Molecular Mass
Molecular Mass - Related Videos
08:52
Spatial Molecular Imaging of the Glycome Using Mass Spectrometry
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Cited by 1 •
2025
This protocol details the key steps to enable rigorous and reproducible measurement of both glycogen and N-linked glycans using mass spectrometry imaging.
09:22
Atmospheric-pressure Molecular Imaging of Biological Tissues and Biofilms by LAESI Mass Spectrometry
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Cited by 29 •
2010
Laser ablation electrospray ionization (LAESI) is an atmospheric-pressure ion source for mass spectrometry. In the imaging mode, a mid-infrared laser probes the distributions of molecules across a tissue section or a biofilm. This technique presents a new approach for diverse bioanalytical studies carried out under native experimental conditions.
09:53
Molecular Beam Mass Spectrometry With Tunable Vacuum Ultraviolet (VUV) Synchrotron Radiation
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Cited by 7 •
2012
A molecular beam coupled to tunable vacuum ultraviolet photoionization mass spectrometer at a synchrotron provides a convenient tool to explore the electronic structure of isolated gas phase molecules and clusters. Proton transfer mechanisms in DNA base dimers were elucidated with this technique.
01:20
Mass Spectrometry: Molecular Fragmentation Overview
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2024
The ionization of a molecule into a molecular ion inside the mass spectrometer causes instability in the molecule's structure due to the loss of an electron. This eventually leads to the fragmentation or breaking of some bonds in the molecule. The fragmentation occurs predominantly at specific bonds to yield relatively stable fragments. One type of fragmentation pattern is the cleavage of a single bond in the molecular ion. The cleavage leads to a radical and a cation. The cleavage can occur at...
09:51
Purification of a High Molecular Mass Protein in Streptococcus mutans
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2019
Described here is a simple method for the purification of a gene product in Streptococcus mutans. This technique may be advantageous in the purification of proteins, especially membrane proteins and high molecular mass proteins, and can be used with various other bacterial species.
FAQs
A molecular formula supplies the atom counts needed for the calculation. Each element’s atomic mass is matched to its symbol, multiplied by the number indicated for that element, and then combined with the contributions from all other atoms. This makes the formula a direct quantitative link between molecular composition and calculated mass.
Atoms of the same element can occur with different isotopic compositions, and those differences affect the mass assigned to a molecule. Consequently, a measured molecular mass may depend on which isotopes are present, rather than only on the element symbols and atom counts. Isotopic composition therefore matters when comparing calculated and measured values.
The numerical value used for molecular mass in unified atomic mass units corresponds to the numerical value of molar mass when the latter is expressed in grams per mole. The units and chemical meaning differ, but this correspondence lets chemists move between molecular-scale descriptions and quantities used for laboratory measurements and stoichiometric calculations.
First, list each element in the formula and identify its atomic mass. Next, multiply each atomic mass by that element’s indicated atom count. Finally, add all resulting contributions and report the total in unified atomic mass units. Checking every symbol and subscript helps prevent omissions or incorrect weighting of elements.
Molecular mass connects a chemical formula with measurable quantities used in stoichiometry. After calculating it, chemists can use the corresponding molar-mass value in grams per mole to relate amounts of a substance to its formula composition. This supports quantitative calculations in which molecular identity and measured material amounts must be considered together.
In molecular formula analysis, a calculated value provides a mass associated with a proposed composition, allowing that formula to be considered against measured information. In mass spectrometry, molecular mass helps interpret mass-related data from molecules. Isotopic composition must also be considered because it can influence the mass observed experimentally.