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A new quasi-one-dimensional compound Ni8Bi8SI is synthesized and its crystal structure determined from single-crystal x-ray diffraction data. Analysis of chemical bonding reveals strong multicenter Ni-Bi bonds and pair Ni-S interactions within the compound.

The effects of sodium counterion presence and chain length on structure and dynamics of single DNA strands of polythymidylate were studied by molecular dynamics simulations. The results show that the importance of base-base stacking phenomenon increases with chain length and partially reduces flexibility of the strand.

O 2 formation in photosystem II (PSII) is a vital event on Earth, but the exact mechanism remains unclear. The presently prevailing theoretical model is "radical coupling" (RC) involving a Mn(IV)-oxyl unit in an "open-cubane" Mn 4 CaO 6 cluster, which is supported experimentally by the S 3 state of cyanobacterial PSII featuring an additional Mn-bound oxygenic ligand. However, it was recently proposed that the major structural form of the S 3 state of higher plants lacks this extra ligand, and that the resulting S 4 state would feature instead a penta-coordinate dangler Mn(V)=oxo, covalently linked to a "closed-cubane" Mn 3 CaO 4 cluster. For this proposal, we explore here a large number of possible pathways of O-O bond formation and demonstrate that the "nucleophilic oxo-oxo coupling" (NOOC) between Mn(V)=oxo and μ 3 -oxo is the only eligible mechanism in such a system. The reaction is facilitated by a specific conformation of the cluster and concomitant water binding, which is delayed compared to the RC mechanism. An energetically feasible process is described starting from the valid S 4 state through the sequential formation of peroxide and superoxide, followed by O 2 release and a second water insertion. The newly found mechanism is consistent with available experimental thermodynamic and kinetic data and thus a viable alternative pathway for O 2 formation in natural photosynthesis, in particular for higher plants.