Inorganic phosphate determination: Colorimetric assay based on the formation of a rhodamine B-phosphomolybdate complex

Na+,K+-ATPase as the Target Enzyme for Organic and Inorganic Compounds

“…Measurement of the specific Na + ,K + -ATPase activity (nanomol of inorganic phosphate, Pi, liberated per min per milligram of protein as well as protein content) is required to evaluate the purity or to determine the actual specific enzyme activity [56-58]. Enzymatic ATP hydrolysis has been measured by several different means, as well as the determination of adenosine diphosphate (ADP) by enzyme coupling [59], or by colorimetric reactions [60, 61] and spectroscopic techniques [62], including measurement of 32 P release from [γ- 32 P]ATP hydrolysis [63, 64]. In general, non-radioactive assays are much less sensitive than the radioactive ones.…”

A Robotics-Based Automated Assay for Inorganic and Organic Phosphates

“…Other cationic dyes, notably rhodamine B (which has a molar absorption coefficient several times higher than that of malachite green), does not undergo a significant color change when a complex is formed with phosphomolybdate (40). Thus, when using this dye, it is necessary to separate unbound dye from that bound to the complex before optical measurements can be made (40). The separation and washing steps would complicate the automation, so we did not consider rhodamine B further.…”

Functional microdomains in bacterial membranes

“…An enzymatic assay to monitor the enzymatic activity of YisP was performed according to Debruyne (1983) with specific modifications. We monitored release of inorganic phosphate derived from the condensation of two molecules of FPP using the ability of rhodamine B to precipitate, once it is chelated with the inorganic phosphate released from the reaction of condensation (2FPP / Squalene + 2PPi).…”