Brownian Carnot engine

The Carnot cycle imposes a fundamental upper limit to the efficiency of a macroscopic motor operating between two thermal baths. However, this bound needs to be reinterpreted at microscopic scales, where molecular bio-motors and some artificial micro-engines operate. As described by stochastic thermodynamics, energy transfers in microscopic systems are random and thermal fluctuations induce transient decreases of entropy, allowing for possible violations of the Carnot limit. Despite its potential relevance for the development of a thermodynamics of small systems, an experimental study of microscopic Carnot engines is still lacking. Here we report on an experimental realization of a Carnot engine with a single optically trapped Brownian particle as working substance. We present an exhaustive study of the energetics of the engine and analyze the fluctuations of the finite-time efficiency, showing that the Carnot bound can be surpassed for a small number of non-equilibrium cycles. As its macroscopic counterpart, the energetics of our Carnot device exhibits basic properties that one would expect to observe in any microscopic energy transducer operating with baths at different temperatures. Our results characterize the sources of irreversibility in the engine and the statistical properties of the efficiency -an insight that could inspire novel strategies in the design of efficient nano-motors.Comment: 7 pages, 7 figure

Engineered swift equilibration of a Brownian particle

A fundamental and intrinsic property of any device or natural system is its relaxation time relax, which is the time it takes to return to equilibrium after the sudden change of a control parameter [1]. Reducing $tau$ relax , is frequently necessary, and is often obtained by a complex feedback process. To overcome the limitations of such an approach, alternative methods based on driving have been recently demonstrated [2, 3], for isolated quantum and classical systems [4--9]. Their extension to open systems in contact with a thermostat is a stumbling block for applications. Here, we design a protocol,named Engineered Swift Equilibration (ESE), that shortcuts time-consuming relaxations, and we apply it to a Brownian particle trapped in an optical potential whose properties can be controlled in time. We implement the process experimentally, showing that it allows the system to reach equilibrium times faster than the natural equilibration rate. We also estimate the increase of the dissipated energy needed to get such a time reduction. The method paves the way for applications in micro and nano devices, where the reduction of operation time represents as substantial a challenge as miniaturization [10]. The concepts of equilibrium and of transformations from an equilibrium state to another, are cornerstones of thermodynamics. A textbook illustration is provided by the expansion of a gas, starting at equilibrium and expanding to reach a new equilibrium in a larger vessel. This operation can be performed either very slowly by a piston, without dissipating energy into the environment, or alternatively quickly, letting the piston freely move to reach the new volume

The use of fluoroproline in MUC1 antigen enables efficient detection of antibodies in patients with prostate cancer

A structure-based design of a new gene22ration tumor-associated glycopeptides with improved affinity against two anti-MUC1 antibodies is described. These unique antigens feature a fluorinated proline residue, such as a (4S)-4-fluoro-L-proline or 4,4-difluoroproline, at the most immunogenic domain. Binding assays using bio-layer interferometry reveal 3-fold to 10-fold affinity improvement with respect to the natural (glyco)peptides. According to X-ray crystallography and MD simulations, the fluorinated residues stabilize the antigen-antibody complex by enhancing key CH/ interactions. Interestingly, a notable improvement in detection of cancer-associated anti-MUC1 antibodies from serum of patients with prostate cancer is achieved with the non-natural antigens, which proves that these derivatives can be considered better diagnostic tools than the natural antigen for this type of cancer.We thank the Ministerio de Economía y Competitividad (projects CTQ2015-67727-R, UNLR13-4E-1931, CTQ2013-44367-C2-2-P, CTQ2015-64597-C2-1P, and BFU2016-75633-P). I. A. B. thanks the Asociación Española Contra el Cancer en La Rioja for a grant. I. S. A. and G. J. L. B. thank FCT Portugal (PhD studentship and FCT Investigator, respectively) and the EPSRC for funding. G. J. L. B. holds a Royal Society URF and an ERC StG (TagIt). F.C. and G. J. L. B thank the EU (Marie-Sklodowska Curie ITN, Protein Conjugates). R.H-G. thanks Agencia Aragonesa para la Investigación y Desarrollo (ARAID) and the Diputación General de Aragón (DGA, B89) for financial support. The research leading to these results has also received funding from the FP7 (2007-2013) under BioStruct-X (grant agreement N°283570 and BIOSTRUCTX_5186). We thank synchrotron radiation source DIAMOND (Oxford) and beamline I04 (number of experiment mx10121-19). Hokkaido University group acknowledges to JSPS KAKENHI Grant Number 25220206 and JSPS Wakate B KAKENHI Grant Number 24710242. We also thank CESGA (Santiago de Compostela) for computer support

Climate adaptation and agriculture: Solutions to successful national adaptation plans

The purpose of this brief is to share insights on agriculture and NAPs with national-level decision makers in developing countries and Least Developed Countries (LDCs), multilateral agencies, UNFCCC negotiators and donors. This brief explores how countries are overcoming the biggest challenges in developing NAPs, outlines examples of successful cross-sector adaptation planning, explores influence and leverage necessary for successful NAP processes, and offers specific recommendations

Investigating the coenzyme specificity of phenylacetone monooxygenase from Thermobifida fusca

Type I Baeyer–Villiger monooxygenases (BVMOs) strongly prefer NADPH over NADH as an electron donor. In order to elucidate the molecular basis for this coenzyme specificity, we have performed a site-directed mutagenesis study on phenylacetone monooxygenase (PAMO) from Thermobifida fusca. Using sequence alignments of type I BVMOs and crystal structures of PAMO and cyclohexanone monooxygenase in complex with NADP+, we identified four residues that could interact with the 2′-phosphate moiety of NADPH in PAMO. The mutagenesis study revealed that the conserved R217 is essential for binding the adenine moiety of the nicotinamide coenzyme while it also contributes to the recognition of the 2′-phosphate moiety of NADPH. The substitution of T218 did not have a strong effect on the coenzyme specificity. The H220N and H220Q mutants exhibited a ~3-fold improvement in the catalytic efficiency with NADH while the catalytic efficiency with NADPH was hardly affected. Mutating K336 did not increase the activity of PAMO with NADH, but it had a significant and beneficial effect on the enantioselectivity of Baeyer–Villiger oxidations and sulfoxidations. In conclusion, our results indicate that the function of NADPH in catalysis cannot be easily replaced by NADH. This finding is in line with the complex catalytic mechanism and the vital role of the coenzyme in BVMOs