(a) ATR-FT-IR spectra of cast native IgG dried
film from a demineralized
solution (blue), cast film from thermally induced aggregated IgG solution
(red), and the difference between them (green). The dried native film
was normalized for comparison using the average absorbance between
1300 and 1350 cm–1. (b) ATR-FT-IR spectra of the
buffer (blue), 1 mg/mL native IgG solution (light green), precipitated
aggregates induced by heating a 1 mg/mL IgG solution (red), difference
between the native IgG solution and the buffer (dark green) and its
second derivative (teal), and the difference between the aggregated
IgG and the buffer (fuchsia) and its second derivative (pink). (c)
Schematics illustrating the native IgG (green box) and the increased
local concentration in the volume probed by ATR-FT-IR spectroscopy
caused by heat induced protein aggregates precipitation (red box).