Which came first, the chicken or the egg? Scientists aren't any closer to answering that question, but they have figured out how the egg forms. According to a study published  this month in Angewandte Chemie International Edition, a protein called OC-17 provides the catalyst for one of nature's most elegant creations. Researchers used a computer simulation to track the formation of eggshells, which are composed mostly of calcium carbonate. In the simulation, the OC-17 protein (illustration, left), which is found only in the hard part of the eggshell, clamps its molecular fingers onto a microscopic particle of calcium carbonate (right). That creates a nucleus, from which the calcium carbonate can crystallize. When the particle nucleus gets big enough, OC-17 can no longer hold onto it. The molecule's fingers detach, leaving it free to grab onto another nucleus and repeat the process. The chain reaction continues until the eggshell has formed. The research, says the team, could someday help scientists grow other types of crystals, such as those needed to house quantum computers or superconducting materials.
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