News on How Insulin Crystals Form

Graphic: Thousands of block-shaped insulin molecules

Peter Vekilov, associate professor of chemical engineering, and Dimitra Georgiou, a recent doctoral graduate in chemical engineering, both in UH's Cullen College of Engineering, are studying the process of how insulin is produced.

Proinsulin, a molecular precursor to insulin itself, is the reason for these crystals. After an insulin molecule is produced from proinsulin, it attaches to an insulin crystal only in special locations where other insulin molecules have formed right angles, called kinks. Using atomic-force microscopy, the scientists discovered a new mechanism by which insulin molecules attach themselves to crystals to form these kinks. They found that groups of insulin blocks create large protrusions, dubbed "mounds" by Vekilov and Georgiou. The very nature of these mounds results in the creation of multiple kinks – far more, in fact, than other methods of kink formation.

By providing so many spaces where insulin molecules can attach to an insulin crystal, these mounds allow for the rapid growth of that crystal and only form when there is a surplus of insulin that allows for rapid crystal growth. Since no mounds appear when there is a lack of insulin and insulin crystals both grow and dissolve at kinks, mounds are important sources of a crystal's net growth.

"Typically in nature, fast growth also results in fast dissolution," Vekilov said. "But this process cheats physics because when there isn't a lot of insulin, mounds don't form. It's an asymmetric mechanism that has no balance." While this discovery will play a significant role in gaining a better understanding of diabetes, it also is an historic find in the area of crystal formation and use, as only the third mechanism of crystal formation ever discovered. Before this finding, there were only two known ways that crystals grew.

"It is possible that crystals composed of materials other than insulin also grow in this manner," Vekilov said. "If so, this discovery could significantly impact any number of fields that deal with crystals."; Source: University of Houston