Hydrogenases catalyze the reversible oxidation of H(2) into protons and electrons and are usually readily inactivated by O(2). However, a subgroup of the [NiFe] hydrogenases, including the membrane-bound [NiFe] hydrogenase from Ralstonia eutropha, has evolved remarkable tolerance toward O(2) that enables their host organisms to utilize H(2) as an energy source at high O(2). This feature is crucially based on a unique six cysteine-coordinated [4Fe-3S] cluster located close to the catalytic center, whose properties were investigated in this study using a multidisciplinary approach. The [4Fe-3S] cluster undergoes redox-dependent reversible transformations, namely iron swapping between a sulfide and a peptide amide N. Moreover, our investigations unraveled the redox-dependent and reversible occurence of an oxygen ligand located at a different iron. This ligand is hydrogen bonded to a conserved histidine that is essential for H(2) oxidation at high O(2). We propose that these transformations, reminiscent of those of the P-cluster of nitrogenase, enable the consecutive transfer of two electrons within a physiological potential range.

While the power of modern microscopy techniques is undeniable, rigorous record-keeping and quality control are required to ensure that imaging data may be properly interpreted (quality), reproduced (reproducibility), and used to extract reliable information and scientific knowledge which can be shared for further analysis (value). In the absence of agreed guidelines, it is inherently difficult for scientists to create comprehensive records of imaging experiments and ensure the quality of resulting image data or for manufacturers to incorporate standardized reporting and performance metrics. To solve this problem, the 4D Nucleome (4DN) Initiative and BioImaging North America (BINA) here propose light Microscopy Metadata specifications that scale with experimental intent and with the complexity of the instrumentation and analytical requirements. They consist of a set of three extensions of the Open Microscopy Environment (OME) Data Model, and because of their tiered nature they clearly specify which provenance and quality control metadata should be recorded for a given experiment. This endeavor is closely aligned with the undertakings of the recently established QUAlity Assessment and REProducibility in Light Microscopy (QUAREP-LiMi; quarep.org) global community initiative. As a result, the ensuing flexible 4DN-BINA-OME (NBO) framework represents a turning point towards increasing data fidelity, improving repeatability and reproducibility, easing future analysis, and facilitating the verifiable comparison of different datasets, experimental setups, and assays. The intention of this proposal is to encourage participation, critiques, and contributions from all imaging community stakeholders, including research and imaging scientists, facility personnel, instrument manufacturers, software developers, standards organizations, scientific publishers, and funders.

No abstract

For quality, interpretation, reproducibility and sharing value, microscopy images should be accompanied by detailed descriptions of the conditions that were used to produce them. Micro-Meta App is an intuitive, highly interoperable, open-source software tool that was developed in the context of the 4D Nucleome (4DN) consortium and is designed to facilitate the extraction and collection of relevant microscopy metadata as specified by the recent 4DN-BINA-OME tiered-system of Microscopy Metadata specifications. In addition to substantially lowering the burden of quality assurance, the visual nature of Micro-Meta App makes it particularly suited for training purposes.