2- -4-nitrophenyl phosphate

Deming and Pardue studied the kinetics for the hydrolysis of p-nitrophenyl phosphate by the enzyme alkaline phosphatase. The progress of the reaction was monitored by measuring the absorbance due to p-nitrophenol, which is one of the products of the reaction. A plot of the rate of the reaction (with units of pmol mL s ) versus the volume, V, (in milliliters) of a serum calibration standard containing the enzyme yielded a straight line with the following equation... 

The rat LD qS are 13, 3.6 (oral) and 21, 6.8 (dermal) mg/kg. Parathion is resistant to aqueous hydrolysis, but is hydroly2ed by alkah to form the noninsecticidal diethjlphosphorothioic acid and -nitrophenol. The time required for 50% hydrolysis is 120 d ia a saturated aqueous solution, or 8 h ia a solution of lime water. At temperatures above 130°C, parathion slowly isomerizes to 0,%diethyl 0-(4-nitrophenyl) phosphorothioate [597-88-6] which is much less stable and less effective as an insecticide. Parathion is readily reduced, eg, by bacillus subtilis ia polluted water and ia the mammalian mmen to nontoxic 0,0-diethyl 0-(4-aminophenyl) phosphorothioate, and is oxidized with difficulty to the highly toxic paraoxon [511-45-5] diethyl 4-nitrophenyl phosphate d 1.268, soluble ia water to 2.4 mg/L), rat oral LD q 1.2 mg/kg. 

Chemical modification studies with fluorescein-5 -isothiocyanate support the proximity of Lys515 to the ATP binding site [98,113-117,212,339]. Fluorescein-5 -isothiocyanate stoichiometrically reacts with the Ca -ATPase in intact or solubilized sarcoplasmic reticulum at a mildly alkaline pH, causing inhibition of ATPase activity, ATP-dependent Ca transport, and the phosphorylation of the Ca " -ATPase by ATP the Ca uptake energized by acetylphosphate, carbamylphos-phate or j -nitrophenyl phosphate is only partially inhibited [113,114,212,339]. The reaction of -ATPase with FITC is competitively inhibited by ATP, AMPPNP, TNP-ATP, and less effectively by ADP or ITP the concentrations of the various nucleotides required for protection are consistent with their affinities for the ATP binding site of the Ca -ATPase [114,212,340]. 

Diethyl p-nitrophenyl phosphate (E-600) is an odorless reddish-yellow oil which... 

Diethyl p-nitrophenyl phosphate, the oxygen analog of parathion, was investigated to ascertain whether it would interfere, if present, in the determination of parathion. It was found, however, under the conditions used in this method to have a decomposition potential of —0.37 volt and a half-wave potential of —0.47 volt. 

Figure 14-2. Potential energy curves (relative to separated monoanions) for the dissociation of / -nitrophenyl phosphate (pNPP) and / -nitrophenyl phosphorothioate (pNPTP) in the gas phase...

The phosphate diesters (02P(0R)2), ethyl-4-nitrophenyl phosphate and bis(4-nitrophenyl)phos-phate in c/.v-[(en)2Ir(OI I)(02P(0R)2]1, react intramolecularly with the as-OH group at pH 8 to liberate nitrophenolate.22... 

The hydrolysis of p-nitrophenyl acetate and bis(p-nitrophenyl phosphate) are frequently used to probe hydrolytic activity. A problem with some other dinuclear systems is that the Zn units are held together by bridging ligands which can be cleaved on reaction with the substrate.440 This is not the case in a ditopic ligand such as those designed by Lippard and co-workers based on Kemp s triacid imide with a xylyl spacer.441,442 Both zinc dimers and mixed metal dimers were formed and a structure characterized with a bridging phosphodiester (Figure 6). 

Fenton and co-workers observed the hydrolysis of bis- and tris-nitrophenyl phosphate with the zinc complex of the pentadentate N302 ligand V,V - (salicylideneimino)-ethyl -2-hydroxy-5-nitro-benzylamine.890... 

As is apparent from Fig. 1, the dianions of monoalkyl phosphates normally resist hydrolysis. However, for leaving groups whose conjugate acids exhibit a pKa < 5 in water, hydrolysis of the dianion becomes faster than that of the monoanion. Fig. 2 shows a pH profile characteristic of this situation. Whereas the hydrolysis rate of 2,4,6-trichlorophenyl phosphate (pKa of the phenol 6.1) still shows the typical monoanion preference as seen for methyl phosphates (Fig. 1), the dianion of 2,4-dinitrophenyl phosphate (pKa of the phenol 4.09) is hydrolyzed far faster than the monoanion 2-chloro-4-nitrophenyl phosphate represents an intermediate case (pKa of the phenol 5.45)6S). 

The highly electrophilic character of the POf ion would suggest a very unselective phosphorylation behavior. For example, the ratio of alkyl phosphate to inorganic phosphate obtained in hydrolyses of phosphoric esters in water/alcohol mixtures should reflect the molar ratio of water and alcohol. This is indeed found in numerous cases, e.g. in the hydrolysis of phenyl and 4-nitrophenyl phosphate monoanions 97) or of 4-nitrophenyl phosphate dianions 65) at 100 °C in methanol/ water mixtures of various compositions, as also in the solvolysis of the acetyl phosphate dianion at 37 °C 97) or of phosphoenol pyruvate monoanions 82). Calculations of the free energy of the addition reactions of water and ethanol to the POf ion support the energetic similarity of the two reactions 98) (Table 4). 

An early example of a combinatorial approach to a reaction catalyzed by transition metal coordination compounds concerns phosphatase mimics, specifically in the hydrolysis of bis(/ -nitrophenyl)phosphate (1)—>(2) (Equation (l)) 29... 

In related work a library of 1,458 peptide ligands and various metal salts was tested in hydrolysis reactions of (p-nitrophenyl)phosphates.35 An active substructure composed of polymer-bound histidine in combination with Eu3+ was identified by further dissecting the original hit structure. It needs to be pointed out that catalytically active polymer beads can also be tested for catalytic activity using IR-thermography. In a seminal paper this was demonstrated using 7,000 encoded polymer beads prepared by split-and-pool methods, specifically in the metal-free acylation of alcohols.36... 

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