4 2 pyridylazo resorcinol par

Manufactured by Merck Group

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4-(2-pyridylazo)resorcinol (PAR) is a colorimetric reagent used in analytical chemistry. It is a heterocyclic compound composed of a pyridine ring and a resorcinol moiety. PAR has the chemical formula C₁₁H₉N₃O₂ and is commonly used as a complexing agent for the detection and quantification of various metal ions in solution.

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Lab products found in correlation

Xylenol orange, by Merck Group (1 mentions) Iron nitrate nonahydrate, by Merck Group (1 mentions) Sodium nitrate, by Merck Group (1 mentions) Aluminum nitrate nonahydrate, by Merck Group (1 mentions) Nitric acid, by Merck Group (1 mentions) P chloromercuribenzoic acid pcmb, by Merck Group (1 mentions)

Spelling variants of this product

Resorcinol (135 citations) 4-(2-pyridylazo) resorcinol (7 citations) PAR-2 (3 citations)

4 protocols using 4 2 pyridylazo resorcinol par

Synthesis of Metal Nitrate Solutions

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The following chemicals were used in this study: Iron nitrate nonahydrate (Fe(NO₃)₃∙9H₂O, ≥ 99.0%), manganous nitrate hexahydrate (Mn(NO₃)₂∙6H₂O, ≥ 99.0%), copper nitrate 2.5-hydrate (Cu(NO₃)₂∙2.5H₂O, ≥ 99.0%), cobalt nitrate hexahydrate (Co(NO₃)₂∙6H₂O, ≥ 99.0%), nickel nitrate hexahydrate (Ni(NO₃)₂∙6H₂O, ≥ 99.0%), zinc nitrate hexahydrate (Zn(NO₃)₂∙6H₂O, ≥ 99.0%), aluminum nitrate nonahydrate (Al(NO₃)₃∙9H₂O, ≥ 99.0%), sodium nitrate produced by Sigma-Aldrich (ACS chemical, ≥ 99.0%, St. Louis, MO, USA) (CAS no. 7631-99-4), 4-(2-pyridylazo)resorcinol (PAR) (CAS no. 1141-59-9), xylenol orange (CAS no. 3618-43-7), nitric acid (chemically pure), and poly(ethylene oxide) with a molecular weight of 1500 produced by Sigma-Aldrich (CAS no. 25322-68-3).
Double distilled water was used to prepare the solutions. All chemicals were used as received, without additional purification. The initial solutions of extracted metals nitrates were obtained by dissolving precisely weighed quantities in double distilled water slightly acidized with nitric acid (pH = 2.5) in order to prevent the generation of hydroxide metal formations.

Zakhodyaeva Y.A., Zinov’eva I.V., Tokar E.S, & Voshkin A.A. (2019). Complex Extraction of Metals in an Aqueous Two-Phase System Based on Poly(Ethylene Oxide) 1500 and Sodium Nitrate. Molecules, 24(22), 4078.

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Zinc Release Quantification Assay

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Zinc release was measured using a modified PAR/PCMB assay (Camberg and Sandkvist 2005; Ilbert et al. 2007). Briefly, zinc was removed from ΔN1‐EpsE‐Hcp1 purified protein using a titration of p‐chloromercuribenzoic acid (PCMB; Sigma‐Aldrich, St. Lois, MO, USA) in the presence of the zinc‐complexing agent 4‐(2‐pyridylazo)resorcinol (PAR; Sigma, Aldrich). Zinc release was measured at 500 nm and was compared to a ZnCl₂ standard curve. Assays were performed in duplicate and SEM is shown.

Rule C.S., Patrick M., Camberg J.L., Maricic N., Hol W.G, & Sandkvist M. (2016). Zinc coordination is essential for the function and activity of the type II secretion ATPase EpsE. MicrobiologyOpen, 5(5), 870-882.

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Kinetic Analysis of NDM Variants

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Using an established assay,^{48 (link)} we determined the K_d values for the Zn2 site (the labile zinc ion in NDM-1^{35 (link)}) for each of the soluble Δ35 NDM variants. Briefly, the colorimetric chelator 4-(2-pyridylazo)resorcinol (PAR, 10 μM, Sigma-Aldrich) is incubated with ZnSO₄ (4 μM, diluted from a 0.1M ZnSO₄ standard solution, Sigma-Aldrich) in HEPES Buffer (50 mM) at pH 7.4, and then titrated with the ‘as purified’ NDM-1, NDM-4 and NDM-12 (0 – 40 μM). At each condition, concentrations of the ZnH_x(PAR)₂ complex and total protein were calculated from absorbance values at 492 and 280 nm, respectively, and K_d values were derived from fits as described elsewhere.^{48 (link)}

Stewart A.C., Bethel C.R., VanPelt J., Bergstrom A., Cheng Z., Miller C.G., Williams C., Poth R., Morris M., Lahey O., Nix J.C., Tierney D.L., Page R.C., Crowder M.W., Bonomo R.A, & Fast W. (2017). Clinical Variants of New Delhi Metallo-β-Lactamase Are Evolving to Overcome Zinc Scarcity. ACS infectious diseases, 3(12), 927-940.

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Measuring Free Zinc Levels

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50 µM recombinant protein was exposed to 500 µM spermine NONOate, 500 µM GSNO, 500 µM H₂O₂, or 500 µM ONOO⁻. GSNO and ONOO⁻ were synthesized as previously described (Hart, 1985 ; Mohr et al., 1994 (link)). Free zinc was measured by the addition 150 mM of the metal chelator 4-(2-pyridylazo)resorcinol (PAR) (Sigma-Aldrich). PAR-zinc chelates were measured spectrometrically at A_500nm, and zinc concentration was calculated by regression analysis using known ZnCl₂ standards.

Henard C.A., Tapscott T., Crawford M.A., Husain M., Doulias P.T., Porwollik S., Liu L., McClelland M., Ischiropoulos H, & Vázquez-Torres A. (2014). The 4-Cysteine Zinc-Finger Motif of the RNA Polymerase Regulator DksA serves as a Thiol Switch for Sensing Oxidative and Nitrosative Stress. Molecular microbiology, 91(4), 790-804.

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