Table 1.

Troubleshooting table.

Step	Problem	Possible cause	Solution
23	Poor MALDI profiles (weak or no signals) during in vitro assay	Reaction was not quenched properly	Pipette the sample 10 to 20 times (Box 1 Step 2) to ensure proper mixing. Alternatively, vortex the samples after addition of 8 M GndHCl quenching solution.
34	Noisy quantitative data	Reaction times were not carefully controlled	Ensure that the reaction start and stop times are synchronized (Step 34)