Zernike seminar: Dr. Ricardo P. Martinho "Using NMR to interrogate polyelectrolytes: from composition upon complexation to ion binding phenomena"

Polymeric charged particles are ubiquitous in biological systems, being associated with the phenomenon of liquid-liquid phase separation. The electrostatic interactions between negatively charged polynucleic acids and positively charged

proteins leads in turn to the formation of membraneless organelles. These are known to be associated with formation of life but also with numerous diseases. In order to understand these systems in a controlled environment, we have

performed systematic studies with different synthetic polyelectrolytes. When aqueous solutions of oppositely charged polyelectrolyte are mixed in aqueous solutions, an entropically driven phase separation occurs, yielding

a dense polymeric phase and a dilute aqueous phase. In this work, we have developed a multinuclear NMR methodology to quantify the distribution of the different components in the mixtures, both organic (polymers) and

inorganic (counterions). We have obtained insights into specific ion binding between counterions and polyelectrolytes. We have further explored this in pH-dependent polyethyleneimine and how this is correlated

with its pH titration behavior.