Analysis of the Amino Acids of Soy Globulins by AOT Reverse Micelles and Aqueous Buffer

The 7S and 11S globulins from soybean proteins using reverse micelle and aqueous buffer extraction methods were characterized by using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and scanning electron microscope (SEM), and their amino acid compositions were also evaluated. SDS-PAGE did not show electrophoretic differences between 7S and 11S globulin subunits with two extraction methods. SEM analysis showed that the AOT reverse micelle processing of 7S and 11S globulins induced a reduction of droplet size. Some individual amino acid contents of 7S and 11S globulins using two extraction methods were different, some were similar. In all the samples, the glutamic acid, aspartic acid, and leucine were the dominant amino acids while the cystine and methionine were the first-limiting amino acids. The proportion of essential amino acids to the total amino acids (E/T) of the 7S globulin from aqueous buffer and reverse micelles was similar. While significant differences were obtained in the proportion of E/T of the 11S globulin.     

Simple and rapid characterization of soybean cultivars by perfusion reversed-phase HPLC: application to the estimation of the 11S and 7S globulin contents

A perfusion RP HPLC method enabling the separation of soybean proteins in an analysis time lower than 3 min has been used to obtain the chromatographic profiles of different soybean cultivars. The chromatograms obtained for each soybean variety presented clear differences that justified the potential use of this method for cultivar characterization. The area percentages obtained were employed as variables for cluster and principal components analysis of these soybeans. The application of these multivariate methods enabled the grouping of the soybeans in different categories. The protein fractions obtained from these soybeans by the application of a fractionation method were also analyzed. The chromatographic profiles obtained enabled the assignment of peaks to the main soybean proteins (7S and 11S globulins). These data were used for the estimation, for the first time, of the 7S and 11S globulin contents in soybean cultivars.     

An Experimental Study on the Relationship between the Physical Properties of CTAB/Hexanol/Water Reverse Micelles and ZrO2-Y2O3 Nanoparticles Prepared

Based on the studies of their physical properties such as aqueous solution uptake, electric conductivity, and microstructure, CTAB/hexanol/water reverse micelles (CTAB, cetyltrimethyl ammonium bromide) were used to prepare ZrO2-Y2O3 nanoparticles. The relationship between the micelle microstructure and size, morphology, and aggregate properties of particles prepared was also investigated. It has been found that with high CTAB concentration ([CTAB] > 0.8 mol/l), the reverse micelles can solubilize a sufficient amount of aqueous solution with high metallic ion concentration ( approximately 1.0 mol/L), while the microstructure of the reverse micelles keeps unchanged. The most important factor affecting the size and shape of reverse micelles was found to be the water content w0 (w0, molar ratio of water to surfactant used). When both the CTAB concentration and the w0 values are low, the diameters of reverse micelles are below 20 nm, and the ZrO2-Y2O3 particles prepared are also very small. However, the powders obtained were found to form a lot of aggregates after drying and calcination. High CTAB concentration, high w0 value, and high metallic ion concentration in the aqueous phase for high powder productivity were found to be the suitable compositions of reverse micelles for preparing high-quality ZrO2-Y2O3 nanoparticles. Under these conditions, the reverse micelles are still spherical in shape even the reverse micellar system is nearly saturated with aqueous solutions. These reverse micelles were found to have a diameter of between 60 and 150 nm and the ZrO2-Y2O3 particles prepared therefrom range from 30 to 70 nm with spherical shape and not easy to form aggregates. Copyright 1999 Academic Press.     

C-N-S-TiO2光催化剂的制备、表征及其性能

以钛酸四丁酯为钛源、功能生物小分子胱氨酸为掺杂剂,采用溶胶-凝胶法同步合成了C-N-S-TiO2光催化剂,利用XRD、XPS、FT-IR和DRS等测试技术对样品的结构及物化性能进行了表征。XRD和DRS分析表明,共掺杂抑制了TiO2晶粒的生长,提高了晶相转变温度,且C-N-S-TiO2样品的吸收带边明显"红移",光吸收范围一直延长至800 nm左右。XPS分析结果显示,C-N-S-TiO2样品表面产生了杂质能级,C、S元素分别取代部分晶格Ti4+以CO23-和S6+形式存在;而N峰呈宽化状态,以O—Ti—N和Ti—O—N键存在,且样品表面羟基含量明显增加。以罗丹明B染料为模型污染物,考察了该催化剂的可见光催化活性。结果表明,与P25 TiO2比较,C-N-S-TiO2光催化剂活性得到改进,C-N-S-TiO2光催化剂在470～800 nm波长下辐射120 min后对罗丹明B的降解率可高达83%。     

硅胶与高岭土的润湿性及荧光和驱油研究

利用Washburn方程测量固体粉末的润湿性,研究了十二烷基苯磺酸钠(SDBS)水溶液在硅胶及高岭土两种固体粉末表面上的接触角,用荧光猝灭法测定了SDBS在水溶液里的胶束平均聚集数。并由此探讨了十二烷基苯磺酸钠水溶液在固体粉末表面的润湿性,表面活性剂的临界胶束浓度(CMC)与表面含油粉末脱油率的关系。     

Structural and elemental investigations of isolated aquatic humic substances using X-ray photoelectron spectroscopy

Structural and elemental investigations of aquatic humic substances (HS) by means of X-ray photoelectron spectroscopy (XPS) are described. For that purpose small amounts (10-50 microg) of dissolved reference HS, which were characterized within the German research program DFG-ROSIG, were dried as thin films on small pieces of a high-purity silicon wafer. The photoelectrons from such HS layers exhibited characteristic signals of carbon C1s, nitrogen N1s, oxygen O1s and sulfur S2s, which could be fitted by Gaussian curves and used for the quantification of various moieties of HS: carbon (C-C, C-O, C=O, O=C-O), oxygen (C-O, C=O), nitrogen (C-N, C-N+) and sulfur. Moreover, by adding up the element signals of the HS samples their elemental composition of C, O, N and S was assessed. A comparison of the data based on solution state NMR and conventional elementary analysis revealed a satisfactory accuracy with those obtained by XPS.     

用气相色谱-原子发射光谱法检测VX、Bz及其降解产物

应用气相色谱－原子发射光谱（ＧＣ－ＡＥＤ）同时检测Ｓ－（２－二异丙基氨乙基）甲基硫直膦酸乙酯（ＶＸ）、二苯羟乙酸－３－喹咛环酯（ＢＺ）战剂及其降解产物等５种化合物,得取了Ｃ、Ｈ、Ｓ、Ｎ、Ｏ、Ｐ６种元素色谱图,通过选择合适的检测元素,其检出限ＶＸ为１５．６ｍｇ／Ｌ,Ｂｚ为１６．７９ｍｇ／Ｌ,二异基氨基乙太醇为３．０２ｍｇ／Ｌ,３－羟基喹咛为２８．４０ｍｇ／Ｌ,二苯羟乙酸甲酯为３１．７８ｍｇ／Ｌ,定量     

碳氟醇对阳离子表面活性剂表面活性及胶团反离子结合度的影响

用表面张力及电动势法研究了C₁₀H₂₁N(CH₃)3Br、C₁₂H₂₅N(CH₃)3Br与C₃F₇CH₂OH混合水溶液的表面与胶团性质。结果表明,对于阳离子表面活性剂,C₃F₇CH₂OH的加入一方面增加表面活性,另一方面降低胶团反离子结合度。后者不同于阴离子表面活性剂/C₃F₇CH₂OH混合体系,可归因于C₃F₇CH₂OH略有酸性,因而具备一些类似阴离子表面活性剂的性质。     

Formation of a N2-dG:N2-dG carbinolamine DNA cross-link by the trans-4-hydroxynonenal-derived (6S,8R,11S) 1,N2-dG adduct

Michael addition of trans-4-hydroxynonenal (HNE) to deoxyguanosine yields diastereomeric 1,N(2)-dG adducts in DNA. When placed opposite dC in the 5'-CpG-3' sequence, the (6S,8R,11S) diastereomer forms a N(2)-dG:N(2)-dG interstrand cross-link [Wang, H.; Kozekov, I. D.; Harris, T. M.; Rizzo, C. J. J. Am. Chem. Soc.2003, 125, 5687-5700]. We refined its structure in 5'-d(G(1)C(2)T(3)A(4)G(5)C(6)X(7)A(8)G(9)T(10)C(11)C(12))-3'·5'-d(G(13)G(14)A(15)C(16)T(17)C(18)Y(19)C(20)T(21)A(22)G(23)C(24))-3' [X(7) is the dG adjacent to the C6 carbon of the cross-link or the α-carbon of the (6S,8R,11S) 1,N(2)-dG adduct, and Y(19) is the dG adjacent to the C8 carbon of the cross-link or the γ-carbon of the HNE-derived (6S,8R,11S) 1,N(2)-dG adduct; the cross-link is in the 5'-CpG-3' sequence]. Introduction of (13)C at the C8 carbon of the cross-link revealed one (13)C8→H8 correlation, indicating that the cross-link existed predominantly as a carbinolamine linkage. The H8 proton exhibited NOEs to Y(19) H1', C(20) H1', and C(20) H4', orienting it toward the complementary strand, consistent with the (6S,8R,11S) configuration. An NOE was also observed between the HNE H11 proton and Y(19) H1', orienting the former toward the complementary strand. Imine and pyrimidopurinone linkages were excluded by observation of the Y(19)N(2)H and X(7) N1H protons, respectively. A strong H8→H11 NOE and no (3)J((13)C→H) coupling for the (13)C8-O-C11-H11 eliminated the tetrahydrofuran species derived from the (6S,8R,11S) 1,N(2)-dG adduct. The (6S,8R,11S) carbinolamine linkage and the HNE side chain were located in the minor groove. The X(7)N(2) and Y(19)N(2) atoms were in the gauche conformation with respect to the linkage, maintaining Watson-Crick hydrogen bonds at the cross-linked base pairs. A solvated molecular dynamics simulation indicated that the anti conformation of the hydroxyl group with respect to C6 of the tether minimized steric interaction and predicted hydrogen bonds involving O8H with C(20)O(2) of the 5'-neighbor base pair G(5)·C(20) and O11H with C(18)O(2) of X(7)·C(18). These may, in part, explain the stability of this cross-link and the stereochemical preference for the (6S,8R,11S) configuration.     

Structural and elemental investigations of isolated aquatic humic substances using X-ray photoelectron spectroscopy

Structural and elemental investigations of aquatic humic substances (HS) by means of X-ray photoelectron spectroscopy (XPS) are described. For that purpose small amounts (10–50 μg) of dissolved reference HS, which were characterized within the German research program DFG-ROSIG, were dried as thin films on small pieces of a high-purity silicon wafer. The photoelectrons from such HS layers exhibited characteristic signals of carbon C1s, nitrogen N1s, oxygen O1s and sulfur S2s, which could be fitted by Gaussian curves and used for the quantification of various moieties of HS: carbon (C-C, C-O, C=O, O=C-O), oxygen (C-O, C=O), nitrogen (C-N, C-N⁺) and sulfur. Moreover, by adding up the element signals of the HS samples their elemental composition of C, O, N and S was assessed. A comparison of the data based on solution state NMR and conventional elementary analysis revealed a satisfactory accuracy with those obtained by XPS.     

Comparison of surface and bulk doping levels in chemical polypyrroles of low,medium and high conductivity

Chemical polypyrroles (PPys) of low (σ < 75 S/cm), medium (75 < σ < 200 S/cm) and high electrical conductivity (σ > 200 S/cm) having chloride dopants have been investigated by XPS, chloride ion‐selective electrode (ISE) measurements and high‐resolution termogravimetric analysis (TGA). The average surface doping level in these PPys was 0.28 ± 0.03 as determined from deconvoluted XPS N 1s, Cl 2p and C 1s spectra by using the well‐established N⁺/N and Cl^?/N atomic ratios as well as a new ratio denoted as Cα*/Cα_Total. This new ratio provides an estimation of the relative amount of α‐C atoms in charged pyrrole units per total α‐C atoms. The average bulk doping level in these materials was 0.31 ± 0.02 from direct chloride ISE measurements. High‐resolution TGA was employed for the first time in the determination of the amount of hydrogen chloride evolved from the PPy samples during degradation at high temperatures. The resulting average bulk doping level by TGA was 0.30 ± 0.04 for these PPys, in very good agreement with the ISE results. Since surface and bulk doping levels are almost identical for the PPys of low, medium and high conductivity, the differences in conductivity between samples have been attributed to differences in conjugation length among them. For PPy of high conductivity (σ = 288 S/cm), a conjugation length 2.6 times higher than that of PPy of low conductivity (σ = 29 S/cm) has been calculated. Copyright © 2006 John Wiley & Sons, Ltd.     

Catalytic performance of lignin peroxidase in a novel reverse micelle

To enhance the catalytic activity of lignin peroxidase (LiP) in a reverse micelle, a synthesized two-tail nonionic surfactant N-gluconyl glutamic acid didecyl ester (GGDE) was used to formulate a novel reverse micelle. Based on the LiP catalyzed oxidation of veratryl alcohol (VA) in this novel GGDE/TritonX-100-cyclohexane-H(2)O reverse micelle, the effects of the size of the reverse micelle, the buffer pH, and the concentration of H(2)O(2) on the catalytic activity of LiP were investigated. Under the optimized conditions, the catalytic efficiency of LiP in the GGDE/TritonX-100 reverse micelle was 40 times higher than that in the AOT reverse micelle. The full expression of catalytic activity of LiP in this medium was mainly due to the lack of electrostatic interaction between LiP and the head group of GGDE and TritonX-100 and to the size fit between LiP and the inner water cavity of the reverse micelle.     

Thermal transition and decomposition properties of pH- and phosphate-induced defatted soybean meals

Defatted soybean meal is a popular raw material for soybean protein products. Thermal properties of soybean meal, which is vital for its application in extruded texturized soybean protein, are influenced by storage time and processing temperature. Thus, low-temperature defatted soybean meal (LSM), low-temperature defatted one-year-stored-soybean meal (LSSM) and high-temperature defatted soybean meal (HSM) were selected to investigate the thermal transition and decomposition properties by pH induction with phosphate using differential scanning calorimetry and thermal gravimetric analysis. The results showed that the peak temperature of 11S (glycinin) in phosphate buffer at pH 7 is significantly higher than that in deionized water. Break temperatures of LSM and LSSM at around 110 °C in deionized water are significantly higher than that in phosphate buffer at pH 7; however, the break temperature of LSM at 300 °C in deionized water is significantly lower than that in phosphate buffer at pH 7. In contrast to LSM, ?H of LSSM in phosphate buffer at pH 7 is significantly lower than in deionized water. It is thus concluded that phosphate stabilizes the soybean protein quaternary structure, enhances protein–protein interactions and weakens protein-water interactions. Protein association occurs in LSSM during soybean storage, while HSM protein appears to be insensitive to these changes.     

聚四氟乙烯微粉辐照接枝苯乙烯的XPS研究

聚四氟乙烯微粉辐照接枝苯乙烯的ＸＰＳ研究许观藩，罗云霞，杨弘（中国科学院长春应用化学研究所，长春，１３００２２）关键词聚四氟乙烯，苯乙烯，表面接枝，ＸＰＳ用辐照方法在疏水性高聚物材料表面接枝聚合亲水性单体，可以达到改性的目的．文献中所用的高聚物材料包...     

A Combined Experimental and Theoretical Electron Density Study of Intra‐ and Intermolecular Interactions in Thiourea S,S‐Dioxide

The thiourea S,S‐dioxide molecule is recognized as a zwitterion with a high dipole moment and an unusually long C? S bond. The molecule has a most interesting set of intermolecular interactions in the crystalline state—a relatively strong O???H? N hydrogen bond and very weak intermolecular C???S and N???O interactions. The molecule has C_s symmetry, and each oxygen atom is hydrogen‐bonded to two hydrogen atoms with O???H? N distances of 2.837 and 2.826 Å and angles of 176.61 and 158.38°. The electron density distribution is obtained both from Xray diffraction data at 110 K and from a periodic density functional theory (DFT) calculation. Bond characterization is made in terms of the analysis of topological properties. The covalent characters of the C? N, N? H, C? S, and S? O bonds are apparent, and the agreement on the topological properties between experiment and theory is adequate. The features of the Laplacian distributions, bond paths, and atomic domains are comparable. In a systematic approach, DFT calculations are performed based on a monomer, a dimer, a heptamer, and a crystal to see the effect on the electron density distribution due to the intermolecular interactions. The dipole moment of the molecule is enhanced in the solid state. The typical values of ρ_b and H_b of the hydrogen bonds and weak intermolecular C???S and N???O interactions are given. All the interactions are verified by the location of the bond critical point and its associated topological properties. The isovalue surface of Laplacian charge density and the detailed atomic graph around each atomic site reveal the shape of the valence‐shell charge concentration and provide a reasonable interpretation of the bonding of each atom.     

Fabrication of Hexagonal Boron Nitride Nanosheets by Using a Simple Thermal Exfoliation Process

A simple and inexpensive method to exfoliate boron nitride powder to form boron nitride nanosheets (BNNSs) with few layers was achieved by using a physically thermal process. The obtained BNNSs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), IR spectroscopy, and Raman spectroscopy. The size distribution of the sheets and average sheet size is in the range of 80–380 nm and 200±62 nm, respectively, and the pure phase h‐BN products were confirmed. XPS result showed the B/N atomic ratio to be 0.99. In addition, the BNNSs can well disperse in aqueous solution to form a cloudy suspension and importantly, can remain suspended for 1 month without precipitate, which would have good potential in a wide range of applications.     

Sol-gel preparation and spectroscopic study of the pyrophanite MnTiO_3 nanoparticles

Titanium dioxide (TiO2) is one of the green cata-lysts, which has attracted much attention due to its promising applications in the purification of air, the bactericidal action of water, and environmental photocatalytic degradation of organic pollutant co…     

Formation mechanism of conducting polypyrrole nanotubes in reverse micelle systems

Polypyrrole (PPy) nanotubes were readily fabricated through chemical oxidation polymerization in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse (water-in-oil) emulsions. The reverse cylindrical micelle phase was characterized, and the key factors affecting the formation of PPy nanotubes were systematically inspected. AOT reverse cylindrical micelles were prepared via a cooperative interaction between an aqueous FeCl3 solution and AOT in an apolar solvent. In the H2O/FeCl3/AOT/apolar solvent system, the aqueous FeCl3 solution played a role in increasing the ionic strength and decreasing the second critical micelle concentration of AOT. As a result, AOT reverse cylindrical micelles could be spontaneously formed in an apolar solvent. In addition, iron cations were adsorbed to the anionic AOT headgroups that were capable of extracting metal cations from the aqueous core. Under these conditions, the addition of pyrrole monomer resulted in the chemical oxidation polymerization of the corresponding monomer at the surface of AOT reverse cylindrical micelles, followed by the formation of tubular PPy nanostructures. In a typical composition (74.0 wt % hexane, 22.4 wt % AOT, and 3.6 wt % aqueous FeCl3 solution at 15 degrees C), the average diameter of PPy nanotubes was approximately 94 nm and their length was more than 2 mum. The PPy nanotube dimensions were affected by synthetic variables such as the weight ratio of aqueous FeCl3 solution/AOT, type of apolar solvent, and reaction temperature. Moreover, the relationship between the diameter and the conductivity of the nanotubes was investigated.     

Chemical alteration of poly(tetrafluoroethylene) TFE teflon induced by exposure to electrons and inert-gas ions

In this study the chemical alterations of poly(tetrafluoroethylene) (TFE Teflon) by approximately 1.0-keV electrons and 1.0-keV He and Ar ions have been examined using X-ray photoelectron spectroscopy (XPS). The initial F/C atom ratio of 1.99 decreases to a steady-state value of 1.48 after 48 h of electron exposure. Exposure to either He+ or Ar+ decreases the initial F/C atom ratio from approximately 2 to a steady-state value of 1.12. The high-resolution XPS C 1s data indicate that new chemical states of carbon form as the F is removed and that the relative amounts of these states depend on the F content of the near-surface region. These states are most likely due to C bonded only to one F atom, C bonded only to other C atoms and C that have lost a pair of electrons through emission of F-. Exposures of the electron-damaged and He+- or Ar+-damaged surfaces to research-grade O2 result in chemisorption of very small amounts of O indicating that large quantities of reactive sites are not formed during the chemical erosion. Further exposure to the electron or ion fluxes quickly removes this chemisorbed oxygen. Exposure of the He+-damaged surface to air at room temperature results in the chemisorption of a larger amount of O than the O2 exposure but no N is adsorbed. The chemical alterations due to electrons and ions are compared with those caused by hyperthermal (approximately 5 eV) atomic oxygen (AO) and vacuum ultraviolet (VUV) radiation. The largest amount of damage is caused by AO followed by VUV, inert-gas ions, and then electrons.     

Low-temperature studies of encapsulated proteins

Water-soluble proteins encapsulated within reverse micelles may be studied under a variety of conditions, including low temperature and a wide range of buffer conditions. Direct high-resolution detection of information relating to protein folding intermediates and pathways can be monitored by low-temperature solution NMR. Ubiquitin encapsulated within AOT reverse micelles was studied using multidimensional multinuclear solution NMR to determine the relationship between protein structure, temperature, and ionic strength. Ubiquitin resonances were monitored by 15N HSQC NMR experiments at varying temperatures and salt concentrations. Our results indicate that the structure of the encapsulated protein at low temperature experiences perturbation arising from two major influences, which are reverse micelle-protein interactions and low-temperature effects (e.g., cold denaturation). These two effects are impossible to distinguish under conditions of low ionic strength. Elevated concentrations of nondenaturing salt solutions defeat the effects of reverse micelle-protein interactions and reveal low-temperature protein unfolding. High ionic strength shielding stabilizes the reverse micelle at low temperatures, which reduces the electrostatic interaction between the protein and reverse micelle surfaces, allowing the phenomenon of cold denaturation to be explored.