INSTITUTE COLLOQUIUM ON LEARNING FROM NATURE TO DEVELOP A CATALYST FOR THE FACILE CONVERSION OF METHANE TO METHANOLS

IIT Bombay is organising Institute Colloquium on Tuesday,  November 3, 2009.  

The details are as follows:

Speaker: Prof. Sunny Chang

               Emeritus Professor

               California Institute of Technology, USA

Topic:   Learning from Nature to Develop a Catalyst for the Facile Conversion of Methane to Methanols

Date:      Tuesday, November 3, 2009

Time & Venue :  4.30 pm, F. C. Kohli Auditorium

--------------------------------------------------------------------------------------------------

Abstract : The  particulate  methane  monooxygenase  (pMMO)  is  a  membrane-bound enzyme  that  mediates  the  facile  conversion  of  methane  to  methanol under ambient  conditions  of  temperature  and  pressure.  In  this lecture, I  shall summarize efforts to obtain the purified pMMO in high yields and high specific activity  from  the  methanotrophic  bacteria Methylococcus  capsulatus (Bath)  for structural  and  biochemical characterization  (1).  The  pMMO  is  a multi-copper protein  containing ~15  copper  ions.  The  enzyme  utilizes  a  unique tricopper cluster to activate dioxygen for “O-atom” transfer to small alkanes and alkenes.

Both  the  hydroxylation  and  epoxidation  proceed  with  total retention  of configuration  of  the  carbon  centers  oxidized.  This novel  O-atom transfer chemistry  will  be  discussed  within  the context  of  the  recent X-ray  crystal structure  of  the  enzyme  (2). Based  on  this  new  chemistry,  an effort  is  now  in progress  to develop  an  artificial  catalyst  for  similar  controlled oxidation  of organic substrates, including the facile conversion of methane to methanol in the laboratory.  Several  trinuclear  [CuICuICuI]3+  clusters  have been synthesized  that are  capable  of  mediating  facile  O-atom insertion  across  C-C  and  C-H  bonds when  they  become  activated  by dioxygen  at  room  temperature  (3). This chemistry mimics the mechanism of hydroxylation of small alkanes that has been implicated in the pMMO. These results will also be presented.

(1)  Chan  SI,  Yu  SSF.  2008.  Controlled  oxidation  of  hydrocarbons by  the membrane- bound methane monoxygenase: The case for a tricopper cluster.Acc. Chem. Res. 41:969–979.

(2) Lieberman RL, Rosenzwig AC. 2005. Crystal structure of a membrane-bound metalloenzyme  that  catalyzes  the  biological  oxidation  of  methane. Nature 434:177–182.

(3)  Chen  PPY,  Yang  RBG,  Lee  JCM,  Chan  SI.  2007.  Facile  O-atom insertion  into C–C  and  C–H  bonds  by  a  trinuclear  copper  complex designed  to harness  a “singlet oxene.” Proc. Natl. Acad. Sci. USA 104:14570–14575.