Effects of animal-plant protein ratio in extruded and expanded diets on nitrogen and energy budgets of juvenile Chinese soft-shelled turtle (Pelodiscus sinensis Wiegmann)

In this study, we investigated the effects of animal-plant protein ratio in extruded and expanded diets on nutrient digestibility, nitrogen and energy budgets of juvenile soft-shelled turtle (Pelodiscus sinensis). Four extruded and expanded feeds (diets 1-4) were formulated with different animal-plant protein ratios (diet 1, 1.50:1; diet 2, 2.95:1; diet 3, 4.92:1; diet 4, 7.29:1). The apparent digestibility coefficients (ADCs) of dry matter and crude lipid for diet 1 were significantly lower than those for diets 2-4. There was no significant difference in crude protein digestibility among diets 1-4. The ADC of carbohydrate was significantly increased with the increase in animal-plant protein. Although nitrogen intake rate, faecal nitrogen loss rate and excretory nitrogen loss rate of turtles fed diet 1 were significantly higher than those fed diets 2-4, nitrogen retention rate, net protein utilization and biological value of protein in these turtles were significantly lower than those fed diets 2-4. In addition, energy intake rate, excretory energy loss rate and heat production rate of turtles fed diet 1 were also significantly higher than those fed diets 2-4. Faecal energy loss was significantly reduced with the increase in the animal-plant protein ratio. The ADC of energy and assimilation efficiency of energy significantly increased with a higher animal-plant protein ratio. The growth efficiency of energy in the group fed diet 1 was significantly lower than those in the groups fed diets 2-4. Together, our results suggest that the optimum animal-plant protein ratio in extruded and expanded diets is around 3:1.

Comparative study on in vitro inhibition of grass carp (Ctenopharyngodon idellus) and mouse protein phosphatases by microcystins

Microcystins isolated from toxic cyanobacteria are potent inhibitors of protein phosphatases 1 and 2A (PP1 and PP2A). The inhibitory effects of three structural variants of microcystins (microcystin-LR, -YR, and -RR) on protein phosphatases isolated and purified from the liver and kidney of grass carp (Ctenopharyngodon idellus) were investigated using the P-32 radiometric assay. The relationships between percentage inhibition of protein phosphatase activity and microcystin levels followed a typical dose-dependent sigmoid curve. These results were compared to those obtained from mouse PP2A. The degree and pattern of inhibition of both fish and mouse protein phosphatases by microcystins were similar. Protein phosphatases in crude fish tissue homogenates showed similar inhibition patterns as purified fish PP2A toward microcystins. (C) 2000 by John Wiley & Sons, Inc.

Symmetry and optical transition rule for low-dimensional semiconductor system with spin-orbit interaction and magnetic field

Starting from effective mass Hamiltonian, we systematically investigate the symmetry of low-dimensional structures with spin-orbit interaction and transverse magnetic field. The position-dependent potentials are assumed to be space symmetric, which is ever-present in theory and experiment research. By group theory, we analyze degeneracy in different cases. Spin-orbit interaction makes the transition between Zeeman sub-levels possible, which is originally forbidden within dipole approximation. However, a transition rule given in this paper for the first time shows that the transition between some levels is forbidden for space symmetric potentials. (C) 2009 Elsevier Ltd. All rights reserved.

Magnetotransport in two-dimensional electron gas: The interplay between spin-orbit interaction and Zeeman splitting

We investigate theoretically the interplay between Zeeman splitting, Rashba spin-orbit interaction (RSOI), and Dresselhaus spin-orbit interaction (DSOI) and its influence on the magnetotransport property of two-dimensional electron gas (2DEG) at low temperature. Our theoretical results show that the nodes of the beating patterns of the magnetoresistivity rho(xx) for 2DEG with RSOI or DSOI alone depend sensitively on the total spin splitting induced by these three spin splitting mechanisms. It is interesting to find that the eigenstates in the presence of RSOI alone are connected with those in the presence of DSOI alone but with opposite Zeeman splitting by a time-reversal transformation. Consequently, the magnetoresistivities exhibit exactly the same oscillation patterns for these two cases. For strong RSOI or DSOI alone, the magneto-oscillation of rho(xx) shows two distinct periods. For 2DEG with both RSOI and DSOI, the beating patterns vanish for equal RSOI and DSOI strengths and vanishing Zeeman splitting. They will appear again, however, when Zeeman splitting or the difference between RSOI and DSOI strengths increases.

Study of competitive binding of enantiomers to protein by affinity capillary electrochromatography

Affinity capillary electrochromatography (CEC) with zonal elution method was used to probe the competitive interactions of enantiomers with protein. In this approach, a known concentration of a competing agent is continuously applied to a CEC column with bovine serum albumin (BSA) physically adsorbed on SAX packing while injections of a small amount of analyte are made. The binding sites of solutes on the BSA molecule were determined by the changes in the retention factors of the solutes resulted from the addition of competitive agent. By using D- or L-tryptophan as competitive agents and D-, L-tryptophan and benzoin enantiomers as injected analytes showed that BSA molecule has a primary site to strongly bind L-tryptophan, but D-tryptophan dose not bind at this site; D- and L-tryptophan share a weak binding site on the BSA molecule. Benzoin enantiomers do not share any binding sites with either D- or L-tryptophan. Non-chiral compounds of trichloroacetic acid and n-hexanoic acid were applied as the competitive agents to study the binding of warfarin enantiomers to BSA, it was observed that trichloroacetic acid and n-hexanoic acid had a same binding site for warfarin enantiomers binding to BSA molecule. (C) 2002 Elsevier Science B.V. All rights reserved.

Uncovering the rules for protein-protein interactions from yeast genomic data

Identifying protein-protein interactions is crucial for understanding cellular functions. Genomic data provides opportunities and challenges in identifying these interactions. We uncover the rules for predicting protein-protein interactions using a frequent pattern tree (FPT) approach modified to generate a minimum set of rules (mFPT), with rule attributes constructed from the interaction features of the yeast genomic data. The mFPT prediction accuracy is benchmarked against other commonly used methods such as Bayesian networks and logistic regressions under various statistical measures. Our study indicates that mFPT outranks other methods in predicting the protein-protein interactions for the database used. We predict a new protein-protein interaction complex whose biological function is related to premRNA splicing and new protein-protein interactions within existing complexes based on the rules generated.

Electrostatic assembly of protein lysozyme on DNA visualized by atomic force microscopy

In the present work, atomic force microscopy (AFM) has been used to study the assembly of protein lysozyme on DNA molecule. Based on the electrostatic interaction, the positively charged lysozyme can easily bind onto the negatively charged DNA molecule surface. The protein molecules appear as globular objects on the DNA scaffold, which are distinguishable in the AFM images. At the same time, lysozyme molecules can be assembled onto DNA as dense or sporadic pattern by varying the protein concentration. This work may provide fundamental aspects for building protein nanostructures and studying of DNA-protein interaction.

Assembly of Prussian blue onto SiO2 nanoparticles and carbon nanotubes by electrostatic interaction

Prussian blue (PB) was modified onto surface of SiO2 nanoparticles and multiwall carbon nanotubes (MWNTs) by electrostatic assembled method. SiO2 nanoparticles and MWNTs firstly modified by polyelectrolyte exhibited positive charges and negative charged PB could be assembled onto them. UV-vs spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field-emitted scanning electron microscopy (FE-SEM) and electrochemical methods were used to characterize these composite nanomaterials. TEM and FE-SEM images showed that PB was easily assembled onto polyelectrolyte modified SiO2 nanoparticles and MWNTs. Moreover, PB on the surface of nanomaterials was stable and still kept its intrinsic electrochemical properties and high electrocatalytic activity towards hydrogen peroxide.

The structure of Aquifex aeolicus sulfide:quinone oxidoreductase, a basis to understand sulfide detoxification and respiration

Sulfide: quinone oxidoreductase (SQR) is a flavoprotein with homologues in all domains of life except plants. It plays a physiological role both in sulfide detoxification and in energy transduction. We isolated the protein from native membranes of the hyperthermophilic bacterium Aquifex aeolicus, and we determined its X-ray structure in the "as-purified,'' substrate-bound, and inhibitor-bound forms at resolutions of 2.3, 2.0, and 2.9 angstrom, respectively. The structure is composed of 2 Rossmann domains and 1 attachment domain, with an overall monomeric architecture typical of disulfide oxidoreductase flavoproteins. A. aeolicus SQR is a surprisingly trimeric, periplasmic integral monotopic membrane protein that inserts about 12 angstrom into the lipidic bilayer through an amphipathic helix-turn-helix tripodal motif. The quinone is located in a channel that extends from the si side of the FAD to the membrane. The quinone ring is sandwiched between the conserved amino acids Phe-385 and Ile-346, and it is possibly protonated upon reduction via Glu-318 and/or neighboring water molecules. Sulfide polymerization occurs on the re side of FAD, where the invariant Cys-156 and Cys-347 appear to be covalently bound to polysulfur fragments. The structure suggests that FAD is covalently linked to the polypeptide in an unusual way, via a disulfide bridge between the 8-methyl group and Cys-124. The applicability of this disulfide bridge for transferring electrons from sulfide to FAD, 2 mechanisms for sulfide polymerization and channeling of the substrate, S2-, and of the product, S-n, in and out of the active site are discussed.

Characterization of degQ(Vh), a serine protease and a protective immunogen from a pathogenic Vibrio harveyi strain

Vibrio harveyi is an important marine pathogen that can infect a number of aquaculture species. V. harveyi degQ (degQ(Vh)), the gene encoding a DegQ homologue, was cloned from T4, a pathogenic V. harveyi strain isolated from diseased fish. DegQ(Vh) was closely related to the HtrA family members identified in other Vibrio species and could complement the temperature-sensitive phenotype of an Escherichia coli strain defective in degP. Expression of degQVh in T4 was modulated by temperature, possibly through the sigma(E)-like factor. Enzymatic analyses demonstrated that the recombinant DegQVh protein expressed in and purified from E. coli was an active serine protease whose activity required the integrity of the catalytic site and the PDZ domains. The optimal temperature and pH of the recombinant DegQVh protein were 50 C and pH 8.0. A vaccination study indicated that the purified recombinant DegQVh was a protective immunogen that could confer protection upon fish against infection by V. harveyi. In order to improve the efficiency of DegQVh as a vaccine, a genetic construct in the form of the plasmid pAQ1 was built, in which the DNA encoding the processed DegQVh protein was fused with the DNA encoding the secretion region of AgaV, an extracellular beta-agarase. The E.coli strain harboring pAQ1 could express and secrete the chimeric DegQVh protein into the culture supernatant. Vaccination of fish with viable E. coli expressing chimeric degQ(Vh) significantly (P < 0.001) enhanced the survival of fish against V. harveyi challenge, which was possibly due to the relatively prolonged exposure of the immune system to the recombinant antigen produced constitutively, albeit at a gradually decreasing level, by the carrier strain.

Characterization of degQ(Vh), a serine protease and a protective immunogen from a pathogenic Vibrio harveyi strain

Vibrio harveyi is an important marine pathogen that can infect a number of aquaculture species. V. harveyi degQ (degQ(Vh)), the gene encoding a DegQ homologue, was cloned from T4, a pathogenic V. harveyi strain isolated from diseased fish. DegQ(Vh) was closely related to the HtrA family members identified in other Vibrio species and could complement the temperature-sensitive phenotype of an Escherichia coli strain defective in degP. Expression of degQVh in T4 was modulated by temperature, possibly through the sigma(E)-like factor. Enzymatic analyses demonstrated that the recombinant DegQVh protein expressed in and purified from E. coli was an active serine protease whose activity required the integrity of the catalytic site and the PDZ domains. The optimal temperature and pH of the recombinant DegQVh protein were 50 C and pH 8.0. A vaccination study indicated that the purified recombinant DegQVh was a protective immunogen that could confer protection upon fish against infection by V. harveyi. In order to improve the efficiency of DegQVh as a vaccine, a genetic construct in the form of the plasmid pAQ1 was built, in which the DNA encoding the processed DegQVh protein was fused with the DNA encoding the secretion region of AgaV, an extracellular beta-agarase. The E.coli strain harboring pAQ1 could express and secrete the chimeric DegQVh protein into the culture supernatant. Vaccination of fish with viable E. coli expressing chimeric degQ(Vh) significantly (P < 0.001) enhanced the survival of fish against V. harveyi challenge, which was possibly due to the relatively prolonged exposure of the immune system to the recombinant antigen produced constitutively, albeit at a gradually decreasing level, by the carrier strain.

Identification and analysis of a Sciaenops ocellatus ISG15 homologue that is involved in host immune defense against bacterial infection

ISG15 is an interferon-stimulated gene that encodes a ubiquitin-like protein. ISG15 homologues have been identified in a number of fish species, some of which are known to be regulated at expression level by virus infection and lipopolysacchande (LPS) treatment However, the relationship between ISG15 and live bacterial infection has not been investigated in piscine models. In this study, an ISG15 homologue, SoISG15, was identified from red drum Scraeriops ocellaws and analyzed at expression and functional levels The open reading frame ofSolSG15 is 477 base pairs (bp) and mtronless, with a 5'-untranslated region (UTR) of 91 bp and a 3'-UTR of 415 bp The deduced amino acid sequence of S0ISG15 shares 60-67% overall identities with the ISG15 of several fish species. S0ISG15 possesses two conserved ubiquinn-like domains and the canonical ubiquitin conjugation motif, LRGG, at the C-terminus. Expressional analysis showed that constitutive expression of SolSG15 was highest in blood and lowest in kidney Experimental challenges with LPS and bacterial pathogens induced significant S0ISG15 expression in the kidney but not in the liver Similar differential induction was also observed at cellular level with primary hepatocytes and head kidney (HK) lymphocytes. Poly(' C), however, effected drastic induction of S0ISG15 expression in kidney and liver at both tissue and cellular levels. Immunoblot analysis showed that S0ISG15 was secreted by cultured HK lymphocytes into the extracellular milieu. Recombinant S0ISG15 expressed in and purified from Eschenclua colt was able to enhance the respiratory burst activity, acid phosphatase activity, and bactericidal activity of HK macrophages. Taken together, the results of this study indicated that SoISG 15 possesses apparent immunological property and is likely to be involved in host immune defense against bacterial infection. (C)2010 Elsevier Ltd All rights reserved.

Evolutionary analysis of phycobiliproteins: Implications for their structural and functional relationships

Phycobiliproteins, together with linker polypeptides and various chromophores, are basic building blocks of phycobilisomes, a supramolecular complex with a light-harvesting function in cyanobacteria and red algae. Previous studies suggest that the different types of phycobiliproteins and the linker polypeptides originated from the same ancestor. Here we retrieve the phycobilisome-related genes from the well-annotated and even unfinished cyanobacteria genomes and find that many sites with elevated d(N)/d(S) ratios in different phycobiliprotein lineages are located in the chromophore-binding domain and the helical hairpin domains (X and Y). Covariation analyses also reveal that these sites are significantly correlated, showing strong evidence of the functional-structural importance of interactions among these residues. The potential selective pressure driving the diversification of phycobiliproteins may be related to the phycobiliprotein-chromophore microenvironment formation and the subunits interaction. Sites and genes identified here would provide targets for further research on the structural-functional role of these residues and energy transfer through the chromophores.

Expression, purification of recombinant flounder MRF4 protein in Escherichia coli and analysis of its polyclonal antibodies

MRF4 is one of muscle regulatory factors and plays critical roles during skeletal muscle development. The muscle development is important for the fish growth which is an important economic factor for the fish culture. To analyze the function of MRF4 in fish, the founder MRF4 antibody was prepared. The flounder MRF4 was cloned, ligated into prokaryotic expression vector pET-30b and expressed in strain E. coli BL21 (130). The recombinant flounder MRF4 fusion protein was soluble and purified with cobalt IMAC resins. To prepare MRF4 polyclonal antibodies, rabbits were immunized with the soluble protein and the increasing level of antibodies was determined by Western blot. Also, the endogenous flounder MRF4 was recognized by the anti-serum. The result further proved the existence of the anti-MRF4 antibody in the anti-serum, which will be useful for studies on the function of flounder MRF4.