PH-Sensing Receptors

Proton-sensing GPCRs. Table 1 pH-sensing receptors... 

The principle of photoinduced electron transfer is combined with the modular system Fluorophore-Spacer-Receptor to develop the phenomenon of cation-responsive fluorescence. pH controlled on-off fluorescence is demonstrated in the case of the dialkylaminoalkyl heterocyclic derivative la. The modular system is then extended in two directions. In the first of these, targetting/anchoring modules are added to allow the investigation of proton fields in microheterogeneous membrane media with high spatial resolution. The sensor family 2a-f is the realization of this approach. The second direction employs phosphorescent (instead of fluorescent) modules with/without protective shields to permit the development of phosphorescent pH sensing in an interference-free manner within... 

Gastric secretion is under the control of hormonal, neuronal, and calcium-sensing receptors, resulting in causing the parietal cells to secrete concentrated acid with pH close to 1. A variety of in vitro and in vivo techniques have been used to study gastric secretion, with emphasis on acid secretion, in isolated parietal cells, isolated whole stomach preparation, or the use of recent technology of noninvasive in vivo telemetry methods. 

Anion sensing by complexes involving macrocyclic and calix[4]arene domains has been reviewed. The receptors [Ru(bpy)2(252)] + (in (252), R = Ph, 2-HOCeH4, 3-HOCeH4, 4-HOCeH4, Bu, or 4- BuC6H4) bind Cl, Br, and I hydrogen-bonded interactions that contribute to this process are discussed. All the complexes show the same anion selectivity CC > Br > The crystal... 

One of the most important design changes in the evolution of this type of sensor was to produce complexes stable in aqueous media. The cyclen-based ligands and their stable Eu(III) and Tb(III) complexes, 44-46, represent examples of sensors developed by Parker et al. for pH, p02, halide and hydroxide ion sensing, [148-150]. The ligand used was based on cyclen substituted in one of the four positions with phenanthridine as the antenna and receptor. The other three positions were substituted with various pendant... 

Another related example is 52 [157], which is a tetra-substituted cyclen ligand with four quinoline receptor moieties capable of sensing protons in a similar manner to 50. The lanthanide emission was found to be switched on in highly acidic conditions, with a luminescent enhancement of over 300-fold. Luminescent enhancement was attributed to an enhancement in the population of the Si and subsequent Ti excited states of the quinoline chromophore when in acidic media. A bell-shaped pH profile was found to exist at pH 1.8-3.5, whereas at more acidic pH the emission was switched off. 

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