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Major advances have been made to improve the sensitivity of mass analyzers, spectral quality, and speed of data processing enabling more comprehensive proteome discovery and quantitation. While focus has recently begun shifting toward robust proteomics sample preparation efforts, a high-throughput proteomics sample preparation is still lacking. We report the development of a highly automated universal 384-well plate sample preparation platform with high reproducibility and adaptability for extraction of proteins from cells within a culture plate. Digestion efficiency was excellent in comparison to a commercial digest peptide standard with minimal sample loss while improving sample preparation throughput by 20- to 40-fold (the entire process from plated cells to clean peptides is complete in ~300 min). Analysis of six human cell types, including two primary cell samples, identified and quantified ~4000 proteins for each sample in a single high-performance liquid chromatography (HPLC)–tandem mass spectrometry injection with only 100 – 10,000 cells, thus demonstrating universality of the platform. The selected protein was further quantified using a developed HPLC-multiple reaction monitoring method for HeLa digests with a heavy labeled internal standard peptide spiked in. Excellent linearity was achieved across different cell numbers indicating a potential for target protein quantitation in clinical research.

Creatine transporter deficiency (CTD) is caused by a defect in the X-linked creatine transporter SLC6A8 gene leading to severe neurologic and physiologic conditions. Cyclocreatine and phosphocyclocreatine supplementation is seen as a potential treatment, but the presence of these compounds within commercially available dietary supplements presents the risk of self-medication. High-performance liquid chromatography-mass spectrometry (HPLC-MS) is an excellent technique to assess composition of complex amino acid mixtures. Herein, we have developed a facile HPLC-MS method using a cyano column in hydrophilic interaction liquid chromatography (HILIC) mode with isocratic elution over 4 min to identify the main components of two commercially available dietary supplements. The relative standard deviation (RSD) for retention time and extracted ion integrated area are

Chemical-peptide conjugation is the molecular initiating event in skin sensitization. The OECD test guideline uses a high-performance liquid chromatography/ultraviolet (HPLC/UV) detection method to quantify chemical-peptide conjugation in a direct peptide reactivity assay (DPRA), which measures the depletion of two synthetic peptides containing lysine or cysteine residues. To improve assay throughput, sensitivity and accuracy, an automated 384-well plate-based RapidFire solid-phase extraction (SPE) system coupled with tandem mass spectrometry (MS/MS) DPRA was developed and validated in the presence of a newly designed internal standard. Compared to the HPLC/UV-based DPRA, the automated SPE-MS/MS-based DPRA improved throughput from 16 min to 10 s per sample, and substrate peptides usage was reduced from 100 mM to 5 μM. When implementing the SPE-MS/MS-based DPRA into a high-throughput platform, we found 10 compounds that depleted lysine peptide and 24 compounds that depleted cysteine peptide (including 7 unreported chemicals from 55 compounds we tested) in a concentration-response manner. The adduct formation between cysteine and cinnamic aldehyde and ethylene glycol dimethacrylate were further analyzed using high-performance liquid chromatography time-of-flight mass spectrometry (HPLC-TOF-MS) to confirm the conjugation. Overall, the automated SPE-MS/MS-based platform is an efficient, economic, and accurate way to detect skin sensitizers.

Proteins are widely used as drug targets, enzyme substrates, and biomarkers for numerous diseases. The emerging demand for proteins quantitation has been increasing in multiple fields. Currently, there is still a big gap for high-throughput protein quantitation at intact protein level using label-free method. Here we choose ribonuclease B (RNB) as a model, which is the substrate for human endo-β-N-acetylglucosaminidase (hENGase), a promising drug target for the treatment of N-Glycanase deficiency. Intact proteinlevel multiple reaction monitoring (MRM) methods were initally developed and optimized to quantify RNB and deglycosylated RNB (RNB-deg), with the S/N ratio improved by nearly 20-fold compared to the traditional full MS scan methods. To further increase the throughput making it possible for hENGase inhibitors screen, the protein MRM methods were introduced to the RapidFire-MS/MS system, achieving at least 12-fold throughput improvement. This assay was further optimized into 384-well plate format for compound screening with S/B ratio >37-fold and Z’ factor >0.7 that is suitable for high-throughput screening of compound collections with a speed of 2 h per 384-well plate and an ability to screen over 3000 compounds per day at a single concentration dose. This 384-well plate based automated SPE-MS/MS assay is efficient and robust for compound screening and the assay format has a wide applicability to protein targets for other disease models.

Single chain variable fragment (scFv) displaying the M13 phage library was covalently immobilized on magnetic microspheres and used as a protein equalizer for the treatment of human serum. First, scFv displaying M13 phage library functionalized magnetic microspheres (scFv@M13@MM) was incubated with a human serum sample. Second, captured proteins on scFv@M13@MM were eluted with 2 M NaCl, 50 mM glycine-hydrochloric acid (Gly-HCl), and 20% (v/v) acetonitrile with 0.5% (v/v) trifluoroacetic acid in sequence. Finally, the tightly bonded proteins were released by the treatment with thrombin. The eluates were first analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with silver staining. Results indicated that the difference of protein concentration was reduced obviously in NaCl and Gly-HCl fractions compared with untreated human serum sample. The eluates were also digested with trypsin, followed by online 2D-strong cation exchange (SCX)-RPLC-ESI-MS/MS analysis. Results demonstrated that the number of proteins identified from an scFv@M13@MM treated human serum sample was improved 100% compared with that from the untreated sample. In addition, the spectral count of 10 high abundance proteins (serum albumin, serotransferrin, α-2-macroglobulin, α-1-antitrypsin, apolipoprotein B-100, Ig γ-2 chain C region, haptoglobin, hemopexin, α-1-acid glycoprotein 1, and α-2-HS-glycoprotein) decreased evidently after scFv@M13@MM treatment. All these results demonstrate that scFv@M13@MM could efficiently remove high-abundance proteins, reduce the protein concentration difference of human serum, and result in more protein identification.

An integrated multidimensional nano-flow liquid chromatography platform with the combination of protein and peptide separation via online digestion by an immobilized enzymatic reactor was established, and successfully applied for proteome analysis. By this platform, proteins were first separated by a weak anion and weak cation mixed-bed microcolumn under a series of salt steps, online digested by a trypsin immobilized enzymatic reactor, digests trapped and desalted by a C18 precolumn, separated by nano-reversed phase liquid chromatography, and finally identified by electrospray ionization-MS/MS. To evaluate the performance of such a platform, Escherichia coli whole cell lysate proteins were analyzed. Compared with the results obtained by shotgun approach, the identified protein number was increased by 6%, with the consumed time decreased from 38 to 14 h. We also compared with integrate platform based on micro-HPLC, and the required sample amount was decreased to 8 mu g. These results demonstrated that such an integrated approach would be an attractive alternative to commonly applied approaches for proteome research.

A novel kind of hydrophilic monolith based immobilized enzyme reactors (IMERs) was prepared both in UV-transparent capillaries and on glass microchips by the photopolymerization of N-acryloxysuccinimide and poly(ethylene glycol)diacrylate, followed by trypsin immobilization. The performance of capillary IMERs for protein digestion was evaluated by the digestion of myoglobin with the residential time from 12 s to 71 s. With μRPLC–ESI-MS/MS analysis, the obtained sequence coverages were all over 80%, comparable to that obtained by in-solution digestion for 12 h. The nonspecific absorption of BSA on monolithic support was evaluated, and no obvious protein residue was observed by a fluorescence assay. Moreover, no carry-over of the digests on the capillary IMER was found after the digestion of myoglobin (24 μg) and BSA (9 μg), which further demonstrated the good hydrophilicity of such matrix. In addition, an integrated microchip-based system involving on-line protein digestion by microchip-based IMER, peptides separation by nanoRPLC and identification by ESI-MS/MS was established, by which a mixture of standard proteins and one RPLC fraction of Escherichia coli extract were successfully identified, indicating that the hydrophilic monolith based IMER might provide a promising tool for high-throughput proteomic analysis.

Two dimensional high performance liquid chromatography-electrospray ionization tandem mass spectrometry (2D-HPLC-ESI-MS/MS) is one of the most powerful techniques for high resolution, efficiency, and throughput separation and identification of proteomes. For a bottom-up strategy-based proteome analysis, usually multistep salt elution was needed in the first dimension separation by SCX, to simplify the peptides for the further second dimensional separation by RPLC. Here, by using a 30 cm-long serially coupled long column (SCLC) in the second dimension, we reduced the salt steps of SCX from 13 to 5 to shorten the total analysis time. Compared to the commonly applied 2D-HPLC with over 10-step salt elution in SCX and microRPLC with a short column (SC), named as SC-2D, the peak capacity of 2D-HPLC with a SCLC column, named as SCLC-2D, was increased 3.3-folds while the analysis time was increased by only 1.17-folds. Therefore, the time-based protein identification efficiency was similar to 55 protein groups/h, nearly 2-fold of that for SC-2D (similar to 28 protein groups/h). With the further combination of assisted solubilization by ionic liquids and SCLC-2D, 608 integral membrane proteins (IMPs) (27.66% of the total 2198 proteins, FDR < 1%) were identified from rat brain, more than those obtaind by the traditional urea method (252 unique IMPs, occupying 17.03% of total 1480 proteins). All of these results demonstrate the promise of the developed technique for large-scale proteome analysis.

To improve the efficiency of proteome analysis, a strategy with the combination of protein pre-fractionation by preparative microscale solution isoelectric focusing, peptide separation by μRPLC with serially coupled long microcolumn and protein identification by ESI-MS/MS was proposed. By preparative microscale solution isoelectric focusing technique, proteins extracted from whole cell lysates of Escherichia coli were fractionated into five chambers divided by isoelectric membranes, respectively with pH range from 3.0 to 4.6, 4.6 to 5.4, 5.4 to 6.2, 6.2 to 7.0 and 7.0 to 10.0. Compared to the traditional on-gel IFF, the protein recovery could be obviously improved to over 95%. Subsequently, the enriched and fractionated proteins in each chamber were digested, and further separated by a 30-cm long serially coupled RP microcolumn. Through the detection by ESI-MS/MS, about 200 proteins were identified in each fraction, and in total 835 proteins were identified even with one-dimensional μRPLC-MS/MS system. All these results demonstrate that by such a combination strategy, highly efficient proteome analysis could be achieved, not only due to the in-solution protein enrichment and pre-fractionation with improved protein recovery but also owing to the increased separation capacity of serially coupled long μRPLC columns.

The solubility and digestion efficiency are two crucial factors that might affect the identification of integral membrane proteins (IMPs). In this work, 1% (v/v) ionic liquid (IL), 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIM BF(4)), added in NH(4)HCO(3) buffer (pH 8.3), was applied as a sample preparation buffer for IMPs analysis. Compared to the commonly used sodium dodecyl sulfate and methanol methods, the number of identified IMPs from rat brain by microcolumn reversed phase liquid chromatography (μRPLC)-electrospray ionization tandem mass spectrometry (ESI-MS/MS) was improved by over three times, which might be due to the fact that BMIM BF(4) offered high solubilizing ability for IMPs and good compatibility for tryptic digestion. Furthermore, compared to Rapigest and urea methods, with BMIM BF(4) method, the number of identified IMPs from rat brain could be improved 25% and 80%, respectively, which might be contributed to the good solubilizing ability and high thermal stability of such IL. With the sample treated by BMIM BF(4) method, by 2D-nanoSCX-RPLC-ESI-MS/MS, 1,450 non-redundant proteins and 7,978 unique peptides were identified from rat brain, and 418 proteins contained at least one predicted transmembrane domain, with false discovery rates of less than 1% for peptide identification, and at least two identified unique peptides per protein. All these results demonstrate that the BMIM BF(4) method is of high potential for the large-scale identification of IMPs.

Screening of tumor markers by proteomic technology is the research focus and key of early diagnosis of stomach cancer study. Aiming at the complexity of the extracted proteins from biological tissue, reversed-phase high performance liquid chromatography (RP-HPLC) was employed as one of the most efficient chromatographic methods. Based on the difference of hydrophobicity, RP-HPLC separation was performed to reduce the complexity of stomach cancer tissue and normal tissue samples, separately. By comparing the chromatograms, different components were collected. The fractions with the retention times from 45 min to 47 min were digested and identified by liquid chromatography-multistage mass spectrometry (LC-MS/MS). Nine common proteins were found in both tumor tissue and normal tissue. Six specific proteins were screened in normal tissue and seventeen specific proteins were found in tumor tissue under the same conditions. Two proteins with higher abundance in tumor tissue were selected for further investigation. These proteins provide more information for future drug target and drug pathway research by the analysis of biological information.

An integrated platform with the combination of protein and peptide separation was established via online protein digestion, by which proteins were first separated by a microcolumn packed with mixed weak anion and weak cation exchange (WAX/WCX) particles under a series of salt steps, online digested by a trypsin immobilized microenzymatic reactor (IMER), trapped and desalted by two parallel C8 precolumns, separated by microreversed-phase liquid chromatography (muRPLC) under a linear gradient of organic modifier concentration, and finally identified by electrospray ionization-MS/MS (ESI-MS/MS). To evaluate the performance of such a platform, a mixture of myoglobin, cytochrome c, bovine serum albumin (BSA), and alpha-casein, with mass ranging from 25 ng to 2 microg, was analyzed. Compared to the methods by off-line protein fractionation and shotgun based strategy, the analysis time, including sample preparation, digestion, desalting, separation, and detection, was shortened from ca. 30 to 5 h, and cytochrome c with abundance of 25 ng could be identified with improved sequence coverage. Furthermore, such an integrated platform was successfully applied into the analysis of proteins extracted from human lung cancer cells. Compared with the results obtained by the shotgun approach, the identified protein number was increased by 30%. All these results demonstrated that such an integrated approach would be an attractive alternative to commonly applied approaches for proteome research.

In this study, microchip free flow planar RP electrochromatography (microFF-PRPEC) was developed by in situ polymerization of monolithic materials in microchamber, and successfully applied for the separation of dyes and proteins. Poly(butyle methyacrylate-co-ethylene dimethacrylate) was prepared by UV-initiated polymerization in a glass microchamber (42 mm long, 23 mm wide, and 28 microm deep). A mixture of 1-propanol, 1,4-butanediol, and water was chosen as porogens, and 1.2% (wt%) 2-acrylamide-2-methyl-propanesulfonic acid (AMPS) was added into the polymerization solution to generate EOF. With 30% v/v ACN-15 mM Tris-HCl as the mobile phase, rhodamine B and methyl green were separated from each other with 400 V transverse voltage applied, and resolution as high as 4.6 was obtained, much higher than that obtained by microFFE under optimal conditions. Furthermore, microFF-PRPEC was also successfully applied into the separation of lysozyme and ribonuclease B, and resolution as high as 9.4 was obtained. All these results demonstrate that microFF-RPPEC might have great potential in the microscale continuous preparation of samples with improved resolution compared to microFFE.

Microcolumn RPLC (microRPLC) is one of the optimum separation modes for shotgun proteomic analysis. To identify as many proteins as possible by MS/MS, the improvement on separation efficiency and peak capacity of muRPLC is indispensable. Although the increase in column length is one of the effective solutions, the preparation of a long microcolumn is rather difficult due to the high backpressure generated during the packing procedure. In our recent work, through connecting microcolumns of 5, 10, and 15 cm length via unions with minimal dead volume, long microcolumns with length up to 30 cm were obtained, with which 318 proteins were identified from proteins extracted from Escherichia coli by microRPLC-ESI MS/MS, and similar distributions of M(w) and pI were found with single and various coupled microcolumns. Furthermore, by using MS/MS with improved sensitivity, with such a serially coupled 30 cm long microcolumn, 1692 proteins were identified within 7 h from rat brain tissue, with false positive rate (FPR)

The adverse effect of salts, especially inorganic salts, on electrospray ionization mass spectrometry (ESI-MS) is one of the most serious obstacles that might limit its application. Among the numerous desalting approaches, the microdialysis technique is favorable for large molecules, such as proteins. In this work, employing a hollow fiber membrane of cellulose acetate (MWCO 3000 Da), a simple, facile and efficient microdialysis interface with the dead volume of less than 1 mu L was constructed for the on-line desalting and identification of proteins dissolved in high salt concentration buffer by nano-ESI-MS. Furthermore, with counterflow added, the desalting procedure was accelerated, and could be finished within 1 min. This system was successfully applied to the analysis of myoglobin dissolved in either high concentration ammonium acetate or sodium chloride buffer. The experimental results showed that, by using such a microdialysis interface, the salt concentration, even as high as 1 M, could be decreased by at least 2 orders of magnitude, while sample loss was less than 10%, demonstrating the potential of such an interface in broadening the application of nano-ESI-MS in the analysis of large molecules. Copyright (c) 2008 John Wiley & Sons, Ltd.

A novel kind of immobilized trypsin reactor based on organic-inorganic hybrid silica monoliths has been developed. With the presence of cetyltrimethyl ammonium bromide (CTAB) in the polymerization mixture, the hybrid silica monolithic support was prepared in a 100 microm i.d. capillary by the sol-gel method with tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) as precursors. Subsequently, the monolith was activated by glutaraldehyde, and trypsin was covalently immobilized. By monitoring the reaction of a decapeptide, C-myc (EQKLISEEDL), the enzymatic activity of the immobilized trypsin was calculated, and the results showed that the digestion speed was about 6600 times faster than that performed in free solution. The performance of such a microreactor was further demonstrated by digesting myoglobin, with the digested products analyzed by microflow reversed-phase liquid chromatography coupled with tandem mass spectrometry (microRPLC-MS/MS). With a stringent threshold for the unambiguous identification of the digests, the yielding sequence coverage for on-column digestion was 92%, the same as that obtained by in-solution digestion, whereas the residence time of myoglobin in the former case was only 30 s, about 1/1440 of that performed in the latter case (12 h). Moreover, such an immobilized trypsin reactor was also successfully applied to the digestion of a mixture of model proteins and proteins extracted from E. coli.

A two-dimensional capillary electrophoresis platform, combining isoelectric focusing (ief) and capillary zone electrophoresis (cze), was established on a microchip with the channel width and depth as 100 mu m and 40 mu m, respectively. with polyacrylamide as permanent coating, eof in the microchannel, which could impair the separation, was decreased to 3.4 x 10(-9) m(2) . v(-1) . s(-1), about 1/10 of that obtained in the uncoated set-up. during the separation, peptides were first focused by ief in the first dimensional channel, and then directly driven into the perpendicular channel by controlling the applied voltages, and separated by cze. effects of various experimental parameters, including the electric field strength, channel length, and injection frequency from the first to the second dimensional separation channel, were studied. under optimized condition, the digests of bsa and proteins extracted from e. coli were separated, and a peak capacity of 540 was obtained, which was far greater than that obtained by each single dimensional separation. all these results showed the promise of multidimensional separation on a microchip for the high-throughput and high-resolution analysis of complex samples.

Metabolomics and peptidomics are systems biology approaches in which broad populations of molecular species produced in a cell or tissue sample are identified and quantified. These two molecular populations, metabolites and peptides, can be extracted from tissues in a similar fashion, and we therefore have here developed an integrated platform for their extraction and characterization. This was accomplished by liquid-liquid extraction of peptides and metabolites from tissue samples and online strong cation exchange (SCX) separation to allow characterization of each population individually. The platform was validated both by a mixed set of purified standards and by an analysis of splenic tissue from SIV-infected macaques, showing both good reproducibility in chromatography, with relative standard deviation (RSD) of hold time less than 0.4%, and clear separation of charge state, with ∼ 95% of molecular features in SCX separated runs at charge states of +1 or +2. Finally, we used this platform to analyze the physiological response to infection in the spleen, showing that the spleen contains an abundance of hemoglobin-derived peptides, which do not appear to change in response to infection, and that there appears to be a large and variable metabolic response to infection. We therefore present a method for peptidomic and metabolomic profiling which is simple, robust, and easy to implement.

Hierarchical imprinting was developed to prepare the protein imprinted materials, as the artificial antibody, for the selective depletion of HSA from the human serum proteome. Porcine serum albumin (PSA) was employed as the dummy template for the fabrication of the recognition sites. To demonstrate the advantages of the hierarchical imprinting, molecularly imprinted polymers prepared by hierarchical imprinting technique (h-MIPs) were compared with those obtained by bulk imprinting (b-MIPs), in terms of the binding capacity, adsorption kinetics, selectivity and synthesis reproducibility. The binding capacity of h-MIPs could reach 12 mg g(-1). And saturation binding could be reached in less than 20 min for the h-MIPs. In the protein mixture, h-MIPs exhibit excellent selectivity for PSA, with imprinting factors as about 3.6, much higher than those for non-template proteins. For the proteomic application, the identified protein group number in serum treated by h-MIPs was increased to 422, which is 21% higher than that obtained from the original serum, meanwhile the identified protein group number for the Albumin Removal kit was only 376. The results demonstrate that protein imprinted polymers prepared by hierarchical imprinting technique, might become the artificial antibodies for the selective depletion of high abundance proteins in proteome study.

The large-scale N-glycosylation analysis is critical for biomedical research, since a variety of diseases are found to be associated with glycoproteins. By a combination of glycoprotein analysis in insoluble protein fraction solubilized with 1% v/v 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM BF(4)) and those in soluble fraction, a total number of 462 non-redundant N-glycoprotein groups, including 316 transmembrane glycoproteins, were successfully identified. Correspondingly, 849 unique N-glycosites were confidently recognized. The data set could provide a support for the further in-depth research of brain N-glycosylation, such as for the discovery of candidate drug targets and biomarkers.

In this study, a facile system for membrane proteome profiling was established, in which membrane proteins were solubilized by formic acid, online digested by a pepsin-based immobilized enzyme reactor (pepsin-IMER), and analyzed by strong cation exchange and microflow reversed-phase liquid chromatography with electrospray ionization tandem mass spectrometry (SCX-μRPLC-ESI-MS/MS). Under optimized conditions, such a system showed excellent compatibility between all crucial steps and was successfully applied for analyzing integral membrane proteins extracted from rat liver microsomes. Out of the 235 unique proteins positively identified, 39% (91/235) were annotated as membrane proteins with one or more transmembrane domains (TMDs). It is anticipated that the efficient sample treatment and the relevant online analytical system might provide a promising tool for automated and comprehensive profiling of membrane proteomes.

Deer antlers mature rapidly in 60 days, and subsequently shed in 5 days with rapid ossification. During this procedure, the function of deer antlers changes significantly. Therefore, the profiling of antler proteome is helpful to discover important growing and shedding regulation proteins, which might be of great significance for studying development and regeneration. In this study, a parallel protein extraction strategy was developed to extract proteins from antlers of red deer with five different lysis solutions, followed by shotgun proteomic analysis by microflow reversed-phase liquid chromatography/electrospray ionization/tandem mass spectrometry (μRPLC-ESI-MS/MS) with a 30 cm-long serially coupled microcolumn. Our experimental results showed that the identified proteins extracted by five kinds of lysis solution were complementary to each other. In total, 416 unique proteins were identified, with relative molecular masses from 2000 to 600,000, and isoelectric points from 3.84 to 11.57. All these results demonstrate that the combination of parallel protein extraction strategy and μRPLC-ESI-MS/MS analysis with serially coupled long microcolumns might be of great significance for comprehensive proteomic research of deer antler.

A novel kind of immobilized metal affinity chromatography (IMAC) column based on organic-inorganic hybrid silica monolith has been developed. The monolithic support was prepared in a 250 microm i.d. capillary by the sol-gel method with tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) as precursors. Subsequently, amine groups were functionalized by glutaraldehyde, and then activated with (aminomethyl) phosphonic acid, followed by Ti(4+) chelation. By such a hybrid silica monolithic Ti(4+)-IMAC column, 15 phosphopeptides were effectively isolated from the digest mixture of alpha-casein and BSA with the molar ratio as low as 1:200, illustrating its superior selectivity. With a synthetic phosphorylated peptide, YKVPQLEIVPNSpAEER, as the sample, the loading capacity and recovery of the Ti(4+)-IMAC monolithic column were measured to be 1.4 micromol/mL and 69%, respectively. Such an IMAC monolithic column was further applied to enrich phosphopeptides from rat liver mitochondria. In total, 224 unique phosphopeptides, corresponding to 148 phosphoprotein groups, were identified by duplicate nanoRPLC-LTQ MS/MS/MS runs with a false-positive rate of less than 1% at the peptide level. These results demonstrate that the hybrid silica monolith based Ti(4+)-IMAC column might provide a promising tool for large-scale phosphopeptide enrichment, facilitating the in-depth understanding of the biological functions of phosphoproteomes.

High-performance liquid chromatography–electrospray ionization tandem mass spectrometry (HPLC–ESI-MS–MS) is regarded as one of the most powerful techniques for separation and identification of proteins. Recently, much effort has been made to improve the separation capacity, detection sensitivity, and analysis throughput of micro- and nano-HPLC, by increasing column length, reducing column internal diameter, and using integrated techniques. Development of HPLC columns has also been rapid, as a result of the use of submicrometer packing materials and monolithic columns. All these innovations result in clearly improved performance of micro- and nano-HPLC for proteome research.

A comprehensive two-dimensional liquid chromatographic (2D-LC) separation system based on the combination of a CN column and a Merck Chromolith Flash reversed-phase column was developed for the separation of components in Adinandra nitida, one type of traditional Chinese medicine (TCM). The two dimensions were connected by a ten-port, dual-position valve controlled automatically by software written in-house. The effluents were detected by both ultraviolet and atmospheric pressure chemical ionization source ion trap tandem mass spectrometry (MS). The calculated peak capacity of the 2D-LC-MS/MS system was above 1240. More than 57 components were resolved in the methanol extract from Adinandra nitida leaves, and five of these were identified based on their relative retention times, molecular weights and MS/MS spectra.