3 research outputs found
Gas Chromatography-Quadrupole Time-of-Flight Mass Spectrometry-Based Determination of Isotopologue and Tandem Mass Isotopomer Fractions of Primary Metabolites for <sup>13</sup>C‑Metabolic Flux Analysis
For the first time an analytical
work flow based on accurate mass
gas chromatography-quadrupole time-of-flight mass spectrometry (GC-QTOFMS)
with chemical ionization for analysis providing a comprehensive picture
of <sup>13</sup>C distribution along the primary metabolism is elaborated.
The method provides a powerful new toolbox for <sup>13</sup>C-based
metabolic flux analysis, which is an emerging strategy in metabolic
engineering. In this field, stable isotope tracer experiments based
on, for example, <sup>13</sup>C are central for providing characteristic
patterns of labeled metabolites, which in turn give insights into
the regulation of metabolic pathway kinetics. The new method enables
the analysis of isotopologue fractions of 42 free intracellular metabolites
within biotechnological samples, while tandem mass isotopomer information
is also accessible for a large number of analytes. Hence, the method
outperforms previous approaches in terms of metabolite coverage, while
also providing rich isotopomer information for a significant number
of key metabolites. Moreover, the established work flow includes novel
evaluation routines correcting for isotope interference of naturally
distributed elements, which is crucial following derivatization of
metabolites. Method validation in terms of trueness, precision, and
limits of detection was performed, showing excellent analytical figures
of merit with an overall maximum bias of 5.8%, very high precision
for isotopologue and tandem mass isotopomer fractions representing
>10% of total abundance, and absolute limits of detection in the
femtomole
range. The suitability of the developed method is demonstrated on
a flux experiment of <i>Pichia pastoris</i> employing two
different tracers, i.e., 1,6<sup>13</sup>C<sub>2</sub>-glucose and
uniformly labeled <sup>13</sup>C-glucose
An Interlaboratory Evaluation of Drift Tube Ion Mobility–Mass Spectrometry Collision Cross Section Measurements
Collision
cross section (CCS) measurements resulting from ion mobility–mass
spectrometry (IM-MS) experiments provide a promising orthogonal dimension
of structural information in MS-based analytical separations. As with
any molecular identifier, interlaboratory standardization must precede
broad range integration into analytical workflows. In this study,
we present a reference drift tube ion mobility mass spectrometer (DTIM-MS)
where improvements on the measurement accuracy of experimental parameters
influencing IM separations provide standardized drift tube, nitrogen
CCS values (<sup>DT</sup>CCS<sub>N2</sub>) for over 120 unique ion
species with the lowest measurement uncertainty to date. The reproducibility
of these <sup>DT</sup>CCS<sub>N2</sub> values are evaluated across
three additional laboratories on a commercially available DTIM-MS
instrument. The traditional stepped field CCS method performs with
a relative standard deviation (RSD) of 0.29% for all ion species across
the three additional laboratories. The calibrated single field CCS
method, which is compatible with a wide range of chromatographic inlet
systems, performs with an average, absolute bias of 0.54% to the standardized
stepped field <sup>DT</sup>CCS<sub>N2</sub> values on the reference
system. The low RSD and biases observed in this interlaboratory study
illustrate the potential of DTIM-MS for providing a molecular identifier
for a broad range of discovery based analyses
An Interlaboratory Evaluation of Drift Tube Ion Mobility–Mass Spectrometry Collision Cross Section Measurements
Collision
cross section (CCS) measurements resulting from ion mobility–mass
spectrometry (IM-MS) experiments provide a promising orthogonal dimension
of structural information in MS-based analytical separations. As with
any molecular identifier, interlaboratory standardization must precede
broad range integration into analytical workflows. In this study,
we present a reference drift tube ion mobility mass spectrometer (DTIM-MS)
where improvements on the measurement accuracy of experimental parameters
influencing IM separations provide standardized drift tube, nitrogen
CCS values (<sup>DT</sup>CCS<sub>N2</sub>) for over 120 unique ion
species with the lowest measurement uncertainty to date. The reproducibility
of these <sup>DT</sup>CCS<sub>N2</sub> values are evaluated across
three additional laboratories on a commercially available DTIM-MS
instrument. The traditional stepped field CCS method performs with
a relative standard deviation (RSD) of 0.29% for all ion species across
the three additional laboratories. The calibrated single field CCS
method, which is compatible with a wide range of chromatographic inlet
systems, performs with an average, absolute bias of 0.54% to the standardized
stepped field <sup>DT</sup>CCS<sub>N2</sub> values on the reference
system. The low RSD and biases observed in this interlaboratory study
illustrate the potential of DTIM-MS for providing a molecular identifier
for a broad range of discovery based analyses