Yi-Hung Lin

Structure of Bacillus amyloliquefaciens alpha-amylase at high resolution: implications for thermal stability.

The crystal structure of Bacillus amyloliquefaciens alpha-amylase (BAA) at 1.4 A resolution revealed ambiguities in the thermal adaptation of homologous proteins in this family. The final model of BAA is composed of two molecules in a back-to-back orientation, which is likely to be a consequence of crystal packing. Despite a high degree of identity, comparison of the structure of BAA with those of other liquefying-type alpha-amylases indicated moderate discrepancies at the secondary-structural level. Moreover, a domain-displacement survey using anisotropic B-factor and domain-motion analyses implied a significant contribution of domain B to the total flexibility of BAA, while visual inspection of the structure superimposed with that of B. licheniformis alpha-amylase (BLA) indicated higher flexibility of the latter in the central domain A. Therefore, it is suggested that domain B may play an important role in liquefying alpha-amylases, as its rigidity offers a substantial improvement in thermostability in BLA compared with BAA.

Two-dimensional PPLN for simultaneous laser Q-switching and optical parametric oscillation in a Nd:YVO 4 laser

We report on a tunable intracavity optical parametric oscillator (IOPO) achieved using a two-dimensional (2D) periodically poled lithium niobate (PPLN) as simultaneously an electro-optic (EO) Bragg Q-switch and an optical frequency mixer (OFM) in a diode-pumped Nd:YVO(4) laser. The 2D periodic domain inversion structure is designed to provide two orthogonal reciprocal vectors to respectively satisfy the phase-matching conditions required by the two quasi-phase-matching devices (i.e., the PPLN EO Bragg deflector and the PPLN OFM). At a ~140-V Q-switching voltage and a 1-kHz switching rate, we obtained a signal wave at 1550 nm with a pulse energy of 9.7 μJ (corresponding to a peak power of ~2.4 kW) from the IOPO at 9.1-W diode pump power. Simultaneously we also observed multi-wavelength generation from the system originating in the single-pass parametric conversions in the 2D nonlinear photonic crystal structure. Temperature tuning of the IOPO signal wavelength in the eye-safe region was also demonstrated.

Purification, crystallization and preliminary X-ray crystallographic analysis of rice Bowman-Birk inhibitor from Oryza sativa

Bowman-Birk inhibitors (BBIs) are cysteine-rich proteins with inhibitory activity against proteases that are widely distributed in monocot and dicot species. The expression of rice BBI from Oryza sativa is up-regulated and induced by pathogens or insects during germination of rice seeds. The rice BBI (RBTI) of molecular weight 15 kDa has been crystallized using the hanging-drop vapour-diffusion method. According to the diffraction of rice BBI crystals at a resolution of 2.07 A, the unit cell belongs to space group P2(1)2(1)2(1), with unit-cell parameters a = 74.37, b = 96.69, c = 100.36 A. Preliminary analysis indicates four BBI molecules in an asymmetric unit, with a solvent content of 58.29%.

Purification, crystallization and preliminary X-ray crystallographic analysis of rice lectin from Oryza sativa

Lectins with sugar-binding specificity are widely distributed in higher plants and various other species. The expression of rice lectin from Oryza sativa is up-regulated in the growing coleoptile when anaerobic stress persists. A rice lectin of molecular weight 15.2 kDa has been crystallized using the hanging-drop vapour-diffusion method. From the diffraction of the lectin crystals at 1.93 A resolution, the unit cell belongs to space group P3(1), with unit-cell parameters a = 98.58, b = 98.58, c = 44.72 A. Preliminary analysis indicates that there are two lectin molecules in an asymmetric unit with a large solvent content, 70.1%.

Broadband fiber-laser-pumped CW OPO for red, green, blue laser generation

We report a cw-RGB laser based on an Yb-fiber-laser pumped OPO with intra- and extracavity wavelength converters. At 25-W pump power, the laser generated 5, 0.5, and 0.01-W at 633, 532, and 450 nm, respectively.

Purification, crystallization and preliminary X-ray crystallographic analysis of rice bifunctional α-amylase/subtilisin inhibitor from Oryza sativa

Rice bifunctional alpha-amylase/subtilisin inhibitor (RASI) can inhibit both alpha-amylase from larvae of the red flour beetle (Tribolium castaneum) and subtilisin from Bacillus subtilis. The synthesis of RASI is up-regulated during the late milky stage in developing seeds. The 8.9 kDa molecular-weight RASI from rice has been crystallized using the hanging-drop vapour-diffusion method. According to 1.81 angstroms resolution X-ray diffraction data from rice RASI crystals, the crystal belongs to space group P2(1)2(1)2, with unit-cell parameters a = 79.99, b = 62.95, c = 66.70 angstroms. Preliminary analysis indicates two RASI molecules in an asymmetric unit with a solvent content of 44%.

Purification, crystallization and preliminary X-ray crystallographic analysis of chitinase from Bacillus cereus NCTU2

Chitinases (EC 3.2.1.14) are found in a broad range of organisms, including bacteria, fungi and higher plants, and play different roles depending on their origin. A chitinase from Bacillus cereus NCTU2 (ChiNCTU2) capable of hydrolyzing chitin as a carbon and nitrogen nutrient has been identified as a member of the family 18 glycoside hydrolases. ChiNCTU2 of molecular weight 36 kDa has been crystallized using the hanging-drop vapour-diffusion method. According to the diffraction of chitinase crystals at 1.10 A resolution, the crystal belongs to space group P2(1), with unit-cell parameters a = 50.79, b = 48.79, c = 66.87 A, beta = 99.31 degrees . Preliminary analysis indicates there is one chitinase molecule in the asymmetric unit, with a solvent content of 43.4%.

2D PPLN for simultaneous laser Q-switching and optical parametric oscillation in a Nd:YVO 4 laser

We report a tunable optical parametric oscillator using a 2D PPLN as simultaneously an electro-optic Bragg Q-switch and an optical frequency mixer in a Nd:YVO4 laser. >;2-kW peak-power eye-safe light was obtained with this system.

Backward THz-wave generation from collinearly phase-matched difference-frequency mixing in periodically poled lithium niobate

We demonstrate difference frequency generation of backward THz waves from collinearly phase-matched, periodically poled lithium niobate. Coherent THz waves between 457~507 mum were generated by using kW pump power at a kHz repetition rate.

Macroscopic‐Size Accelerator Structures for CO2 Laser‐Driven Linear Acceleration in a Vacuum

We report the simulation and fabrication of a single‐stage and a multistage CO2 laser‐driven particle accelerator with macroscopic dimensions suitable for conducting proof‐of‐principle laser‐driven acceleration experiments in a vacuum. The single‐stage copper accelerator structure, having a 300‐μm electron transit aperture, is 10 cm long and provides 210 keV electron energy gain. The multistage structure consists of 16 ZnSe lenses with 1.5 cm separation between adjacent lenses. The energy gain over the 24‐cm distance is 250 keV for a 200‐μm electron transit aperture. This resonant structure is suitable for studying beam loading, mode excitation, and phase synchronization among accelerator stages.