6 research outputs found
Effects of different concentrations of topotactic hydrogen impurities on the electronic structure of nickelate superconductors
Infinite-layer nickelate superconductors have recently been discovered to
share both similarities and differences with cuprate superconductors. Notably,
the incorporation of hydrogen (H) through topotactic reduction has been found
to play a critical role in their electronic structure and, consequently, their
superconductivity. In this study, we utilized a theoretical approach combining
density-functional theory and impurity approximation to design three
characteristic multi-orbital Hubbard models representing low, moderate, and
high concentrations of topotactic-hydrogen. Consistent with experimental
findings, our simulations revealed that both low and high concentrations of
topotactic-hydrogen induce high-spin states (=1) that are composed by holes
at and orbitals and consequently the emergent
inter-site hopping between to is unfavorable for
superconductivity. Conversely, an optimal concentration of 25\% H aligns with
the single Ni- band picture of superconductivity in infinite-layer
nickelates, demonstrating its beneficial effect on promoting superconducting
behavior.Comment: 9 pages, 6 figure
A New Searching Strategy for the Identification of O-Linked Glycopeptides
For the analysis of homogeneous post-translational modifications such as protein phosphorylation and acetylation, setting a variable modification on the specific residue(s) is applied to identify the modified peptides for database searching. However, this approach is often not applicable to identify intact mucin-type O-glycopeptides due to the high microheterogeneity of the glycosylation. Because there is virtually no carbohydrate-related tag on the peptide fragments after the O-glycopeptides are dissociated in HCD, we find it is unnecessary to set the variable mass tags on the Ser/Thr residues to identify the peptide sequences. In this study, we present a novel approach, termed as O-Search, for the interpretation of O-glycopeptide HCD spectra. Instead of setting the variable mass tags on the Ser/Thr residues, we set variable mass tags on the peptide level. The precursor mass of the MS/MS spectrum was deducted by every possible summed mass of O-glycan combinations on at most three S/T residues. All the spectra with these new precursor masses were searched against the protein sequence database without setting variable glycan modifications. It was found that this method had much decreased search space and had excellent sensitivity in the identification of O-glycopeptides. Compared with the conventional searching approach, O-Search yielded 96%, 86%, and 79% improvement in glycopeptide spectra matching, glycopeptide identification, and peptide sequence identification, respectively. It was demonstrated that O-Search enabled the consideration of more glycan structures and was fitted to analyze microheterogeneity of O-glycosylation
Continuous Fluorescence Imaging of Intracellular Calcium by Use of Ion-Selective Nanospheres with Adjustable Spectra
Continuous fluorescence imaging of
intracellular ions in various
spectral ranges is important for biological studies. In this paper,
fluorescent calcium-selective nanospheres, including calix[4]arene-functionalized
bodipy (CBDP) or 9-(diethylamino)-5-[(2-octyldecyl)imino]benzo[<i>a</i>]phenoxazine (ETH 5350) as the chromoionophore, were prepared
to demonstrate intracellular calcium imaging in visible or near-IR
regions, respectively. The fluorescence of the nanospheres was controlled
by the chromoionophore, and thus the spectral range for detection
was adjustable by choosing the proper chromoionophore. The response
time of the nanospheres to calcium was typically 1 s, which allowed
accurate measurement of intracellular calcium. These nanospheres were
loaded into cells through free endocytosis and exhibited fluorescence
for 24 h, and their intensity was correlated with the elevation of
intracellular calcium upon stimulation. The successful demonstration
of calcium imaging by use of ion-selective nanospheres within two
spectral ranges in 24 h supported that these nanospheres could be
applied for continuous imaging of intracellular ions with adjustable
spectra