Monte Carlo simulation of the grafting of maleic anhydride onto polypropylene at higher temperature

The graft of maleic anhydride (MAH) onto isotactic polypropylene (iPP) initiated by dicumyl peroxide (DCP) at 190 degreesC was studied by means of the Monte Carlo method. The ceiling temperature theory, i.e., no possibility for the homopolymerization of MA-H to occur at higher temperatures, was used in this study. The simulation results show that most MAH monomers were grafted onto the radical chain ends arising from beta scission at a lower MAH concentration, whereas the amount of MAH monomers attached to the tertiary carbons was much larger than that grafted onto the radical chain ends at a higher MAH concentration for various DCP concentrations. This conclusion gives a good interpretation for the disagreement on the grafting sites along a PP chain. Moreover, it was found that the grafting degree increased considerably up to a peak value; thereafter, it decreased continuously with increasing MA-H concentration. The peak shifted in the lower MAH concentration direction and became lower and lower with increasing DCP concentration. When the DCP concentration was below 0.1 wt %, the peak was hardly observed. Those results are in good agreement with the experiments.

Shear induced mixing/demixing: Blends of homopolymers, of homopolymers plus copolymers, and blends in solution

Shear may shift the phase boundary towards the homogeneous state (shear induced mixing, SIM), or in the opposite direction (shear induced demixing, SID). SIM is the typical behavior of mixtures of components of low molar mass and polymer solutions, SID can be observed with solutions of high molar mass polymers and polymer blends at higher shear rates. The typical sequence with increasing shear rate is SIM, then occurrence of an isolated additional immiscible area (SLD), melting of this island into the main miscibility gap, and finally SIM again. A three phase line originates and ends in two critical end points. Raising pressure increases the shear effects. For copolymer containing systems SID is sometimes observed at very low shear rates, preceding the just mentioned sequence of shear influences.

LIQUID-CRYSTALLINE POLYSURFACTANT

A new kind of amphiphilic polymer(PAMC(16)B) has been synthesized where the amphiphilic moiety is attached as a side chain via the hydrophilic end to the polymer backbone. DSC, POM, and WAXD study revealed that the polysurfactant formed thermotropic liquid crystalline phase. The liquid crystalline domains appeared after annealed at the melt for a period of time, and evolved with annealing. It was indicated that the thermodynamic effect played a significant role on the self-aggregation of hydrophobic ends, so as to form liquid crystalline structure. X-ray investigation suggested that the mesophase structure could be described as smectic with lamellar type of packing, in which alkyl tails aggregated to form layer, A model of supermolecular structure was given.

AN INFRARED SPECTROSCOPIC CHARACTERIZATION OF THE SOLID SOLID BEHAVIOR OF DODECYLAMMONIUM CHLORIDE

The infrared spectra of the bilayer system dodecylammonium chloride has been studied as a function of temperature. Unusual splitting of some vibrational modes helps us to characterize the structure of different solid states. This study provided the evidence for the occurrence of an order-disorder phase transition whose onset occurs at 327 K and its completion ends at 339 K. In the low temperature phase below 327 K, the virgin crystals form a well-ordered phase with all-transhydrocarbon chains. In the intermediate state between 327 and 339 K, the data demonstrate the introduction of intramolecular as well as intermolecular disorder. The coexistence of solid and liquid-crystal-like states is shown by the persistence of factor group splittings together with the existence of defect bands in the wide intermediate temperature range. In the high temperature phase over 339 K the crystals convert to a liquid-crystal-like system with extensive motional and conformational disorder, but still show characteristics in their infrared spectra which indicate the presence of ordered segments in the hexagonal solid phase.

THE EFFECT OF RADIATION-INDUCED CROSS-LINKING ON THE RELAXATION OF TAUT TIE MOLECULES DURING ANNEALING OF DRAWN LDPE

Shrinkage, retractive stress, and infrared dichroism of the drawn low-density polyethylene (LDPE) as-drawn and irradiated by Co-60-ray have been measured under different annealing conditions. The shrinkage and the disorientation of the irradiated sample was undergone more rapidly than that of unirradiated one as the temperature was continuously increased, surpassing a certain value, and a higher degree of shrinkage and disorientation was achieved finally for the irradiated sample when the samples were annealed with free ends. For the samples heated isothermally with fixed ends, the retractive stress went through a maximum and then attenuated to a limited value, and the degree of such a stress attenuation for the unirradiated sample was much more than that for the irradiated sample. These results show that the taut tie molecules (TTMs) in drawn PE can relax by the pulling of chain segments out of crystal blocks that they anchored in at elevated temperatures higher than the a transition and also by the displacing of microfibrils if the samples were annealed with free ends. The cross-links produced by irradiation prohibit the former process. It was further observed that the dependence of the average extinction coefficient of the band at 2016 cm-1 on that of the band at 1894 cm-1 is related to irradiation and annealing conditions, which has also been explained by the relaxation of TTMs and the function of irradiation-induced cross-linking on the relaxation.

Molecular cloning and expression of a Relish gene in Chinese mitten crab Eriocheir sinensis

P>NF-kappa B is a B-cell specific transcription factor that plays crucial roles in inflammation, immunity, apoptosis, development and differentiation. In the present study, a novel NF-kappa B-like transcription factor Relish was cloned from Chinese mitten crab Eriocheir sinensis (designated as EsRelish) by rapid amplification of cDNA ends (RACE) technique based on expressed sequence tag (EST). The full-length cDNA of EsRelish was of 5034 bp, consisting of a 5' untranslated region (UTR) of 57 bp, a 3' UTR of 1335 bp with two mRNA instability motifs (ATTTA), a polyadenylation signal sequence (AATAAA) and a poly (A) tail, and an open reading frame (ORF) of 3645 bp encoding a polypeptide of 1214 amino acids with a calculated molecular mass of 134.8 kDa and a theoretical isoelectric point of 5.26. There were a typical Rel homology domain (RHD), two nuclear localization signal (NLS) sequences (KR), an inhibitor kappa B (I kappa B)-like domain with six ankyrin repeats, a PEST region and a death domain in the deduced amino acid sequence of EsRelish. Conserved domain, higher similarity with other Rel/NF-kappa Bs and phylogenetic analysis suggested that EsRelish was a member of the NF-kappa B family. Quantitative real-time RT-PCR was employed to detect the mRNA transcripts of EsRelish in different tissues and its temporal expression in hemocytes of E. sinensis challenged with Pichia methanolica and Listonella anguillarum. The EsRelish mRNA was found to be constitutively expressed in a wide range of tissues. It could be mainly detected in the hemocytes, gonad and hepatopancreas, and less degree in the gill, muscle and heart. The expression level of EsRelish mRNA in hemocytes was up-regulated from at 3, 6, 9 and 12 h after P. methanolica challenge. In L. anguillarum challenge, it was up-regulated at 9, 12 and 24 h. The results collectively indicated that EsRelish was potentially involved in the immune response against fungus and bacteria.

CLONING AND QUANTITATIVE ANALYSIS OF THE CARBONIC ANHYDRASE GENE FROM PORPHYRA YEZOENSIS

Carbonic anhydrase (CA), an enzyme that catalyzes the interconversion of CO2 and HCO3-, has a critical role in inorganic carbon acquisition in many kingdoms, including animals, plants, and bacteria. In this study, the full-length cDNA of the CA gene from Porphyra yezoensis Ueda (denoted as PyCA) was cloned by using an expressed sequence tag (EST) and rapid amplification of cDNA ends (RACE). The nucleotide sequence of PyCA consists of 1,153 bp, including a 5' untranslated region (UTR) of 177 bp, a 3' UTR of 151 bp, and an open reading frame (ORF) of 825 bp that can be translated into a 274-amino-acid putative peptide with a molecular mass (M) of 29.8 kDa and putative isoelectric point (pI) of 8.51. The predicted polypeptide has significant homology to the beta-CA from bacteria and unicellular algae, such as Porphyridium purpureum. The mRNA in filamentous thalli, leafy thalli, and conchospores was examined, respectively, by real-time fluorescent quantitative PCR (qPCR), and the levels of PyCA are different at different stages of the life cycle. The lowest level of mRNA was observed in leafy thalli, and the level in filamentous thalli and in the conchospores was 4-fold higher and 10-fold higher, respectively.

Molecular Cloning and Expression Analysis of a Cytosolic Hsp70 gene from Laminaria japonica (Laminariaceae, Phaeophyta)

In this study, a full-length cytosolic heat shock protein 70 complementary DNA (cDNA) of Laminaria japonica (designated as LJHsp70) was obtained by reverse transcriptase-polymerase chain reaction (RT-PCR) coupled with rapid amplification of cDNA ends. The full length of LJHsp70 cDNA was 2,918 bp, with a 5' untranslated region of 248 bp, a 3' untranslated region of 696 bp, and an open reading frame of 1,974 bp encoding a polypeptide of 657 amino acids with an estimated molecular mass of 72.03 kDa and an estimated isoelectric point of 4.97. There was highly repeated sequence of CAA in 5' untranslated region of LJHsp70. The result of phylogenetic tree of Hsp70s, the BLAST program, analysis and cytosolic Hsp70-specific motif of LJHsp70 verified that the cloned LJHsp70 belonged to cytosolic Hsp70 family. Three typical Hsp70 signature motifs were detected in LJHsp70 by InterPro analysis. Under different stress conditions, messenger RNA (mRNA) expression levels of LJHsp70 were quantified by quantitative RT-PCR. To L. japonica sporophytes kept in different temperatures for 1 h, the expression level of LJHsp70 at 30A degrees C was highest and twofold higher than that at 10A degrees C. To L. japonica sporophytes kept at 25A degrees C for different times, the mRNA expression level of LJHsp70 reached a maximum level after 7 h and then dropped progressively. The expression level of LJHsp70 at 0 or 5aEuro degrees salt concentration for 2 h was twofold higher than that at 30aEuro degrees salt concentration for 2 h. The results showed that LJHsp70 may be a kind of potential biomarker used to monitor environment conditions.

Molecular cloning and characterisation of prophenoloxidase (ProPO) cDNA from Fenneropenaeus chinensis and its transcription injected by Vibrio anguillarum

The prophenoloxidase(ProPO) gene was cloned from haemocytes of Chinese shrimp Fenneropenaeus chinensis by Rapid Amplification Complementary DNA Ends (RACE) method. The full-length cDNA of prophenoloxidase gene consists of 3040 bp with a 2061 bp Open Reading Frame (ORF), encoding 686 amino acids. Phylogenetic analysis revealed that it belongs to insect-type invertebrate prophenoloxidase gene family. To understand ProPO reaction for pathogeny's challenge in shrimp, the expressions of ProPO in different tissues were studied by real-time PCR after challenged by Vibrio anguillarum. The results showed that the expression level of ProPO gene in haemocytes was highest among three studied tissues including haemocytes, lymphoid organ and hepatopancreas. The time-course change of ProPO mRNA levels in challenge experiment showed that ProPO mRNA transcripts had the biggest change extent in lymphoid organ.

First molluscan TNFR homologue in Zhikong scallop: Molecular characterization and expression analysis

Tumor necrosis factor receptors (TNFRs) are a superfamily of proteins characterized by the unique cysteine-rich domain (CRD) and their important roles in diverse physiological and pathological events such as inflammation, apoptosis, autoimmunity and organogenesis. The first member of the molluscan TNFR family, designated as CfTNFR, was identified from Zhikong scallop Chlamys farreri by expressed sequence tag (EST) and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of CfTNFR was of 1334 bp, consisting of a 5' UTR of 17 bp, a 3'UTR of 69 by with a poly (A) tail, and an open reading frame (ORE) of 1248 by encoding a polypeptide of 415 amino acids with a theoretical isoelectric point of 8.33 and predicted molecular weight of 47.07 kDa. There were a signal peptide, a CRD, a transmembrane region and a death domain in the deduced amino acid sequence of CfTNFR, suggesting that it was a typical type 1 membrane protein. The high identities (22-40%) of CfTNFR with other TNFR superfamily members indicated that CfTNFR should be a member of TNFR superfamily, and moreover, it should be the first death domain-containing TNFR found in invertebrates. Phylogenetic analysis revealed that CfTNFR was closely related to TNFR-like proteins from Strongylocentrotus purpuratus, Drosophila melanogaster and Ciona intestinalis, and they formed a separate branch apart from vertebrate TNFRs. The spatial expression of CfTNFR transcripts in healthy and bacteria challenged scallops was examined by quantitative real-time PCR. CfTNFR transcripts could be detected in all tested tissues, including haemocytes, gonad, gill, mantle and hepatopancreas, and significantly up-regulated in the tissues of gonad, gill, mantle and hepatopancreas after Listonella anguillarum challenge, indicating that CfTNFR was constitutive and inducible acute-phase protein involved in immune defence. The present results suggested the existence of the TNFR-like molecules and TNF-TNFR system in low invertebrates, and provided new insights into the role of CfTNFR in scallop innate immune responses to invading microorganisms. (C) 2009 Elsevier Ltd. All rights reserved.

A serpin from Chinese shrimp Fenneropenaeus chinensis is responsive to bacteria and WSSV challenge

Arthropod defence responses (e.g. prophenoloxidase (proPO) activation and Toll pathway initiation) are mediated by serine proteinase cascades and regulated by serpins in haemolymph. A serpin (Fc-serpin) cDNA was cloned from the haemocytes of Fenneropenaeus chinensis by rapid amplification of cDNA ends (RACE) PCR and haemocyte cDNA library screening. The full-length cDNA consists of 1734 bp, encoding 411 amino acids with a calculated molecular mass of 46.55 kDa and a theoretical isoelectric point of 7.70. Fc-serpin contains a typical serpin-like homologue (serine proteinase inhibitors domain). The deduced protein contains a putative signal peptide of 19 amino acids and the serpin's signature sequence ((FHCNRPFLFLI389)-F-379). Fc-serpin showed some identity with Pacifastacus leniusculus serpin (42%) and Manduca sexta serpin-6 (34%). The reactive centre loop (RCL) sequences of Fc-serpin, P leniusculus serpin, M. sexta serpin-6 and Bombyx mori serpin-2 are highly similar. An Arg at the PI position of the reactive site indicates that Fc-serpin may have inhibitory activity against prophenoloxidase activating proteinase (PAP) and clotting enzyme. Transcripts of Fc-serpin mRNA were mainly detected in haemocytes and the lymphoid organ by RT-PCR. The variation of the mRNA transcription level in haemocytes followed by artificial infection with bacteria OF white spot syndrome virus (WSSV) was quantified by SYBR Green real-time PCR analysis. Expression profiles of Fc-serpin greatly fluctuated after challenge. This work represents the first report Of a serpin in penaeid shrimp. The data provide clues that Fc-serpin might play potential roles in the innate immunity of shrimp. (C) 2008 Elsevier Ltd. All rights reserved.

The complete mitochondrial genome sequence of the cutlassfish Trichiurus japonicus (Perciformes: Trichiuridae) : Genome characterization and phylogenetic considerations

Mitochondrial genome sequence and structure analysis has become a powerful tool for studying molecular evolution and phylogenetic relationships. To understand the systematic status of Trichiurus japonicus in suborder Scombroidei, we determined the complete mitochondrial genome (mitogenome) sequence using the long-polymerase chain reaction (long-PCR) and shotgun sequencing method. The entire mitogenome is 16,796 by in length and has three unusual features, including (1) the absence of tRNA(Pro) gene, (2) the possibly nonfunctional light-strand replication origin (O-L) showing a shorter loop in secondary structure and no conserved motif (5'-GCCGG-3'), (3) two sets of the tandem repeats at the 5' and 3' ends of the control region. The three features seem common for Trichiurus mitogenomes, as we have confirmed them in other three T. japonicus individuals and in T nanhaiensis. Phylogenetic analysis does not support the monophyly of Trichiuridae, which is against the morphological result. T. japonicus is most closely related to those species of family Scombridae; they in turn have a sister relationship with Perciformes members including suborders Acanthuroidei, Caproidei, Notothenioidei, Zoarcoidei, Trachinoidei, and some species of Labroidei, based on the current dataset of complete mitogenome. T japonicus together with T. brevis, T lepturus and Aphanopus carbo form a clade distinct from Lepidopus caudatus in terms of the complete Cyt b sequences. T. japonicus mitogenome, as the first discovered complete mitogenome of Trichiuridae, should provide important information on both genomics and phylogenetics of Trichiuridae. (C) 2009 Elsevier B.V. All rights reserved.

A thioredoxin with antioxidant activity identified from Eriocheir sinensis

Thioredoxin, with a redox-active disulfide/dithiol in the active site, is the major ubiquitous disulfide reductase responsible for maintaining proteins in their reduced state. In the present study, the cDNA encoding thioredoxin-1 (designated EsTrx1) was cloned from Chinese mitten crab Eriocheir sinensis by using rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of EsTrx1 was of 641 bp, containing a 51 untranslated region (UTR) of 17 bp, a 3' UTR of 306 bp with a poly (A) tail, and an open reading frame (ORF) of 318 bp encoding a polypeptide of 105 amino acids. The high similarity of EsTrx1 with Trx1s from other animals indicated that EsTrx1 should be a new member of the Trx1 sub-family. Quantitative real-time PCR analysis revealed the presence of EsTrx1 transcripts in gill, gonad, hepato-pancreas, muscle, heart and haemocytes. The expression of EsTrx1 mRNA in haemocytes was up-regulated after Listonella anguillarum challenge, reached the maximum level at 6 h post-stimulation, and then dropped back to the original level gradually. In order to elucidate its biological functions, EsTrx1 was recombined and expressed in E. coli BL21 (DE3). The rEsTrx1 was demonstrated to possess the expected redox activity in enzymatic analysis, and to be more potent than GSH in antioxidant capacity. These results together indicated that EsTrx1 could function as an important antioxidant in a physiological context, and perhaps is involved in the responses to bacterial challenge. (C) 2009 Elsevier Ltd. All rights reserved.

Molecular cloning and characterization of peroxiredoxin 6 from Chinese mitten crab Eriocheir sinensis

Peroxiredoxin is a superfamily of antioxidative proteins that play important roles in protecting organisms against the toxicity of reactive oxygen species (ROS). In this study, the full-length cDNA encoding peroxiredoxin 6 (designated EsPrx6) was cloned from Chinese mitten crab Eriocheir sinensis by using rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of EsPrx6 was of 1076 bp, containing a 5' untranslated region (UTR) of 69 bp, a 3' UTR of 347 bp with a poly (A) tail, and an open reading frame (ORF) of 660 bp encoding a polypeptide of 219 amino acids with the predicted molecular weight of 24 kDa. The conserved Prx domain, AhpC domain and the signature of peroxidase catalytic center identified in EsPrx6 strongly suggested that EsPrx6 belonged to the 1-Cys Prx subgroup. Quantitative real-time RT-PCR was employed to assess the mRNA expression of EsPrx6 in various tissues and its temporal expression in haemocytes of crabs challenged with Listonella anguillarum. The mRNA transcript of EsPrx6 could be detected in all the examined tissues with highest expression level in hepatopancreas. The expression level of EsPrx6 in haemocytes was down-regulated after bacterial challenge and significantly decreased compared to the control group at 12 h. As time progressed, the expression level began to increase but did not recover to the original level during the experiment. The results suggested the involvement of EsPrx6 in responses against bacterial infection and further highlighted its functional importance in the immune system of E sinensis. (C) 2009 Elsevier Ltd. All rights reserved.

A cyclophilin A inducible expressed in gonad of zhikong scallop Chlamys farreri

Cyclophilin A (CypA), a receptor for the immunosuppressive agent cyclosporin A (CsA), is a cis-trans peptidyl-prolyl isomerase (PPIase) which accelerates the cis-trans isomerization of prolyl-peptide bonds, interacts with a variety of proteins and therefore regulates their activities. One CypA (designated CfCypA) cDNA was cloned from Chlamys farreri by expressed sequence tag (EST) and rapid amplification of cDNA ends (RACE) techniques. The full-length cDNA of CfCypA consisted of 1,248 nucleotides with a canonical polyadenylation signal sequence AATAAA, a poly (A) tail, and an open reading frame (ORF) of 495 nucleotides encoding a polypeptide of 164 amino acids. The deduced amino acid sequence shared high similarity with CypA from the other species, indicating that CfCypA should be a new member of the CypA family. Quantitative real-time (RT) PCR was employed to assess the mRNA expression of CfCypA in various tissues and its temporal expression in haemocytes and gonad of scallops challenged with Vibrio anguillarum. The mRNA transcripts of CfCypA could be detected in all the examined tissues with highest expression level in gonad. After bacterial challenge, the expression level of CfCypA was almost unchanged in haemocytes, but up-regulated in gonad and increased to the peak (22.59-fold; P < 0.05) at 4 h post-injection, and then dropped to the original level at 8 h post-injection. These results indicated that CfCypA was constitutive expressed in haemocytes, but could be induced in gonad, and perhaps played a critical role in response to the bacterial challenge in gonad.