Date of Award


Document Type

Union College Only

Degree Name

Bachelor of Science






Old Yellow Enzyme (OYE) has been the subject of extensive research since the early 1930's. However, the structure of OYE was not determined until 1994, and its physiological function still remains a mystery. Investigations into the function of OYE involve uncovering the details of protein-substrate interactions through the use of x-ray crystallography. OYE is known to oxidize NADPH, but attempts to crystallize the OYE-NADPH bound complex have been hampered by the presence of chloride in the active site of OYE. This competition prevents an accurate assessment of the structure of OYE bound to NADPH. This study will examine the possibility of determining crystallization or soaking conditions for OYE in which there is no chloride in the active site. Three experiments were employed with this design. First, we attempted to grow OYE crystals in the absence of chloride. Unfortunately there were no positive signs of the ability to grow crystals of OYE without chloride. The second experiment involved transferring crystals to increasingly dilute solutions containing MgCl2. This was only effective until a concentration of 0.16 M MgCl2 at which point the crystals cracked. In the final experiment, crystals were transferred into a solution identical to the reservoir solution in which the 0.2 M MgCl2 had been replaced with 0.2 M MgS04. Although the crystals survived this transfer, our data still shows the presence of chloride in the active site. This technique is still being actively investigated.