Gaseous Electronics

Contains reports on two research projects.Joint Services Electronics Program (Contract DA36-039-AMC-03200(E)

Gaseous Electronics

Contains research objectives and reports on two research projects.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 36-039-AMC-03200(E

Computational shelf-life dating : complex systems approaches to food quality and safety

Shelf-life is defined as the time that a product is acceptable and meets the consumers expectations regarding food quality. It is the result of the conjunction of all services in production, distribution, and consumption. Shelf-life dating is one of the most difficult tasks in food engineering. Market pressure has lead to the implementation of shelf-life by sensory analyses, which may not reflect the full quality spectra. Moreover, traditional methods for shelf-life dating and small-scale distribution chain tests cannot reproduce in a laboratory the real conditions of storage, distribution, and consumption on food quality. Today, food engineers are facing the challenges to monitor, diagnose, and control the quality and safety of food products. The advent of nanotechnology, multivariate sensors, information systems, and complex systems will revolutionize the way we manage, distribute, and consume foods. The informed consumer demands foods, under the legal standards, at low cost, high standards of nutritional, sensory, and health benefits. To accommodate the new paradigms, we herein present a critical review of shelf-life dating approaches with special emphasis in computational systems and future trends on complex systems methodologies applied to the prediction of food quality and safety.Fundo Europeu de Desenvolvimento Regional (FEDER) - Programa POS-ConhecimentoFundação para a Ciência e a Tecnologia (FCT) - SFRH/BPD/26133/2005, SFRH/ BPD/20735/200

Direct Monitoring of the Reaction between Photochemically Generated Nitric Oxide and <i>Mycobacterium tuberculosis</i> Truncated Hemoglobin N Wild Type and Variant Forms: An Assessment of Computational Mechanistic Predictions

The previously reported nitric oxide precursor [Mn­(PaPy₂Q)­NO]­ClO₄ (<b>1</b>), where (PaPy₂QH) is <i>N</i>,<i>N</i>-bis­(2-pyridylmethyl)-amine-<i>N</i>-ethyl-2-quinoline-2-carboxamide, was used to investigate the interaction between NO and the protein truncated hemoglobin N (trHbN) from the pathogen <i>Mycobacterium tuberculosis</i>. Oxy-trHbN is exceptionally efficient at converting NO to nitrate, with a reported rate constant of 7.45 × 10⁸ M^–1 s^–1 [Ouellet, H., et al. (2002) <i>Proc. Natl. Acad. Sci. U.S.A. 99</i>, 5902] compared to 4 × 10⁷ M^–1 s^–1 for oxy-myoglobin [Eich, R. F., et al. (1996) <i>Biochemistry 35</i>, 6976]. This work analyzed the NO dioxygenation kinetics of wild type oxy-trHbN and a set of variants, as well as the nitrosylation kinetics for the reduced (red-trHbN) forms of these proteins. The NO dioxygenation reaction was remarkably insensitive to mutations, even within the active site, while nitrosylation was somewhat more sensitive. Curiously, the most profound change to the rate constant for nitrosylation was effected by deletion of a 12-amino acid dangling N-terminal sequence. The deletion mutant exhibited first-order kinetics with respect to NO but was zero-order with respect to protein concentration; by contrast, all other variants exhibited second-order rate constants of >10⁸ M^–1 s^–1. trHbN boasts an extensive tunnel system that connects the protein exterior with the active site, which is likely the main contributor to the protein’s impressive NO dioxygenation efficiency. The results herein suggest that N-terminal deletion abolishes a large scale conformational motion, in the absence of which NO can still readily enter the tunnel system but is then prevented from binding to the heme for an extended period of time