Fractional Abundance
Fractional Abundance - Related Videos
10:09
Fractional Distillation
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2023
Source: Laboratory of Dr. Nicholas Leadbeater — University of Connecticut Distillation is perhaps the most common laboratory technique employed by chemists for the purification of organic liquids. Compounds in a mixture with different boiling points separate into individual components when the mixture is carefully distilled. The two main types of distillation are "simple distillation" and "fractional distillation", and both are widely used in organic chemistry laboratories. Simple distillation...
10:34
Quantification of the Abundance and Charging Levels of Transfer RNAs in Escherichia coli
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Cited by 13 •
2017
Here we present a method for directly measuring transfer RNA charging levels from purified Escherichia coli RNA as well as a way to compare relative levels of transfer RNA, or any other short RNA, across different samples based on the addition of spike-in cells expressing a reference gene.
12:47
Chromatin Immunoprecipitation (ChIP) Protocol for Low-abundance Embryonic Samples
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Cited by 5 •
2017
Here, we describe a chromatin immunoprecipitation (ChIP) and ChIP-seq library preparation protocol to generate global epigenomic profiles from low-abundance chicken embryonic samples.
07:09
Purification of Low-abundant Cells in the Drosophila Visual System
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2018
Here, we present a cell dissociation protocol for efficiently isolating cells present at low abundance within the Drosophila visual system through fluorescence activated cell sorting (FACS).
07:57
Using the GELFREE 8100 Fractionation System for Molecular Weight-Based Fractionation with Liquid Phase Recovery
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Cited by 17 •
2009
The accompanying video describes the use of the GELFREE 8100 Fractionation System, which partitions complex protein samples on the basis of molecular weight and recovers the fractions in liquid phase. The video describes how the technology works, how it is used, and provides resultant data, with polyacrylamide gel electrophoresis analysis of fractionated bovine liver homogenate.
FAQs
Dividing by the total atom count normalizes an isotope’s contribution to the whole sample. This produces a proportion that can be compared across samples containing different numbers of particles. Because the result is expressed as a decimal or fraction, it can also be used directly as a weighting factor in atomic-mass calculations without first converting from percent.
Each isotope mass contributes according to its fractional abundance, so more abundant isotopes exert a greater influence on the calculated atomic mass. The calculation multiplies every isotope’s mass by its corresponding fraction and combines those contributions. Consequently, the result reflects the sample’s isotopic composition rather than the mass of only one selected isotope.
The two forms express the same isotopic composition but use different numerical scales. Fractional abundance remains in decimal or fraction form, whereas multiplying it by 100 gives percent abundance. The fractional form is especially convenient when weighting isotope masses, while the percentage form can make the relative representation easier to communicate in isotope-analysis results.
First identify the number of atoms belonging to the isotope of interest, then determine the total number of atoms represented in the sample. Divide the isotope count by that total to obtain the fractional value. If a percentage is needed for reporting, multiply the fraction by 100, keeping the calculation tied to the same sample.
An element’s reported atomic-weight value must account for the relative presence of its isotopes rather than treating every isotope as equally important. Fractional abundances supply the weighting factors for that calculation. This allows atomic-weight data to represent natural isotopic composition and explains why the value may differ from the mass of any single isotope.
In mass spectrometry and isotope analysis, fractional abundance provides a quantitative way to describe how much of a sample is associated with a particular isotope. Those proportions can be combined with isotope masses to interpret atomic-weight data and perform chemical calculations. The concept therefore connects measured isotopic composition with numerical descriptions of the sample.