The authors acknowledge the University of Pittsburgh Start-up Funds and NIH, NIGMS R01 grant (GM 117191-01) to RASR.

Ethics Statement: Mice were purchased from an independent, non-profit biomedical research institution and housed in the Division of Laboratory Animal Resources at the University of Pittsburgh. All animal protocols were approved by the Institutional Animal Care and Use Committee at the University of Pittsburgh.
1. Protein Extraction and Generation of Peptides for Chemical-tagging
<ol>
	<li>Extract protein from tissue, cells, or bodily fluids.
	<ol>
		<li>Homogenize 60-90 mg o...

<ol>
	<li>Ong, S. -. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stable+Isotope+Labeling+by+Amino+Acids+in+Cell+Culture,+SILAC,+as+a+Simple+and+Accurate+Approach+to+Expression+Proteomics.">Stable Isotope Labeling by Amino Acids in Cell Culture, SILAC, as a Simple and Accurate Approach to Expression Proteomics.</a> Mol Cell Proteomics. 1 (5), 376-386 (2002).</li><li>Koehler, C. J., Arntzen, M. &. #. 2. 1. 6. ;., de Souza, G. A., Thiede, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Approach+for+Triplex-Isobaric+Peptide+Termini+Labeling+(Triplex-IPTL).">An Approach for Triplex-Isobaric Peptide Termini Labeling (Triplex-IPTL).</a> Anal. Chem. 85 (4), 2478-2485 (2013).</li><li>Langen, H. F., Evers, M., Wipf, S., Berndt, B., P, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> From Genome to Proteome 3rd Siena 2D Electrophoresis Meeting. , (1998).</li><li>Yao, X., Freas, A., Ramirez, J., Demirev, P. A., Fenselau, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteolytic+18O+Labeling+for+Comparative+Proteomics:+Model+Studies+with+Two+Serotypes+of+Adenovirus.">Proteolytic 18O Labeling for Comparative Proteomics: Model Studies with Two Serotypes of Adenovirus.</a> Anal. Chem. 73 (13), 2836-2842 (2001).</li><li>Reynolds, K. J., Yao, X., Fenselau, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteolytic+18O+Labeling+for+Comparative+Proteomics:+Evaluation+of+Endoprotease+Glu-C+as+the+Catalytic+Agent.">Proteolytic 18O Labeling for Comparative Proteomics: Evaluation of Endoprotease Glu-C as the Catalytic Agent.</a> J. Proteome Res. 1 (1), 27-33 (2002).</li><li>Gygi, S. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+analysis+of+complex+protein+mixtures+using+isotope-coded+affinity+tags.">Quantitative analysis of complex protein mixtures using isotope-coded affinity tags.</a> Nat Biotech. 17 (10), 994-999 (1999).</li><li>Schmidt, A., Kellermann, J., Lottspeich, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+strategy+for+quantitative+proteomics+using+isotope-coded+protein+labels.">A novel strategy for quantitative proteomics using isotope-coded protein labels.</a> PROTEOMICS. 5 (1), 4-15 (2005).</li><li>Thompson, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tandem+Mass+Tags:+A+Novel+Quantification+Strategy+for+Comparative+Analysis+of+Complex+Protein+Mixtures+by+MS/MS.">Tandem Mass Tags: A Novel Quantification Strategy for Comparative Analysis of Complex Protein Mixtures by MS/MS.</a> Anal. Chem. 75 (8), 1895-1904 (2003).</li><li>Ross, P. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiplexed+Protein+Quantitation+in+Saccharomyces+cerevisiae+Using+Amine-reactive+Isobaric+Tagging+Reagents.">Multiplexed Protein Quantitation in Saccharomyces cerevisiae Using Amine-reactive Isobaric Tagging Reagents.</a> Mol Cell Proteomics. 3 (12), 1154-1169 (2004).</li><li>Xiang, F., Ye, H., Chen, R., Fu, Q., Li, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=N,N-Dimethyl+Leucines+as+Novel+Isobaric+Tandem+Mass+Tags+for+Quantitative+Proteomics+and+Peptidomics.">N,N-Dimethyl Leucines as Novel Isobaric Tandem Mass Tags for Quantitative Proteomics and Peptidomics.</a> Anal. Chem. 82 (7), 2817-2825 (2010).</li><li>Ting, L., Rad, R., Gygi, S. P., Haas, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MS3+eliminates+ratio+distortion+in+isobaric+multiplexed+quantitative+proteomics.">MS3 eliminates ratio distortion in isobaric multiplexed quantitative proteomics.</a> Nat Meth. 8 (11), 937-940 (2011).</li><li>McAlister, G. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increasing+the+Multiplexing+Capacity+of+TMTs+Using+Reporter+Ion+Isotopologues+with+Isobaric+Masses.">Increasing the Multiplexing Capacity of TMTs Using Reporter Ion Isotopologues with Isobaric Masses.</a> Anal. Chem. 84 (17), 7469-7478 (2012).</li><li>Frost, D. C., Greer, T., Li, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-Resolution+Enabled+12-Plex+DiLeu+Isobaric+Tags+for+Quantitative+Proteomics.">High-Resolution Enabled 12-Plex DiLeu Isobaric Tags for Quantitative Proteomics.</a> Anal. Chem. 87 (3), 1646-1654 (2015).</li><li>Robinson, R. A. S., Evans, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+Sample+Multiplexing+for+Nitrotyrosine-Modified+Proteins+Using+Combined+Precursor+Isotopic+Labeling+and+Isobaric+Tagging.">Enhanced Sample Multiplexing for Nitrotyrosine-Modified Proteins Using Combined Precursor Isotopic Labeling and Isobaric Tagging.</a> Anal. Chem. 84 (11), 4677-4686 (2012).</li><li>Evans, A. R., Robinson, R. A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+combined+precursor+isotopic+labeling+and+isobaric+tagging+(cPILOT)+approach+with+selective+MS(3)+acquisition.">Global combined precursor isotopic labeling and isobaric tagging (cPILOT) approach with selective MS(3) acquisition.</a> Proteomics. 13 (22), 3267-3272 (2013).</li><li>Evans, A. R., Gu, L., Guerrero, R., Robinson, R. A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+cPILOT+analysis+of+the+APP/PS-1+mouse+liver+proteome.">Global cPILOT analysis of the APP/PS-1 mouse liver proteome.</a> PROTEOMICS - Clin Appl. 9 (9-10), 872-884 (2015).</li><li>Gu, L., Evans, A. R., Robinson, R. A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sample+Multiplexing+with+Cysteine-Selective+Approaches:+cysDML+and+cPILOT.">Sample Multiplexing with Cysteine-Selective Approaches: cysDML and cPILOT.</a> J. Am. Soc Mass Spectrom. 26 (4), 615-630 (2015).</li><li>Dephoure, N., Gygi, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperplexing:+A+Method+for+Higher-Order+Multiplexed+Quantitative+Proteomics+Provides+a+Map+of+the+Dynamic+Response+to+Rapamycin+in+Yeast.">Hyperplexing: A Method for Higher-Order Multiplexed Quantitative Proteomics Provides a Map of the Dynamic Response to Rapamycin in Yeast.</a> Sci Signal. 5 (217), rs2 (2012).</li><li>Hebert, A. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutron-encoded+mass+signatures+for+multiplexed+proteome+quantification.">Neutron-encoded mass signatures for multiplexed proteome quantification.</a> Nat Meth. 10 (4), 332-334 (2013).</li><li>Merrill, A. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NeuCode+Labels+for+Relative+Protein+Quantification.">NeuCode Labels for Relative Protein Quantification.</a> Mol Cell Proteomics. 13 (9), 2503-2512 (2014).</li><li>Braun, C. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+Multiple+Reporter+Ions+from+a+Single+Isobaric+Reagent+Increases+Multiplexing+Capacity+for+Quantitative+Proteomics.">Generation of Multiple Reporter Ions from a Single Isobaric Reagent Increases Multiplexing Capacity for Quantitative Proteomics.</a> Analytical Chemistry. 87 (19), 9855-9863 (2015).</li><li>Everley, R. A., Kunz, R. C., McAllister, F. E., Gygi, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increasing+Throughput+in+Targeted+Proteomics+Assays:+54-Plex+Quantitation+in+a+Single+Mass+Spectrometry+Run.">Increasing Throughput in Targeted Proteomics Assays: 54-Plex Quantitation in a Single Mass Spectrometry Run.</a> Anal. Chem. 85 (11), 5340-5346 (2013).</li><li>Gu, L., Robinson, R. A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-throughput+endogenous+measurement+of+S-nitrosylation+in+Alzheimer's+disease+using+oxidized+cysteine-selective+cPILOT.">High-throughput endogenous measurement of S-nitrosylation in Alzheimer's disease using oxidized cysteine-selective cPILOT.</a> Analyst. 141 (12), 3904-3915 (2016).</li><li>Cao, Z., Evans, A. R., Robinson, R. A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MS3-based+quantitative+proteomics+using+pulsed-Q+dissociation.">MS3-based quantitative proteomics using pulsed-Q dissociation.</a> Rapid Commun Mass Spectrom. 29 (11), 1025-1030 (2015).</li><li>Swaney, D. L., Wenger, C. D., Coon, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Value+of+Using+Multiple+Proteases+for+Large-Scale+Mass+Spectrometry-Based+Proteomics.">Value of Using Multiple Proteases for Large-Scale Mass Spectrometry-Based Proteomics.</a> J. Proteome Res. 9 (3), 1323-1329 (2010).</li><li>McAlister, G. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MultiNotch+MS3+Enables+Accurate,+Sensitive,+and+Multiplexed+Detection+of+Differential+Expression+across+Cancer+Cell+Line+Proteomes.">MultiNotch MS3 Enables Accurate, Sensitive, and Multiplexed Detection of Differential Expression across Cancer Cell Line Proteomes.</a> Anal. Chem. 86 (14), 7150-7158 (2014).</li></ol>

The authors have no competing interests.

cPILOT allows for the simultaneous measurement of more than 12 unique samples. In order to ensure successful tagging at both the N-terminus and lysine residues of peptides, it is imperative to have the correct pH for each set of reactions and to perform the dimethylation reaction first for peptide labeling. Selective dimethylation at the N-terminus is performed by having a pH at ~2.5 (&#177;0.2). This is achieved by exploiting the differences of the pKA&#39;s of the amino groups on lysine and the N-terminus. At pH 2.5, l...

Proteomics often involves the analysis of many samples used to better understand disease processes, enzyme kinetics, post-translational modifications, response to environmental stimuli, response to therapeutic treatments, biomarker discovery, or drug mechanisms. Quantitative methods can be employed to measure relative differences in protein levels across the samples and can be label-free or involve isotopic labeling (metabolic, chemical, or enzymatic). Stable isotope labeling methods have grown in popularity because they allow many samples to be analyzed simultaneously and are suitable for samples from different cells, tissues, bodily fluids, or whole organisms. Isotope labeling methods1,2,3,4,5,6,7 increase experimental throughput, while reducing acquisition time, costs, and experimental error. These methods use precursor mass spectra to measure relative abundances of proteins from peptide peaks. In contrast, isobaric tagging reagents8,9,10 generate reporter ions that are either detected in MS/MS or MS3 11 spectra and these peaks are used to report on relative abundances of proteins.
The current state-of-the-art in proteomics multiplexing is either a 10-plex12 or 12-plex isobaric tag analysis13. Enhanced sample multiplexing (i.e. &#62;10 samples) methods have been developed by our laboratory for tissues14,15,16,17, and by others for the analysis of cells18,19,20, tissues 21, or targeted peptides22. We developed an enhanced multiplexing technique called combined precursor isotopic labeling with isobaric tagging (cPILOT). Global cPILOT is useful for getting information about the relative concentrations of all proteins across different sample conditions (&#8805;12)14. Figure 1 shows a general cPILOT workflow. Tryptic or Lys-C peptides are selectively labeled at the N-terminus with dimethylation using low pH2 and at lysine residues with 6-plex reagents using high pH. This strategy doubles the number of samples that can be analyzed with isobaric reagents which helps to reduce experimental costs and additionally, reduces experimental steps and time.
cPILOT is flexible as we have developed other methods to study oxidative post-translational modifications, including 3-nitrotyrosine-modified proteins14 and cysteine containing peptides with S-nitrosylation (oxcyscPILOT)23. We have also developed an amino acid selective approach, cysteine cPILOT (cyscPILOT)17. MS3 acquisition with a top-ion11 or selective-y1-ion method15 can help reduce reporter ion interference and improve quantitative accuracy of cPILOT. The use of MS3 in the acquisition method requires a high-resolution instrument with an orbitrap mass analyzer although low resolution ion trap instruments may also work24.
Previously, cPILOT has been used to study liver proteins16 from an Alzheimer&#39;s disease mouse model. Here, we describe how to perform global cPILOT analysis using brain, heart, and liver homogenates to study the role of the periphery in Alzheimer&#39;s disease. This experiment incorporates biological replication. Because of the versatility of cPILOT, interested users can use the technique to study other tissues for a range of biological problems and systems.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Water - MS Grade</td>
			<td>Fisher Scientific</td>
			<td>W6-4</td>
			<td>4 L quantity is not necessary</td>
		</tr>
		<tr>
			<td>Acetonitrile - MS Grade</td>
			<td>Fisher Scientific</td>
			<td>A955-4</td>
			<td>4 L quantity is not necessary</td>
		</tr>
		<tr>
			<td>Acetic Acid</td>
			<td>J.T. Baker</td>
			<td>9508-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium hydroxide solution (28 - 30%)</td>
			<td>Sigma Aldrich</td>
			<td>320145-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium formate</td>
			<td>Acros Organics</td>
			<td>208-753-9</td>
			<td></td>
		</tr>
		<tr>
			<td>Formic Acid</td>
			<td>Fluka Analytical</td>
			<td>94318-250ML-F</td>
			<td></td>
		</tr>
		<tr>
			<td>BCA protein assay kit</td>
			<td>Pierce Thermo Fisher Scientific</td>
			<td>23227</td>
			<td></td>
		</tr>
		<tr>
			<td>Urea</td>
			<td>Biorad</td>
			<td>161-0731</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris</td>
			<td>Biorad</td>
			<td>161-0716</td>
			<td></td>
		</tr>
		<tr>
			<td>Dithiothreiotol (DTT)</td>
			<td>Fisher Scientific</td>
			<td>BP172-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Iodoacetamide (IAM)</td>
			<td>Acros Organics</td>
			<td>144-48-9</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Cysteine</td>
			<td>Sigma Aldrich, Chemistry</td>
			<td>168149-25G</td>
			<td></td>
		</tr>
		<tr>
			<td>L-1-tosylamido-2 phenylethyl cholormethyl ketone (TPCK)-treated Trypsin from bovine pancreas</td>
			<td>Sigma Aldrich, Life Science</td>
			<td>T1426-100MG</td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde (CH2O) solution; 36.5 - 38% in H2O</td>
			<td>Sigma Aldrich, Life Science</td>
			<td>F8775-25ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde (13CD2O) solution; 20 wt % in D2O, 98 atom % D, 99 atom % 13 C</td>
			<td>Sigma Aldrich, Chemistry</td>
			<td>596388-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Cyanoborohydride; reagent grade, 95%</td>
			<td>Sigma Aldrich</td>
			<td>156159-10G</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Cyanoborodeuteride; 96 atom % D, 98% CP</td>
			<td>Sigma Aldrich, Chemistry</td>
			<td>190020-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Strong Cation Exchange (SCX) spin tips sample prep kit</td>
			<td>Protea BioSciences</td>
			<td>SP-155-24kit</td>
			<td></td>
		</tr>
		<tr>
			<td>Triethyl ammonium bicarbonate (TEAB) buffer</td>
			<td>Sigma Aldrich, Life Science</td>
			<td>T7408-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Isobaric Tagging Kit (TMT 6 plex) - 6 reactions (1 x 0.8 mg)&#160;</td>
			<td>Thermo Fisher Scientific</td>
			<td>90061</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydroxylamine hydrochloride</td>
			<td>Sigma Aldrich, Chemistry</td>
			<td>255580-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Standard vortex mixer</td>
			<td>Fisher Scientific</td>
			<td>2215365</td>
			<td>any mixer can be used</td>
		</tr>
		<tr>
			<td>Oasis HLB 1cc (10 mg) &#160;&#160;extraction cartridges</td>
			<td>Waters</td>
			<td>186000383</td>
			<td>These are C18 cartridges</td>
		</tr>
		<tr>
			<td>Visiprep SPE vacuum manifold, DL (disposable liner), 24 port model</td>
			<td>Sigma Aldrich</td>
			<td>57265</td>
			<td>A 12 port model is also sufficient</td>
		</tr>
		<tr>
			<td>Speed-vac</td>
			<td>Thermo Scientific</td>
			<td>SPD1010</td>
			<td>any brand of speed vac is sufficient</td>
		</tr>
		<tr>
			<td>Water bath chamber</td>
			<td>Thermo Scientific</td>
			<td>2825/2826</td>
			<td>Any brand of&#160; a water bath chamber with controlled temperatures is sufficient.</td>
		</tr>
		<tr>
			<td>Mechanical Homogenizer (i.e. FastPrep-24 5G)</td>
			<td>MP Biomedicals</td>
			<td>116005500</td>
			<td></td>
		</tr>
		<tr>
			<td>Eksigent Nano LC - Ultra 2D with Nano LC AS-2 autosampler</td>
			<td>Sciex</td>
			<td>-</td>
			<td>This model is no longer available. Any nano LC with an autosampler is sufficient.</td>
		</tr>
		<tr>
			<td>LTQ Orbitrap Velos Mass Spectrometer</td>
			<td>Thermo Scientific</td>
			<td>-</td>
			<td>This model is no longer available. Other high resolution instruments (e.g. Orbitrap Elite, Orbitrap Fusion, or Orbitrap Fusion Lumos) can be used.</td>
		</tr>
		<tr>
			<td>Protein software (e.g. Proteome Discoverer)</td>
			<td>Thermo Scientific</td>
			<td>IQLAAEGABSFAKJMAUH&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Analytical balance</td>
			<td>Mettler Toledo</td>
			<td>AL54</td>
			<td></td>
		</tr>
		<tr>
			<td>Stir plate</td>
			<td>VWR</td>
			<td>12365-382</td>
			<td>Any brand of stir plates are sufficient.</td>
		</tr>
		<tr>
			<td>pH meter (Tris compatiable)</td>
			<td>&#160;Fisher Scientific (Accumet)</td>
			<td>13-620-183</td>
			<td>Any brand of a ph meter is sufficient</td>
		</tr>
		<tr>
			<td>pH 10 buffer</td>
			<td>Fisher Scientific</td>
			<td>06-664-261</td>
			<td>Any brand of ph buffer 10 is sufficient</td>
		</tr>
		<tr>
			<td>pH 7 buffer</td>
			<td>Fisher Scientific</td>
			<td>06-664-260</td>
			<td>Any brand ph buffer 7&#160; is sufficient</td>
		</tr>
		<tr>
			<td>1.5 mL eppendorf tubes, 500pk</td>
			<td>Fisher Scientific</td>
			<td>05-408-129</td>
			<td>Any brand of 1.5 mL eppendorf tubes are sufficient</td>
		</tr>
		<tr>
			<td>0.6 mL eppendorf tubes, 500pk</td>
			<td>Fisher Scientific</td>
			<td>04-408-120</td>
			<td>Any brand of 0.6 mL eppendorf tubes are sufficient</td>
		</tr>
		<tr>
			<td>0.65&#181;m Ultrafree MC DV centrifugal filter units</td>
			<td>EMD Millipore</td>
			<td>UFC30DV00</td>
			<td></td>
		</tr>
		<tr>
			<td>2 mL microcentrifuge tubes, 72 units</td>
			<td>Thermo Scientific</td>
			<td>69720</td>
			<td></td>
		</tr>
		<tr>
			<td>C18 packing material (5 &#181;m, 100 &#197;)</td>
			<td>Bruker</td>
			<td>PM5/61100/000</td>
			<td>This item is no longer available from Bruker. Alternative packing material with listed specifications will be sufficient.</td>
		</tr>
		<tr>
			<td>C18 packing material (5 &#181;m, 200 &#197;)</td>
			<td>Bruker</td>
			<td>PM5/61200/000</td>
			<td>This item is no longer available from Bruker. Alternative packing material with listed specifications will be sufficient.</td>
		</tr>
	</tbody>
</table>

enhanced sample multiplexing of tissues using combined precursor isotopic labeling and isobaric tagging (cpilot)

There is an increasing demand to analyze many biological samples for disease understanding and biomarker discovery. Quantitative proteomics strategies that allow simultaneous measurement of multiple samples have become widespread and greatly reduce experimental costs and times. Our laboratory developed a technique called combined precursor isotopic labeling and isobaric tagging (cPILOT), which enhances sample multiplexing of traditional isotopic labeling or isobaric tagging approaches. Global cPILOT can be applied to samples originating from cells, tissues, bodily fluids, or whole organisms and gives information on relative protein abundances across different sample conditions. cPILOT works by 1) using low pH buffer conditions to selectively dimethylate peptide N-termini and 2) using high pH buffer conditions to label primary amines of lysine residues with commercially-available isobaric reagents (see Table of Materials/Reagents). The degree of sample multiplexing available is dependent on the number of precursor labels used and the isobaric tagging reagent. Here, we present a 12-plex analysis using light and heavy dimethylation combined with six-plex isobaric reagents to analyze 12 samples from mouse tissues in a single analysis. Enhanced multiplexing is helpful for reducing experimental time and cost and more importantly, allowing comparison across many sample conditions (biological replicates, disease stage, drug treatments, genotypes, or longitudinal time-points) with less experimental bias and error. In this work, the global cPILOT approach is used to analyze brain, heart, and liver tissues across biological replicates from an Alzheimer&#39;s disease mouse model and wild-type controls. Global cPILOT can be applied to study other biological processes and adapted to increase sample multiplexing to greater than 20 samples.

cPILOT uses amine-based chemistry to chemically label peptides at the N-terminus and lysine residues and enhances sample multiplexing capabilities. Figure 2 shows representative MS data that is obtained from a 12-plex cPILOT analysis of brain, heart, and liver tissues from an Alzheimer&#39;s disease mouse model and wild-type controls. As shown in Table 1, two biological replicates for the Alzheimer&#39;s disease and wild-type mice are included in this 12-...

Watch this Scientific Journal Video about Enhanced Sample Multiplexing of Tissues Using Combined Precursor Isotopic Labeling and Isobaric Tagging cPILOT at JoVE.com

Enhanced Sample Multiplexing of Tissues Using Combined Precursor Isotopic Labeling and Isobaric Tagging cPILOT

Combined precursor isotopic labeling and isobaric tagging (cPILOT) is a quantitative proteomics strategy that enhances sample multiplexing capabilities of isobaric tags. This protocol describes the application of cPILOT to tissues from an Alzheimer's disease mouse model and wild-type controls.

Enhanced Sample Multiplexing of Tissues Using Combined Precursor Isotopic Labeling and Isobaric Tagging (cPILOT)

There is an increasing demand to analyze many biological samples for disease understanding and biomarker discovery. Quantitative proteomics strategies ...

The overall goal of this enhanced multiplex method is to increase the number of protein samples that can be analyzed simultaneously while decreasing sample error and instrument time. This method can help answer key questions in the fields of aging, neurodegenerative disease, other age-related diseases, and cancer that are related to pathogenesis, progression, diagnosis, prognosis, and therapeutic targets. The main advantage of this technique is that a comprehensive snapshot of protein changes across many conditions can be generated.Though this method can provide insight into Alzheimer disease in mouse model, it can also be applied to tissue samples from patient with Alzheimer or a range of other disorders. Generally, individuals new to this method will find it challenging because there are several samples to handle simultaneously in a short time frame. We first had the idea for this method when we recognized that acetylation could be combined with isoberic tagging for protein nitration which motivated us to make the technique work globally for all peptides.This study will analyze brain, heart, and liver tissues from an Alzheimer's disease mouse model and wild type controls. Transfer 60 to 90 milligrams of each tissue sample to a lysing tube, and add 500 microliters of PBS with eight molar urea. Homogenize the samples using a mechanical homogenizer.Remove the tissue homogenate from the lysing tube and transfer to a microcentrifuge tube. Rinse the lysing tube with 100 to 500 microliters of PBS with eight molar urea and combine the rinse solution with the tissue homogenate. Centrifuge the tissue homogenate for 15 minutes.Clutch the supernatant from each sample. After the performing the BCA assay to determine protein concentration, add 100 micrograms of protein from each sample to individually labeled microcentrifuge tubes. Add dithiothreitol to each sample.And incubate at 37 degrees Celsius for two hours. Add iodoacetamide, IAM, to each sample, and incubate on ice in the dark for two hours. Next, add L-cysteine to each sample, and incubate at room temperature for 30 minutes.After 30 minutes, add tris buffer with calcium chloride to dilute urea to a final concentration of two molar. Add L1 tosilimitotophenylethylcholer methyl ketone-treated trypsin to each sample. And incubate at 37 degrees Celsius for 24 hours.On the following day, quench the protein digestion by flash freezing the sample in liquid nitrogen and store at negative 80 degree Celsius until further processing. Prior to dimethylation labeling, the peptide samples are desalted, as described in the text protocol, and dried by vacuum centrifugation. To begin the dimethylation labeling procedure, reconstitute the peptides in 1%acetic acid dissolved in HPLC or nanopure grade water.Remove a 50 microgram portion of each sample to a new 1.5 milliliter microcentrifuge tube. Store the remainder of the reconstituted peptides at negative 80 degree Celsius for future experiments. In the steps that will be demonstrated next, it is critical to add reagents quickly so the chemical enabling reactions will take place for the same amount of time for all of the samples.Add eight microliters of a 60 millimolar formaldehyde solution to the samples for labeling with light dimethylation. Add eight microliters of a 60 millimolar carbon 13 deuterium labeled formaldehyde solution to the samples for labeling with heavy dimethylation. Add eight microliters of 24 millimolar sodium cyanoborohydride to the samples labeled with light dimethylation.Add eight mircoliters of 24 millimolar sodium cyanoboroduderide to the samples labeled with heavy dimethylation. Vortex the samples, and then shake gently on a tube shaker for about 10 minutes at room temperature. Quench the reactions by adding 16 microliters of 1%ammonia for five minutes.Reacidify the reaction mixtures by adding eight microliters of 5%formic acid. Combine the light and heavy dimethylated peptides to generate a total of six samples. Perform sample desalting as described in the text protocol.And dry the samples by vacuum centrifugation. To being isobaric tagging of the dimethylated samples, first, reconstitute 100 micrograms of dimethylated peptides and triethylammonium bicarbonate, or TEAB buffer. Next, prepare isobaric reagents according to the manufacturer's protocol of the isobaric tagging kit.Add the appropriate volume, in this case, 41 microliters of the solubilized isobaric tagging reagent to each of the peptide samples, and vortex for about 10 seconds. Shake the samples on a microcentrifuge tube shaker for about one hour at room temperature. To quench the reactions, add 8 microliters of hydroxylamine to each sample.And incubate the samples for 15 minutes at room temperature. Pool the six labeled samples into a single mixture and desalt. Prepare the peptides for liquid chromatogrophy by reconstituting the peptides in mass spectrometry grade water with 0.1%formic acid.Add reconstituted peptides to a microcentrifuge tube containing a 0.65 micrometer filter. And centrifuge at 12, 000 times g for one minute. Remove and discard the filter.Transfer filtered peptides into an autosampler vial. Inject six microliters of each strong cation exchange faction sample onto a trap column. Pack to two centimeters with carbon 18 material.Run the analytical separation and data acquisition mass spectrometer methods. A 12-plex cPilot analysis of brain, heart, and liver tissues from an Alzheimer's disease mouse model and wild type controls was performed. Precursor data showed light and heavy dimethylated peptides represented by the peaks at m/z 643.854 and 647.875.These peptides were selected, independently isolated, and fragmented with collusion induced dissociation to generate these spectra. Search results indicated that the peaks belonged to a peptide of the protein phosphoglycerate kinase one. These peaks were isolated further for higher energy collusional dissociation tandem mass spectrometry and the reporter ions are observed as shown.Both sets of triple stage mass spectrometry spectra are necessary to get information about the 12 samples. In this example, the Alzheimer's disease to wild type control ion ratios are similar across the two biological replicates for brain, liver, and heart tissues. The fold change values for each comparison suggest that phosphoglyerate kinase one levels in the brain and heart are higher in Alzheimer's disease mice but lower in the liver.Once mastered, this technique can be done in approximately five hours if it is performed properly. While attempting this procedure, it's important to remember to be careful of sample handling. Incorporated into this procedure, separation methods like strong cation exchange or high pH fractionation can be performed in order to increase per diem depth and coverage.After watching this video, you should have a good understanding of how to enhance sample multiplexing using C-Pilot.

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6.8K vistas.  University of Pittsburgh. The overall goal of this enhanced multiplex method is to increase the number of protein samples that can be analyzed simultaneously while decreasing sample error and instrument time. This method can help answer key questions in the fields of aging, neurodegenerative disease, other age-related diseases, and cancer that are related to pathogenesis, progression, diagnosis, prognosis, and therapeutic targets. The main advantage of this technique is that a comprehensive snapshot of protein changes...