We develop new techniques in mass spectrometry to measure stable isotopically labeled (SIL) compounds in new, more precise, and more sensitive ways to be used as tracers of metabolism in humans, animals, and in cell culture.
We develop new methods of sample isolation and derivatization
We develop kinetic models to understand tracer metabolism
We develop mass spectrometry methods for metabolomics
We develop mass spectrometry methods for proteomics
Stable isotopes are not radioactive. They occur naturally in nature.
For example, 99% of all carbon in the world is carbon-12 (12C) and 1% is carbon-13 (13C). We purchase enriched stable isotopes that have been placed into compounds in abundances much greater than their natural abundance. We can obtain labeled compounds with ~95-99% 13C.
Because a mass spectrometer separates ions by mass, we use mass spectrometry to distinguish isotopes in compounds by their mass.
For example, 13C is 1 Dalton (or atomic mass unit) heavier than 12C, and a 13C-labelled compound appears in the mass spectrometer at a higher mass from an unlabeled compound.
We use the isotopes of hydrogen (deuterium, 2H), carbon (13C), nitrogen (15N), and oxygen (18O).
We administer SIL compounds to humans as tracers to define the rates of production, disposal and conversion of metabolites in the body.
Using tracers we can determine, for example, how much glucose the liver is making at any point in time, how much protein is being broken down in the body and how much of each amino acid is being released from this breakdown.
We use tracers and mass spectrometers to study specific metabolomes.
We use SIL compounds in cell culture as tracers to define metabolic pathways and the rates of production and disposal of metabolites.
Using tracers we can determine, for example, how much glucose proceeds to lactate via glycolysis versus how much glucose carbon enters the TCA cycle.
We can determine how much glycogen is synethized or broken down.
We can determine uptake and metabolism of glutamine.
We use mass spectrometry to identify proteins and their modifications, and we use stable isotopes to quantify protein and peptide amounts in proteomics.
Measuring stable isotopic enrichments in biological matrices is not simple:
Mass spectrometry instrumentation comes in different forms—all expensive and complex to use.
In most cases, biological samples require isolation and modification steps before they are suitable for measurement by mass spectrometry.
Designing experiments and labeled compounds to measure a specific metabolic event in the body is not simple.