Science Stuck in the Middle: Lasers, Diamonds, and DNA, Oh My!

by Richelle Teeling-Smith

What does it mean to do ‘interdisciplinary’ research? Sometimes in research, you might find that your path to solving a specific problem leads you outside the traditional boundaries of the field you set out to study. That’s how my graduate school experience has gone and I’m not the only one!

I’m a fifth year graduate student at the Ohio State University and I am studying physics. However, unlike most graduate students, I work for three different advisors with three different specialties. All of us are technically in physics, but our work takes us outside of physics on a daily basis. I study the dynamics of single biomolecules, like DNA. I look at how DNA moves using a tool called nitrogen-vacancy (or NV) diamond. My work involves lasers, DNA, diamonds, gold, and magnetic resonance. I use physics, biology, chemistry, and engineering on a daily basis. Yes, it is as cool as it sounds!

Why are scientists so interested in studying the dynamics of single biomolecules? Who cares how a single molecule (like DNA) moves? Single-molecule measurements are becoming more and more popular in biophysics, biology, and biochemical and biomedical engineering because they allow us to clarify and better understand important biochemical processes such as protein-DNA interactions (transcription and translation), protein folding, and the functions of membrane proteins – and much more!

It’s important to look at a single molecule because so much information can be lost in measuring a large number of molecules together. If you take a pipette and suck up some small volume of your sample, you have moles of molecules! We’re talking 1023 molecules. That’s 23 zeros! When you measure a large ensemble you are averaging over the whole group and you lose important information. Imagine you are an alien studying the planet Earth. You want to understand the life forms that live on Earth and you take one snapshot that averages over all humans on Earth. What do you see? First off, this human is half male and half female. Weird right? Now what do they look like on the outside? Do they have hair? What color?  How tall are they? You get my point? One averaged human does not do a great job of representing us accurately.  Single-molecule measurements of these complex biological systems have allowed us to get a much more accurate and detailed view of what is going on in our bodies!

So why diamond?  And what do lasers have to do with this?

NV diamond is really a great tool. Have you ever heard of colored diamonds? Diamonds can be blue, yellow, or pink. These colors are caused by impurities in the diamond crystal. Normally, diamond is composed of carbon atoms arranged in a tetrahedral lattice structure. However, if you replace or remove some of these carbon atoms in a specific way, you can change the optical and electrical properties of diamond.

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Pink Nitrogen-Vacancy Diamond (image by Young Woo Jung)

NV diamond involves just that. One carbon atom is replaced by a nitrogen atom. Adjacent to that, one carbon atom is removed altogether to leave a gap in the lattice. These atoms form the NV center. This is what makes the NV diamond pink!

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Nitrogen-vacancy centers in the carbon diamond lattice. Nitrogen atoms are yellow, the vacancies are transparent, and the bond between the N-V is highlighted in pink. (Image by Young Woo Jung)

NV diamond has the unique electrical property that if you shine a laser on it, it will fluoresce. This means that it emits red photons. It glows red. No really… And NV diamond is a good measurement tool because this fluorescence can be controlled by external magnetic fields and microwaves. This is called magnetic resonance. We apply energy (in the form of microwaves) to the NV diamond sample. I use gold waveguides to do this.

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Gold waveguide (fabricated on a glass slide) and soldered to a copper mount to create a microwave circuit. 8 flow channels are placed across the microwave channel. This is where the DNA experiment is housed. (Design and image by Richelle Teeling-Smith)

I design a very intricate pattern in gold that controls the path and intensity of the traveling microwaves. At very specific frequencies, the diamond absorbs the microwave energy. This causes the electrons in the diamond to change their quantum state and ‘go dark’. You control the ‘dark’ frequencies of the diamond by applying magnetic fields to the sample. People have used this to measure small magnetic fields, or even measure a single electron and nuclear spin. This is the tool that allows us to track the dynamics of a single biomolecule in a magnetic field.

In the process of conducting this interdisciplinary experiment, I have had to become a jack-of-all-trades. I engineered and built my own microscope for imaging this diamond-DNA sample. This required learning how to design and utilize both the hardware and software needed to take this measurement. I’ve learned electrical engineering, mechanical engineering, and coding through trial and error.   I also design and fabricate my own waveguides (to supply the microwaves to the sample).   I’ve even become a bit of a biologist and a chemist. Biophysics is an inherently interdisciplinary field, as Morgan Bernier pointed out in her post.  To create my sample, I had to learn the chemistry and biology necessary to attach a single molecule of DNA to a piece of glass on the microscope objective, and also to attach a single nanometer-sized diamond to the other end of the DNA molecule.

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Schematic of the NV-nanodiamond attached to the end of a single DNA molecule. This experiment is conducted in a ‘flow channel’ where we house the DNA in solution and apply magnetic and microwave fields. (Design and image by Richelle Teeling-Smith)

This project is highly interdisciplinary. I regularly pull from the expertise of each of my three advisors (magnetic resonance measurements, optics and lasers, and biophysics) and I have had to teach myself a wide array of new skills to conduct this experiment. But as scientists move forward and push the boundaries of the incredibly small, incredibly large, and imperceptibly fast, research is by necessity becoming more and more interdisciplinary. More and more often, the solutions to our problems are beyond the scope of a single discipline and require specialized knowledge from multiple fields. Thinking across boundaries, and a willingness to take on any new challenge to solve a problem, are two important skills that will allow us to develop innovative solutions to our research problems.

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About Richelle Teeling-Smith

BlogPost_biophotoI grew up in Akron, Ohio.  I am the first woman in my family to earn a bachelor’s degree in any field.  I went to college at Kent State University in Kent, OH, and didn’t decide to go into physics until my sophomore year.  I graduated in 2009 with my B.S. and now attend The Ohio State University.  In 2011 I earned my M.S. in physics and I am now working on finishing my Ph.D.  I do research in experimental condensed matter physics and biophysics.  I study the dynamics of bio-molecules, like DNA, using impurity centers in diamonds. I am also a mother to a beautiful little girl.

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