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Biomedical subjects

F H Malpress

Publications and source records attributed to F H Malpress.

At least 19 recordsLinked to original sources
PubMed1984

The coulombic hypothesis of mitochondrial energy transduction: an attempt to quantify relationships in the energized zones.

From a consideration of (i) an assumed maximal respiration rate (ii) the ATP synthesis which can be obtained from mitochondria after respiratory inhibition and (iii) electrophoretic mobility data, the number of energized zones on the mitochondrial inner membrane has been assessed as 0.68 X 10(18)/g protein. For a single zone (representing one electron transport chain, three phosphorylating complexes and three fixed-charge cycles) in which all the cycles use molecular species doubly-charged in the energized form (b2-), the zone area will be 134 A2 and the specialized fixed charge concentration 4.5 X 10(-2) sigma/A2. The lifetime ("blink") of any energized form will be 24.4 ms, 5% of the cycle repeat time when a site 1 substrate is being oxidized.

Adenosine Triphosphate↗
PubMed1984

A coulombic hypothesis of mitochondrial oxidative phosphorylation.

A coulombic hypothesis of mitochondrial oxidative phosphorylation is presented, founded upon the evidence for negative fixed charge formation during electron transport chain activity. The intermediary force is electrostatic (psi H) and not electrochemical (delta mu H). The electrochemical potential of the chemiosmotic hypothesis is identified as a "phantom" parameter which owes its delusive existence to the procedures by which it is measured. The connection between psi H and the conditional delta mu H values is examined; it entails the use of a variable conversion factor, f, where delta mu H (mV) = f psi H, and the concept of the "protonic status" of the diffuse double layer. A number of problems which beset the chemiosmotic view are reappraised in the light of the new interpretation, and find authentic solutions.

Adenosine Triphosphate↗
PubMed1984

Local energized proton hypotheses of mitochondrial oxidative phosphorylation.

Two hypotheses are compared each interpreting mitochondrial energy transduction in terms of a localized form of proton activity. Their differences are seen to be profound and far-reaching. It is concluded that the "chemiosmotic/local energized proton dialogue" as conducted hitherto has offered a very incomplete and restricted analysis of the problems of mitochondrial oxidative phosphorylation.

Electron Transport↗
PubMed1979

Oxygen-pulse curves in rat liver mitochondrial suspensions. Some observations and deductions.

1. The inference, implicit in the chemiosmotic hypothesis, that protons move into the bulk phase during ATP synthesis was investigated. 2. Incubation of rat liver mitochondria in the presence of the cation exchanger CM-Sephadex C-50 caused alkalinization in the medium, though total ATP synthesis remained unchanged. The addition of N-ethylmaleimide prevented the alkalinization, but there was still no indication of protons passing into the medium. The expected proton movement [Mitchell & Moyle (1967) Biochem. J. 105, 1147--1162] was readily detected when as an equivalent acid pulse. 3. Analysis of delta H+ decay curves after O2 pulses (3 micrograms-atoms of O/g of protein) indicated the presence of fast and slow components of decay, with first-order rate constants (k) of 0.24s-1 and 0.032s-1. The fast decay was finite and was eliminated in the presence of N-ethylmaleimide. 4. These observations are interpreted as evidence for the development of unmasking of fixed charges on the outer surface of the mitochondrial inner membrane during energization and for the existence of proton-retentive electrical fields (rho-zones) on this surface. The charge concentration is calculated as about 1 charge/10nm2. 5. A cycle of changes in a single fixed-charge molecule is proposed which mediates both Ca2+ uptake and the first step in the utilization of the rho-zone protonmotive force, delta p rho.

Adenosine Triphosphate↗
PubMed1966

Studies on human alpha(s)- and kappa-casein fractions and human caseinoglycomacropeptide.

1. Fractions have been obtained from human whole casein closely resembling the alpha(s)- and kappa-fractions of cow casein. 2. The alpha(s)-fraction (human alpha(s)-casein) is calcium-sensitive, heterogeneous in zone analysis and inert towards rennin. 3. The kappa-fraction (human kappa-casein) is calcium-insensitive, heterogeneous in zone analysis, and forms a soluble glycopeptide when acted upon by rennin. 4. Human kappa-casein stabilizes human alpha(s)-casein in the presence of Ca(2+) ions. 5. The glycopeptides released by rennin from human casein and from cow casein have been compared. There are important differences in both the peptide and non-peptide structures of the two compounds. 6. In both human and bovine glycopeptides some of the carbohydrate residues are joined to the peptide by O-glycosidic links with threonine, and possibly with serine.

Journal Article↗