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An efficient all-solid-state picosecond (ps) ultraviolet (UV) laser at 335 nm was demonstrated based on frequency quadrupling of a mode-locked 1342 nm MOPA system. An output power of 0.95 W was obtained under a fundamental wave power of 16.38 W, corresponding to a conversion efficiency of 5.8% from infrared to UV. The repetition rate and pulse duration were 77 MHz and 20.2 ps, respectively. The beam quality factor M^2 was measured to be 1.56. This is, to the best of our knowledge, the highest output power at 335 nm.

We have investigated the influence of the oxygen stoichiometry on the structures, dielectric and ferroelectric properties of the BaTiO 3 thin films. The oxygen content in the films has a significant effect on lattice parameters, crystalline phase, crystallographic orientation, dielectric constant, dissipation factor, spontaneous polarization and polarization-electric field curves.

Epidermal Growth Factor (EGF) is a small growth factor containing 53 amino acid residues capable of stimulating the proliferation of both mesenchymal and epithelial cells. Comparison of the amino acid sequences of EGF from several species, and related proteins that can bind to the EGF receptor (e.g. TGFα, VGF, heparin-binding EGF, and betacellulin), suggests that Leu47, which is highly conserved, is important for biological function. Additionally, we have shown previously, using a combination of trypsin and carboxypeptidase Y digestion of native murine EGF, that removal of Leu47 results in more than 100-fold decrease in both receptor binding and mitogenic activity. We now describe a micromethod for the rapid generation of C-terminally modified EGFs to investigate further the role of C-terminal residues in determining functional activity. These analogues have been generated by digesting native murine EGF with trypsin, purifying the biologically inactive, but structurally intact, EGF1-45 core by micropreparative RP-HPLC, and then reversing the action of trypsin to couple synthetic peptides (e.g. DL, DI, DF, EL, DLLW) onto the C-terminus of the EGF1-45 core. This enzymic semisynthesis method allows multiple derivatives to be generated rapidly from microgram quantities of EGF1-45 in sufficient quantities for sensitive biological and physicochemical analysis. We have validated the method by regenerating EGF1-47 from EGF1-45 with equivalent mitogenic and receptor binding activity to EGF1-47 generated from wild type EGF by digestion with trypsin and carboxypeptidase Y. We have also investigated the effect of substituting alternative normal or non-physiological amino acids (e.g. allo-Ile) for Asp46, Leu47 or Arg48. Even small changes in these C-terminal residues reduce the mitogenic potency of the analogue.

Destetrapeptide insulin (DTI, human insulin with B27-30 removed) was obtained from a monomeric precursor (MIP) expressed in Saccharomyces cerevisiae through tryptic transpeptidation in the presence of synthetic tetrapeptide Gly-Phe-Phe-Tyr. The in vivo biological activity of DTI, determined by mouse convulsion assay, is 22 IU/mg. Its binding activity with insulin receptor on human placental membrane is 80% and its in vitro biological activity, determined by free fat cell assay, is 77%. Compared with native insulin, DTI molecules do not associate in solution but exist in the monomeric form, thus leading to its rapid utilization in vivo.

DsbC, a periplasmic disulfide isomerase of Gram-negative bacteria, displays about 30% of the activities of eukaryotic protein disulfide isomerase (PDI) as isomerase and as thiol-protein oxidoreductase. However, DsbC shows more pronounced chaperone activity than does PDI in promoting the in vitro reactivation and suppressing aggregation of denatured D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) during refolding. Carboxymethylation of DsbC at Cys98 decreases its intrinsic fluorescence, deprives of its enzyme activities, but lowers only partly its chaperone activity in assisting GAPDH reactivation. Simultaneous presence of DsbC and PDI in the refolding buffer shows an additive effect on the reactivation of GAPDH. The assisted reactivation of GAPDH and the protein disulfide oxidoreductase activity of DsbC can both be inhibited by scrambled and S-carboxymethylated RNases, but not by shorter peptides, including synthetic 10- and 14-mer peptides and S-carboxymethylated insulin A chain. In contrast, all the three peptides and the two nonnative RNases inhibit PDI-assisted GAPDH reactivation and the reductase activity of PDI. DsbC assists refolding of denatured and reduced lysozyme to a higher level than does PDI in phosphate buffer and does not show anti-chaperone activity in HEPES buffer. Like PDI, DsbC is also a disulfide isomerase with chaperone activity but may recognize different folding intermediates as does PDI.

High quality BaTiO3 thin films have been epitaxially grown on SrTiO3 (100) substrates by pulsed laser deposition (PLD) using a single crystal target. The BaTiO3/YBa2Cu3O7 bilayer staictures have also been grown on LaAlO3(100) substrate by PLD for ferroelectric thin film devices. All the two kinds of thin films were analysed by x-ray diffraction, high resolution transmission electron microscopy and scanning electron microscopy.

The effect of the structure YBa2Cu3O7-x superconducting thin films on microwave surface resistance was investigated. The electon channeling patterns (ECPs) and X-ray experimental results showed that the microwave surface resistanceRs is strongly correlated with the perfection of the thin films. The films were deposited on LaAlO3(100) and YSZ(100) substrates. For thin film withRs of 280µO, the crystallinity of the thin film shown byw-scanning andf-scanning was excellent and the ECPs were very sharp. For thin film with highRs of 98 mO, only bands from the major zone were visible in the ECPs, which suggested poor crystallinity of the film. From this investigation it was shown that the more perfect the thin films, the lower theRs.

The surface morphology and growth mechanism ofc-oriented YBa2Cu3O7 thin films deposited on Y-stabilized zirconia substrate by laser deposition has been investigated with scanning tunneling microscopy. Both screw dislocation and layered island growth processes took place. Surface features such as screw dislocation, steps, subgrain boundaries, holes, and troughs were present, suggesting that they may act as pinning sites for flux lines. A thin layer of nonsuperconducting material with a thickness of a few angstroms is seen on the surface of the film.

We have investigated the superconducting behavior of high-Tc YBa2Cu3O7 (YBCO) thin films containing BaO impure phase produced by pulsed laser deposition. The thin films were characterized by the standard four-probe method, X-ray diffraction (XRD), and scanning electron microscopy (SEM). XRD showed that all these thin films contained BaO impurity, with thec-axis normal to the surface of the substrates. The presence of impurity existed from substrate temperatureTs of 727 to 796°C. When these thin films with BaO impurity were measured under the magnetic fields, it was found that the critical current densityJc increased slightly with increase in magnetic fieldB within the range ofB=500 G, in the case ofB perpendicular to thec-axis of the film.

YBa2Cu3O7 superconducting thin films were deposited onR-plane sapphire substrates with Yttria-stabilized zirconia buffer layer by laser ablation. The structure of the films was characterized by X-ray diffraction. Superconducting transitional temperatures as high as =90 K and critical current densities up to 2.2×106 A/cm2 (77 K) were achieved. The results of Auger depth profile showed that no obvious diffusion occurred between the substrate and the YBa2Cu3O7 thin film.

Superconducting MgB₂ thin films were fabricated on Al₂O₃(0001) and MgO(100) substrates by a two-step method. Boron thin films were deposited by pulsed laser deposition followed by an ex-situ annealing process. Resistance measurements of the deposited MgB₂ films show a T_c of 38.6 K for MgB₂/Al₂O₃ and 38.1 K for MgB₂/MgO. Atomic force microscopy, scanning electron microscopy and x-ray diffraction were used to study the properties of the films. The results indicate that the MgB₂/Al₂O₃ films consist of well-crystallized grains with a highly c-axis-oriented structure while the MgB₂/MgO films have a dense uniform appearance with an unfixed orientation.

Des-(B25-B30)-hexapeptide-insulin with B23-glycine replaced by D-alanine was prepared by a combination of enzymic and non-enzymic syntheses. The purified product was homogeneous in polyacrylamide-gel electrophoresis and could be crystallized. The biological activity in vivo of crystalline [B23-D-Ala]des-(B25-B30)-hexapeptide-insulin was determined as 58% of that of standard pig insulin (27 i.u./mg).

We report on the successful preparation of large-area high-quality YBa2Cu3O7 superconducting thin films by pulsed excimer laser ablation with a Si heater and composite scanning of laser beam and target. The Si heater, composite scanning of laser beam and target, and experiment results are described. The temperature variation of the Si heater was < ±0.5% in a 45×40 mm2 area of 900–1000 °C. Films were deposited on LaAlO3 substrates 35 mm in diameter. The thin films exhibited a thickness variation of ±2.5%; the superconducting properties wereTc0=91×0.5 K andJc= (3.3±0.7)×106 A/cm2 at 77 K and zero magnetic field.

The semisynthesis of deshexapeptide insulin (DHI) from desoctapeptide insulin (DOI) reported earlier1showed that DHI was biologically active. However, the product was not quite homogeneous, mainly due to the esterification side reaction and the following saponification2. Recently, the catalytic action of trypsin was successfully used in the preparation of human insulin from porcine insulin3. It was also used in the preparation of insulin analogues with substitutions of B24 or B25 phenylalanine by leucine4,5. Here, we report the synthesis of DHI from DOI and glycylphenylalanine through the catalytic action of trypsin. The product, purified by gel filtration and DEAE-Sephadex ion-exchange chromatography, showed insulin activity of 7.5 IU mg−1in vivoand could be obtained in crystalline form.