• Athel Cornish-Bowden

      Articles written in Journal of Biosciences

    • Two centuries of catalysis

      Athel Cornish-Bowden

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    • Enthalpy—entropy compensation: a phantom phenomenon

      Athel Cornish-Bowden

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      Enthalpy—entropy compensation is the name given to the correlation sometimes observed between the estimates of the enthalpy and entropy of a reaction obtained from temperature-dependence data. Although the mainly artefactual nature of this correlation has been known for many years, the subject enjoys periodical revivals, in part because of the frequent excellence of the correlation. As with other cases of impossibly good correlation between two biological variables, the explanation is that what purports to be two variables are very largely the same variable looked at in two different ways

    • Synergy between verapamil and other multidrug -resistance modulators in model membranes

      Madeleine Castaing Alain Loiseau Athel Cornish-Bowden

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      Various cationic lipophilic compounds can reverse the multidrug resistance of cancer cells. Possible interaction between these compounds, which are known as modulators, has been assessed by measuring leakage of Sulphan blue from anionic liposomes, induced both by verapamil alone and by verapamil in combination with diltiazem, quinine, thioridazine or clomipramine. An equation was derived to quantify the permeation doses and Hill coefficients of the drugs and mixtures between them by simultaneous fitting of the experimental data. The interaction was tested by two methods, the competition plot and the isobole method; both showed synergy between verapamil and each of diltiazem, quinine and thioridazine. The dose factor of potentiation for verapamil determined within membranes was 4.0 ± 0.4 with diltiazem, 3.2 ± 0.4 with quinine and 2.4 ± 0.3 with thioridazine. The results suggest that the effectiveness of reversing multidrug resistance may be increased with modulators such as verapamil and diltiazem that have a much greater effect in combination than what would be expected from their effects when considered separately.

    • Clipboard: Monitoring the energy status of a living organism in real time

      Athel Cornish-Bowden

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    • A weak link in metabolism: the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis

      Enrique Meléndez-Hevia Patricia De Paz-Lugo Athel Cornish-Bowden María Luz Cárdenas

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      In a previous paper, we pointed out that the capability to synthesize glycine from serine is constrained by the stoichiometry of the glycine hydroxymethyltransferase reaction, which limits the amount of glycine produced to be no more than equimolar with the amount of C1 units produced. This constraint predicts a shortage of available glycine if there are no adequate compensating processes. Here, we test this prediction by comparing all reported fluxes for the production and consumption of glycine in a human adult. Detailed assessment of all possible sources of glycine shows that synthesis from serine accounts for more than 85% of the total, and that the amount of glycine available from synthesis, about 3 g/day, together with that available from the diet, in the range 1.5–3.0 g/day, may fall significantly short of the amount needed for all metabolic uses, including collagen synthesis by about 10 g per day for a 70 kg human. This result supports earlier suggestions in the literature that glycine is a semi-essential amino acid and that it should be taken as a nutritional supplement to guarantee a healthy metabolism.

    • Biochemistry and evolutionary biology: Two disciplines that need each other

      Athel Cornish-Bowden Juli Peretó María Luz Cárdenas

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      Biochemical information has been crucial for the development of evolutionary biology. On the one hand, the sequence information now appearing is producing a huge increase in the amount of data available for phylogenetic analysis; on the other hand, and perhaps more fundamentally, it allows understanding of the mechanisms that make evolution possible. Less well recognized, but just as important, understanding evolutionary biology is essential for understanding many details of biochemistry that would otherwise be mysterious, such as why the structures of NAD and other coenzymes are far more complicated than their functions would seem to require. Courses of biochemistry should thus pay attention to the essential role of evolution in selecting the molecules of life.

    • Enthalpy-entropy compensation and the isokinetic temperature in enzyme catalysis

      ATHEL CORNISH-BOWDEN

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      Enthalpy-entropy compensation supposes that differences in activation enthalpy delta-H-++ for different reactions (or, typically inbiochemistry, the same reaction catalysed by enzymes obtained from different species) may be compensated for bydifferences in activation entropy delta-S-++. At the isokinetic temperature the compensation is exact, so that all samples have thesame activity. These ideas have been controversial for several decades, but examples are still frequently reported asevidence of a real phenomenon, nearly all of the reports ignoring or discounting the possibility of a statistical artefact. Evenfor measurements in pure chemistry artefacts occur often, and they are almost inescapable in enzyme kinetics and otherfields that involve biological macromolecules, on account of limited stability and the fact that kinetic equations are normallyvalid only over a restricted range of temperature. Here I review the current status and correct an error in a recent bookchapter.

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