28 research outputs found
Ge/Si nanowire mesoscopic Josephson junctions
The controlled growth of nanowires (NWs) with dimensions comparable to the
Fermi wavelengths of the charge carriers allows fundamental investigations of
quantum confinement phenomena. Here, we present studies of proximity-induced
superconductivity in undoped Ge/Si core/shell NW heterostructures contacted by
superconducting leads. By using a top gate electrode to modulate the carrier
density in the NW, the critical supercurrent can be tuned from zero to greater
than 100 nA. Furthermore, discrete sub-bands form in the NW due to confinement
in the radial direction, which results in stepwise increases in the critical
current as a function of gate voltage. Transport measurements on these
superconductor-NW-superconductor devices reveal high-order (n = 25) resonant
multiple Andreev reflections, indicating that the NW channel is smooth and the
charge transport is highly coherent. The ability to create and control coherent
superconducting ordered states in semiconductor-superconductor hybrid
nanostructures allows for new opportunities in the study of fundamental
low-dimensional superconductivity
Changes in the proteome of pea (Pisum sativum L.) seeds germinating under optimal and osmotic stress conditions and subjected to post-stress recovery
Circadian oscillator proteins across the kingdoms of life : Structural aspects 06 Biological Sciences 0601 Biochemistry and Cell Biology
Circadian oscillators are networks of biochemical feedback loops that generate 24-hour rhythms and control numerous biological processes in a range of organisms. These periodic rhythms are the result of a complex interplay of interactions among clock components. These components are specific to the organism but share molecular mechanisms that are similar across kingdoms. The elucidation of clock mechanisms in different kingdoms has recently started to attain the level of structural interpretation. A full understanding of these molecular processes requires detailed knowledge, not only of the biochemical and biophysical properties of clock proteins and their interactions, but also the three-dimensional structure of clockwork components. Posttranslational modifications (such as phosphorylation) and protein-protein interactions, have become a central focus of recent research, in particular the complex interactions mediated by the phosphorylation of clock proteins and the formation of multimeric protein complexes that regulate clock genes at transcriptional and translational levels. The three-dimensional structures for the cyanobacterial clock components are well understood, and progress is underway to comprehend the mechanistic details. However, structural recognition of the eukaryotic clock has just begun. This review serves as a primer as the clock communities move towards the exciting realm of structural biology
Using Upgrading Strategy and Analytics to Provide Agility to Clothing Manufacturing Subsidiaries: With a Case Study
Additional regulatory activities of MrkH for the transcriptional expression of the Klebsiella pneumoniae mrk genes: Antagonist of H-NS and repressor
Mechanics, thermodynamics, and kinetics of ligand binding to biopolymers.
Ligands binding to polymers regulate polymer functions by changing their physical and chemical properties. This ligand regulation plays a key role in many biological processes. We propose here a model to explain the mechanical, thermodynamic, and kinetic properties of the process of binding of small ligands to long biopolymers. These properties can now be measured at the single molecule level using force spectroscopy techniques. Our model performs an effective decomposition of the ligand-polymer system on its covered and uncovered regions, showing that the elastic properties of the ligand-polymer depend explicitly on the ligand coverage of the polymer (i.e., the fraction of the polymer covered by the ligand). The equilibrium coverage that minimizes the free energy of the ligand-polymer system is computed as a function of the applied force. We show how ligands tune the mechanical properties of a polymer, in particular its length and stiffness, in a force dependent manner. In addition, it is shown how ligand binding can be regulated applying mechanical tension on the polymer. Moreover, the binding kinetics study shows that, in the case where the ligand binds and organizes the polymer in different modes, the binding process can present transient shortening or lengthening of the polymer, caused by changes in the relative coverage by the different ligand modes. Our model will be useful to understand ligand-binding regulation of biological processes, such as the metabolism of nucleic acid. In particular, this model allows estimating the coverage fraction and the ligand mode characteristics from the force extension curves of a ligand-polymer system