Recent Developments in Lyotropic Liquid Crystals as Drug Delivery Vehicles - Self-Assembled Supramolecular Architectures: Lyotropic Liquid Crystals - page 246

- sheets, and unordered conforma-
tions, turn together with random coils) during heating from 25 to 70°C in different
hosting media: water, water-fi lled H II phase (fi rst H II system), water - glycerol - fi lled H II
phase (second system), and water-glycerol-fi lled H II phase containing PC (third
system). Each system contains 4 wt % insulin in the polar phase (Amar-Yuli et al.,
2011b ).

Figure 8.21 Insulin secondary structure ( α - helix, β

Comparison of insulin secondary structure during heating from 25 to 70°C
in different hosting media: water, water-fi lled H II phase (fi rst H II system),
glycerol/water - fi lled H II phase (second system), and glycerol/water-fi lled H II
phase containing PC (third system) is shown in Figure 8.21. Each system
depicts the corresponding content of sheets, and unordered confor-

mations (turns together with random coils) of insulin. The dependence of the
insulin secondary structure on prolonged heating (for 60 min) at 60 and 70°C
was tested. The pronounced modifi cations were observed only at 70°C. These
temperatures were selected on the basis of previous reports demonstrating
that the insulin aggregation process begins at 55°C (but is surmised to be too
slow to be detected); however, at 60°C, immediately after the dimer dissocia-
tion, the aggregation process was detectable and accelerated with increasing
temperature (to 70°C) or upon prolonged heating.
All four matrices did not reveal any signifi cant changes in content of the
conformational elements up to 60°C (Fig. 8.21). However, prolonged incuba-
tion of insulin at 60°C for 60 min caused an increase in the

α helix, β

- sheet confi gura-
tions from 25 to 36% only when insulin was confi ned in the water-fi lled H II
phase (fi rst H II system, data not shown). Once the temperature reached 70°C,

β