One-Step Synthesis of Water-Dispersible and Biocompatible Silicon Nanoparticles for Selective Heparin Sensing and Cell Imaging.

A sensitive and selective fluorescence "turn-off" sensor to detect heparin using water-soluble silicon nanoparticles (Si NPs) was developed for the first time. The Si NPs were synthesized by a simple one-step procedure, which did not need high-temperature and complex modification. The as-prepared Si NPs featured strong fluorescence, favorable biocompatibility, and robust photo- and pH stability. Significantly, the Si NPs were induced to assemble or aggregate via hydrogen bonding, which resulted in the fluorescence of Si NPs quenched. Under the optimized conditions, the linear range was obtained from 0.02 to 2.0 µg/mL, with a limit of detection of 18 ng/mL (equal to 0.004 U/mL). It was lower than the proper therapeutic level of heparin during cardiovascular surgery and long-term therapy. This proposed method was relatively free of interference from heparin analogues, which commonly existed in heparin samples and could possibly affect heparin detection. Moreover, it did not need to introduce any control medium. As expected, the method was successfully applied to detect heparin in human serum samples with satisfactory recovery ranging from 98.8 to 102.5%. The Si NPs were superbly suitable for cell imaging owing to the negligible cytotoxicity and excellent biocompatibility.

Detection of biogenic amines in C57BL/6 mice brain by capillary electrophoresis electrokinetic supercharging.

Ischemic stroke is caused when blood flow to the brain is stopped and is a major cause of death and long term disability across the globe. Excessive release of neurotransmitters is triggered in the brain by ischemia that mediates neuronal damage and causes ischemic injury. In this study, a simple, sensitive, and on-line preconcentration capillary electrophoresis method based on electrokinetic supercharging (EKS) was developed for the determination of the biogenic amines including dopamine (DA), epinephrine (E), and norepinephrine (NE) in C57BL/6 mice brain. Under the optimized conditions, the analytes were concentrated and detected within 10 min. The detection limits for the analytes ranged from 0.42 to 0.57 ng mL(-1) for a mice brain matrix. With the proposed method, the analyses of three neurochemical amines in C57BL/6 mice brain tissue during cerebral ischemic/reperfusion had been performed successfully.

Determination of enantiomers by FESI-sweeping with an acid-labile sweeper in nonaqueous capillary electrophoresis.

In this work, a facile and highly efficient on-line concentration strategy based on a coupling of field enhanced sample injection (FESI) and sweeping was developed for the determination of trace enantiomers (propranolol, PL) by nonaqueous capillary electrophoresis (NACE). In this FESI-sweeping method, the use of a sample of high acidity and low conductivity (pH* = 2.5, 4.0 µS cm(-1)) allowed for a large amount of analyte injection. Then, the concentration of the analytes was carried out by sweeping based on the interaction of an acid-labile anionic selector, di-n-butyl L-tartrate-boric acid complex acid, and cationic analytes. Simultaneously, the concentrated analytes were released and focused at the boundary of the acid sample solution and separation buffer due to the decomposition of the selector in the acid sample solution. Under the optimum conditions, a 21,000-fold sensitivity enhancement upon normal capillary zone electrophoresis (CZE) was achieved for PL enantiomers. The detection limits of R-propranolol and S-propranolol were 0.26 ng mL(-1) and 0.31 ng mL(-1), respectively. Eventually, the FESI-sweeping method was applied to detect PL enantiomers in plasma, saliva, and urine.

Chiral separation of ß-blockers by MEEKC using neutral microemulsion: Analysis of separation mechanism and further elucidation of resolution equation.

Based on the investigation of the effect of microemulsion charge on the chiral separation, a new chiral separation method with MEEKC employing neutral microemulsion was established. The method used a microemulsion containing 3.0% (w/v) neutral surfactant Tween 20 and 0.8% (w/v, 30 mM) dibutyl l-tartrate in 40 mM sodium tetraborate buffer to separate the enantiomers of ß-blockers. The effect of major parameters on the chiral separation was investigated. The applied voltage had little effect on the resolution, but the chiral separation could be improved by suppressing the EOF. Nine racemic ß-blockers obtained relatively good enantioseparation after appropriate concentrations of tetradecyl trimethyl ammonium bromide were added into the microemulsion to suppress the EOF. These results were explained based on the analysis of the separation mechanism of the method and deduced separation equations. The resolution equation of the method was further elucidated. It was found that the fourth term in the resolution equation, an additional term compared to the conventional resolution equation for column chromatography, represents the ratio of the relative movement distance between the analyte and microemulsion droplets relative to the effective capillary length. It can be regarded as a correction for the effective capillary length. These findings are significant for the development of the theory of MEEKC and the development of new chiral MEEKC method.

[Recent developments in the application of covalent organic frameworks in capillary electrochromatography].

Capillary electrochromatography (CEC) has received increased attention from the academic community because it combines the excellent selectivity of high performance liquid chromatography (HPLC) and the high efficiency of capillary electrophoresis (CE). Selecting the most appropriate stationary phase material is crucial to achieve better separation effects in CEC. In recent years, a considerable number of materials, such as graphene oxide, proteins, metal organic frameworks, and covalent organic frameworks (COFs), have been widely used as stationary phases in CEC to further improve its separation performance and extend its scope of potential applications. Among these materials, COFs have shown great application prospects in CEC owing to their unique properties, which include high porosity, large surface area, excellent stability, tunable pore size, and high designability of the framework structure. This review systematically summarizes published papers on the development and application of COFs in CEC from 2016 to 2023. First, two COF-based capillary columns (i. e., open-tube CEC columns and monolithic CEC columns) and their preparation methods are introduced. Second, the applications of CEC based on COF stationary phases in the separation of environmental endocrine disruptors, pesticides, aromatic compounds, amino acids, and drugs, particularly chiral drugs, are systematically summarized. The separation mechanism of CEC based on COF stationary phases is also introduced. At present, the good separation ability of COF-based CEC is mainly attributed to two factors: 1) The size exclusion effect of the pores of the COF stationary phase. Because of differences in the sizes of their organic molecular building units and side chains, COFs have varying pore sizes and topological structures. Thus, target analytes smaller than the pores of the COFs can enter the frameworks and interact with them during separation. On the other hand, target analytes larger than the pores of the COFs cannot enter the frameworks and interact with them during separation; thus, they can be separated. 2) The interactions between the target analytes and side chains (e. g., hydrophobic interactions, hydrogen bonding, π-π interactions, etc.) of the COFs. Since COFs usually contain alkyl side chains, aromatic structures, and oxygen and/or nitrogen atoms with high electronegativity, various interactions could occur between the COFs and target analytes. Finally, directions for the future development and strategic application of CEC based on COF stationary phases are proposed. We believe that future research in CEC based on COF stationary phases should focus on the following aspects: 1) The use of cheminformatics to design and construct COFs to improve the efficiency of COF capillary column preparation; 2) the development of milder methods to synthesize COFs that can meet the requirements of high performance COF capillary columns; and 3) in-depth research to explore the separation mechanism of CEC based on COF stationary phases to provide theoretical guidance for developing CEC methods suitable for the separation and analysis of complex samples.

A novel cross-H-channel interface for flow injection-capillary electrophoresis to reduce sample requirement and improve sensitivity.

In this study, a cross-H-channel interface was constructed for coupling flow injection with capillary electrophoresis (FI-CE) to reduce sample requirement and sensitivity loss in the typical FI-CE. Based on this cross-H-channel interface, a new FI-CE system was established, in which sample introduction was performed by directly injecting sample solution along a thin capillary (50 µm, i.d.) to the interface from an injection syringe. The sample requirement was reduced distinctly and usual sample dilution in the sample transport process was obviously decreased, thereby spontaneously enhancing the sensitivity. Moreover, because of the unique construction of the cross-H-channel interface, field amplified sample stacking (FASS) and high-speed CE were skillfully combined to further improve the sensitivity and to shorten separation time. The versatility of this new FI-CE was demonstrated by determination of ephedrine (E) and pseudoephedrine (PE) in human urine. Up to 45 repeated injections per hour and clearly baseline separation of E and PE in less than 1 min were achieved, giving limits of detection (LODs) of 0.23 and 0.21 µg mL(-1) for E and PE, respectively, and yielding relative standard deviation (RSD) values of the migration time and the peak height (n=5) of 2.6% and 3.1% for E, 2.3% and 3.3% for PE, respectively. In contrast to typical FI-CE, approximately 8-250-fold decreases in sample volume requirement, 7-fold shortening in separation time and 50-fold improvements in sensitivity were obtained.

Aqueous synthesis of CdTe/CdSe core/shell quantum dots as pH-sensitive fluorescence probe for the determination of ascorbic acid.

By controlling the reflux time and the quantity of the shell materials, different sizes of thioglycollic acid (TGA) modified CdTe/CdSe core/shell quantum dots were synthesized in aqueous solution. This type of QDs was used for sensitive and selective determination of ascorbic acid in commercial tablets. Under optimal conditions, a good linearity was observed between the relative fluorescence (FL) intensity and the concentration of ascorbic acid in the range of 4.0 to 64.0 µg/mL with a correlation coefficient of 0.9968. The limit of detection was 2.4 µg/mL. This method was applied to the determination of the ascorbic acid in Vitamin C tablets and Vitamin C Yinqiao pills, and satisfactory results were obtained.

Preparation of guanidine group functionalized magnetic nanoparticles and the application in preconcentration and separation of acidic protein.

Guanidine group (Gnd) functionalized magnetic nanoparticles (Fe3O4@SiO2@NH2-Gnd) were synthesized and characterized in this work for the first time. The characterization of Fe3O4@SiO2@ NH2-Gnd nanoparticles was demonstrated by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectra, vibration sample magnetometer, and zeta potential analyzer. The novel multifunctional nanoparticles were served as a solid-phase extraction sorbent for easy isolation and preconcentration of acidic protein from aqueous solution only using a magnet. Bovine serum albumin (BSA) was selected as a model protein and the main experimental parameters influencing the adsorption and desorption efficiency were investigated and optimized. Under the optimum conditions, the particles reached saturated adsorption within 20 min and exhibited significant specific recognition for the acidic proteins. Fifteen fold enrichment efficiency was achieved and the detection limits was 45 ng x mL(-1) for BSA by capillary electrophoresis (CE). The practical application of the novel nanoparticles as a sorbent for the isolation and preconcentration of acidic proteins from basic proteins was demonstrated by effective separation and enrichment of bovine serum albumin from lysozyme and cytochrome C mixture, which was assayed by CE.

Extremely large volume electrokinetic stacking of cationic molecules in MEKC by EOF modulation with strong acids in sample solutions.

In this report, a novel facile way of online preconcentration of trace levels of analytes in capillary electrophoresis is presented. The proposed strategy is based on the combination of strong acidic phosphate as sample buffers with borate separation buffer containing sodium dodecyl sulfate. When injection voltage is applied, the continuous introduction of low pH sample causes the apparent bulk flow inside the capillary gradually slows down. Finally at a certain point, it reaches the same magnitude as that of the oppositely migrating anionic micelles, thus the frontier of the micelle zone becomes stagnant. This steady state can be maintained for a very long time so that essentially extremely large volume of sample solutions can be injected into the capillary, and the cationic analytes may be efficiently stacked at the neutralized micelle zone. A theoretical model was proposed and preconcentration conditions of two model analytes, matrine and oxymatrine, were optimized with the aid of the model. Under optimized conditions, more than 1000-fold increase in sensitivity was obtained as compared with the normal hydrodynamic injection without sample stacking. The limits of detection for oxymatrine and matrine were 0.81 and 0.18 ng/mL, respectively, using photodiode array UV detection at wavelength 211 nm.

The combination of flow injection with electrophoresis using capillaries and chips.

The technique of combined flow injection CE (FI-CE) integrates the essential favorable merits of FI and CE. It utilizes the various excellent on-line sample pretreatments and preconcentration (such as cloud point extraction, SPE, ion-exchange, dynamic pH junction and head-column field-amplified sample stacking technique) of FI, which has the advantages of high speed, accuracy, precision and avoiding manual handling of sample and reagents. Therefore, the coupling of FI-CE is an attractive technique; it can significantly expand the application of CE and has achieved many publications since its first appearance. The basic principles, instrumental developments and applications of FI-CE system from 2006 to 2008 are reviewed.

In situ preparation of multilayer coated capillary column with HKUST-1 for separation of neutral small organic molecules by open tubular capillary electrochromatography.

The popularity of novel nanoparticles coated capillary column has aroused widespread attention of researchers. Metal organic frameworks (MOFs) with special structure and chemical properties have received great interest in separation sciences. This work presents the investigation of HKUST-1 (Hong Kong University of Science and Technology-1, called Cu3(BTC)2 or MOF-199) nanoparticles as a new type of coating material for capillary electrochromatography. For the first time, three layers coating (3-LC), five layers coating (5-LC), ten layers coating (10-LC), fifteen layers coating (15-LC), twenty layers coating(20-LC) and twenty-five layers coating (25-LC) capillary columns coated with HKUST-1 nanoparticles were synthesized by covalent bond with in situ, layer-by-layer self-assembly approach. The results of scanning electron microscopy (SEM), X-ray diffraction (XRD) and plasma atomic emission spectrometry (ICP-AES) indicated that HKUST-1 was successfully grafted on the inner wall of the capillary. The separating performances of 3-LC, 5-LC, 10-LC, 15-LC, 20-LC and 25-LC open tubular (OT) capillary columns were studied with some neutral small organic molecules. The results indicated that the neutral small organic molecules were separated successfully with 10-LC, 15-LC and 20-LC OT capillary columns because of the size selectivity of lattice aperture and hydrophobicity of organic ligands. In addition, 10-LC and 15-LC OT capillary columns showed better performance for the separation of certain phenolic compounds. Furthermore, 10-LC, 15-LC and 20-LC OT capillary columns exhibited good intra-day repeatability with the relative standard deviations (RSDs; %) of migration time and peak areas lying in the range of 0.3-1.2% and 0.5-4.2%, respectively. For inter-day reproducibility, the RSDs of the three OT capillary columns were found to be lying in the range of 0.3-5.5% and 0.3-4.5% for migration time and peak area, respectively. The RSDs of retention times for column-to-column for three batches of 10-LC, 15-LC and 20-LC OT capillary columns were in the range from 2.3% to 7.2%. Moreover, the fabricated 10-LC, 15-LC and 20-LC OT capillary columns exhibited good repeatability and stability for separation, which could be used successively for more than 120 runs with no observable changes on the separation efficiency.

Interaction of DNA with aromatic hydrocarbons fraction in atmospheric particulates of Xigu District of Lanzhou, China.

Voluminously epidemiological studies show that the relationships exist between the air pollution and human health and cancer. Aromatic hydrocarbons (AHs) in air form a large class of organic pollutants, which are widely in environment and many of them are known to be carcinogenic and/or mutagenic and contribute to ambient air pollution. In the past decades, bioassays mainly have been used to evaluate the toxicity of chemical mixtures in atmospheric particulates or aqueous environment. However, it is well known that the covalent complexes formed by carcinogens with DNA may be exert negative results in bioassay. So the main aim of this paper is to develop an evaluation method of toxicity effects of chemical mixtures in atmospheric particulates from chemical standpoint. In this study, the in vitro interaction of the AHs with DNA was investigated by absorption, fluorescence and resonance light scattering (RLS) spectroscopic techniques. The results showed that the AHs in the atmospheric particulates could combine with calf thymus DNA (ctDNA) and herring sperm DNA (hsDNA) without being activated or metabolized by organism, respectively. Intercalation may be present in the mechanism of interaction. The binding constants of the AHs with ctDNA and hsDNA were 2.5 x 10(2) and 2.0 x 10(3), respectively, which indicated that the interaction of the AHs with hsDNA is stronger than that with ctDNA. In addition, the relationships of dose-effect between the total mole concentration of chemical components and the ability of binding ctDNA and hsDNA were confirmed. This research made it possible to study the toxicity effects of chemical mixtures in atmospheric particulates by chemical method. It is believed that the composition and contents of unknown AHs and the interaction of DNA with AHs in atmospheric particulates of Xigu District of Lanzhou City, China are first reported in the past twenty years.

[Determination of tetrandrine and fangchinoline in Radix Stephaniae tetrandrae and its preparation by nonaqueous capillary chromatography].

OBJECTIVE: To establish a new method for the determination of fangchinoline and tetrandrine in Stephania tetrandra and Fengtongan capsule by noanqueous capillary electrophoresis. METHOD: Separation was carried out in an uncoated fused capillary (50 cm x 75 microm i.d.) with a running buffer containing 50 mmol x L(-1) ammonium acetate, 1.0% acetic acid and 20% acetonitrile in methanol. A separation voltage of 20 kV and a UV detector wavelength at 214 nm were adopted. Sample was introduced from the anode. RESULT: The calibration ranges were 1.00, 500 mg x L(-1) for both analytes. Under the optimum conditions, the relative standard deviation (RSD, n = 6) for the migration time of each analyte were 0.09%, 1.9% (intra-day) and 0.63%, 1.9% (inter-day); The RSD for the peak area of each analyte were 0.45%, 5.9% (intra-day) and 2.3%, 5.6% (inter-day), respectively. The contents of the analytes were determined easily with average recoveries 102% for fangchinoline and 105% for tetrandrine in S. tetrandra and 94.6% for fangchinoline and 98.7% for tetrandrine in Fengtongan capsules, respectively. CONCLUSION: The proposed method is simple, rapid, accurate and higher repeatable, and can be used to control of the quality of S. tetrandra and Fengtongan capsules.

Enhanced photoluminescence of morin-bovine serum albumin on porous anodized aluminum oxide.

In this paper, the photoluminescence (PL) of porous anodized aluminum oxide (AAO) impregnated with essentially nonfluorescent morin and morin-bovine serum albumin (BSA) was investigated for the first time, respectively. The evident PL bands similar to that of morin-Al3+ complex in solution were observed and the intensity of the latter with morin-BSA was much greater than that of the former with only morin. Moreover, the enhancement increased with the larger pore diameter of the AAO membranes. The appearance of PL bands might be ascribed to the formation of morin-Al complexes in the AAO pores with its inner wall involved. A likely orderly luminescent model was proposed to be responsible for the observed enhancing phenomena of PL due to the coexistence of morin and BSA in the AAO pores.

[Using GST-tag to capture protein interaction of an interferon-inducible systemic lupus associated gene, IFIT1].

OBJECTIVE: To investigate the protein-to-protein interaction of interferon-induced protein with tetratricopeptide repeats 1 (IFIT1), a newly discovered systemic lupus erythematosus (SLE) related up-regulated gene, and its possible function. METHODS: Peripheral blood of 40 SLE patients was obtained to extract total RNA and synthesized cDNA. Real-time PCR was used to determine the IFIT1 expression at transcript level. Peripheral blood of another 10 SLE patients was extracted to obtain specimens of white blood cell lysate. Molecular cloning and a modified gluthion S-transferase (GST)-pull down assay were used to capture the protein interacting with IFIT1 in the specimens of white blood cell lysate. MALDI-TOF mass spectrometry (MS) was preformed to identify the captured protein that could interact with IFIT1. Twenty-nine sex and age-matched healthy persons were used as controls. RESULTS: By real-time PCR showed that the IFIT1Delta Ct value (x +/- s) was 2.344 +/- 1.200 in the SLE patients and was 3.734 +/- 1.274 in the controls (P < 0.001), showing a significant up-regulation in SLE patients. IFIT1 was cloned and GST-IFIT1 fusion protein was expressed in Escherichia coli. GST-IFIT1 fusion protein was further purified using Glutathione Sepharose 4B column, and was treated as bait to capture prey from peripheral white blood cell lysate of SLE patients. MALDI-TOF MS detected protein interaction between Rho/Rac guanine nucleotide exchange factor and IFIT1. CONCLUSION: IFIT1 may interact with Rho/Rac guanine nucleotide exchange factor, and regulate the activation of Rho/Rac proteins, thus being involved in the pathogenesis of SLE.

[Interferon-inducible genes lymphocyte antigen 6 complex E and tetratricopeptide repeats 1 are correlated with clinical features of patients with systemic lupus erythematosus].

OBJECTIVE: To investigate the expression levels of lymphocyte antigen 6 complex, locus E (LY6E) and interferon-induced protein with tetratricopeptide repeats 1 (IFIT1) genes in the peripheral blood mononuclear cells (PBMCs) of patients with systemic lupus erythematosus (SLE), and to evaluate the relations between these gene expression levels and disease activity. METHODS: The clinical data of 144 SLE patients, 27 non-SLE patients with rheumatic diseases, and 59 normal controls were collected. The SLE patients were further divided into 2 subgroups: active SLE group (n = 87) and non-active SLE group (n = 57) according to SLEDAI scores. Specimens of peripheral blood were drawn; total RNA was extracted and transcribed into cDNA. Sybr green dye based real-time quantitative PCR method was used to compare the expression levels (indicated as-DeltaDeltaCT value) of LY6E and IFIT1 in patients with SLE and those in the controls. RESULTS: (1) The-DeltaDeltaCT value of LY6E expression level of the SLE patients was 5.4760 +/- 1.9806, significantly higher than those of the non-SLE patients (3.4323 +/- 1.7456) and normal controls (4.5198 +/- 1.6359, both P = 0.001). (2) The-DeltaDeltaCT value of LY6E and IFIT1 mRNA expression of the active SLE patients were 6.1960 +/- 1.7729 and 6.4997 +/- 2.6297 respectively, significantly higher than those observed in the inactive SLE patients (4.3770 +/- 1.7764 and 4.1327 +/- 2.6044 respectively, both P = 0.000). The-DeltaDeltaCT values of LY6E and IFIT1 mRNA of the SLE patients were correlated with the SLEDAI scores, and with the numbers of matched criteria used in the diagnosis of SLE (P < 0.001). CONCLUSION: As IFN-induced genes, elevated expression of LY6E mRNA is specific to diagnosis of SLE. The real time expression levels of LY6E and IFIT1 genes are associated with SLE disease activity. To inhibit the expression of LY6E and IFIT1 may become a novel therapeutic approach for SLE.

[Determination of active anthraquinones in Rheum and its tea preparations by micellar electrokinetic capillary electrophoresis].

OBJECTIVE: To establish an instant determination method of emodin, aloe-emodin and rhein, from Rheum, and one of their preparations, Qinghai Wild Dahuang Tea, by micellar electrokinetic capillary electrophoresis for the first time. METHOD: Separation was carried out in an uncoated fused silica capillary (75 microm x 50.0 cm). Meanwhile, a running voltage 20 kV, 15.0 mmol x L(-1) borax buffer with 30.0 mmol x L(-1) SDS and 10% ethanol (pH 9.60) and a UV detector at 254 nm were adopted. RESULT: The linear calibration rang was 4-120 mg x L(-1) (r = 0.992 1) for emodin, 10-200 mg x L(-1) (r = 0.997 0) for aloe-emodin, and 2-100 mg x L(-1) (r = 0.997 1) for rhein, respectively. Under the optimum conditions, the relative standard deviation (RSD) values (n = 6) for the migration time and the peak area of each peak were 0.59%-0.80%, 1.30%-3.22%, respectively. The contents of the analytes were easily determined with recoveries ranging from 97.6%-102.3%. CONCLUSION: The method is proved to be simple, rapid and accurate, and can be used for the quality control of medicinal herb, Rheum, and its tea preparation.

An ion-pair principle for enantioseparations of basic analytes by nonaqueous capillary electrophoresis using the di-n-butyl L-tartrate-boric acid complex as chiral selector.

A chiral recognition mechanism of ion-pair principle has been proposed in this study. It rationalized the enantioseparations of some basic analytes using the complex of di-n-butyl l-tartrate and boric acid as the chiral selector in methanolic background electrolytes (BGEs) by nonaqueous capillary electrophoresis (NACE). An approach of mass spectrometer (MS) directly confirmed that triethylamine promoted the formation of negatively charged di-n-butyl l-tartrate-boric acid complex chiral counter ion with a complex ratio of 2:1. And the negatively charged counter ion was the real chiral selector in the ion-pair principle enantioseparations. It was assumed that triethylamine should play its role by adjusting the apparent acidity (pH*) of the running buffer to a higher value. Consequently, the effects of various basic electrolytes including inorganic and organic ones on the enantioseparations in NACE were investigated. The results showed that most of the basic electrolytes tested were favorable for the enantioseparations of basic analytes using di-n-butyl l-tartrate-boric acid complex as the chiral ion-pair selector.

Preparation and characterization of open-tubular capillary column modified with graphene oxide nanosheets for the separation of small organic molecules.

A novel coated capillary was prepared by immobilizing graphene oxide (GO) on the fused-silica capillary (75 µm i.d.) which was derivatized by 3-aminopropyl-trimethoxysilane (APTMS). The bare capillary, APTMS modified capillary (NH2-capillary) and GO coated capillary (GO-capillary) were characterized by streaming potentials (SPs), fluorescence microscope and scanning electron microscope (SEM). The results indicated that the capillary was successfully modified with GO sheets via covalent bonding and electrostatic effect. Compared with bare capillary, greater separation efficiency was achieved by GO-capillary column as a result of the increasing interactions between the small organic molecules and the inner wall of the GO-capillary column originated from the π-π electrostatic stacking. For three consecutive runs, the intra-day relative standard deviations (RSDs) of migration time and peak areas were 0.6-4.3% and 2.8-9.3%, respectively. The inter-day relative standard deviations of migration time and peak areas were 0.2-8.3% and 4.5-9.6%. Additionally, one GO-capillary column could be used for more than 100 runs with no observable changes on the separation efficiency.

Binding of phthalate plasticizers to human serum albumin in vitro: a multispectroscopic approach and molecular modeling.

As endocrine-disrupting chemicals, a few frequently used phthalate plasticizers were banned or restricted for use as additives in food in some countries. The interaction mechanisms between three phthalate plasticizers with human serum albumin (HSA) were studied by fluorescence (quenching, synchronous, and three-dimensional), UV-vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy, in combination with molecular modeling under simulative physiological conditions, respectively. The results obtained from fluorescence quenching data revealed that the plasticizers-HSA interaction altered the conformational strcture of HSA. Meanwhile, the alterations of HSA secondary structure in the presence of phthalate plasticizers were investigated. The binding distances for the plasticizers-HSA system were provided by the efficiency of fluorescence resonance energy transfer. Furthermore, the thermodynamic analysis implied that hydrophobic forces were the main interaction for the plasticizers-HSA system, which agreed well with the results from the molecular modeling study.