Proteomic analysis of pervanadate-induced tyrosine-phosphorylated proteins in hepatocellular carcinoma WRL 68 cells
ABSTRACT: Proteomic analysis of pervanadate-induced tyrosine-phosphorylated proteins in hepatocellular carcinoma WRL 68 cells Protein tyrosine phosphorylation plays critical roles in modulating biological processes such as cellular proliferation, differentiation, migration, apoptosis and metabolism. To profile tyrosine phosphorylated (pTyr) proteins as well as search novel pTyr proteins as cross-talk points among different cellular pathways, we developed a rapid and efficient approach to identify cellular pTyr proteins and their complexes by a combination of subcellular proteomics approach with signal transduction strategies. Human hepatocytic cells from WRL68 cell line were treated with pervanadate (POV), subfractionated into four fractions and then subjected to immunoaffinity purification with anti-pTyr antibody. The eluted mixtures of the anti-pTyr purification were identified by LC-MS/MS. Subcellular fractionation and affinity purification of tyrosine-phosphorylated proteins: WRL68 cells were first grown to 80% confluence in MEM complete medium and then the medium replaced with serum free media. After 15 h, the cells were either untreated or stimulated with 0.1 mM pervanadate (1 mM sodium orthovanadate, 3 mM H2O2) for 10 min. 150-mm cultures of WRL 68 cells were rinsed twice with 4? PBS and then scraped from the dish in 750?l of hypotonic buffer (10 mM Tris, 1 mM NaF, 10 mM IAA, pH 7.5) containing a cocktail of protein inhibitors. After a 20-min incubation on ice, the cells were passed about five times through a 25-g needle. The resulting lysate was subjected to a 15min centrifugation at 1000 rpm at 4?, after which the pellet was resuspended in 250?l of hypotonic buffer and re-extracted by a second round of the trituration and centrifugation. The supernatants of the first and second spins were combined, adjusted to 0.25 M NaCl, and separated into cytosolic (supernatant) and membrane (pellet) fractions bycentrifugation at 19,000 rpm (43,000 g) for 90 min at 4?. All the pellets and total cell lysate were resuspended in RIPA buffer (50 mM Tris-HCl, 150 mM NaCl, 1% Triton X-100, 0.1% SDS, 1% deoxycholic acid sodium) containing 1mM pervanadate with a cocktail of protein inhibitors with sonication aid. Cleared cell lysates were incubated overnight at 4? with 30?l monoclonal anti-phosphotyrosine-agrose (Sigma). Precipitated immune complexes were washed three times with 1×HNTG (20 mM HEPES, 150 mM NaCl, 0.1% Triton X-100, 10% Glycerol, pH 7.5) and then eluted with 100 mM phenyl phosphate (Sigma) in lysis buffer at 4?. Enzyme digestion, mass spectrometry and protein identification: The sample was digested according to the published method. Chromatography was performed using a surveyor LC system (Thermo Finnigan,SanJose,CA) on C18 reverse phase column(RP, 180 µm x 150 mm, BioBasic® C18, 5 µm, Thermo Hypersil-Keystone). The pump flow rate is split 1:100 for a colum flow rate of 1.5 µL/min.The column effluent is directly electrosprayed using the orthogonal metal needle source without further splitting.Mobile phase A is 0.1% formic acid in water,and the B mobile phase is 0.1% formic acid in acetonitrile. The separation of peptides obtained by enzymatic digest of bile sample was achieved with a gradient of 2-80% B over 360 min.The column effluent from the reverse phase column was analyzed by LCQ Deca XP ion-trap mass spectrometer.The micro-electrospray interface uses a 30 µm metal needle that is orthogonal to the inlet of the LCQ.The mass spectrometer was set that one full MS scan was followed by three MS/MS scans on the three most intense ion from the MS spectrum with the following Dynamic Exclusion™ settings: repeat count, 1; repeat duration, 0.5 min; exclusion duration, 3.0 min. The acquired MS/MS spectra were automatically searched against protein database for human proteins (SWISS-PROT/TrEMBL) using the TurboSEQUEST program in the BioWorks™ 3.0 software suite. An accepted SEQUEST result had to have a ?Cn score of at least 0.1 (regardless of charge state) and Xcorr (one charge?1.5, two charges?2.0, three charges?2.5). Single peptides that alone identify a protein were manually validated after meeting the above criteria. Bioinformatics analysis: The pI and MW of the proteins were analyzed using ExPASy proteomics tools accessed from http://cn.expasy.org/tools/#proteome. The grand average hydropathicity (GRAVY) values were determined according to Kyte-Doolittle. The protein subcellular location annotation was from SwissProt &TrEMBL protein database (http://us.expasy.org/sprot/). The protein function family was categorized according to Gene Ontology (GO) annotation terms extracted by InterPro (http://www.ebi.ac.uk./interpro/). The annotation of protein phosphorylation was from SwissProt &TrEMBL protein database (http://us.expasy.org/sprot/) and PhosphoSite (http://www.phosphosite.org). The kinases were annotated according to human kinome. Keywords: other
INSTRUMENT(S): Proteomic analysis of pervanadate-induced tyrosine-phosphorylated proteins in hepatocellular carcinoma WRL 68 cells
Project description:Leaves of Brachypodium distachyon Bd21 were collected at three leaf stage. The total proteins were extracted and then phosphopeptides were enriched by using TiO2 microcolumns and phosphopeptides and their corresponding proteins were identified with LC-MS/MS and Maxquant software. In details, enriched phosphopeptides were separated on a self-packed C18 reverse phase column (75 μm I.D., 150 mm length) (Column Technology Inc., Fremont, CA), which directly connected the nano electrospray ion source to a LTQ-Orbitrap XL mass spectrometer. Pump flow was split to achieve a flow rate at 1 μL/min for sample loading and 300 nL/min for MS analysis. The mobile phases consisted of 0.1% FA (A) and 0.1% FA and 80% ACN (B). A five-step linear gradient of 5% to 30% B in 105 min, 35% to 90% B in 16 min, 90% B in 4 min, 90% to 2% B for 0.5 min and 2% B for 14.5 min was performed. The spray voltage was set to 2.0 kV and the temperature of the heated capillary was 240ºC. For data acquisition, a data-dependent top 10 MS/MS spectraper MS full scan in the Orbitrapanalyser was used. The raw files were processed with Maxquant (version 126.96.36.199) and searched against the NCBI Brachypodium protein database (26,035 entries in total) concatenated with a decoy of reversed sequences. The following parameters were used for database searches: cysteine carbamidomethylation was selected as a fixed modification; methionine oxidation, protein N-terminal acetylation, and phosphorylation on serine, threonine and tyrosine were selected as variable modifications. Up to two missing cleavage points were allowed. The precursor ion mass tolerances were 7 ppm, and fragment ion mass tolerance was 0.5 Da for MS/MS spectra.
Project description:Bacteria were washed three times in NaCl (150 mM). Cells were resuspended in 1 ml TSU buffer (50 mM Tris pH 8.0, 0.1% SDS, 2.5 M urea) and lysed by two freeze-thaw cycles in liquid nitrogen. Lysate proteins (40 ug) were separated and digested. Digested peptides were separated by nano-LC using an Ultimate 3000 HPLC and autosampler system (Dionex; Amsterdam, Netherlands). Samples (1 ul) were concentrated and desalted onto a micro C18 pre-column (500 um×2 mm, Michrom Bioresources; Auburn, CA, USA) with H2O:CH3CN (98:2, 0.05% trifluoroacetic acid) at 15 ul min−1. After a 4 min wash the pre-column was switched (Valco 10 port valve; Dionex) into line with a fritless nano column (75 u×~10 cm) containing C18 media (5 u, 200 A Magic; Michrom) manufactured according to Gatlin. Peptides were eluted using a linear gradient of H2O:CH3CN (98:2, 0.1% formic acid) to H2O:CH3CN (64:36, 0.1% formic acid) at 250 nl min−1 over 30 min. High voltage (2000 V) was applied to low volume tee (Upchurch Scientific) and the column tip positioned ~0.5 cm from the heated capillary (T = 280 degrees C) of an Orbitrap Velos (Thermo Electron; Bremen, Germany) mass spectrometer. Positive ions were generated by electrospray and the Orbitrap operated in data dependent acquisition mode (DDA). A survey scan m/z 350–1750 was acquired in the Orbitrap (Resolution = 30,000 at m/z 400, with an accumulation target value of 1,000,000 ions) with lockmass enabled. Up to the 10 most abundant ions (>5,000 counts) with charge states >+2 were sequentially isolated and fragmented within the linear ion trap using collisionally induced dissociation with an activation q = 0.25 and activation time of 30 ms at a target value of 30,000 ions. M/z ratios selected for MS/MS were dynamically excluded for 30 s. Peak lists were generated using Mascot Daemon/extract_msn (Matrix Science, Thermo; London, England) using the default parameters, and submitted to the database search program Mascot (version 2.1, Matrix Science). Search parameters were: Precursor tolerance 4 ppm and product ion tolerances +/-0.4 Da; Oxidation (M) and Carbamidomethyl (C) specified as variable modifications, Enzyme specificity was trypsin, 1 missed cleavage was possible
Project description:Washed three times in NaCl (150 mM). Cells were resuspended in 1 ml TSU buffer (50 mM Tris pH 8.0, 0.1% SDS, 2.5 M urea) and lysed by two freeze-thaw cycles in liquid nitrogen. Lysate proteins (40 ug) were separated and digested. Digested peptides were separated by nano-LC using an Ultimate 3000 HPLC and autosampler system (Dionex; Amsterdam, Netherlands). Samples (1 ul) were concentrated and desalted onto a micro C18 pre-column (500 um×2 mm, Michrom Bioresources; Auburn, CA, USA) with H2O:CH3CN (98:2, 0.05% trifluoroacetic acid) at 15 ul min−1. After a 4 min wash the pre-column was switched (Valco 10 port valve; Dionex) into line with a fritless nano column (75 u×~10 cm) containing C18 media (5 u, 200 A Magic; Michrom) manufactured according to Gatlin. Peptides were eluted using a linear gradient of H2O:CH3CN (98:2, 0.1% formic acid) to H2O:CH3CN (64:36, 0.1% formic acid) at 250 nl min−1 over 30 min. High voltage (2000 V) was applied to low volume tee (Upchurch Scientific) and the column tip positioned ~0.5 cm from the heated capillary (T = 280 degrees C) of an Orbitrap Velos (Thermo Electron; Bremen, Germany) mass spectrometer. Positive ions were generated by electrospray and the Orbitrap operated in data dependent acquisition mode (DDA). A survey scan m/z 350–1750 was acquired in the Orbitrap (Resolution = 30,000 at m/z 400, with an accumulation target value of 1,000,000 ions) with lockmass enabled. Up to the 10 most abundant ions (>5,000 counts) with charge states >+2 were sequentially isolated and fragmented within the linear ion trap using collisionally induced dissociation with an activation q = 0.25 and activation time of 30 ms at a target value of 30,000 ions. M/z ratios selected for MS/MS were dynamically excluded for 30 s. Peak lists were generated using Mascot Daemon/extract_msn (Matrix Science, Thermo; London, England) using the default parameters, and submitted to the database search program Mascot (version 2.1, Matrix Science). Search parameters were: Precursor tolerance 4 ppm and product ion tolerances +/-0.4 Da Oxidation (M) and Carbamidomethyl (C) specified as variable modifications Enzyme specificity was trypsin, 1 missed cleavage was possible
Project description:Cyanophora paradoxa muroplasts were isolated on a Percoll gradient. Muroplasts were fractionated into soluble (stroma), envelope, and thylakoid proteins. Protein samples from envelope membranes, thylakoids, stroma and total muroplasts were separated by 12% SDS-PAGE. Each Protein lanewas cut into 10 slices of variable size to match similar protein amounts. The gel slices were washed and diced to 1mm3 cubes. Gel pieces were destained by two consecutive washes with a 50:50 mixture of 200 mM ammonium bicarbonate and acetonitrile (ACN) for 20 min at 37°C. Proteins were reduced with 10mM DTT for 45 min at 56°C, followed by alkylation with 55mM iodoacetamide for 45 min at room temperature in the dark. After reduction and alkylation, gel pieces were washed twice with 100 mM ammonium bicarbonate, dehydrated with 100% ACN for 10 min, and dried in a SpeedVac. Gel pieces were fully covered in 50 mM ammonium bicarbonate containing 10ng/ml trypsin and rehydrated at 4°C. The samples were incubated overnight at 37°C and peptides in the supernatant were pooled after successive extraction steps using 50 mM ammonium bicarbonate, 100% ACN and 2.5% formic acid (FA), 50% ACN. The samples were dried in a SpeedVac and reconstituted in 5% ACN, 0.1% FA prior to MS analysis. Each of the samples were analysed in duplicates. Tryptic peptides of the thylakoid, envelope and stroma fractions were loaded onto a fritless 100 μm capillary packed in-house with 10cm of ProntoSIL C18 ace-EPS, 3µm. A gradient of 5-80% (v/v) ACN in 0.1% (v/v) FA was passed over the column with a duration of 115 min. The eluted peptides were directly electrosprayed into the LTQ orbitrap XL MS at a flow rate of 250 nl min-1 and a spray voltage of 1.3 kV. The instrument was operated in a 4-step data-dependent positive mode to identify the top three most abundant ions in a high-resolution MS scan (400 to 2000 m/z), which were then selected for fragmentation. MudPIT analyses were performed on the muroplast samples using an in-house packed analytical column consisting of 10 cm ProntoSIL C18 ace-EPS, 3µm (Bischoff) and 2 cm of a strong cationic exchange (SCX) material, 3µm in combination with an 6-step salt pulse gradient (0, 50, 100, 150, 200 and 500 mM ammonium acetate). Each salt-step peptides were eluted from the SCX to the C18-phase of the analytical column and eluated with a 130- min reverse-phase solvent gradient (5–80% ACN containing 0.1% FA). The eluate was directly electrosprayed into the LTQ orbitrap XL MS which was operated as described before. All MS/MS samples were analyzed using Sequest and X! Tandem. Sequest was set up to search the C. paradoxa nuclear and muroplast protein database with a total of 32,286 entries, assuming the digestion enzyme trypsin. X! Tandem was set up to search a subset of the C. paradoxa database also assuming trypsin. Sequest and X! Tandem were searched with a fragment ion mass tolerance of 0,80 Da and a parent ion tolerance of 10,0 ppm. Oxidation of methionine and iodoacetamide derivatives of cysteine were specified in Sequest and X! Tandem as variable modifications. Scaffold (version 3.5.1, Proteome Software Inc., Portland, OR) was used to validate MS/MS based peptide and protein identifications. Peptide identifications were accepted if they could be established at greater than 95,0% probability as specified by the Peptide Prophet algorithm. Protein identifications were accepted if they could be established at greater than 99,0% probability and contained at least 2 identified peptides.
Project description:MIADB: a cumulative collection of 172 tandem mass spectrometry (MS/MS) of a vast array of monoterpene indole alkaloids. Samples were analyzed using an Agilent LC-MS system composed of an Agilent 1260 Infinity HPLC coupled to an Agilent 6530 ESI-Q-TOF-MS operating in positive mode. A Sunfire analytical C18 column (150 × 2.1 mm; i.d. 3.5 μm, Waters) was used, with a flow rate of 250 μL/min and a linear gradient from 5% B (A: H2O + 0.1% formic acid, B: MeOH) to 100% B over 30 min. ESI conditions were set with the capillary temperature at 320 °C, source voltage at 3.5 kV, and a sheath gas flow rate of 10 L/min. The divert valve was set to waste for the first 3 min. There were four scan events: positive MS, window from m/z 100−1200, then three data-dependent MS/MS scans of the first, second, and third most intense ions from the first scan event. MS/MS settings were three fixed collision energies (30, 50, and 70 eV), default charge of 1, minimum intensity of 5000 counts, and isolation width of m/z 2. In the positive-ion mode, purine C5H4N4 [M + H]+ ion (m/z 121.050873) and the hexakis(1H,1H,3H-tetrafluoropropoxy)-phosphazene C18H18F24N3O6P3 [M + H]+ ion (m/z 922.009 798) were used as internal lock masses. Full scans were acquired at a resolution of 11 000 (at m/z 922). A permanent MS/MS exclusion list criterion was set to prevent oversampling of the internal calibrant.
Project description:Human primary macrophages were infected with influenza A virus (H3N2/Udorn strain, HA 256) for 6 hrs or left untreated. Cells were collected and lysed with HEPES lysis buffer (50 mM HEPES, 150 mM NaCl, 1 mM EDTA, 1 % NP-40, pH 7.4) including protease and phosphatase inhibitor cocktails. The cell lysates were centrifuged and the supernatant was collected and the protein content was measured with Bio-Rad DC™ protein assay (Bio-Rad). The proteins were reduced, alkylated, and enzymatically digested in-solution with trypsin. The digestion was stopped by adding FA (final c = 1 %). The samples were centrifuged 9168 x g for 10 min and desalted with Sep-Pak Vac RP C18 cartridges (Waters, MA, USA), following fractionation by strong cation exchange chromatography (SCX). The peptides were separated on a 200 x 4.6 mm, 5 μm, 200 Å PolySULFOETHYL A™ column (PolyLC, USA). The fractions were vacuum centrifuged and desalted as before, following phosphopeptide-enrichment with PHOS-Select™ Iron Affinity Gel (Sigma Aldrich, MO, USA). LC-MS/MS was performed with a Q Exactive hybrid quadrupole-orbitrap tandem mass spectrometer coupled to an EASY-nLC 1000 nanoflow liquid chromatograph (Thermo Fisher Scientific). A 100 μm x 3 cm trap column and a 75 μm x 15 cm analytical column were in-house packed with Magic C18AQ resin (200 Å, 5 μm; Michrom Bioresources). The mobile phases were 2% acetonitrile, 0.2% formic acid (A) and 95% acetonitrile, 0.2% formic acid (B). LC gradient elution condition was 2% B (0 min), 20% B (70 min), 40% B (100 min), and then 100% B (105-110 min), with a flow rate of 300 nl/min. Data dependent acquisition was performed in positive ion mode. MS spectra were acquired from m/z 300 to m/z 2000 at a resolution of 70,000 at m/z 200 with a target value of 1,000,000 and maximum injection time of 120 ms. The 10 most abundant precursor ions of which charge states were 2+ or higher were selected for higher energy collisional dissociation (HCD) with an isolation window of 2 and normalized collision energy of 30. MS/MS spectra were acquired at a resolution of 17,500 at m/z 200 with a target value of 50,000, maximum injection time of 250 ms, and the lowest mass fixed at m/z 100. Dynamic exclusion duration was 30 s.
Project description:Female Sprague-Dawley rats were randomly separated into two groups: i) trained (Ex group) and ii) sedentary (Cont group). Animals from the Ex group were adapted to treadmill exercise for two consecutive weeks, involving a gradual increase in the running time till 60 min/day at 20 m/min, 0% grade, 5 days/week. This exercise program remained constant until the end of the 54 weeks. Mitochondria isolation from 10 animals (5 Ex group and 5 Cont group) was performed using the conventional methods of differential centrifugation. Mitochondrial protein extracts were reduced with dithiothreitol, alkylated with iodoacetamide and digested with trypsin using the FASP procedure (18). Briefly, each sample was solubilized in 4 % SDS, 0.1 M DTT, 0.1 M HEPES and incubated for 30 min at 60 C. Then, samples were mixed with 0.2 mL of a solution of 8 M Urea, 0.1 M HEPES, pH 8.5 (UH solution), loaded into the filtration devices (3k Microcon, Millipore), centrifuged at 14,000 g for 20 min, and washed twice with UH solution. After centrifugation, the concentrates were alkylated with 50 mM iodoacetamide in UH solution (dark, 25 C, 20 min), and washed twice with UH solution. The concentrate was diluted with 0.1 mL of 50 mM ammonium bicarbonate (ABC) and digested overnight (37 C) with the addition of 2 ug of trypsin diluted in 30 uL of 50 mM ABC. The resulting tryptic peptides were collected by centrifugation and the filter were washed twice with 50 uL of 50 mM ABC. Eluted peptides were acidified with 10 uL of formic acid and cleaned up on a homemade Empore C18 column (3M, St. Paul, MN, USA) (ref) for subsequent phospho-enrichment and/or analysis by LC-MS/MS. The dried protein digest was dissolved with 10 uL (3 % ACN, 0.1 % TFA), diluted 1:5 with loading buffer (1 M glycolic acid, 5 % TFA, 80 % ACN) and phosphopeptides were enriched on TiO2-beads as previously described (19). Briefly 5 mg of "Titansphere TiO2 5 um" were suspended in 100 uL of 100 % ACN, immobilized in a pipette-column and washed using 5 uL of loading buffer. Each sample was loaded in each pipette-column and then washed with 30 uL of washing buffer (1 % TFA, 80 % ACN). Phosphopeptides were eluted from the beads with 25 uL of 25 % ACN (v/v) containing 25 % NH4OH (m/v), acidified with 10 uL of 10 % TFA and vacuum- concentrated to approximately 4 uL. Samples were finally diluted to 10 uL with H2O + 0.1% formic acid prior to injection. The peptides mixtures were analyzed by online nanoflow liquid chromatography tandem mass spectrometry (nanoLC-MS/MS) on an EASY-nLC system (Proxeon Biosystems, Odense, Denmark) connected to the LTQ Orbitrap Velos instrument (Thermo Fisher Scientific, Bremen, Germany) through a nanoelectrospray ion source. Six microliters of the peptide mixture were auto-sampled directly onto the analytical HPLC column (120 mm x75 um I.D., 3 um particle size (Nikkyo Technos Co., Ltd.) with a 120-min gradient from 5 % to 50 % ACN in 0.1 % FA. The effluent from the HPLC column was directly electrosprayed into the mass spectrometer. The LTQ Orbitrap Velos instrument was operated in data-dependent acquisition mode to automatically switch between full scan MS and MS/MS acquisition. The MS survey scan was performed in the FT cell recording a window between 350 and 2000 m/z. The resolution was set to 60 000, and the automatic gain control was set to 1,000,000 ions with a maximal acquisition time of 400 ms. The 20 most intense peptide ions with charge states great than or equal to 2 were sequentially isolated to a target value of 5,000 and fragmented in the high-pressure linear ion trap by low-energy CID with normalized collision energy of 35% Q value of 0.25, and an activation time of 10 ms. Raw files were processed using Proteome Discoverer version 1.3 (Thermo Fisher Scientific, Bremen). Peak lists were searched using Mascot software version 2.3 (Matrix Science, UK) against a SwissProt database containing entries corresponding to Rattus norvegicus (version of July 2012), a list of common contaminants, and all the corresponding decoy entries. Trypsin was chosen as enzyme and a maximum of two miscleavages were allowed. Carbamidomethylation (C) was set as a fixed modification, whereas oxidation (M) and phosphorylation (STY) were used as variable modifications. Searches were performed using a peptide tolerance of 7 ppm, a product ion tolerance of 0.5 Da. Resulting data files were filtered for FDR less than 1 % at peptide level.
Project description:Staphylococcus aureus is a leading cause of human disease and can be difficult to treat due to both multi-drug resistance and the organism’s remarkable ability to persist in the host, which is thought to result from several complex regulatory networks that modify transcription in response to environmental stress. In this study, we characterize the global transcriptional response of S. aureus strain 8325 to the antibiotic ciprofloxacin. We find that ciprofloxacin induces prophage mobilization and also significant alterations in metabolism, most notably an upregulation of the tricarboxylic acid cycle. In addition, ciprofloxacin induces the SOS response, which based on a comparison of the wild-type and lexA mutant strains, we show includes the de-repression of sixteen genes. In addition to RecA, LexA, and the hypothetical proteins encoded by SACOL0436, SACOL1375, SACOL1986 and SACOL1999, the S. aureus SOS genes encode proteins involved in DNA metabolism and induced mutation. Finally, we show that rendering LexA uncleavable significantly sensitizes the pathogen to ciprofloxacin therapy in vivo. These observations suggest that the SOS response may play a critical role in the pathogenicity of S. aureus. Keywords: time course Overall design: Sample preparation for transcriptional analysis. For each strain, 3 clones were inoculated in TSB and incubated for 18 hours. Cultures were diluted 1:100 and incubated until they reached early log phase (OD600 ~0.5-0.6) at which point ciprofloxacin was added to a final concentration of 0.8 •g/ml. Immediately prior to ciprofloxacin addition, and again 30 and 120 minutes following addition, appropriate volumes from each of the 3 cultures per strain were pooled and added to 2 volumes of RNAprotect reagent (Qiagen). Cultures were centrifuged and cell pellets were stored at 4 ºC until RNA extraction. During the experiment, OD600 and viable cfu per ml were monitored for each of the cultures (Figure 2A and 2B). Total RNA was extracted using the RNeasy Mini kit (Qiagen) at the end of the sample collection period. This procedure was repeated 3 independent times to generate 3 samples at each time point for each strain. Generation of probes for microarray experiments. cDNA probes for microarray experiments were generated as follows. Briefly, 2 μg of total RNA in a mixture containing 6 μg of random hexamers (Invitrogen); 0.01 M dithiothreitol; an aminoallyl-deoxynucleoside triphosphate mixture containing 25 mM each dATP, dCTP, and dGTP, 15 mM dTTP, and 10 mM amino-allyl-dUTP (aa-dUTP) (Sigma); reaction buffer (Clontech); and 400 units of Powerscript reverse transcriptase (Clontech) were incubated at 42 °C overnight. The resulting RNA template was hydrolyzed by adding NaOH and EDTA to a final concentration of 0.2 and 0.1 M, respectively, and incubating at 65 °C for 15 min. Unincorporated aa-dUTP was removed with a Minelute column (Qiagen). The cDNA probes were eluted with phosphate buffer (4 mM KPO4, pH 8.5, in ultrapure water), dried, and resuspended in 0.1 M sodium carbonate buffer (pH 9.0). To couple the amino-allyl cDNA with fluorescent labels, normal human serum-Cy3 or normal human serum-Cy5 (Amersham) was added at room temperature and incubated for 2 h. Uncoupled label was removed using a Minelute column (Qiagen). Microarray hybridization, scanning, image analysis, normalization, and analysis. Epoxy-coated slides were prehybridized in 5´ SSC (1´ SSC, 0.15 M NaCl plus 0.015 M sodium citrate) (Invitrogen), 0.1% sodium dodecyl sulfate, and 1% bovine serum albumin at 42 °C for 60 min. The slides were then washed at room temperature with distilled water, dipped in isopropanol, and spun dry. Equal volumes of the appropriate Cy3- and Cy5-labeled probes were combined, dried and then resuspended in a solution of 40% formamide, 5´ SSC, and 0.1% sodium dodecyl sulfate. Resuspended probes were denatured by heating to 95ºC prior to hybridization. The probe mixture then was added to the microarray slide and allowed to hybridize overnight at 42 °C. Hybridized slides were washed sequentially in solutions of 1´ SSC-0.2% SDS, 0.1´ SSC-0.2% SDS, and 0.1´ SSC at room temperature, dried, and then scanned with an Axon GenePix 4000 scanner. Individual TIFF images from each channel were analyzed with TIGR Spotfinder (available at http://www.tigr.org/software/tm4). Microarray data were normalized by LocFit (LOWESS) Normalization in block mode using TIGR MIDAS software (available at http://www.tigr.org/software/tm4). Median spot intensity values were used to calculate the log2 ratio and fold change. Oligos with intensities less than 10,000 units were subtracted from the analysis to rule out background. All hybridizations were performed with a minimum of 1 flip dye experiment. Each hyb has 3 inslide replicates per oligo to rule out bias data.
Project description:Four bile samples collected from patients with a malignant (PAC, CC) or a nonmalignant (CP, BS) biliary stenosis were used for comparative proteomic analysis. Briefly, bile samples were centrifuged at 16,000/g/ for 10 min at 4 C. Each supernatant was delipided with Cleanascite (Biotech Support Group, North Brunswick, NJ, USA) and ultrafiltrated using a 3 kDa filter cut-off (YM-3 centricon, Millipore, Bedford, MA, USA). For each sample, 50 ug of proteins were mixed with 0.5 M triethylammonium bicarbonate (TEAB) buffer pH 8.0 to a total volume of 100 uL. One ug of bovine lactoglobulin (LACB) was spiked in each sample as an internal standard. Proteins were reduced and alkylated before digestion of N-linked oligosaccharides from glycoproteins using PNGase F (Sigma-Aldrich, St. Louis, MO, USA). Proteins were then digested with trypsin and the resulting peptides were tagged with one of the isobaric tags from the iTRAQ reagents 4plex kit (AB Sciex, Foster City, CA, USA) according to the manufacturer's instructions. The four samples were then pooled and dried under vacuum. Labeled peptides were fractionated according to their isoelectric point on an Agilent 3100 OFFGEL fractionator using 24 cm pH 3-10 linear immobilized pH gradients (GE Healthcare, Chalfont St. Giles, UK) following manufacturer's instructions. Fractions were then recovered in separate tubes for high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). MS analysis was performed on a LTQ Orbitrap XL from Thermo Electron (San Jose, CA, USA) equipped with a NanoAcquity HPLC system from Waters. Peptides were trapped on a home-made 5 um 200 A Magic C18 AQ (Michrom, Auburn, CA, USA) 0.1 x 20 mm pre-column and separated on a home-made 5 um 100 A Magic C18 AQ (Michrom) 0.75 x 150 mm column with a gravity-pulled emitter. The analytical separation was run for 65 min using a gradient of H_2 O/formic acid (FA) 99.9%/0.1% (solvent A) and CH_3 CN/FA 99.9%/0.1% (solvent B). The gradient was run at a flow rate of 220 nL/min as follows: 5% B for 1 min, from 5 to 35% B in 54 min, from 35 to 80% B in 10 min. For MS survey scans, the OT resolution was set to 60,000 and the ion population was set to 5 x 10^5 with an m/z window from 400 to 2000. Maximum of 3 precursors were selected for both collision-induced dissociation (CID) in the LTQ and high-energy C-trap dissociation (HCD) with analysis in the Orbitrap (OT). For MS/MS in the LTQ, the ion population was set to 1 x 10^4 (isolation width of 2 m/z) while for MS/MS detection in the OT, it was set to 2 x 10^5 , with resolution of 7,500, first mass at m/z = 100, and maximum injection time of 750 ms. The normalized collision energies were set to 35% for CID and 60% for HCD. Peak lists from MS analysis were searched against Uniprot_Swissprot database (version 2011_2) using Phenyx protein identification software (GeneBio, Geneva, Switzerland). /Homo Sapiens/ taxonomy was specified for database searching. The parent ion tolerance was set to 10 ppm. Variable amino acid modifications were oxidized methionine and deamidated asparagine. Carbamidomethylation of cysteines and iTRAQ-labeled peptides on the amino terminus and lysine were set as fixed modifications. Trypsin was selected as the enzyme, with one potential missed cleavage, and the normal cleavage mode was used. Only one search round was used with selection of "turbo" scoring. The peptide p value was 10^-2 for LTQ-OT data. Protein and peptide scores were set up to maintain the false positive rate below 5%.
Project description:Whole genome gene expression level changes in E. coli DH1 exposed to 150 mM [C2mim]Cl in mid exponential growth, and compared to a non-exposed strain. Total RNA was isolated from three biological replicates for each condition: 150 mM [C2mim]Cl exposed at OD(600nm) 0.6, after 30 and 60 min, no exposure to [C2mim]Cl at OD(600 nm) 0.6 after 30 and 60 min.