Growing Egg Shells

For a long time scientists have believed that a chicken egg shell protein called ovocledidin-17 (OC-17) played a part in the formation of egg shells. This protein is only found in the mineral region of the egg which is the hard part of the shell, and, it appears to influence the transformation of amorphous calcium carbonate into calcite crystals by acting as a catalyst for crystal growth.

Scientists have now created simulations to show how the protein binds to the amorphous calcium carbonate surface using two clusters of arginine residues located on two loops of the OC-17 protein and creating a chemical clamp to nano sized particles of calcium carbonate. While clamped in this way, the OC-17 protein encourages the nanoparticles of calcium carbonate to transform into calcite crystallites that form the tiny nucleus of crystals that can continue to grow on their own. When the crystal nucleus is sufficiently large to grow on its own, the OC-17 protein desorbs, or, falls off. This frees up the OC-17 protein to promote yet more crystallization.

Reference:
Colin L. Freeman, John H. Harding, David Quigley, P. Mark Rodger. Structural Control of Crystal Nuclei by an Eggshell Protein. Angewandte Chemie International Edition, 2010; 49 (30): 5135 DOI: 10.1002/anie.201000679

Study Questions

1. What are the elements common to all proteins?
2. Proteins are actually polymers. What is the name given to the monomers that make up a protein?
3. What kind of bond binds these monomers together within the protein?
4. What is the formula for arginine?
5. Would the "loops" referred to in reference to the structure of OC-17 be part of its primary, secondary or tertiary structure? Explain your answer.
6. What does the term amorphous mean?
7. How does amorphous calcium carbonate differ from calcite crystals?
8. What is the definition of a catalyst?
9. Do you think OC-17 could be accurately described as a catalyst? Explain your answer.