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Mass spectrometry-based proteomics experiments can be subject to a large variability, which forms an obstacle to obtaining deep and accurate protein identification. Here, to obtain an optimal sample preparation workflow for in-depth proteome identification in human tissues, we systematically compared typical procedures in the four key steps during sample preparation, including two lysis buffers (5% SDS and 7M urea/2M thiourea), acetone precipitation, two proteolytic enzyme methods (in-solution digestion and FASP), and two pre-fractionation methods (SDS-PAGE and hi-pH RPLC). Compared with other methods, the procedure, including urea/thiourea as the lysis buffer, in-solution digestion, followed by hi-pH RPLC, yields an increase in proteome coverage (+15%), matched peptides (+42.4%), and significantly high protein concentrations. We also used combinations of these sample preparation methods to demonstrate a high identification rate in the range of low molecular weight (LMW), and the performance of sample preparation workflows varied between different groups of proteins. Importantly, 3 proteins defined as missing proteins (MPs) following the Human Proteome Project (HPP) guidelines were found in our data set. Overall, our findings provide an optimal sample preparation workflow for highly efficient and unbiased global proteomic analysis in human tissues.

Tobacco is a traditional Chinese medicine containing a variety of biologically active substances. In addition to being used to make cigarettes, tobacco is also a vastly underdeveloped medicinal resource. In order to identify and clarify the biological activities and medicinal value of tobacco leaves, the metabolomes of tobacco leaves were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) based on multiple reaction monitoring (MRM). In total, 1169 metabolites were identified and quantified. The results showed that the metabolic profiles of the tobacco cultivars K326 and Yun87 are similar to each other but different from that of Hongda. Moreover, the curing process affects the metabolic profiles of tobacco leaves. Flavonoids are the largest class of metabolites in tobacco leaves. Flavonoids have multiple biological functions; for example, they can promote or inhibit inflammation. We found that quercetin provides anti-inflammatory activity by inhibiting the il-1β mRNA expression, while glycitin and neohesperidin can promote il-1β and il-6 production. Our results provide in-depth insights into the medical uses and biological mechanisms of tobacco leaves.

Serum/plasma holds promise as an important source of disease-related proteins and even biomarkers in clinical practice. However, the discovery of biomarker candidates in serum/plasma remains challenging. In this study, we constructed an MS strategy that enables the fast and precise quantification of serum biomarkers through coupling a high-throughput scheduled MRM strategy with a stable isotope-labelled (SIL) peptide panel from more than 500 plasma proteins as internal standards. With this strategy, we discovered relevant serum proteins of atherosclerosis (AS), lung cancer (LC) and breast cancer (BC), which can simultaneously recognize these diseases. The results indicate that the powerful strategy we constructed has the potential for serum biomarker screening and disease detection.

Bloodstream infections rank among the most serious causes of morbidity and mortality in hospitalized patients, partly due to the long period (up to one week) required for clinical diagnosis. In this work, we have developed a sensitive method to quickly and accurately identify bacteria in human blood samples by combining optimized matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MS) and efficient immunoaffinity enrichment/separation. A library of bacteria reference mass spectra at different cell numbers was firstly built. Due to a reduced sample spot size, the reference spectra could be obtained from as few as 10 to 10(2) intact bacterial cells. Bacteria in human blood samples were then extracted using antibodies-modified magnetic beads for MS fingerprinting. By comparing the sample spectra with the reference spectra based on a cosine correlation, bacteria with concentrations as low as 500 cells per mL in blood serum and 8000 cells per mL in whole blood were identified. The proposed method was further applied to positive clinical blood cultures (BCs) provided by a local hospital, where Escherichia coli and Staphylococcus aureus were identified. Because of the method's high sensitivity, the BC time required for diagnosis can be greatly reduced. As a proof of concept, whole blood spiked with a low initial concentration (10(2) or 10(3) cells per mL) of bacteria was cultured in commercial BC bottles and analysed by the developed method after different BC times. Bacteria were successfully identified after 4 hours of BC. Therefore, an entire diagnostic process could be accurately accomplished within half a day using the newly developed method, which could facilitate the timely determination of appropriate anti-bacterial therapy and decrease the risk of mortality from bloodstream infections.

The dispersive effect of polyacrylate amine (NH4PAA) upon suspensions of silicon nitride (Si3N4) is considered. Slurry introduction for axial inductively coupled plasma optical emission spectrometry determination of Al, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni and Ti in powdered Si3N4 has also been investigated. Characterization by zeta potential measurement and slurry stability measurements shows that NH4PAA is a good dispersant for the preparation of Si3N4 suspensions. The optimal concentration of NH4PAA was 0.8 wt% for μm-sized Si3N4 and 1.2 wt% for nm-sized Si3N4. The analytical results obtained using nm- and μm-sized Si3N4 by slurry introduction were in good accordance with results obtained by the high-pressure acid deposition method, thus verifying that calibration curves could be established using aqueous standards. By introducing a low amount of contamination in the sample preparation, an accurate result is obtained for the detection of contamination-risk elements such as K and Na, which cannot be accurately determined by the high-pressure acid deposition method. The limits of detection, which are in the range of 8–250 ng g−1, were shown to be superior to those of the conventional nebulization technique with ICP-OES or ICP-MS.

SDS-PAGE and high-pH RPLC are commonly used fractionation strategies in proteomics research. A comparative investigation of these two strategies would be meaningful to thoroughly understand their respective features. Here, we systematically compared the two methods by trying 4 SDS-PAGE/RPLC and 3 high-/low-pH RPLC different workflows for a higher sensitivity in protein identification. Totally 9793 proteins were identified in HepG2 cells, with 8581 proteins identified by high-/low-pH RPLC workflows and 7933 by SDS-PAGE/RPLC workflows. The results demonstrate that using high-pH RPLC in the first dimensional separation would favour a high-throughput proteome analysis but choosing SDS-PAGE could yield much better peptide coverage. We found that the SDS-PAGE fractionation method benefits the neutral pI peptides. We also analyzed unexpected modifications caused by the two strategies. Our results suggest that more pre-fractionation benefits protein identifications in both strategies and pooling of gel pieces according to their grey values increased the identification efficiency in SDS-PAGE/RPLC workflows.

Trypsin has traditionally been used for enzymatic digestion during sample preparation in shotgun proteomics. The stringent specificity of trypsin is essential for accurate protein identification and quantification. But nonspecific trypsin cleavages are often observed in LC-MS/MS-based shotgun proteomics. To explore the extent of nonspecific trypsin cleavages, a series of biological systems including a standard protein mixture, Saccharomyces cerevisiae, human serum, human cancer cell lines and mouse brain were examined. We found that nonspecific trypsin cleavages commonly occurred in various trypsin digested samples with high frequency. To control these nonspecific trypsin cleavages, we optimized fundamental parameters during sample preparation with mouse brain homogenates. These parameters included denaturing agents and protein storage time, trypsin type, enzyme-to-substrate ratio, as well as protein concentration during digestion. The optimized experimental conditions significantly decreased the ratio of partially tryptic peptides in total identifications from 28.4% to 2.8%. Furthermore, the optimized digestion protocol was applied to the study of N-glycoproteomics, and the proportions of partially tryptic peptides in enriched mixtures were also sharply reduced. Our work demonstrates the importance of controlling nonspecific trypsin cleavages in both shotgun proteomics and glycoproteomics and provides a better understanding and standardization for routine proteomics sample treatment.

Protein analysis is always one of the key fields researchers focus on. Recent years has witnessed the rapid development of novel nanomaterials and microfluidic droplets as ideal reactors for protein analysis. This article reviews the recent advances regarding the development of nanomaterial-based nanoreactors and microfluidic droplet reactors and their applications in protein analysis, especially in proteomics. The categories, features and applications of various recently developed micro/nano-reactors have been summarized and future directions and challenges in this field have also been discussed.

PNGase F-catalyzed glycosylation site (18)O-labeling is a widely used method for glycoprotein quantitation owing to its efficiency and simplicity. However, PNGase F-catalyzed glycan (18)O-labeling, which offers advantages for glycomics, has not yet been developed. In this study, PNGase F-mediated incorporation of (18)O into glycans during the N-glycan release from glycoproteins by PNGase F was finally realized, named as PCGOL (PNGase F-catalyzed glycan (18)O-labeling), which offers a potential strategy for relative glycan quantitation. This new method showed good linearity and high reproducibility within at least 2 orders of magnitude in the dynamic range. Furthermore, PCGOL combined with our previously developed TOSIL method (tandem (18)O stable isotope labeling for N-glycoproteome quantitation) can be used for comprehensive N-glycosylation quantification, achieving simultaneous quantification of glycans, glycopeptides and glycoproteins in a single workflow, which was also used to analyze glycosylation changes in immunoglobulin G (IgG) associated with hepatocellular carcinoma in the present work.

As a key post-translational modification mechanism, protein acetylation plays critical roles in regulating and/or coordinating cell metabolism. Acetylation is a prevalent modification process in enzymes. Protein acetylation modification occurs in sub-stoichiometric amounts; therefore extracting biologically meaningful information from these acetylation sites requires an adaptable, sensitive, specific, and robust method for their quantification. In this work, we combine immunoassays and multiple reaction monitoring-mass spectrometry (MRM-MS) technology to develop an absolute quantification for acetylation modification. With this hybrid method, we quantified the acetylation level of metabolic enzymes, which could demonstrate the regulatory mechanisms of the studied enzymes. The development of this quantitative workflow is a pivotal step for advancing our knowledge and understanding of the regulatory effects of protein acetylation in physiology and pathophysiology.

GREDIL for quantitative N-glycomics largely improves the stability of N-glycan 18O-labeling and greatly decreases the interference of isotopic cluster overlap.

Slurry nebulization in plasmas has advantages of simplicity, high speed, low cost, minimized analyte loss, and low risk of sample contamination, but it has not been very widely adopted. However, the study of advanced ceramic materials has recently renewed enthusiasm for this technique. In this paper, the current state of research on slurry nebulization in plasmas for the analysis of advanced materials is thoroughly surveyed. Sample preparation, sample characterization, and modifications of the instrumentation necessary for slurry nebulization are reviewed, along with calibration procedures and studies on fundamental issues. Finally, the applications of this method to a variety of advanced materials are summarized, and the outlook for this method is discussed.

Taking advantage of reliable metabolic labeling and accurate isobaric MS2 quantification, we developed a global in vivo terminal amino acid labeling (G-IVTAL) strategy by combining metabolic labeling and isotopic dimethyl labeling for quantifying tryptic peptides. With G-IVTAL, the scale of qualitative and quantitative data can be increased twofold compared with in vivo termini amino acid labeling (IVTAL) in which Lys-N and Arg-C are used for digestion. As a result, up to 81.78% of the identified proteins have been confidently quantified in G-IVTAL-labeled HepG2 cells. Dialyzed serum has been used in most SILAC studies to ensure complete labeling. However, dialysis requires the removal of low molecular weight hormones, cytokines, and cellular growth factors, which are essential for the cell growth of certain cell lines. To address the influence of dialyzed serum in HepG2 growth, the G-IVTAL strategy was applied to quantify the expression differences between dialyzed serum- and normal serum-cultured HepG2 cells. Finally, we discovered 111 differentially expressed proteins, which could be used as references to improve the reliability of the SILAC quantification. Among these, by using western blotting, the differential expressions of MTDH, BCAP31, and GPC3 were confirmed as being influenced by dialyzed serum. The experimental results demonstrate that the G-IVTAL strategy is a powerful tool to achieve accurate and reliable protein quantification.

Lectin microarrays are increasingly used as screening tools with a high potential for glycobiology analysis, providing a high-sensitivity profiling of complex glycan features in a short time, without the need for the release of glycan. The application of the technology for the rapid differential glycan profiling of target samples resulted in the discovery of new glycan-related biomarkers for disease detection and particular types of glycobiology studies. Additionally, lectin microarrays might offer many opportunities for further innovation, and their range of applications in the life sciences promises to be greatly expanded. Herein, we describe the advances in the fabrication and detection of lectin microarray technologies and their application, which herald even more exciting breakthroughs in the coming decade.

Correction for ‘Identification of potential serum biomarkers of acute paraquat poisoning in humans using an iTRAQ quantitative proteomic’ by Liming Wei et al., RSC Adv., 2018, 8, 10598–10609.

Parkinson's disease (PD) is a common disease which occurs in aged people with chronic, progressive degenerative character of the central nervous system. Until now there is no effective treatment method in PD patients before they show obvious symptoms for prevention and early diagnosis. In order to find out early disease specific biomarkers, two-dimensional liquid chromatography-tandem mass spectrometry coupled with isobaric tags for relative and absolute quantification (iTRAQ) labeling was employed to quantitatively identify the differentially expressed proteins among the different disease progress types of PD. 26 proteins were differentially expressed in a total of 258 identified proteins by proteomic techniques. The expression level of eight proteins which included sero-transferrin and clusterin increased. The expression level of eighteen proteins which include complement component 4B, apolipoprotein A-I, α-2-antiplasmin and coagulation factor V decreased. Those proteins may be associated with oxidative stress, mitochondrial dysfunction, abnormal protein aggregation and inflammation. In this study, the expression level of apolipoprotein A-I decreased, particularly in the early stage of PD patients. This protein regulated not only the lipid metabolism in the central nervous system, but also influenced the deposition process of proteins which are involved in neural degenerative diseases, such as the pathogenesis of PD.

Microdialysis sampling coupled with liquid chromatography-electrochemical detection (LC-ED) was developed and applied to determine the interaction of thiopurine (TP) with bovine serum albumin (BSA). A nickel hexacyanoferrate (NiHCNFe) modified electrode was fabricated and used as the working electrode in LC-ED for the determination of TP. Cyclic voltammetric experiments demonstrate that this chemically modified electrode (CME) can effectively catalyze the electrooxidation of TP. The mechanism of the catalytic oxidation of TP at the CME involves an 'EC' process. In the LC-ED, the CME also shows good stability and reproducibility for the determination of TP. The limit of detection is 5.0 x 10(-7) mol l(-1) for 6-TP with a signal-to-noise ratio of 3. The utility of microdialysis as a quantitative sampling technique for in vitro studies of drug-protein interactions was studied. The microdialysis experiments were performed in phosphate buffer solution (pH 7.4) containing different molar ratios of the drug and protein at 37 degrees C. The collected microdialysis sample with unbound TP was analyzed at the NiHCNFe CME in the LC-ED. The relative recovery of TP determined in vitro is 18.3% at a perfusion rate of 1.0 microl min(-1) and the RSD is about 2.1%. The association constant and the number of binding sites on a BSA molecule calculated with the Scatchard equation are 3.72 x 10(-3) (1 mol(-1)) and 1.51, respectively. This method provides a fast, sensitive and simple technique for the study of drug-protein interactions.

The possibility of suppressing gas species in direct current glow discharge mass spectrometry (dc-GDMS) with a linear time-of-flight mass analyzer was investigated. With this dc-GD ion source, a ‘clean’ mass spectrum rich in analyte could be obtained when the dc-GD was operated under a discharge current of 15–30 mA and a gas pressure of 300–500 Pa, in contrast to the strong signals of gas species in conventional dc-GDMS, which operates at lower currents and pressures (typically 1–5 mA and 100 Pa). Such an experimental result is believed to be due to increased sputtering at higher pressures and currents, and the different ionization mechanisms of analyte and gas species. For a possible GD design to eliminate the background gas ions, a new discharge configuration was developed by attaching a TM 010 microwave resonator to the GD ion source. The mass spectrum of the cathode sample showed a low gas species background when the microwave-induced plasma (MIP) discharge was ‘off’ under different dc-GD parameters. The mass spectra of analyte and gas species obtained with ‘MIP+dc-GD’ and ‘MIP only’ modes are also compared and discussed. It was found that the analyte signals decrease and the gas species signals increase in the presence of the MIP, and that the analyte signals nearly disappear in the ‘MIP only’ mode. Preliminary results suggest that, for specific discharge conditions and with a suitable design of the GD source, an efficient suppression of gas species in dc-GDMS detection could be realized.

A microsecond-pulse (µs-pulse) glow discharge (GD) source boosted by a microwave-induced plasma (MIP) has been developed and studied for optical emission spectrometry (OES). The excitation processes of the tandem GD source were investigated. The analytical characteristics of the GD-OES source in the presence and absence of the MIP were compared, including the operating parameters, signal-to-background ratios (S/B) and relative standard deviation (RSD). The results show that under a relatively low discharge pressure (

The technique of on-line flow injection (FI) cobalt-ammonium pyrrolidin-1-yldithioformate (Co–APDC) coprecipitation for the preconcentration of trace amounts of the heavy metals Cd, Cu, Fe, Ni, Pb and Zn in rain water samples with simultaneous determination by inductively coupled plasma atomic emission spectrometry (KP-AES) has been developed. A precipitate collector system, consisting of a poly(tetrafluoroethylene)(PTFE) membrane on a polypropylene support filtering device combined with a 1.5 m reaction coil, was selected. An inorganic solution of concentrated nitric acid and hydrogen peroxide was applied as the dissolution reagent. The technique is characterized by high retention efficiency (which ranged from 77 to 99% for the six elements of interest), good enrichment factors (ranging from 10 to 50 for 100 s preconcentration depending on the elements studied) and satisfactory accuracy and precision (recoveries from two standard additions to a rain sample ranged from 92 to 104%, with relative standard deviations ranging from 1.9 to 5%). The sample throughput is 20 per hour.

A fully alkaline procedure, including alkaline fusion, pre-reduction of Se(VI) to Se(IV) in alkaline medium and an alkaline mode of H2Se generation, together with ICP-AES for the determination of total Se in biological and environmental samples, is described. Alkaline fusion coupled with alkaline mode hydride generation could effectively avoid volatile losses of selenium by changing it into soluble salts such as selenate or selenite and greatly eliminate the chemical interference from the co-existing transition metals Fe, Cu, and Mn. The method was verified with a certified reference material and was successfully applied to several real samples such as selenium-enriched plasma, egg, animal feeds and soils with satisfactory results.

A flow injection–electrochemical hydride generation technique for atomic absorption spectrometry has been developed in order to avoid the use of sodium tetrahydroborate, which is capable of introducing contamination. A specially designed thin-layer electrolytic flow cell for hydride generation was used in a normal flow injection system coupled to an electrically heated T-tube atomizer for the atomic absorption measurements. About 200 µl of sample were injected into the electrolyte carrier stream flowing to the electrolytic cell, where hydride-forming elements were reduced to gaseous hydrides. The effects of various factors, e.g., electrode material, electrolyte, current density and carrier stream flow rate, on rate of formation of the hydride and interferences have been studied. The technique has been applied to the determination of As, Se and Sb in various samples. The detection limits for these elements in aqueous solutions were 0.45, 0.62 and 0.92 ng ml–1, respectively, with precisions of 1.2–1.8%.

Photoswitchable upconversion luminescence nanoprobes (ps-UCNPs) are capable of adjusting the luminescent emission of upconversion nanocrystals and producing photoswitchable imaging by photochromism of molecular switch diarylethenes (DTEs). Here we present a rational, and simple strategy for constructing reversible ps-UCNPs based on NaYF4:Yb,Er,Tm nanocrystals and DTEs trapped in one nanosystem using BSA-graft-dextran copolymer as a shell to form a nanocapsule. In this nanosystem ps-UCNPs exhibited effective photochromic behavior and photoswitchable upconversion luminescence (UCL) which was controlled by alternating UV/visible light. Importantly, the ps-UCNPs showed low cytotoxicity and may be used as a photoswitchable UCL nanoprobe for in vitro and in vivo bioimaging. This is the first photoswitchable probe for mouse-level bioimaging in vivo. Our design strategy provides a versatile process for constructing a special photo-modulated probe in bioimaging.

A segment flow protocol has been proposed for coupling nano-liquid chromatography (nano-LC) with mass spectrometry (MS) in peptide-based proteomics research. LC effluent was segmented by perfluorodecalin oil and stored as segments in sequence to carry out the following off-line MSn analysis. In this way, incomplete identification of co-eluted peptides resulting from the MS scan rate, relatively slower than the LC elution rate, was solved to some extent for on-line coupling LC-MSn analysis. The complex proteins from a sample of T. tengcongensis were successfully identified with one run using segment as the interface between nano-LC and MSn analysis, compared to the total identified proteins with six runs using routine on-line nano-LC-MSn analysis. This segment flow approach could eliminate detection loss and sample cross-contamination, providing a new method for peptide-based proteomic research, especially when the amount of sample is limited.

Hierarchically ordered macro/mesoporous alumina has been successfully synthesized as a nanoreactor with multi-functions, which combine in situ digestion and in situ enrichment via one simple integrated step but with high efficiency.

In this work, for the first time, Ti(4+)-Fe3O4@polydopamine microspheres were designed and synthesized for efficient and selective enrichment of phosphopeptides in biological samples.

Secretomics is receiving more and more considerable attention due to the key roles of secreted proteins in cancer. Most of the potential biomarkers for clinical diagnosis and treatment of cancer are secreted proteins. However, the low concentration of secreted proteins and contaminants released from dead cells are a great challenge to secretomic profiling studies. Although some bioinformatics tools such as SecretomeP and SignalP can help to annotate or predict secreted proteins, they also cause false positive or negative rates of identification especially for nonclassical secreted proteins. Therefore, an iTRAQ based quantitative proteomics strategy was set up in this work and applied in the secretomics study of metastatic HCC cell lines. A total of 94 proteins were identified as secreted and 31 of them were newly found in our data. Compared with the known secreted proteins participating in inter-cellular signalling, most of the newly identified secreted proteins were metabolic enzymes, such as PKM2 and EHHADH, whose functions focused on the synthesis/metabolism of glucose, fatty acids and amino acids. Exploring their secretion would help to further study their bio-functions in conditioned media and the effects on the interactions of cancer cells and the microenvironment. Differences between the secretomes of the two metastatic HCC cell lines were also explored in the same experiment. This strategy showed its superiority in accurately identifying secreted proteins as well as monitoring their variation under different biological conditions.

Herein we report a novel test strip capable of rapid water toxicity assessment, which is economical and easily applicable compared with conventional methods, and is especially useful for field application. The test trip is made from hydrogel containing Vibrio fischeri. The toxicity assessment is based on the measurement of the changing of bacterial bioluminescence when water pollutants exist. The test trip was validated with different metal ions and organic compounds representing various pollutants. Our tests showed a great linear relation between the gamma value (Γt) and the concentrations of pollutants. The strip also showed high reliability and reproducibility when tested with real water samples, which suggested its potential application in environmental applications.

A spherical liquid-liquid interface can be obtained by dispersing one liquid phase into another to form droplets, which will facilitate the two-phase reactions between the immiscible participating fluids. The phase transfer catalysts assembled at the droplet "wall" catalyze the reactions between the aqueous and organic phases. The study illustrates an interfacial synthetic approach which is ideal for the biphasic reaction by taking advantage of the droplet-based microdevice. The improved reaction efficiency can be attributed to the high surface-to-volume ratio and internal flow circulation in the droplets.

With an ultra-high surface area and abundant functional groups, graphene oxide (GO) provides an ideal substrate for the immobilization of trypsin. We demonstrated that trypsin could be immobilized on GO sheets assisted by polymers as molecular spacers to maintain the activity of the enzyme. And with the trypsin-linked GO as the enzyme immobilization probe, a novel microwave-assisted on-plate digestion method has been developed with subsequent analysis by MALDI-MS. The feasibility and performance of the digestion approach were demonstrated by the proteolysis of standard proteins. The results show that this novel approach substantially accelerated proteolysis and reduced the time required for traditional procedures involving on-plate enzymatic digestion and sample preparation prior to MALDI-MS analysis. The novel digestion approach is simple and efficient, offering great promise for high throughput protein identification.

Hepatocellular carcinoma (HCC) is one of the most common and aggressive malignant tumors worldwide. The prognosis of patients with HCC still remains very dismal, mainly due to metastasis. We found that high-expression levels of AGR2 existed in metastatic HCC cell lines and patient samples. Overexpression of AGR2 was found to be correlated to the metastatic status of HCC cells, and inhibition of AGR2 by siRNA resulted in a dramatic decline in invasion abilities in metastatic cells in vitro. Overexpression of AGR2 increased the invasion of HCC cells in vitro and also in vivo with a nude mouse model. The tandem affinity purification (TAP) identified 18 AGR2-binding proteins and IPA analysis revealed that these proteins focus on MAPK and Caspase pathway. Therefore, we speculate that the overexpression of AGR2 can promote HCC metastasis, possibly by affecting MAPK and Caspase pathway through AGR2-interacting proteins.

As one of the most comprehensive and versatile tools for investigating proteomics, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) still faces the problem of identification of low abundant proteins and post-translational modifications (PTMs) of proteins. These proteins typically require concentration and isolation prior to MS analysis. The surfaces of MALDI targets have been modified so they can be used not only as sample supports but as functional substrates for sample enrichment. These modified targets are therefore capable of concentrating and binding molecules of interest selectively from sample solutions placed on them. In this report, current on-plate techniques employed for enrichment of low-abundance proteins, including those for selective capture of phosphopeptides and glycopeptides prior to MALDI-MS analysis, were reviewed.

A hierarchical Fe-ZSM-5 zeolite monolithic column was fabricated for immobilization of low abundance phosphoprotein through specific coordination between heteroatomic Fe in the framework of the zeolite with the phosphate group in the micro-environment of the protein. Compared to traditionally immobilized metal ion chromatography, this method could be directly manipulated and handily adapted for phosphoproteomics identification.

Human hepatocellular carcinoma (HCC) is one of the most malignant tumors, being particularly induced by unregulated growth and metastasis, and is a leading cause of death and major health problems in many countries. We report here the identification of 167 differentially expressed proteins between HCC (MHCC97-H) cells and Chang liver cells using enhanced nano-liquid chromatography/mass spectrometry (LC/MS). The most relevant pathways of differentially expressed proteins are involved in cytoskeleton organization, stress defense, and energy homeostasis etc. Moreover, of the identified proteins, there are 59 known or putative membrane-associated proteins with multitransmembrane domains confirmed by bioinformatic analysis. These proteins may be associated with cancer, reflecting tumorigenesis of HCC, and would be useful for the development of diagnostic and subsequently pharmaceutical targets of HCC. In addition, we identify a total of 41 proteins that are found to be up- or down-regulated following tanshinone IIA treatment for MHCC97H cells in a time-depended manner. Also, several proteins that are involved in actin cytoskeleton and stress resistance are mainly down-regulated, whereas proteins associated with cell redox homeostasis, mitochondrial, and microtubule-based movement are identified as mostly up-regulated after the treatment. Determination of functional roles of those differentially expressed proteins will enable further understanding of the mechanism of HCC tumorigenesis and exploration of new drugs for therapeutic intervention.

A high-concentration with low viscosity ceramic silicon carbide (SiC) slurry prepared for ICP-OES determination of ultra-trace impurities is described in this paper. Good fluidity can be kept up to the slurry concentration as high as 30% (m v−1) by adding 2% polyethylene imine (PEI) as a dispersant at pH 4.0. Stability of the high content slurry of nm-size SiC is characterized by zeta potential measurement and viscosity measurement, and medium pH is experimentally optimized. The analysis can be calibrated using simple aqueous standards in case a high-concentration slurry is nebulized. Owing to extremely low blanks and unusually highly slurry concentration (20% m v−1), extraordinarily low limits of detection ranging from 2 (Mn, Ti) to 100 (Al) ng g−1 could be achieved.

In this work, we synthesized α-Fe(2)O(3)@SnO(2) core-shell structure nanotubes by a facile two-step hydrothermal method for selective enrichment of phosphopeptides. The core-shell structure nanotubes were found to have outer diameters of 90-110 nm, thicknesses of 30 nm, and lengths of 260-280 nm. SnO(2) nanoparticles with an average crystallite size of around 5 nm form a layer of about 10 nm on both walls of the α-Fe(2)O(3) nanotubes. To demonstrate their ability for selective enrichment of phosphopeptides, we applied α-Fe(2)O(3)@SnO(2) nanotubes to the isolation and enrichment of the phosphopeptides from standard protein digestion and real samples. The enriched peptides were analyzed by MALDI-MS and LC-ESI MS. Experiment results demonstrate that SnO(2) coated α-Fe(2)O(3) nanotubes show excellent potential for selective enrichment of phosphopeptides.

A simple, rapid and reliable method for the determination of Al, Ca, Cr, Cu, Fe, Mg, Mn, Na, Ni, Si, Ti, V and Zr in high purity boron carbide (B4C) using slurry introduction axial viewed inductively coupled plasma optical emission spectrometry (ICP-OES) is described. The sample slurry was prepared by directly dispersing the powdery boron carbide in an aqueous solution without dispersant addition. The accuracy was verified by comparison of the results with those obtained by various other methods and the value of certified reference material ERM-ED 102 (boron carbide powder). Owing to a rather low contamination in the sample preparation and stability of the slurry, the LODs, which were in the range of 0.02–2 µg g−1, were superior to those of the conventional nebulization ICP-OES technique or solid dc-OES.

In this work, aminophenylboronic acid-functionalized magnetic nanoparticles were synthesized, and applied to selective separation of glycopeptides and glycoproteins.

Characterization of the stability of ceramic suspension for slurry introduction in inductively coupled plasma optical emission spectrometry (ICP-OES) and its application to the analysis of aluminium nitride (AlN) was reported in this paper. Stability and homogeneity suspensions of μm sized AlN and nm sized AlN, as the representatives selected, were characterized by sedimentation test, scanning electron microscope observation and zeta potential measurement. The zeta potential of the interface between the particle and the medium can be controlled by pH adjustment and adding 0.8 wt% polyethylene imine (PEI) for μm size AlN or 2.0 wt% PEI for nm size AlN, respectively. The analytical results obtained via slurry introduction were compared with those via nebulization of aqueous solutions prepared by fusion digestion. The nm size AlN can be directly analyzed by using slurry nebulization ICP-OES with aqueous standards calibration, and the impurities Cu, Fe, Mg, Mn, etc. in μm size AlN can also be determined by slurry method, but the results of some elements with high boiling points, such as Si, Y, etc., show deviation from the reference values.

Metal-ion-immobilized zeolite nanoparticles have been applied for the first time to isolate phosphopeptides from tryptic beta-casein digest; the phosphopeptides enriched on the modified zeolite nanoparticles could be effectively identified by MALDI-TOF-MS/MS.

The strategy presented in this work supplies a general method of controlling protein assembly on a switchable low-density SAM, which may open a new way to design functional biocomposite films for biosensors or protein chips.

A slurry sample introduction technique for the analysis of TiO2 powders by axial viewing ICP-OES is reported. Relationships between stable slurries and the conditions, such as particle size, pH, dispersant and its amount, were experimentally investigated. Slurries were prepared by mixing the TiO2 powder with the dispersant poly(acrylate amine) (NH4PAA) and agitation in an ultrasonic bath to ensure good dispersion. The pH of the medium and amount of dispersant has been optimized. Impurities in TiO2 were determined by an axial viewing ICP-OES spectrometer. As representatives, a Standard Reference Material 154 b of µm particle size TiO2 and a nm particle size TiO2 were selected and determined for micro and trace impurities. Analytical results obtained via slurry sample introduction were compared with those via nebulization of aqueous solutions prepared by acid digestion and fusion digestion. The determined results by slurry introduction were in good accordance with the stated values, which verified that the calibration curves could be established by aqueous standards.

This paper describes the use of palladium salt as chemical modifier for the determination of silicon by electrothermal atomic absorption spectrometry. It is found that the optimal atomization temperature of silicon appeared to be flat above 2500 °C and that the sensitivity was significantly improved in the presence of palladium. The method was validated by the analysis of National Bureau of Standards (now National Institute for Standards and Technology) Standard Reference Materials 361, 362 and 363 Low Alloy Steels.

A 9-mm torch and a 40.68-MHz radiofrequency power supply were evaluated for use in inductively coupled plasma mass spectrometry (ICP-MS). With this system, an analytically useful plasma can be supported at 850 W applied r.f. power and 8.7 l min–1 total argon flow-rate. The effects of operating parameters (nebuliser gas flow-rate, r.f. power, sampling depth and ion-lens voltages) on the analyte ion signals were determined. The 9-mm source exhibits greater independence of the ion-optic bias potential on relative atomic mass than do conventional-sized torches. Further, the 9-mm system produced similar sensitivities, detection limits, doubly charged ion ratios and oxide ion ratios to the conventional plasma but with lower power and argon consumption. However, the proper placement of the discharge under the interface was found to be critical to obtain maximum signal levels.