Prerona, a graduate in chemistry, is a final year PhD student at the Indian Institute of Science Education and Research (IISER) Pune working with Prof. Harinath Chakrapani. Her work focuses on the development of stimuli-responsive small molecule persulfidating agents.

Discovering the researcher within
Some minds are just passionately curious and for such people, getting into a PhD program happens organically. What is your story?

I have always wanted to study pure sciences but I was not certain if I ever wanted to do a PhD. In fact, during my Masters, I was preparing for GATE and was more inclined to get a job thereafter. However, during my second year, I got selected as a Summer Research Fellow at JNCASR, Bangalore under their Summer Research Fellowship Program (SRFP). Those 2 months I believe was the turning point in my career. I enjoyed working in the lab, troubleshooting and solving problems. It was equally exhausting and I faced more failures than success- the project I was working on never took off. It is quite intriguing that I never meant to come to IISER Pune for an interview. It just happened by chance that I was already in Mumbai and took a last-minute decision to come and appear for the interview. I already had offers in hand by then but after my initial interactions, I was really impressed with the work environment here. It is a small, well-knit campus and I was quite interested in the research work of 2-3 professors in the department here. Although IISER Pune only assigns your supervisors after getting admitted into the program, I had shortlisted 3-4 labs based on my research interest, hoping that I would at least get one of those. And lucky for me, it did work in my favor.

Big picture of your research
What challenges are driving your research within that larger question? How is your research making an original contribution to your field?

We have all heard about hydrogen sulfide (H2S), did experiments with H2S in our high school science courses. However, we have always learnt that H2S is a toxic gas and an environmental pollutant. Little did we know that H2S indeed plays a very crucial role in cellular signalling processes and such gaseous signalling molecules are known as gasotransmitters. One of the mechanisms by which H2S elicits its effects is by modifying cysteine residues (-SH) in proteins to form a persulfide (-SSH), a process commonly known as persulfidation. Persulfidation of proteins has been associated with the pathophysiology of various neurodegenerative diseases such as Alzheimer’s and Parkinson’s, aging, regulation of inflammation, countering oxidative stress, etc. However, it appears that H2S due to its redox constraints can induce this modification only under certain conditions. Whereas, small molecule persulfides (RSSH) can directly induce persulfidation and are reported to be more efficient than H2S. Furthermore, RSSH are superior reductants compared to its thiol counterpart (RSH) and are recognized as important intermediates in mitigating oxidative stress. Therefore, persulfides have assumed importance as therapeutic agents and strategies to enhance persulfides in cells are in development. Given persulfides are not stable in the biological milieu and might decompose before its entry into cells, we have developed two distinct strategies for the generation of persulfides. The first one involves the masking of a persulfide moiety with groups that can be deprotected by a biologically relevant stimulus resulting in the generation of a persulfide. Although these compounds are useful, certain limitations are owing to their complex synthetic protocols and short shelf-life. Therefore, we have developed an alternate strategy that does not contain a persulfide moiety but can generate persulfides in cells. 3-mercaptopyruvate sulfurtransferase (3-MST) is an enzyme involved in the trafficking of sulfur and operates by forming a persulfide at its active site. We have developed artificial substrates for the enzyme, which upon efficient turnover by the enzyme generates a persulfide, is cell-permeable and it was found to exhibit antioxidant and anti-inflammatory effects. Together, these approaches will serve as vital tools in elucidating the role of persulfides in cellular signalling processes.

 

 

All-important student-advisor relationship
The healthy sound student-advisor relationship is the basis for good performance and success of any such research collaboration. How is your experience working with your PhD advisor?

It is indeed very important to have a healthy relationship with your supervisor, they are the ones who will see you through till the end of your journey. I am extremely grateful to be working with someone who has always been approachable, encouraging and supportive of my work and my decisions. Undoubtedly, we have had our share of disagreements but we have always managed to talk through it and find an amicable solution. I believe, being open and honest about my expectations, abilities and work has helped us get along pretty well. However, like any other relationship, there aren’t set rules, we just need to read the situation and act accordingly.

Best Bits, Worst Bits
Embarking PhD is a big undertaking. The journey sees it all: Highways, side roads, and dead ends. So far, what have been the hardest and most rewarding moments of your PhD?

The most difficult phase has been the initial 2 years of my PhD journey. Almost every project I had been working on then resulted up in dead ends. But that is how research works, not every project works, not every experiment yields satisfactory results. As the saying goes, what does not kill you makes you stronger. Although the projects did not take off as expected, it was a huge learning curve for me. The failures, experiences and skills I had acquired from it helped me design and execute my next project. And that was the best bit in my PhD, the one that came after the worst bit. Your first publication is always special but it is extra special when it comes after a series of failures. Yes indeed, I did have a satisfying PhD experience and it did turn out as expected. Although, sometimes I do feel I could have performed better in certain aspects, learn more skills and hone the existing ones. I believe everyone feels that way, as you gather more experience, you tend to recount the things you could have done differently to obtain better outcomes. As my supervisor says, I am too critical of everything, myself included.