Speciation of aqueous solutions of iron(III)-nitrilotriacetic acid complexes - simulations

Abstract

Experimental data for a paper entitled Method for preparation and characterization of iron(III) nitrilotriacetic acid solution for quantitative protein binding experiments (paper in preparation; citation will be updated pending publication). A custom VBA script for Microsoft Excel 365 (Version 2304, build 16.0.16327.20200, 64-bit) was used to solve the 5th-order polynomial for the free ligand NTA3− as a function of all congruent association and dissociation constants and the total concentrations of iron, ligand, and hydrogen ions using the Jenkins-Traub algorithm. [1-4] For comparison, the FeNTA species distribution was also simulated using HySS software [5], which applies the Newton-Raphson algorithm to solve the mass balance equations using known equilibrium constants. [6-7] The Excel workbook is provided with the following information: Sheet 1: FeNTA-Speciation - contains all relevant equilibrium constants and corresponding equations, expressions for polynomial coefficients, polynomial roots, and equilibrium concentrations of all species. The values are calculated from the analytical concentrations provided to the HySS software and imported to Sheet 2. Sheet 2: HySS-Import - contains the values obtained from the HySS software (the HySS model file is also included for reference). The values in the columns headed 'total Fe', 'total NTA' and 'p(H)' are used for the calculation in Sheet 1. Sheet 3: Examples - contains plots for the FeNTA species distribution obtained by solving the 5th-order polynomial in Excel and HySS software: Top: Fe:NTA = 0.15 M:0.15 M, Bottom: Fe:NTA = 0.15 M:0.30 M. Sheet 4: Polynomial-Procedure - contains the details of using the VBA script in Excel. [1] For more details, please visit: https://glymech.pharma.hr//GlyMech.html. References: [1] Jenkins D (2014) Solving Quadratic, Cubic, Quartic and higher order equations; examples. In: Newton Excel Bach, not (just) an Excel Blog. https://newtonexcelbach.wordpress.com/2014/01/14/solving-quadratic-cubic-quartic-and-higher-order-equations-examples/. Accessed 18 May 2017 [2] Jenkins MA, Traub JF (1972) Algorithm 419: zeros of a complex polynomial [C2]. Commun ACM 15:97–99. https://doi.org/10.1145/361254.361262 [3] Jenkins MA (1975) Algorithm 493: Zeros of a Real Polynomial [C2]. ACM Trans Math Softw 1:178–189. https://doi.org/10.1145/355637.355643 [4] Ralston A, Rabinowitz P (1978) A first course in numerical analysis, 2d ed. McGraw-Hill, New York ISBN: 9780486414546 https://www.worldcat.org/title/44883559 [5] Alderighi L, Gans P, Ienco A, Peters D, Sabatini A, Vacca A (1999) Hyperquad simulation and speciation (HySS): a utility program for the investigation of equilibria involving soluble and partially soluble species. Coordination Chemistry Reviews 184:311–318. https://doi.org/10.1016/S0010-8545(98)00260-4 [6] Motekaitis RJ, Martell AE (1994) The Iron(III) and Iron(II) Complexes of Nitrilotriacetic Acid. Journal of Coordination Chemistry 31:67–78. https://doi.org/10.1080/00958979408022546 [7] Hegenauer J, Saltman P, Nace G (1979) Iron(III)-phosphoprotein chelates: stoichiometric equilibrium constant for interaction of iron(III) and phosphorylserine residues of phosvitin and casein. Biochemistry 18:3865–3879. https://doi.org/10.1021/bi00585a006This work was supported by funding from the Croatian Science Foundation grant UIP-2017-05-9537 – Glycosylation as a factor in the iron transport mechanism of human serum transferrin (GlyMech). Additional support was provided by the European Regional Development Fund grants for 'Strengthening of Scientific Research and Innovation Capacities of the Faculty of Pharmacy and Biochemistry at the University of Zagreb' (KK.01.1.1.02.0021), 'Development of methods for production and labelling of glycan standards for molecular diagnostics' (KK.01.1.1.07.0055) and 'Scientific center of excellence for personalized health care' (KK.01.1.1.01.0010)