Hydrogen Bonding and Noncovalent Electric Field Effects in the Photoconversion of a Phytochrome.

A profound understanding of protein structure and mechanism requires dedicated experimental and theoretical tools to elucidate electrostatic and hydrogen bonding interactions in proteins. In this work, we employed an approach to disentangle noncovalent and hydrogen-bonding electric field changes during the reaction cascade of a multidomain protein, i.e.

Activation of the general stress response sigma factor SigB prevents competence development in .

Unlabelled: Seemingly simple bacteria mount intricate adaptive responses when exposed to physical stress or nutrient limitation, and the activation of these responses is governed by complex signal transduction networks. Upon entry into the stationary growth phase, the soil bacterium may develop natural competence, form biofilms or stress-resistant cells, or ultimately trigger a cellular differentiation program leading to spore formation. Master regulators, such as Spo0A, ComK, SinR, and SigB, constantly monitor the bacterium's environment and then determine appropriate adaptive responses.

A bis-Phenolate Carbene-Supported bis-μ-Oxo Iron(IV/IV) Complex with a [Fe(μ-O)Fe] Diamond Core Derived from Dioxygen Activation.

The diiron(II) complex, [(OCO)Fe(MeCN)] (, MeCN = acetonitrile), supported by the bis-phenolate carbene pincer ligand, 1,3-bis(3,5-di--butyl-2-hydroxyphenyl)benzimidazolin-2-ylidene (OCO), was synthesized and characterized by single-crystal X-ray diffraction, H nuclear magnetic resonance, infrared (IR) vibrational, ultraviolet/visible/near-infrared (UV/vis/NIR) electronic absorption, Fe Mössbauer, X-band electron paramagnetic resonance (EPR) and SQUID magnetization measurements. Complex activates dioxygen to yield the diferric, μ-oxo-bridged complex [(OCO)Fe(py)(μ-O)Fe(O(C═O)O)(py)] () that was isolated and fully characterized. In , one of the iron-carbene bonds was oxidized to give a urea motif, resulting in an O(C═O)O binding site, while the other Fe(OCO) unit remained unchanged.

Expanding the scope of resonance Raman spectroscopy in hydrogenase research: New observable states and reporter vibrations.

Oxygen-tolerant [NiFe] hydrogenases are valuable blueprints for the activation and evolution of molecular hydrogen under application-relevant conditions. Vibrational spectroscopic techniques play a key role in the investigation of these metalloenzymes. For instance, resonance Raman spectroscopy has been introduced as a site-selective approach for probing metal-ligand coordinates of the [NiFe] active site and FeS clusters.