Chemical Characterization of a Volatile Dubnium Compound, DbOCl3

The formation and the chemical characterization of single atoms of dubnium (Db, element 105), in the form of its volatile oxychloride, was investigated using the on-line gas phase chromatography technique, in the temperature range 350–600 °C. Under the exactly same chemical conditions, comparative studies with the lighter homologues of Group 5 in the Periodic Table clearly indicate the volatility sequence being NbOCl3 > TaOCl3 ≥ DbOCl3. From the obtained experimental results, thermochemical data for DbOCl3 were derived. The present study delivers reliable experimental information for theoretical calculations on chemical properties of transactinides

Combined effect of regulatory polymorphisms on transcription of UGT1A1 as a cause of Gilbert syndrome

<p>Abstract</p> <p>Background</p> <p>Gilbert syndrome is caused by defects in bilirubin UDP-glucuronosyltransferase (UGT1A1). The most common variation believed to be involved is A(TA)7TAA. Although several polymorphisms have been found to link with A(TA)7TAA, the combined effect of regulatory polymorphisms in the development of Gilbert syndrome remains unclear.</p> <p>Methods</p> <p>In an analysis of 15 patients and 60 normal subjects, we detected 14 polymorphisms and nine haplotypes in the regulatory region. We classified the 4-kbp regulatory region of the patients into: the TATA box including A(TA)7TAA; a phenobarbital responsive enhancer module including c.-3275T>G; and a region including other ten linked polymorphisms. The effect on transcription of these polymorphisms was studied.</p> <p>Results</p> <p>All haplotypes with A(TA)7TAA had c.-3275T>G and additional polymorphisms. In an <it>in-vitro </it>expression study of the 4-kbp regulatory region, A(TA)7TAA alone did not significantly reduce transcription. In contrast, c.-3275T>G reduced transcription to 69% of that of wild type, and the linked polymorphisms reduced transcription to 88% of wild type. Transcription of the typical regulatory region of the patients was 56% of wild type. Co-expression of constitutive androstane receptor (CAR) increased the transcription of wild type by a factor of 4.3. Each polymorphism by itself did not reduce transcription to the level of the patients, however, even in the presence of CAR.</p> <p>Conclusions</p> <p>These results imply that co-operation of A(TA)7TAA, c.-3275T>G and the linked polymorphisms is necessary in causing Gilbert syndrome.</p

Correlated Triplet Pair Formation Activated by Geometry Relaxation in Directly Linked Tetracene Dimer (5,5′-Bitetracene)

Singlet fission (SF) materials have the potential to overcome the traditional external quantum efficiency limits of organic light-emitting diodes (OLEDs). In this study, we theoretically designed an intramolecular SF molecule, 5, 5′-bitetracene (55BT), in which two tetracene units were directly connected through a C–C bond. Using quantum chemical calculation and the Fermi golden rule, we show that 55BT undergoes efficient SF induced by geometry relaxation in a locally excited singlet state, ¹(S0S1). Compared with another high-performing SF system, the tetracene dimer in the crystalline state, 55BT has advantages when used in doped systems owing to covalent bonding of the two tetracene units. This feature makes 55BT a promising candidate triplet sensitizer for near-infrared OLEDs

Reevaluation of protein neutron crystallography with and without X-ray/neutron joint refinement

Protein neutron crystallography is a powerful technique to determine the positions of hydrogen atoms, providing crucial biochemical information such as the protonation states of catalytic groups and the geometry of hydrogen bonds. Recently, we determined the crystal structure of a bacterial copper amine oxidase by joint refinement using X-ray and neutron diffraction data sets at resolutions of 1.14 A and 1.72 A, respectively (Murakawa, T. et al. (2020). Proc. Natl Acad. Sci. USA, 117, 10818?10824). While the joint refinement is effective for determination of the accurate positions of heavy atoms on the basis of the electron density, the structural information of light atoms (hydrogen and deuterium) derived from the neutron diffraction data might be affected by the X-ray data. To unravel the information included in the neutron diffraction data, we conducted the structure determination again using only the neutron diffraction data at a 1.72 A resolution and compared the results with those obtained by the previous study. Most hydrogen and deuterium atoms were identified at essentially the same positions in both the neutron-only and X-ray/neutron joint refinements. Nevertheless, the neutron-only refinement was found to be less effective than the joint refinement in providing very accurate heavy atom coordinates that lead to significant improvement of the neutron scattering length density map, especially for the active-site cofactor. Consequently, we have confirmed that the X-ray/neutron joint refinement is crucial for determination of the real chemical structure of the catalytic site of the enzyme