Yi-Ru Lee

Photodissociation of CH2BrCl at 248 and 193 nm investigated by translational spectroscopy

Abstract The photodissociation of CH 2 BrCl at 248 and 193 nm has been studied by translational spectroscopy. Both the product translational energy distribution and the anisotropy parameter were derived from the measured time-of-flight spectra. Results show that at 248 nm, CH 2 BrCl exclusively dissociates to CH 2 Cl+Br with average translational energy of 20 kcal/mol. On absorption of 193 nm photons, two different paths, (1) CH 2 BrCl→CH 2 Cl+Br and (2) CH 2 BrCl→CH 2 Br+Cl, were detected with average translational energies of 32 and 24 kcal/mol, respectively. The branching ratio of reactions (1)/(2) was deduced as −4.5. From the measured values of product anisotropy parameter at these two wavelengths, we conclude that reaction (1) occurs rapidly after excitation via an A′←A′ transition.

A novel papaya ACC oxidase gene (CP-ACO2) associated with late stage fruit ripening and leaf senescence

Abstract A novel 1-aminocyclopropane-1-carboxylate (ACC) oxidase cDNA clone (CP-ACO2, 1485 bp) was isolated from papaya for the first time. The deduced amino acid sequence shares 77% identity with the previously reported papaya CP-ACO1. Genomic Southern analysis with gene specific probes showed that CP-ACO2 is single copy in papaya genome. It was also identified to be ethylene and wounding inducible, an observation in agreement with the presence of ERE and WUN cis-acting elements in CP-ACO2 promoter region. Northern blot analysis revealed that CP-ACO2 was induced only at the late stage of fruit ripening and leaf senescence, while CP-ACO1 was induced before color break (mature) stage. These results suggest that CP-ACO2 is late stage associated, occurring during organ senescence, such as fruit ripening and leaf senescence; while AP-ACO1is maturation associated are possible. Therefore, two distinct pathways for ACC oxidase regulated ripening, one is regular ripening associated, the other is late stage ripening associated.

Photodissociation of CBrCl3 at 248 nm by translational spectroscopy

Abstract The photodissociation of S 2 Cl 2 at 308 nm has been studied by the crossed laser-molecular beam technique. Both the product translational energy distribution and the antisotropy parameter β were derived from the measured time-of-flight spectra. Results show that S 2 Cl 2 undergoes a simple SCl bond scission with the fragments recoiling anisotropically. The averaged translational energy of the products is 88 kJ/mol. S 2 Cl may produce two pairs of fragments, S 2 +Cl and SCl+S, by absorbing an additional photon. These secondary dissociation processes were observed at high laser powers.

Atomic structure of the Ag/Ge(111)-(3×3) surface: From scanning tunneling microscopy observation to theoretical study

The atomic structure of the Ag/Ge(111)-(sq.rt.(3) x sq.rt.(3))R30 degrees surface is studied by scanning tunneling microscopy (STM) and the density functional theory (DFT) calculations. Our STM images have shown a structure which is different from the widely accepted honeycomb-chained-triangle (HCT) model before. The structure is similar to the inequivalent triangle (IET) model found for the Ag/Si(111)-(sq.rt.(3) x sq.rt(3))R30 degrees surface. This model proposed two types of silver triangles with different sizes in the unit cell, corresponding to the bright spots and the dark spots in the STM image. A distinguishable hexagonal pattern of the IET structure was well disclosed in the temperature range from 100 to 473 K in our STM studies for Ag/Ge(111)-(sq.rt.(3) x sq.rt.(3))R30 degrees. Furthermore, the result of the DFT calculations showed that the IET structure is 0.20 eV energetically more stable than the HCT model. Besides, the Ge triangles, which were not disclosed in earlier STM research, are found in this study.

MicroRNA-like small RNAs prediction in the development of Antrodia cinnamomea.

Antrodia cinnamomea, a precious, host-specific brown-rot fungus that has been used as a folk medicine in Taiwan for centuries is known to have diverse bioactive compounds with potent pharmaceutical activity. In this study, different fermentation states of A. cinnamomea (wild-type fruiting bodies and liquid cultured mycelium) were sequenced using the next-generation sequencing (NGS) technique. A 45.58 Mb genome encoding 6,522 predicted genes was obtained. High quality reads were assembled into a total of 13,109 unigenes. Using a previously constructed pipeline to search for microRNAs (miRNAs), we then identified 4 predicted conserved miRNA and 63 novel predicted miRNA-like small RNA (milRNA) candidates. Target prediction revealed several interesting proteins involved in tri-terpenoid synthesis, mating type recognition, chemical or physical sensory protein and transporters predicted to be regulated by the miRNAs and milRNAs.

Isolation and analysis of genes specifically expressed during basidiomatal development in Antrodia cinnamomea by subtractive PCR and cDNA microarray

cDNAs specifically expressed at the basidiome stage were isolated by using PCR-selected cDNA subtraction in order to study gene regulation during porous-hymenium basidiomatal formation in Antrodia cinnamomea. blastx results suggested that most of the expressed sequence tags (52.4-69.5%) had no significant protein homology to genes from other published living things. cDNAs particularly expressed at different growing conditions were identified using cDNA microarray analysis. Reverse transcriptase PCR analyses confirmed that the clone putative to P-type ATPase, various cytochrome P450s and some unknown genes were abundant at natural basidiomes while endoglucanase was abundant at the tissue from artificial medium.

The 193 nm photodissociation of CH2=CClF

The photodissociation of CH2=CClF at 193 nm has been studied by product translational spectroscopy. A total of five primary dissociation channels was detected for the products of Cl (fast), HCl, HF, Cl (slow), and F in the decreasing order of relative yield. Product translational energy distributions have been measured for these reaction products. While a thermal-like distribution was detected for the slow Cl and F atoms, a nonthermal distribution was determined for the fast Cl atom and the molecular elimination of HCl and HF. Apart from the fast Cl atom with anisotropy parameter β=0.5, the remaining products recoil isotropically following photolysis with linearly polarized light. By analogy with the photodissociation of chloroethylenes, these products are found to originate from two potential energy surfaces. In addition to the primary dissociation channels, we have detected the secondary products of F+C2H2 from the internally excited α-fluorovinyl radical through a fast fragment isomerization.

Characterization of the 2,3-Oxidosqualene Cyclase Gene from Antrodia cinnamomea and Enhancement of Cytotoxic Triterpenoid Compound Production

Antrodia cinnamomea is a scarce, epiphyte, host-specific, brown-rot fungus that produces diverse bioactive compounds with potent biological activity. Natural wild-type fruiting bodies of A. cinnamomea are rare and highly valued, but their artificial culture poses challenges. Triterpenoids are a group of secondary metabolites that contribute to the bioactivities of A. cinnamomea. 2,3-Oxidosqualene cyclase (OSC) is a key enzyme in triterpenoid biosynthesis, which converts 2,3-oxidosqualene (OS) into polycyclic triterpenoids. In this study, we isolated a 2,3-oxidosqualene cyclase gene from A. cinnamomea with degenerate primers and designated it as AcOSC. The full length AcOSC cDNA was subcloned into a yeast expression vector, and AcOSC activity was confirmed. RT-PCR results showed that AcOSC expression was highest in the wild-type fruiting body and correlated with a higher concentration of triterpenoids. Agrobacterium-mediated gene transformation was conducted to enhance the triterpenoid synthesis capacity of the cultured mycelium. Metabolite profiling was conducted by LC-MS/MS and principal component analysis (PCA). The compositions and contents of metabolites in the AcOSC transgenic lines were different from those in the wild-type mycelium and vector control. The levels of two important triterpenoids, dehydrosulphurenic acid (DSA) and dehydroeburicoic acid (DEA), were increased in A. cinnamomea oxidosqualene cyclase overexpression strains compared to controls. In summary an Agrobacterium-mediated gene transformation procedure was established that successfully increased the level of transgene expression and enhanced the triterpenoid content in cultured A. cinnamomea.

Differential Gene Expression Network in Terpenoid Synthesis of Antrodia cinnamomea in Mycelia and Fruiting Bodies

Antodia cinnamomea, a precious brown-rot fungus endemic to Taiwan, has pharmaceutical applications due to its diverse array of metabolites. The terpenoids found in A. cinnamomea contribute to its most important bioactivities. We identified several terpenoid compounds in A. cinnamomea and revealed that their content in mycelium and fruiting body were significantly different. Using next-generation sequencing and an in-house transcriptome database, we identified several terpene synthase (TPS) candidates. After sequence analysis and functional characterization, 10 out of 12 candidates were found to have single or multiple terpene synthesis functions. Most of the terpenoid compounds were found to confer important bioactivities. RT-PCR results showed a positive correlation between terpene synthase expression pattern and terpenoid content. In addition, we identified several modification enzyme candidates that may be involved in the postmodification of terpenoid compounds with a genomic DNA scaffold, and a putative genetic network.

Characterization of S-(+)-linalool synthase from several provenances of Cinnamomum osmophloeum

Cinnamomum osmophloeum is a commercially important tree species in Taiwan, which has numerous chemotypes with various secondary metabolite profiles. The linalool chemotype is important because it generates pure S-(+)-linalool with high yield. In the present study, the linalool synthase (LIS) genes were isolated from different provenances of C. osmophloeum. The recombinant proteins of LIS were able to generate the S-(+)-linalool from GPP and (E)-nerolidol from FPP. Kinetic analysis showed differing enzyme activities of similar proteins from different provenances. Two point mutations enhanced enzyme activity up to sixfold. Phylogenetic analysis and leaf volatiles composition analysis clustered the genes into designated groups according to their chemotypes. Because the CoLIS-LL gene has a particularly abundant transcript, we suggest that the W-box, recognized by the WRKY transcription factor, might be responsible for high differential gene expression. A marker based on the W-box sequence can be used to distinguish linalool chemotype.