Interfacial activity of a novel family of polymeric surfactants

A novel series of polymeric surfactants based on carboxy methyl cellulose and alkyl poly(etheroxy) acrylate were synthesized by ultrasonic irradiation. These polymeric surfactants have exhibit excellent surface activity due to their unique structure. The influences of salt, alcohol and alkali on the interfacial activity of these polymeric surfactants were studied by interfacial tensiometery, dynamic laser scattering (DLS), UV spectroscope and environmental scanning electrical microscope (ESEM). The surface tension and interfacial tension (IFT) properties change little with NaCl added. The formed micelles shrink, their size becomes smaller. Alcohols cause the IFT to decrease a little because a small amount of free chains present in solution. Under the influence of added alkali, the IFT of the polymeric surfactants, in aqueous solution, decreases so much that sometimes it is less than 10⁻² mN/m. Using data from the equivalent alkane scan, one cannot draw the conclusion that the action of alkali with the acidic components in crude oil leads to the ultra-low IFT. The analyses by UV, DLS and ESEM show that the micelles formed by polymeric surfactants could be disaggregated or destroyed sharply by the action of alkali. So the size of micelles decreases greatly and the number of free chains increases. That more polymeric surfactants molecules move to the interface of oil/water and rearrange at the interface of oil/water is believed to be the main reason of the ultra-low IFT (10⁻³ mN/m) that is obtained.     

Simulations of the active transport of a neutral solute based on a kinase-channel-phosphatase topology

Simulations of coupled interactions involving two opposite enzymatic reactions, solute diffusions, and electrostatic interactions between membrane charges and charged solutes were conducted under a fixed kinase-channel-phosphatase (KCP) topology oriented from the outside to the inside of a porous membrane structure. Depending on the kinase and phosphatase locations, we recently demonstrated that an active transport of a phosphorylated substrate may occur via the opposite topology, that is, a PCK topology. The present analysis demonstrates that, under a KCP membrane topology, which also behaves as a specific ATP-dependent transporter, the active transport of a neutral substrate may occur. This analogous active transport appears to be dependent on the phosphatase location and on the membrane surface potentials. A broad analysis of the role played by the main parameters taken into account in the model was conducted in order to define precisely the physico-chemical conditions and the membrane topology needed for the highest active transports within the shortest time.     

Effect of using mixed ion-pairs on PVC-membrane electrodes for ephedrine

Mixed ion-pairs based on the use of ephedrinium (EPH)-TPB plus EPH-reineckate (II) and phenylephrine-TPB plus EPH-reineckate (III) were tried for use in plastic membranes. The results were compared to those of an EPH-reineckate (I) single ion-pair electrode. The Nernstian slopes were 50, 49 and 55 mV decade^–1 for membranes I, II and III, respectively. The linear concentration ranges were 10^–5–10^–1, 4.0 × 10^–5–10^–1 and 6.3 ×^–5–10^–1 M ephedrine. The detection limits were 4 ×^–6,10^–5 and 1.2 × 10^–5 M ephedrine for membranes I, II and III, respectively. The pH ranges were 4–9, 3–9 and 2–8 for I, II and III-membranes, respectively. Selectivity coefficient values for membrane II were better than those for membranes I and III. The effects of increasing KC1 concentration and temperature changes were explained for the three electrodes. The isothermal temperature coefficients were 0.00145, 0.0007 and 0.00055 V/ °C for electrodes I, II and III. Electrode III was applied for the determination of ephedrine in its pharmeaceutical preparations with an overall relative standard deviation range of 1.3–2.4% and an overall mean recovery value of 98.1%.     

Kinetics of epidermal growth factor/receptor binding on cells measured by total internal reflection/fluorescence recovery after photobleaching

Total internal reflection fluorescence (TIRF) microscopy is used to measure the dissociation kinetic rate of fluorescein-labeled epidermal growth factor from its specific receptors on the surface of intact but mildly fixed A431 human epidermoid cells in culture. Prior applications of TIRF microscopy have been limited to nonreceptor binding or to model membrane systems. The evanescent field excites fluorescence selectively at the surface of the cell proximal to the coverslip. Prismless epiillumination TIR is employed to avoid space limitations and is achieved by passing the excitation laser beam through a high (1.4)-aperture objective so that the light is incident at the glass/water interface beyond the critical angle. Long-term focus is maintained by a special feedback system. Of the possible effects that can influence the time course of the postbleach fluorescence recoveries—the EGF/receptor dissociation ratek ₂, the bulk solution diffusion rate of EGF, and the cell surface motion of the receptors—we infer that the dissociation ratek ₂ dominates. Several fitting schemes are compared and indicate the presence of a multiplicity of values fork ₂, ranging from about 0.05 to 0.004 s^–1, with an average value of about 0.012 s^–1. These results compare well with values previously obtained by radiolabel/washing techniques. The significance of the results in terms of kinetic models and the advantages of the TIRF technique for these sorts of measurements are discussed.     

Structure and microporous formation of cellulose/silk fibroin blend membranes: Part II. Effect of post-treatment by alkali

Blend membranes (RCF1) were prepared from mixture solution of cellulose and silk fibroin (SF) in cuoxam by coagulating with acetone–acetic acid (4:1 by volume). The blend membranes were subjected to post-treatment with 10% NaOH aqueous solution, and their structure and properties were characterized by FT-IR, X-ray diffraction, DSC, SEM and DMTA. In previous work, cellulose/SF blend membranes (RCF2) prepared by coagulating with 10% NaOH aqueous solution formed a microporous structure, in which the SF as a pore former was almost completely removed from the membrane. However, when the blend membranes RCF1 were immersed in 10% NaOH aqueous solution for post-treatment, a strong hydrogen bonding between cellulose and SF inhibited the removal of SF. Although alkali is a good solvent for SF, the blend membranes RCF1 such obtained from cellulose and SF were alkali resistant. The crystallinity and the mean pore size of the blend membranes slightly decreased with increasing post-treatment time. This work provided a cellulose/silk blend membrane, which can be used under alkaline medium.     

Supported liquid membrane separation of amine and amino acid derivatives with chiral esters of phosphoric acids as carriers

Studies on the possible use of phosphate and phosphonate esters bearing chiral menthol or nopol moieties as carriers for the transport of amines, amino acids, and amino acid esters through supported liquid membranes (SLM) are presented. Additionally, the enantioselectivity of the SLM transport of alkyl esters of aromatic amino acids and a non‐protein amino acid was also evaluated. It could be concluded that the extent of transport strongly depends on the hydrophobicity of the amino compound. Moreover, the carrier structure also influences the transport of those compounds through SLM: chiral phosphate and phosphonate esters appear to be poor or moderate carriers for enantioselective SLM transport of amino acids and their esters. The transport efficiency and selectivity is strongly dependent on the structure of both the transported compounds and the carrier. However, no meaningful relationship exists between these structural features and transportation or enantioselectivity.     

Electron paramagnetic resonance spin label titration: a novel method to investigate random and site-specific immobilization of enzymes onto polymeric membranes with different properties

The immobilization of biological molecules onto polymeric membranes to produce biofunctional membranes is used for selective catalysis, separation, analysis, and artificial organs. Normally, random immobilization of enzymes onto polymeric membranes leads to dramatic reduction in activity due to chemical reactions involved in enzyme immobilization, multiple-point binding, etc., and the extent of activity reduction is a function of membrane hydrophilicity (e.g. activity in cellulosic membrane?polysulfone membrane). We have used molecular biology to effect site-specific immobilization of enzymes in a manner that orients the active site away from the polymeric membrane surface, thus resulting in higher enzyme activity that approaches that in solution and in increased stability of the enzyme relative to the enzyme in solution. A prediction of this site-specific method of enzyme immobilization, which in this study with subtilisin and organophosphorus hydrolase consists of a fusion tag genetically added to these enzymes and subsequent immobilization via the anti-tag antibody and membrane-bound protein A, is that the active site conformation will more closely resemble that of the enzyme in solution than is the case for random immobilization. This hypothesis was confirmed using a new electron paramagnetic resonance (EPR) spin label active site titration method that determines the amount of spin label bound to the active site of the immobilized enzyme. This value nearly perfectly matched the enzyme activity, and the results suggested: (a) a spectroscopic method for measuring activity and thus the extent of active enzyme immobilization in membrane, which may have advantages in cases where optical methods can not be used due to light scattering interference; (b) higher spin label incorporation (and hence activity) in enzymes that had been site-specifically immobilized versus random immobilization; (c) higher spin label incorporation in enzymes immobilized onto hydrophilic bacterial cellulose membranes versus hydrophobic modified poly(ether)sulfone membranes. These results are discussed with reference to analysis and utilization of biofunctional membranes.     

Study on δ‐form complex in syndiotactic polystyrene–organic molecules systems. IV. Formation of complexes with a mixture of solvents and structural changes during the sorption of solvents by syndiotactic polystyrene mesophase membranes

The syndiotactic polystyrene (sPS) δ form was crystallized from mixtures with different compositions of p‐chlorotoluene–chlorobenzene (p‐CT–CB) and p‐chlorotoluene–1,1,2‐trichloroethane (p‐CT–TCE). The presence of the δ form and TTGG helical conformation was confirmed by Fourier transform infrared and wide‐angle X‐ray diffraction (WAXD) analyses. In sPS/p‐CT–CB and sPS/p‐CT–TCE δ‐form membranes, the relative absorbance (RA) of the p‐chlorotoluene (p‐CT) solvent peak was very high even at very low concentrations of p‐CT in comparison with the RA of higher concentrations of chlorobenzene (CB) or 1,1,2‐trichloroethane (TCE) in the mixtures. However, the RAs of both CB and TCE solvent peaks decreased with decreasing concentrations of CB and TCE in the mixtures. A negligible decrease in the RA of the TTGG helical content was observed with a decreasing concentration of CB or TCE. The WAXD results showed that the 2θ peak positions of the [010] and [ 10] planes of the sPS/p‐CT–CB and sPS/p‐CT–TCE δ‐form membranes appeared in the same position and were almost equal to those of the sPS–p‐CT δ‐form membrane. The mesophases of the sPS–p‐CT [p‐CT (A‐M)] and sPS–TCE [TCE (A‐M)] membranes were used for the sorption studies with different concentrations of various solvents. The sorption amount of aromatic solvents by both p‐CT (A‐M) and TCE (A‐M) mesophase membranes was higher than that of aliphatic solvents, regardless of the size, shape, and nature of the molecular cavity. The 2θ peak of the [010] plane of the sPS membranes slowly approached the original δ‐form value when the sPS mesophase membranes were immersed in various solvents of different concentrations for 48 h. The shifting of the 2θ peak of the [010] plane to the original δ form depended on the nature and concentration of the immersion solvents. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2380–2387, 2005     

Vibrational spectroscopic encoding of polystyrene-based resin beads: converting the encoding peaks into barcodes

A detailed approach is described for the vibrational spectroscopic encoding of polystyrene-based resin beads by converting the infrared absorption peaks suitable for encoding (encoding peaks) into barcodes. Based on combining the FT-IR measurements and the quantum-chemical computations, the vibrational characteristics of p-tert-butylstyrene monomer, polystyrene and poly(p-tert-butylstyrene) resin beads are analyzed, which are helpful for the selection of encoding peaks. The vibrational spectroscopic encoding of polystyrene-based resin beads could be obtained by converting the wavenumber, intensity and full width at half maximum (FWHM) of the encoding peaks into barcodes automatically through a computer program designed in our laboratory.     

聚苯乙烯键合麻黄碱-Co(Ⅱ)络合物对烯烃环氧化反应的催化作用

聚苯乙烯键合麻黄碱 Ｃｏ（Ⅱ）络合物对烯烃环氧化反应的催化作用刘庆艳刘必前何纪纲（中国科学院化学研究所北京１０００８０）关键词环氧化，分子氧，烯烃，醛，高分子催化剂烯烃的环氧化反应是将烯烃进行氧化转化的重要反应［１］．由于高分子催化剂具有与反应...