Unexpected branching in pectin observed by atomic force microscopy

Pectic polysaccharides extracted from unripe tomato plant cell walls have been imaged with an atomic force microscope (AFM). The images obtained reveal for the first time a branched structure for tomato pectins that differs from that proposed for the neutral sugar side chains from enzymatic hydrolysis and sugar analysis. The branches are between 30 and 170 nm long and are relatively linear. This work demonstrates that the AFM is uniquely capable of unambiguously identifying, with minimal sample preparation, individual macromolecules within a heterogeneous population.