Alkenone Unsaturation Index
Alkenone Unsaturation Index - Related Videos
10:10
An Overview of Alkenone Biomarker Analysis for Paleothermometry
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2023
Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst Throughout this series of videos, natural samples were extracted and purified in search of organic compounds, called biomarkers, that can relate information on climates and environments of the past. One of the samples analyzed was sediment. Sediments accumulate over geologic time in basins, depressions in the Earth into which sediment flows through the action of fluid (water or air), movement, and gravity. Two main types...
02:05
Degree of Unsaturation
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2025
The degree of unsaturation (U), or index of hydrogen deficiency (IHD), is defined as the difference in the number of pairs of hydrogen atoms between the compound and the acyclic alkane with the same number of carbon atoms. Each double bond or ring costs two hydrogen atoms compared to a saturated analog and results in one degree of unsaturation. The degree of unsaturation for hydrocarbons is U = (2C + 2 − H) / 2, where C is the number of carbon atoms and H is the number of hydrogen atoms. For...
09:10
Experimental Protocol for Biodiesel Production with Isolation of Alkenones as Coproducts from Commercial Isochrysis Algal Biomass
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Cited by 8 •
2016
Detailed methods are presented for the production of biodiesel along with the co-isolation of alkenones as valuable coproducts from commercial Isochrysis microalgae.
13:16
A Whole Cell Bioreporter Approach to Assess Transport and Bioavailability of Organic Contaminants in Water Unsaturated Systems
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Cited by 5 •
2014
A whole cell bioreporter assay with Burkholderia sartisoli RP037-mChe was developed to detect fractions of an organic contaminant (i.e., fluorene) available for bacterial degradation after active transport by mycelia bridging air-filled pores in a water unsaturated model system.
01:09
Conjugate Addition to α,β-Unsaturated Carbonyl Compounds
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2025
α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in the molecule leads to three resonance structures. The hybrid form exhibits two probable electrophilic sites: the carbonyl carbon and the β carbon. A simple nucleophilic attack at the carbonyl center results in an alkoxy intermediate, which gives the direct or 1,2-addition product upon further protonation. When the nucleophile attacks the β carbon, it...
FAQs
Marine haptophyte algae modify the proportion of unsaturated alkenones as their growth temperature changes. Warmer conditions are associated with a higher relative contribution of the di-unsaturated C37:2 compound compared with the tri-unsaturated C37:3 compound. Consequently, the UK′37 ratio rises, providing a temperature-related signal that can be preserved in environmental samples.
The calculation uses the concentrations of two C37 alkenones: the di-unsaturated C37:2 compound and the tri-unsaturated C37:3 compound. UK′37 is obtained by dividing C37:2 by the combined concentration of C37:2 and C37:3. Because the result is based on relative abundance, the index emphasizes composition rather than the total amount of alkenone material.
A concentration measurement describes how much alkenone material occurs in a sample, whereas the unsaturation index compares the relative amounts of specific C37 compounds. That distinction allows UK′37 to track the algae’s temperature-responsive molecular composition. Researchers can therefore use the ratio to estimate sea-surface temperature even when the overall quantity of alkenones varies among samples.
Researchers analyze alkenones recovered from marine sediments or suspended particles and determine the concentrations of the relevant C37 compounds using chromatographic methods. The measured C37:2 and C37:3 abundances are then inserted into the UK′37 equation. This workflow converts molecular composition into a temperature-related index suitable for environmental and geological investigations.
UK′37 measurements support reconstructions of past and present sea-surface temperatures. Applied to marine sediments, they help investigate climate variability and environmental change over geological timescales. Measurements from suspended particles provide information from material currently present in the marine environment, extending the proxy’s use beyond long-term sedimentary records.
Marine sediments preserve alkenones produced by marine haptophyte algae, allowing their molecular composition to be examined after deposition. By measuring the C37:2 and C37:3 compounds in sediment samples, researchers can derive UK′37 values and reconstruct ocean-temperature conditions represented by the sediment record. This makes the index useful for studying changes across geological timescales.