Iron from micellar solutions

A carbon monoxide (CO)-saturated dichloromethane solution containing the Fe(III) complex with 1-ethylimidazole was vigorously stirred with an aqueous solution of sodium dithionite under a CO atmosphere. The dichloromethane solution was evaporated to dryness, and the residue was heated to about 80 C in vacuo to remove the coordinating CO molecule from the complex. Water was added to the powdery iron-porphyrin polymer with shaking to yield a micellar solution of the iron-porphyrin polymer Structure (4). 

X-ray contrast variation has been best applied to the metalloprotein ferritin, which consists of a mineral iron core (electron density - 1000 e nm ) surrounded by a spherical protein shell (410 enm ) of 24 regularly-arranged subunits [149,158-160]. The protein shell was matched out in 53% sucrose (w/w) or 0.66 g sucrose/ml solution, leaving the observed scattering to be caused only by the iron core (Fig. 17). Control experiments were performed on apoferritin which lacks the iron core [149,160]. Thus the Rq for native ferritin is 3.7 nm, that of apoferritin is 5.6 nm and that of the iron core is 2.9 nm [158-160]. The outer and inner radii of the protein of ferritin were found to be 6.3 and 3.55 nm [160]. The radius of the iron core was found to be 3.66 nm and corresponded well to the scattering from a uniform sphere [149], rather than to other models based on a collection of spherical micellar domains that were proposed from electron microscopy studies (Fig. 17). 

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