueous solutions. The amount of binding was shown to increase in the series methanol-glycerol-sorbitol, on this basis a suggestion is made that interaction of alcohols with HSA occurs due to the formation of hydrogen bonds in which the hydroxyl groups act as proton donors. It is found that the presence of albumin influences significantly the outcome of eutectics from a diluted methanol solution and glycerol solution, the temperature of eutectics decreases in case of methanol and increases in case of glycerol.

[A study of the effect of the adsorbed molecules of concanavalin A on characteristics of the bound water in the hydrate coat of the disperse silica by 1H NMR of the frozen water suspensions]. / Vliianie adsorbirovannykh molekul konkonovalina A na kharakteristiki sviazannoi vody v gidratnoi obolochke dispersnogo kremnezema po dannym 1H IaMR zamorozhennykh vodnykh suspenzii.

The experimental technique is presented which allows the investigation of water at the adsorbent-biopolymer interface by record of temperature dependencies of 1H NMR signals during the heating of previously frozen water suspensions. It was found that the adsorption of protein conconovalin A resulted in twofold decrease of strong bound water amount and in 70% increase of loosely bound one. The mean-value of Gibbs energy decreased twice for strong bound water and increased twice for loosely bound one. The external layer of hydrate shell of silica particles with adsorbed conconovalin A was organized by protein molecules. This conclusion is based on the observed total increase of loosely bound water amount, as a result, of protein adsorption, although its amount with respect to a protein molecule decreased.

Interactions of poly(dimethylsiloxane) with nanosilica and silica gel upon cooling-heating.

To control the properties of poly(dimethylsiloxane) (PDMS, Oxane 1000) as a bio-inert material, the characteristics of Oxane 1000 were compared for PDMS alone and interacting with silica gel Si-100 and nanosilica PS400. Low-temperature (1)H NMR spectroscopy, applied to static samples at 200-300 K, and differential scanning calorimetry (DSC) at 153-393 K were used to analyze the properties of PDMS and composites. The NMR study shows that liquid and solid-like fractions of PDMS co-exist over a broad temperature range. The cooling-heating cycles give hysteresis loops of intensity of (1)H NMR signals of methyl groups of a liquid fraction of PDMS vs. temperature depending on the silica type. The loop width differs for PDMS alone and bound to silicas, and the samples preheated at 420 K are characterized by much narrower loops. DSC measurements of the samples show a significant difference in the thermograms on the first and second DSC scans that depend on the silica type. For PDMS confined in pores of silica gel, 3D spatial structure of the polymers can be more ordered than that of PDMS located in thin layers at a surface of nanosilica. Therefore, both melting endotherms and crystallization exotherms are observed for PDMS/silica gel. However, for PDMS/nanosilica, both thermal features are much weaker and observed during only the first DSC scan.