Sensing cations

Rettig W, Rurack K, Sczepan M (2001) From cyanines to styryl bases - photophysical properties, photochemical mechanisms, and cation sensing abilities of charged and neutral polymethinic dyes. In Valeur B, Brochon JC (eds) New trends in fluorescence spectroscopy applications to chemical and life sciences. Springer, Berlin, pp 125-155... 

From Cyanines to Styryl Bases -Photophysical Properties, Photochemical Mechanisms, and Cation Sensing Abilities of Charged and Neutral Polymethinic Dyes, in Valeur B. and Brochon J. C. (Eds),... 

Abundant data indicate that Ca + inhibits the formation and activity of osteoclasts and stimulates the activity of osteoblasts. The first evidence for the existence of a G protein-coupled, cation-sensing mechanism in osteoblasts was presented shortly after the cloning of the CaR (Quarles et al, 1994). Since then some, but not all studies have found that the CaR is expressed in various osteoblastic cell lines and primary osteoblasts (Chang et al, 1999 Chattopadhyay et al, 2004 ... 

Quarles, LD, Hartle, JE, 2nd, Middleton, JP, Zhang, J, Arthur, JM and Raymond, JR, 1994, Aluminum-induced DNA synthesis in osteoblasts mediation by a G-protein coupled cation sensing mechanism, J Cell Biochem 56 106-117... 

Riccardi, D, Park, J, Lee, WS, Gamba, G, Brown, EM and Hebert, SC, 1995, Cloning and functional expression of a rat kidney extracellular calcium/polyvalent cation-sensing receptor, Proc Natl Acad Sci U S A 92 131-135... 

Sands, JM, Naruse, M, Baum, M, Jo, I, Hebert, SC, Brown, EM and Harris, HW, 1997, Apical extracellular calcium/polyvalent cation-sensing receptor regulates vasopressin-elicited water permeability in rat kidney irmer medullary collecting duct, J Clin Invest 99 1399—1405... 

Pazianas M, Adebanjo OA, Shankar VS, James SY, Colston KW, Maxwell JD, Zaidi M. 1995. Extracellular cation sensing by the enterocyte. Prediction of a novel divalent cation receptor. Biochem Biophys Res Comm210 948-53. 

Pi M, Faber P, Ekema G, Jackson PD, Ting A, Wang N, Fontilla-Poole M, Mays RW, Brunden KR, Harrington JJ, Quarles LD. 2005. Identification of a novel extracellular cation-sensing G-protein-coupled receptor. J Biol Chem 280 40201-9. 

Fig. 3 a Schematic representation for the monolayers of the cation-sensing library with short-wavelength fluorophores. b Relative fluorescence intensity of surfaces modified with different fluorophores and chemical functionalities in the presence of 10 3 M solutions of Pb2+, Zn2+ and Ca2+ as perchlorate salts. The data have been normalized in the absence of metal cations the fluorescence emission is set to 0 for the MD-1, MD-2 and MD-3 monolayers and for the MC-1, MC-2 and MC-3 monolayers at 510 and 460 nm, respectively... 

Scheme 11.4 Cation sensing by anthracene-substituted azacorand 11.27.19...

Physical and chemical stimuli such as temperature, solvent polarity and addition of various cations induce conformational changes in the nonconjugated polysquaraines, leading to either preferential folding to, or unfolding from, chromo-phore H-dimers. The binding event is translated into a shift in the monomer to H-dimer equilibrium of the squaraine chromophores and can be conveniently visualized by UV-Vis and fluorescence spectroscopy and, therefore, can successfully be exploited for cation sensing. 

The main advantage of PCT switches over PET switches consists in the possibility of usage of several wavelengths to analyze the state of the sensor, which is essential especially in intracellular cation sensing [10]. 

An interesting new approach of using TICT compounds in intermolecular interactions are molecules with a crown ether function. These molecules can form complexes with cations, e.g. Ca +, and the complex can have different emission properties in the complexed and the uncomplexed state. In this way, specific ion probes usable in medicine, biology and analytical chemistry can be developed. The mechanism of cation sensing and the TICT-crown molecules studied to date [145-147] are collected in Fig. 20. 

The results of an in vitro study on immortalized mouse distal convoluted tubule cells have suggested that aminoglycosides act through an extracellular polyvalent cation-sensing receptor and that they inhibit hormone-stimulated magnesium absorption in the distal convoluted tubule (80). 

After formation of the stable monolayers, their cation sensing properties were studied. The chloride salts of Hg2+, Ca2+, Co2+, and Cu2+ were used as analytes. Each of the layers of the sensing library was placed in a spectrofluorometer cuvette filled with 0.1M aqueous solution of HEPES buffer (pH 7.0) and the fluorescence spectrum was measured. A solution of the corresponding cation was added so that the concentration of the analyte in the cuvette was 10-4 M, and the fluorescence spectrum was measured again. Two typical examples of the layer fluorescence emission spectra in the presence of analytes are shown in Fig. 4.10. 

Quarles LD, Hartle JE, 11, Siddhanti SR, Guo R and Hinson TK (1997) A distinct cation-sensing mechanism in MC3T3-E1 osteoblasts functionally related to the calcium receptor. J Bone Miner Res 12 393-402. 

CH2CI2 solution by spectrophotometric titration. This is a rare example of the use of an otganometallic group as a chromophore in cation sensing. 

Work on thin polymer films of organometallic species has primarily been focused on anion sensing (presumably due to the positively charged nature of pyrrole electropolymers, the most commonly used type), although cation sensing by this method has also been demonstrated. 

Further fine-tuning of the physicochemical and chemical properties of the derivatives allows for their use for extraction of cations, sensing at surfaces and interfaces, conducting of polymers, and specific-site targeting in biological macromolecules. 

Fig. 2 Examples of ferrocene (Fc) derivatives used for cation sensing...

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