Category Archives: Uncategorized


January 26, 2015

We are expecting a short interruption in our services on Wednesday, January 28 which will affect LCT and QTRAP customers (James). A longer interruption is expected for Orbitrap services (Tania): Wednesday through Friday, if all goes well. The OPP electricians will be installing a new circuit breaker in the main panel in our lab.

The sample preparation for MS (in-gel digestion) and MALDI TOF analyses will not be affected.


August 5, 2014

Joana’s sample is running. It takes 24 hrs of Orbi time to run 1 Joana’s sample: 3 blanks, 1 standard, 1 control, and 1 sample. All this to ensure that everything works as expected: the instrument, the sample prep, the chromatography. Talk about loving care…


July 30, 2014

Orbi is well and running Olga’s samples. Joana’s and Anna’s samples are digested.

Ammonium bicarbonate or triethylammonium bicarbonate?

This was a question from one of my blog’s secret readers. Actually, most of the time I feel like I am talking to myself: “Hey Tania, how do you prepare a protein sample for proteolysis?” “Well, Tania, let me show you in a step-by-step tutorial.” No comments, no questions, no pointing out typos, no “thank you, Tania, but there’s a better way to do this”?

Oh well, back to ammonium bicarbonate. This is a volatile salt which breaks down to ammonia, carbon dioxide, and water. Volatile salts are the only salts compatible with MS. Aqueous solutions of ammonium bicarbonate (0.01 – 0.1 M) have pH around 8, the optimal pH for trypsin activity. Ammonium bicarbonate competes with basic amino acids for Coomassie dye, which makes it a great de-staining reagent for the in-gel digestion procedure. All this goodness comes at a very reasonable price – what not to like? Another ammonium salt, triethylammonium bicarbonate (TEAB), is more volatile than ammonium bicarbonate; it is also more expensive. TEAB is a buffer of choice for LC-MS applications: TMT (iTRAQ) amine-reactive labeling, ion-exchange chromatography, protein solubilization (when neutral and acidic pH is undesirable), in-gel digestion, etc.