Game Number:     g/L Seed:      


A polypeptide has hormonal activity that delays the progression of symptoms of Alzheimers Syndrome. Several companies have licensed the patents and are rushing to capture the market. The only product currently approved by the FDA is lyophilized from a crude mixture extracted from a mutant bacterial culture. Because of contamination by other proteins and polypeptides, potential side reactions restrict its use to hopeless cases.

The product can be purified by chromatography but tends to isomerize to a molecule with improper folding that induces unacceptable side reactions. As with other peptides, purification by crystalliztion is possible but difficult. Our people have been the first to cyrstallize this polypeptide and have pending patents on the best buffers.

Only our people have obtained crystals from heavily supersaturated solutions (more like colloidal suspensions than true solutions) and have overcome the tendency to form a viscous glop. Your assignment is to develop a crystallization process.


There are several reasons for control of crystal size and size distribution:
  1. Achieve proper bulk density for powders. Powders are often dispensed by volume.
  2. Adjust rate of dissolving.
  3. Change long-term stability, e.g., antibiotics in animal feed where tiny crystals with great surface area are ruined quickly while big crystals persist for days.

Nothing happens unless the concentration is greater than the solubility. When only slightly supersaturated, crystals may not form unles seed crystals are added. The growth rate depends on the driving force. When greatly supersaturated, the high driving force can induce rapid deposition that risks having foreign ions or molecules as part of the crystal because of insufficient time for the correct species to reach its spot in the lattice.

More Javascript Exercises: Biochemical Engineering    Environmental Engineering