18 research outputs found
Gaussian and Fourier Transform (GFT) Method and Screened Hartree-Fock Exchange Potential for First-principles Band Structure Calculations
Chemical synthesis of novel taurine-containing uridine derivatives
Recently, novel taurine-containing uridine derivatives were discovered in mammalian mitochondrial tRNAs, and these modified ribonucleosides existed at the first position of the anti-codon. This paper describes the chemical synthesis of these novel uridine derivatives, 5-taurinomethyluridine (Ļm5U) and 5-taurinomethyl-2-thiouridine (Ļm5s2U). These taurine-containing uridine derivatives were synthesized in the good yields by the reaction of the corresponding S-hydroxymethyluridine derivatives with taurine under basic conditions
Gaussian-based range-separation approach on HartreeāFock exchange interaction and second-order perturbation theory
Theoretical Study of the Molecular Passivation Effect of Lewis Base/Acid on Lead-Free Tin Perovskite Surface Defects
Extensive research has been recently conducted to improve
the power
conversion efficiency (PCE) of perovskite solar cells. However, the
charge carriers are easily trapped by the defect sites located at
the interface between the perovskite layer and the electrode, which
decreases the PCE. To reduce such defect sites, the passivation technique
is frequently employed to coat small molecules on the perovskite surface
during the manufacturing process. To clarify the passivation mechanism
from a molecular viewpoint, we performed density functional theory
calculations to target Pb-free Sn perovskites (CH3NH3SnI3). We investigated the passivation effect of
Lewis base/acid molecules, such as ethylene diamine (EDA) and iodopentafluorobenzene
(IPFB), and discussed behaviors of the defect levels within the bandgap
as they have strong negative impacts on the PCE. The adsorption of
EDA/IPFB on the Sn perovskite surface can remove the defect levels
from the bandgap. Furthermore, we discuss the importance of interactions
with molecular orbitals
Chemical Synthesis and Properties of 5-Taurinomethyluridine and 5-Taurinomethyl-2-thiouridine
Improved in-cell structure determination of proteins at near-physiological concentration
Investigating three-dimensional (3D) structures of proteins in living cells by in-cell nuclear magnetic resonance (NMR) spectroscopy opens an avenue towards understanding the structural basis of their functions and physical properties under physiological conditions inside cells. In-cell NMR provides data at atomic resolution non-invasively, and has been used to detect protein-protein interactions, thermodynamics of protein stability, the behavior of intrinsically disordered proteins, etc. in cells. However, so far only a single de novo 3D protein structure could be determined based on data derived only from in-cell NMR. Here we introduce methods that enable in-cell NMR protein structure determination for a larger number of proteins at concentrations that approach physiological ones. The new methods comprise (1) advances in the processing of non-uniformly sampled NMR data, which reduces the measurement time for the intrinsically short-lived in-cell NMR samples, (2) automatic chemical shift assignment for obtaining an optimal resonance assignment, and (3) structure refinement with Bayesian inference, which makes it possible to calculate accurate 3D protein structures from sparse data sets of conformational restraints. As an example application we determined the structure of the B1 domain of protein G at about 250āĪ¼M concentration in living E. coli cells
Ganglioside Synthase Knockout Reduces Prion Disease Incubation Time in Mouse Models
Localization of the abnormal and normal isoforms of prion proteins to detergent-resistant membrane microdomains, lipid rafts, is important for the conformational conversion. Lipid rafts are enriched in sialic acid-containing glycosphingolipids (namely, gangliosides). Alteration in the ganglioside composition of lipid rafts can affect the localization of lipid raft-associated proteins. To investigate the role of gangliosides in the pathogenesis of prion diseases, we performed intracerebral transmission study of a scrapie prion strain Chandler and a Gerstmann-Straussler-Scheinker syndrome prion strain Fukuoka-1 using various knockout mouse strains ablated with ganglioside synthase gene (ie, GD2/GM2 synthase, GD3 synthase, or GM3 synthase). After challenge with the Chandler strain, GD2/GM2 synthase knockout mice showed 20% reduction of incubation time, reduced prion protein deposition in the brain with attenuated glial reactions, and reduced localization of prion proteins to lipid rafts. These results raise the possibility that the gangliosides may have an important role in prion disease pathogenesis by affecting the localization of prion proteins to lipid rafts
Controlling Formation of Single-Molecule Junctions by Electrochemical Reduction of Diazonium Terminal Groups
We report controlling the formation of single-molecule
junctions
by means of electrochemically reducing two axialdiazonium terminal
groups on a molecule, thereby producing direct AuāC covalent
bonds <i>in situ</i> between the molecule and gold electrodes.
We report a yield enhancement in molecular junction formation as the
electrochemical potential of both junction electrodes approach the
reduction potential of the diazonium terminal groups. Step length
analysis shows that the molecular junction is significantly more stable,
and can be pulled over a longer distance than a comparable junction
created with amine anchoring bonds. The stability of the junction
is explained by the calculated lower binding energy associated with
the direct AuāC bond compared with the AuāN bond