Science and Technology
By Nicole Soussana, Contributing Writer
During my first summer as an undergraduate at Stern, I decided to spend my time with Dr. Ran Drori, Professor of Organic Chemistry and Biochemistry at Stern College for Women, in order to receive firsthand experience of life as a researcher.
Upon entering Stern, I planned to attend medical school, like mostly everyone else. Over the course of two semesters, my plans have transitioned from an intended MD to PhD. This means that rather than going to medical school and become a practicing doctor, I have shifted gears to instead enter a field that would further my understanding of the world of science, in addition to becoming part of a community dedicated to enhancing the breadth of scientific knowledge. While this sounds like a great feat, I wanted to experience life in research before solidifying my decision. My summer in Dr. Drori’s lab helped me reach this intention.
Dr. Drori’s lab focuses on antifreeze proteins (AFPs). These proteins play a vital role in the survival of cold-environment organisms by stunting the growth of ice within them. Due to the effects of antifreeze proteins, ice crystals can exist within the organisms without causing harm, because ice growth is inhibited. AFPs are present in many organisms living in freezing temperatures, such as fish, insects, bacteria, plants, and fungi. Like most occurences in science, these magnificent proteins are not as simple as they sound.
Pure water melts at just above zero degrees celsius and freezes just below zero. There is practically no gap between the freezing point and the melting point. However, the basic means of antifreeze proteins is to bind the ice and inhibit its growth. This creates a gap between the melting and freezing points. In this gap, called TH (thermal hysteresis), ice will not grow and will therefore not cause harm to the organisms living in sub-zero temperatures (where ice would have grown if it were not for AFPs). Once the ice crystal in the presence of AFPs reaches the freezing point, the crystal bursts. The story becomes highly complicated when adding various types of antifreeze proteins, degrees of activity, and binding sites to the planes of ice crystals, all of which impacts how and when the ice grows, while also manipulating the temperature.
During my time in Dr. Drori’s lab, the research I conducted was twofold. On the one hand, I focused on the influence that time would play on the TH activity of different AFPs. If you leave the ice crystal at a constant temperature within the TH gap, will this give an opportunity for more AFPs to bind, thereby increasing the TH activity? We concluded that the impact of time on TH activity would depend on the protein. For AFPI, which is found in flounders, there was no observed change of TH activity as time increased, even with varying concentrations. However, with a more active protein, QAE, found in eelpouts, differing concentrations displayed an increase in TH activity with time. The basic explanation for this occurrence is the different ways the proteins bind to ice. QAE specifically causes sharper tips on the crystal with the increase of time, which increased the TH.
The other aspect of my research involved comparing the ice crystal shape as it is formed to just before it bursts. If it is found that the crystal shape becomes sharper before burst, it could explain an increase in TH activity. The sharpness of the ice crystal displays how efficiently the AFP is inhibiting ice growth. The sharper the tips of an ice crystal, the further growth is being inhibited. Once the rate of ice growth is faster than the AFP binding, the crystal will burst.
While the bulk of my time doing research happened to be very tedious, repetitive, and included many failures along the way, I learned that this is the path every researcher follows. The work leading up to a discovery or even just to the step which will lead to a discovery, is extremely hard and taxing, but at the end of the day, when you discover a small nuance or some small reaction that wasn’t expected or a clue leading you to your final answer, it is more than gratifying.