小分子热休克蛋白Mj HSP16.5的分级变性

应用荧光光谱、圆二色光谱、体积排阻色谱、激光动态光散射等技术, 研究了来自嗜热古细菌Methanococcus jannaschii (Mj)的小分子热休克蛋白Mj HSP16.5在变性剂作用下的变性过程. 研究表明, 在pH 7时, Mj HSP16.5在8 mol·L-1尿素作用下不会发生变性. 在pH 7条件下, 盐酸胍对Mj HSP16.5的变性表现为一个分级过程,分别在2.0、3.0和6.0 mol·L-1盐酸胍浓度附近,出现明显的结构变化; 到7.0 mol·L-1盐酸胍时, Mj HSP16.5才完全变性. 降低溶液pH值将使Mj HSP16.5的变性变得更为容易.     

Electrodeposition of the Charge-Transfer Complex Generated during Electrooxidation of o-Tolidine and the Effects of Coexisting Chondroitin Sulfate

The electrochemical quartz crystal microbalance (EQCM) technique was used to investigate the electrodeposition of the charge-transfer complex (CTC) generated during electrooxidation of o-tolidine (o-TD) in Britton-Robinson buffers and the effects of coexisting chondroitin sulfate (CS). A V-shaped frequency response to the cyclic voltammetric switching of o-TD indicated the precipitation and dissolution of the poorly soluble CTC, an oxidation intermediate, formed at the Au electrode during the redox switching of o-TD in a neutral or a weakly acidic medium (pH=4.07-6.50). The effects of potential scan rate, solution pH, and several supporting electrolytes were examined. The depth of the V-shaped frequency curves (-Δf_0V) was related to the supporting electrolyte used, with a decreasing sequence for −Δf_0V as 0.20 mol·L⁻¹ NaNO₃ > 0.20 mol·L⁻¹ NaClO₄ > 0.10 mol·L⁻¹ Na₂SO₄. The −Δf_0V response to the redox switching of the CTC/o-TD “couple” was enhanced by the introduction of CS because of the formation of the CTC-CS adduct, as also characterized and supported by UV-Vis and FTIR spectrophotometry. The molar ratio (x) of the CTC to CS in the adduct and the electrode-collection efficiency of the CTC (η) were estimated using EQCM. The values of −Δf_0V increased with the increase in CS concentration, with a linear range from 0.75 to 15.2 μmol·L⁻¹, and a detection limit down to 50 nmol·L⁻¹. The new method proposed for CS assay was characterized by a dynamically renewed surface of the detection electrode.     

Corrosion and Anodic Behaviors of Pure Aluminum in a Novel Alkaline Electrolyte

The corrosion and anodic dissolution behaviors of pure aluminum in Na₂SnO₃-containing 4 mol·L⁻¹ KOH methanol-water mixed solutions with a methanol/water volume ratio of 4:1 were investigated. This was carried out by means of hydrogen collection, polarization curve, galvanostatic discharge, scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). The experimental results indicated that the addition of stannate inhibited the corrosion of aluminum in the 4 mol·L⁻¹ KOH methanol-water solutions by the deposition of tin with a higher hydrogen evolution overpotential on the electrode surface. In the electrolytes with higher stannate contents the inhibiting effect decreased because of the occurrence of some cracks on the tin deposition film. The results of galvanostatic discharge showed that the discharge of aluminum in the Na₂SnO₃-containing 4 mol·L⁻¹ KOH methanol-water solutions were obviously improved. In addition, the improvement effect enhanced with the increase of stannate content. It was noted that the aluminum anode showed a very flat discharge plateau at relatively low potentials in the electrolyte with 10.0 mmol·L⁻¹ Na₂SnO₃ at 20 mA·cm⁻² discharge current density.     

Determination of brominated phenols in water samples by on-line coupled isotachophoresis with capillary zone electrophoresis

A method for determination of nine brominated phenols as environmental risk compounds was developed by on-line coupled capillary isotachophoresis and capillary zone electrophoresis (ITP–CZE). For ITP step, 1 × 10⁻² mol L⁻¹ hydrochloric acid with 3 × 10⁻² mol L⁻¹ ammediol pH 9.1 was used as the leading electrolyte, and 3 × 10⁻² mol L⁻¹ β-alanine with 2 × 10⁻² mol L⁻¹ sodium hydroxide pH 10.05 was used as the terminating electrolyte. As the background electrolyte for CZE separation, 2.5 × 10⁻² mol L⁻¹ β-alanine with 2.5 × 10⁻² mol L⁻¹ lysine pH 9.6 was used. All electrolytes contained 0.05% or 0.1% (m/v) hydroxyethylcellulose to suppress the electroosmotic flow. UV detection at wavelength 220 nm was used. Detection limits in order of tens of nmol L⁻¹ were achieved. Good repeatability of migration times (less than 0.33% RSD) and good repeatability of peak areas (less than 7.19% RSD) at concentration level 5 × 10⁻⁸ mol L⁻¹ were observed. Developed ITP–CZE method was applied to determination of brominated phenols in spiked tap and river water samples.     

A fully automated effervescence-assisted switchable solvent-based liquid phase microextraction procedure: Liquid chromatographic determination of ofloxacin in human urine samples

A novel fully automated effervescence-assisted switchable solvent-based liquid phase microextraction procedure has been suggested. In this extraction method, medium-chain saturated fatty acids were investigated as switchable hydrophilicity solvents. The conversion of fatty acid into hydrophilic form was carried out in the presence of sodium carbonate. The injection of sulfuric acid into the solution decreased the pH value of the solution, thus, microdroplets of the fatty acid were generated. Carbon dioxide bubbles were generated in-situ, and promoted the extraction process and final phase separation. The performance of the suggested approach was demonstrated by the determination of ofloxacin in human urine samples using high-performance liquid chromatography with fluorescence detection. This analytical task was used as a proof-of-concept example. Under the optimal conditions, the detector response of ofloxacin was linear in the concentration ranges of 3·10⁻⁸−3·10⁻⁶ mol L⁻¹. The limit of detection, calculated from a blank test based on 3σ, was 1·10⁻⁸ mol L⁻¹. The results demonstrated that the presented approach is highly cost-effective, simple, rapid and environmentally friendly.     

Linear polyamines as carriers in thiocyanate-selective membrane electrodes

The polyamines, octyl-[2-(2-octylamino-ethylamino)-ethyl]-amine (L¹) and octyl-{2-[2-(2-octylamino-ethylamino)-ethylamino]-ethyl}-amine (L²), have been used as anion ionophores in PVC-based membrane ion-selective electrodes. Different electrodes were prepared containing L¹, or L², and o-nitrophenyl octyl ether (NPOE) or bis(2-ethylhexyl)sebacate (DOS) as plasticizers. The response of the electrodes was tested in two different buffers, HEPES-KOH (pH 7) and MES-KOH (pH 5.6). Electrodes containing L¹ and L² with NPOE (E1 and E2, respectively) showed a Nernstian response for thiocyanate with a good response time. The detection limit, linear range and slope for electrode E1 were 3.8 × 10⁻⁶ mol dm⁻³, 1 × 10⁻⁵ to 1 × 10⁻¹ mol dm⁻³ and −57.2 mV decade⁻¹ at pH 5.6 and 4.47 × 10⁻⁶ mol dm⁻³, 1.95 × 10⁻⁵ to 1 × 10⁻¹ mol dm⁻³ and −58.1 mV decade⁻¹ at pH 7.0. For electrode E2 the detection limit, linear range and slope found were 2.63 × 10⁻⁶ mol dm⁻³, 7.94 × 10⁻⁶ to 1 × 10⁻¹ mol dm⁻³ and −58.5 mV decade⁻¹ at pH 5.6 and 1.23 × 10⁻⁵ mol dm⁻³, 7.95 × 10⁻⁵ to 1 × 10⁻¹ mol dm⁻³ and −46.0 mV decade⁻¹ at pH 7. In contrast, electrodes containing DOS as plasticizers gave only response at pH 5.6 (detection limit, linear range and slope at pH 5.6 were 3.16 × 10⁻⁵ mol dm⁻³, 1 × 10⁻⁴ to 1 × 10⁻¹ mol dm⁻³ and −52.6 mV decade⁻¹). Selectivity coefficients for different anions with respect to thiocyanate were calculated. The electrode E2 at pH 5.6 was also used for the determination of SCN⁻ by potentiometric titrations with Ag⁺ ions with good results. The electrode E2 was also used to determine concentrations of thiocyanate in biological samples.     

High activity of Mj HSP16.5 under acidic condition

Small heat shock proteins (sHSPs) exist ubiquitously among all organisms, with a variety of functions. All small heat shock proteins assemble into a native large oligomeric state containing 9–40 monomers. The sHSPs show chaperone-like activity to prevent the aggregation of nonnative proteins under stressful cellular conditions such as non-optimal temperatures, pH changes, osmotic pressure, and exposure to toxic chemicals. It was found that a common dimeric subunit of sHSPs might be the major active species, but whether the native large oligomeric state is only a storage state or a state crucial to its molecular chaperone activity is still under debate. The native large oligomeric state of the small heat shock protein from a hyperthermophilic methanarchaeon, Methanococcus jannaschii (Mj HSP 16.5), is a stable icositetramer, which is a symmetric hollow sphere that is very stable even at 85°C, and no small active subunit has been detected till now. Our results show that Mj sHSP 16.5 changes into small and active oligomeric state at pH 3, likely as octamers (average result) at 25°C, and dimers at 65°C. The dimer of Mj HSP 16.5 at pH 3.0 and 65°C is very active and efficient, even 7-fold more efficient than the high-temperature-activated icositetramer at neutral pH. Monomer exchange can be observed between dimers of Mj HSP 16.5 at pH 3.0 and 65°C. These results not only demonstrate that the icositetramer structure of Mj sHSP16.5 is not necessary for its molecular chaperone activity, but also suggest that Mj sHSP16.5 is a very efficient chaperone acting at high temperature and under the acidic condition. Even though it is not clear whether the native environment of Methanococcus jannaschii is acidic or not, given its ability to excrete acidic compounds, it is likely that Methanococcus jannaschii will encounter acidic internal or external environments at high temperature. Our results demonstrate that Mj HSP 16.5 may help Methanococcus jannaschii to survive better under those extreme environmental conditions. Supported by the National Natural Science Foundation of China (Grant Nos. 20203001, 20673003, and 30490245) and Ministry of Science and Technology of China (Grant No. 2006AA02Z301)     

Sodium hexadecanoate micellar aggregation number

The diffusion coefficient of sodium hexadecanoate micelles was studied by polarography at 63°C, and the size and aggregation number of the micelles was computed. At concentrations above 0.01 mol·L^–1 rodlike micelles exist, which become flexible at 0.040 mol·L^–1 and entangle at 0.043 mol·L^–1     

Electrochemical and In Situ FTIR Studies of Adsorption and Oxidation of Dimethyl Ether on Platinum Electrode

Dissociative adsorption and electrooxidation of dimethyl ether (DME) on a platinum electrode in different pH solutions were studied using cyclic voltammetry (CV) and in situ FTIR reflection spectroscopy. The coverage of the dissociative adsorbed species was measured about 70% from hydrogen adsorption-desorption region (0.05-0.35 V (vs RHE)) of steady-state voltammogram recorded in 0.1 mol·L⁻¹ H₂SO₄ solution. It was found that the electrochemical reactivity of DME was pH dependent, i.e., the larger the pH value was, the less the reactivity of DME would be. No perceptible reactivity of DME in 0.1 mol·L⁻¹ NaOH solution could be detected. It was revealed that the protonation of the oxygen atom in the C-O-C bond played a key role in the electrooxidation of DME. In situ FTIR spectroscopic results illustrated that linearly bonded CO (CO_L) species determined at low potential region were derived from the dissociative adsorption of DME and behaved as ‘poisoning’ intermediate. The CO_L species could be oxidized to CO₂ at potential higher than 0.55 V (vs RHE) and in the potential range from 0.75 to 1.00 V (vs RHE) DME was oxidized simultaneously via HCOOH species that were identified as the reactive intermediates.     

Flow method based on cloud point extraction for fluorometric determination of epinephrine in human urine

A novel stepwise injection fluorometric method for the determination of epinephrine in human urine has been developed. In the current study, the stepwise injection analysis (SWIA) was successfully combined with on-line in-syringe cloud point extraction (CPE) and fluorometric detection. The procedure was based on the epinephrine derivatization in the presence of o-phenylenediamine followed by the preconcentration stage based on the CPE with the nonionic surfactant Triton X-114. After the phase separation into a syringe of the flow system, the micellar phase containing the epinephrine derivative was transported to a fluorometric detector. The excitation and emission wavelengths were set at 447 nm and 550 nm, respectively. The conditions of epinephrine derivatization and CPE have been studied. The calibration plot constructed using the developed procedure was linear in the range of 1·10⁻¹¹–5·10⁻⁷ mol L⁻¹. The limit of detection, calculated as 3 σ of a blank test (n = 10), was found to be 3·10⁻¹² mol L⁻¹. The proposed method was successfully applied for the determination of epinephrine in human urine samples.     

Determination of uranium by adsorptive stripping voltammetry at a lead film electrode

An adsorptive stripping voltammetric procedure for the determination of U(VI) at an in situ plated lead film electrode is described. The U(VI) complex with cupferron was accumulated from an acetate buffer solution of pH 4.2 at the potential −0.65 V. The measurements were carried out from undeaerated solutions. The calibration graph for an accumulation time of 180 s was linear from 5 × 10⁻¹⁰ to 2 × 10⁻⁸ mol L⁻¹. The detection limit was 2 × 10⁻¹⁰ mol L⁻¹, the relative standard deviation for 2 × 10⁻⁸ mol L⁻¹ U(VI) was 4.3%. The proposed procedure was validated in the course of U(VI) determination in water certified reference materials.     

Determination of citrate in tablets and of oxytetracycline in serum using europium (III) luminescence

A direct method for the determination of citrate and oxytetracycline in samples containing complex matrices like tablets or serum has been developed using the luminescence of the ternary complex formed with Eu(III) ions. The triplet-state energy level of oxytetracycline (OxTc), the excitation maximum (412 nm) and the luminescence lifetime of Eu-OxTc (58 μs) were determined. A 17-fold luminescence enhancement at 615 nm occurs upon addition of citrate within a short 5-min incubation time at neutral pH. This is accompanied by a threefold increase of the luminescence decay time. The optimal conditions for determination of OxTc are equal concentrations of Eu (III) and citrate (C = 1 · 10^− 4 mol L^− 1) and pH 7.2. For determination of citrate, the optimal concentrations of Eu(III) and OxTc are 1 : 0.5 (C_Eu = 1 · 10^− 4 mol L^− 1, C_OxTc = 5 · 10^− 5 mol L^− 1) at pH 7.2. The linear range for determination of OxTc in serum is 0.25-250 μg mL^− 1, and for citrate in tablets from 0.5 to 10.0 μg mL^− 1 (2.3 · 10^− 6- 4 · 10^− 5 mol L^− 1). The detection limit was 0.1 μg mL^− 1 for OxTc and 0.2 μg mL^− 1 (1 · 10^-6 mol L^− 1) for citrate, respectively. A comparison of the new method with other methods for determination of citrate is given.     

Application of sequential injection-square wave voltammetry (SI-SWV) to study the adsorption of atrazine onto a tropical soil sample

Square wave voltammetry automated by sequential injection analysis was applied to determine the Freundlich adsorption coefficients for the adsorption of atrazine onto a clay rich soil. The detection limit in soil extracts was between 0.18 and 0.48 μmol L⁻¹, depending on the medium used to prepare the extracts (0.010 mol L⁻¹ KCl, CaCl₂ or HNO₃ and 0.0050 mol L⁻¹ H₂SO₄), all of them conditioned in 40 mmol L⁻¹ Britton-Robinson buffer at pH 2.0 in presence of 0.25 mol L⁻¹ NaNO₃. Also in soil extracts the linear dynamic range was between 1.16 and 18.5 μmol L⁻¹ (0.25-4.0 μg mL⁻¹), with a sampling frequency of 190 h⁻¹. The K_f Freundlich adsorption coefficient was 3.8 ± 0.2 μmol^1−1/n Lⁿ kg⁻¹ in medium of 0.010 mol L⁻¹ KCl or CaCl₂, but increased to 7.7 ± 0.1 and 9.0 ± 0.3 μmol^1−1/n Lⁿ kg⁻¹ in 0.010 mol L⁻¹ HNO₃ and 0.0050 mol L⁻¹ H₂SO₄, respectively. The increase of K_f was related to the decrease of pH from 6.4-6.7 in KCl and CaCl₂ to 3.7-4.0 in presence of HNO₃ or H₂SO₄, which favors protonation of atrazine, facilitating electrostatic attractions with negative charges of the clay components of the soil. The 1/n parameters were between 0.76 and 0.86, indicating that the isotherms are not linear, suggesting the occurrence of chemisorption at specific adsorption sites. No statistically significant differences were observed in comparison to the adsorption coefficients obtained by HPLC. The advantage of the proposed SI-SWV method is the great saving of reagent because it does not use organic solvent as in the case of HPLC (50% (v/v) acetonitrile in the mobile phase). Additionally the start up of SI-SWV is immediate (no column conditioning necessary) and the analysis time is only 19 s.     

Studying the distribution pattern of selenium in nut proteins with information obtained from SEC-UV-ICP-MS and CE-ICP-MS

In this work, size exclusion chromatography (SEC) with UV and inductively coupled plasma mass spectrometry (ICP-MS) detection was used to study the association of selenium to proteins present in Brazil nuts (Bertholletia excelsa) under five different extraction conditions. As expected, better solubilization of proteins was observed using 0.05 mol L⁻¹ sodium hydroxide and 1% sodium dodecylsulfate (SDS) in Tris/HCl buffer (0.05 mol L⁻¹, pH 8) as compared to 0.05 mol L⁻¹ HCl, 0.05 mol L⁻¹ Tris/HCl or hot water (60 °C). Due to non-destructive character of Tris-SDS treatment, this was applied for studying molecular weight (MW) distribution patterns of selenium-containing nut proteins. Three different SEC columns were used for obtaining complete MW distribution of selenium: Superdex 75, Superdex Peptide, and Superdex 200 were tested with 50 mmol L⁻¹ Tris buffer (pH 8), 150 mmol L⁻¹ ammonium bicarbonate buffer (pH 7.8), phosphate (pH 7.5), and CAPS (pH 10.0) mobile phases. Using Superdex 200 column, the elution of at least three MW fractions was observed with UV detection (200-10 kDa) and ICP-MS chromatogram showed the co-elution of selenium with the two earlier fractions. The apparent MWs of these selenium-containing fractions were respectively about 107 and 50 kDa, as evaluated from the column calibration. For further characterization of individual selenium species, the defatted nuts were hydrolyzed with proteinase K and analyzed by capillary electrophoresis (CE) with ICP-MS detection. The suitability of CE for the separation of selenite, selenate, selenocystine and selenomethionine in the presence of the nut sample matrix is demonstrated. Complete separation of the above mentioned selenium species was obtained within a migration time of 7 min. In the analysis of nut extracts with CE-ICP-MS, selenium was found to be present mainly as selenomethionine.     

SERS as an analytical tool in environmental science: The detection of sulfamethoxazole in the nanomolar range by applying a microfluidic cartridge setup

Sulfamethoxazole (SMX) is a commonly applied antibiotic for treating urinary tract infections; however, allergic reactions and skin eczema are known side effects that are observed for all sulfonamides. Today, this molecule is present in drinking and surface water sources. The allowed concentration in tap water is 2·10⁻⁷ mol L⁻¹. SMX could unintentionally be ingested by healthy people when drinking contaminated tap water, representing unnecessary drug intake. To assess the quality of tap water, fast, specific and sensitive detection methods are required, in which consequence measures for improving the purification of water might be initiated in the short term. Herein, the quantitative detection of SMX down to environmentally and physiologically relevant concentrations in the nanomolar range by employing surface-enhanced Raman spectroscopy (SERS) and a microfluidic cartridge system is presented. By applying surface-water samples as matrices, the detection of SMX down to 2.2·10⁻⁹ mol L⁻¹ is achieved, which illustrates the great potential of our proposed method in environmental science.     

Synchronous fluorescence determination of DNA based on the interaction between methylene blue and DNA

The fluorescence intensity of methylene blue (MB) quenched by DNA in the pH range of 6.5-8.0 was studied with synchronous fluorescence technology. A novel method for detecting single-stranded and double-stranded DNA was developed. The decreased fluorescence intensity at 664 nm is in proportion to the concentration of DNA in the range of 0.28-11.0 μmol L⁻¹ for ctDNA, 0.14-8.25 μmol L⁻¹ for thermally denatured ctDNA and 0.28-8.25 μmol L⁻¹ for hsDNA. The detection limits (S/N = 3) are 0.11, 0.04 and 0.04 μmol L⁻¹, respectively. The method is rapid, selective, and the reagents are lower toxic. It has been used for the determination of DNA in synthetic samples with good satisfaction. In addition, the interaction modes between MB and ctDNA and the mechanism of the fluorescence quenching were also discussed in detail. The experimental results from absorption spectra and fluorescence polarization indicate that the possible interaction modes between MB and DNA are the electrostatic binding and the intercalation binding.     

Carbon Electrode Material with High Densities of Energy and Power

Activated carbon (AC) samples as electrode materials were prepared by means of simultaneous physical-chemical activation using walnut shells as precursors. The porosity and surface chemistry of the resultant AC samples were studied by the nitrogen adsorption at 77 K, and FTIR spectrum. The testing supercapacitors were assembled with resultant carbon electrode and electrolyte of 6 mol·L⁻¹ KOH solution. Their electrochemical properties were investigated by charge-discharge of constant current, cyclic voltammogram, impedance spectrum and so on. The results showed that the capacitor had low inner resistance, low leakage current, high stability, and capacitance retainability. The specific capacitance of AC increased with increasing BET specific surface area. The specific capacitance of the AC sample with a specific area of 1197 m²·g⁻¹ could be as high as 292 F·g⁻¹. At a discharge current of 80 mA, the corresponding specific energy density, power density, and maximum power of the supercapacitor are 7.3 Wh·kg⁻¹, 770 W·kg⁻¹, and 5.1 W·g⁻¹, respectively.     

Differential pulse voltammetric simultaneous determination of noradrenalin and acetaminophen using a hematoxylin biosensor

A highly efficient noradrenalin (NA) biosensor was fabricated on the basis of hematoxylin electrodeposited on a glassy carbon electrode, GCE. The cyclic voltammetric responses of the hematoxylin biosensor at various scan rates, which were obtained in a 0.25 mmol L⁻¹ NA solution, showed the characteristic shape typical of an EC_cat process. The kinetic parameters such as electron transfer coefficient, α, the catalytic electron transfer rate constant, k′, and the standard catalytic electron transfer rate constant, k⁰, for oxidation of NA at the hematoxylin biosensor surface were estimated using cyclic and RDE voltammetry. The peaks of differential pulse voltammetric (DPV) for NA and acetaminophen (AC) oxidation at the hematoxylin biosensor surface were clearly separated from each other when they co-exited in the physiological pH (pH 7.0). It was, therefore, possible to simultaneously determine NA and AC in the samples at a hematoxylin biosensor. Linear calibration curves were obtained for 5.0 × 10⁻¹ to 65.40 μmol L⁻¹ and 65.40-274.20 μmol L⁻¹ of NA, and for 12.00-59.10 μmol L⁻¹ and 59.10-261.70 μmol L⁻¹ of AC. The sensitivities of the biosensor to NA in the absence and presence of AC were found virtually the same, which indicates the fact that the electrocatalytic oxidation processes of NA are independent of AC and, therefore, simultaneous or independent measurements of the two analytes (NA and AC) are possible without any interference. The results of 16 successive measurements show an average voltammetric peak current of 1.13 ± 0.03 μA for an electrolyte solution containing 5.00 μmol L⁻¹ NA. The hematoxylin biosensor has been satisfactorily used for the determination of NA and AC in pharmaceutical formulations. The results obtained, using the biosensor, are in very good agreement with those declared in the label of pharmaceutical inhalation products.     

Simultaneous voltammetric determination of paracetamol and caffeine in pharmaceutical formulations using a boron-doped diamond electrode

A simple and highly selective electrochemical method was developed for the single or simultaneous determination of paracetamol (N-acetyl-p-aminophenol, acetaminophen) and caffeine (3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione) in aqueous media (acetate buffer, pH 4.5) on a boron-doped diamond (BDD) electrode using square wave voltammetry (SWV) or differential pulse voltammetry (DPV). Using DPV with the cathodically pre-treated BDD electrode, a separation of about 550 mV between the peak oxidation potentials of paracetamol and caffeine present in binary mixtures was obtained. The calibration curves for the simultaneous determination of paracetamol and caffeine showed an excellent linear response, ranging from 5.0 × 10⁻⁷ mol L⁻¹ to 8.3 × 10⁻⁵ mol L⁻¹ for both compounds. The detection limits for the simultaneous determination of paracetamol and caffeine were 4.9 × 10⁻⁷ mol L⁻¹ and 3.5 × 10⁻⁸ mol L⁻¹, respectively. The proposed method was successfully applied in the simultaneous determination of paracetamol and caffeine in several pharmaceutical formulations (tablets), with results similar to those obtained using a high-performance liquid chromatography method (at 95% confidence level).     

利用辅助识别聚合物链制备牛血清白蛋白分子印迹聚合物

论文提出了一种新的蛋白质分子印迹方法, 即以聚乙烯醇接枝聚合物作为辅助识别聚合物链(ARPCs), 以丙烯酰胺为单体, 在丙烯酸酯树脂载体表面进行聚合, 制备牛血清白蛋白分子印迹树脂. 实验使用2.00 mol•L⁻¹氯化钾(KC1)溶液除去模板蛋白质, 使用十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)检测吸附蛋白质, 并设计使用0.150, 0.500和2.00 mol•L⁻¹KC1溶液分别对吸附蛋白质进行梯度洗提. 电泳实验结果表明, 2.00 mol•L⁻¹KC1溶液洗脱的蛋白质是大孔树脂的吸附效应; 0.500 mol•L⁻¹KC1溶液洗脱掉的是印迹蛋白质. 引入ARPCs制得的分子印迹树脂, 用于混合蛋白质体系吸附时, 对模板蛋白质的吸附量为80~100μg•g⁻¹, 其特异性吸附能力较未引入ARPCs之前有明显提高.