Journal article
Iron uptake by ferritin: NMR relaxometry studies at low iron loads
Journal of inorganic biochemistry, Vol.71(3), pp.153-157
1998
DOI: 10.1016/S0162-0134(98)10047-8
PMID: 9833320
Abstract
Twenty ferritin samples were prepared at pH 6.5 with average loadings of 0–89 Fe atoms per molecule. Nuclear magnetic relaxation times
T
1 and
T
2 were measured at 3°C, 23°C, and 37°C and at field strength from 0.025 to 1.5 T. The field dependence, temperature dependence, and approximate equality of
T
1 and
T
2 at low fields all suggest that nuclear magnetic relaxation in this range is caused primarily by solitary Fe
3+ ions. The relaxivity (relaxation rate per mM ferritin) increases quickly with initial iron loading, reaches a peak at 13–14 Fe atoms per molecule, and then declines. This provides supportive evidence for the formation of antiferromagnetically-coupled clusters during early stages in iron loading; the failure to see a similar peak in an earlier study may be related to the nonphysiological pH that was used. Above 50 atoms per molecule, the relaxivity remains approximately constant, except that 1/
T
2 at high fields increases slightly, consistent with early core growth. The residual ionic relaxivity in this region is consistent with about three solitary Fe
3+ ions remaining on the protein shell, indicating that spin cancellation is not complete. A similar value is obtained by extrapolating relaxation data at high loadings (up to 3000 Fe atoms per molecule), suggesting that these uncoupled spins persist on the protein shell even after an appreciable core has been built.
Details
- Title: Subtitle
- Iron uptake by ferritin: NMR relaxometry studies at low iron loads
- Creators
- J Vymazal - Neuroimaging Branch, NINDS, National Institutes of Health, Bethesda, MD 20892, USAR.A Brooks - National Institutes of HealthJ.W.M Bulte - Laboratory of Diagnostic Radiology Research, CC, National Institutes of Health, Bethesda, MD 20892, USAD Gordon - Neuroimaging Branch, NINDS, National Institutes of Health, Bethesda, MD 20892, USAP Aisen - Department of Biophysics, Albert Einstein Medical College, Bronx, NY 10461, USA
- Resource Type
- Journal article
- Publication Details
- Journal of inorganic biochemistry, Vol.71(3), pp.153-157
- Publisher
- Elsevier Inc
- DOI
- 10.1016/S0162-0134(98)10047-8
- PMID
- 9833320
- ISSN
- 0162-0134
- eISSN
- 1873-3344
- Language
- English
- Date published
- 1998
- Academic Unit
- Stead Family Department of Pediatrics; Hematology/Oncology
- Record Identifier
- 9984093323902771
Metrics
22 Record Views