EasyPep™ MS Sample Prep Kits

High sample viscosity after lysis is due to release of DNA from the nucleus. Sonication or addition of a nuclease such as the Pierce Universal Nuclease (Cat. No. 88700, 88701, or 88702) can be used to degrade DNA and reduce sample viscosity.

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Add 0.5 mm diameter glass beads to the sample pelleted in Easy Pep Lysis Solution and proceed as recommended in the Easy Pep sample prep protocol. Vortex vigorously for few minutes, spin at 16,000 x g for 5 mins, and extract the supernatant for protein assay and further downstream sample preparation.

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Add 1-2 µL of 50 mg/mL Lysozyme Solution (Cat. No. 90082) to 200 µL of the EasyPep lysis buffer provided in the kit and proceed with the sample prep. Add 200 µL of the prepared lysis solution to 5 X 10E8 bacterial cells (E. coli cells) (OD600 equal to 1, corresponding to 1 X 10E8 CFUs). Lyse by pipetting the sample repeatedly and centrifuge at 16,000 x g for 5 mins. Alternatively, E. coli cells can be lysed in lysis buffer using bead beating or sonication instead of lysozyme. After lysis, dilute samples to 1 mg/mL using lysis buffer, proceed with the EasyPep protocol for reduction, alkylation, digestion, and clean up as described in the product manual.

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High Select Top14 Abundant Protein Depletion Mini Spin columns (Cat. Nos. A36369, A36370) can be used to deplete top 14 abundant plasma/serum proteins. The depletion of highly abundant proteins from the sample enables the detection and identification of low abundant proteins. The depleted samples can be processed with EasyPep MS sample prep kit to generate digested plasma/serum samples. The clean digested samples can be processed by nanoLC-MS/MS analysis for discovery experiments or nanoLC-PRM/MS analysis for targeted experiments.

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TMT labeling can be performed after reduction, alkylation, digestion, or prior to cleanup, if the sample is buffered at appropriate pH (8-8.5) in a suitable buffer without primary amines (e.g., Tris, glycine). TMT labeling can also be performed after peptide clean-up. Labeling of peptides after clean-up enables measuring and normalizing of the peptide samples for equal mixing.

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