This presentation demonstrates workflows for the stable isotope labeling of protein digests and synthetic peptides employing oxygen 18 enriched water first in the protease catalyzed paleo time course experiment, incubates substrate and protease in the presence of 50%Oxygen 18 enriched water to incorporate oxygen. 18 atoms then for protease is capable of double labeling. Repeat incubation of the post digestion cleavage products with protease of interest in the presence of 50%oxygen 18 enriched water.
The EO workflow performs the acid catalyzed incorporation of oxygen 18 atoms into functional groups at timed intervals. Spot aliquots of the reaction mixtures with matrix on moldy target plates upon mass spectrometric data acquisition generates spectral time plots of the peptide cleavage reactions as well as oxygen 18 incorporation plots of individual peptide species labeled cleavage products are selected for MSM S based sequence identification. Ultimately, these workflows offer versatile tools for quantitative and qualitative proteomic studies.
This method can help answer key questions in the protease research field, such as identifying rate, limiting steps and reaction intermediates in complex proteolytic pathways. Proteolytic signatures identified by the paleo time course provide important facts regarding substrate specificity. In addition, the timers of data also uses kinetic information.
The A postdoc from my laboratory will now demonstrate the procedure. The paleo time course workflow monitors dynamics of proteolytic cleavage reactions based on protease catalyzed oxygen 18 incorporation for the 20 microliter reaction, add the sample peptides to the protease reaction buffer containing oxygen 18 enriched water mix 0.5 microliters of the reaction mixture with 0.5 microliters of matrix spot on an opti to 3 84 maldi target plate and leave the solvent droplets at room temperature until dry. Meanwhile, split the reaction mixture into two tubes.
Control and sample for the sample tube. Add protease of interest and incubate at recommended enzyme reaction temperature. Add specified time points.
Remove a 0.5 microliter aliquot to mix with 0.5 microliters of matrix and spot on the multi targett plate. Proceed to analyze the reaction dynamics by MALDI to toff ms MS analysis as described later in this paleo post digestion labeling workflow SN produce produces like trypsin, catalyze the carboxyl oxygen exchange reaction to incorporate oxygen.18. After performing a protein digest without oxygen 18 labeling, pass the cleavage products through a pep clean C 18 spin column to eliminate residual protease activities.
Then resuspend samples in 20 microliters of tripsin reaction buffer containing oxygen 18 enriched water. Remove a 0.5 microliter aliquot and mix with equal volume of matrix. Then spot on an opti off 3 84 maldi target plate to air dry.
Next, split the reaction solution into control and sample tubes for the sample tube. Add trypsin and incubate at 37 degrees Celsius. To monitor the reaction, remove a 0.5 microliter aliquot.
Mix with 0.5 microliters of matrix and spot on a maltar plate. Analyze the dynamics of this carboxyl oxygen exchange reaction by Maldi Toof MSM S analysis. IEO Time course workflow relies on the acid catalyzed carboxyl oxygen exchange reactions of acidic peptide side and terminal groups.
First incubate 50 nanomolar of individual peptides with one-to-one oxygen 18 enriched water in the presence or absence of 0.1%Final trichloroacetic acid sample 0.5 microliter aliquots of the reaction daily for 48 days directly copo with matrix onto a MALDI targett plate. Regularly submit the MALDI TARGETT plate for MALDI TOOF MSM S product analysis. This section is detailed in the accompanying manuscript.
First, acquire triplicate MS Spectra in positive ion mode. After calibrating the multipl and setting up the MS acquisition, acquire single shots for sub spectra. Next, export the MS data files from the 4, 000 series Explorer data acquisition software.
Then import into an in-house information system that utilizes mascot distiller software for spectral processing and peak detection. Deconvolute the isotopic envelopes and determine oxygen 18 incorporation ratios automatically note the oxygen 18 incorporation ratios as the relative contributions of individual peptide isotope species to the entire isotopic envelope. Filter the bin list and bin at least three values at 100 PP m mass width for each time course experiment.
Extract the molecular masses for all detected peptide species from the associated MS data files. Now using X pacey find pep set a 200 PPM mass error acceptance tolerance. Compare the bin list to the data of proteolytic cleavage products predicted from the substrate peptide sequence.
Proceed to acquire msms spectra for all mass values of cleavage products predicted by the find pep tool and for bin values that have associated oxygen 18 incorporations. Collect MSM S data of 50 shots in a randomized pattern per sub spectra with up to 40 sub spectra per spot and export the msms files. Then export the MSM S data files into the analysis system for peak detection and MSM S peak lists associated with the corresponding bend MS data for peptide identification.
Set these search parameters in the mascot search engine, no enzyme specificity, 150 PPM precursor ion and 0.2 Dalton fragment ion mass tolerances. Search the M-S-M-S-P lists against the Swiss Pro database. Peptide identifications can additionally be validated using data explorer software by confirming the characteristic oxygen 18 incorporation patterns across yer fragment ions for spectral time plots.
Export the MS data files for each reaction time point from the data explorer software ASCI files using a macro. Then import the files into a data analysis and graphic software program and display as waterfall plots to create oxygen 18 incorporation plots for each bend. Peptide cleavage product extract the relative contributions of individual peptide isotope species across all reaction time points, then plot against time.
Spectral time plots like this one, display the dynamics of proteolytic cleavage reactions. This experiment analyzes cleavage of the bioactive peptide endo and C by the endothelium converting enzyme one. A waterfall arrangement plots the MS spectra of the paleo time course experiments to simultaneously monitor the degradation of the substrate and the emergence of intermediate and final products.
The cleavage products are identified by MSMS and the characteristic oxygen 18 incorporation signatures of their isotope envelopes. This reaction mechanism of trypsin indicates the searing proteases mediate incorporation of up to two oxygen 18 atoms into peptide cleavage products. In the protease based labeling workflow, the peptide bond cleavage reaction results in a 50%single oxygen 18 incorporation ratio for freshly generated peptide cleavage products proteases like trypsin that rebind the reaction products further catalyze the incorporation of a second oxygen 18 atom via the carboxyl oxygen exchange reaction.
At equilibrium, the oxygen 18 label is distributed in a ratio of one to two to one in unlabeled single labeled and double labeled products. In the pre-digestion labeling of proteolytic termini workflow, no peptide bond cleavages occur. Instead, the incorporation of up to two oxygen 18 atoms is exclusively based on the carboxyl oxygen exchange reaction.
Therefore, oxygen 18 incorporation only occurs with proteases that rebind their peptide cleavage products. Acid catalyzed oxygen 18 labeling leads to the incorporation of two oxygen 18 atoms per carboxyl group. Over the course of this experiment, the multiple plus two Dalton mass shifts of the isotopic envelope of angiotensin one can be mapped by the uptake of oxygen 18 atoms.
By combining OPE labeling and high resolution mass spectrometry in a time resolved manner. The paleo time course method allows for a dynamic analysis of the generation of peptide products. The assay can be used to generate stabilized topically labeled peptides for quantitative and qualitative proteomic studies, and to evaluate the kinetics by which Protopic peptides are generated.
The Paleo time course is designed to evaluate proteolytic pathways under physiologically relevant conditions. This technique paved the way for our recent survey of lytic processes in human cancer.Microenvironments.
