CAREER: Nonlinear Infrared Studies of Biomolecular Coacervation

With support from the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) Program in the Division of Chemistry, Arnaldo Serrano of the University of Notre Dame is using advanced laser-based spectroscopic techniques to investigate protein structure and interactions both in and on the surface of droplets that are composed of distinct phases. Proteins fold into well-defined three dimensional structures 'spontaneously' in biological organisms and are likely involved in cellular organization. The Serrano group is advancing two-dimensional infrared spectroscopy and microscopy methods that can detect changes in protein folding and shape with high sensitivity and specificity. By also using small well-controlled droplets, impacts on protein function and structure can be learned. Discoveries made through this line of experimental inquiry could lead to better understanding of protein structure that could be subsequently modulated to achieve targeted functions. The Serrano group will also engage with other researchers through a regional graduate student workshop on advanced ultrafast spectroscopy and imaging, as well as in the development of an open-source web-based chemical kinetics software platform for undergraduates. The Serrano group will study liquid-liquid phase separation (LLPS) or coacervation using ultrafast infrared spectroscopic tools including two-dimensional infrared (2D-IR) and infrared sum frequency (IRSF) spectroscopies. Organization of building blocks in biological systems such as those that form from proteins during LLPS, are hypothesized to represent a universal mechanism of cellular organization with phase transitions being critical to the level of protein secondary structure and hydration that is locally observed. The chemical physics of proteins and other biopolymers will be studied as new phases form. 2D-IR and IRSF spectroscopies will be used to monitor the in-situ characterization of protein structure, dynamics, and solvation within liquid-liquid phase-separated droplets. The advancement of these spectroscopic tools coupled with LLPS droplet systems has the potential to create new biophysical measurement approaches capable of revealing how phase separation induces variations on the secondary structure and function of proteins. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.