Determination of iron content and dispersity of intact ferritin by superconducting tunnel junction cryodetection mass spectrometry.
Anal Chem
; 87(17): 8985-93, 2015 Sep 01.
Article
em En
| MEDLINE
| ID: mdl-26266697
ABSTRACT
Ferritin is a common iron storage protein complex found in both eukaryotic and prokaryotic organisms. Although horse spleen holoferritin (HS-HoloFt) has been widely studied, this is the first report of mass spectrometry (MS) analysis of the intact form, likely because of its high molecular weight â¼850 kDa and broad iron-core mass distribution. The 24-subunit ferritin heteropolymer protein shell consists of light (L) and heavy (H) subunits and a ferrihydrite-like iron core. The H/L heterogeneity ratio of the horse spleen apoferritin (HS-ApoFt) shell was found to be â¼110 by liquid chromatography-electrospray ionization mass spectrometry. Superconducting tunneling junction (STJ) cryodetection matrix-assisted laser desorption ionization time-of-flight MS was utilized to determine the masses of intact HS-ApoFt, HS-HoloFt, and the HS-HoloFt dimer to be â¼505 kDa, â¼835 kDa, and â¼1.63 MDa, respectively. The structural integrity of HS-HoloFt and the proposed mineral adducts found for both purified L and H subunits suggest a robust biomacromolecular complex that is internally stabilized by the iron-based core. However, cross-linking experiments of HS-HoloFt with glutaraldehyde, unexpectedly, showed the complete release of the iron-based core in a one-step process revealing a cross-linked HS-ApoFt with a narrow fwhm peak width of 31.4 kTh compared to 295 kTh for HS-HoloFt. The MS analysis of HS-HoloFt revealed a semiquantitative description of the iron content and core dispersity of 3400 ± 1600 (2σ) iron atoms. Commercially prepared HS-ApoFt was estimated to still contain an average of 240 iron atoms. These iron abundance and dispersity results suggest the use of STJ cryodetection MS for the clinical analysis of iron deficient/overload diseases.
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Base de dados:
MEDLINE
Idioma:
En
Revista:
Anal Chem
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
Estados Unidos