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Giardi M.T.,CNR Institute of Neuroscience | Rea G.,CNR Institute of Neuroscience | Lambreva M.D.,CNR Institute of Neuroscience | Antonacci A.,CNR Institute of Neuroscience | And 4 more authors.
PLoS ONE | Year: 2013

Space missions have enabled testing how microorganisms, animals and plants respond to extra-terrestrial, complex and hazardous environment in space. Photosynthetic organisms are thought to be relatively more prone to microgravity, weak magnetic field and cosmic radiation because oxygenic photosynthesis is intimately associated with capture and conversion of light energy into chemical energy, a process that has adapted to relatively less complex and contained environment on Earth. To study the direct effect of the space environment on the fundamental process of photosynthesis, we sent into low Earth orbit space engineered and mutated strains of the unicellular green alga, Chlamydomonas reinhardtii, which has been widely used as a model of photosynthetic organisms. The algal mutants contained specific amino acid substitutions in the functionally important regions of the pivotal Photosystem II (PSII) reaction centre D1 protein near the QB binding pocket and in the environment surrounding Tyr-161 (YZ) electron acceptor of the oxygen-evolving complex. Using real-time measurements of PSII photochemistry, here we show that during the space flight while the control strain and two D1 mutants (A250L and V160A) were inefficient in carrying out PSII activity, two other D1 mutants, I163N and A251C, performed efficient photosynthesis, and actively re-grew upon return to Earth. Mimicking the neutron irradiation component of cosmic rays on Earth yielded similar results. Experiments with I163N and A251C D1 mutants performed on ground showed that they are better able to modulate PSII excitation pressure and have higher capacity to reoxidize the QA - state of the primary electron acceptor. These results highlight the contribution of D1 conformation in relation to photosynthesis and oxygen production in space. Source


Wiederoder M.S.,University of Maryland College Park | Wiederoder M.S.,U.S. Department of Agriculture | Lefcourt A.M.,U.S. Department of Agriculture | Lefcourt A.M.,The Henry llace Beltsville Agricultural Research Center | And 2 more authors.
Sensing and Instrumentation for Food Quality and Safety | Year: 2012

To reduce the risk of foodborne-illness, produce processors currently clean and sanitize food contact surfaces daily before production starts. Current methods to verify the efficacy of cleaning procedures include visual inspection and direct surface sampling using ATP bioluminescence assays and culturing methods. To assess the possibility of augmenting these existing verification methods, this study investigated the potential to use imaging techniques to detect fresh-cut produce residues. A laboratory hyperspectral system was used to image produce residues obtained from a commercial processing plant, cantaloupe and honeydew residues generated in-house, and selected cleaning and sanitizing agents. Test materials were dispensed onto stainless steel and high density polyethylene coupons. The coupons were selected to represent common surfaces used in production facilities. Analysis of VIS/NIR hyperspectral reflectance and fluorescence images showed that the cleaning and sanitizing agents were essentially undetectable; thus, demonstrating that presence of these substances would not result in false-positives. In contrast, produce residues in microgram quantities showed fluorescence peaks encompassing the regions from 480 to 560 nm and from 670 to 690 nm. However, auto-fluorescence responses of high density polyethylene at shorter wavelengths were found to obscure the 480 to 560 nm peaks for some residues. These results suggest that fluorescence imaging techniques can be used to enhance surface hygiene inspection in produce processing plants and, given the immediate availability of imaging results, to help optimize routine cleaning procedures. © 2012 Springer Science + Business Media New York (Outside the USA). Source

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