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R B Frankel

Publications and source records attributed to R B Frankel.

41 records · Page 3Linked to original sources
PubMed1973

Synthetic analogs of the active sites of iron-sulfur proteins. Structure and properties of bis(o-xylyldithiolato-m2-sulfidoferrate (3)), an analog of the 2Fe-2S proteins.

The synthetic analog approach has been applied to a clarification of the active sites of 2Fe-2S(*) proteins. The compound (Et(4)N)(2)[FeS(SCH(2))(2)C(6)H(4)](2), derived from o-xylyl-alpha,alpha'-dithiol, has been prepared and its structure has been determined by x-ray diffraction. The centrosymmetric anion contains two tetrahedrally coordinated ferric ions bridged by two sulfide ions and separated by 2.70 A. Comparison of electronic, Mössbauer, and proton magnetic resonance spectra and magnetic susceptibility of the anion with the corresponding properties of the oxidized forms of the proteins reveals significant degrees of similarity. The anion also exhibits the essential redox capacity of the proteins. We conclude that [FeS(SCH(2))(2)C(6)H(4)](2) (2-) possesses the same total oxidation level and electronic configuration as the active sites of the oxidized proteins, and that its structure provides a feasible representation of the minimal structure of the active site. [FeS(SCH(2))(2)C(6)H(4)](2) (2-) is thus the first well-defined synthetic analog of the active sites of two-iron ferredoxins.

Binding Sites↗
PubMedDate not supplied

Magnetoferritin: characterization of a novel superparamagnetic MR contrast agent.

A protein-encaged superparamagnetic iron oxide has been developed and characterized by using horse spleen apoferritin as a novel bioreactive environment. The roughly spherical magnetoferritin molecules, 120 A in diameter, are composed of a monocrystalline maghemite or magnetite core 73 A +/- 14 in diameter. Except for the additional presence of iron-rich molecules of higher molecular weight, the appearance and molecular weight (450 kd) of magnetoferritin are identical to that of natural ferritin; the molecules are externally indistinguishable from their precursor, with a pI (isoelectric point) in the range 4.3-4.6. The measured magnetic moment of the superparamagnetic cores is 13,200 Bohr magnetons per molecule, with T1 and T2 relaxivities (r1 and r2) of 8 and 175 L.mmol-1 (Fe).sec-1, respectively, at body temperature and clinical field strengths. The unusually high r2/r1 ratio of 22 is thought to arise from ideal core composition, with no evidence of crystalline paramagnetic inclusions. T2 relaxation enhancement can be well correlated to the field-dependent molecular magnetization, as given by the Langevin magnetization function, raised to a power in the range 1.4-1.6. With its nanodimensional biomimetic protein cage as a rigid, convenient matrix for complexing a plethora of bioactive substances, magnetoferritin may provide a novel template for specific targeting of selected cellular sites.

Animals↗
PubMedDate not supplied

A new frontier for prescription drug services.

To help payers and patients achieve the full value of their prescription drug benefit, the next frontier of managed pharmacy services will be improving individual health outcomes, raising employee productivity and lowering a plan's overall medical costs.

Cost Control↗