eoe sub articles

EoE Sub Articles

1. Immunoprecipitation
NOTE: We used non-sodium dodecyl sulfate (SDS) lysis buffer and citrate elution, as described in the following sections. However, the use of an alternative in-house immunoprecipitation technique may be also applicable for preparing LC-MS/MS samples.
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	<li>Transfect cultured cells with vectors encoding an epitope tag alone or a fusion protein. For acquiring representative data, transfer J774 cells (1 x 106) with vectors encoding a green f...

on-membrane protein digestion to prepare co-immunoprecipitated proteins for interaction studies

Source: Obama, T. et al., <a href="https://app.jove.com/v/59733">Evaluation of Protein&#8211;Protein Interactions using an On-Membrane Digestion Technique.</a>&#160;J. Vis. Exp.&#160; (2019)
This video demonstrates co-immunoprecipitated protein complexes on a PVDF membrane for protein-protein interaction analysis. The reduced proteins from complexes were treated with trypsin to cleave the individual proteins at the smaller peptides, then, the remaining peptides were extracted from the PVDF membrane. The pulled peptide derived from both proteins in the complex was then dried and resuspended in a low concentration of formic acid for further analysis.

On-Membrane Protein Digestion to Prepare Co-Immunoprecipitated Proteins for Interaction Studies

Source: Obama, T. et al., Evaluation of Protein&#8211;Protein Interactions using an On-Membrane Digestion Technique.&#160;J. Vis. Exp.&#160; (2019)
This ...

To perform on-membrane digestion, take a solution of co-immunoprecipitated protein complexes, each containing a recombinant GFP-tagged target protein associated with its partner protein.
Transfer the proteins to a tube containing a pre-wet polyvinylidene difluoride, PVDF membrane, and incubate. The PVDF membrane&#39;s hydrophilic surface helps to transfer the proteins onto the membrane.
Transfer the protein-containing membrane to a fresh tube. Add a reducing agent-containing buffer to reduce the disulfide bonds between the cysteine residues, leading to denaturation of the individual proteins in the complexes without disturbing their interaction.
Replace this solution with an alkylating reagent, which alkylates the sulfhydryl group of both proteins in the complexes and prevents the reformation of disulfide bonds. Wash the membrane to remove any excess reagent.
Treat the membrane with a buffer containing trypsin &#8212; a proteolytic enzyme. Trypsin cleaves the GFP-tagged target protein and its partner protein at the arginine and lysine residues&#39; carboxyl terminal, releasing the smaller peptides into the supernatant. Transfer the supernatant into a fresh tube.
Wash the membrane with an acidic solution, dissociating any bound peptides from the membrane, ensuring complete extraction. Pull the peptide-containing fractions into a single tube. Desiccate via vacuum drying.
Resuspend the residues in a low concentration of formic acid, dissolving the peptides, which are ready for protein-protein interaction identification.

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Research

JoVE Encyclopedia of Experiments

Biological Techniques

Biomolecular Interaction Detection Techniques

Protein-protein interactions

Efficient Purification and LC-MS/MS-based Assay Development for Ten-Eleven Translocation-2 5-Methylcytosine Dioxygenase

The epigenetic transcription regulation mediated by 5-methylcytosine (5mC) has played a critical role in eukaryotic development. Demethylation of these epigenetic marks is accomplished by sequential oxidation by ten-eleven translocation dioxygenases (TET1-3), followed by the thymine-DNA glycosylase-dependent base excision repair. Inactivation of the TET2 gene due to genetic mutations or by other epigenetic mechanisms is associated with a poor prognosis in patients with diverse cancers, especially hematopoietic malignancies. Here, we describe an efficient single step purification of enzymatically active untagged human TET2 dioxygenase using cation exchange chromatography. We further provide a liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach that can separate and quantify the four normal DNA bases (A, T, G, and C), as well as the four modified cytosine bases (5-methyl, 5-hydroxymethyl, 5-formyl, and 5-carboxyl). This assay can be used to evaluate the activity of wild type and mutant TET2 dioxygenases.

Here, we present a protocol for an efficient single step purification of the active untagged human ten-eleven translocation-2 (TET2) 5-methylcytosine dioxygenase using ion-exchange chromatography and its assay using a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based approach.

The epigenetic transcription regulation mediated by 5-methylcytosine (5mC) has played a critical role in eukaryotic development. Demethylation of these ...

JoVE Journal

Biochemistry

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 ...

Fast Enzymatic Processing of Proteins for MS Detection with a Flow-through Microreactor

The vast majority of mass spectrometry (MS)-based protein analysis methods involve an enzymatic digestion step prior to detection, typically with trypsin. This step is necessary for the generation of small molecular weight peptides, generally with MW &#60; 3,000-4,000 Da, that fall within the effective scan range of mass spectrometry instrumentation. Conventional protocols involve O/N enzymatic digestion at 37 &#186;C. Recent advances have led to the development of a variety of strategies, typically involving the use of a microreactor with immobilized enzymes or of a range of complementary physical processes that reduce the time necessary for proteolytic digestion to a few minutes (e.g., microwave or high-pressure). In this work, we describe a simple and cost-effective approach that can be implemented in any laboratory for achieving fast enzymatic digestion of a protein. The protein (or protein mixture) is adsorbed on C18-bonded reversed-phase high performance liquid chromatography (HPLC) silica particles preloaded in a capillary column, and trypsin in aqueous buffer is infused over the particles for a short period of time. To enable on-line MS detection, the tryptic peptides are eluted with a solvent system with increased organic content directly in the MS ion source. This approach avoids the use of high-priced immobilized enzyme particles and does not necessitate any aid for completing the process. Protein digestion and complete sample analysis can be accomplished in less than ~3 min and ~30 min, respectively.

A quick protocol for proteolytic digestion with an in-house built flow-through tryptic microreactor coupled to an electrospray ionization (ESI) mass spectrometer is presented. The fabrication of the microreactor, the experimental setup and the data acquisition process are described.

The vast majority of mass spectrometry (MS)-based protein analysis methods involve an enzymatic digestion step prior to detection, typically with trypsin. ...

On-Membrane Protein Digestion to Prepare Co-Immunoprecipitated Proteins for Interaction Studies

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