Jiggling and wiggling of atoms!

Last week I was talking to my dad and suddenly from nowhere he asked me “What do you do in your PhD? “ and the comic series that circulates on Facebook about what other people think you do in your profession  flashed on my mind.  After a brief moment I recovered myself and told him “I do research dad…””Okay on what?” “Spectroscopy “I said in style! I still sensed some questions in his silence. Dad this one is for you… 🙂

Grad Students

Haha…May be I could change what my mum thinks i should do with….:p …you know what… 🙂

When I first started to work with my adviser Dr. Nancy Pleshko, in 2009, I had never heard of spectroscopy so I googled it and found this interesting quote.  “…Everything that living things do can be understood in terms of the jiggling and wiggling of atoms…” by Richard Feynman. Such an apt description of spectroscopy! …and this is how I fell in love with it… 🙂  Infrared spectroscopy is an analytic method which is based on the vibrations of atoms in a molecule. On electromagnetic spectrum infrared region lies between microwave and visible region. When an Infrared source is passed through a sample, Infrared (IR) electromagnetic radiation causes vibrations in molecules. There are different types of vibrations such as stretching, bending, scissoring and rocking. Molecules absorb the frequencies which are characteristic to their structure and we get a spectrum.

You can consider this spectrum as a fingerprint of the sample.  Unique!!! And what does this spectrum tell us about the sample???  It tells us what are the components of the sample and in what quantity they are present in the sample. Samples can be in any form such as liquid, solid or gas!  Spectroscopic technique can be used to characterize, identify unknown sample, monitor chemical reactions and in pharmaceutical companies it is often used to quality control.

Mid-IR spectrum from ligament

Mid-IR spectrum from ligament

In this part I will explain why we use spectroscopy in my research. All biological tissues are made up of (roughly) proteins, sugar, lipids and water and all these components change with the initiation and during the disease.  Traditionally these changes in the tissues are studied with the help of histology. In this technique, normal and diseased tissues are embedded in paraffin and sectioned at 5-7µ and stained with appropriate stain. These tissues are then looked under microscope to understand the changes between normal and diseased tissue. But there are limitation to this method. The stains can be used for specifically one component at a time. So if you want to look at protein content you will use one stain and for sugar other. This method is an invasive method. That means if you want to look at cancerous versus normal tissue, you have to take a biopsy to get the tissue for histology.  Infrared spectroscopy is a nice tool to look at the biological tissues too. Proteins, sugar, lipid and water have absorbance in mid and near infrared range.  Infrared spectroscopy is sensitive to chemical composition and molecular structure. Infrared spectroscopy requires minimum sample preparation and it is possible to get all information about the tissue by looking at one spectrum.  Also there are fiber optic probes of infrared which make data acquisition noninvasive.

In my coming bogs I will discuss how spectroscopy has been used in different fields.

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