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submitted on 20.05.2020 and posted on 21.05.2020by Denilson Mendes de Oliveira, Samual
R. Zukowski, Vladimir Palivec, Jérôme Hénin, Hector Martinez-Seara, Dor Ben-Amotz, Pavel Jungwirth, Elise Duboué-Dijon
In spite of the biological importance of the binding of Zn2+, Ca2+, and Mg2+ to carboxylate anions,
previous experimental and computational studies have reached conflicting conclusions regarding
the corresponding binding affinities. Here, we report the first use of Raman multivariate curve
resolution (Raman-MCR) vibrational spectroscopy to obtain self-consistent free and bound metal
acetate spectra and one-to-one binding constants, without the need to invoke any a priori
assumptions regarding the shapes of the corresponding vibrational bands. The experimental
results, combined with classical molecular dynamics simulations with a force field effectively
accounting for electronic polarization via charge scaling and ab initio simulations,
the measured binding constants pertain to direct (as opposed to water
separated) ion pairing. The resulting binding constants do not scale
with cation size, as the binding constant to Zn2+ is
significantly larger than that to either Mg2+ or Ca2+, although Zn2+ and Mg2+ have similar radii that
are about 25% smaller than Ca2+. Remaining uncertainties in the metal acetate binding free
energies are linked to fundamental ambiguities associated with identifying the range of structures
pertaining non-covalently bound species.
DBA, DMdO, and SKZ were supported in part by the US National Science Foundation (CHE- 1763581). PJ thanks the Czech Science Foundation for support via an EXPRO grant no. 19- 26854X. EDD acknowledges support from the EMBO and Marie Curie Actions (fellowship ALTF 952-2015), and EDD and JH were supported in part by the "Initiative d’Excellence" program from the French State (Grants "DYNAMO", ANR-11-LABX-0011, and "CACSICE", ANR-11-EQPX- 0008). HMS and VP acknowledge support from the Czech Science Foundation (19-19561S). This work was performed with computer time allocated by the national supercomputing center IT4innovations in Ostrava (project OPEN-8-35), the European Regional Development Fund OP RDE (project ChemBioDrug no. CZ.02.1.01/0.0/0.0/16_019/0000729) computational resources, and the MetaCentrum data storage facilities.