Isobaric Interference
Isobaric Interference - Related Videos
01:21
Isochoric and Isobaric Processes
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2023
A thermodynamic process that occurs at constant volume is called an isochoric process. According to the first law of thermodynamics, heat supplied or removed from the system is partially utilized to perform work and change the internal energy of the system. However, in an isochoric process, the volume remains constant. Hence, the work done by the system is zero. Therefore, the exchange of heat changes the internal energy of the system only. Suppose 1000 g of water is heated from 40 degrees...
02:18
Interference and Diffraction
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2020
Interference is a characteristic phenomenon exhibited by waves. When two electromagnetic waves interact with their peaks and troughs coinciding, a resulting wave with enhanced amplitude is produced. This is known as constructive interference. In this case, the two waves interacting are in phase with each other. Alternatively, if the two waves coincide and interact in a way such that the trough of one wave coincides with the peak of the other (in an out of phase manner), the resultant wave will...
08:41
Interference and Diffraction
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2023
Source: Yong P. Chen, PhD, Department of Physics & Astronomy, College of Science, Purdue University, West Lafayette, IN Interference and diffraction are characteristic phenomena of waves, ranging from water waves to electromagnetic waves such as light. Interference refers to the phenomenon of when two waves of the same kind overlap to give an alternating spatial variation of large and small wave amplitude. Diffraction refers to the phenomenon of when a wave passes through an aperture or...
09:06
Enhanced Sample Multiplexing of Tissues Using Combined Precursor Isotopic Labeling and Isobaric Tagging (cPILOT)
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Cited by 10 •
2017
Combined precursor isotopic labeling and isobaric tagging (cPILOT) is a quantitative proteomics strategy that enhances sample multiplexing capabilities of isobaric tags. This protocol describes the application of cPILOT to tissues from an Alzheimer's disease mouse model and wild-type controls.
01:23
RNA Interference
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2019
RNA interference (RNAi) is a process in which a small non-coding RNA molecule blocks the post-transcriptional expression of a gene by binding to its messenger RNA (mRNA) and preventing the protein from being translated. This process occurs naturally in cells, often through the activity of genomically-encoded microRNAs. Researchers can take advantage of this mechanism by introducing synthetic RNAs to deactivate specific genes for research or therapeutic purposes. For example, RNAi could be used...
FAQs
The key distinction is between nominal mass, which uses whole-number mass values, and exact mass, which reflects the more precise mass associated with an ion’s elemental composition. Two species can therefore appear equivalent at nominal m/z while differing in exact mass. Recognizing this difference explains why assignments based only on a low-resolution mass value may be uncertain.
When multiple chemical species reach the detector together, their contributions are recorded within an overlapping signal rather than as independently resolved measurements. The resulting intensity may represent more than one ion, so assigning the full signal to a single compound can distort its apparent abundance. This effect is especially consequential when interpreting complex samples.
Ions that overlap in mass-to-charge ratio may produce different fragment ions when analyzed by tandem mass spectrometry. Comparing these fragmentation behaviors provides an additional level of evidence beyond the precursor m/z value. Distinct fragment patterns can help separate competing assignments and increase confidence that the measured signal has been attributed to the appropriate chemical species.
High-resolution mass spectrometry measures m/z with greater precision, allowing ions with different exact masses to be distinguished even when their nominal masses are the same. This separation can reveal that an apparently single signal contains chemically different contributors. It improves identification confidence and can support more reliable interpretation of abundance measurements when mass differences are sufficiently resolved.
A useful workflow combines complementary evidence rather than relying on one mass value. Researchers can apply chromatographic separation to resolve species before detection, use high-resolution measurements to compare exact masses, examine isotope patterns, and collect tandem mass spectra for fragmentation evidence. Together, these steps help identify overlapping contributors and assess whether a signal supports a specific assignment.
The issue becomes especially important when analyzing complex samples that contain several chemically distinct species near the same m/z. In such settings, overlapping signals can lead to misleading molecular assignments or inaccurate quantitation. High-resolution mass spectrometry, chromatographic separation, isotope-pattern analysis, and tandem mass spectrometry provide complementary approaches for improving confidence in the reported chemical identities and abundances.