I’m a Project Leader working at the Max Planck Institute for the Physics of Complex Systems (MPI-PKS, Dresden, Germany) in the Biological Physics Division.
My two main research interests are stochastic thermodynamics and biophysics. I study the thermodynamic properties of processes that take place in the microscopic world, where the dynamics is strongly affected by thermal fluctuations. My work on non-equilibrium thermodynamics provides novel insights on the fluctuations of biological processes that occur at mesoscopic scales, such as RNA transcription, spontaneous otoacoustic emissions and cell-fate decisions. I have also participated in several applications in micro and nano-engineering with the construction of colloidal heat engines and information engines using optical tweezers.
I currently work in collaboration with the Max Planck Institute for Cell Biology and Genetics (MPI-CBG, Dresden, Germany), the Biotechnology Center (BIOTEC, Dresden, Germany), the Vodafone Chair of Mobile Communication Systems (Dresden, Germany) and the Center for Advancing Electronics Dresden. I’m member of Grupo Interdisciplinar de Sistemas Complejos (GISC, Madrid, Spain).
GRC Prize for excellent poster presentation
I received the GRC Prize for excellent poster presentation in the prestigious Gordon Research Conference ``Stochastic Physics in Biology``, which took place in Ventura (California) on 8-13 Jan 2017.
The prize was awarded for my poster contribution entitled ¨Decision Making in the Arrow of Time¨ (coauthored with Izaak Neri, Meik Dörpinghaus, Heinrich Meyr and Frank Jülicher).
2017 Emerging Investigators
Soft Matter dedicates a special collection to the recent work of leading researchers in the field who are in the earlier stages of their careers. The collection showcases both experimental and theoretical work from around the globe and features investigations across a wide diversity of soft materials, including polymers, liquid crystals, nanoparticles, foams, emulsions and biological matter.
In the 2017 edition, the collection Emerging Investigators recognizes our work with the publication of our review article on colloidal heat engines.
I. A. Martínez, É. Roldán, L. Dinis, and R. A. Rica
Soft Matter 13 (1), 22-36 (2017)
Decision Making in the Arrow of Time
Irreversibility is a hallmark of nonequilibrium processes. It implies that time reversal invariance of microscopic equations of motion is broken at meso and macro scales. Here we show that the degree of irreversibility of a physical process can be quantified by the time it takes an observer to decide whether a movie of the process runs forward or in reverse.
We derive an exact relation between the average entropy production rate and the minimal mean decision time. We also show that entropy production can be estimated from mean first-passage times of suitable observables and introduce a novel fluctuation theorem for the decision time distributions.
É Roldán, I Neri, M Dörpinghaus, H Meyr, and F Jülicher
PRL 115 (25), 250602 (2015)
Mechanisms of backtrack recovery by RNA polymerases I and II
Transcription of the genetic information from DNA into RNA is the central process of gene expression, and it is performed by enzymes called RNA polymerases (Pol). Transcription is interspersed with a proofreading mechanism called backtracking, during which the polymerase moves backward on the DNA template and displaces the RNA 3′ end from its active site.
Here we show that backtrack recovery results from a kinetic competition between diffusion of the enzyme along the DNA and cleavage of the backtracked RNA.
Using single-molecule experiments and stochastic theory, we quantify distinct diffusion and cleavage rates of Pol I and Pol II and described distinct backtrack recovery strategies of these essential enzymes.
A Lisica, C Engel, M Jahnel, É Roldán, EA Galburt, P Cramer, and SW Grill
PNAS 113 (11), 2946-2951 (2016)
Brownian Carnot Engine
Sadi Carnot is considered the father of thermodynamics. In his seminal work “Reflexions sur la puissance motrice du feu” Carnot studied the conversion of heat into work by thermal engines operating cyclically. Carnot found an optimal protocol called later the Carnot cycle : any heat engine operating between two thermal baths cannot be more efficient than the Carnot cycle.
Despite being the basis of thermodynamics, an experimental realization of the Carnot cycle has been elusive to experimentalists during almost two centuries.
Using an optically-trapped microscopic sphere in water, we have recently realized the first Carnot engine at the microscale. In our experiment, the microscopic particle is the working substance and the optical trap plays the role of the piston in a classical engine. The temperature of the particle is changed in time using external noisy electrostatic fields. By concatenating a series of isothermal and microadiabatic protocols (where the entropy of the particle remains constant in time), our microscopic engine attains Carnot efficiency when driven quasistatically. We also show that under nonequilibrium driving, the Brownian Carnot engine can transiently surpass Carnot efficiency. We also test a plethora of novel theoretical results on stochastic efficiency.
IA Martínez, É Roldán, L Dinis, D Petrov, JMR Parrondo, and RA Rica
Nature Physics 12, 67-70 (2015)
Universal features in the energetics of symmetry breaking
A breaking of symmetry involves an abrupt change in the set of microstates a system can explore. This change has unavoidable thermodynamic implications: a shrinkage of the microstate set results in an entropy decrease, which eventually needs to be compensated by heat dissipation and hence requires work. On the other hand, in a spontaneous symmetry breaking, the available phase-space volume changes without the need for work, yielding an apparent entropy decrease.
Here we show that this entropy decrease is a key ingredient of a Szilard engine and Landauer’s principle, and perform a direct measurement of the entropy change along symmetry-breaking transitions for a Brownian particle subject to a bistable potential realized through two optical traps. The experiment confirms theoretical results based on fluctuation theorems, enables the construction of a Szilard engine extracting energy from a single thermal bath, and shows that a signature of a symmetry breaking in a system’s energetics is observable.
É Roldán, IA Martinez, JMR Parrondo, and D Petrov
Nature Physics 10, 457-461 (2014)
Springer Theses Prize
I received the Springer Theses Award which recognizes outstanding PhD research. My PhD Thesis “Irreversibility and Dissipation in Microscopic Systems” supervised by Juan M.R. Parrondo was published as a book in the Springer Theses series.
É Roldán, Irreversibility and Dissipation in Microscopic Systems, Springer 2014