This Is How We Do It ♫

Julianna Duran, Virginia Tech

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First and foremost, if you didn’t get the reference in the title please click here!

Now that I have educated you on the topic of music, let’s switch to science.

 The Approach: In my previous post I mentioned that I am studying the lipids of Nile Crocodile and Mozambique Tilapia. So the first thing I did is wrestle the reptile like Steve Irwin and hand catch my fish – just kidding, but imagine how cool that would be! My samples were collected from Lake Loskop, South Africa in 2014. Once they were in my possession, here is what I did.

  1. Sample Preparation
    • The muscle tissue samples I received looked like chicken breasts you buy from the grocery store – except the size of a fat bean. These solid chunks need to be turned into a fine powder for me to analyze them. This was done by freezing the sample in the cryomill machine – where the samples were shaken extremely fast and broken up

      Cryomill

      Cryomill

  2. Extraction
    • Think of what happens when you pour oil in water. They go to different ends and don’t mix, right? (Yes) That is exactly what I’m doing with my samples. We are adding lots of chemicals to break down fats into their building blocks: Fatty Acids! The muscle layer (organic layer) hates touching the chemicals, so I take that out and can use it for my next step!
    • Check out a video I made of one of my extractions
  3. Gas Chromatography
    • This instrument is how I will measure the amount of each fatty acid in my samples.
    • How does it work?
      • The sample is injected into the system and enters a narrow glass column. The sample separates in this column based on its weight and boiling point. The particle encounters a flame at the end of the glass, which detects what specific fatty acid it is. The computer then gets this signal and generates a graph showing a fatty acid profile. Each peak on the graph is a different fatty acid, and the height of the peak indicates how much of it there is in the sample.
      • For help envisioning this process, take a look at this video (I used it when I learned about this instrument!)

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        Chromatogram

Summary:

I will be physically and chemically breaking down my samples, then getting fatty acid profiles for each of my individual species. This is all to see if there is a difference between healthy and diseased species and what lipids are most affected by Pansteatitis!


Supported by the Fort Johnson REU Program (NSF DBI-1757899), Dr. Mike Napolitano, Dr. John Bowden, The College of Charleston, NOAA, and NIST. 


References:

CryoMill. https://www.retsch.com/products/milling/ball-mills/mixer-mill-cryomill/function-features/ (accessed Jun 18, 2019).

Gas Chromatography for Fatty Acid Analysis

Jack McAlhany, Wofford College

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In applying to College of Charleston REU at Grice Marine Laboratory, I assumed I would be researching the well-being of a local fishery or the biomechanics of an organism in response to different variables, but this was not the case. My research to this point has not focused on a living organism, but rather tiny portions of blood plasma that we vaporize into a gas to determine the basic constituents of the blood. A solid understanding of chemical structures, or a wild imagination, is necessary for this research because unlike working with live samples, our desired product is not visible. To give you a better understanding, the fatty acids we are detecting have between 8 and 24 carbon atoms while a 70 kg human has approximately 7X10^26 carbon atoms (Kross, B.).

In order to detect such tiny fat molecules I am using a gas chromatography with a flame ionization detector (GC-FID). This instrument converts a liquid sample to a gas that then travels through a 100 meter column with an inert gas carrier. The time at which certain samples exit the column is reproducible, so the retention time in the column is a way to determine which fatty acids are in a blood plasma sample (E.T.S. Laboratories).

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Figure 1: In a GC-FID, a sample (red) is vaporized in a vaporizing column (blue) and an inert gas carrier is the “liquid” phase that carries the vaporized fatty acid methyl ester (FAME) through a 100 meter column (gold). This column has a stationary phase that interacts differently with each FAME, causing the FAME’s to exit the column at different times. The detector responds to compounds that form ions when combusted in the hydrogen-air flame. This response is converted to electrical signals and produce a gas chromatogram we can analyze (E.T.S. Laboratories).

These retention times are represented on a gas chromatogram, which consists of peaks of varying sizes (Figure 2). Each fatty acid interacts in a unique, but constant, way with the stationary phase of the column, so fatty acid peaks are in the same order and have the relatively same retention time every trial. This constant retention time allows us to determine the fatty acid composition of a sample. Not only can we find the blood plasma fatty acid composition, but by analyzing the area under each peak, we can determine the concentration of each fatty acid in the blood. The concentration of each fatty acid or relationships in these concentrations hopefully will provide a biomarker that we can test in the field for the fatty acid disease, pansteatitis.

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Figure 2: Gas Chromatogram of 19 fatty acids. Each peak is labeled with its corresponding fatty acid (Christie W. 2011).

Acknowledgements

I would like to thank the College of Charleston for this internship, the National Science Foundation for funding, and Dr. John Bowden for his guidance as a mentor.

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Works Cited

Christie, W. 2011. Gas Chromatography and Lipids. The Oily Press” Chapter 10.http://lipidlibrary.aocs.org/GC_lipid/10_misc/index.htm

E.T.S. Laboratories https://www.etslabs.com/analysis.aspx?id=$GCP

Kross, B. Questions and Answers. Jefferson Lab. http://education.jlab.org/qa/mathatom_04.html.