Fig. 1.

Insulin spherulites observed by polarized optical microscopy. (A) Representative polarized optical microscopy images of insulin spherulites formed by incubating solutions containing 1 mM insulin at pH 2.0 and 65°C for several hours. A distribution of spherulite sizes is clearly observable. (B Left) Insulin spherulites, as viewed between crossed polars. (B Right) Differential interference contrast microscopy shows that the central region of the spherulites is made up of material that is not oriented in a regular manner. (Scale bar, 50 μm.)