Terms concerning the TruQuant Protocol

Terms used in IROA

Accurate Compound ID. The IROA Internal Standard (an identical amount of labeled 95% U-13C only metabolites as in the LTRS) is spiked into experimental samples and is used as a yardstick in which to quantify all biochemicals in the sample relative to their counterparts in the LTRS.  The dictionary is used identify the same compounds in experimental samples. 

Creation of a RT Dictionary.  The IROA Long-Term Reference Standard (a 1:1 paired mixture of labeled U-5% and – 95% U-13C metabolites) is analyzed every 10 samples to build a dictionary of RT, m/z, and physical characteristics together with the ClusterFinder software.

Dual MSTUS algorithm.  An algorithm that requires a biochemically complex internal standard and which then normalized the analytical sample to have the same MSTUS as the MSTUS of the internal standard.   If a historically-derived set of values is used, this algorithm can normalize all samples to the to be more comparable despite significant source differences. 

Identification of Unknown Fragments. Fragments have the IROA ratio pattern derived from their parent peaks and can be identified using the “peak correlation” ClusterFinder module.

Isotopologs.  Isotopomers which differ in the number of isotopes in each molecules. Within each Isotopolog there are many positional isotopomers.

Isotopomer Ladder.  Each molecular formula has a collection of possible isotopologs that extend from the C12 monoisotopomeric peak to the C13 monoisotopomeric peak.  

No sample material wasted.  The TruQuant Workflow  calibration experiment optimizes the quantity of experimental sample to use for a successful outcome.

Platform agnostic.  The TruQuant Protocol can be used across different chromatographic systems and results can be equated using the dictionary because of comparability of the IROA-LTRS and IROA-IS, by querying the same mass and secondary physical characteristics across systems.

Removal of false data. Unique IROA patterns discriminate peaks of biological origin from artifactual peaks.

Reproducible.  Sample normalization to a universal standard for complete comparability across days and laboratories.

Sample Normalization. The total area under the curve (AUC) for all natural abundance experimental suppression-corrected peaks is normalized to the total AUC of their corresponding IROA-IS peaks. is a “Dual MSTUS[1]” algorithm that allows for normalization of samples not only within a single day’s run, but since the IROA-IS is equivalent every day; all normalizations are to a true Standard, i.e. that is the same every day.  Normalization overcomes sample-to-sample variation.  [1] MSTUS described in “Normalization strategies for metabonomic analysis of urine samples” Warrack et. al

Semi-targeted.  ClusterFinder Software searches for the highly characterized 1000+ known IROA LTRS peaks and also will search for unlabeled compound peaks using user generated natural abundance libraries 

Software solution.  Clusterfinder builds libraries, IDs/quantitates compounds, corrects for ion-suppression and normalizes data.  ClusterFinder outputs three values: 1) the raw (suppressed) values observed; 2) a suppression-corrected value; and 3) a normalized (suppression-corrected and normalized) value. 

Suppression Correction for significantly better quantitation.  Because the ratio of the C-12 envelope to the C-13 envelope for each molecule is unaffected by almost all sources induced inefficiencies (suppression, sensu latu) it can be used to correct for all source ionizations losses.  This ability should correct for any situation where the C12/C13 ratio after the loss remains effectively the same, i.e. there are no significant isotopic effects involved.