Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: January 1, 2009
Publication Date: April 1, 2009
Citation: Fish, W.W. 2009. Nature’s packaging and organization of carotenoids in watermelon and cantaloupe chromoplasts [abstract]. Federation of American Societies for Experimental Biology Journal. 23:729.7. Technical Abstract: As a means to better understand factors influencing the bioavailability of carotenoids from natural sources, the properties of plant-derived precipitates of watermelon lycopene and cantaloupe B-carotene were examined in an aqueous environment. Electron microscopy and chemical analyses revealed that carotenoids from both plant sources were packaged inside membranes to form chromoplasts. Watermelon chromoplasts ranged in apparent diameter from 0.1 to 6 um while cantaloupe chromoplasts ranged in apparent diameter between 0.1 to about 1 um. The chromoplasts could be made more water soluble by treatment with sodium dodecyl sulfate (SDS); only SDS in its monomeric state appeared to bind to the membrane to effect solubilization. Binding measurements indicated that about 120 molecules of SDS were bound to the watermelon chromoplast membrane per molecule of lycopene inside the chromoplast. Around 90% of the chromoplast-SDS complexes from both sources were retained on a 0.45 um membrane filter. Carotenoid-containing melon chromoplasts that were dispersed in aqueous SDS obeyed Beer’s law indicating that this system can be used for quantification of lycopene in watermelon or B-carotene in cantaloupe. Chromoplasts in SDS exhibited pronounced circular dichroic activity at visible wavelengths; this is consistent with the carotenoid monomers being assembled into a chiral aggregate inside the membrane.