30 research outputs found
A 5 kDa protein (SCS23) from the 30 S subunit of the spinach chloroplast ribosome
AbstractThe proteins of the 30 S ribosomal subunits from spinach chloroplasts were investigated using a radical-free and highly reducing (RFHR) method of two-dimensional polyacrylamide gel electrophoresis (PAGE). Twenty-three proteins were resolved on the gel down to the smallest protein of 5 kDa. The N-terminal amino acid sequence of the 5 kDa protein showed no homology with that of any other protein stored in databases, and the copy numbers were estimated to be 0.88±0.16 and 0.72±0.04 in the 30 S subunits and the 70 S ribosomes, respectively. The results suggest that the 5 kDa protein, which we have called SCS23, may be an essential ribosomal protein specific to spinach chloroplasts
Electronic Control of Spin Alignment in pi-Conjugated Molecular Magnets
Intramolecular spin alignment in pi-conjugated molecules is studied
theoretically in a model of a Peierls-Hubbard chain coupled with two localized
spins. By means of the exact diagonalization technique, we demonstrate that a
spin singlet (S=0) to quartet (S=3/2) transition can be induced by electronic
doping, depending on the chain length, the positions of the localized spins,
and the sign of the electron-spin coupling. The calculated results provides a
theoretical basis for understanding the mechanism of spin alignment recently
observed in a diradical donor molecule.Comment: 4 pages, 4 figures, Physical Review Letters (in press
Theoretical study on novel electronic properties in nanographite materials
Antiferromagnetism in stacked nanographite is investigated with using the
Hubbard-type model. We find that the open shell electronic structure can be an
origin of the decreasing magnetic moment with the decrease of the
inter-graphene distance, as experiments on adsorption of molecules suggest.
Next, possible charge-separated states are considered using the extended
Hubbard model with nearest-neighbor interactions. The charge-polarized state
could appear, when a static electric field is present in the graphene plane for
example. Finally, superperiodic patterns with a long distance in a nanographene
sheet observed by STM are discussed in terms of the interference of electronic
wave functions with a static linear potential theoretically. In the analysis by
the k-p model, the oscillation period decreases spatially in agreement with
experiments.Comment: 8 pages; 6 figures; accepted for publication in J. Phys. Chem.
Solids; related Web site: http://staff.aist.go.jp/k.harigaya/index_E.htm
Competition between spin and charge polarized states in nanographene ribbons with zigzag edges
Effects of the nearest neighbor Coulomb interaction on nanographene ribbons
with zigzag edges are investigated using the extended Hubbard model within the
unrestricted Hartree-Fock approximation. The nearest Coulomb interaction
stabilizes a novel electronic state with the opposite electric charges
separated and localized along both edges, resulting in a finite electric dipole
moment pointing from one edge to the other. This charge-polarized state
competes with the peculiar spin-polarized state caused by the on-site Coulomb
interaction and is stabilized by an external electric field.Comment: 4 pages; 4 figures; accepted for publication in Phys. Rev. B; related
Web site: http://staff.aist.go.jp/k.harigaya/index_E.htm
Flat-band ferromagnetism induced by off-site repulsions
Density matrix renormalization group method is used to analyze how the
nearest-neighbor repulsion V added to the Hubbard model on 1D triangular
lattice and a railway trestle (t-t') model will affect the electron-correlation
dominated ferromagnetism arising from the interference (frustration). Obtained
phase diagram shows that there is a region in smaller-t' side where the
critical on-site repulsion above which the system becomes ferromagnetic is
reduced when the off-site repulsion is introduced.Comment: 4 pages, RevTex, 6 figures in Postscript, to be published in Phys.
Rev.
(Running head: Exciton effects in doped Peierls systems)
Exciton effects in soliton and bipolaron lattice state