In the yeast Saccharomyces cerevisiae, nuclear DNA-encoded tRNA Lys CUU is partially imported into mitochondria. We previously found that the synthetic transcripts of yeast tRNA Lys and a number of their mutant versions could be specifically internalized by isolated yeast and human mitochondria. The mitochondrial targeting of tRNA Lys in yeast was shown to depend on the cytosolic precursor of mitochondrial lysyl-tRNA synthetase and the glycolytic enzyme enolase. Here we applied the approach of in vitro selection (SELEX) to broaden the spectrum of importable tRNA-derived molecules. We found that RNAs selected for their import into isolated yeast mitochondria have lost the potential to acquire a classical tRNA-shape. Analysis of conformational rearrangements in the importable RNAs by in-gel fluorescence resonance energy transfer (FRET) approach permitted us to suggest that protein factor binding and subsequent import require formation of an alternative structure, different from a classic L-form tRNA model. We show that in the complex with targeting protein factor, enolase 2, tRK1 adopts a particular conformation characterized by bringing together the 39-end and the TCC loop. This is a first evidence for implication of RNA secondary structure rearrangement in the mechanism of mitochondrial import selectivity. Based on these data, a set of small RNA molecules with significantly improved efficiency of import into yeast and human mitochondria was constructed, opening the possibility of creating a new mitochondrial vector system able to target therapeutic oligoribonucleotides into deficient human mitochondria.

Yeast tRNA vys g is nucleus-encoded and is partially imported into the mitochondria. Another lysine isoacceptor, tRNA vys , is also nucleus-encoded but is not imported. These two tRNAs differ in 21 bases. We have previously localised import selectivity determinants in the anticodon arm. By in vitro import of mutant transcripts and by expression of mutant tRNA genes in vivo we show here that the first base pair (1:72) and the discriminator base 73 are also relevant to import selectivity. Replacement of bases 1 :72 in tRNA vys by those of tRNA vys g makes it importable with a transport efficiency similar to natural.z 1999 Federation of European Biochemical Societies.

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We present a quantitative study of the current-voltage characteristics (CVC) of SFIFS Josephson junctions (S denotes bulk superconductor, F -metallic ferromagnet, I -insulating barrier) with weak ferromagnetic interlayers in the diffusive limit. The problem is solved in the framework of the nonlinear Usadel equations. We consider the case of a strong tunnel barrier such that the left SF and the right FS bilayers are decoupled. We calculate the density of states (DOS) in SF bilayers using a self-consistent numerical method. Then we obtain the CVC of corresponding SFIFS junctions, and discuss their properties for different set of parameters including the thicknesses of ferromagnetic layers, the exchange field, and the magnetic scattering time. We observe the anomalous nonmonotonic CVC behavior in case of weak ferromagnetic interlayers, which we ascribe by DOS energy dependencies in case of small exchange fields in F layers.

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We present a quantitative study of the density of states (DOS) in SF bilayers (where S is a bulk superconductor and F is a ferromagnetic metal) in the diffusive limit. We solve the quasiclassical Usadel equations in the structure considering the presence of magnetic and spin–orbit scattering. For practical reasons, we propose the analytical solution for the density of states in SF bilayers in the case of a thin ferromagnet and low transparency of the SF interface. This solution is confirmed by numerical calculations using a self-consistent two-step iterative method. The behavior of DOS dependencies on magnetic and spin–orbit scattering times is discussed.

Currently, the superconducting diode effect (SDE) is being actively discussed, due to its large application potential in superconducting electronics. In particular, superconducting hybrid structures, based on three-dimensional (3D) topological insulators, are among the best candidates, due to their having the strongest spin–orbit coupling (SOC). Most theoretical studies on the SDE focus either on a full numerical calculation, which is often rather complicated, or on the phenomenological approach. In the present paper, we compare the linearized and nonlinear microscopic approaches in the superconductor/ferromagnet/3D topological insulator (S/F/TI) hybrid structure. Employing the quasiclassical Green’s function formalism we solve the problem self-consistently. We show that the results obtained by the linearized approximation are not qualitatively different from the nonlinear solution. The main distinction in the results between the two methods was quantitative, i.e., they yielded different supercurrent amplitudes. However, when calculating the so-called diode quality factor the quantitative difference is eliminated and both approaches result in good agreement.

We present the quantitative study of the density of states (DOS) in SF bilayers (where S - is a bulk superconductor and F - a ferromagnetic metal) in the diffusive limit. We solve the quasiclassical Usadel equations in the structure, considering the presence of magnetic and spin-orbit scattering. For practical reasons we propose the analytical solution for the density of states in SF bilayer in case of thin ferromagnet and low transparency of the SF interface. It is confirmed by numerical calculations, using a self-consistent two-step iterative method. The behavior of DOS dependencies on magnetic and spin-orbit scattering times is discussed.