3.3 Characteristic size of biological macromolecules
Dissolving in 20 mM AmAc, serially-diluted samples were prepared and the
correlation between the protein concentration and size distribution was
investigated. At 10-1 mg/ml scale of the protein
concentration in electrolyte, only the BSA exhibited clear and separate
peaks among size distribution, as shown in Figure 3(A) . Based
on the electrophoretic mobility of NP, the primary peak, the
representative size, was 6.9 nm, and the dimer (8.8 nm), and trimer
(10.2 nm) of BSA could be clearly recognized [17]. On the other
hand, the ubiquitin, LDL, and HDL possessed wider range of size
distribution and the positions of monomer, dimer, and etc., were obscure
(Figure 3 (B) -(D) ). At the concentration of
10-3 mg/ml, the representative sizes of ubiquitin
revealed and were 3.6 nm and the dimer was 4.6 nm for ubiquitin.
Although a primary peak at 10.2 nm and 20.9 nm extinguished in HDL and
LDL sample at 10-3 mg/ml protein concentration, the
emergence of multiple peaks with inconsistent relation between size and
number could not be explained by the theory of NP charging efficiency
[20]. Consequently, HDL and LDL that possessed unknown
electrophoretic behavior was not considered as the RM in this article.