Fig. 3.

PE-conjugated IgG molecules were able to form a monomer, trimer or polymer with different sizes and shapes. (a) The monomer and trimer are indicated by long and short arrows, respectively. An enlarged image of trimer with a scanning size of 250 nm was shown on the top left corner; three circles underline three PE-conjugated IgG molecules making up the trimer. (b) Shown are images of two hexamers that were formed by an end–end connection of two trimers; three circles indicate three molecules making up a trimer of a hexamer. (c) The image indicates that non-labeled IgG molecules are unable to form end–end connected polymers and circular monolayers even at high concentrations. These molecules distribute dispersedly and irregularly, with no evidence of non-labeled IgG polymers. Scanning size: (a) 1 μm; (b) 0.6 μm; (c) 1 μm. Single monomer and trimer and multimer (hexamer) of PE-labeled IgG were judged based on the size and unique end–end connection of detectable molecules. The monomer indicated by the large arrow in (a) has a diameter of approximately 50–60 nm, which is consistent with the single molecule of PE-labeled IgG. The multimer indicated by the small arrow has a length of approximately 200 nm, which was three-fold larger than that of the monomer of a PE-labeled IgG molecule (about 60 nm). Such a multimer was interpreted as trimer, since its length or size was equivalent to an elongation of three PE-labeled IgG monomers. Similarly, the elongated multimers in (b) was interpreted as a hexamer, since it had an end–end connected length of approximately 400 nm, six-fold longer than the length of a single PE-labeled IgG monomer.