Reversible Photoinduced Reductive Elimination of H2 from the Nitrogenase Dihydride State, the E(4)(4H) Janus Intermediate.

ABSTRACT: We recently demonstrated that N2 reduction by nitrogenase involves the obligatory release of one H2 per N2 reduced. These studies focus on the E4(4H) "Janus intermediate", which has accumulated four reducing equivalents as two [Fe-H-Fe] bridging hydrides. E4(4H) is poised to bind and reduce N2 through reductive elimination (re) of the two hydrides as H2, coupled to the binding/reduction of N2. To obtain atomic-level details of the re activation process, we carried out in situ 450 nm photolysis of E4(4H) in an EPR cavity at temperatures below 20 K. ENDOR and EPR measurements show that photolysis generates a new FeMo-co state, denoted E4(2H)*, through the photoinduced re of the two bridging hydrides of E4(4H) as H2. During cryoannealing at temperatures above 175 K, E4(2H)* reverts to E4(4H)

SUBMITTER: Lukoyanov D 

PROVIDER: S-EPMC4773049 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature