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The photocatalytic hydrogen (H2) generation by boron (B) and phosphorus (P) codoped silicon quantum dots (Si QDs) with diameters in the quantum confinement regime is investigated. The codoped Si QDs have an amorphous shell made from B, Si and P. The shell induces negative potential on the surface and makes codoped Si QDs dispersible in water. The hydrophilic shell offers enhanced stability and efficiency in photocatalytic H2 generation and provides the opportunity to study the size dependence of the H2 generation rate. A drastic increase of H2 generation rate with decreasing QD size is observed. Analyses based on the Marcus theory reveal that the upper shift of the lowest unoccupied molecular orbital level of Si QDs by the quantum confinement effect is responsible for the enhanced photocatalytic activity. [ABSTRACT FROM AUTHOR]

Haem substitution is an effective approach to tweak the function of haemoproteins. Herein, we report a facile haem substitution method for self-sufficient cytochrome P450BM3 (CYP102A1) from Bacillus megaterium utilising the transpeptidase Sortase A from Staphylococcus aureus. We successfully constructed Mn-substituted BM3 and investigated its catalytic activity. [ABSTRACT FROM AUTHOR]

Heavily boron and phosphorus codoped silicon quantum dots (QDs) are dispersible in water without organic ligands and exhibit near infrared luminescence. We summarize the fundamental properties and demonstrate the formation of a variety of nanocomposites. [ABSTRACT FROM AUTHOR]

Si1−xGex alloy nanocrystals potentially have superior properties compared to Si nanocrystals such as an enhanced absorption cross-section and wider controllability of the band gap energy. However, reports on the synthesis of Si1−xGex alloy nanocrystals, especially colloidal Si1−xGex alloy nanocrystals, are still very limited and the quality is not as high as that of colloidal Si nanocrystals. Here, we report the development of a new type of luminescent colloidal Si1−xGex alloy nanocrystals of 3 to 6 nm in diameter. The characteristic feature of the Si1−xGex alloy nanocrystals is the formation of a high B and P concentration layer on the surface. The shell provides inorganic atomic ligands and B and P co-doped Si1−xGex nanocrystals can be dispersed in alcohol without any surface functionalization processes. [ABSTRACT FROM AUTHOR]

Resonance Raman (RR) spectra of the oxygenated and FeIVO reaction intermediates of indoleamine 2,3-dioxygenase (IDO) are reported. Absorption and RR spectra reveal that the electronic and geometric structures of the two respective species at pH 6.5 and pH 8.0 are the same, although the enzymatic activity at pH 6.5 is 6 times higher than at pH 8.0. The results thus further support our current understanding that the FeIVO heme species is the active species in the IDO reaction cycle, although its presence was unexpected. The Fe–O2and the O–O stretching frequencies of the IDO-Trp-O2ternary complex at Trp concentrations of 50 μM and 8 mM are essentially identical. These results suggest that “substrate inhibition” of enzymatic activity occurs by binding of a second substrate molecule to an unknown binding site and not to the heme pocket. [ABSTRACT FROM AUTHOR]

The O2-binding carboxylate-bridged diiron site in DcrH-Hr was engineered in an effort to perform the H2O2-dependent oxidation of external substrates. A His residue was introduced near the diiron site in place of a conserved residue, Ile119. The I119H variant promotes the oxidation of guaiacol and 1,4-cyclohexadiene upon addition of H2O2. [ABSTRACT FROM AUTHOR]

The use of biological host-guest interactions, specifically the binding of hemoprotein to heme, has attracted significant research interest in the design of artificial protein assemblies. However, because of the inherent flexibility of the propionic acid group of heme, it is difficult to control the positioning and orientation of the protein unit and to construct well-ordered structures. Herein, we report a heme-substituted protein dimer composed of the native hemoprotein HasA, which accommodates a tetraphenylporphyrin bearing an additional metal coordination site. The specific binding of the tetraphenylporphyrin with an additional metal coordination site that protrudes in a fixed direction confines the configuration of the dimer structure to a defined bent form. The small-angle X-ray scattering profile shows the dimer structure with a bent form and suggests dynamic rotational behavior while keeping its bent-core structure, resembling a bevel gear. This unique dimer structure demonstrates that the design of heme-substituted protein assemblies can be expanded to protein assemblies while maintaining the rotational freedom of the individual protein units., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The O2-binding carboxylate-bridged diiron site in DcrH-Hr was engineered in an effort to perform the H2O2-dependent oxidation of external substrates. A His residue was introduced near the diiron site in place of a conserved residue, Ile119. The I119H variant promotes the oxidation of guaiacol and 1,4-cyclohexadiene upon addition of H2O2.

The crystal structure of a truncated Aer2, a signal transducer protein from Pseudomonas aeruginosa, consisting of the heme-containing PAS and di-HAMP domains revealed that a distal tryptophan residue (Trp283) plays an important role in stabilizing the heme-bound O(2) and intra-molecular signal transduction upon O(2) binding.