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Biomedical subjects

M C Falk

Publications and source records attributed to M C Falk.

41 records · Page 3Linked to original sources
PubMed1976

Synthetic flavinyl peptides related to the active site of mitochondrial monoamine oxidase II. Fluorescence properties.

The fluorescence properties of various 8alpha-sulfur-linked flavinyl peptides and related flavin analogues were investigated as the pH solvent, temperature, and flavin concentration were varied. Substitution in the 8alpha position by a thioether-linked peptide brings about a marked quenching of fluorescence (up to 98% in water), a slight bathochromic shift and broadening of the fluorescence emission spectra, and a slight decrease in the fluorescence lifetimes. Oxidation of the thioether function to a sulfone partially releases this fluorescence quenching without further changes in the fluorescence emission spectra. The primary effect on the fluorescence intensity is due to an interaction between the nonbonding electrons of the thioether, the hydrogen-bonding, polar solvent, and the isoalloxazine ring. Dissolving these flavinyl peptides in nonaqueous solvents increases the fluorescence intensity as much as 20-fold. A secondary effect on flavinyl fluorescence can be attributed to a collisional quenching by the vicinal tyrosyl residue within tyrosine-containing flavinyl peptides. The fluorescence properties provide further confirmation of the identity of the synthetic and naturally obtained flavinyl peptides and of the interaction between the free-hydroxyl functions of the ribityl side chain and the thioether.

Binding Sites↗
PubMedDate not supplied

Wire-induced osteogenesis in marrow.

Although it has been reported, in observations connected to electrically stimulated bone repair, that intramedullary electrodes not attached to any electrical source can also induce osteogenesis, there has been only one systematic attempt to study this effect per se. We have extended these studies, implanting selected metal and plastic wires longitudinally into the medullary diaphyses of rat femora. Atomic absorption analysis was used for the first time in analyzing for medullary calcium. This technique and the histologic evaluation clearly indicate that osteogenesis occurs within 2 weeks after this wire implantation. Osteogenesis was not observed when the wire was immediately removed after the original trauma of wire insertion.

Animals↗
PubMedDate not supplied

FMN cofactor dissociation from the soluble hydrogenase of Alcaligenes eutrophus H16.

The specific activity of purified soluble hydrogenase of Alcaligenes eutrophus H16 was found to vary with enzyme concentration. Specific activity as a function of concentration of purified enzyme could be fit to an equation describing the dissociation of a compound into two components. An association constant, kappa(a), was determined in this way to be 39.4 +/- 8.7 micrograms protein/ml. The concentration of the enzyme affected its kinetic parameters: a tenfold decrease in enzyme concentration caused by a reduction of the V(max) and Kappa(m) (NAD) values to 45% and 58%, respectively, of the values for undiluted (0.64 mg/ml) enzyme. Diaphorase (NAD-dependent reduction of benzyl viologen) specific activity of the hydrogenase was unaffected by dilution. The extent of dilution-induced activity loss was dependent on pH, with greater activity loss observed at higher pH values. The substrate NAD prevented loss of specific activity due to dilution, while the product NADH did not. Specific activity loss due to dilution as reversed with the addition of the cofactor FMN. Dilution of the hydrogenase caused an increase in the enzyme's specific flavin fluorescence. These results suggest that dilution of the soluble hydrogenase of Alcaligenes eutrophus causes dissociation of the cofactor FMN, and this activity loss should be taken into account as an important factor governing hydrogenase activity and kinetic properties.

Alcaligenes↗