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.

Interaction of poly(ethylene oxide) with fumed silica.

Interaction of poly(ethylene oxide) (PEO, 600 kDa) with fumed silica A-300 (SBET = 316 m2/g) was investigated under different conditions using adsorption, infrared (IR), thermal analysis (TG-DTA), AFM, and quantum chemical methods. The studied dried silica/PEO samples were also carbonized in a flow reactor at 773 K. The structural characteristics of fumed silica, PEO/silica, and pyrocarbon/fumed silica were investigated using nitrogen adsorption-desorption at 77.4 K. PEO adsorption isotherm depicts a high affinity of PEO to the fumed silica surface in aqueous medium. PEO adsorbed in the amount of 50 mg per gram of silica (PEO monolayer corresponds to CPEO approximately 190 mg/g) can disturb approximately 70% of isolated surface silanols. However, at the monolayer coverage, only 20% of oxygen atoms of PEO molecules take part in the hydrogen bonding with the surface silanols. An increase in the PEO amount adsorbed on fumed silica leads to a diminution of the specific surface area and contributions of micro- (pore radius R < 1 nm) and mesopores (1 < R < 25 nm) to the pore volume but contribution of macropores (R > 25 nm) increases with CPEO. Quantum chemical calculations of a complex of a PEO fragment with a tripple bond SiOH group of a silica cluster in the gas phase and with consideration for the solvent (water) effect show a reduction of interaction energy in the aqueous medium. However, the complex remains strong enough to provide durability of the PEO adsorption complexes on fumed silica; i.e., PEO/fumed silica nanocomposites could be stable in both gaseous and liquid media.

[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.

[Interaction of disperse silica with the surface of bovine reproductive cell and seminal plasma]. / Vzaimodeistvie dispersnogo kremnezema s poverkhnost'iu reproduktivnoi kletki i plazmoi semennoi zhidkosti byka.

The nature of contact interactions of highly disperse silica with the surface of bovine reproductive cells and seminal plasma is investigated. Surface proteins and glycoproteids, containing N-acetylneuraminic acid as a terminal residue, are shown to participate in this process. It is found that the efficiency of contact interaction falls with an increase in the concentration of the disperse silica from 0.1% to 1%.

[Sorption immobilization of glycerol on disperse silica and its interaction with the surface of bovine reproductive cells, seminal plasma and sperm]. / Sorptsionnaia immobilizatsiia glitserina na dispersnom kremnezeme i ego vzaimodeistvie s poverkhnost'iu reproduktivnykh kletok, semennoi plazmoi i spermoi byka.

The binding of hydroxylated disperse silica (I) surface and surface, modified by glycerol (II), with components of above-membrane matrix of bovine reproductive cell and seminal plasma was investigated. It was found that structure of inorganic support defined the character of binding SiO2 with proteins and glycoproteins, including those with hexose and N-acetylneuraminic acid as terminal residue. Value of binding depends on concentration of disperse silica contacting with biomaterial.

[Effect of the nature of the surface of disperse silica on its interaction with the reproductive cells and seminal plasma of cattle]. / Vliianie prirody poverkhnosti dispersnogo kremnezema na ego vzaimodeistvie s reproduktivnoi kletkoi i semennoi plazmoi krupnogo rogatogo skota.

The interaction of various disperse silica of I, II, III kind possessing various structure of surface groups (-OH; -O-CH2-CH2-O-CH2-CH2OH; -O-CH2-CH2-NH2 respectively) was investigated with some above membrane matrix polymers of bovine reproductive cells and seminal plasma (namely the surface proteins and carbohydrate polymers containing the N-acetyl-neuraminic acid (NANA) as terminal residue). Protein binding was preferentially observed for silica surface modified by aminoethoxy--and ethylene glycol groups and depended on concentration of silica in the mixture. It was found that biopolymers containing carbohydrate groups had larger affinity to I than to II or III. The binding value of I-III was 12-16% with respect to plasma proteins. Silicas I and II with -OH-groups on the surface absorb 17-21% N-ANA-containing polymers of bovine seminal plasma.

[Isolation and purification of proteolytic enzymes on organo-silica sorbents with immobilized gramicidin S]. / Vydelenie i ochistka proteoliticheskikh fermentov na organokremnezemnykh sorbentakh s immobilizirovannym gramitsidinom S.

Biospecific sorbents for affinity chromatography of proteolytic enzymes have been synthesized by attaching cyclopeptide antibiotic gramicidin S to organo-silica supports. It is shown possible to attach gramicidin S to the organo-silica supports using glutaric aldehyde, p-benzoquinone, soluble and insoluble carbodiimides. The sorbents prepared by these methods were successfully applied for the purification of the crude pepsin from horse gastric juice and proteolytic complex produced by Acremonium chrysogenum.

[The effect of an alpha-adrenoblocker and a calcium-channel blocker on the spontaneous tonus of an isolated blood-perfused artery]. / Vliianie al'fa-adrenoblokatora i blokatora kal'tsievykh kanalov na spontannyi tonus izolirovannoi arterii, øerfuziruemoi krov'iu.

The existence of spontaneous myogenic tone was shown on an experimental model of an isolated artery perfused "ex vivo" with blood from the rat donor. Administration of the alpha-adrenoblockers prasosine and yohimbine into the perfusion medium in the bath was followed by a 60% decrease in the myogenic tone. The nonspecific blocker of calcium channels CaCl2 decreased the rest of the tone by 15%. The remaining 20-25% of the initial myogenic tone was inhibited by sodium nitroprusside. Urethane (300 mg/kg) or nembutal (20 mg/kg) injected intravenously into the rat donor may lead to an increase or a decrease in the myogenic tone, respectively. The conclusion is made that the advantage of the experimental model proposed lies in the existence of the spontaneous myogenic tone of an arterial vessel depending on humoral catecholamines and some other vasoconstrictor factors.

Growth of peptide chains on silica in absence of amino acid access from without.

Changes in IR spectra during thermal treatment of chemisorption products of glycine and valine vapours on dehydrated silica surfaces have been studied. Peptide products were formed from these chemisorbed species. A scheme of peptide chain growth on the silica surface is suggested based on the idea of ester type "activated intermediates".

Evidence for an antihypertensive factor from the adrenal medulla of SHR modulating neurogenic vasoconstriction.

The aim of this study is to investigate some vasoactive properties of the blood of spontaneously hypertensive rats (SHR). Isolated segments of rat tail arteries obtained from normotensive rats (Wistar-Kyoto (WKY) and Wistar) were perfused with blood from conscious donor rats (WKY, Wistar or SHR). Alterations of the neurogenic constrictor responses (NCR) of the isolated segments evoked by electrical stimulation were studied. The amplitude of NCR of the isolated arteries was studied during perfusion with blood according to the perfusion scheme WKY1(1)-SHR1(2)-WKY1(3) and WKY1(1)-WKY2(2)-WKY1(3). The release of 3H-noradrenaline ([3H]-NA) from vascular sympathetic fibres was measured. The influence of adrenal demedullation on NCR was estimated. We have shown that NCR of isolated arteries decreased by 28.3 +/- 7.9% (P < 0.05 vs. WKY1(1)) during perfusion with blood from SHR (scheme WKY1(1)-SHR1(2)-WKY1(3)). In these experiments, release of [3H]-NA from sympathetic fibres of the artery segments decreased by 39.9 +/- 9.6% during the perfusion with blood from SHR vs. WKY1(1) (P < 0.05). Adrenal demedullation prevented the decrease of NCR during perfusion of the arteries with blood from SHR. In conclusion, the blood of SHR has some antihypertensive factor(s), which causes decrease of NCR in the tail artery from normotensive rats. This decline is accompanied by the decrease of release in [3H]-NA from the transmural sympathetic fibres and is abolished after adrenal demedullation of blood donor rats.

[The effect of dispersed silicon dioxide--aerosil A-300--on the growth of Saccharomyces cerevisiae yeasts]. / Vliianie dispersnogo dioksida kremniia--aérosila A-300 na rost drozhzhei Saccharomyces cerevisiae.

High-dispersed silicon dioxide--aerosil A-300 has been studied for its effect on the growth of yeast Saccharomyces cerevisiae. It is shown that at heterophase cultivation of these microorganisms under periodical conditions introduction of aerosil A-300 induces a decrease of the lag phase duration and an increase of the maximum specific growth rate and economic coefficient of the carbon substrate utilization. This high-dispersed material has exerted the similar effect under the conditions of chemostatic cultivation. Optimal parameters of this process are determined.