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Spectroscopic Study of the Interaction between Horse Heart Myoglobin and Zirconium(IV)‐Substituted Polyoxometalates as Artificial Proteases
Author(s) -
Ly Hong Giang T.,
ParacVogt Tatja.
Publication year - 2017
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201700680
Subject(s) - fluorescence spectroscopy , chemistry , myoglobin , circular dichroism , spectroscopy , crystallography , nuclear magnetic resonance spectroscopy , quenching (fluorescence) , zirconium , fluorescence , inorganic chemistry , stereochemistry , organic chemistry , physics , quantum mechanics
A recent study [ Angew. Chem. Int. Ed . 2015 , 54 , 7391–7394] has shown that horse heart myoglobin (HHM) is selectively hydrolyzed by a range of zirconium(IV)‐substituted polyoxometalates (POMs) under mild conditions. In this study, the molecular interactions between the Zr‐POM catalysts and HHM are investigated by using a range of complementary techniques, including circular dichroism (CD), UV/Vis spectroscopy, tryptophan fluorescence spectroscopy, and 1 H and 31 P NMR spectroscopy. A tryptophan fluorescence quenching study reveals that, among all examined Zr‐POMs, the most reactive POM, 2:2 Zr IV ‐Keggin, exhibits the strongest interaction with HHM. 31 P NMR spectroscopy studies show that this POM dissociates in solution, resulting in the formation of a monomeric 1:1 Zr IV ‐Keggin structure, which is likely to be a catalytically active species. In the presence of Zr IV ‐POMs, HHM does not undergo complete denaturation, as evidenced by CD, UV/Vis, tryptophan fluorescence, and 1 H NMR spectroscopy. CD spectroscopy shows a gradual decrease in the α‐helical content of HHM upon addition of Zr IV ‐POMs. The largest effect is observed in the presence of a large Zr IV ‐Wells–Dawson structure, whereas small Zr IV ‐Lindqvist POM has the least influence on the decrease in the α‐helical content of HHM. In all cases, the Soret band at λ =409 nm is maintained in the presence of all examined Zr‐POMs, which indicates that no conformational changes in the protein occur near the heme group.