The kinetic states of molecules play a determining role in the metabolic and physiological processes in which they take part. Now, a paper published in the journal Proceedings of the National Academy of Sciences (PNAS) specifies for the first time the levels of energy, the entropy and the enthalpy of protein folding. To do so, the team used a device with optical tweezers that enables changing the experimental temperature between 5ºC and 40ºC.

The study was led by Professor Fèlix Ritort, from the Faculty of Physics and the Institute of Nanosciences and Nanotechnology of the UB (IN2UB). Its first author is the researcher Marc Rico-Pasto (UB) and it counts with the collaboration of teams from the University of Padova (Italy), the Institute of Bioengineering in Lausanne (Switzerland) and the company SpliceBio, whose headquarters are in the Barcelona Science Park.

The emergence of innovative techniques such as optical and magnetic tweezers has revolutionized research in biophysics, and specifically, the study of thermodynamic properties in macromolecules: proteins, nucleic acids, etc. This type of technology enables the manipulation of individual molecules with nanometre precision (10-9 meters) applying forces in the piconewton range (10-12 newtons). Therefore, researchers can characterize the thermodynamic properties of complex biomolecules with unprecedented resolution. The application of such techniques provides with new scenarios for the experimental studies in the field of thermodynamics from a statistical approach, an interpretation of thermodynamics that was only possible from a theoretical perspective to date.

However, these techniques have limitations that prevent researchers from differentiating the origins of the measured forces. At the moment, combining different techniques to expand the number of control parameters is a challenge in biophysics. This is precisely what the team in charge of this study has done: introducing a temperature monitor in the optical tweezers to determine, for the first time, the entropy and enthalpy of protein folding.

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