Modeling the adsorptive selectivity of carbon nanotubes for effective separation of CO2/N2 mixtures

Canonical Monte Carlo (CMC) simulations were carried out to investigate the behavior of CO₂ and N₂ mixtures upon adsorption on single walled carbon nanotubes (CNTs). In the simulation, all the particle–particle interactions between CO₂, N and C were modeled using Lennard-Jones (LJ) potential. To provide deep insight into the effect of pore width, temperature, pressure and bulk composition on the adsorption behavior of CO₂ /N₂ mixtures, five different CNTs [(6,6), (7,7), (8,8) (9,9) and (10,10) CNT] with diameters ranging from 0.807 to 1.35 nm, three temperatures (300 323 and 343 K), six pressures (0.15, 2, 4, 6, 8 and 10 MPa), and three bulk mole compositions of carbon dioxide (0.3 0.5 and 0.7) were tested. The results from all the simulation conditions investigated in this work show that CNTs preferentially adsorb carbon dioxide relative to nitrogen in a binary mixture. The results are consistent with the hypothesis that stronger interaction of one component with the nanotube surface results in a higher adsorption capacity compared to the other component. An optimized pore size of D = 8.07 nm corresponding to (6, 6) CNT, at T = 300 K and P = 0.15 MPa at a bulk mole composition of y_CO2 =0.3 was identified in which carbon nanotubes demonstrate the greatest selectivity for separation of carbon dioxide relative to nitrogen. In addition, it is worth pointing out that, under similar simulation conditions, CNTs exhibit higher selectivity compared to other carbon-based materials [carbon membrane polyimide (PI) and PI/multi-wall carbon nanotubes (MWCNTs)] for CO₂ adsorption. As a prototype, the selectivity of an equimolar mixture of CO₂ /N₂ for adsorption on (6, 6) CNTs at 300 K and 0.15 MPa reaches 9.68, which is considerably larger than that reported in carbon membrane. Therefore, it can be concluded that carbon nanotubes can act as a capable adsorbent for adsorption/desorption of CO₂ in comparison with other carbon-based materials in the literature.     

Evaluation of complementary effects of 9,10-anthraquinone and fumaric acid on methanogenesis and ruminal fermentation in vitro

The objective of the present study was to investigate the hypothesis that 9,10-anthraquinone (AQ) in combination with fumaric acid (FMA) may provide complementary effects to inhibit methanogens and enhance rumen's capacity for better utilisation of FMA towards propionate production. Three levels of AQ and four levels of FMA were tested in a 3 x 4 factorial design using in vitro gas production technique. AQ reduced the total gas and methane production significantly. The combination of 4 ppm AQ with FMA had additive effect on concentration of propionate. Supplementation of AQ alone resulted in hydrogen accumulation (p < 0.001), whereas presence of FMA (up to 6.5 mM) along with AQ declined hydrogen concentration (p < 0.001). The level of 4 ppm AQ did not affect in vitro digestibility, however, a reduction of organic matter digestibility was caused by 8 ppm AQ (p < 0.001), which was partially compensated by the addition of FMA (p = 0.06). The optimum FMA level depended on the AQ concentration. At 4 ppm AQ, a FMA level of 3.5 mM had best possible effect on partitioning factor and microbial biomass production (p < 0.001), though, at 8 ppm AQ the higher level of FMA (6.5 mM) responded better. Overall, FMA in combination with AQ provided an alternative hydrogen sink and might be introduced as a novel strategy for mitigation of enteric methane emission. Nevertheless, the result should be proved by in vivo experiments.     

The potential of brewer's spent grain to improve the production of α-amylase by Bacillus sp. KR-8104 in submerged fermentation system

Brewer's spent grain (BSG) was used as a solid substrate for the production of α-amylase by Bacillus sp. KR-8104 in a submerged fermentation system. The production of α-amylase was maximized through statistical optimization of the BSG concentration and incubation time using the Doehlert experimental design. The highest tested amount of BSG (5%, w/v) in the optimization process resulted in a 5.1-fold enhancement of the response. Subsequently, we studied the role of the water-soluble and -insoluble fractions of BSG in the production of α-amylase. The results revealed that whole BSG had a greater effect on the production of α-amylase than each fraction had separately. Finally, when we examined the potential of BSG to replace the constituents of a medium formula, we observed that simultaneously adding BSG, omitting dextrin, and reducing the other ingredients concentration in the culture medium improved the production of α-amylase and made the production process more economical.     

Gender differences in healthy ranges for serum alanine aminotransferase levels in adolescence

Background & Aims

There is a worldwide epidemic of obesity among adolescents who subsequently are at increased risk for the development of non alcoholic fatty liver disease (NAFLD). The serum alanine aminotransferase (ALT) is the most frequently used test for screening these individuals, but no age and gender-specific upper limits of normal (ULN) based on healthy population data in children are available. The objective of the present study was to define ULN for ALT in healthy children in order to use this as a tool for case finding.

Methods

A total of 975 school children (aged 7–18 years) were included in the study cohort. Highly significant correlations (all p<0.001) were noted between ALT values and measures of BMI, systolic and diastolic blood pressure, insulin levels, HOMA-IR, total cholesterol and triglyceride concentrations. In order to define the population with no risk factors, we excluded subjects having abnormal values for factors that correlated with ALT. This population comprised 186 boys and 185 girls.

Results

In boys, median serum ALT levels were 16 IU/L and 9, 11, 18, and 30 IU/L for the 5th, 25th, 75th, and 95th percentiles. In girls, median serum ALT was 13, and 7, 9, 16, and 21 IU/L for the 5th, 25th, 75th, and 95th percentiles, respectively. The ULNs for ALT were 30 IU/L and 21 IU/L for boys and girls respectively. We found a linear relationship between age and ALT in females (p<0.001) but not in males. By multiple logistic regression, independent predictors of an elevated ALT included the BMI, waist hip ratio and levels of serum total cholesterol. In females, age was an additional inverse predictor.

Conclusions

In children and adolescents, these normal limits for ALT should be applied. Those with persistent elevations should be investigated further.     

The stimulatory effect of CaCl(2), NaCl and NH(4)NO(3) salts on the ssDNA-binding activity of RecA depends on nucleotide cofactor and buffer pH

The single-stranded DNA binding activity of the Escherichia coli RecA protein is crucial for homologous recombination to occur. This and other biochemical activities of ssDNA binding proteins may be affected by various factors. In this study, we analyzed the effect of CaCl(2), NaCl and NH(4)NO(3) salts in combination with the pH and nucleotide cofactor effect on the ssDNA-binding activity of RecA. The studies revealed that, in addition to the inhibitory effect, these salts exert also a stimulatory effect on RecA. These effects occur only under very strict conditions, and the presence or absence and the type of nucleotide cofactor play here a major role. It was observed that in contrast to ATP, ATPγS prevented the inhibitory effect of NaCl and NH(4)NO(3), even at very high salt concentration. These results indicate that ATPγS most likely stabilizes the structure of RecA required for DNA binding, making it resistant to high salt concentrations.     

Protein secondary structure prediction using three neural networks and a segmental semi Markov model

Prediction of protein secondary structure is an important step towards elucidating its three dimensional structure and its function. This is a challenging problem in bioinformatics. Segmental semi Markov models (SSMMs) are one of the best studied methods in this field. However, incorporating evolutionary information to these methods is somewhat difficult. On the other hand, the systems of multiple neural networks (NNs) are powerful tools for multi-class pattern classification which can easily be applied to take these sorts of information into account.To overcome the weakness of SSMMs in prediction, in this work we consider a SSMM as a decision function on outputs of three NNs that uses multiple sequence alignment profiles. We consider four types of observations for outputs of a neural network. Then profile table related to each sequence is reduced to a sequence of four observations. In order to predict secondary structure of each amino acid we need to consider a decision function. We use an SSMM on outputs of three neural networks. The proposed SSMM has discriminative power and weights over different dependency models for outputs of neural networks. The results show that the accuracy of our model in predictions, particularly for strands, is considerably increased.     

Identification of a high affinity FcgammaRIIA-binding peptide that distinguishes FcgammaRIIA from FcgammaRIIB and exploits FcgammaRIIA-mediated phagocytosis and degradation

FcgammaRIIA is a key activating receptor linking immune complex formation with cellular effector functions. FcgammaRIIA has 93% identity with an inhibitory receptor, FcgammaRIIB, which negatively regulates FcgammaRIIA. FcgammaRIIA is important in the therapeutic action of several monoclonal antibodies. Binding molecules that discriminate FcgammaRIIA from FcgammaRIIB may optimize receptor activity and serve as a lead for development of therapeutics with FcgammaRIIA as a key target. Here we report the use of phage display libraries to select short peptides with distinct FcgammaRIIA binding properties. An 11-mer peptide (WAWVWLTETAV) was characterized that bound FcgammaRIIA with a K(d) of 500 nm. It mediated cell internalization and degradation of a model antigen. The peptide-binding site on FcgammaRIIA was shown to involve Phe(163) and the IgG binding amino acids Trp(90) and Trp(113). It is thus overlapping but not identical to that of IgG. Neither activating receptors FcgammaRI and FcgammaRIII, nor FcgammaRIIB, all of which lack Phe(163), bound the peptide.     

Cloning,expression and immunogenicity of ferric enterobactin binding protein Fep B from <Emphasis Type="Italic">Escherichia coli</Emphasis> O157:H7

The gene coding for ferric enterobactin binding protein from E. coli O157:H7 was amplifi ed. This gene was cloned and expressed as C-terminal His (6)-tagged protein. The SDS-PAGE analysis of the total protein revealed only two distinct bands, with molecular masses of 31kDa and 34kDa. The Ni-NTA chromatography purifi ed FepB and the osmotically shocked periplasmic fraction of IPTG induced cells showed only a single band of 31 kDa. Polyclonal mouse antibody was raised against the recombinant protein during 4 weeks after immunization. Western blot analysis of the recombinant FepB with mouse antiserum revealeda single band of 31 kDa. Identification and purification of FepB helped reveal its appropriate molecular mass. Polyclonal antibody raised against the recombinant protein reacted with bacterial FepB. The recombinant protein FepB could have a protective effect against E. coli O157:H7 and might be useful as an effective vaccine.     

The effect of thidiazuron level on in vitro regeneration type and peroxidase profile in <Emphasis Type="Italic">Eucalyptus microtheca</Emphasis> F. Muell

The green twigs of 1-year-old Eucalyptus microtheca F. Muell seedlings were cultured on modified MS medium, supplemented with α-naphthalene acetic acid (NAA) and kinetin (Kin) hormones at 12 different concentrations. After 4 weeks, the combination of 1 mg l⁻¹ NAA + 1 mg l⁻¹ Kin induced the highest number of axillary shoots. Meanwhile, embryogenic calli were observed in media containing 4 mg l⁻¹ NAA + 0.5 mg l⁻¹ Kin, without any regeneration. The hormone treatments were followed by subculturing the twigs in different levels of thidiazuron (TDZ). The combination of 1 mg l⁻¹ NAA + 1 mg l⁻¹ Kin together with 0.01 mg l⁻¹ TDZ resulted in an increase of direct shoot, while higher amounts of TDZ led to adventitious shoot induction. Somatic embryogenesis was observed in the treatment containing 0.01 mg l⁻¹ TDZ + 4 mg l⁻¹ NAA + 0.5 mg l⁻¹Kin. The peroxidase (POD) band patterns in regenerated plantlets were investigated in order to determine the effect of different levels of TDZ on loci synthesis. A dimer locus, a tetramer locus and two epigenetic bands (a new band for NAA + Kin and the other for TDZ) were observed in the POD profiles. In case of low (0.01 mg l⁻¹ and 0.1 mg l⁻¹) levels of TDZ, one heterozygote allele was disappeared from dimer locus, while at higher TDZ levels, the dimer locus lost its stability and tetramer locus showed a high activity. Thus, POD allele patterns seems to be a feasible marker for different types of regeneration.