Characterization of internal lipids from wool

The internal lipids of wool were isolated after solubilizing the wool keratin with a mixture of papain and dithioerythritol 1.4. Thin layer chromatography of the internal lipids was applied to classify the extracted components. The internal wool lipids gave 11 spots of which some were identified as cholesterol and free fatty acids, C-16 and C-18 being predominant. A very small amount of triglycerides and cholesterol esters were also found. A characteristic difference between internal wool lipids and wool wax appears to be the limited number of well defined components of which free cholesterol and fatty acids constitute the main bulk. Furthermore another feature of keratin membrane lipids is the extremely reduced phospholipid: cholesterol ratio of 0.3. The internal lipids originate mainly from the cell membrane complex of the fiber. The existence of a chemically modified bilayer membrane structure without the essential phospholipids must be taken into consideration.     

The effect of internal lipids on the water sorption kinetics of keratinised tissues

Water has a large influence on the properties of keratinised tissues. The water diffusion properties of keratinised tissues are known to be governed by the cell membrane complex, which is mainly composed of internal lipids. The main aim of this work was to characterise the differences in the water sorption and desorption behaviour of human hair and stratum corneum (SC) both with and without internal lipids. Absorption and desorption curves were obtained using a thermogravimetric balance equipped with a controlled humidity chamber. The results demonstrate that the role of the intercellular lipids in the SC is more marked than in hair, which is likely due to the greater amount of lipids present in its structure. Therefore, lipid structures in the SC are essential both to prevent changes in the water-holding capacity of the skin and to maintain the water permeability of the SC.     

A study of anisotropic water self-diffusion and defects in the lamellar mesophase

The correlation of molecular diffusion coefficients obtained via a novel two-dimensional pulsed gradient spin-echo (PGSE) NMR method has been shown to reveal detailed structural information on the mesophases of lyotropic liquid crystals. A four-component system containing both nonionic (pentaethylene glycol monododecyl ether) and ionic (sodium dodecyl sulfate) surfactants, water, and decane was prepared and left to equilibrate. In the temperature region around 309 K, a lamellar mesophase forms. A two-dimensional Laplace inverse transformation was performed on the (gammadeltag)2(delta - delta/3) domain data to separate any multiexponential behavior that resulted from local anisotropy. The results of the double PGSE experiment with contiguous gradient pulse pairs, applied both collinearly and orthogonally, clearly show the presence of local anisotropic self-diffusion of the water molecules and suggest a preferred orientation of the lamellae. Information about defects/domain size was obtained by the insertion of a mixing time (t(m)') between the successive gradient pulse pairs. This work highlights the value of this new NMR correlation method in the study of surfactant systems.     

Influence of ionic charges on the bilayers of lamellar phases

The influence of ionic charges on the mesophases in the ternary system of C(12-16)E(6) (LA 070), ethylhexylglycerid (EHG), and water was studied. The charge was introduced by adding the ionic surfactant SDS (sodium dodecyl sulfate). The single lamellar phase (5 wt % LA 070 and 240 mM EHG in water) yields a bluish homogeneous solution. With the addition of SDS, the samples become more and more clear. Rheology measurements indicate that increased charge density increases the storage modulus G', and the lamellar phases show typical behavior of a viscoelastic fluid with a yield stress at higher SDS concentration. SAXS measurements show that the interlamellar distance D decreases with SDS concentration. The addition of ionic surfactants suppresses the Helfrich undulations, flattens the bilayers, and decreases interbilayer spacing due to electrostatic repulsions of the ionic surfactant head groups. Furthermore, the L(alpha) phase transforms into vesicle phases as the SDS concentration is increased. Second, it is shown that with added NaCl electrolyte the phase with charged surfactant behaves again in the same way as the initial uncharged system. The addition of salt screens the electrostatic interaction, which leads to a higher flexibility of the bilayers and a decrease of the storage modulus G'. Theoretical calculations show that the shear moduli of the L(alpha) phases are much smaller than the osmotic pressure of the systems. Several models are proposed for the explanation of the shear moduli. The model due to Lekkerkerker for the electric contribution of the bending constant of the bilayer seems to yield good results for the transition to vesicles.     

Flip rearrangement in the water pentamer: Analysis of electronic structure

Tunneling pathways of the flip rearrangement between permutation-inversion isomers corresponding to the energetically degenerate global energy minima of (H₂O)₅ are analyzed in terms of the electronic structure. We demonstrate that charge density-based scalar measures quantify the responses of the bonding to the flip rearrangement and we discovered a high degree of continuity of the values that depend on the presence of the sliding motion of the bond critical point relative to the oxygen atom. The scalar measures can distinguish the pairs of permutation-inversion isomers everywhere except at the transition state due to the asymmetrical energy barrier; however, they cannot determine the most and least facile directions of the flip rearrangement. The vector or directional character of the two sides of the pathway is captured by the stress tensor trajectories constructed in a non-Cartesian space, defined by the variation of the position of the bond critical point. The stress tensor trajectories are presented in terms that enable bond-flexing, bond-twist, and bond-anharmonicity of the flip rearrangement between permutation-inversion isomers to be quantified. The stress tensor trajectories can distinguish the isomers at the transition state and demonstrate that the clockwise and counter-clockwise directions of the flip rearrangement are the most and least facile respectively.     

Influence of 1-alkyl-3-methylimidazolium tetrafluoroborate on the lamellar liquid crystal formed by tetraethylene glycol lauryl ether and water

Lyotropic liquid crystals (LLCs) formed in tetraethylene glycol lauryl ether–water system by the addition of 1-alkyl-3-methylimidazolium tetrafluoroborate ([C _n Mim][BF₄], n?=?2, 4, 6, 8, 10) are characterised by polarised optical microscopy and small-angle X-ray scattering techniques. A small number of [C _n Mim][BF₄] molecules can be solubilised in the liquid crystal without changing the lamellar type. These imidazolium salts are considered as an ideal kind of modifiers for the ordered structure. With different lengths of alkyl chains, [C _n Mim][BF₄] molecules appear in various domains of ordered assemblies: in the water layer for [C₂Mim][BF₄], in the water layer as well as in the polar domain for [C₄Mim][BF₄] and in the apolar domain for the other imidazolium salts with long alkyl chains. Diverse distributions of [C _n Mim][BF₄] molecules in the inner structure bring about their specific influence on the lamellar phase. These results enlighten the use of diverse alkyl-substituted imidazolium salts in modulating LLC and other assemblies and also enrich the aggregation behaviour of these assemblies.     

Dielectric properties of wool and horn containing absorbed water

Summary The dielectric properties of wool containing 0→30% H₂O have been examined for the temperature range −90→22 °C. An absorption peak due to the orientation of bound water molecules has been studied and found to be unlike ice or liquid water. Other absorption bands were found;Ω due to interfacial polarisation;α′ due to main chain motion;β due to localised chain motion andδ of unknown origin. For each of these bands the distribution of relaxation times and the activation enthalpies have been obtained.

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Zusammenfassung Das dielektrische Verhalten von 0–30% Wasser enthaltender Wolle wurde zwischen −90 bis +22 °C untersucht. Ein Absorptionsmaximum, welches anhand der Orientierung der gebundenen Wassermoleküle bestehend, wurde eingehend untersucht und nicht als Eis oder (flüssiges) Wasser befunden. Weitere Absorptionsbanden wurden beobachtet;Ω von der Zwischenphasenpolarisation resultierend,α′ von der Hauptkettenbewegung,β von der Bewegung lokalisierter Ketten undσ von unbekannter Herkunft. Die Verteilung der Relaxationszeiten und die Aktivierungsenthalpie wurden für die einzelnen Banden erhalten.

     

Structural fluctuations in the lamellar phase of sodium decyl sulphate/decanol/water

We present a neutron scattering study of oriented samples for the lamellar phase of the ternary mixture sodium decyl sulphate/1-decanol/water. Diffuse scatterings are observed, around the Bragg reflections and away from them, which show that the structure of this lamellar phase deviates from the periodic stacking of infinite homogeneous lamellae of water and amphiphilic molecules usually proposed for the structure of lamellar phases. The nature of this deviation evolves with the soap/decanol ratio, according to the location of the sample in the lamellar domain of the phase diagram. In the middle of the domain the deviation relates to the organization of the lamellar stacking, without apparent modification of the structure of the lamellae of amphiphiles. Moving away from the middle, for higher soap/decanol ratios, the structure of the lamellae appears to be randomly perturbed, eventually by the presence of a few water regions piercing them. When the boundary of the lamellar domain is approached, for still higher soap/decanol ratios, the density of these peturbations increases and they start to be correlated over limited distances, within the lamellae and from lamella to lamella. The local symmetry of these short range correlations is such that these perturbations may be seen as structural fluctuations which may be seen as precursors of the transformation of the lamellar phase into a neighbouring phase on the phase diagram. This phenomenon is discussed briefly in relation to the structural fluctuations of the relative concentrations of sodium decyl sulphate and decanol within the aggregates.     

Enantiospecific photochemical carbon skeletal rearrangement of Morita-Baylis-Hillman products in water

Asymmetric carbon skeletal rearrangements of Morita-Baylis-Hillman products, α-hydroxymethylenones, under photochemical irradiation in water are described, wherein the asymmetric induction mechanism is discussed in detail.     

Proteins, lipids, and water in the gas phase

Evidence from mass‐spectrometry experiments and molecular dynamics simulations suggests that it is possible to transfer proteins, or in general biomolecular aggregates, from solution to the gas‐phase without grave impact on the structure. If correct, this allows interpretation of such experiments as a probe of physiological behavior. Here, we survey recent experimental results from mass spectrometry and ion‐mobility spectroscopy and combine this with observations based on molecular dynamics simulation, in order to give a comprehensive overview of the state of the art in gas‐phase studies. We introduce a new concept in protein structure analysis by determining the fraction of the theoretical possible numbers of hydrogen bonds that are formed in solution and in the gas‐phase. In solution on average 43% of the hydrogen bonds is realized, while in vacuo this fraction increases to 56%. The hydrogen bonds stabilizing the secondary structure (α‐helices, β‐sheets) are maintained to a large degree, with additional hydrogen bonds occurring when side chains make new hydrogen bonds to rest of the protein rather than to solvent. This indicates that proteins that are transported to the gas phase in a native‐like manner in many cases will be kinetically trapped in near‐physiological structures. Simulation results for lipid‐ and detergent‐aggregates and lipid‐coated (membrane) proteins in the gas phase are discussed, which in general point to the conclusion that encapsulating proteins in “something” aids in the conservation of native‐like structure. Isolated solvated micelles of cetyl‐tetraammonium bromide quickly turn into reverse micelles whereas dodecyl phosphocholine micelles undergo much slower conversions, and do not quite reach a reverse micelle conformation within 100 ns.

     

Rapid determination of cobalt-60 in sea water with steel wool adsorption

A rapid adsorption method has been developed to determine the⁶⁰Co content in sea water samples. The⁶⁰Co activity is concentrated by filtering the water sample through an adsorption column of steel work. A 60-liter sample can be processed in 1 h with 95% adsorption efficiency.     

Influence of protease on dyeing of wool with acid dyes

The application of enzymes in the wool dyeing process is an important research goal in order to reduce the environmental impact and costs of this finishing process. The work has focused on the possibility of reducing the temperature of conventional dyeing, using an enzymatic pretreatment with a neutral protease to improve the diffusion of the dye into the fibers. After the identification of the optimal dyeing process, the study goes on transferring the method to an industrial application. For this reason the influence of a leveling agent added to the dyeing bath was considered and further tests with an industrial dyeing recipe were performed. In order to evaluate possible fiber damage, samples treated with enzyme were observed by scanning electron microscopy (SEM) and analyzed by gel electrophoresis (SDS-PAGE). Moreover, the variation of tensile strength and elongation of dyed samples were determined. In addition, color fastness to domestic laundering, perspiration and rubbing were carried out. Finally, color measurements and fiber section analysis were performed. The results show the possibility, thanks to the pretreatment with the investigated enzyme, to obtain a homogeneous and solid dyeing on fibers maintaining good mechanical properties, already working at 85°C instead of 98°C currently used in industry.      

Additive-assisted Rupe rearrangement of 1-ethynylcyclohexan-1-ol in near-critical water

We performed the Rupe rearrangement of 1-ethynylcyclohexan-1-ol in near-critical water to study the reaction under high temperature conditions. The final product thus obtained was primarily 1-cyclohexen-1-ylethanone which was identified by GC-MS. The influences of reaction time, temperature, and initial reactant-to-water ratio on the yield of 1-cyclohexen-1-ylethanone were examined. The yield of 1-cyclohexen-1-ylethanone was 49 % in pure water at 260°C for a reaction time of 60 min. However, when additives such as ZnSO₄, FeCl₃, and NaHSO₄, respectively, were introduced to the water to investigate the effect of salts on the Rupe rearrangement reaction, the yield increased markedly to as much as 88 % in 5 mole % NaHSO₄ aqueous solution under the same conditions. The catalytic ability of the additives decreased in order: NaHSO₄, FeCl₃, ZnSO₄. On the basis of these results, a possible reaction mechanism of the Rupe rearrangement of 1-ethynylcyclohexan-1-ol in near-critical water was proposed.     

Influence of the method of isolating lipids on their composition

Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 623–624, July–August, 1995. Original article submitted November 7, 1994.     

Photocatalyst of lamellar aggregates of RuOx-loaded perovskite nanosheets for overall water splitting

Overall photocatalytic splitting of water was achieved using a restacked aggregate of exfoliated nanosheets of Ca(2)Nb(3)O(10), which was synthesized by flocculating a colloidal suspension of the nanosheets with alkali-metal ions and a trace amount of ruthenium red, a trinuclear complex of ([(NH(3))(5)Ru-O-Ru(NH(3))(4)-O-Ru(NH(3))(5)]Cl(6). The as-restacked material showed the evolution of H(2) gas from water immediately after UV irradiation, while O(2) evolution was observed only after some induction time, which may be understood by the possible oxidation of ruthenium red to RuO(x) in the initial stage. The restacked aggregate, which was heated at 773 K to convert the ruthenium complex to the oxide, underwent the stoichiometric splitting of water upon initiation of UV illumination, verifying the hypothesis. Total decomposition of water could not be attained with the bulk layered host of KCa(2)Nb(3)O(10) as well as its RuO(x)-loaded forms obtained via a conventional impregnation procedure. This clearly demonstrates the effectiveness of the present exfoliation-restacking route for loading RuO(x) to improve and enhance the photocatalytic activities of layered semiconducting materials. A homogeneous distribution of RuO(x)was suggested by XPS depth-profile analysis on the materials obtained through the exfoliation-restacking process.     

Chemical waves and pattern formation in the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/water lamellar system

The present work deals with the spatially extended oscillatory Belousov Zhabotinsky reaction-diffusion system carried out in an anisotropic environment of phosphatidylcholines/water binary system, which presents layered aqueous domains separated by lipid bilayers. We report the occurrence of stable Turing patterns, spiral waves, and other exotic structures in phospholipids bilayers that are generally used as a models for cell plasma membranes.     

Interaction of nitrophenols with lipids at the air/water interface

The uptake of ortho and para nitrophenol to charged and neutral lipid monolayers spread at the air/solution interface was studied by reflection spectroscopy. The adsorption characteristics of the two nitrophenols have been studied by measuring the surface pressure and surface potential as a function of molecular area of the different lipid monolayers in the presence of nitrophenols in the subphase. The results have been interpreted in terms of the electrostatic interaction between the negatively charged dissociated phenolate ions and the positively charged head group of dioctadecyldimethylammonium bromide monolayers.