Amino acid overproduction by analog resistant mutants of the nitrogen fixing cyanobacteriumAnabaena sp 287

Two amino acid analog resistant mutants of the cyanobacteriumAnabaena sp 287 were isolated after MNNG mutagenesis.Anabaena ST 16, a mutant resistant to the alanine analog D-α-aminobutyric acid andAnabaena ST 25, another mutant resistant to the histidine analog l,2,4-triazole-3-alanine, released alanine and histidine, respectively, into the medium upon immobilization in alginic acid during diazotrophic growth in fluidized bed reactors. The rates of amino acid production by the mutants were 4.3 μmol mg chl^-1 h^-1 of D-alanine byAnabaena ST 16 and 16.6 μnol mg chl^-1 h^-1 of L-histidine byAnabaena ST 25. Nitrogen fixation by the mutants was not affected by the extracellular amino acid concentration. While the radioactive carbon flow was followed, the parent strain retained 93% of fixed¹⁴C and released only 7% into the medium. On the other hand,Anabaena ST 16 released 13% andAnabaena ST 25 released 29% into the medium. These mutants are beneficial in the production of radioactive amino acids using diazotrophic photobiotechnology.     

Molecular basis for antifreeze activity difference of two insect antifreeze protein isoforms

The insect spruce budworm(Choristoneura fumiferana) produces antifreeze protein(AFP) to assist in the protection of the over-wintering larval stage and contains multiple isoforms. Structures for two isoforms,known as CfAFP-501 and CfAFP-337,show that both possess similar left-handed β-helical structure,although thermal hysteresis activity of the longer isoform CfAFP-501 is three times that of CfAFP-337. The markedly enhanced activity of CfAFP-501 is not proportional to,and cannot be simply accounted for,by the increased ice-binding site resulting from the two extra coils in CfAFP-501. In or-der to investigate the molecular basis for the activity difference and gain better understanding of AFPs in general,we have employed several different computational methods to systematically study the structural properties and ice interactions of the AFPs and their deletion models. In the context of intact AFPs,a majority of the coils in CfAFP-501 has better ice interaction and causes stronger ice lattice disruption than CfAFP-337,strongly suggesting a cooperative or synergistic effect among β-helical coils. The synergistic effect would play a critical role and make significant contributions to the anti-freeze activity β-helical antifreeze proteins. This is the first time that synergistic effect and its implica-tion for antifreeze activity are reported for β-helical antifreeze proteins.     

Assessment of corrosion resistance of surface-coated galvanized steel by analysis of the AC impedance spectra measured on the salt-spray-tested specimen

In the present work, corrosion resistance of surface-coated galvanized steel was quantitatively determined by an analysis of the alternating current (AC) impedance spectra measured on the salt-spray-tested specimen. To evaluate the corrosion resistance of the surface-coated galvanized steel, AC impedance spectroscopy was performed on the salt-spray-tested specimen previously exposed to salt-sprayed corrosive environment. From the analysis of the impedance spectra, the area fraction transient of white rust θ ₂(t) was theoretically derived from the equivalent circuit equation by using two fitting parameters. The values of the two fitting parameters were determined by fitting the empirical transient equations to the area fraction of the resin coating layer and to the total resistance obtained from the impedance spectra measured, respectively. From the analyses of θ ₂(t) for four kinds of surface-coated galvanized steels with various resin coating layers, it is indicated that as the values of the two fitting parameters decrease in the order of CP, GI, OD and OM (commercial trade names) specimens, the corrosion resistance increases in that order as well. Furthermore, from the quantitative comparison of the two fitting parameters with the polarization resistance of the upper resin coating layer R _p determined from the potentiodynamic polarization curve, it is suggested that the two fitting parameters decrease in value as well with increasing R _p.     

Photoinduced graft polymerization of 2-methacryloyloxyethyl phosphorylcholine on polyethylene membrane surface for obtaining blood cell adhesion resistance

Phospholipid polymer, poly[2-methacryloyloxyethyl phosphorylcholine (MPC)], was grafted with polyethylene (PE) membrane using photoinduced polymerization technique to make the membrane resistant to cell adhesion. The water contact angle on the PE membrane grafted with poly(MPC) decreased with an increase in the photopolymerization time. This decrease corresponded to the increase in the amount of poly(MPC) grafted on the PE surface. The same graft polymerization procedure was applied using other hydrophilic monomers, such as acrylamide (AAm), N-vinylpyrrolidone (VPy) and methacryloyl poly(ethylene glycol) (MPEG). These monomers were also polymerized to form grafted chains on the PE membrane, and the grafting was confirmed with X-ray photoelectron spectroscopy. Analysis of amount and distribution of plasma proteins at the plasma-contacting surface of the original and the modified PE membranes were analyzed using immunogold assay. The grafting of poly(MPC) and poly(VPy) on PE membrane reduced the plasma protein adsorption significantly compared with that on the original PE membrane. However, the PE membranes grafted with poly(AAm) or poly(MPEG) did not show any effects on protein adsorption. Platelet adhesion on the original and modified PE membranes from platelet-rich plasma was also examined. A large number of platelets adhered and activated on the original PE membrane. Grafting with poly(AAm) did not suppress platelet adhesion, but grafting with poly(MPC) or poly(VPy) on the PE membrane was effective in preventing platelet adhesion. It is concluded that the introduction of the phosphorylcholine group on the surface could decrease the cell adhesion to substrate polymer.     

Novel method for bulk resistance evaluation in conductivity measurement for high-purity water

A major issue with the electrolytic conductivity measurement for pure water is the lack of standard or reference methods. A primary method traceable to SI and suitable for pure-water conductivity measurement was developed at the Physikalisch-Technische Bundesanstalt (PTB), Germany, as the base for the calibration method for the conductivity measuring devices at the low conductivity level. This paper provides a novel method to calculate the bulk resistance of pure water using impedance measured at a single frequency, which is one of the key procedures for the primary methods.     

Characterization of a convection-based support microstructure through a flow resistance parameter

Modern convection-based supports differ substantially in pore size, porosity, and microstructure topology. Due to such variability, it is challenging to evaluate the contribution of a particular microstructure topology on flow resistance. We demonstrated that the flow resistance parameter ($\varphi$) introduced decades ago can be used as a criterion to evaluate the effect of microstructure topology on a pressure drop when the pore size is used as a characteristic support dimension. Furthermore, the $\varphi$ value of simple cubic packing was calculated over the entire range of open porosity and compared to the $\varphi$ values determined for pressure drop models derived for particular convection-based supports and experimental values of various convection-based supports from the literature. It was shown that different convection-based supports become clustered into distinct groups when plotted according to their $\varphi$ and open porosity values, allowing their discrimination.     

Industrial Application of Hybrid Sol-Gel Coatings for the Decoration of Crystal Glassware

The coloration of glass via melting techniques presents some unique problems with respect to the reproducibility, toxicology and economics of certain colors, especially if the market demands are highly variable. This is also the case for consumer products such as crystal glass and tableware. Traditionally, the decoration of crystal glasses is performed by laborious manual techniques, which are costly and do not meet modern market requirements. Alternatively, spraying of colored lacquers is a highly flexible and valuable tool for the development of new products. Sol-gel type hybrid coatings provide several advantages compared to conventional organic systems like high abrasion resistance, almost perfect adhesion, refractive index matching and sufficient stability in dishwashing procedures. The solubility of organic dyes in the hybrid matrix is sufficient for intense colors even at rather low layer thicknesses, which on the other hand convey the high brilliance of the base material. The development of transparent, translucent and opaque hybrid coatings for crystal glass has been completed in the last few years and the production of partially coated articles has started recently. The synthesis and properties of the coating material are reviewed and the industrial process and first market results are also outlined.     

Resistance analysis for enhanced wastewater membrane filtration

This study investigated enhancement techniques for synthetic wastewater filtration in a membrane bioreactor (MBR) at mixed liquor suspended solids concentrations (MLSS) of 12–18 g/L. Air sparging (AS), backflushing (BF) and a combined application of both (AS + BF) were applied to increase permeate flux compared to the conventional application (NON). Scanning electron microscope (SEM) measurements of cake thickness served for evaluating cleaning effectiveness and as input data for some of the model calculations. AS + BF showed the lowest overall resistance, and thus the highest permeate yield, for about 2 weeks of observation. The contribution of fouling resistance, cake resistance and membrane resistance to the overall resistance was evaluated, based on experimental data. Air sparging significantly lowered cake thickness and consequently cake resistance. The experimental cake resistance and the model resistances were compared. A model based on the measured cake thickness and literature values for the specific surface area proved most successful. Finally, a relationship between the backflush resistance and the permeate flow resistance was observed.     

A Procedure for Transforming Impedance Spectra for the Determination of Mechanism of Electrochemical Reactions

Transformation of impedance spectra into relaxation time spectra (RTS) is used for determining contributions of individual processes of the oxygen electroreduction reaction (OER) to the polarization resistance of the electrochemical cell. The transformation technique involves the solution of the convolution equation found with the aid of a modified Van Cittert iteration algorithm checked on model impedance spectra. The technique, when used to analyze impedance spectra of electrochemical cells air|Pt|YSZ|YSZ + Pt|air, shows that the conversion of a globular structure of the YSZ + Pt cermet layer to a columnar one is accompanied by a change of peak amplitudes in RTS. The revealed RTS dynamics when heated to 750°C is compared with peculiarities of individual processes in OER.     

2-Oxo-3,4-dihydropyrimido[4,5-d] pyrimidines as new reversible inhibitors of EGFR C797S (Cys797 to Ser797) mutant

Extensive structure-activity relationships (SARs) study of JND3229 was conducted to yield a series of new reversible 2-oxo-3,4-dihydropyrimido[4,5-d]pyrimidine privileged scaffold as EGFR^C797S inhibitors. One of the most potent compound 6i potently suppressed EGFR^{L858R/T790M/C797S} kinase with an IC₅₀ value of 3.1 nmol/L, and inhibited the proliferation of BaF3 cells harboring EGFR^{L858R/T790M/C797S} and EGFR^{19D/T790M/C797S} mutants with IC₅₀ values of 290 nmol/L and 316 nmol/L, respectively. Further, 6i dose-dependently induced suppression of the phosphorylation of EGFR^{L858R/T790M/C797S} and EGFR^{19D/T790M/C797S} in BaF3 cells. Compound 6i may serve as a promising lead compound for further drug discovery overcoming the acquired resistance of non-small cell lung cancer (NSCLC) patients.