This work was supported in part by NIH awards F32-HL149191 to YH; R00-HL144829 to EL; R21-HL150456, R00-HL127302, R01-HL141278 to MPL. Figure&#160;1, Figure 2, Figure 3 are created with the aid of a web-based science illustration tool, BioRender.com.

<ol>
	<li>Geyer, P. 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=Revisiting+biomarker+discovery+by+plasma+proteomics.">Revisiting biomarker discovery by plasma proteomics.</a> Molecular Systems Biology. 13 (9), 942 (2017).</li><li>Coscia, F., 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=A+streamlined+mass+spectrometry-based+proteomics+workflow+for+large-scale+FFPE+tissue+analysis.">A streamlined mass spectrometry-based proteomics workflow for large-scale FFPE tissue analysis.</a> The Journal of Pathology. 251 (1), 100-112 (2020).</li><li>Yeung, Y. -. G., Neives, E., Angeletti, R., Stanley, E. 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=Removal+of+detergents+from+protein+digests+for+mass+spectrometry+analysis.">Removal of detergents from protein digests for mass spectrometry analysis.</a> Analytical Biochemistry. 382 (2), 135-137 (2008).</li><li>Addona, T. 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=Multi-site+assessment+of+the+precision+and+reproducibility+of+multiple+reaction+monitoring-based+measurements+of+proteins+in+plasma.">Multi-site assessment of the precision and reproducibility of multiple reaction monitoring-based measurements of proteins in plasma.</a> Nature Biotechnology. 27 (7), 633-641 (2009).</li><li>Lowenthal, M. S., Liang, Y., Phinney, K. W., Stein, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+bottom-up+proteomics+depends+on+digestion+conditions.">Quantitative bottom-up proteomics depends on digestion conditions.</a> Analytical Chemistry. 86 (1), 551-558 (2014).</li><li>Elliott, K. C., Resnik, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scientific+reproducibility,+human+error,+and+public+policy.">Scientific reproducibility, human error, and public policy.</a> Bioscience. 65 (1), 5-6 (2015).</li><li>Brown, A. W., Kaiser, K. A., Allison, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Issues+with+data+and+analyses:+Errors,+underlying+themes,+and+potential+solutions.">Issues with data and analyses: Errors, underlying themes, and potential solutions.</a> Proceedings of the National Academy of Sciences of the United States of America. 115 (11), 2563-2570 (2018).</li><li>van den Broek, I., 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=Automated+multiplex+LC-MS/MS+assay+for+quantifying+serum+apolipoproteins+A-I,+B,+C-I,+C-II,+C-III,+and+E+with+qualitative+apolipoprotein+E+phenotypic.">Automated multiplex LC-MS/MS assay for quantifying serum apolipoproteins A-I, B, C-I, C-II, C-III, and E with qualitative apolipoprotein E phenotypic.</a> Clinical Chemistry. 62 (1), 188-197 (2016).</li><li>M&#252;ller, T., 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=Automated+sample+preparation+with+SP3+for+low-input+clinical+proteomics.">Automated sample preparation with SP3 for low-input clinical proteomics.</a> Molecular Systems Biology. 16 (1), 9111 (2020).</li><li>Fu, Q., 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=Highly+reproducible+automated+proteomics+sample+preparation+workflow+for+quantitative+mass+spectrometry.">Highly reproducible automated proteomics sample preparation workflow for quantitative mass spectrometry.</a> Journal of Proteome Research. 17 (1), 420-428 (2018).</li><li>Liu, X., Gygi, S. P., Paulo, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+semiautomated+paramagnetic+bead-based+platform+for+isobaric+tag+sample+preparation.">A semiautomated paramagnetic bead-based platform for isobaric tag sample preparation.</a> Journal of the American Society for Mass Spectrometry. 32 (6), 1519-1529 (2021).</li><li>Poulsen, K. M., Pho, T., Champion, J. A., Payne, C. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automation+and+low-cost+proteomics+for+characterization+of+the+protein+corona:+experimental+methods+for+big+data.">Automation and low-cost proteomics for characterization of the protein corona: experimental methods for big data.</a> Analytical and Bioanalytical Chemistry. 412 (24), 6543-6551 (2020).</li><li>Liang, Y., 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=Fully+automated+sample+processing+and+analysis+workflow+for+low-input+proteome+profiling.">Fully automated sample processing and analysis workflow for low-input proteome profiling.</a> Analytical Chemistry. 93 (3), 1658-1666 (2021).</li><li>. Web URL Available from: <a target="_blank" href="https://opentrons.com/ot-app/">https://opentrons.com/ot-app/</a> (2021)</li><li>. Web URL Available from: <a target="_blank" href="https://docs.opentrons.com/v2/">https://docs.opentrons.com/v2/</a> (2021)</li><li>. Web URL Available from: <a target="_blank" href="https://www.cytivalifesciences.com/en/us/solutions/genomics/knowledge-center/cleanup-for-mass-spectrometry">https://www.cytivalifesciences.com/en/us/solutions/genomics/knowledge-center/cleanup-for-mass-spectrometry</a> (2021)</li><li>. Web URL Available from: <a target="_blank" href="https://www.thermofisher.com/order/catalog/product/23275#/23275">https://www.thermofisher.com/order/catalog/product/23275#/23275</a> (2021)</li><li>Han, Y., Wright, J. M., Lau, E., Lam, M. P. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determining+alternative+protein+isoform+expression+using+RNA+sequencing+and+mass+spectrometry.">Determining alternative protein isoform expression using RNA sequencing and mass spectrometry.</a> STAR Protocols. 1 (3), 100138 (2020).</li></ol>

The authors have no conflicts to declare.

Critical steps within the protocol 
For the best performance, Opentrons-verified labware, modules, and consumables&#160;compatible with OT-2 should be used. Custom labware can be created following Opentrons&#39; instruction at Reference14. Make sure to calibrate the OT-2 deck, pipettes, and labware when used for the first time. It is also critical to follow guidelines from SP3 beads&#39; manufacturer to prepare beads for peptide and protein clean-up. Notably, during the bead ...

Mass spectrometry-based shotgun proteomics is a powerful tool to measure the abundance of many proteins in biological samples simultaneously. Proteomics experiments with bioinformatics analysis are routinely employed to identify biomarkers and discover associated biological complexes and pathways underpinning pathological mechanisms. With its high analyte specificity and potential quantitative accuracy, shotgun proteomics also has excellent potential to be adopted by research facilities and diagnostic laboratories for clinical sample analysis without the need to rely on antibodies1,2.
To prepare protein samples for shotgun proteomics analysis, proteins extracted from biological samples (e.g., cells and tissues) typically first need to be processed using lengthy protocols, including measuring the sample protein concentration, protein reduction, and alkylation, and enzymatic digestion into peptides. Moreover, proteins extracted in common lysis buffers containing detergents often require additional steps of buffer exchange or detergent removal before analysis because detergent can interfere with trypsin digestion and significantly degrade the performance of downstream liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis3. Peptides are typically further desalted, dried, and reconstituted in LC-MS/MS compatible solvents following enzymatic digestion. These protein biochemistry procedures can be labor-intensive and time-consuming. Thus, they continue to limit the throughput of proteomics workflows and contribute to the variability of acquired data4,5. Human errors and biases have been recognized as crucial factors affecting data variance and reproducibility6,7. To minimize human errors in mass spectrometry sample preparation workflows, automated pipetting robotic systems have been utilized to improve the throughput and reproducibility of protein identification and quantification from shotgun proteomics and targeted mass spectrometry analysis, where such advances have been hailed as instrumental for continuing the push for widespread adoption of proteomics technologies in critical research and clinical settings8,9,10,11,12,13. However, most existing protocols utilize robotic liquid handling platforms that require substantial investment and training, limiting their utility in many laboratories in the academic environment or otherwise with a limited budget.
This article describes a protocol that utilizes a low-cost, open-source robotic liquid handling system, the OT-2, to semi-automate a typical shotgun proteomics sample preparation workflow. The OT-2 has a lower cost than many other robotic liquid handling systems, and at the time of writing, costs approximately $5,000 US dollars. When factoring in the prices of different modules and labware, the total cost to set up experiments in this protocol at the time of writing is around $10,000, which renders it more affordable to a considerably broader set of laboratories over more expensive options. The OT-2 is compatible with open-source programming through Python scripts and offers great flexibilities in user-defined DIY protocol design. Using three in-house developed scripts, the protocols below cover executing a typical shotgun proteomics sample preparation workflow on the OT-2 station with an archetypical protein standard (bovine serum albumin; BSA) and a complex protein sample of a normal human heart lysate (Figure 1). The procedures for processing (1) a BSA sample and (2) a complex cardiac lysate sample are detailed in Protocol sections 1, 2, 5, 6 and 3, 4, 5, 6, respectively. Sera-Mag carboxylate-modified magnetic beads are utilized in single-pot solid-phase-enhanced sample preparation (SP3) to remove detergents and salts in the protein and peptide samples. Tryptic digests from bovine serum albumin and human heart proteins are further cleaned by SP3 beads and submitted for LC-MS/MS analysis. Mass spectra are then analyzed using the MaxQuant software for peptide and protein identification. Representative results performed by us show that the protocol achieves excellent technical coefficients of variation (CV) while saving bench time and is non-inferior to hand digest.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>300 &#181;L pipette tips</td>
			<td>Opentrons</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>4-in-1 tube rack set</td>
			<td>Opentrons</td>
			<td></td>
			<td>Each set includes 2 base stands and 4 tube holder tops 1.5mL, 2mL, 15mL + 50mL, 15mL, and 50mL. We use 2mL and 15 mL + 50 mL tops in this study.</td>
		</tr>
		<tr>
			<td>Acclaim PepMap 100 C18 HPLC Column</td>
			<td>Thermo Scientific</td>
			<td>#164568</td>
			<td>3 &#956;m particle; 100 &#197; pore; 75 &#956;m x 150 mm</td>
		</tr>
		<tr>
			<td>Acetonitrile LC-MS grade</td>
			<td>VWR</td>
			<td>#JT9829</td>
			<td></td>
		</tr>
		<tr>
			<td>Aluminum block set</td>
			<td>Opentrons</td>
			<td></td>
			<td>This block set includes 3 tops that are compatible with 96-well, 2.0 mL tubes and a PCR strip to use with the OT-2 temperature module. We use the 2.0mL tube holder in this manuscript.</td>
		</tr>
		<tr>
			<td>Ammonium Bicarbonate</td>
			<td>Sigma-Aldrich</td>
			<td># A6141</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin Standard, 2 mg/mL</td>
			<td>Thermo Scientific</td>
			<td>#23210</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethylsulfoxide (DMSO) LC-MS grade</td>
			<td>Thermo Scientific</td>
			<td>#85190</td>
			<td></td>
		</tr>
		<tr>
			<td>Dithiothreitol</td>
			<td>Sigma-Aldrich</td>
			<td>#D5545</td>
			<td></td>
		</tr>
		<tr>
			<td>EASY-Spray HPLC Columns</td>
			<td>Thermo Scientific</td>
			<td>#ES800A</td>
			<td></td>
		</tr>
		<tr>
			<td>EasynLC 1200 Nano LC</td>
			<td>Thermo Scientific</td>
			<td>#LC140</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol Proof 195-200</td>
			<td>Fisher</td>
			<td>#04-355-720</td>
			<td></td>
		</tr>
		<tr>
			<td>Formic Acid LC-MS grade</td>
			<td>Thermo Scientific</td>
			<td>#85178</td>
			<td></td>
		</tr>
		<tr>
			<td>Human heart lysate</td>
			<td>Novus Biologicals</td>
			<td>NB820-59217</td>
			<td></td>
		</tr>
		<tr>
			<td>Iodoacetamide</td>
			<td>Sigma-Aldrich</td>
			<td>#I1149</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic tube rack</td>
			<td>Thermo Scientific</td>
			<td>#MR02</td>
			<td></td>
		</tr>
		<tr>
			<td>MAXQuant v.1.6.10.43</td>
			<td></td>
			<td></td>
			<td>Tyanova et al., 2016 (https://www.maxquant.org/)</td>
		</tr>
		<tr>
			<td>mySPIN 6 Mini Centrifuge</td>
			<td>Thermo Scientific</td>
			<td>#75004061</td>
			<td>benchtop mini centrifuge for quick spin</td>
		</tr>
		<tr>
			<td>NEST 2 mL 96-Well Deep Well Plate, V Bottom</td>
			<td>Opentrons</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>OT-2 magnetic module</td>
			<td>Opentrons</td>
			<td></td>
			<td>GEN1</td>
		</tr>
		<tr>
			<td>OT-2 P300 single channel pipette</td>
			<td>Opentrons</td>
			<td></td>
			<td>GEN1</td>
		</tr>
		<tr>
			<td>OT-2 P50 single channel pipette</td>
			<td>Opentrons</td>
			<td></td>
			<td>GEN1</td>
		</tr>
		<tr>
			<td>OT-2 robot pipetting robot</td>
			<td>Opentrons</td>
			<td>OT-2</td>
			<td></td>
		</tr>
		<tr>
			<td>OT-2 temperature module</td>
			<td>Opentrons</td>
			<td></td>
			<td>GEN1</td>
		</tr>
		<tr>
			<td>Pierce Quantitative Colorimetric Peptide Assay</td>
			<td>Thermo Scientific</td>
			<td>#23275</td>
			<td></td>
		</tr>
		<tr>
			<td>Protein LoBind tubes 2.0 mL</td>
			<td>Eppendorf</td>
			<td>#022431102</td>
			<td></td>
		</tr>
		<tr>
			<td>Protein Sequence Database</td>
			<td>UniProt/SwissProt</td>
			<td></td>
			<td>https://www.uniprot.org/uniprot/?query=proteome:UP000005640% 
			20reviewed:yes</td>
		</tr>
		<tr>
			<td>Sera-Mag SpeedBead Carboxylate-Modified Magnetic Particles, Hydrophobic</td>
			<td>Cytiva</td>
			<td>#65152105050250</td>
			<td></td>
		</tr>
		<tr>
			<td>Sera-Mag SpeedBead Carboxylate-Modified Magnetic Particles, Hydrophylic</td>
			<td>Cytiva</td>
			<td>#45152105050250</td>
			<td></td>
		</tr>
		<tr>
			<td>SpeedVac</td>
			<td>Thermo Scientific</td>
			<td></td>
			<td>Vacuum evaporator</td>
		</tr>
		<tr>
			<td>Thermo Q Exactive HF Mass Spectrometer</td>
			<td>Thermo Scientific</td>
			<td>#IQLAAEGAAPFALGMBFZ</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin MS Grade</td>
			<td>Thermo Scientific</td>
			<td>#90057</td>
			<td></td>
		</tr>
		<tr>
			<td>Water LC-MS grade</td>
			<td>VWR</td>
			<td>#BDH83645.400</td>
			<td></td>
		</tr>
	</tbody>
</table>

shotgun proteomics sample processing automated by an open-source lab robot

Mass spectrometry-based shotgun proteomics experiments require multiple sample preparation steps, including enzymatic protein digestion and clean-up, which can take up significant person-hours of bench labor and present a source of batch-to-batch variability. Lab automation with pipetting robots can reduce manual work, maximize throughput, and increase research reproducibility. Still, the steep starting prices of standard automation stations make them unaffordable for many academic laboratories. This article describes a proteomics sample preparation workflow using an affordable, open-source automation system (The Opentrons OT-2), including instructions for setting up semi-automated protein reduction, alkylation, digestion, and clean-up steps; as well as accompanying open-source Python scripts to program the OT-2 system through its application programming interface.

Three Python scripts are provided here that are compatible with the OT-2 robot, and that perform sample preparation for mass spectrometry proteomics with a single protein standard bovine serum albumin (technical replicates n = 5 digestions) and a detergent-containing human heart lysate sample (n = 5 digestions). Each digest product is partitioned into two peptide clean-up reactions. The number of identified peptide-spectrum matches (PSMs), peptides, and proteins in each run of the BSA and heart samples are shown in <stro...

Watch this Scientific Journal Video about Shotgun Proteomics Sample Processing Automated by an Open-Source Lab Robot at JoVE.com

Shotgun Proteomics Sample Processing Automated by an Open-Source Lab Robot

Detailed protocol and three Python scripts are provided for operating an open-source robotic liquid handling system to perform semi-automated protein sample preparation for mass spectrometry experiments, covering detergent removal, protein digestion, and peptide desalting steps.

Mass spectrometry-based shotgun proteomics experiments require multiple sample preparation steps, including enzymatic protein digestion and clean-up, ...

shotgun-proteomics-sample-processing-automated-an-open-source-lab

Research

JoVE Journal

Biochemistry

3.5K Views.  University of Colorado Anschutz Medical Campus. Detailed protocol and three Python scripts are provided for operating an open-source robotic liquid handling system to perform semi-automated protein sample preparation for mass spectrometry experiments, covering detergent removal, protein digestion, and peptide desalting steps.

Video: Shotgun Proteomics Sample Processing Automated by an Open-Source Lab Robot

Automated Acoustic Dispensing for the Serial Dilution of Peptide Agonists in Potency Determination Assays

As with small molecule drug discovery, screening for peptide agonists requires the serial dilution of peptides to produce concentration-response curves. Screening peptides affords an additional layer of complexity as conventional tip-based sample handling methods expose peptides to a large surface area of plasticware, providing an increased opportunity for peptide loss via adsorption. Preventing excessive exposure to plasticware reduces peptide loss via adherence to plastics and thus minimizes inaccuracies in potency prediction, and we have previously described the benefits of non-contact acoustic dispensing for in vitro high-throughput screening of peptide agonists1. Here we discuss a fully integrated automation solution for non-contact acoustic preparation of peptide serial dilutions in microtiter plates utilizing the example of screening for peptide agonists at the mouse glucagon-like peptide-1 receptor (GLP-1R). Our methods allow for high-throughput cell-based assays to screen for agonists and are easily scalable to support increased sample throughput, or to allow for increased numbers of assay plate copies (e.g., for a panel of more target cell lines).

Peptide adsorption to plasticware during traditional tip-based serial dilutions can significantly impact potency determination and confound the understanding of structure-activity relationships used for lead identification and lead optimization phases of drug discovery. Here methods for automated acoustic non-contact serial dilution of peptide samples are described.

As with small molecule drug discovery, screening for peptide agonists requires the serial dilution of peptides to produce concentration-response curves. ...

LERLIC-MS/MS for In-depth Characterization and Quantification of Glutamine and Asparagine Deamidation in Shotgun Proteomics

Characterization of protein deamidation is imperative to decipher the role(s) and potentialities of this protein posttranslational modification (PTM) in human pathology and other biochemical contexts. In order to perform characterization of protein deamidation, we have recently developed a novel long-length electrostatic repulsion-hydrophilic interaction chromatography-tandem mass spectrometry (LERLIC-MS/MS) method which can separate the glutamine (Gln) and asparagine (Asn) isoform products of deamidation from model compounds to highly complex biological samples. LERLIC-MS/MS is, therefore, the first shotgun proteomics strategy for the separation and quantification of Gln deamidation isoforms. We also demonstrate, as a novelty, that the sample processing protocol outlined here stabilizes the succinimide intermediate allowing its characterization by LERLIC-MS/MS. Application of LERLIC-MS/MS as shown in this video article can help to elucidate the currently unknown molecular arrays of protein deamidation. Additionally, LERLIC-MS/MS provides further understanding of the enzymatic reactions that encompass deamidation in distinct biological backgrounds.

Here we present a step-by-step protocol of the long-length electrostatic repulsion-hydrophilic interaction chromatography-tandem mass spectrometry (LERLIC-MS/MS) method. This is a novel methodology that enables for the first time quantification and characterization of the glutamine and asparagine deamidation isoforms by shotgun proteomics.

Characterization of protein deamidation is imperative to decipher the role(s) and potentialities of this protein posttranslational modification (PTM) in ...

Calibration-free In Vitro Quantification of Protein Homo-oligomerization Using Commercial Instrumentation and Free, Open Source Brightness Analysis Software

Number and brightness is a calibration-free fluorescence fluctuation spectroscopy (FFS) technique for detecting protein homo-oligomerization. It can be employed using a conventional confocal microscope equipped with digital detectors. A protocol for the use of the technique in vitro is shown by means of a use case where number and brightness can be seen to accurately quantify the oligomeric state of mVenus-labelled FKBP12F36V before and after the addition of the dimerizing drug AP20187. The importance of using the correct microscope acquisition parameters and the correct data preprocessing and analysis methods are discussed. In particular, the importance of the choice of photobleaching correction is stressed. This inexpensive method can be employed to study protein-protein interactions in many biological contexts.

Calibration-free In Vitro Quantification of Protein Homo-oligomerization Using Commercial Instrumentation and Free, Open Source Brightness Analysis Software

This protocol describes a calibration-free approach for quantifying protein homo-oligomerization in vitro based on fluorescence fluctuation spectroscopy using commercial light scanning microscopy. The correct acquisition settings and analysis methods are shown.

Number and brightness is a calibration-free fluorescence fluctuation spectroscopy (FFS) technique for detecting protein homo-oligomerization. It can be ...

Detection of Protein Ubiquitination Sites by Peptide Enrichment and Mass Spectrometry

The posttranslational modification of proteins by the small protein ubiquitin is involved in many cellular events. After tryptic digestion of ubiquitinated proteins, peptides with a diglycine remnant conjugated to the epsilon amino group of lysine (&#39;K-&#949;-diglycine&#39; or simply &#39;diGly&#39;) can be used to track back the original modification site. Efficient immunopurification of diGly peptides combined with sensitive detection by mass spectrometry has resulted in a huge increase in the number of ubiquitination sites identified up to date. We have made several improvements to this workflow, including offline high pH reverse-phase fractionation of peptides prior to the enrichment procedure, and the inclusion of more advanced peptide fragmentation settings in the ion routing multipole. Also, more efficient cleanup of the sample using a filter-based plug in order to retain the antibody beads results in a greater specificity for diGly peptides. These improvements result in the routine detection of more than 23,000 diGly peptides from human cervical cancer cells (HeLa) cell lysates upon proteasome inhibition in the cell. We show the efficacy of this strategy for in-depth analysis of the ubiquitinome profiles of several different cell types and of in vivo samples, such as brain tissue. This study presents an original addition to the toolbox for protein ubiquitination analysis to uncover the deep cellular ubiquitinome.

We present a method for the purification, detection, and identification of diGly peptides that originate from ubiquitinated proteins from complex biological samples. The presented method is reproducible, robust, and outperforms published methods with respect to the level of depth of the ubiquitinome analysis.

The posttranslational modification of proteins by the small protein ubiquitin is involved in many cellular events. After tryptic digestion of ...

Using the Open-Source MALDI TOF-MS IDBac Pipeline for Analysis of Microbial Protein and Specialized Metabolite Data

In order to visualize the relationship between bacterial phylogeny and specialized metabolite production of bacterial colonies growing on nutrient agar, we developed IDBac&#8212;a low-cost and high-throughput matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) bioinformatics pipeline. IDBac software is designed for non-experts, is freely available, and capable of analyzing a few to thousands of bacterial colonies. Here, we present procedures for the preparation of bacterial colonies for MALDI-TOF MS analysis, MS instrument operation, and data processing and visualization in IDBac. In particular, we instruct users how to cluster bacteria into dendrograms based on protein MS fingerprints and interactively create Metabolite Association Networks (MANs) from specialized metabolite data.

IDBac is an open-source mass spectrometry-based bioinformatics pipeline that integrates data from both intact protein and specialized metabolite spectra, collected on cell material scraped from bacterial colonies. The pipeline allows researchers to rapidly organize hundreds to thousands of bacterial colonies into putative taxonomic groups, and further differentiate them based on specialized metabolite production.

In order to visualize the relationship between bacterial phylogeny and specialized metabolite production of bacterial colonies growing on nutrient agar, ...

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 ...

SUMO-Binding Entities (SUBEs) as Tools for the Enrichment, Isolation, Identification, and Characterization of the SUMO Proteome in Liver Cancer

Post-translational modification is a key mechanism regulating protein homeostasis and function in eukaryotic cells. Among all ubiquitin-like proteins in liver cancer, the modification by SUMO (Small Ubiquitin MOdifier) has been given the most attention. Isolation of endogenous SUMOylated proteins in vivo is challenging due to the presence of active SUMO-specific proteases. Initial studies of SUMOylation in vivo were based on the molecular detection of specific SUMOylated proteins (e.g., by western blot). However, in many cases, antibodies, generally made with non-modified recombinant protein, did not immunoprecipitate SUMOylated forms of the protein of interest.&#160;Nickel chromatography has been the other approach to study SUMOylation by capturing histidine-tagged versions of SUMO molecules. This approach is mainly used in cells stably expressing or transiently transfected with His-SUMO molecules. To overcome these limitations, SUMO-binding entities (SUBEs) were developed to isolate endogenous SUMOylated proteins. Herein, we describe all the steps required for the enrichment, isolation, and identification of SUMOylated substrates from human hepatoma cells and hepatic tissues from a liver cancer mouse model by using SUBEs. Firstly, we describe methods involved in the preparation and lysis of the human hepatoma cells and liver tumor tissue samples. Then, a thorough explanation of the preparation of SUBEs and controls is detailed along with the protocol for the protein pull-down assays. Finally, some examples are provided regarding the options available for the identification and characterization of the SUMOylated proteome, namely the use of western-blot analysis for the detection of a specific SUMOylated substrate from liver tumors or the use of proteomics by mass spectrometry for high-throughput characterization of the SUMOylated proteome and interactome in hepatoma cells.

SUMO-Binding Entities SUBEs as Tools for the Enrichment, Isolation, Identification, and Characterization of the SUMO Proteome in Liver Cancer

Here, we present a protocol to enrich, isolate, identify, and characterize proteins modified by SUMO in vivo both from human hepatoma cells and liver tumors obtained from mouse models of hepatocellular carcinoma by using SUMO-binding entities (SUBEs).

Post-translational modification is a key mechanism regulating protein homeostasis and function in eukaryotic cells. Among all ubiquitin-like proteins in ...

TMT Sample Preparation for Proteomics Facility Submission and Subsequent Data Analysis

Proteomic technologies are powerful methodologies that can aid our understanding of mechanisms of action in biological systems by providing a global view of the impact of a disease, treatment, or other condition on the proteome as a whole. This report provides a detailed protocol for the extraction, quantification, precipitation, digestion, labeling, and subsequent data analysis of protein samples. Our optimized TMT labeling protocol requires a lower tag-label concentration and achieves consistently reliable data. We have used this protocol to evaluate protein expression profiles in a variety of mouse tissues (i.e., heart, skeletal muscle, and brain) as well as cells cultured in vitro. In addition, we demonstrate how to evaluate thousands of proteins from the resulting dataset.

We present an optimized tandem mass tag (TMT) labeling protocol that includes detailed information for each of the following steps: protein extraction, quantification, precipitation, digestion, labeling, submission to a proteomics facility, and data analyses.

Proteomic technologies are powerful methodologies that can aid our understanding of mechanisms of action in biological systems by providing a global view ...

Making Precise and Accurate Single-Molecule FRET Measurements using the Open-Source smfBox

The smfBox is a recently developed cost-effective, open-source instrument for single-molecule F&#246;rster Resonance Energy Transfer (smFRET), which makes measurements on freely diffusing biomolecules more accessible. This overview includes a step-by-step protocol for using this instrument to make measurements of precise FRET efficiencies in duplex DNA samples, including details of the sample preparation, instrument setup and alignment, data acquisition, and complete analysis routines. The presented approach, which includes how to determine all the correction factors required for accurate FRET-derived distance measurements, builds on a large body of recent collaborative work across the FRET Community, which aims to establish standard protocols and analysis approaches. This protocol, which is easily adaptable to a range of biomolecular systems, adds to the growing efforts in democratising smFRET for the wider scientific community.

This article provides step-by-step instructions for making fully-corrected accurate FRET measurements on individual, freely diffusing biomolecules using the open-source, inexpensive smfBox, from switch on, through alignment and focusing, to data collection and analysis.

The smfBox is a recently developed cost-effective, open-source instrument for single-molecule F&#246;rster Resonance Energy Transfer (smFRET), which makes ...