Directly revealing the geometric phase effect of dissociative D2+ by two-color strong field photodissociation.

We study the geometric phase (GP) effect of D2+ produced by the encirclement of the dissociated nuclear wavefunction around the light-induced conical intersection (LICI) using a linearly polarized two-color (800 nm and its third harmonic at 266 nm) synthesized laser field. We calculate the photofragment momentum distribution of D2+ with the random orientation by solving the time-dependent Schrödinger equation. We reveal the GP effect that manifests as the Aharonov-Bohm-like interference in the photofragment angular distribution along the direction perpendicular to the linear polarization axis. Our work deepens the understanding of the physical mechanisms of the molecular dynamics when driven by the synthesized strong laser field.

In vitro assembly of the bacterial actin protein MamK from ' Candidatus Magnetobacterium casensis' in the phylum Nitrospirae

Magnetotactic bacteria (MTB), a group of phylogenetically diverse organisms that use their unique intracellular magnetosome organelles to swim along the Earth's magnetic field, play important roles in the biogeochemical cycles of iron and sulfur. Previous studies have revealed that the bacterial actin protein MamK plays essential roles in the linear arrangement of magnetosomes in MTB cells belonging to the Proteobacteria phylum. However, the molecular mechanisms of multiple-magnetosome-chain arrangements in MTB remain largely unknown. Here, we report that the MamK filaments from the uncultivated 'Candidatus Magnetobacterium casensis' (Mcas) within the phylum Nitrospirae polymerized in the presence of ATP alone and were stable without obvious ATP hydrolysis-mediated disassembly. MamK in Mcas can convert NTP to NDP and NDP to NMP, showing the highest preference to ATP. Unlike its Magnetospirillum counterparts, which form a single magnetosome chain, or other bacterial actins such as MreB and ParM, the polymerized MamK from Mcas is independent of metal ions and nucleotides except for ATP, and is assembled into well-ordered filamentous bundles consisted of multiple filaments. Our results suggest a dynamically stable assembly of MamK from the uncultivated Nitrospirae MTB that synthesizes multiple magnetosome chains per cell. These findings further improve the current knowledge of biomineralization and organelle biogenesis in prokaryotic systems.