Light dependent redox catalysis by Photosystem I complexes encapsulated in organic nanoparticles

Photosystem I (PSI) is a pigment binding multi-subunit protein complexes involved in photosynthesis. PSI is localized in the thylakoid membranes and catalyze the electron transfer reaction from plastocyanin to ferredoxin, as one of the main steps involved in conversion of light energy into chemical energy. PSI is highly efficiency with a photochemical efficiency close to one. Several attempts have doing in the past in order to exploit the high efficiency and high stability of PSI in an extra-cellular context in order to catalyze electron transfer reactions: in this work we present an innovative solution for exploiting the photochemical properties of PSI, by encapsulation of PSI complexes in organic nanoparticles. Nanoparticles offer a protected environment to the encapsulated molecule, giving it the possibility of preserving its functional properties and studying how they change over time. In this work the complete characterization, both morphological and functional, of nanostructures obtained by encapsulation of PSI complexes purified from higher plants with PLGA (poly lactic-co-glycolic acid) polymer is presented. The results obtained by transient absorption and time-resolved fluorescence demonstrate that encapsulated PSI were characterized by an higher photochemcial activity compared to PSI complexes in detergent solution. Moreover, encapsulated PSI maintained the high efficiency observed for several weeks even if exposed to very strong light, being more stable compared to PSI in detergent solution. Finally, the nanostructures obtained by encapsulated PSI were able to catalyze light dependent redox reactions with electron acceptors and donors outside the nanostructures Potential application of these PLGA encapsulated PSI in different fields are thus presented and discussed

Limit on the Radiative Neutrinoless Double Electron Capture of 36^{36}Ar from GERDA Phase I

Neutrinoless double electron capture is a process that, if detected, would give evidence of lepton number violation and the Majorana nature of neutrinos. A search for neutrinoless double electron capture of $^{36}$Ar has been performed with germanium detectors installed in liquid argon using data from Phase I of the GERmanium Detector Array (GERDA) experiment at the Gran Sasso Laboratory of INFN, Italy. No signal was observed and an experimental lower limit on the half-life of the radiative neutrinoless double electron capture of $^{36}$Ar was established: $T_{1/2} >$ 3.6 $\times$ 10$^{21}$ yr at 90 % C.I.Comment: 7 pages, 3 figure

Microchip Capillary Electrophoresis (Lab-on-chip\uae) Improves Detection of Celery (Apium graveolens L.) and Sesame (Sesamum indicum L.) in Foods

PCR is an usual analytical method applied to the detection of food allergens but sensitivity is a crucial problem in conventional post-PCR detection phase. The multiplex PCR approach often leads to adjunctive loss of sensitivity. The main goal of our study was to improve sensitivity in order to simultaneously detect sesame and celery in foods by mean of an end-point PCR protocol, by replacing conventional agarose gel electrophoresis with a Lab-on-chip® platform (microchip-based capillary electrophoresis). The Lab-on-chip®-based detection allowed to obtain the highest sensitivity in singleplex end-point PCR, for celery and sesame-specific primer pairs, using wheat flour as diluting agent. Moreover, in order to simulate a real system, home-made meat balls and commercial soup were artificially spiked with different percentages of sesame/celery (5% cooked meat balls, w/w and 0.1% soups, w/w), and then analyzed. Limits of detection highlighted in this study using Lab-on-chip® capillary electrophoresis were significantly lower if compared to those obtained with classical agarose gel electrophoresis

The Cryogenic AntiCoincidence Detector for ATHENA X-IFU: Improvement of the Test Setup Toward the Demonstration Model

The ATHENA X-IFU development program foresees to build and characterize an instrument Demonstration Model (DM), in order to probe the system critical technologies before the mission adoption. In this respect, we are now developing the DM of the X-IFU Cryogenic AntiCoincidence Detector (CryoAC), which will be delivered to the Focal Plane Assembly development team for the integration with the TES array. Before the delivery, we will characterize and test the CryoAC DM in our CryoLab at INAF/IAPS. In this paper, we report the main results of the activities performed to improve our cryogenic test setup, making it suitable for the DM integration. These activities mainly consist in the development of a mechanical setup and a cryogenic magnetic shielding system, whose effectiveness has been assessed by FEM simulations and a measurement at warm. The preliminary performance test has been performed by means of the last CryoAC single-pixel prototype, the AC-S8 pre-DM sample