A study of the indicator pigment isolated from the slime mould Physarum Flavicomum

Hillier, Judith Margaret (1975) A study of the indicator pigment isolated from the slime mould Physarum Flavicomum. Masters thesis, Memorial University of Newfoundland.

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Abstract

The slime mould Physarum flavicomum exhibits synchronous nuclear divisions and has been widely used to study the biochemical changes which take place on differentiation. One example of this, sporulation, has been shown to require light and the plasmodial pigments have been implicated as possible photocatalysts or photoreceptors. In order to fully understand this process it is necessary to know the chemical structure of the pigments. One pigment shows changes in absorption maxima with variations in the pH of the solution and has been called the “indicator” pigment. It is with this pigment that the present investigation is concerned. -- The pigment was isolated and purified using a modification of the method employed Khalil. Elemental analyses gave empirical formulae of C₁₂.₁H₁₃.₁O₅N for the protonated pigment and C₁₁.₂H₁₆.₅O₇.₂N Na and C₁₂.₃H₁₃.₉O₇.₇N Na₂.₅ for the sodium salt of the pigment. The n.m.r. spectrum agrees with a high degree of unsaturation in the pigment molecule. -- The presence of the tetraene, identified by Khalil, was confirmed by oxidation experiments. Hydrolysis indicated the presence of a carbohydrate, possibly sorbose, and basic compounds which were isolated, by several methods, as their hydrochlorides, but were not identified. -- Pigment isolated from frozen plasmodia had a molecular mass of approximately 1880, determined by oxidation techniques, and a low E1%/1cm value of 200. This pigment yielded five amino acids on hydrolysis, two of which were tentatively identified as glycine and alanine. There was also evidence, on hydrolysis, of an amino sugar which was possibly glucosamine. It is suggested that this pigment contains a peptide. -- Khalil proposed a tetraene conjugated to a 2,4-pyranone system to be the chromophore of the pigment. In order to investigate this possibility, compounds were synthesized by reacting triacetic acid lactone at the 3 and 6α positions. On of the products, 4-hydroxy-6-(4-(2-furyl)buta-2,4-dienyl)-2H-pyran-2-one, had the same absorption maximum as the pigment but the hyperchromic, bathochromic shifts it displayed on acidification were not as great as those shown by the pigment. However, it does represent the best model system for the pigment available at the present time.

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