Interfacial adsorption of an inhalation anesthetic onto ionic surfactant micelles and its desorption by high pressure

The effects of pressure and temperature on the critical micelle concentration (CMC) of sodium dodecylsulfate (SDS) were measured in the presence of various concentrations of an inhalation anesthetic, methoxyflurane. The change in the partial molal volume of SDS on micellization, $\text{Δ}\text{V}{}_{\mathrm{<mtext>m</mtext>}}$, increased with the increase in the concentration of methoxyflurane. The CMC-decreasing power, which is defined as the slope of the linear plot between ln(CMC) vs. mole fraction of anesthetic, was determined as a function of pressure and temperature. Since the CMC-decreasing power is correlated to the micelle/water partition coefficient of anesthetic, the volume change of the transfer (ΔV_p^o) of methoxyflurane from water to the micelle can be determined from the pressure dependence of the CMC-decreasing power. The value of ΔV_p^o amounts 6.5±1.8 cm³·mol^?1, which is in reasonable agreement with the volume change determined directly from the density data, 5.5±0.6 cm³ · mol^?1. Under the convention of thermodynamics, this indicates that the application of pressure squeezes out anesthetic molecules from the micelle. The transfer enthalpy of anesthetic from water to the micelle is slightly endothermic. The partial molal volume of methoxyflurane in the micelle (112.0 cm³·mol^?1) is smaller than that in decane (120.5 cm³·mol^?1) and is larger than that in water (108.0 cm³·mol^?1). This indicates that the anesthetic molecules are incorporated into the micellar surface region, i.e., the palisade layer of the micelle in contact with water molecules, rather than into the micelle core.     

外源腐殖酸对三种土壤磷吸附与解吸特性的影响

通过对3种土壤（红壤、棕壤和褐土）施入不同腐殖酸的室内培养试验,探讨了外源腐殖酸对不同土壤磷素吸附和解吸的影响。结果表明：与对照土壤相比,不同腐殖酸降低了3种供试土壤磷素的吸附量,其降低顺序为：褐土＞红壤＞棕壤;外源腐殖酸提高了红壤和棕壤磷素的解吸量和解吸率,提高的幅度与腐殖酸的种类有关;而腐殖酸对褐土磷素的解吸量则无明显促进作用。表明外源腐殖酸对3种土壤磷素吸附-解吸作用最强的为红壤,其次为棕壤,最弱的为褐土;同时表明腐殖酸可提高红壤和棕壤磷素的利用率。     

Studies on adsorption of amyloglucosidase on ion-exchange resins

Highly charged water-soluble conjugates of amyloglucosidase with a copolymer of ethylene-maleic acid or styrene-maleic acid were prepared and adsorbed on DEAE-cellulose and other cationic resins. Negatively charged enzyme conjugates were also obtained by means of succinylation. The polyanionic conjugates of amyloglucosidase adsorbed on the cationic carriers show higher temperature stability than the native enzyme adsorbed on the same carriers under the same experimental conditions. The insoluble enzyme conjugate-carrier complexes could be reused and retained their full activity while working continuously for three weeks. The application of the insoluble enzyme preparations with the above characteristics which could possibly satisfy the requirements for industry are discussed.     

Separation of DNA fragments by high-resolution ion-exchange chromatography on a nonporous QA column

A nonporous QA column (a strong anion exchanger) was used for HPLC of DNA fragments. This column was successfully employed to separate small (ca. 10 bp) and intermediate size (ca. 10 kbp) DNA fragments from each other. The column also separated double-stranded DNA from its single-stranded form, and circular DNA molecules from linear ones. The entire separation process was completed within 60 min. The recovery of DNA fragments in each run was above 95%. High resolution was obtained both at an analytical level (microgram scale) and at a preparative level (100 micrograms scale). In view of time efficiency, recovery, and resolution, the nonporous QA column is superior to other porous ion-exchange columns and expected to be a very useful tool in molecular biological studies.     

Effects of ionic substances on the adsorption of egg white proteins to a stainless steel surface

The surface fouling of food processing equipment by proteins was studied by investigating the adsorption of egg white proteins to the surface of stainless steel (SS) at pH 7.4 and 30 °C, and particularly the effects of different types of ionic substances. Ovalbumin and ovomucoid, acidic egg white proteins, were less adsorbed in the presence of phosphate (P(i)), a multivalent anion, than in the presence of HEPES, an amphoteric ion. On the other hand, lysozyme, a basic egg white protein, was more adsorbed in the presence of P(i) than in the presence of HEPES. Citrate as another multivalent anion and taurine as another amphoteric ion affected the respective adsorption of those egg white proteins similarly to P(i) and HEPES. The adsorption of an egg white protein to an SS surface therefore depended on the combination of the type of protein and the effective charge of the coexisting ionic substance. This behaviour can be well explained by assuming that a small ionic substance precedes a protein in attaching to an SS surface, resulting in an alteration to the effective surface charge. Pretreating SS with a P(i) buffer lowered the amount of ovalbumin adsorbed with the HEPES buffer, demonstrating that P(i) can attach to and remain on the SS surface to affect the subsequent protein adsorption.     

不同来源生物炭对砷在土壤中吸附与解吸的影响

采用OECD Guideline 106批平衡方法研究了由凋落松针、玉米秸秆、牛粪制备的3种生物炭对As(Ⅴ)在棕壤中的吸附和解吸特性的影响.结果表明：3种生物炭的添加量为0.5%时,对As(Ⅴ)在土壤中的吸附量大小顺序为牛粪炭处理＞松针炭处理＞玉米秸秆炭处理,这与生物炭的基本性质密切相关;等温吸附曲线能用Langmuir方程进行很好的拟合(R² =0.997);与对照相比,生物炭处理对砷的吸附容量(lgK_f 为1.99～2.10)和吸附强度(1/N 为0413～0.449)降低,生物炭对As(Ⅴ)的主要吸附机制为物理吸附;生物炭处理对As(Ⅴ)解吸率大小顺序为：玉米秸秆炭处理＞松针炭处理＞牛粪炭处理,解吸率在14.5%～18.7%.添加3种来源生物炭降低了棕壤对As(Ⅴ)的吸附,这可能会导致砷的有效性增强,更易被生物吸收,进而增强土壤中砷的毒性.     

活性铝对小麦根生长及酶活性的影响

利用铝形态分布与环境pH的相关性,通过改变染毒液pH条件,研究了不同浓度活性铝对小麦根生长、蛋白质含量及酸性磷酸酶活性的影响,并探讨了不同形态活性铝植物毒性的差异.本实验染毒液中总铝浓度设置为0(CK)、25(T₁)和75μmol·L^-1(T₂)3组,各组pH分别调至4.0、4.5、5.0和5.5.结果表明,微量Al_a与Al_b对小麦根生长均具有抑制作用.但随染毒液中活性铝组分的改变,小麦根蛋白质含量和酸性磷酸酶活性显现相反变化趋势:T₁和T₂组在pH4.0,活性铝主要成分为Al_a时(Al_a浓度高于活性铝浓度的90%),小麦根细胞蛋白质含量显著下降,酸性磷酸酶活性显著上升;T₁和T₂组在pH5.0,Al_a浓度降低至与Al_b浓度接近,且Al_a和Al_b浓度均低于10μmol·L^-1时,根细胞蛋白质含量显著上升,酸性磷酸酶活性显著下降.     

Post-thaw plasma membrane integrity of bull spermatozoa separated with a Sephadex ion-exchange column

Previous experiments have established that filtration of bovine semen through a Sephadex ion-exchange column improves its quality before and after freezing. The present study was conducted to determine the post-thaw membrane integrity of bull spermatozoa separated with a Sephadex ion-exchange column and to determine the kind of protection to spermatozoa is provided by glycerol during freezing and thawing. Semen from Holstein bulls diluted in TEST-yolk extender (with and without glycerol) was filtered through a Sephadex ion-exchange column and frozen in liquid nitrogen (-196 degrees C). After thawing, there were more normal acrosomes in filtered spermatozoa than nonfiltered (P < 0.01). Post-thaw plasma membrane integrity and swelling ability in a hypoosmotic solution revealed that the filtered spermatozoa had a stronger (P < 0.005) plasma membranes than the nonfiltered. Filtered spermatozoa demonstrated higher zona-free hamster oocyte penetration than the nonfiltered (30.5 vs 11.5%; P < 0.0005). Spermatozoa extended in TEST-yolk without glycerol had the lowest (P < 0.001) normal acrosomes, intact plasma membranes and swelling ability. Plasma membrane over the post-acrosomal region of the head and post-midpiece region of the tail was more sensitive to damages caused by freezing and thawing than acrosomal and midpiece regions of spermatozoa. Glycerol in the extender provided significant (P < 0.05) protection to the sensitive regions of filtered and nonfiltered spermatozoa during freezing and thawing. Filtered plus glycerolated spermatozoa had the highest (P < 0.01) normal acrosomes, intact plasma membranes and swelling ability. In conclusion, the pre-freezing filtration of bovine semen harvested the spermatozoa possessing stronger plasma membranes which enabled them to endure freezing and thawing stresses. The addition of glycerol to the extender protected the post-acrosomal region of the head and post-midpiece region of the tail of spermatozoa from freezing and thawing shocks.     

Adhesion of Azospirillum brasilense to polystyrene: Influence of ionic strength through protein adsorption

The influence of ionic strength on the adhesion of Azospirillum brasilense to polystyrene has been examined by comparing water and phosphate buffer saline (PBS) as suspending media. Polystyrene supports analysed by X‐ray photoelectron spectroscopy (XPS) after adhesion in PBS for 2 h or 24 h and detachment of adhering cells showed a higher protein surface concentration, reflected by the N/C atomic concentration ratio, compared to supports analysed after adhesion in water. It was shown that PBS both favours protein release by the cells into the solution and enhances the tendency of proteins to adsorb at the support surface.

After 2 h contact time, the increase in the concentration of adsorbed proteins in PBS was related to an increase in adhesion density. However, the observation that the adhesion density after 24 h was lower in PBS than in water indicated that the amount of proteins adsorbed at the support surface controls cell adhesion in a complex way. In PBS, a thick layer of proteinaceous material retaining the bacterial cells is formed; this leads to underestimation of the density of adhering cells as well as to a heterogeneous adhesion pattern and to a relatively low adhesion density due to detachment of pellicles upon rinsing.

The ionic strength thus influences bacterial adhesion in a more subtle way than simply through double layer interactions between the cells and the support.     

Physico-chemical and functional characteristics of a subfraction of low-density lipoproteins isolated by ion-exchange column chromatography

Fractionation of human blood plasma low density lipoproteins (LDL) was performed by ion-exchange chromatography, using a linear NaCl gradient. It was shown that the binding of LDL subfractions eluted with a low ionic strength buffer (i.e., containing the particles with a lower negative charge) to B, E-receptors of fibroblasts was more effective than that of subfractions eluted with a high ionic strength buffer (i.e., containing the particles with a higher negative charge). The LDL particles with a lower negative charge had lower values of flotation coefficients (according to analytical ultracentrifugation data), smaller dimensions (according to gradient gel electrophoresis data) and a lower phospholipid/protein ratio (w/w). The experimental results suggest that LDL subfractions having different electrical parameters of the particle surface also differ in other physicochemical properties and seem to play a different role in atherogenesis.     

Root surface area measurements based on adsorption and desorption of nitrite

A method, based on the negative adsorption of NO₂ ^-, has been developed to determine surface area of roots. Young roots of 3–4 year old plants ofAcacia catechu, Eucalyptus camaldulensis andLeucaena leucocephala were up-rooted and cut into 18 cylindrical pieces. Each root piece was immersed individually for 10 sec in 0.05M, 0.10M and 0.15M aqueous NaNO₂ solution and the excess solution on the root surface allowed to drain off. It was then transferred to conical flask containing distilled water and shaken for 15 min for desorption of nitrite. A known quantity of this aliquot was reacted with 1% acidic sulphanilamide and 0.02% NED HCl. A pink colour developed, and its optical density was read at 540 nm. A positive linear correlation was noted between colour density and root surface area. The respective correlation coefficientvalues for 0.05M, 0.10M and 0.15M NaNO₂ solutions were 0.973, 0.963 and 0.964 forAcacia catechu, 0.933, 0.903 and 0.898 forEucalyptus camaldulensis and 0.968, 0.976 and 0.972 forLeucaena leucocephala (significant atp<0.001). The method was successfully adopted to determine the root surface area of seedlings ofAlbizia lebbek, A. procera, Acacia auriculiformis, A. nilotica, Dalbergia latifolia andD. sissoo.     

Kinetics of protein adsorption and desorption on surfaces with grafted polymers

The kinetics of protein adsorption are studied using a generalized diffusion approach which shows that the time-determining step in the adsorption is the crossing of the kinetic barrier presented by the polymers and already adsorbed proteins. The potential of mean-force between the adsorbing protein and the polymer-protein surface changes as a function of time due to the deformation of the polymer layers as the proteins adsorb. Furthermore, the range and strength of the repulsive interaction felt by the approaching proteins increases with grafted polymer molecular weight and surface coverage. The effect of molecular weight on the kinetics is very complex and different than its role on the equilibrium adsorption isotherms. The very large kinetic barriers make the timescale for the adsorption process very long and the computational effort increases with time, thus, an approximate kinetic approach is developed. The kinetic theory is based on the knowledge that the time-determining step is crossing the potential-of-mean-force barrier. Kinetic equations for two states (adsorbed and bulk) are written where the kinetic coefficients are the product of the Boltzmann factor for the free energy of adsorption (desorption) multiplied by a preexponential factor determined from a Kramers-like theory. The predictions from the kinetic approach are in excellent quantitative agreement with the full diffusion equation solutions demonstrating that the two most important physical processes are the crossing of the barrier and the changes in the barrier with time due to the deformation of the polymer layer as the proteins adsorb/desorb. The kinetic coefficients can be calculated a priori allowing for systematic calculations over very long timescales. It is found that, in many cases where the equilibrium adsorption shows a finite value, the kinetics of the process is so slow that the experimental system will show no adsorption. This effect is particularly important at high grafted polymer surface coverage. The construction of guidelines for molecular weight/surface coverage necessary for kinetic prevention of protein adsorption in a desired timescale is shown. The time-dependent desorption is also studied by modeling how adsorbed proteins leave the surface when in contact with a pure water solution. It is found that the kinetics of desorption are very slow and depend in a nonmonotonic way in the polymer chain length. When the polymer layer thickness is shorter than the size of the protein, increasing polymer chain length, at fixed surface coverage, makes the desorption process faster. For polymer layers with thickness larger than the protein size, increases in molecular weight results in a longer time for desorption. This is due to the grafted polymers trapping the adsorbed proteins and slowing down the desorption process. These results offer a possible explanation to some experimental data on adsorption. Limitations and extension of the developed approaches for practical applications are discussed.     

Biosorption and desorption of Nickel on oil cake: batch and column studies

Biosorption potential of mustard oil cake (MOC) for Ni(II) from aqueous medium was studied. Spectroscopic studies showed possible involvement of acidic (hydroxyl, carbonyl and carboxyl) groups in biosorption. Optimum biosorption was observed at pH 8. Contact time, reaction temperature, biosorbent dose and adsorbate concentration showed significant influence. Linear and non-linear isotherms comparison suggests applicability of Temkin model at 303 and 313 K and Freundlich model at 323 K. Kinetics studies revealed applicability of Pseudo-second-order model. The process was endothermic and spontaneous. Freundlich constant (n) and activation energy (E_a) values confirm physical nature of the process. The breakthrough and exhaustive capacities for 5 mg/L initial Ni(II) concentration were 0.25 and 4.5 mg/g, while for 10 mg/L initial Ni(II) concentration were 4.5 and 9.5 mg/g, respectively. Batch desorption studies showed maximum Ni(II) recovery in acidic medium. Regeneration studies by batch and column process confirmed reutilization of biomass without appreciable loss in biosorption.     

Rapid purification of a recombinant protein using tandem radial flow ion-exchange column chromatography.

Tandem radial flow anion- and cation-exchange columns were used to partially purify and concentrate a dilute recombinant protein that had been refolded in vitro after production as insoluble inclusion bodies in E. coli. The refolded sample was first passed through a Q-Sepharose Fast Flow column in order to remove the majority of E. coli contaminating proteins and endotoxins, then purified on an S-Sepharose Fast Flow column connected to the outlet of the Q-Sepharose column. This tandem arrangement enabled the rapid processing of multiple preparations of refolded material during production method development.     

几种粉煤灰对磷素吸附与解吸特性的研究

通过吸附解吸和培养试验, 研究了几种粉煤灰对磷素吸附与解吸特性.结果表明,粉煤灰的全磷含量和有效磷含量分别为0.545～4.540 g·kg^-1和19.55～163.0 mg·kg^-1,显著高于土壤,粉煤灰对磷吸附量随着加入溶液磷浓度的增加而增加,但其吸附率随着加入溶液磷浓度的增加而减少;粉煤灰的吸磷率比土壤高,但其解吸率低.这主要是由于粉煤灰比土壤存在更多的磷吸附位点且结合能大,不易解吸.Langmuir方程、Freundlich方程和Temkin方程都能很好地拟合粉煤灰对磷吸附,其中Langmuir方程的MBC、Freundlich方程的a和Temkin方程的k2都可以表征粉煤灰对磷吸附能力, MBC、a和k2值越大,则吸磷能力越强.不同来源的粉煤灰的MBC、a和k2值不同,其大小顺序为：湘潭电厂(5 167.7,4 056.2,831.5)>岳阳纸厂(1 650.7,2 803.4,711.9)>华能电厂(303.0,1 677.6,368.7)>株洲电厂(76.2,464.2, 211.0) > 洞庭氮肥厂(34.7,413.48,213.8).粉煤灰对磷吸附固定作用随粉煤灰含水量的增加有增大的趋势.粉煤灰对磷吸附主要是专性吸附和化学沉淀反应,所以在施用粉煤灰改良土壤或利用粉煤灰制造复混肥时,须考虑粉煤灰对磷的固定作用及粉煤灰含水量的影响.     

Equilibrium and dynamic investigations of organic acids adsorption onto ion-exchange resins

The aim of the study was to determine properties of selected ion-exchange resins for citric and lactic acids recovery, to define sorption isotherms for these acids at different temperatures (in the range of 20–60°C) and to determine diffusion coefficients inside sorbent particles. A mathematical model of the ion-exchange process in the chromatographic column and its experimental verification is also presented. During investigations 18 types of ion-exchange resins were tested. It was found that weakly basic resins were more suitable for the recovery process than strongly basic ones. The best resin for the separation of citric acid was Amberlite IRA-67 and for lactic acid Amberlite IRA-92. As a result of transient-state sorption experiments diffusion coefficients of the citric acid inside the sorbent particle at different temperatures were obtained. It was found that D_p increased with the temperature by two times in the range of 20–60°C, and its value at 60°C was 7.2×10^–10 m²/s. The proposed mathematical model was applied to identify bed operation parameters in the column for the needs of the simulated moving bed chromatography method.List of symbols b Equilibrium constant in Langmuir equation, [dm³/g] - c Acid concentration in the liquid phase inside the particle pores, [g/dm³] - C Acid concentration in the liquid, [g/dm³] - D_L Axial dispersion coefficient, [m²/s] - D_p Intraparticle diffusion coefficient, [m²/s] - k_f Liquid film mass transfer coefficient, [m/s] - L Ion-exchanger bed height, [m] - q Acid concentration in the adsorbent phase, [g/dm³] - R_p Particle radius, [m] - U Volumetric flow rate of the feeding solution, [dm³/s] - V Volume of the solution, [dm³] - W Weight of the wet resin particles, [g] - The ion-exchanger bed porosity, [-] - _p Particle porosity, [-] - Linear liquid velocity, [m/s] - Apparent density of the wet resin, [g/dm³]     

碳酸钙对土壤镉吸附及解吸的影响

采用等温吸附法,并以1mol/L KNO3进行解吸试验,研究CaCO3对3种土壤镉吸附和解吸的影响。结果表明,3种土壤的原状土样对镉吸附总趋势为：栗钙土＞棕壤＞淋溶褐土,均符合Langmuir方程、Frenudlich方程和Temink方程,其中以Freumdlich方程最佳。镉的专性吸附量表现为栗钙土＞淋溶褐土＞棕壤。添加CaCO3使3种土壤中镉的吸附量增加,增加幅度棕壤为4％－11％,淋溶褐土2％－11％,栗钙土2％－8％。外界加入的镉浓度越高,增加幅度越大。Freundlich方程（lgX=lgK lgC/n）拟合的参数结果表明：加入CaCO3后,K和n值均下降;Langmuir方程中镉最大吸附值增加,吸附平均常数减小。可以推测,CaCO3的存在之所以能够使土壤体系吸附镉能力增加,除CaCO3本身的吸附作用增加,吸附平衡常数减小。可以推测,CaCO3的存在之所以能够使土壤体系吸附镉能力增加,除CaCO3本身的吸附作用外,还可能影响反应体系的平衡系数。加入CaCO3,土壤对镉的专性吸附明显增加,尤其以棕壤专性吸附的镉最多,淋溶褐土其次,而栗钙土增加较少,栗钙土去除CaCO3后,镉的吸附减少了2.0%-26.0%,土壤专性吸附的镉减少4.0%-38.2%。3种土壤镉的解吸能力表现为：棕壤＞淋溶褐土＞栗钙土。添加CaCO3,土壤镉的解吸量下降。去除CaCO3后,栗钙土匐解吸量明显增加。