P-aminophenyl phosphate

T.T. Hua, C.E. Lunte, H.B. Halsall and W.H. Heineman, p-Aminophenyl phosphate An improved substrate for electrochemical enzyme immunoassay, Anal. Chim. Acta, 214 (1988) 187-195. 

Substrate p-aminophenyl phosphate and reduction of Ag+ to Ag. Oxidation peak of Ag 100 aM [14]... 

The specific electrochemical behaviour of IDAs is result of its design [97], i.e. two arrays intercalated and individually addressed in a bipotentiostatic system where reversible redox species can be cycled between one array (generator) and the other array (collector) (Fig. 32.3). The feedback obtained, greatly enhances the current and high sensitive detection can be achieved. An important application of IDAs is the electrochemical detection of p-aminophenol when it is generated from p-aminophenyl phosphate, by enzymatic reaction with alkaline phosphatase (like enzymatic label), in geno- [98-100] and immunoassays [101-103]. Another interesting feature of IDAs is the possibility of... 

Streptavidin coupled with phosphatase alkaline (Biospa, Milano, Italy) p-aminophenyl phosphate (PAPP, Universal Sensors, Kinsale-Sandycove, Ireland) 2-(methylamino)ethanol (Aldrich, Milwaukee, USA) bovine serum albumin (BSA), phosphate and tris buffer (Sigma, St Louis, USA). 

Substrate incubation place 15 pL of enzyme substrate solution (10 mM p-aminophenyl phosphate (PAPP) in 100 mM 2-MAE + 2 mM MgCl2 buffer at pH 9) in the Immuchip reservoirs. 

Figure 14. Cyclic voltammogram of enzyme-linked electrodes in a solution of 0.5 mM p-aminophenyl phosphate ( p-APP) scan rate of 50 mV/s in the case of hybridization with (a) 1 pM complementary target (Tl), (b) 1 uM single base- mismatched target (T3), (c) 1 pM non-complementary target (T2),and (d) without hybridization with target and detection probe (Adapted from Ref.[ 160]).

Tang, H.T., Lunte, C.E., Halsall, H.B., and Heineman, W.R. (1988) p-Aminophenyl phosphate an improved substrate for electrochemical enzyme immunoassay. Analytica Chimica Acta, 214,187-195. 

The amplification of the amperometric response of redox species has been studied for p-aminophenol The sensitive detection of this compound is of particular interest since it is the basis for the measurement of enzymes such as alkaline phosphatase and (J-galactosidase, which are frequently used in enzyme immunoassays The electrode active species (p-aminophenol) is liberated in the enzyme catalysed hydrolysis of its aminophenylated substrate which itself exhibit an irreversible electrochemical behavior The utility of p-aminophenyl phosphate in enzyme immunoassays in combination with IDA electrodes has been demonstrated in [6] The unfavorable pH-optimum of alkaline phosphatase is the drawback of this system Because of its neutral pH-optimum p-galactosidase appeared to be more advantageous An illustration of the proposed electrochemical enzyme immunoassay is given in Fig 2... 

The enzyme labels are typically horse radish peroxidase (HRP, electrochemical detection shown in the scheme) and alkaline phosphatase (ALP). Lor ALP, the selection of substrates is limited and p-aminophenyl phosphate (PAPP) is mostly used as the resulting aminophenol becomes easily and reversibly oxidised at the electrode. A wide choice of substrates (DH2) generating electroactive products includes hydroquinone, tetramethylbenzidine, aminosalicylic acid and iodide in the case of HRP ... 

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