For AFM inspection, 40-μl sample aliquots were centrifuged at 1700 × g for 5 min using an Eppendorf 5417R centrifuge. The pellet was suspended in an equal volume of water, and a 10-μl aliquot was deposited on freshly cleaved mica and dried under mild vacuum. Tapping mode AFM images were acquired in air using a Dimension 3100 Scanning Probe Microscope equipped with a “G” scanning head (maximum scan size 100 μm) and driven by a Nanoscope IIIa controller, and a Multimode Scanning Probe Microscope equipped with “E” scanning head (maximum scan size 10 μm), driven by a Nanoscope V controller (Digital Instruments, Bruker). Single beam uncoated silicon cantilevers (type OMCL-AC160TS, Olympus) were used. The drive frequency varied between 280 and 330 kHz, the scan rate was between 0.4 and 0.7 Hz. Height and width of imaged objects were measured from the corresponding cross-section profiles in topographic AFM images. Widths at half-height were measured to correct tip size effects (20 (link)) and standard errors are reported. The object volume V was calculated from the equation,
where h is the imaged object height and a is its half-corrected width (20 (link)).
where h is the imaged object height and a is its half-corrected width (20 (link)).