Sensing phosphate

Sun H, Scharff-Poulsen AM, Gu H, Jakobsen I, Kossmann JM, Frommer WB, Almdal K (2008) Phosphate sensing by fluorescent reporter proteins embedded in polyacrylamide nanoparticles. ACS Nano 2 19-24... 

Abel S, Ticconi CA, Delatorre CA. 2002. Phosphate sensing in higher plants. Physiol Plant arum 115 1-8. 

Fig. 18). This effect is not observed with CP or HSO " ions. Therefore, we reported the first case of specific dihydrogen phosphate sensing by emission. 

Scheme 5.5 Phosphate sensing based on coupled purine nucleoside phosphorylase/XO activity.

Ca2+-sensing Receptor Calpains Protein Phosphates S100 Proteins... 

In an ideal pure preparation of Na,K-ATPase from outer renal medulla, the al subunit forms 65 70% of the total protein and the molar ratio of a to is 1 1, corresponding to a mass ratio of about 3 1 [1,5]. Functionally the preparation should be fully active in the sense that each a/ unit binds ATP, Pj, cations and the inhibitors vanadate and ouabain. The molecular activity should be close to a maximum value of 7 000-8 000 Pj/min. The highest reported binding capacities for ATP and phosphate are in the range 5-6 nmol/mg protein and close to one ligand per otjS unit [29], when fractions with maximum specific activities of Na,K-ATPase [40 50 pmo Pj/min mg protein) are selected for assay. 

AP isoenzymes can cleave associated phosphomonoester groups from a wide variety of substrates. The exact biological function of these enzymes is not well understood. They can behave in vivo in their classic phosphohydrolase role at alkaline pH, but at neutral pH AP isoenzymes can act as phosphotransferases. In this sense, suitable phosphate acceptor molecules can be utilized in solution to increase the reaction rates of AP on selected substrates. Typical phosphate acceptor additives include diethanolamine, Tris, and 2-amino-2-methyl-lpropanol. The presence of these additives in substrate buffers can dramatically increase the sensitivity of AP ELISA determinations, even when the substrate reaction is done in alkaline conditions. 

Similarly to dyes, some fluorescent proteins can be incorporated into polymeric beads to be used as an alternative for ion sensing. For example, a reporter protein (composed of a phosphate-binding protein, a FRET donor (cyan fluorescent protein) and a FRET acceptor (yellow fluorescent protein)) was incorporated into polyacrylamide nanobeads by Sun et al. [46]. FRET was inhibited upon binding of phosphate. Kopelman and co-workers [47] used a similar approach to design a nanosensor for copper ions. They have found that fluorescence of red fluorescent protein DsRed (commonly used as a label) is reversibly quenched by Cu2+ and Cu+. Both DsRed and Alexa Fluor 488 (used as a reference) were entrapped into polyacrylamide nanobeads. Typically, up to 2 ppb of copper ions can be reliably measured. It should be mentioned, that in contrast to much more robust dyes, mild conditions upon polymerization and purification are very important for immobilization of the biomolecule to avoid degradation. 

Jokichi Takamine (1854-1922) went to the University of Glasgow, and then, to the United States to investigate the phosphatic manure, and he established the first company of phosphatic manure in Japan. He produced Takadiastase, a digestive agent containing various digestive enzymes, ribonuclease and cellulase. Amylase was extracted from Takadiastase. In a narrow sense, Takadiastase is one of the carboxyoroteases. He discovered in 1900. 

Eor the former solvent log D = -1.92 (experimental) vs. -1.98 (calculated) and for the latter log D = 0.76 (experimental) vs. 0.88 (calculated). Obviously, succinic acid with two carboxylic groups that strongly donate hydrogen bonds (assigned a = 1.12 as for acetic acid) prefers the basic (in the Lewis basicity, hydrogen-bond-accepting sense) tri-n-butyl phosphate ( i = 0.82, measured for the wet solvent) over water (P = 0.47) and naturally also chloroform (P = 0.10). 

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