caa a22 4500 477132537 CHVBK 20180405111707.0 cr unu---uuuuu 170330e19971201xx s 000 0 eng 10.1023/A:1018328517603 doi (NATIONALLICENCE)springer-10.1023/A:1018328517603 The pH dependent properties of metallotransferrins: a comparative study [Elektronische Daten] [Luigi Messori, Giovanni Dal Poggetto, Roberto Monnanni, Junzo Hirose] The dependence on pH of the absorption and circular dichroic spectra of iron(III), cobalt(III) and copper(II) transferrins has been (re)investigated. In the alkaline region, the CD profiles of iron(III) and cobalt(III) transferrin are essentially pH independent up to pH 11; only for very high pH values (pH > 11) is breakdown of the cobalt(III) and iron(III) transferrin derivatives observed, without evidence of conformational rearrangements. By contrast, the CD profiles of copper transferrin show drastic changes in shape around pH 10; these spectral changes, which are fitted to a pKa of ~10.4, are interpreted in terms of a substantial rearrangement of the local environment of the copper ions at high pH. Although the CD spectra of copper transferrin at alkaline pH strictly resemble those observed upon addition of modifier anions, the mechanism of site destabilization in the two cases is different; at variance with the case of modifier anions, our results suggest that the high pH form of copper transferrin still contains the synergistic anion. A13C NMR experiment has confirmed this view. In the acidic region, iron(III) and cobalt(III) transferrins are stable down to pH ~6. For lower pH values progressive metal detachment is observed without evidence of conformational changes; around pH 4.5 most bound metals are released. In the case of the less stable copper-transferrin, metal removal from the specific binding sites is already complete around pH 6.0; in concomitance with release from the primary sites, binding of copper ions to secondary sites is observed. Additional information has been gained from CD experiments in the far UV. The pH dependent properties of iron(III), cobalt(III) and copper(II) transferrin are discussed in the frame of the present knowledge of transferrin chemistry, particular emphasis being attributed to the comparison between tripositive and bipositive metal derivatives. Chapman and Hall, 1997 circular dichroism nationallicence pH dependence nationallicence transferrin nationallicence Messori Luigi Department of Chemistry, University of Florence, Florence, Italy aut Dal Poggetto Giovanni Department of Chemistry, University of Florence, Florence, Italy aut Monnanni Roberto Department of Chemistry, University of Florence, Florence, Italy aut Hirose Junzo Department of Food Science and Technology, Fukuyama University, Hiroshima, Japan aut Biometals Kluwer Academic Publishers 10/4(1997-12-01), 303-313 0966-0844 10:4<303 1997 10 10534 https://doi.org/10.1023/A:1018328517603 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1018328517603 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Messori Luigi Department of Chemistry, University of Florence, Florence, Italy aut NATIONALLICENCE 700 1- Dal Poggetto Giovanni Department of Chemistry, University of Florence, Florence, Italy aut NATIONALLICENCE 700 1- Monnanni Roberto Department of Chemistry, University of Florence, Florence, Italy aut NATIONALLICENCE 700 1- Hirose Junzo Department of Food Science and Technology, Fukuyama University, Hiroshima, Japan aut NATIONALLICENCE 773 0- Biometals Kluwer Academic Publishers 10/4(1997-12-01), 303-313 0966-0844 10:4<303 1997 10 10534 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer