Advisor(s) - Committee Chair
Dr. Kevin Williams (Director), Dr. Darwin Dahl, Dr. Lester Pesterfield
Department of Chemistry
Master of Science
Since the discovery of anti-tumor activity of cisplatin in 1960, significant progress has been made in treating metastatic or advanced cancer with cisplatin and platinum compounds. Platinum compounds covalently bind to DNA and disrupt DNA function. They are also known to bind with amino acids like methionine, histidine and cysteine to form cisplatin-protein adducts which are responsible for most of its cytotoxicity and side effects. Recent articles on cisplatin-protein have shown that adding bulky adjuncts to cisplatin or using different platinum compounds varies the degree and extent of reaction thus possibly reducing cisplatin resistance and side effects.
One of the proteins to study is cytochrome C, which is an intermediate in apoptosis (a controlled form of cell death used to kill cells in the process of development or in response to infection or DNA damage). Cytochrome C activates caspase 9, a cysteine protease, which in turn goes on to activate caspases 3 and 7, which are responsible for destroying the cell from within.
In this study, we tried to examine how various platinum compounds like cis-Pt(NH3)2Cl2, cis-Pt(NH3)2(NO3)2, Pt(en)(NO3)2, Pt(Me4en)(NO3)2, Pt(NH3)2 (oxalate), Pt(en)(oxalate),Pt(Me4en)(oxalate), which have different ligands/bulk, react with cytochrome C in different physiological conditions.
This research project subsequently focused on three main aspects: 1) to determine whether the concentration of platinum compounds made a difference in the reaction rate, 2) to determine whether the pH of the buffer shows any difference in the reaction rate, 3) to determine how the ligands coordinated to the platinum affected the rate. We used 1) HPLC with vitamin B12 (cyanocobalamin) as an internal standard. 2) Separate samples of platinum compounds with bovine serum albumin were then subjected to dialysis and were then sent to the Materials Characterization Center for analysis by ICP-AES spectroscopy.
In summary, the following conclusions are stated: •The leaving group, pH, bulk and the concentration play a very vital role in determining the reaction rate for platinum-cytochrome C interactions. •Chlorides form excellent leaving groups followed by oxalates then nitrates. •Pt(en) reacts faster than Pt(NH3)2 which reacts faster than Pt(Me4en). •Nitrates, Pt(en) and few oxalate form multiple products showing non-specific binding. Only cis-Pt(NH3)2Cl2 and Pt(Me4en)(oxalate) formed predominately a single product showing target specific binding. •cis-Pt(NH3)2Cl2 showed an increased reaction rate at lower pH while cis-Pt(NH3)2(NO3)2 and Pt(Me4en)(NO3)2 showed higher reactions at higher pH. •Despite platinum compound was present in significant molar excess relative to cytochrome C, at the end of 21 hrs there was a significant amount of unreacted cytochrome C left except in case of cis-Pt(en)Cl2 which reacted with the whole cytochrome C in less than ten minutes. •We saw the rate of reaction in order of cis-Pt(en)Cl2 > Pt(en)(oxalate) > cis-Pt(NH3)2Cl2 > Pt(en)(NO3)2 > cis-Pt(NH3)2(NO3)2 > cis-Pt(NH3)2(oxalate) > Pt(Me4en)(oxalate) > Pt(Me4en)(NO3)2
Chemistry | Medicinal-Pharmaceutical Chemistry
Kotadia, Nayna, "A Study on the Protein Interaction with Different Platinum Compounds" (2008). Masters Theses & Specialist Projects. Paper 8.