RESUMO
An essential feature of the mechanism of nitrogenase, the enzyme responsible for biological nitrogen fixation, is the formation of a transient electron transfer complex between the MoFe protein containing the active site at which N2 is reduced, and the Fe protein, which functions as a specific electron donor to the MoFe protein. We have obtained high quality solution X-ray scattering data using synchrotron X-rays of a stable putative electron transfer complex, (MoFe-protein)(Fe-protein.ADP.AIF4)2, of Klebsiella pneumoniae and used the model-independent approach based on the multipole expansion method to provide a stable and unique shape restoration at approximately 15 A resolution. The biological significance of this first molecular structure of a nitrogenase complex is discussed.
Assuntos
Klebsiella pneumoniae/enzimologia , Molibdoferredoxina/química , Nitrogenase/química , Azotobacter vinelandii/química , Transporte de Elétrons , Modelos Moleculares , Nitrogênio/metabolismo , Conformação Proteica , Espalhamento de Radiação , Raios XRESUMO
The operation of a pulsed, watt-level, low-pressure far infrared (FIR) laser is described. Single mode output powers of 0.1-1 W are obtained from several molecular gases in the 300-1200 microm region. Plasma diagnostic applications are discussed.