Xiaoming Cai

Chinese Academy of Sciences, Peping, Beijing, China

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Publications (9)22.18 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Mixed-mode chromatography has received more and more attention due to its unique chromatographic characteristics recently. In this review, a summary of the development and applications of mixed-mode chromatography is presented. According to the types of hydrophilic interaction/ion-exchange mixed-mode chromatography (HILIC/IEX), reversed-phase/hydrophilic interaction mixed-mode chromatography (RPLC/HILIC) and reversed-phase/ion-exchange mixed-mode chromatography (RPLC/IEX), the preparation and applications of each type are introduced. Compared with single mode chromatography, the selectivity as well as the sample loading capacity of the mixed-mode chromatography can be improved. The researches mostly focus on the design of mixed-mode stationary phases and the applications especially to bio-analysis. The mixed-mode chromatography will be a potent approach for the analysis and separation of complex samples, and it will also be an effective and complementary tool in practical separation work.
    Se pu = Chinese journal of chromatography / Zhongguo hua xue hui 04/2013; 31(4):297-302.
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    ABSTRACT: A cysteine-bonded zwitterionic hydrophilic interaction chromatography (HILIC) stationary phase (Click TE-Cys) was prepared based on the "thiol-ene" click chemistry. The Click TE-Cys material was characterized by solid state ¹³C cross polarization/magic-angle spinning (CP/MAS) NMR and elemental analysis. The dynamic evaluation for cytosine, cytidine and orotic acid was performed using Van Deemter plots. The plate height values were no more than 24 μm for the flow rate between 0.5 and 5.4 mm s⁻¹ (0.3-3.5 mL min⁻¹), which proved the excellent separation efficiency of Click TE-Cys stationary phase. The influences of the content of water, concentration of salt and pH of the buffer solution on the retention of model compounds were investigated. The results demonstrated that the separation of polar analytes was dominated by the partitioning mechanism, while the contribution of electrostatic interaction was minor. The thermodynamic characteristic of Click TE-Cys stationary phase was also studied according to van't Hoff plot. An exothermic process for transferring analytes from the mobile phase to the stationary phase was observed and a linear relationship for ln k and 1/T was achieved, indicating no change of retention mechanism within the measured temperature range. Besides, the zwitterionic stationary phase exhibited good stability. Considering the high hydrophilicity of Click TE-Cys stationary phase, the application in the separation of protein tryptic digests was carried out using hydrophilic interaction chromatography-electrospray ionization mass spectrometry (HILIC-ESI-MS). More peaks were adequately resolved on the Click TE-Cys column comparing with that on the TSK Amide-80 column. In addition, the orthogonality between HILIC and RPLC system was investigated utilizing geometric approach. The XTerra MS C₁₈ and Click TE-Cys column displayed great difference in separation selectivity, with the orthogonality reaching 88.0%. On the other hand, the orthogonality between Click TE-Cys and TSK Amide-80 system was 21.4%, i.e. the selectivity was similar but slightly different from each other. The successful separation of protein digests indicated the great potential of Click TE-Cys stationary phase in the separation of complex samples and applicability in two-dimensional liquid chromatography (2D-LC).
    Journal of Chromatography A 11/2011; 1228:175-82. · 4.61 Impact Factor
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    ABSTRACT: In this study, plasma samples were collected from 28 health volunteers and 66 lung cancer patients. Ultraperformance HILIC/Q-TOF MS-based metabonomic techniques were employed to compare the highly polar metabolites (HPMs) in the plasma of patients with lung cancer and those in the plasma of healthy volunteers. High separation efficiency and good repeatability of the HILIC/Q-TOF MS method were observed. Partial least squares discriminant analysis (PLS-DA) of the data from both ESI+ and ESI− mode revealed good classifications between the health volunteer and the lung cancer patients. This result showed that the HPMs from lung cancer patients and healthy controls were significantly different. The correct classification rate of models in both ion modes reached 100%, indicating that the metabonomics method established in this study could predict the plasma samples with high accuracy. Besides, we found 19 ions that show a significant difference in levels between lung cancer patients and healthy controls. Finally, we conducted a primary study of the effect of radiotherapy on HPMs in lung cancer patients. Clear differences among the HPMs of patients in different radiotherapy periods and significant changes in levels of the 19 ions after radiotherapy were noted. This demonstrated that radiotherapy influences the metabolism system of patients. KeywordsUPLC/Q-TOF–Hydrophilic interaction chromatography–Metabonomics–Lung cancer–Highly polar metabolites–Radiotherapy
    Chromatographia 09/2011; 74(5):391-398. · 1.44 Impact Factor
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    ABSTRACT: Selection of a first-dimensional separation method is very important in proteomic studies performed with two-dimensional liquid chromatography (2D-LC), since reversed-phase chromatography (RPLC) is usually chosen as the second-dimensional separation method in most studies. In this paper, we assess the potential use of mixed-mode reversed-phase/weak cation-exchange (RP/WCX) chromatography in 2D-LC proteomic studies. First, a new RP/WCX mixed-mode stationary phase (named C18WCX) was synthesized based on the polar-copolymerized approach, and a C18WCX column with separation efficiency comparative to conventional C18 columns was developed. This new mixed-mode column primarily provides hydrophobic interactions under acidic condition, but can offer hydrophobic and cation-exchange interactions under neutral and weak basic conditions. An off-line 2D-RP/WCX-RPLC system was established using the C18WCX column with a mobile phase of pH 6.5 in the first dimension and a C18 column with a mobile phase of pH 3.0 in the second dimension. The orthogonality of this two-dimensional system, evaluated through the separation of 123 tryptic peptides, was shown to be higher than that of the conventional 2D-RP-RPLC approach. Applying this 2D-LC method to rat brain samples, we identified 1031 proteins and 4397 unique peptides. In addition, this new two-dimensional method improved the identification of basic peptides. Therefore, we propose that this novel 2D-RP/WCX-RPLC system can be used as an alternative approach for the two-dimensional separation of peptides.
    Journal of Chromatography A 06/2011; 1228:242-9. · 4.61 Impact Factor
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    ABSTRACT: The interaction of two Chinese medicinal ingredients and human serum albumin (HSA) has been investigated by high performance affinity chromatography (HPAC). HSA bounded silica-based stationary phase was prepared based on the "click chemistry" strategy, and packed in a column (named as HSA column). The drug-HSA binding ratio was calculated from the difference of the drug's retention times on the HSA column and silica column (blank column). The warfarin-HSA binding ratio determined by this method was similar to the reference reported value by ultrafiltration method. The results indicated that the new HSA column and the HPAC method can be used for the detection of binding ratio of drug and HSA. The binding ratios of puerarin and goitrin determined by the HPAC method were 10.26% and 10.20%, respectively. And the binding ratio of puerarin determined by ultrafiltration was 14.25%. All these results showed that HPAC is a useful method to investigate the interaction between drugs and protein.
    Se pu = Chinese journal of chromatography / Zhongguo hua xue hui 04/2011; 29(4):358-61.
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    ABSTRACT: In this study, we investigated a novel application of matrix solid-phase dispersion (MSPD) methodology for the extraction of endogenous peptides from porcine hypothalamus tissue samples. Several experimental factors of the MSPD procedure were examined. Finally, silica-based octadecyl was chosen as dispersing material and blended with 0.25 g porcine hypothalamus at a ratio of 5, and 10 mL of 60% acetonitrile with 0.2% formic acid in water was chosen as the extraction and elution solvent. This MSPD extraction method was compared to the classic acid extraction method. More peaks were observed in the MSPD extracts (74±5) by MALDI-TOF MS than in acid extracts (34±5). Moreover, 14 potential endogenous peptides were identified in the MSPD extracts after nanoLC-MS/MS analysis, while only 2 endogenous peptides in the acid extracts. These results indicated that MSPD could be employed as a simple and efficient method for the extraction of endogenous peptides from tissues.
    Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 02/2011; 879(9-10):657-61. · 2.78 Impact Factor
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    ABSTRACT: Lysophosphatidylcholines (lysoPCs) are a class of compounds that have a constant polar head, and fatty acyls of different chain lengths, position, degrees of saturation, and double bond location in human plasma. LysoPCs levels can be a clinical diagnostic indicator that reveals pathophysiological changes. In this work, a method was developed to discriminate between different types of lysoPCs using reversed phase ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry, using mass spectrometry MSE. Isomeric lysoPCs were distinguished based on retention time and the peak intensity ratio of product ions, and 14 pairs of lysoPCs regioisomers were identified in human plasma. The plasma samples of 12 lung cancer patients and 12 healthy persons were collected and analyzed by principal component analysis to generate metabolic profiles of the identified lysoPCs. Both electrospray ionization ESI+ and ESI− results showed that all lung cancer patients had the same five lysoPC metabolic abnormalities, specifically in sn-1 lyso16:0, sn-2 lysoPC 16:0, sn-1 lysoPC 18:0, sn-1 lysoPC 18:1 and sn-1 lysoPC 18:2. Thus, the function of isomers with different fatty acyl positions may be related to lung cancer, and this may help elucidate the mechanism of the disease. KeywordsLysophosphatidylcholine-Isomers-Discrimination-Metabonomics-Lung cancer
    Metabolomics 01/2010; 6(4):478-488. · 4.43 Impact Factor
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    ABSTRACT: Highly polar metabolites are abundant in human plasma. Analysis of these compounds by standard reverse-phase chromatography is difficult. Highly polar metabolites were extracted by a two-step method. They were analyzed by ultra-performance hydrophilic interaction chromatography (HILIC) coupled to quadrupole-time of flight mass spectrometer detection technology. The middle and low polar fraction were also analyzed using a standard C18 column. Data were extracted by Markerlynx, and analyzed by multivariate statistical methods to discriminate human plasma samples by sex and age. The results not only showed good classification of samples by sex and age, but also revealed new potential biomarkers not revealed by standard RPLC/MS analysis. This study showed that HILIC is an effective technique to analyze highly polar metabolites for metabonomic studies.
    Analytica chimica acta 10/2009; 650(1):10-5. · 4.31 Impact Factor
  • Journal of Biotechnology - J BIOTECHNOL. 01/2008; 136.

Publication Stats

50 Citations
22.18 Total Impact Points

Institutions

  • 2011–2013
    • Chinese Academy of Sciences
      • • Dalian Institute of Chemical Physics
      • • Graduate School
      Peping, Beijing, China
    • Dalian Medical University
      Lü-ta-shih, Liaoning, China
  • 2009–2011
    • Northeast Institute of Geography and Agroecology
      • • Laboratory of Analytical Chemistry for Life Science
      • • Graduate School
      Beijing, Beijing Shi, China