380-nm Excitation Research Articles

A simple synthesis method for Zn2SiO4:Mn2+ phosphor films and their optical and luminescence properties

We prepared a bright and transparent Zn2SiO4:Mn2+ phosphor film using a simple method through a thermally diffused reaction between quartz (SiO2) substrate and spin-coated ZnO:Mn thin film on a quartz (SiO2) substrate. From X-ray diffraction patterns, our samples revealed some preferred crystal orientations which have (113)-, (223)-, and (333)-crystal planes. Our best sample (Mn/Zn=5at %) showed 40% brightness compared to the commercial powder product under 146nm excitation and it has a short decay time of 4.5ms under 254nm excitation. In addition, transmittance of our film revealed 60% at 525nm wavelength range. These excellent luminescent and optical properties can be explained by morphology of the interface and the unique crystal structure of our Zn2SiO4:Mn2+ film.

Ubiquitin‐specific protease‐like 1 (USPL1) is a SUMO isopeptidase with essential, non‐catalytic functions

Isopeptidases are essential regulators of protein ubiquitination and sumoylation. However, only two families of SUMO isopeptidases are at present known. Here, we report an activity-based search with the suicide inhibitor haemagglutinin (HA)-SUMO-vinylmethylester that led to the identification of a surprising new SUMO protease, ubiquitin-specific protease-like 1 (USPL1). Indeed, USPL1 neither binds nor cleaves ubiquitin, but is a potent SUMO isopeptidase both in vitro and in cells. C13orf22l--an essential but distant zebrafish homologue of USPL1--also acts on SUMO, indicating functional conservation. We have identified invariant USPL1 residues required for SUMO binding and cleavage. USPL1 is a low-abundance protein that colocalizes with coilin in Cajal bodies. Its depletion does not affect global sumoylation, but causes striking coilin mislocalization and impairs cell proliferation, functions that are not dependent on USPL1 catalytic activity. Thus, USPL1 represents a third type of SUMO protease, with essential functions in Cajal body biology.

Synthesis and photoluminescence study of rare earth activated phosphor Na2La2B2O7

The photoluminescence properties in UV and N-UV excitable range for the phosphors of Na2La2B2O7: RE (RE=Eu, Tb, Ce, Sm, Gd) are investigated. The solution combustion synthesis technique was employed for the synthesis of the phosphors Na2La2B2O7: RE. The photoluminescence measurements of the phosphors were carried out on a HITACHI F7000 Fluorescence Spectrophotometer. The PL and PL excitation (PLE) spectra indicate that the main emission wavelength of Na2La2B2O7: Eu are 591 and 615nm, Na2La2B2O7: Ce shows dominating emission peak at 387nm and Na2La2B2O7: Tb displays green emission at 493, 544, 593 and 620nm at 254nm excitation, while Na2La2B2O7: Sm shows the main emission peak wavelengths 566 and 604nm at 405nm excitation and Na2La2B2O7: Gd shows dominating emission peak at 312nm at 274nm excitation. These phosphors may provide a new kind of luminescent materials under ultraviolet and near ultraviolet excitation for various applications.

Photoluminescence of Y2O3:Eu3+ prepared by mimicking wood tissue

Cubic Y2O3:Eu3+ was successfully prepared by mimicking wood tissue of Nepal Alder. Its structure was characterized by X-ray diffraction pattern (XRD) and Energy dispersive X-ray spectroscopy (EDX). The results show that the sample shares the single phase of cubic structure. The composition analysis shows an approximate Y3+ to Eu3+ atom ratio of about 10:1. The scanning electron microscopy (SEM) images confirm that the sample shares the same shape as the wood tissue of Nepal Alder, which was composed of some thin fibers with an average grain size of about 1μm. The red phosphor exhibits strong red emission of the 5D0→7F2 transition for Eu3+ at 611nm, under 254nm excitation.

Preparation and characterization of boron oxide-based red-emitting phosphors using Eu, Al and Ca additives

New red-emitting phosphors have been produced and studied by investigating the effects of various additives such as europium (Eu), aluminum (Al), and calcium (Ca) on the photoluminescence performance of boron oxide-based phosphors. When both Eu and Ca ions were added, Ca3B2O6:Eu phosphors could be synthesized via a straightforward process using a liquid precursor. The photoluminescent spectra of Ca3B2O6:Eu phosphors exhibited a red emission at 611nm under 254nm excitation, and the internal quantum efficiency reached 41.5% when the concentration of Eu ion was fixed at an optimal condition of 0.13M.

N-Methyl-d-aspartate Receptor Mechanosensitivity Is Governed by C Terminus of NR2B Subunit

N-methyl-D-aspartate receptors (NMDARs), critical mediators of both physiologic and pathologic neurological signaling, have previously been shown to be sensitive to mechanical stretch through the loss of its native Mg(2+) block. However, the regulation of this mechanosensitivity has yet to be further explored. Furthermore, as it has become apparent that NMDAR-mediated signaling is dependent on specific NMDAR subtypes, as governed by the identity of the NR2 subunit, a crucial unanswered question is the role of subunit composition in observed NMDAR mechanosensitivity. Here, we used a recombinant system to assess the mechanosensitivity of specific subtypes and demonstrate that the mechanosensitive property is uniquely governed by the NR2B subunit. NR1/NR2B NMDARs displayed significant stretch sensitivity, whereas NR1/NR2A NMDARs did not respond to stretch. Furthermore, NR2B mechanosensitivity was regulated by PKC activity, because PKC inhibition reduced stretch responses in transfected HEK 293 cells and primary cortical neurons. Finally, using NR2B point mutations, we identified a PKC phosphorylation site, Ser-1323 on NR2B, as a unique critical regulator of stretch sensitivity. These data suggest that the selective mechanosensitivity of NR2B can significantly impact neuronal response to traumatic brain injury and illustrate that the mechanical tone of the neuron can be dynamically regulated by PKC activity.

The Endoplasmic Reticulum of Dorsal Root Ganglion Neurons Contains Functional TRPV1 Channels

Transient receptor potential vanilloid type 1 (TRPV1) is a plasma membrane Ca(2+) channel involved in transduction of painful stimuli. Dorsal root ganglion (DRG) neurons express ectopic but functional TRPV1 channels in the endoplasmic reticulum (ER) (TRPV1(ER)). We have studied the properties of TRPV1(ER) in DRG neurons and HEK293T cells expressing TRPV1. Activation of TRPV1(ER) with capsaicin or other vanilloids produced an increase of cytosolic Ca(2+) due to Ca(2+) release from the ER. The decrease of [Ca(2+)](ER) was directly revealed by an ER-targeted aequorin Ca(2+) probe, expressed in DRG neurons using a herpes amplicon virus. The sensitivity of TRPV1(ER) to capsaicin was smaller than the sensitivity of the plasma membrane TRPV1 channels. The low affinity of TRPV1(ER) was not related to protein kinase A- or C-mediated phosphorylations, but it was due to inactivation by cytosolic Ca(2+) because the sensitivity to capsaicin was increased by loading the cells with the Ca(2+) chelator BAPTA. Decreasing [Ca(2+)](ER) did not affect the sensitivity of TRPV1(ER) to capsaicin. Disruption of the TRPV1 calmodulin-binding domains at either the C terminus (Delta35AA) or the N terminus (K155A) increased 10-fold the affinity of TRPV1(ER) for capsaicin, suggesting that calmodulin is involved in the inactivation. The lack of TRPV1 sensitizers, such as phosphatidylinositol 4,5-bisphosphate, in the ER could contribute to decrease the affinity for capsaicin. The low sensitivity of TRPV1(ER) to agonists may be critical for neuron health, because otherwise Ca(2+) depletion of ER could lead to ER stress, unfolding protein response, and cell death.

The Cytoplasmic Peptidase DPP9 Is Rate-limiting for Degradation of Proline-containing Peptides

Protein degradation is an essential process that continuously takes place in all living cells. Regulated degradation of most cellular proteins is initiated by proteasomes, which produce peptides of varying length. These peptides are rapidly cleaved to single amino acids by cytoplasmic peptidases. Proline-containing peptides pose a specific problem due to structural constrains imposed by the pyrrolidine ring that prevents most peptidases from cleavage. Here we show that DPP9, a poorly characterized cytoplasmic prolyl-peptidase, is rate-limiting for destruction of proline-containing substrates both in cell extracts and in intact cells. We identified the first natural substrate for DPP9, the RU1(34-42) antigenic peptide (VPYGSFKHV). RU1(34-42) is degraded in vitro by DPP9, and down-regulation of DPP9 in intact cells results in increased presentation of this antigen. Together our findings demonstrate an important role for DPP9 in peptide turnover and antigen presentation.

Regulation of the Proteasome by Neuronal Activity and Calcium/Calmodulin-dependent Protein Kinase II

Protein degradation via the ubiquitin proteasome system has been shown to regulate changes in synaptic strength that underlie multiple forms of synaptic plasticity. It is plausible, therefore, that the ubiquitin proteasome system is itself regulated by synaptic activity. By utilizing live-cell imaging strategies we report the rapid and dynamic regulation of the proteasome in hippocampal neurons by synaptic activity. We find that the blockade of action potentials (APs) with tetrodotoxin inhibited the activity of the proteasome, whereas the up-regulation of APs with bicuculline dramatically increased the activity of the proteasome. In addition, the regulation of the proteasome is dependent upon external calcium entry in part through N-methyl-D-aspartate receptors and L-type voltage-gated calcium channels and requires the activity of calcium/calmodulin-dependent protein kinase II (CaMKII). Using in vitro and in vivo assays we find that CaMKII stimulates proteasome activity and directly phosphorylates Rpt6, a subunit of the 19 S (PA700) subcomplex of the 26 S proteasome. Our data provide a novel mechanism whereby CaMKII may regulate the proteasome in neurons to facilitate remodeling of synaptic connections through protein degradation.

Native Store-operated Ca2+ Influx Requires the Channel Function of Orai1 and TRPC1

With the discovery of STIM1 and Orai1 and gating of both TRPC and Orai1 channels by STIM1, a central question is the role of each of the channels in the native store-operated Ca(2+) influx (SOCs). Here, we used a strategy of knockdown of Orai1 and of TRPC1 alone and in combination and rescue by small interfering RNA-protected mutants (sm) of smOrai1 and smTRPC1 to demonstrate that in human embryonic kidney (HEK) cells, rescue of SOCs required co-transfection of low levels of both smOrai1 and smTRPC1. The pore mutant Orai1(E106Q) failed to rescue the SOCs in the presence or absence of TRPC1 and, surprisingly, the pore mutant TRPC1(F562A) failed to rescue the SOCs in the presence or absence of Orai1. TRPC1 is gated by electrostatic interaction between TRPC1(D639D,D640D) with STIM1(K684K, K685K). Strikingly, the channel-dead TRPC1(D639K,D640K) that can be rescued only by the STIM1(K684E,K685E) mutant could restore SOCs only when expressed with Orai1 and STIM1(K684E,K685E). Accordingly, we found a mutual requirement of Orai1 and TRPC1 for their interaction with the native STIM1 in HEK cells. By contrast, SOC and the CRAC current in Jurkat cells were inhibited by knockdown of Orai1 but were not influenced by knockdown on TRPC1 or TRPC3. These findings define the molecular makeup of the native SOCs in HEK cells and the role of a STIM1-Orai1-TRPC1 complex in SOC activity.

La 3PO 7:Eu 3+ nanoparticles — A novel red phosphor

Eu 3+-doped oxyphosphate (La 3PO 7:Eu 3+) nanoparticles were synthesized by a straightforward combustion method. Under 254-nm excitation, the La 3PO 7:Eu 3+ nanoparticles emitted intense red fluorescence from the 5D 0→ 7F 2 transition of Eu 3+ ions. When the ratio of glycine to nitrate was about 2.7:1, the optimal intensity of the 5D 0→ 7F 2 transition was obtained. The luminescence intensity of La 3PO 7:Eu 3+ stronger than YBO 3:Eu 3+ and the Commission Internationale de l' Eclairage chromaticity coordinates of La 3PO 7:Eu 3+ nanoparticles are in the red area of CIE1931 XY chromaticity coordinate graph. It is close to that of Y 2O 3:Eu 3+ and has a better colour purity than YBO 3:Eu 3+. As a novel red phosphor, this nanomaterial is low cost and may have potential applications in plasma display panels and Hg-free fluorescent lamps in the future.

Intracellular calcium mobilization of the aganglionic intestine in the endothelin B receptor gene –deficient rat

Background and Aim Up to now, numerous reports have analyzed the pathogenesis of Hirschsprung's disease (HD) by means of physiologic, pathologic, or molecular biologic methods. However, very little is still known about the smooth muscle cell itself. The endothelin B receptor gene–deficient (EDNRB(−/−)) rat, which is suitable for research of HD, has an aganglionic segment of the total colon. Our purpose is to investigate the myogenic mechanisms using simultaneous measurements of the intracellular Ca 2+ concentration ([Ca 2+]i) and tension and reverse transcriptase polymerase chain reaction for L-type Ca 2+ channel (L-VOC) expression. Methods The muscle strips of the rat distal colon were loaded with a Ca 2+ indicator dye, fura-PE3/AM, for 3 to 4 hours. The changes in the fluorescence intensity of Ca 2+-fura-PE3 complex of the strips were monitored with a front surface fluorometer (CAM-230). The fluorescence intensities at 340- and 380-nm excitation and their ratio (F340/F380) were recorded as the level of [Ca 2+]i. The comparison of L-VOC α1c subunit messenger RNA (mRNA) expression in both wild and homozygous rat was performed by reverse transcriptase polymerase chain reaction. Results The peak levels of force development induced by carbachol were 139.1% ± 5.0% in EDNRB(−/−) rat, whereas the peak levels were 242.1% ± 27.7% in EDNRB(+/+) rat. The changes in the [Ca 2+]i elevation induced by carbachol were 101.7% ± 12.2% in the homozygous rat, whereas these were 143.8% ± 8.9% in the wild-type rat. Both results in the homozygous rat significantly decreased in comparison with those of the wild rat ( P < .05). The expression of the L-VOC channel mRNA also decreased in the homozygous rat. Conclusions This is the first report to show the [Ca 2+]i mobilization in the smooth muscles of the rat model of HD. The decrease in both [Ca 2+]i and force development was thus considered to be due to the decrease in the Ca 2+ channel expression.

Human serum albumin binding assay based on displacement of a non selective fluorescent inhibitor

In this paper, we describe a fluorescent antibacterial analog, 6, with utility as a competition probe to determine affinities of other antibacterial analogs for human serum albumin (HSA). Analog 6 bound to HSA with an affinity of 400±100nM and the fluorescence was environmentally sensitive. With 370nm excitation, environmental sensitivity was indicated by a quenching of the 530nm emission when the probe bound to HSA. Displacement of dansylsarcosine from HSA by 6 indicated it competed with compounds that bound at site II (ibuprofen binding site) on HSA. Analog 6 also shifted the NMR peaks of an HSA bound oleic acid molecule that itself was affected by compounds that bound at site II. In addition to binding at site II, 6 interacted at site I (warfarin binding site) as indicated by displacement of dansylamide and the shifting of NMR peaks of an HSA bound oleic acid molecule affected by warfarin site binding. Additional evidence for multiple site interaction was discovered when a percentage of 6 could be displaced by either ibuprofen or phenylbutazone. A competition assay was established using 6 to determine relative affinities of other antibacterial inhibitors for HSA.

Luminescent Properties of Sr&lt;sub&gt;2&lt;/sub&gt;B&lt;sub&gt;5&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt;Cl Phosphor Doped with Eu

Sr2B5O9Cl:Eu phosphor with high efficient luminescent material was synthesized by solid-state reaction method in air. The result of X-ray diffraction showed that the pure Sr2B5O9Cl phase forms at 900°C. The emission spectrum of Sr2B5O9Cl:Eu under 254nm excitation contained two parts. One part was constituted by a strong peak located at 417nm due to the d→f transition of Eu2+ ion, and the other part contained five weak peaks between 580-660nm due to the 5D0→7FJ(J=1,2,3) of Eu3+ ion. The infrared spectrum revealed that both BO3 unites and BO4 unites coexisted in the resultant product. The Eu2+ was surrounded and protected from being oxidized by the BO4 unites. Both red and blue visible lights were observed under ultraviolet excitation as a result of the coexistence of Eu2+ ion and Eu3+ ion.

TRPM7 Regulates Cell Adhesion by Controlling the Calcium-dependent Protease Calpain

m-Calpain is a protease implicated in the control of cell adhesion through focal adhesion disassembly. The mechanism by which the enzyme is spatially and temporally controlled is not well understood, particularly because the dependence of calpain on calcium exceeds the submicromolar concentrations normally observed in cells. Here we show that the channel kinase TRPM7 localizes to peripheral adhesion complexes with m-calpain, where it regulates cell adhesion by controlling the activity of the protease. Our research revealed that overexpression of TRPM7 in cells caused cell rounding with a concomitant loss of cell adhesion that is dependent upon the channel of the protein but not its kinase activities. Knockdown of m-calpain blocked TRPM7-induced cell rounding and cell detachment. Silencing of TRPM7 by RNA interference, however, strengthened cell adhesion and increased the number of peripheral adhesion complexes in the cells. Together, our results suggest that the ion channel TRPM7 regulates cell adhesion through m-calpain by mediating the local influx of calcium into peripheral adhesion complexes.

Luminescence properties of newly developed red-emitting phosphors M2Si2O7:Eu3+ (M=La, Y) under UV/VUV excitation

AbstractThe red-emitting phosphors of Eu3+ doped M2Si2O7 (M=La, Y) were synthesized by a solid-state reaction method and their luminescence properties in UV-VUV region have been studied. On the excitation spectra, the Eu3+-O2- CT band is of higher intensity for La2Si2O7, while for Y2Si2O7, the absorption around 150nm is much stronger and this can be assigned to the Y3+-O2- CT band in company with the Si-O group absorption. The emission spectra show higher intensity and better color purity for La2Si2O7:Eu3+ under 254nm excitation due to Eu3+ occupying the non-centrosymmetric site. Under 147nm excitation, Y2Si2O7:Eu3+ exhibits stronger emission with purer red, which can be corresponded to the absorption of Y3+-O2- CT in the VUV region.

Impaired Ca2+ Store Functions in Skeletal and Cardiac Muscle Cells from Sarcalumenin-deficient Mice

Sarcalumenin (SAR), specifically expressed in striated muscle cells, is a Ca2+-binding protein localized in the sarcoplasmic reticulum (SR) of the intracellular Ca2+ store. By generating SAR-deficient mice, we herein examined its physiological role. The mutant mice were apparently normal in growth, health, and reproduction, indicating that SAR is not essential for fundamental muscle functions. SAR-deficient skeletal muscle carrying irregular SR ultrastructures retained normal force generation but showed slow relaxation phases after contractions. A weakened Ca2+ uptake activity was detected in the SR prepared from mutant muscle, indicating that SAR contributes to Ca2+ buffering in the SR lumen and also to the maintenance of Ca2+ pump proteins. Cardiac myocytes from SAR-deficient mice showed slow contraction and relaxation accompanied by impaired Ca2+ transients, and the mutant mice exhibited a number of impairments in cardiac performance as determined in electrocardiography, ventricular catheterization, and echocardiography. The results obtained demonstrate that SAR plays important roles in improving the Ca2+ handling functions of the SR in striated muscle.

Angiotensin II and Epidermal Growth Factor Induce Cyclooxygenase-2 Expression in Intestinal Epithelial Cells through Small GTPases Using Distinct Signaling Pathways

Colorectal carcinogenesis is a multistep process involving genetic mutations and alterations in rigorously controlled signaling pathways and gene expression that control intestinal epithelial cell proliferation, differentiation, and apoptosis. Cyclooxygenase-2 (COX-2) is aberrantly expressed in premalignant adenomatous polyps and colorectal carcinomas and is associated with increased epithelial cell proliferation, decreased apoptosis, and increased cell invasiveness. Currently, knowledge of the regulation of expression of COX-2 by endogenous cell-surface receptors is inadequate. Recently, in a non-transformed rat intestinal epithelial cell line (IEC-18), we showed induction of cell proliferation and DNA synthesis by angiotensin II (Ang II) via the endogenous Ang II type 1 receptor (Chiu, T., Santiskulvong, C., and Rozengurt, E. (2003) Am. J. Physiol. 285, G1-G11). We report that Ang II potently stimulated expression of COX-2 mRNA and protein as an immediate-early gene response through the Ang II type 1 receptor, correlating with an increase in prostaglandin I2 production. Ang II induced Cdc42 activation and filopodial formation. COX-2 expression was induced by epidermal growth factor (EGF), which activated Rac with lamellipodial formation. Inhibition of small GTPases by Clostridium difficile toxin B blocked COX-2 expression by Ang II and EGF. Inhibition of ERK activation by U0126 or PD98059 significantly decreased EGF-dependent COX-2 expression, but did not affect Ang II-dependent COX-2 expression. Conversely, inhibition of p38MAPK by SB202190 or PD169316 inhibited COX-2 expression by Ang II, but did not block COX-2 induction by EGF. Ang II caused Ca2+ mobilization. Inhibition of Ca2+ signaling by 2-aminobiphenyl borate blocked Ang II-dependent COX-2 expression. EGF did not induce Ca2+ mobilization, and 2-aminobiphenyl borate did not inhibit EGF-dependent COX-2 expression. Inhibition of COX-2 expression correlated with inhibition of prostaglandin I2 production. Luciferase promoter assays showed that Ang II-dependent transcriptional activation of the COX-2 promoter was dependent on activation of small GTPases and p38(MAPK) and on Ca2+ signaling via the cAMP-responsive element/activating transcription factor cis-acting element.

Nanoparticles of a doped oxide phosphor prepared by direct-spray pyrolysis

A gas-phase synthesis route based on spray pyrolysis with a residence/heating time of less than 0.1 s was designed to directly prepare Eu-doped Y2O3 phosphor nanoparticles. The average size of the phosphor particles decreased from the submicron size to around 10 nm when the concentration of the starting solution was increased. By increasing the operating temperature, from 1500 to 1700 °C, the submicron-particles were converted into a nano-particle phosphor, and their photoluminescence intensities at 611 nm (254-nm excitation) were greatly improved. This synthesis procedure has considerable potential for preparing a variety of doped luminescent nanoparticles without the need for post-treatment processing.

Luminescence of Ba 0.85 MgAl 10 O 16.94 :Eu 2+ 0.09 with different fluxes

BaMgAl10O17:Eu2+, known as BAM, is a very important blue-emitting phosphor used in plasma display panels (PDP) and three band fluorescent lamps. In this paper, the Ba0.85MgAl10O16.94:Eu2+0.09 phosphors with different fluxes (BaF2, MgF2, AlF3, BaCl2, MgCl2, AlCl3, H3BO3) were prepared by high temperature solid-state reaction method and the influence of different fluxes on the luminescence of Ba0.85MgAl10O16.94:Eu2+0.09 phosphor was studied under 254nm excitation and vacuum ultraviolet (VUV) excitation. It was found that fluorides have better flux effects than chlorides and H3BO3. The mechanism of particle growth in the presence of flux in the process of phosphor preparation is discussed in detail. Particle size distribution and the crystal structure of the phosphors are also analysed.