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Nature's packaging and organization of carotenoids in watermelon and cantaloupe chromoplasts
Author(s) -
Fish Wayne W.
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.729.7
Subject(s) - chromoplast , carotenoid , lycopene , chemistry , membrane , monomer , rutaceae , chromatography , biochemistry , botany , biology , plastid , organic chemistry , polymer , chloroplast , gene
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 β‐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 μm while cantaloupe chromoplasts ranged in apparent diameter between 0.1 to about 1 μm. 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 μm 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 β‐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.