Detection of polysaccharides using Carbotrace 680 relies on regularly occurring units joined by glycosidic linkages. The specific type of glycosidic linkage and the occurrence of branches allow Carbotrace 680 to differentiate between different types of glucans. By means of its structure-responsive properties, Carbotrace 680 can differentiate between β(1-4) linked cellulose and α(1-4) configured amylose, but it can also detect differences between amylose and amylopectin, which contains α(1-6) linked branches.
Since starches from different sources often differ by the length of glucose chains or the amylose/amylopectin ratio, and the protein and fat content of the storage organs, Carbotrace 680 can distinguish between different source of starch like starch obtained from corn or potato.
Monitoring freshly obtained potato starch granules with Carbotrace 680 shows very fine details of the morphology of native starch granules at a sub-cellular scale. The movie shows Carbotrace 680 fluorescence when bound to potato starch granules while stepping through a stack of images collected on the confocal microscope. The most intense green fluorescence is observed on the exposed surface and the outer layer of granules, decreasing towards the core. Faint striations, likely corresponding to alternating layers in crystalline and amorphous lamina were observed in the larger granules. This pattern is likely attributed to differences in polysaccharide packing density in each lamina.
Movie: Carbotrace 680 fluorescence when bound to potato starch granules while stepping through a stack of images collected on the confocal microscope. The movie is reproduced from Choong et al. 2019 (CC BY 4.0)