The aforementioned probes do not directly sense ROS (e.g., H2O2 or ONOO?), and fluorescent changes are only observed when the generated ROS are able to shift the GSH/GSSG equilibrium. Variants of roGFP have also been developed to show different redox potentials, which are particularly valuable for imaging redox dynamics in cell compartments with different basal redox levels [33]. roGFP is excitation-ratiometric, so it is less sensitive to the expression levels of the probe and fluorescence photobleaching, leading to better control for quantitative measurement. Indeed, roGFP is used more often than rxYFP. It is worth noting that, for both roGFP and rxYFP, the oxidation and reduction modulate the equilibrium of their chromophore between a neutral and an anionic state.

Therefore, these probes are intrinsically sensitive to pH changes and additional caution is needed when interpreting fluorescence results.Figure 2.X-ray structures of roGFP variants in their oxidized (a) and reduced (b) forms (redrawn from PDB 2AH8 and 2AHA).3.?Molecular Hybrids of Fluorescent Proteins and Redox Sensory ProteinsIn order to directly sense H2O2, roGFP has been linked to a H2O2-specific peroxidase Orp1 [34]. H2O2 can generate an intramolecular disulfide bond in Orp1, which is next quickly transferred to roGFP through a thiol-disulfide exchange mechanism. Oxidation of Orp1 by H2O2 can be near-stoichiometrically converted to oxidation of roGFP. The oxidized roGFP-Orp1 probe is reversible in cells by reducing molecules such as thioredoxin (Trx) and potentially the Grx/GSH system.

So the roGFP-Orp1 fusion responds to a balance between H2O2-induced oxidation and cell reduction.Another approach to sense H2O2 is to directly conjugate circula
Global Positioning Systems (GPS) are nowadays used in many agricultural tasks [1�C3]. GPS receivers with RTK differential corrections are frequently employed in agricultural equipment [4,5]. Nevertheless, tasks such as yield mapping [6] and assisted guidance in cereal fertilization do not always need centimeter precision. In consequence, some companies manufacture assisted guidance systems for tractors equipped with low-cost GPS receivers, such as Agroguia? [7] and Tractordrive? [8], for example, in Spain. Moreover, the universalization of mobile computing with smartphones and tablet devices, equipped with powerful processors and low-cost embedded GPS receivers, makes the use of these devices in agricultural tasks attractive.

However, due to a quantization effect, most low-cost GPS receivers provide positions on a rectangular Cilengitide grid of some decimeters on each side. Because of this fact, low speed trajectories and parts of the trajectories with headings close to a coordinate axle suffer from significant speed, position, and heading errors when using low-cost GPS receivers.