Name: enhanced sample multiplexing of tissues using combined precursor isotopic labeling and isobaric tagging (cpilot)
Uploaded: 2017-05-01T10:30:00
Description: Watch this Scientific Journal Video about Enhanced Sample Multiplexing of Tissues Using Combined Precursor Isotopic Labeling and Isobaric Tagging cPILOT at JoVE.com

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>

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.

enhanced-sample-multiplexing-tissues-using-combined-precursor

Research

JoVE Journal

Biochemistry

Horizontal Gel Electrophoresis for Enhanced Detection of Protein-RNA Complexes

Native polyacrylamide gel electrophoresis is a fundamental tool of molecular biology that has been used extensively for the biochemical analysis of RNA-protein interactions. These interactions have been traditionally analyzed with polyacrylamide gels generated between two glass plates and samples electrophoresed vertically. However, polyacrylamide gels cast in trays and electrophoresed horizontally offers several advantages. For example, horizontal gels used to analyze complexes between fluorescent RNA substrates and specific proteins can be imaged multiple times as electrophoresis progresses. This provides the unique opportunity to monitor RNA-protein complexes at several points during the experiment. In addition, horizontal gel electrophoresis makes it possible to analyze many samples in parallel. This can greatly facilitate time course experiments as well as analyzing multiple reactions simultaneously to compare different components and conditions. Here we provide a detailed protocol for generating and using horizontal native gel electrophoresis for analyzing RNA-Protein interactions.

Native polyacrylamide gel electrophoresis is a fundamental tool for analyzing RNA-protein interactions. Traditionally most experiments have used vertical gels. However, horizontal gels provide several advantages, such as the opportunity to monitor complexes during electrophoresis. We provide a detailed protocol for generating and using horizontal native gel electrophoresis.

Native polyacrylamide gel electrophoresis is a fundamental tool of molecular biology that has been used extensively for the biochemical analysis of ...

Deep Proteome Profiling by Isobaric Labeling, Extensive Liquid Chromatography, Mass Spectrometry, and Software-assisted Quantification

Many exceptional advances have been made in mass spectrometry (MS)-based proteomics, with particular technical progress in liquid chromatography (LC) coupled to tandem mass spectrometry (LC-MS/MS) and isobaric labeling multiplexing capacity. Here, we introduce a deep-proteomics profiling protocol that combines 10-plex tandem mass tag (TMT) labeling with an extensive LC/LC-MS/MS platform, and post-MS computational interference correction to accurately quantitate whole proteomes. This protocol includes the following main steps: protein extraction and digestion, TMT labeling, 2-dimensional (2D) LC, high-resolution mass spectrometry, and computational data processing. Quality control steps are included for troubleshooting and evaluating experimental variation. More than 10,000 proteins in mammalian samples can be confidently quantitated with this protocol. This protocol can also be applied to the quantitation of post translational modifications with minor changes. This multiplexed, robust method provides a powerful tool for proteomic analysis in a variety of complex samples, including cell culture, animal tissues, and human clinical specimens.

We present a protocol to accurately quantitate proteins with isobaric labelling, extensive fractionation, bioinformatics tools, and quality control steps in combination with liquid chromatography interfaced to a high-resolution mass spectrometer.

Many exceptional advances have been made in mass spectrometry (MS)-based proteomics, with particular technical progress in liquid chromatography (LC) ...

Isolation of Glomeruli and In Vivo Labeling of Glomerular Cell Surface Proteins

Proteinuria results from the disruption of the glomerular filter that is composed of the fenestrated endothelium, glomerular basement membrane, and podocytes with their slit diaphragms. The delicate structure of the glomerular filter, especially the slit diaphragm, relies on the interplay of diverse cell surface proteins. Studying these cell surface proteins has so far been limited to in vitro studies or histologic analysis. Here, we present a murine in vivo biotinylation labeling method, which enables the study of glomerular cell surface proteins under physiologic and pathophysiologic conditions. This protocol contains information on how to perfuse mouse kidneys, isolate glomeruli, and perform endogenous immunoprecipitation of a protein of interest. Semi-quantitation of glomerular cell surface abundance is readily available with this novel method, and all proteins accessible to biotin perfusion and immunoprecipitation can be studied. In addition, isolation of glomeruli with or without biotinylation enables further analysis of glomerular RNA and protein as well as primary glomerular cell culture (i.e., primary podocyte cell culture).

Isolation of Glomeruli and In Vivo Labeling of Glomerular Cell Surface Proteins

Here we present a protocol for murine in vivo labeling of glomerular cell surface proteins with biotin. This protocol contains information on how to perfuse mouse kidneys, isolate glomeruli, and perform endogenous immunoprecipitation of the protein of interest.

Proteinuria results from the disruption of the glomerular filter that is composed of the fenestrated endothelium, glomerular basement membrane, and ...

Proteome-wide Quantification of Labeling Homogeneity at the Single Molecule Level

Cell proteomes are often characterized using electrophoresis assays, where all species of proteins in the cells are non-specifically labeled with a fluorescent dye and are spotted by a photodetector following their separation. Single molecule fluorescence imaging can provide ultrasensitive protein detection with its ability for visualizing individual fluorescent molecules. However, the application of this powerful imaging method to electrophoresis assays is hampered by the lack of ways to characterize the homogeneity of fluorescent labeling of each protein species across the proteome. Here, we developed a method to evaluate the labeling homogeneity across the proteome based on a single molecule fluorescence imaging assay. In our measurement using a HeLa cell sample, the proportion of proteins labeled with at least one dye, which we termed &#8216;labeling occupancy&#8217; (LO), was determined to range from 50% to 90%, supporting the high potential of the application of single molecule imaging to sensitive and precise proteome analysis.

Here, we present a protocol to assess the labeling homogeneity for each protein species in a complex protein sample at the single molecule level.

Cell proteomes are often characterized using electrophoresis assays, where all species of proteins in the cells are non-specifically labeled with a ...

Robust Comparison of Protein Levels Across Tissues and Throughout Development Using Standardized Quantitative Western Blotting

Western blotting is a technique that is commonly used to detect and quantify protein expression. Over the years, this technique has led to many advances in both basic and clinical research. However, as with many similar experimental techniques, the outcome of Western blot analyses is easily influenced by choices made in the design and execution of the experiment. Specific housekeeping proteins have traditionally been used to normalize protein levels for quantification, however, these have a number of limitations and have therefore been increasingly criticized over the past few years. Here, we describe a detailed protocol that we have developed to allow us to undertake complex comparisons of protein expression variation across different tissues, mouse models (including disease models), and developmental timepoints. By using a fluorescent total protein stain and introducing the use of an internal loading standard, it is possible to overcome existing limitations in the number of samples that can be compared within experiments and systematically compare protein levels across a range of experimental conditions. This approach expands the use of traditional western blot techniques, thereby allowing researchers to better explore protein expression across different tissues and samples.

This method describes a robust and reproducible approach for the comparison of protein levels in different tissues and at different developmental timepoints using a standardized quantitative western blotting approach.

Western blotting is a technique that is commonly used to detect and quantify protein expression. Over the years, this technique has led to many advances ...

An All-in-one Sample Holder for Macromolecular X-ray Crystallography with Minimal Background Scattering

Macromolecular X-ray crystallography (MX) is the most prominent method to obtain high-resolution three-dimensional knowledge of biological macromolecules. A prerequisite for the method is that highly ordered crystalline specimen need to be grown from the macromolecule to be studied, which then need to be prepared for the diffraction experiment. This preparation procedure typically involves removal of the crystal from the solution, in which it was grown, soaking of the crystal in ligand solution or cryo-protectant solution and then immobilizing the crystal on a mount suitable for the experiment. A serious problem for this procedure is that macromolecular crystals are often mechanically unstable and rather fragile. Consequently, the handling of such fragile crystals can easily become a bottleneck in a structure determination attempt. Any mechanical force applied to such delicate crystals may disturb the regular packing of the molecules and may lead to a loss of diffraction power of the crystals. Here, we present a novel all-in-one sample holder, which has been developed in order to minimize the handling steps of crystals and hence to maximize the success rate of the structure determination experiment. The sample holder supports the setup of crystal drops by replacing the commonly used microscope cover slips. Further, it allows in-place crystal manipulation such as ligand soaking, cryo-protection and complex formation without any opening of the crystallization cavity and without crystal handling. Finally, the sample holder has been designed in order to enable the collection of in situ X-ray diffraction data at both, ambient and cryogenic temperature. By using this sample holder, the chances to damage the crystal on its way from crystallization to diffraction data collection are considerably reduced since direct crystal handling is no longer required.

A novel sample holder for macromolecular X-ray crystallography along with a suitable handling protocol is presented. The system allows crystal growth, crystal soaking and in situ diffraction data collection at both, ambient and cryogenic temperature without the need of any crystal manipulation or mounting.

Macromolecular X-ray crystallography (MX) is the most prominent method to obtain high-resolution three-dimensional knowledge of biological macromolecules. ...

A Plasma Sample Preparation for Mass Spectrometry using an Automated Workstation

Sample preparation for mass spectrometry analysis in proteomics requires enzymatic cleavage of proteins into a peptide mixture. This process involves numerous incubation and liquid transfer steps in order to achieve denaturation, reduction, alkylation, and cleavage. Adapting this workflow onto an automated workstation can increase efficiency and reduce coefficients of variance, thereby providing more reliable data for statistical comparisons between sample types. We previously described an automated proteomic sample preparation workflow1. Here, we report the development of a more efficient and better controlled workflow with the following advantages: 1) The number of liquid transfer steps is reduced from nine to six by combining reagents; 2) Pipetting time is reduced by selective tip pipetting using a 96-position pipetting head with multiple channels; 3) Potential throughput is increased by the availability of up to 45 deck positions; 4) Complete enclosure of the system provides improved temperature and environmental control and reduces the potential for contamination of samples or reagents; and 5) The addition of stable isotope labeled peptides, as well as &#946;-galactosidase protein, to each sample makes monitoring and quality control possible throughout the entire process. These hardware and process improvements provide good reproducibility and improve intra-assay and inter-assay precision (CV of less than 20%) for LC-MS based protein and peptide quantification. The entire workflow for digesting 96 samples in a 96-well plate can be completed in approximately 5 hours.

Here, we present an automated plasma protein digestion method for mass spectrometry-based quantitative proteomic analysis. In this protocol, the liquid transferring and incubation steps for protein denaturation, reduction, alkylation, and trypsin digestion reactions are streamlined and automated. It takes approximately five hours to prepare a 96-well plate with desired precision.

Sample preparation for mass spectrometry analysis in proteomics requires enzymatic cleavage of proteins into a peptide mixture. This process involves ...

Quantification of Coenzyme A in Cells and Tissues

Emerging research has revealed that the cellular coenzyme A (CoA) supply can become limiting with a detrimental impact on growth, metabolism and survival. Measurement of cellular CoA is a challenge due to its relatively low abundance and the dynamic conversion of free CoA to CoA thioesters that, in turn, participate in numerous metabolic reactions. A method is described that navigates through potential pitfalls during sample preparation to yield an assay with a broad linear range of detection that is suitable for use in many biomedical laboratories.

This method describes sample preparation from cultured cells and animal tissues, extraction and derivatization of coenzyme A in the samples, followed by high pressure liquid chromatography for purification and quantification of the derivatized coenzyme A by absorbance or fluorescence detection.

Emerging research has revealed that the cellular coenzyme A (CoA) supply can become limiting with a detrimental impact on growth, metabolism and survival. ...

Enrichment of Mammalian Tissues and Xenopus Oocytes with Cholesterol

Cholesterol enrichment of mammalian tissues and cells, including Xenopus oocytes used for studying cell function, can be accomplished using a variety of methods. Here, we describe two important approaches used for this purpose. First, we describe how to enrich tissues and cells with cholesterol using cyclodextrin saturated with cholesterol using cerebral arteries (tissues) and hippocampal neurons (cells) as examples. This approach can be used for any type of tissue, cells, or cell lines. An alternative approach for cholesterol enrichment involves the use of low-density lipoprotein (LDL). The advantage of this approach is that it uses part of the natural cholesterol homeostasis machinery of the cell. However, whereas the cyclodextrin approach can be applied to enrich any cell type of interest with cholesterol, the LDL approach is limited to cells that express LDL receptors (e.g., liver cells, bone marrow-derived cells such as blood leukocytes and tissue macrophages), and the level of enrichment depends on the concentration and the mobility of the LDL receptor. Furthermore, LDL particles include other lipids, so cholesterol delivery is nonspecific. Second, we describe how to enrich Xenopus oocytes with cholesterol using a phospholipid-based dispersion (i.e., liposomes) that includes cholesterol. Xenopus oocytes constitute a popular heterologous expression system used for studying cell and protein function. For both the cyclodextrin-based cholesterol enrichment approach of mammalian tissue (cerebral arteries) and for the phospholipid-based cholesterol enrichment approach of Xenopus oocytes, we demonstrate that cholesterol levels reach a maximum following 5 min of incubation. This level of cholesterol remains constant during extended periods of incubation (e.g., 60 min). Together, these data provide the basis for optimized temporal conditions for cholesterol enrichment of tissues, cells, and Xenopus oocytes for functional studies aimed at interrogating the impact of cholesterol enrichment.

Enrichment of Mammalian Tissues and Xenopus Oocytes with Cholesterol

Two methods of cholesterol enrichment are presented: the application of cyclodextrin saturated with cholesterol to enrich mammalian tissues and cells, and the use of cholesterol-enriched phospholipid-based dispersions (liposomes) to enrich Xenopus oocytes. These methods are instrumental for determining the impact of elevated cholesterol levels in molecular, cellular, and organ function.

Cholesterol enrichment of mammalian tissues and cells, including Xenopus oocytes used for studying cell function, can be accomplished using a variety of ...

Preparation of Sample Support Films in Transmission Electron Microscopy using a Support Floatation Block

Structure determination by cryo-electron microscopy (cryo-EM) has rapidly grown in the last decade; however, sample preparation remains a significant bottleneck. Macromolecular samples are ideally imaged directly from random orientations in a thin layer of vitreous ice. However, many samples are refractory to this, and protein denaturation at the air-water interface is a common problem. To overcome such issues, support films-including amorphous carbon, graphene, and graphene oxide-can be applied to the grid to provide a surface which samples can populate, reducing the probability of particles experiencing the deleterious effects of the air-water interface. The application of these delicate supports to grids, however, requires careful handling to prevent breakage, airborne contamination, or extensive washing and cleaning steps. A recent report describes the development of an easy-to-use floatation block that facilitates wetted transfer of support films directly to the sample. Use of the block minimizes the number of manual handling steps required, preserving the physical integrity of the support film, and the time over which hydrophobic contamination can accrue, ensuring that a thin film of ice can still be generated. This paper provides step-by-step protocols for the preparation of carbon, graphene, and graphene oxide supports for EM studies.

Sample preparation for cryo-electron microscopy (cryo-EM) is a significant bottleneck in the structure determination workflow of this method. Here, we provide detailed methods for using an easy-to-use, three-dimensionally printed block for the preparation of support films to stabilize samples for transmission EM studies.

Structure determination by cryo-electron microscopy (cryo-EM) has rapidly grown in the last decade; however, sample preparation remains a significant ...