Gradinaru, Claudiu

Research

One of the defining characteristics of a living system is the ability of even the most intricate of its molecular components to self-assemble into functional states. Understanding the complex relationship between the amino acid sequence of a protein and its three-dimensional shape is a major challenge in biophysics. Protein folding is inherently a heterogeneous process because of the vast number of microscopic pathways that connect the myriad of unfolded conformations to the unique native structure. By avoiding averaging, single-molecule methods are uniquely suited to follow individual folding pathways, test and improve the current theoretical models. The research in Prof. Gradinaru’s lab is focused upon developing new modalities for optical spectroscopy studies of single biomolecules. In particular, the goal is to detect simultaneously all fluorescence parameters in order to gain the most complete picture about the chemical environment and the dynamics of specific molecules. Proteins of different size, origin and function are currently studied in vitro under conditions that favour frequent transitions between the folded and the unfolded state(s). The time course of folding can be followed using a combination of resonance energy transfer (FRET) and new environment-sensitive probes. In the cell, protein folding may start at very early stages of peptide synthesis along a narrow tunnel spanning the ribosome, but the characteristic dynamics and conformational changes are still elusive. Multiparameter single-molecule studies will help answer when and how the newly synthesized peptides fold and will also provide the tools to visualize their transient interaction with the ribosome and with the molecular chaperones.