ALBERT

Description: Matrix-assisted laser desorption ionization (MALDI) has been widely used in the mass analysis of biomolecules; however, there are a lot of debates about the ionization mechanisms. Previous studies have indicated that S 1 -S 1 annihilation might be a key process in the generation of primary ions. This study investigates S 1 -S 1 annihilation by examining the time-resolved fluorescence spectra of 12 matrices. No S 1 -S 1 annihilation was observed in six of these matrices (3-hydroxy-picolinic acid, 6-aza-2-thiothymine, 2,4-dihydroxy-acetophenone, 2,6-dihydroxy-acetophenone, 2,4,6-trihydroxy-acetophenone, and ferulic acid). We observed two matrix molecules reacting in an electronically excited state (S 1 ) in five of these matrices (2,5-dihydroxybenzoic acid, α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxy-acetophenone, 2,3-dihydroxybenzoic acid, and 2,6-dihydroxybenzoic acid), and S 1 -S 1 annihilation was a possible reaction. Among these five matrices, no S 1 -S 1 annihilation was observed for 2,3-dihydroxybenzoic acid in typical peak power region of nanosecond laser pulses in MALDI, but a very small value of reaction rate constant was observed only in the high peak power region. The excited-state lifetime of sinapinic acid was too short to determine whether the molecules reacted in an electronically excited state. No correlation was observed between the ion generation efficiency of MALDI and S 1 -S 1 annihilation. The results indicate that the proposal of S 1 -S 1 annihilation is unnecessary in MALDI and energy pooling model for MALDI ionization mechanism has to be modified.

Description: Matrix-assisted laser desorption ionization (MALDI) has been widely used in the mass analysis of biomolecules; however, there are a lot of debates about the ionization mechanisms. Previous studies have indicated that S 1 -S 1 annihilation might be a key process in the generation of primary ions. This study investigates S 1 -S 1 annihilation by examining the time-resolved fluorescence spectra of 12 matrices. No S 1 -S 1 annihilation was observed in six of these matrices (3-hydroxy-picolinic acid, 6-aza-2-thiothymine, 2,4-dihydroxy-acetophenone, 2,6-dihydroxy-acetophenone, 2,4,6-trihydroxy-acetophenone, and ferulic acid). We observed two matrix molecules reacting in an electronically excited state (S 1 ) in five of these matrices (2,5-dihydroxybenzoic acid, α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxy-acetophenone, 2,3-dihydroxybenzoic acid, and 2,6-dihydroxybenzoic acid), and S 1 -S 1 annihilation was a possible reaction. Among these five matrices, no S 1 -S 1 annihilation was observed for 2,3-dihydroxybenzoic acid in typical peak power region of nanosecond laser pulses in MALDI, but a very small value of reaction rate constant was observed only in the high peak power region. The excited-state lifetime of sinapinic acid was too short to determine whether the molecules reacted in an electronically excited state. No correlation was observed between the ion generation efficiency of MALDI and S 1 -S 1 annihilation. The results indicate that the proposal of S 1 -S 1 annihilation is unnecessary in MALDI and energy pooling model for MALDI ionization mechanism has to be modified.

Description: Journal of Proteome Research DOI: 10.1021/acs.jproteome.6b00138

Description: Chemokine (C-C motif) ligand 3 (CCL3), also known as macrophage inflammatory protein-1alpha, is a cytokine involved in inflammation and activation of polymorphonuclear leukocytes. CCL3 has been detected in infiltrating cells and tumor cells. Chondrosarcoma is a highly malignant tumor that causes distant metastasis. However, the effect of CCL3 on human chondrosarcoma metastasis is still unknown. Here, we found that CCL3 increased cellular migration and expression of matrix metalloproteinase (MMP)-2 in human chondrosarcoma cells. Pre-treatment of cells with the MMP-2 inhibitor or transfection with MMP-2 specific siRNA abolished CCL3-induced cell migration. CCL3 has been reported to exert its effects through activation of its specific receptor, CC chemokine receptor 5 (CCR5). The CCR5 and AMP-activated protein kinase (AMPK) inhibitor or siRNA also attenuated CCL3-upregulated cell motility and MMP-2 expression. CCL3-induced expression of MMP-2 and migration were also inhibited by specific inhibitors, and inactive mutants of AMPK, p38 mitogen activated protein kinase (p38 or p38-MAPK), and nuclear factor kappaB (NF-kappaB) cascades. On the other hand, CCL3 treatment demonstrably activated AMPK, p38, and NF-kappaB signaling pathways. Furthermore, the expression levels of CCL3, CCR5, and MMP-2 were correlated in human chondrosarcoma specimens. Taken together, our results indicate that CCL3 enhances the migratory ability of human chondrosarcoma cells by increasing MMP-2 expression via the CCR5, AMPK, p38, and NF-kappaB pathways.

Description: We present a numerical study on phononic band gaps and resonances occurring at the edge of a semi-infinite two-dimensional (2D) phononic crystal plate. The edge supports localized edge waves coupling to evanescent phononic plate modes that decay exponentially into the semi-infinite phononic crystal plate. The band-gap range and the number of edge-wave eigenmodes can be tailored by tuning the distance between the edge and the semi-infinite 2D phononic lattice. As a result, a phononic band gap for simultaneous edge waves and plate waves is created, and phononic cavities beside the edge can be built to support high-frequency edge resonances. We design an L3 edge cavity and analyze its resonance characteristics. Based on the band gap, high quality factor and strong confinement of resonant edge modes are achieved. The results enable enhanced control over acoustic energy flow in phononic crystal plates, which can be used in designing micro and nanoscale resonant devices and coupling of edge resonances to other types of phononic or photonic crystal cavities.

Description: Using light-emitting diodes (LEDs) for visible light communication has become an alternative choice of radio source due to channel crowding of the radio-frequency (RF) signal. The modulation bandwidth of LEDs is usually limited by the spontaneous carrier lifetime in multiple quantum wells. Here, sub-GHz modulation of GaN-based LED employing photonic crystal (PhC) nanostructure is demonstrated. The guided photonic modes of the LEDs are modulated by the RF signal. Both carrier lifetime of lower- and higher-order modes are studied in time-resolved photoluminescence (TRPL) at room temperature. The f - 3 dB - J curve of the PhC LED exhibits a higher bandwidth than the typical LED structure. At 11.41 kA/cm 2 , the optical −3-dB bandwidth ( f - 3 dB ) up to 234 MHz of the PhC LED (PhCLED) is achieved. Our studies on TRPL at different wavelengths and frequency response at different injection current densities conclude that the higher operation speed is attributed to faster radiative carrier recombination of extracted guided modes from the PhC nanostructure.

Description: Background: Protein phosphorylation regulated by plant hormone is involved in the coordination of fundamental plant development. Brassinosteroids (BRs), a group of phytohormones, regulated phosphorylation dynamics remains to be delineated in plants. In this study, we performed a mass spectrometry (MS)-based phosphoproteomics to conduct a global and dynamic phosphoproteome profiling across five time points of BR treatment in the period between 5 min and 12 h. MS coupling with phosphopeptide enrichment techniques has become the powerful tool for profiling protein phosphorylation. However, MS-based methods tend to have data consistency and coverage issues. To address these issues, bioinformatics approaches were used to complement the non-detected proteins and recover the dynamics of phosphorylation events. Results: A total of 1104 unique phosphorylated peptides from 739 unique phosphoproteins were identified. The time-dependent gene ontology (GO) analysis shows the transition of biological processes from signaling transduction to morphogenesis and stress response. The protein-protein interaction analysis found that most of identified phosphoproteins have strongly connections with known BR signaling components. The analysis by using Motif-X was performed to identify 15 enriched motifs, 11 of which correspond to 6 known kinase families. To uncover the dynamic activities of kinases, the enriched motifs were combined with phosphorylation profiles and revealed that the substrates of casein kinase 2 and mitogen-activated protein kinase were significantly phosphorylated and dephosphorylated at initial time of BR treatment, respectively. The time-dependent kinase-substrate interaction networks were constructed and showed many substrates are the downstream of other signals, such as auxin and ABA signaling. While comparing BR responsive phosphoproteome and gene expression data, we found most of phosphorylation changes were not led by gene expression changes. Our results suggested many downstream proteins of BR signaling are induced by phosphorylation via various kinases, not through transcriptional regulation. Conclusions: Through a large-scale dynamic profile of phosphoproteome coupled with bioinformatics, a complicated kinase-centered network related to BR-regulated growth was deciphered. The phosphoproteins and phosphosites identified in our study provide a useful dataset for revealing signaling networks of BR regulation, and also expanded our knowledge of protein phosphorylation modification in plants as well as further deal to solve the plant growth problems.