Molecular characterization of common carp (Cyprinus carpio) Sonic Hedgehog and discovery of its maternal expression

Sonic hedgehog (Shh), one of important homologous members of the hedgehog (Hh) family in vertebrates, encodes a signaling molecule that is involved in short- or long-range patterning processes during embryogenesis. In zebrafish, maternal activity of Hh was found to be contributing to the formation of primary motoneurons. However, we found that all of the known Hh members were not maternally expressed in zebrafish. In the present study, full-length cDNA of common carp (Cyprinus carpio) Shh (cShh) was gained by degenerate reverse-transcription PCR (RT-PCR) and rapid amplification of cDNA ends. Sequence comparison shows that cShh coding sequence shares 93.4% identity with zebrafish Shh coding sequence, and their corresponding protein sequences have 91.9% similarity. Comparative analysis of Shh genomic sequences and Hh protein sequences from different species revealed that the genomic structures of Hh are conserved from invertebrate to vertebrate. In contrast to zebrafish Shh, cShh transcripts were detectable from one-cell stage by RT-PCR analysis. Whole mount in situ hybridization verified the maternal expression of Shh in common carp, which is, to our knowledge, the first report of that in vertebrates, suggesting that Shh might be responsible for the maternal Hh activity in common carp.

Optical and electrical characterizations of ZnSe self-organized quantum dots grown by molecular beam epitaxy

Optical and electrical properties of ZnSe self-organized quantum dots were investigated using photoluminescence, capacitance-voltage, and deep level transient Fourier spectroscopy techniques. The temperature dependence of photoluminescence was employed to clarify the mechanism of photoluminescence thermal quenching processes in ZnSe quantum dots. A theoretic fit on considering a two-step quenching processes well explained the experimental data. The apparent carrier concentration profile obtained from capacitance-voltage measurements exhibits an accumulation peak at the depth of about 100nm below the sample surface, which is in good agreement with the location of the quantum dot layer. The electronic ground state of ZnSe quantum dots is determined to be about 0.11 eV below the conduction band of ZnS, which is similar to that obtained by simulating the thermal quenching of ZnSe photoluminescence.

Current-induced migration of surface adatoms during GaN growth by molecular beam epitaxy

The influence of electric fields on surface migration of Gallium (Ga) and Nitrogen (N) adatoms is studied during GaN growth by molecular beam epitaxy (MBE). When a direct current (DC) is used to heat the sample, long distance migration of Ga adatoms and diffusion asymmetry of N adatoms at steps are observed. On the other hand, if an alternating current (AC) is used, no such preferential adatom migration is found. This effect is attributed to the effective positive charges of surface adatoms. representing an effect of electro-migration. The implications of such current-induced surface migration to GaN epitaxy are subsequently investigated. It is seen to firstly change the distribution of Ga adatoms on a growing surface, and thus make the growth to be Ga-limited at one side of the sample but N-limited at the other side. This leads to different optical qualities of the film and different morphologies of the surface. (C) 2001 Elsevier Science B.V. All rights reserved.

Current-induced migration of surface adatoms during GaN growth by molecular beam epitaxy

The influence of electric fields on surface migration of Gallium (Ga) and Nitrogen (N) adatoms is studied during GaN growth by molecular beam epitaxy (MBE). When a direct current (DC) is used to heat the sample, long distance migration of Ga adatoms and diffusion asymmetry of N adatoms at steps are observed. On the other hand, if an alternating current (AC) is used, no such preferential adatom migration is found. This effect is attributed to the effective positive charges of surface adatoms. representing an effect of electro-migration. The implications of such current-induced surface migration to GaN epitaxy are subsequently investigated. It is seen to firstly change the distribution of Ga adatoms on a growing surface, and thus make the growth to be Ga-limited at one side of the sample but N-limited at the other side. This leads to different optical qualities of the film and different morphologies of the surface. (C) 2001 Elsevier Science B.V. All rights reserved.

Multi-electron processes in 4.15-11.08 keV/u(13)C(6+) on argon collisions

The relative partial cross sections for C-13(6+)-Ar collisions at 4.15-11.08 keV/u incident energy are measured. The cross-section ratios sigma(2E)/sigma(SC), sigma(3E)/sigma(SC), sigma(4E)/sigma(SC) and sigma(5E)/sigma(SC) are approximately the constants of 0.51 +/- 0.05, 0.20 +/- 0.03, 0.06 +/- 0.03 and 0.02 +/- 0.01 in this region. The significance of the multi-electron process in highly charged ions (HCIs) with argon collisions is demonstrated (sigma(ME)/sigma(SC) as high as 0.79 +/- 0.06). In multi-electron processes, it is shown that transfer ionization is dominant while pure electron capture is weak and negligible. For all reaction channels, the cross-sections are independent of the incident energy in the present energy region, which is in agreement with the static characteristic of classic models, i.e. the molecular Coulomb over-the-barrier model (MCBM), the extended classical over-the-barrier (ECBM) and the semiempirical scaling laws (SL). The result is compared with these classical models and with our previous work of C-13(6+)-Ne collisions

Multi-electron processes in C-13(6+) ions with neon collisions in energy region 4.15-11.08 keV/u

The cross-section ratios of double-, triple-, quadruple-, and the total multi-electron processes to the single electron capture process sigma(DE)/sigma(SC), sigma(TE)/sigma(SC), sigma(QE)/sigma(SC) and sigma(ME)/sigma(SC)) as well as the relative ratios among reaction channels in double-electron active, triple-electron active and quadruple- electron active are measured in C-13(6+) -Ne collision in the energy region of 4.15-11.08 keV/u by employing position-sensitive and time-of-flight coincident techniques. It is determined that the cross-section ratios sigma(DE)/sigma(SC), sigma(TE)/sigma(SC), sigma(QE)/sigma(SC) and sigma(ME)/sigma(SC) are approximately the constants of 0.20 +/- 0.03, 0.16 +/- 0.04, 0.06 +/- 0.02 and 0.42 +/- 0.05. These values are obviously smaller than the predictions of the molecular Coulomb over-the-barrier model (MCBM) [J. Phys. B 23 (1990) 4293], the extended classical over-the-barrier model (ECBM) [J. Phys. B 19 (1986) 2925] and the semiempirical scaling laws (SL) [Phys. Rev. A 54 (1996) 4127]. However, the relative ratios among partial processes of DE, TE and QE are found to depend on collision energy, which suggests that the collision dynamics depends on the collision velocity. The limitation of velocity-independent character of ECBM, MCBM and SL is undoubtedly shown.

Molecular dynamics and control following excitation with an ultra-short intense laser pulse

Vibronic excitations of the tri-atomic molecule OClO (A(2)A(2)(nu(1), nu(2), nu(3)) <-- (XB1)-B-2 (0, 0, 0)) with weak and strong ultra-short laser fields are studied within full quantum wavepacket dynamics in hyperspherical coordinates. Different dynamics is observed following excitation with laser pulses of different intensities. With a strong laser pulse, many vibrational states are excited and a spatially more localised wavepacket arises. The numerical results show that the population of different vibrational states of the wavepacket on the excited potential energy surface is altered by the intensity of the laser pulse. The numerical results also suggest a related effect on the phase of the wavepacket. These interesting phenomena can be understood by an analysis of the corresponding results for two model diatomic molecules. The possible physical mechanisms of control of chemical processes using strong laser fields are discussed. (C) 2004 Elsevier B.V. All rights reserved.

Numerical Simulation of Reactive Extrusion Processes for Activated Anionic Polymerization

In order to deal with the complicated relationships among the variables of the reactive extrusion process for activated anionic polymerization, a three-dimensional equivalent model of closely intermeshing co-rotating twin screw extruders was established. Then the numerical computation expressions of the monomer concentration, the monomer conversion, the average molecular weight and the fluid viscosity were deduced, and the numerical simulation of the reactive extrusion process of Styrene was carried out. At last, our simulated results were compared with Michaeli's simulated results and experimental results. (C) 2007 Elsevier B.V. All rights reserved

Investigation of the gel effect in reactive extrusion processes for free radical polymerization

The gel effect in the reactive extrusion process for free radical polymerization in a closely intermeshing co-rotating twin screw extruder was investigated. First the reaction kinetic model was constructed mainly on the basis of entanglement theory. Next, numerical calculation expressions for the initiator and monomer concentrations, monomer conversion, average molecular weight and apparent viscosity were deduced. Finally, the evolution of the above variables were shown and discussed for the example of butyl methacrylate. The simulated results of the monomer conversion are in good agreement with experimental results.

Computer simulation of reactive extrusion processes for free radical polymerization

The reactive extrusion for polymerization is an integrated polymer processing technology. A new semi-implicit iterative algorithm was proposed to deal with the complicated relationships among the chemical reaction, the macromolecular structure and the chemorheological property. Then the numerical computation expressions of the average molecular weight, the monomer conversion, and the initiator concentration were deduced, and the computer simulation of the reactive extrusion process for free radical polymerization was carried out, on basis of which reactive processing conditions can be optimized.

Study on reactive extrusion processes of block copolymer

The anionic copolymerization process of styrene-buradiene (S/B) block copolymer in a closely intermeshing co-rotating twin screw extruder with butyl-lithium initiator was studied. According to the anionic copolymerization mechanism and the reactive extrusion characteristics, the mathematical models of monomer conversion, average molecular weight and fluid viscosity during the anionic copolymerization of S/B were constructed, and then the reactive extrusion process was simulated by means of the finite volume method and the uncoupled semi-implicit iterative algorithm. Finally, the influence of the feeding mixture composition on conversion was discussed. The simulated results were nearly in agreement with the experimental results.

Molecular cloning and expression of a novel Kazal-type serine proteinase inhibitor gene from Zhikong scallop Chlamys farreri, and the inhibitory activity of its recombinant domain

Serine proteinase inhibitors (SPIs) play important roles in host physiological and immunological processes in all multicellular organisms. A novel Kazal-type SPI gene was cloned from the Zhikong scallop Chlamys farreri (designated as CfKZSPI) by expressed sequence tag (EST) and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of CfKZSPI was of 1788 nucleotides with a canonical polyadenylation signal sequence AATAAA and a polyA tail, and an open reading frame (ORF) encoding a polypeptide of 509 amino acids with a putative signal peptide of 22 amino acids. The deduced amino acid sequence of CfKZSPI contained 12 tandem Kazal domains with high similarity to other Kazal-type SPIs. The temporal expression of CfKZSPI in hemocytes after Vibrio anguillorum challenge was recorded by quantitative real-time RT-PCR. The relative mRNA expression level of CfKZSPI was up-regulated and reached 43.6-fold at 3 h post-challenge. After a decrease at 6 h, the expression Level increased again and reached 207.8-fold at 12 h post-challenge. The 12th Kazal domain of CfKZSPI was recombined into pET-32a(+) and expressed in Escherichia coli Rosetta-gami (DE3) to investigate its inhibitory activity. The purified recombinant protein (rCf KZSPI-1 2) showed significant inhibitory activity against trypsin but no activity against thrombin. When the molar ratio of inhibitor to trypsin reached 1:1, almost 90% of the enzyme activity could be inhibited, which suggested that one molecule of rCfKZSPI-12 was able to inhibit one molecule of trypsin. Kinetics analysis with Dixon plot showed that the inhibition constant (K-i) of rCfKZSPI-12 to trypsin was 173 nmol L-1. These results indicated that CfKZSPI was a novel Kazal-type SPI with significant inhibitory activity against trypsin, and was suspected to be involved in scallop immune response. (c) 2008 Elsevier Ltd. All rights reserved.

Stable carbon and nitrogen isotopic compositions of high molecular weight dissolved organic matter from four US estuaries

High molecular weight dissolved organic matter (HMW-DOM) represents an important component of dissolved organic carbon (DOC) in seawater and fresh-waters. In this paper, we report measurements of stable carbon (delta(13)C) isotopic compositions in total lipid, total hydrolyzable amino acid (THAA), total carbohydrate (TCHO) and acid-insoluble "uncharacterized" organic fractions separated from fourteen HMW-DOM samples collected from four U.S. estuaries. In addition, C/N ratio, delta(13) C and stable nitrogen (delta(15)N) isotopic compositions were also measured for the bulk HMW-DOM samples. Our results indicate that TCHO and THAA are the dominant organic compound classes, contributing 33-46% and 13-20% of the organic carbon in HMW-DOM while total lipid accounts for only <2% of the organic carbon in the samples. In all samples. a significant fraction (35-49%) of HMW-DOM was included in the acid-insoluble fraction. Distinct differences in isotopic compositions exist among bulk samples, the compound classes and the acid-insoluble fractions. Values of delta(13)C and delta(15)N measured for bulk HMW-DOM varied from -22.1 to -30.1parts per thousand and 2.8 to 8.9parts per thousand, respectively and varied among the four estuaries studied as well. Among the Compound classes, TCHO was more enriched in C-13 (delta(13)C = -18.5 to -22.8parts per thousand) compared with THAA (delta(13)C = -20.0 to -29.6parts per thousand) and total lipid (delta(13)C = -25.7 to -30.7parts per thousand). The acid-insoluble organic fractions, in general, had depleted C-13 values (delta(13)C = -23.0 to -34.4parts per thousand). Our results indicate that the observed differences in both delta(13)C and delta(15)N were mainly due to the differences in sources of organic matter and nitrogen inputs to these estuaries in addition to the microbial processes responsible for isotopic fractionation among the compound classes. Both terrestrial sources and local sewage inputs contribute significantly to the HMW-DOM pool in the estuaries studied and thus had a strong influence on its isotopic signatures. Copyright (C) 2004 Elsevier Ltd.

Bacterial roles in the formation of high-molecular-weight dissolved organic matter in estuarine and coastal waters: Evidence from lipids and the compound-specific isotopic ratios

High-molecular-weight dissolved organic matter (HMW-DOM, > 1,000 Daltons) is actively involved in the global biogeochemical cycling of many elements, but its carbon sources and detailed formation pathways are still not well understood. In this study, we measured bulk stable carbon and nitrogen isotopic ratios, lipid composition, and compound-specific carbon isotopic ratios of HMW-DOM samples collected from four U.S. estuaries (Boston Harbor/Massachusetts Bay, Delaware/Chesapeake Bay, San Diego Bay, and San Francisco Bay). Analytical results show (1) a fraction of HMW-DOM (lipid associated) in estuarine and coastal waters is derived from bacteria and phytoplankton; (2) this fraction of HMW-DOM is formed by various release processes of bacterial membrane components and bacterial reworking of phytoplankton-derived material; (3) this fraction of HMW-DOM is generally present in all samples from different coastal systems despite variable organic matter inputs and environmental conditions, suggesting an important bacterial role in HMW-DOM formation.