Prediction of the mean transit time using machine learning models based on radiomics features from digital subtraction angiography in moyamoya disease or moyamoya syndrome-a development and validation model study.

Background: Digital subtraction angiography (DSA) is an important technique for diagnosis of moyamoya disease (MMD) or moyamoya syndrome (MMS), and computed tomography perfusion (CTP) is essential for assessing intracranial blood supply. The aim of this study was to assess whether radiomics features based on images of DSA could predict the mean transit time (MTT; outcome of CTP) using machine learning models. Methods: The DSA images and MTT values of adult patients with MMD or MMS, according to the diagnostic guidelines for MMD, as well as control cases, were retrospectively collected in the Guangdong Provincial People's Hospital between January 2018 and December 2020. A total of 93 features were extracted from the images of each case through 3-dimensional (3D) slicer. After features preprocessing and filtering, 3-4 features were selected by the least absolute shrinkage and selection operator (LASSO) regression algorithm. Prediction models were established using random forest (RF) and support vector machine (SVM) for MTT values. Single-factor receiver operating characteristic (ROC) curve analysis and partial-dependence (PD) profiles were conducted to investigate selected features and prediction models. Results: Our results showed that prediction models based on RF models had the best performance in frontal lobe {area under the curve (AUC) [95% confidence interval (CI)] =1.000 (1.000-1.000)], parietal lobe [AUC (95% CI) =1.000 (1.000-1.000)], and basal ganglia/thalamus [AUC (95% CI) =0.922 (0.797-1.000)] in the test set, whereas the SVM model performed the best in the temporal lobe [AUC (95% CI) =0.962 (0.876-1.000)] in the test set. The AUC values in the test set were greater than 0.9. The PD profiles showed good robustness and consistency. Conclusions: Prediction models based on radiomics features extracted from DSA images demonstrate excellent performance in predicting MTT in patients with MMD or MMS, which may provide guidance for future clinical practice.

Small RNA sequencing reveals sex-related miRNAs in Collichthys lucidus.

Collichthys lucidus (C. lucidus) is an economically important fish species, exhibiting sexual dimorphism in its growth rate. However, there is a lack of research on its underlying sex-related mechanisms. Therefore, small RNA sequencing was performed to better comprehend these sex-related molecular mechanisms. In total, 171 differentially expressed miRNAs (DE-miRNAs) were identified between the ovaries and testes. Functional enrichment analysis revealed that the target genes of DE-miRNAs were considerably enriched in the p53 signaling, PI3K-Akt signaling, and TGF-beta signaling pathways. In addition, sex-related miRNAs were identified, and the expression of miR-430c-3p and miR-430f-3p was specifically observed in the gonads compared with other organs and their expression was markedly upregulated in the testes relative to the ovaries. Bmp15 was a target of miR-430c-3p and was greatly expressed in the ovaries compared with the testes. Importantly, miR-430c-3p and bmp15 co-expressed in the ovaries and testes. This research provides the first detailed miRNA profiles for C. lucidus concerning sex, likely laying the basis for further studies on sex differentiation in C. lucidus.

Whole-Genome Sequencing and Genome-Wide Studies of Spiny Head Croaker (Collichthys lucidus) Reveals Potential Insights for Well-Developed Otoliths in the Family Sciaenidae.

Spiny head croaker (Collichthys lucidus), belonging to the family Sciaenidae, is a small economic fish with a main distribution in the coastal waters of Northwestern Pacific. Here, we constructed a nonredundant chromosome-level genome assembly of spiny head croaker and also made genome-wide investigations on genome evolution and gene families related to otolith development. A primary genome assembly of 811.23 Mb, with a contig N50 of 74.92 kb, was generated by a combination of 49.12-Gb Illumina clean reads and 35.24 Gb of PacBio long reads. Contigs of this draft assembly were further anchored into chromosomes by integration with additional 185.33-Gb Hi-C data, resulting in a high-quality chromosome-level genome assembly of 817.24 Mb, with an improved scaffold N50 of 26.58 Mb. Based on our phylogenetic analysis, we observed that C. lucidus is much closer to Larimichthys crocea than Miichthys miiuy. We also predicted that many gene families were significantly expanded (p-value <0.05) in spiny head croaker; among them, some are associated with "calcium signaling pathway" and potential "inner ear functions." In addition, we identified some otolith-related genes (such as otol1a that encodes Otolin-1a) with critical deletions or mutations, suggesting possible molecular mechanisms for well-developed otoliths in the family Sciaenidae.

Whole genome re-sequencing identifies unique adaption of single nucleotide polymorphism, insertion/deletion and structure variation related to hypoxia in Tibetan chickens.

BACKGROUND: The adaptation to hypoxia in high altitude areas has great research value in the field of biological sciences. Tibetan chicken has unique adaptability to high-altitude, low pressure and anoxic conditions, and served as a biological model to search for genetic diversity of hypoxia adaption. METHODS: The whole genome re-sequencing technology was conducted to investigate the genetic diversity. RESULTS: In this study, we obtained quantity genetic resource, contained 5164926 single nucleotide polymorphisms (SNPs), 237504 Insertion/Deletion (InDel), 55606 structural variation types in all chromosomes of Tibetan chicken. Moreover, 17154 non-synonymous mutations, 45763 synonymous mutations, 258 InDel mutations and 9468 structural mutations were detected in coding sequencing (CDS) region. Furthermore, SNPs occur in 591 genes, including HIF1A, VEGF, MAPK 8/9/10/11, PPARA/D/G, NOTCH2, and ABCs, which were involved in 14 hypoxia-related pathways, such as VEGF signaling pathway, MAPK signaling pathway, PPAR signaling pathway and Notch signaling pathway. Among them, 19 genes with non-synonymous SNP variation in CDS were identified. Moreover, structure variation in CDS also occurred in the mentioned above genes with SNPs. CONCLUSIONS: This study provides useful targets for clarifying the hypoxia adaptability of the domestication of chickens in Tibetan and may help breeding efforts to develop improved breeds for the highlands.

Global tissue transcriptomic analysis to improve genome annotation and unravel skin pigmentation in goldfish.

Goldfish is an ornamental fish with diverse phenotypes. However, the limited genomic resources of goldfish hamper our understanding of the genetic basis for its phenotypic diversity. To provide enriched genomic resources and infer possible mechanisms underlying skin pigmentation, we performed a large-scale transcriptomic sequencing on 13 adult goldfish tissues, larvae at one- and three-days post hatch, and skin tissues with four different color pigmentation. A total of 25.52 Gb and 149.80 Gb clean data were obtained using the PacBio and Illumina platforms, respectively. Onto the goldfish reference genome, we mapped 137,674 non-redundant transcripts, of which 5.54% was known isoforms and 78.53% was novel isoforms of the reference genes, and the remaining 21,926 isoforms are novel isoforms of additional new genes. Both skin-specific and color-specific transcriptomic analyses showed that several significantly enriched genes were known to be involved in melanogenesis, tyrosine metabolism, PPAR signaling pathway, folate biosynthesis metabolism and so on. Thirteen differentially expressed genes across different color skins were associated with melanogenesis and pteridine synthesis including mitf, ednrb, mc1r, tyr, mlph and gch1, and xanthophore differentiation such as pax7, slc2a11 and slc2a15. These transcriptomic data revealed pathways involved in goldfish pigmentation and improved the gene annotation of the reference genome.

Identification of long noncoding RNAs involved in adaptability to chronic hypoxic by whole transcriptome sequencing.

Hypoxia affects the physiology of cells and organisms; however, the mechanisms associated with hypoxia adaptation remain unknown in Tibetan chickens. In this study, we aimed to identify long noncoding RNAs (lncRNAs) involved in hypoxia adaptation in Tibetan chickens and Daheng broilers, to provide insights into the mechanisms underlying hypoxia induction. RNA sequencing results revealed that a total of 5504 lncRNAs and 16,779 microRNAs were differentially expressed in four Tibetan chickens and four Daheng broilers; 70 lncRNAs were up-regulated and 113 lncRNAs were down-regulated in the Tibetan chickens compared to the expression levels in the Daheng broilers. The differentially expressed lncRNAs (DElncRNAs) were enriched in the following Gene ontology terms: protein complex localization, small-molecule metabolic process, and RNA splicing. Kyoto Encyclopedia of Genes and Genomes analyses revealed that the DElncRNAs were mainly enriched in pathways that regulate cell junctions and intercellular spaces and oxygen or energy metabolism, mainly involved in hypoxic adaption. Moreover, a predicted ceRNA network with five DElncRNAs interacted with three miRNAs that acted on 42 pathways through 19 target genes. Quantitative real-time polymerase chain reaction was used to verify that the expression levels of ENSGALG00000008047, ENSGALG00000050044, and ENSGALG00000053982 were significantly lower in Tibetan chickens than in the Daheng broilers, consistent with the RNA sequencing results. We obtained lncRNA expression profiles for the heart tissue of Tibetan chickens for the first time and have provided novel data that may aid research on biological adaptation to hypoxic stress.

High-throughput sequencing analysis identified microRNAs associated with egg production in ducks ovaries.

BACKGROUND: MicroRNAs (miRNAs) exist widely and are involved in multiple biological processes in ducks, whereas the regulatory mechanism of miRNAs in egg laying of ducks has remained unclear. This study aims to reveal key miRNAs involved in the regulation of egg production in duck ovaries. METHODS: High-throughput sequencing was performed on four egg-type duck ovaries and four egg-meat-type duck ovaries at the start of the egg-laying stage. Quantitative reverse transcription PCR (qRT-PCR) validation was performed on differentially expressed miRNAs (DE miRNAs). Gene network of DEmiRNA-mRNA-pathway was constructed by Cytoscape. RESULTS: A total of 251 know miRNAs and 1,972 novel miRNAs were obtained from whole clean reads. Among the known miRNAs, we identified 21 DEmiRNAs, including eight down-regulated and 13 up-regulated miRNAs in egg-type ducks compared with egg-meat-type ducks. Among the novel miRNAs, we identified 70 DEmiRNAs, including 58 down-regulated and 12 up-regulated in egg-type ducks compared with egg-meat-type ducks. The expression patterns of four miRNAs were verified by qRT-PCR. The DEmiRNAs were involved in the function of response to folic acid and the pathway of valine, leucine and isoleucine degradation. Specific target genes of DEmiRNAs enrichment was found in some egg-laying regulation pathways, such as dopaminergic synapse, ovarian steroidogenesis and oocyte meiosis. The DEmiRNA-mRNA-pathway network including three DEmiRNAs, nine mRNAs and 11 pathways. apl-miR-194-5p and apl-miR-215-5p may be potential key miRNAs in regulating egg laying. CONCLUSIONS: This study provided miRNAs profiles in ducks about egg laying and establish a theoretical basis for subsequent selection or modification of duck phenotypes at the molecular level.

Small RNA sequencing of pectoral muscle tissue reveals microRNA-mediated gene modulation in chicken muscle growth.

Sichuan mountainous black-bone (SMB) chicken is a small-sized black-feathered chicken breed with low amount of meat, while Dahen (DH) chicken has a larger body size and a faster growth rate. MicroRNAs (miRNAs) are involved in various physiological processes, but their role in chicken muscle growth remains unclear. We aimed to investigate the miRNAs and pathways participating in the muscle growth of chicken. MiRNA profiles of four SMB chickens and four DH chickens were detected by small RNA sequencing. A total of 994 known miRNAs were identified, among which gga-miR-1a-3p, gga-miR-148-3p and gga-miR-133a-3p exhibited the highest enrichment in both breeds of chickens. Thirty-two miRNAs were differently expressed between SMB and DH chickens. The differently expressed miRNAs were mainly associated with fatty acid metabolism, immunity and MAPK activation-related processes. Kyoto encyclopaedia of genes and genomes (KEGG) analysis showed that miRNAs were involved in the immunity-related and MAPK signalling pathways. Moreover, miR-204 was downregulated in DH chicken compared with SMB chicken, and significantly inhibited the expression of MAP3K13, which is involved in the MAPK pathway. It was confirmed through luciferase reporter assays that miR-204 specifically inhibited the activity of MAP3K13. Our results helped demonstrate the potential molecular mechanisms of muscle growth in chickens and provide valuable information for chicken breeding.

Novel miRNA identification and comparative profiling of miRNA regulations revealed important pathways in Jinding duck ovaries by small RNA sequencing.

Functional studies have revealed miRNAs play pivotal roles in ovulation and ovary development in mammalians, whereas little is known about the miRNA function in ducks. In this study, miRNA deep sequencing in the ovary tissues was carried out to obtain the miRNA profile from ovaries before oviposition (BO) and after oviposition (AO) in Jinding duck. Overall, an average of 23,128,075 and 26,020,523 reads were identified in the BO and AO samples, respectively, and 6739 miRNAs were identified from them through further mapping and analysis. Besides, 1570 miRNAs were identified as differentially expressed miRNAs compared with BO, including 493 miRNAs up-regulated and 1077 down-regulated in AO. Moreover, 2291 target genes were predicted from 443 significantly differentially expressed miRNAs. In addition, GO and KEGG pathway analysis indicated that target genes were enriched in some basic cell metabolism pathways as well as the productive pathways such as MAPK signaling pathway, gonadotropin-releasing hormone signaling pathway, TGF-beta signaling pathway which had been significantly changed. Our results helped to replenish the duck miRNA database and illustrate the potential mechanism of miRNA function in duck ovary development and reproduction process.

Cloning of hepatic lipase and the effects of dietary nutrition on hepatic lipase expression in genetically improved farmed tilapia (Oreochromis niloticus).

Hepatic lipase is an important gene in lipid metabolism, which is crucial in the growth of fish. In this study, the cDNA sequence of genetically improved farmed tilapia (GIFT) HL gene was cloned by aimed rapid amplification of cDNA ends (RACE) method. Then, the characteristics of HL were analyzed with bioinformatics methods, and the expression of HL was assessed by the quantitative real-time PCR. To study the regulation of HL expression, GIFT were fed with diets containing different contents of lipid (40, 80, and 120 g kg-1) and choline (500, 750, and 1000 mg kg-1) and fed with different frequencies (2 or 3 times/day) and amounts (20, 40, 60, 80, and g kg-1 of body weight). Our results revealed that the GIFT HL gene has a full length of 1872 bp, encoding 493 amino acids. Consistent with the study in other species, GIFT HL was specially expressed in the liver. The HL gene of GIFT shared identity of 60.9-96.6% with other species. The expression of HL in 120 g kg-1 dietary lipid and 1000 mg kg-1 dietary choline group was the highest in all groups (P < 0.01). The expression of HL was increased gradually with 3 times/day frequency. All these results revealed the cDNA sequence of GIFT HL, and the expression of HL was affected by dietary choline and lipid levels, feeding frequency, and amount. This would guide the aquaculture of GIFT in the future.

[Thermal desorption sampling-gas chromatography-tandem mass spectrometry with a carbonyl-iron powder composite silica monolithic column for enrichment and determination of pyrethroid pesticide residues in tea samples].

Long-term exposure to pyrethroid insecticides is detrimental to the nervous system, reproductive system, and immune system in humans. Therefore, enrichment detection of pyrethroid pesticides is imperative. In this study, a novel carbonyl-iron powder composite silica monolithic column was first prepared for the enrichment of pyrethroid pesticide residues in tea samples. Then, the target analytes were thermally desorbed and online-injected into a gas chromatography-tandem mass spectrometry (GC-MS/MS) system. In the present method, hydroxy-terminated polydimethylsiloxane (PDMS) was covalently bonded to the surface of the SiO2 network and subsequently bonded with the carbonyl-iron powder. After the target analytes were adsorbed and concentrated in the PDMS spots, high-frequency induction heating was used for GC-MS/MS sampling. Under the optimal conditions, the detection limits of the pyrethroid pesticide residues were 3.8 to 7.5 µg/kg, and the relative standard deviation was 3.2% to 6.8% (n=6). The extraction recovery ranged from 97.7% to 110.5%, and the correlation coefficient was ≥ 0.9960. In addition, the enrichment factor could reach 1000 times. PDMS materials show excellent adsorption properties for non-polar solutes. In our experiment, carbonyl iron powder-bonded monolithic columns were prepared on the basis of stir bar sorptive extraction (SBSE). Carbonyl iron powder magnetic particles were evenly implanted into the inorganic-organic hybrid cassia material for realizing rapid and uniform desorption upon electromagnetic induction heating. Under the premise of perfectly integrating the technical advantages of SBSE and solid-phase microextraction (SPME), the electromagnetic induction characteristics of carbonyl iron powder can be exploited for thermal desorption and directly combined with GC-MS to facilitate online analysis and solvent-free elution. Compared with the conventional SPME method, the proposed method has the advantages of high enrichment factor, large adsorption capacity of the column, reusability, high degree of automation, and good universality. This method has high significance for sample preparation and for the extraction of pesticide residues in complex matrices.

Determination of preservatives by integrative coupling method of headspace liquid-phase microextraction and capillary zone electrophoresis.

An integrative coupling method of headspace liquid-phase microextraction (HS-LPME) and capillary zone electrophoresis (CZE) was proposed in this paper. In the method, a separation capillary was used to create a microextraction droplet of the running buffer solution of CZE, hold the droplet at the capillary inlet, extract analytes of sample solutions in the headspace of a sample vial, inject concentrated analytes into the capillary and separate the analytes by CZE. The proposed method was applied to determine the preservatives of benzoic acid and sorbic acid in soy sauce and soft drink samples, in which the running buffer solution of 50 mmol/L tetraborate (pH 9.2) was directly used to form the acceptor droplet at the capillary inlet by pressure, and the preservatives in a 6-mL sample solution containing 0.25 g/mL NaCl were extracted at 90°C for 30 min in the headspace of a 14-mL sample vial. Then the concentrated preservatives were injected into the capillary at 10 cm height difference for 20 s and separated by CZE. The enrichment factors of benzoic acid and sorbic acid achieved 266 and 404, and the limits of detection (LODs) were 0.03 and 0.01 µg/mL (S/N=3), respectively. The recoveries were in the range of 88.7-105%. The integrative coupling method of HS-LPME and CZE was simple, convenient, reliable and suitable for concentrating volatile and semi-volatile organic acids and eliminating matrix interferences of real samples.

[On-line coupling of microcolumn electrophoresis and UV-Vis spectrophotometry].

In the present paper, a laboratory-made high-performance electrophoresis microcolumn unit was prepared for UV-Vis spectrophotometer. X-ray diffraction was used in the preparation of electrophoretic microcolumns. And an analytical technique of microcolumn electrophoresis coupled with UV-Vis spectrophotometry was introduced. Uniform quartz microncrystals were prepared by hydrothermal synthesis. Their crystalline phase and morphology were identified by X-ray diffraction and scanning electron microscope, respectively. The quartz microncrystals were packed into a 2-mm i. d. fused-silica tube to prepare the electrophoretic microcolumn. With 1.5 mmol x L(-1) disodium phosphate buffer solution (pH 11.5) containing 25% (phi) methanol and 10% (phi) acetonitrile, tryptophan, phenylalanine and tyrosine were on-line separated on line and detected by microcolumn electrophoresis coupled with UV-Vis spectrophotometry without derivatization. The limits of detection were 0.037, 0.20 and 0.20 micromol x L(-1), respectively. The separation efficiency of tryptophan was 4.5 x 10(4) plates/m. The sample capacity of the electrophoretic microcolumn achieved 35 microL. It was found that the electrophoretic microcolumn packed with quartz microncrystals was able to limit Joule heat, increase sample capacity and enhance detection sensitivity. The laboratory-made electrophoretic microcolumn could be a high-performance separation unit for conventional UV-Vis spectrophotometer. The on-line coupling of microcolumn electrophoresis and UV-Vis spectrophotometry could separate and determine samples with complicated matrices, reduce zone broadening and enhance separation efficiency, so expand the analytical function of spectrophotometer in the trace analysis of mixed components with overlapped spectra.

In-line coupling headspace liquid-phase microextraction with capillary electrophoresis.

An analytical technique of in-line coupling headspace liquid-phase microextraction (HS-LPME) with capillary electrophoresis (CE) was proposed to determine volatile analytes. A special cover unit of the sample vial was adopted in the coupling method. To evaluate the proposed method, phenols were used as model analytes. The parameters affecting the extraction efficiency were investigated, including the configuration of acceptor phase, kind and concentration of acceptor solution, extraction temperature and time, salt-out effect, sample volume, etc. The optimal enrichment factors of HS-LPME were obtained with the sample volume of about half of sample vials, which were confirmed by both the theoretical prediction and experimental results. The enrichment factors were obtained from 520 to 1270. The limits of detection (LODs, S/N=3) were in the range from 0.5 to 1 ng/mL each phenol. The recoveries were from 87.2% to 92.7% and the relative standard deviations (RSDs) were lower than 5.7% (n=6). The proposed method was successfully applied to the quantitative analysis of the phenols in tap water, and proved to be a simple, convenient and reliable sample preconcentration and determination method for volatile analytes in water samples.

Design and application of a novel integrated electrochemical hydride generation cell for the determination of arsenic in seaweeds by atomic fluorescence spectrometry.

An integrated electrochemical hydride generation cell, mainly composed of three components (a gas liquid separator, a graphite tube cathode and a reticulate Pt wire anode), was laboratory constructed and employed for the detection of arsenic by coupling to atomic fluorescence spectrometry. This integrated cell was free of ion-exchange membrane and individual anolyte, with the virtues of low-cost, easy assembly and environmental-friendly. Using flow injection mode, the sample throughput could come to 120 h(-1) attributed to the small dimension of the cathode chamber. The operating conditions for the electrochemical hydride generation of arsenic were investigated in detail and the potential interferences from oxygen or various ions were also evaluated. Under the optimized conditions, no obvious oxygen quenching effects were observed. The limit of detection of As (III) for the sample blank solution was 0.2 ng mL(-1) (3sigma) and the relative standard deviation was 3.1% for nine consecutive measurements of 5 ng mL(-1) As (III) standard solution. The calibration curve was linear up to 100 ng mL(-1). The accuracy of the method was verified by the determination of arsenic in the reference materials GBW08517 (Laminaria Japonica Aresch) and GBW10023 (Porphyra crispata) and the developed method was successfully applied to determine trace amounts of arsenic in edible seaweeds.

Electrophoretic separation with 2-mm inner diameter fused-silica microcolumn packed with quartz microncrystals and its application.

The feasibility of a microcolumn electrophoresis technique was investigated with a 100mm length, 2mm I.D. fused-silica microcolumn packed with uniform quartz microncrystals prepared by hydrothermal synthesis. To evaluate the separation technique, tryptophan, phenylalanine and tyrosine were primarily separated by the microcolumn electrophoresis and detected at 216 nm without derivatization by an ordinary spectrophotometer. The separation conditions of the amino acids were optimized. With 1.5 mmol/L disodium phosphate buffer solution (pH 11.5) containing 25% (v/v) methanol and 10% (v/v) acetonitrile, the three amino acids were separated and the separation efficiency of tryptophan was 4.5x10(4)plates/m. The limits of detection were 0.035, 0.22 and 0.20 micromol/L, respectively. The sample capacity of the electrophoretic microcolumn achieved 35 microL. The proposed method was used to determine these amino acids in compound amino acid injection samples without derivatization. For the simplicity and portability of the microcolumn electrophoresis, it is studied as one of the high-performance separation techniques for an in situ and real-time electrokinetic flow analysis system. For its high detection sensitivity and large sample capacity, it can be developed for preparative electrophoresis.

On-line wall-free cell for laser-induced fluorescence detection in capillary electrophoresis.

A wall-free detection method based on liquid junction in a capillary gap was proposed for laser-induced fluorescence (LIF) of capillary electrophoresis (CE). The capillary gap of the wall-free cell was fabricated by etching a 10-mm x 50-microm I.D. fused-silica capillary to obtain a polyimide coating sleeve, decoating about 6mm at one end of both 50 microm I.D. separation and liquid junction capillary, inserting the treated capillary ends into the coating sleeve oppositely, fixing the capillaries with a gap distance of 140 microm by epoxy glue and removing the coating sleeve by burning. The theoretical model, experimental results and wall-free cell images indicated that the gap distance and applied voltage were main influence factors on the wall-free detection. Since the wall-free cell increased the absorption light path and avoided the stray light from the capillary wall, it improved the ratio of signal to noise and limit of detection (LOD) of CE-LIF. Three flavin compounds of riboflavin (RF), flavin mononucleotide sodium (FMN) and flavin adenine dinucleotide disodium (FAD) were used to evaluate the wall-free detection method. Compared with on-column cell, the LODs of the wall-free cell were improved 15-, 6- and 9-fold for RF, FMN and FAD, respectively. The linear calibration concentrations of the flavins ranged from 0.005 to 5.0 micromol/L. The column efficiency was in the range from 1.0 x 10(5) to 2.5 x 10(5) plates. The wall-free detection of CE-LIF was applied to the analysis of the flavins in spinach and lettuce leaves.

On-column liquid-liquid-liquid microextraction coupled with base stacking as a dual preconcentration method for capillary zone electrophoresis.

A simple and efficient dual preconcentration method of on-column liquid-liquid-liquid microextraction (LLLME) coupled with base stacking was developed for capillary zone electrophoresis (CZE) in this paper. Four N-methyl carbamates were used as target compounds to evaluate the enrichment means. The carbamates in sample solutions (donor phase) were extracted into a dodecanol phase immobilized on a porous hollow fiber, hydrolyzed and back extracted into 0.20 microL running buffer (acceptor phase) of 30 mmol/L methylamine hydrochloride (pH 11.6) containing 0.5 mmol/L tetradecyltrimethylammonium bromide inside the hollow fiber, stacked further with 0.5 mol/L NaOH injected at -10 kV for 60s, and separated by CZE. Analytical parameters affecting the LLLME, base stacking and CZE were investigated, including sample solution volume, pH and temperature, extraction time, stirring rate, buffer component, buffer pH, NaOH concentration, stacking time, etc. The enrichment factors of the carbamates were higher than 1100. The relative standard deviation (RSD) of peak height and limits of detection (LODs) were 4.5-5.5% (n=6) and 2-4 ng/mL (S/N=3) for standard solutions, respectively. The proposed method was applied to the analysis of vegetable and fruit samples with the RSD less than 6.0% (n=3) and LODs of 6-10 ng/g (S/N=3). The calibration solutions were prepared by diluting the stock solutions with blank sample solutions, and the calibration concentrations ranged from 0.012 to 1.0 microg/mL (r>0.9951). The analytical results demonstrated that the LLLME coupled with base stacking was a simple, convenient and reliable on-column sample pretreatment method for the analysis of anionic analytes in CZE.

Determination of kanamycin A, amikacin and tobramycin residues in milk by capillary zone electrophoresis with post-column derivatization and laser-induced fluorescence detection.

An analytical method for kanamycin A, amikacin and tobramycin of aminoglycoside (AG) antibiotics in milk samples was proposed using capillary zone electrophoresis (CZE) with post-column derivatization and laser-induced fluorescence detection. A simple and convenient homemade coaxial-gap reactor was adopted in the post-column derivatization of the AGs with 1.0 mmol/L naphthalene-2,3-dicarboxaldehyde and 8.0 mmol/L 2-mercaptoethanol in 35 mmol/L sodium tetraborate buffer (pH 10.0) of 30% (v/v) methanol. 50 mmol/L sodium acetate (pH 5.0) containing 0.5 mmol/L cetyltrimethyl ammonium bromide was used as the separation buffer. The linear calibration concentrations and detection limits were from 2.1 x 10(-5) to 5.0 x 10(-2)g/L and in the range of 7 x 10(-6) to 2 x 10(-5)g/L, respectively. The recoveries of the AGs in milk samples were from 81.6 to 93.1% (n=3).

[Effect of acidity on the interaction of Ofloxacin and bovine serum albumin].

Bovine serum albumin (BSA) exists as N(pH -7.0), B(pH -9.0), and E (pH < 3.5) = isomeric forms in the solution of different pH. Acid effect on the structure of bovine serum albumin and the interaction of different structure of BSA with Ofloxacin were studied by UV-Vis and fluorescence spectroscopy. Based on the fluorescence quenching of bovine serum albumin and Förster energy transfer mechanism, the quenching constants, energy transfer efficiencies and the binding distances were determined at four different pHs. The results showed that Ofloxacin has the ability to quench bovine serum albumin fluorescence with the optimal condition of fluorescence quenching constants of 1.928 1 x 10(5) L x mo l(-1), binding distance of r = 2.55 nm and quenching efficiency of 8.63 x 10(4) L x mo x l(-1) at pH 4.9. Non-radiative energy transfer and static quenching were the cause of fluorescence quenching. The influence on the binding of Ofloxacin and bovine serum albumin under neutral, subacidity and alkalescent conditions was not obviously observed, and the electrostatic interaction was not the main force. The effect of Oflx on the conformation of BSA was also investigated using synchronous fluorescence spectrometry.