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Biomedical subjects

J A Fee

Publications and source records attributed to J A Fee.

At least 109 records · Page 6Linked to original sources
PubMed1975

The behavior of holo- and apo-forms of bovine superoxide dismutase at low pH.

1. Holo-superoxide dismutase from bovine erythrocytes has been shown to undergo a reversible structural modification in the pH 3-5 range. 2. The spectral alterations observed on changing from neutrality to pH 2 were: a slight attenuation of the 680 nm absorbance; the loss of the 450 nm shoulder, apparent in the optical spectrum of the native protein; and a new band appeared at 330 nm. The circular dichroism at 600 nm was essentially lost while a weak negative band appeared at approx. 380 nm and a positive band at 310 nm. 3. The EPR spectrum was also modified on changing from the native to the low pH form: A parallel increased from approximately 130 to approximately 150 G, g parallel remained unchanged at approximately 2.27, and gm decreased from approximately 2.09 to approximately 2.08. The apparent linewidth remained essentially constant. 4. High resolution (220 MHz) PMR spectra of holo- and apoproteins revealed that the metals influence the three-dimensional structure of the protein. 5. PMR studies indicated that at pH 3 the apoprotein existed almost entirely in a random coil form and that it assumed a compact well-ordered structure on returning to neutral pH. The holoprotein maintained a compact, apparently dimeric, structure even at pH 3.

Animals↗
PubMed1975

A physical explanation of the EPR spectrum observed during catalysis by enzymes utilizing coenzyme B12.

We have proposed that the "doublet" EPR spectra observed during catalysis by a number of coenzyme B12-requiring enzymes arises from a weak electrostatic exchange interaction between an organic free radical and low spin Co(II), B12r. By varying the magnitude of the exchange of coupling we have quite accurately simulated the published EPR spectra from the enzyme systems: diol dehydrase, glycerol dehydrase, ribonucleotide reductase, and ethanolamine ammon-ia lyase. A dipolar model was shown to be incompatible with the observed properties of these systems.

Ammonia-Lyases↗
PubMed1975

Studies on the reconstitution of bovine erythrocyte superoxide dismutase. V. Preparation and properties of derivatives in which both zinc and copper sites contain copper.

1. We have developed a procedure for preparing derivatives of bovine superoxide dismutase in which primarily the Cu binding sites are occupied by Cu2+ (2 Cu2+-) and in which both the Zn and Cu binding sites are occupied by Cu2+ (4 Cu2+-). 2. The 2 Cu2+ protein shows approximately one-half the superoxide dismutase activity of an equivalent amount of native protein. A two-fold enhancement of the activity of 2 Cu2+-dismutase was observed upon occupation of the Zn sites either with Zn2+ or Cu2+. 3. The electron paramagnetic resonance spectrum of 4 Cu2+ protein was recorded over the temperature range 5-100 degrees K and the results suggest an antiferro-magnetic interaction between Cu2+ in the Zn site and Cu2+ in the Cu site having a coupling constant of approx. 52 cm-1. 4. The binuclear Cu2+ complex was found to accept only one electron from ferrocyanide. 5. One-half the total Cu+ of dithionite reduced 4 Cu+ protein was found to react rapidly with bathocupreine sulfonate whereas the other half reacted slowly. Reduced native protein did not react with bathocupreine sulfonate below 70 degrees C.

Animals↗