Occupancy Regulation Research Articles

Luminescence improvement via site environment adjustment and site occupancy regulation of Eu2+ in Ca8MgSi4O16Cl2

Phosphors emitting cyan-green light with a small Stokes shift under blue light excitation is crucial for addressing spectral deficiencies in phosphor-converted white light-emitting diodes (pc-wLEDs). In this work, a series of Mg2+ ion doped and Mg2+-Th3+ (ThGa,In) ion pair co-doped Ca8MgSi4O16Cl2: Eu2+ phosphors were synthesized using a high-temperature solid-phase reaction method. It is found that the doped Mg2+ ions can improve the local environment of Eu2+ ions thus enhance its luminescence, while the doped Th3+ (ThGa,In) can regulate the distribution of Eu2+ ions occupying hexa-coordinated and octa-coordinated Ca2+ sites. It is proven that co-doping Mg2+-Ga3+ ion pair facilitates more Eu2+ ions enter the octa-coordinated Ca2+ sites, which largely enhances the cyan-green emission intensity. A pc-wLEDs device with a color rendering index (CRI) of 97.2 and a correlated color temperature (CCT) of 3480K has been fabricated combining the present Ca7Ga0.9Mg1.9Si3.1O16Cl2:0.1Eu2+ phosphor, commercial yellow and red phosphors with blue LED chip. It is found that Ca7Ga0.9Mg1.9Si3.1O16Cl2:0.1Eu2+ phosphor can partially fill the cyan gap of the pc-wLEDs spectra, enhancing the emission quality of the pc-wLEDs device.

Spin occupancy regulation of the Pt d-orbital for a robust low-Pt catalyst towards oxygen reduction

Disentangling the limitations of O-O bond activation and OH* site-blocking effects on Pt sites is key to improving the intrinsic activity and stability of low-Pt catalysts for the oxygen reduction reaction (ORR). Herein, we integrate of PtFe alloy nanocrystals on a single-atom Fe-N-C substrate (PtFe@FeSAs-N-C) and further construct a ferromagnetic platform to investigate the regulation behavior of the spin occupancy state of the Pt d-orbital in the ORR. PtFe@FeSAs-N-C delivers a mass activity of 0.75 A mgPt−1 at 0.9 V and a peak power density of 1240 mW cm−2 in the fuel-cell, outperforming the commercial Pt/C catalyst, and a mass activity retention of 97%, with no noticeable current drop at 0.6 V for more than 220 h, is attained. Operando spectroelectrochemistry decodes the orbital interaction mechanism between the active center and reaction intermediates. The Pt dz2 orbital occupation state is regulated to t2g6eg3 by spin-charge injection, suppressing the OH* site-blocking effect and effectively inhibiting H2O2 production. This work provides valuable insights into designing high-performance and low-Pt catalysts via spintronics-level engineering.

Substrate-dependent cluster density dynamics of Corynebacterium glutamicum phosphotransferase system permeases.

SummaryMany bacteria take up carbohydrates by membrane‐integral sugar specific phosphoenolpyruvate‐dependent carbohydrate:phosphotransferase systems (PTS). Although the PTS is centrally involved in regulation of carbon metabolism in different bacteria, little is known about localization and putative oligomerization of the permease subunits (EII). Here, we analyzed localization of the fructose specific PtsF and the glucose specific PtsG transporters, as well as the general components EI and HPr from Corynebacterium glutamicum using widefield and single molecule localization microscopy. PtsF and PtsG form membrane embedded clusters that localize in a punctate pattern. Size, number and fluorescence of the membrane clusters change upon presence or absence of the transported substrate, and a direct influence of EI and HPr was not observed. In presence of the transport substrate, EII clusters significantly increased in size. Photo‐activated localization microscopy data revealed that, in presence of different carbon sources, the number of EII proteins per cluster remains the same, however, the density of these clusters reduces. Our work reveals a simple mechanism for efficient membrane occupancy regulation. Clusters of PTS EII transporters are densely packed in absence of a suitable substrate. In presence of a transported substrate, the EII proteins in individual clusters occupy larger membrane areas.

Nanog induces suppression of senescence through downregulation of p27KIP1 expression

A comprehensive analysis of the molecular network of cellular factors establishing and maintaining pluripotency as well as self renewal of pluripotent stem cells is key for further progress in understanding basic stem cell biology. Nanog is necessary for the natural induction of pluripotency in early mammalian development but dispensable for both its maintenance and its artificial induction. To gain further insight into the molecular activity of Nanog, we analyzed the outcomes of Nanog gain-of-function in various cell models employing a recently developed biologically active recombinant cell-permeant protein, Nanog-TAT. We found that Nanog enhances the proliferation of both NIH 3T3 and primary fibroblast cells. Nanog transduction into primary fibroblasts results in suppression of senescence-associated β-galactosidase activity. Investigation of cell cycle factors revealed that transient activation of Nanog correlates with consistent downregulation of the cell cycle inhibitor p27KIP1 (also known as CDKN1B). By performing chromatin immunoprecipitation analysis, we confirmed bona fide Nanog-binding sites upstream of the p27KIP1 gene, establishing a direct link between physical occupancy and functional regulation. Our data demonstrates that Nanog enhances proliferation of fibroblasts through transcriptional regulation of cell cycle inhibitor p27 gene.

Abstract 804: The impact of aromatase inhibitor therapy on ER co-regulator expression and interaction

Abstract Estrogen receptor alpha (ERα) is a member of the nuclear receptor family and is currently recognized as the most defining metric in breast cancer diagnosis and treatment. Roughly 70% of all breast cancer patients present with ERα-positive, hormone sensitive disease, and the majority of these women are post-menopausal. Because post-menopausal women require the aromatase enzyme for estrogen synthesis, the first line of treatment for these patients is aromatase inhibitor (AI) therapy. Despite the number of women whose primary disease responds positively, a significant fraction of patients fail to gain any clinical benefit due to intrinsic resistance, or eventually relapse due to acquired resistance to AI therapy. Currently, the biochemical changes underlying both intrinsic and acquired resistance to AI therapy is yet unknown; thus, resistance to AI therapy remains a significant clinical obstacle for a large fraction of breast cancer patients. Here, we investigate the impact of ERα co-regulators on intrinsic and acquired AI resistance in breast cancer. In vitro administration of testosterone to wild-type MCF-7, T47-D, or ZR75-1 cells is capable of offering a significant ERα-dependent proliferative advantage, suggesting an active role for aromatase in these cells. Interestingly, aromatase inhibitor (Anastrazole) treatment of these cells alters the expression of specific ERα co-regulators independent of ligand. Furthermore, interaction between ERα and individual co-regulators is altered after treatment with estradiol or testosterone, and is impacted by Anastrazole treatment acutely. While these findings are preliminary, further investigation is on-going and promises to provide critical insight into the contributions of ERα co-regulators to the short- and long-term response to AI-mediated estrogen deprivation, as well as establish the alterations in ERα-mediated promoter occupancy and gene regulation that contribute to intrinsic and acquired AI resistance. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 804. doi:1538-7445.AM2012-804

Proportional Service Differentiation in Wireless LANs Using Spacing-based Channel Occupancy Regulation

In this paper, we propose Spacing-based Channel Occupancy Regulation (SCORE) MAC protocol for wireless LANs that provides proportional service differentiation in terms of normalized throughput. As shown by our system model and simulation study, SCORE provides consistent, scalable and adjustable proportional differentiation for any network size, any service class distribution, any node data rate and any packet size. Compared to state-of-the-art prioritized service differentiation schemes like Enhanced Distributed Coordination Function (EDCF), SCORE can quantitatively control the channel sharing between different service classes. Moreover, SCORE obtains significant performance improvements in terms of higher network throughput, higher transmission efficiency, lower medium access delay and lower delay jitter.