Highly ordered merocyanine dye assemblies by supramolecular polymerization and hierarchical self-organization.
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Journal Article↗
Biomedical subjects
Sheng Yao
Publications and source records attributed to Sheng Yao.
[Potential role of JAK/STAT in regulating Toll-like receptor 2 gene expression in rats with postburn Staphylococcus aureus sepsis].
OBJECTIVE: To investigate the potential role of Janus kinase/signal transducers and activators of transcription (JAK/STAT) signal transduction pathway in regulating Toll-like receptor 2 (TLR2) gene expression in postburn Staphylococcus aureus infection. METHODS: Thirty-eight male Wistar rats were randomly divided into four groups as follows: normal control group (n=6), postburn sepsis group (n=12), AG490 treatment group (n=10) and Rapamycin (RPM) treatment group (n=10). Tissue samples from the liver, kidneys and lungs were collected to determine TLR2 and TNF-alpha mRNA expressions. RESULTS: It was found that, 0.5 and 2 hours after Staphylococcus aureus challenge, TLR2 mRNA expressions in the liver, kidneys and lungs from postburn septic animals were up-regulated rapidly (P<0.05 or P<0.01). Treatment with RPM could effectively inhibit TLR2 mRNA expressions in the liver and kidneys. However, TLR2 mRNA expressions in the above tissues from AG490 treated animals had no significant differences with those from normal controls. Two hours after Staphylococcus aureus challenge, TNF-alpha mRNA expressions in the liver, kidneys and lungs were also increased markedly (all P<0.01). Both treatment with RPM and AG490 could significantly inhibit the up-regulation of all tissue TNF-alpha mRNA expressions (P<0.05 or P<0.01), and AG490 were more significant in liver and kidneys (both P<0.01). CONCLUSION: It is suggested that scald injury combined with Staphylococcus aureus infection can up-regulate TLR2 expression, which appears to be associated with the signal transduction of STAT.
Animals↗
Dimerization of merocyanine dyes. Structural and energetic characterization of dipolar dye aggregates and implications for nonlinear optical materials.
Aggregation of polar merocyanine dyes has been identified as an important problem in the fabrication of organic materials for photonic applications. In this work, a series of merocyanine dyes is synthesized, and their aggregation is investigated by a combination of several experimental techniques to reveal structure-property relationships. These studies provide clear evidence for the formation of centrosymmetric dimers for all investigated merocyanines in concentrated solution and in the solid state. The thermodynamics of dimerization in liquid solution is studied by concentration-dependent permittivity measurements, UV-vis spectroscopy, and electrooptical absorption experiments. A centrosymmetric dimer structure with antiparallel ordering of the dipole moments is observed in solution by 2D NMR spectroscopy as well as in the solid state by X-ray crystallography and interpreted in terms of dipolar and pi-pi interactions. The optical properties of the dimer aggregates are satisfactorily explained by an excitonic coupling model. The effect of an external electric field on the dimerization equilibrium is considered and quantitatively determined by electrooptical absorption measurements. Implications of the observed findings on the design of nonlinear optical and photorefractive materials are discussed.
Journal Article↗
Activation of the Bur1-Bur2 cyclin-dependent kinase complex by Cak1.
Cyclin-dependent kinases (Cdks) were originally identified as regulators of eukaryotic cell cycle progression, but several Cdks were subsequently shown to perform important roles as transcriptional regulators. While the mechanisms regulating the Cdks involved in cell cycle progression are well documented, much less is known regarding how the Cdks that are involved in transcription are regulated. In Saccharomyces cerevisiae, Bur1 and Bur2 comprise a Cdk complex that is involved in transcriptional regulation, presumably mediated by its phosphorylation of the carboxy-terminal domain (CTD) of the largest subunit of RNA polymerase II. To investigate the regulation of Bur1 in vivo, we searched for high-copy-number suppressors of a bur1 temperature-sensitive mutation, identifying a single gene, CAK1. Cak1 is known to activate two other Cdks in yeast by phosphorylating a threonine within their conserved T-loop domains. Bur1 also has the conserved threonine within its T loop and is therefore a potential direct target of Cak1. Additional tests establish a direct functional interaction between Cak1 and the Bur1-Bur2 Cdk complex: Bur1 is phosphorylated in vivo, both the conserved Bur1 T-loop threonine and Cak1 are required for phosphorylation and Bur1 function in vivo, and recombinant Cak1 stimulates CTD kinase activity of the purified Bur1-Bur2 complex in vitro. Thus, both genetic and biochemical evidence demonstrate that Cak1 is a physiological regulator of the Bur1 kinase.
Cyclin-Dependent Kinases↗
Fluorene-based fluorescent probes with high two-photon action cross-sections for biological multiphoton imaging applications.
Two-photon fluorescence microscopy is a powerful tool for the study of dynamic cellular processes and live-cell imaging. Many commercially available fluorescent probes have been used in multiphoton-based imaging studies despite exhibiting relatively low two-photon absorption cross-section values in the tunability range of ultrafast Ti:sapphire lasers commonly used in multiphoton microscopy imaging. Furthermore, available fluorophores may be plagued with low fluorescence quantum yield and/or photoinstability (i.e., photobleaching) on exposure to the high peak power and photon density provided by the ultrafast laser source. To address the demand for better performing dyes, we prepare fluorophores tailored for multiphoton imaging. These fluorophores are based on the fluorene ring system, known to exhibit high fluorescence quantum yield (>0.7) and high photostability. Furthermore, an amine-reactive fluorescent probe for the covalent attachment onto amine-containing biomolecules is also prepared. Epi-fluorescence and two-photon fluorescence microscopy images of H9c2 rat cardiomyoblasts stained with an efficient two-photon absorbing fluorene fluorophore is demonstrated. Additionally, single-photon spectral characteristics of the amine-reactive fluorophore, as well as the two-photon absorption cross sections of its model adduct in solution, and spectral characterization of a bovine serum albumin (BSA) as a model bioconjugate are presented.
Animals↗