Selective Hydrolysis of Transferrin Promoted by Zr-Substituted Polyoxometalates.

ABSTRACT: The hydrolysis of the iron-binding blood plasma glycoprotein transferrin (Tf) has been examined at pH = 7.4 in the presence of a series of Zr-substituted polyoxometalates (Zr-POMs) including Keggin (Et2NH2)10[Zr(PW11O39)2]?7H2O (Zr-K 1:2), (Et2NH2)8[{?-PW11O39Zr-(?-OH) (H2O)}2]?7H2O (Zr-K 2:2), Wells-Dawson K15H[Zr(?2-P2W17O61)2]·25H2O (Zr-WD 1:2), Na14[Zr4(?-P2W16O59)2(?3-O)2(?-OH)2(H2O)4]·57H2O (Zr-WD 4:2) and Lindqvist (Me4N)2[ZrW5O18(H2O)3] (Zr-L 1:1), (nBu4N)6[(ZrW5O18(?-OH))2]?2H2O (Zr-L 2:2)) type POMs. Incubation of transferrin with Zr-POMs resulted in formation of 13 polypeptide fragments that were observed on sodium dodecyl sulfate poly(acrylamide) gel electrophoresis (SDS-PAGE), but the hydrolysis efficiency varied depending on the nature of Zr-POMs. Molecular interactions between Zr-POMs and transferrin were investigated by using a range of complementary techniques such as tryptophan fluorescence, circular dichroism (CD), 31P-NMR spectroscopy, in order to gain better understanding of different efficiency of investigated Zr-POMs. A tryptophan fluorescence quenching study revealed that the most reactive Zr-WD species show the strongest interaction toward transferrin. The CD results demonstrated that interaction of Zr-POMs and transferrin in buffer solution result in significant secondary structure changes. The speciation of Zr-POMs has been followed by 31P-NMR spectroscopy in the presence and absence of transferrin, providing insight into stability of the catalysts under reaction condition.

SUBMITTER: Van Rompuy LS 

PROVIDER: S-EPMC7435656 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature