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Genetic selection system for improving recombinant membrane protein expression in<i>E. coli</i>
Massey-Gendel, Elizabeth,Zhao, Anni,Boulting, Gabriella,Kim, Hye-Yeon,Balamotis, Michael A.,Seligman, Len M.,Nakamoto, Robert K.,Bowie, James U. Wiley (John WileySons) 2009 Protein science Vol.18 No.2
<P>A major barrier to the physical characterization and structure determination of membrane proteins is low yield in recombinant expression. To address this problem, we have designed a selection strategy to isolate mutant strains of Escherichia coli that improve the expression of a targeted membrane protein. In this method, the coding sequence of the membrane protein of interest is fused to a C-terminal selectable marker, so that the production of the selectable marker and survival on selective media is linked to expression of the targeted membrane protein. Thus, mutant strains with improved expression properties can be directly selected. We also introduce a rapid method for curing isolated strains of the plasmids used during the selection process, in which the plasmids are removed by in vivo digestion with the homing endonuclease I-CreI. We tested this selection system on a rhomboid family protein from Mycobacterium tuberculosis (Rv1337) and were able to isolate mutants, which we call EXP strains, with up to 75-fold increased expression. The EXP strains also improve the expression of other membrane proteins that were not the target of selection, in one case roughly 90-fold.</P>
Removal of Cu(II) by biosorption onto coconut shell in fixed-bed column systems
Mike A. Acheampong,Kannan Pakshirajan,Ajit P. Annachhatre,Piet N.L. Lens 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.3
Biosorption of Cu(II) onto coconut shell, an agricultural biomaterial, was studied in a fixed-bed column. The Cu(II) biosorption column had the best performance at 10 mg Lˉ1 inlet Cu(II) concentration, 10 mL minˉ1 flow rate and 20 cm bed depth. The equilibrium uptake of Cu(II) amounted to 7.25 mg gˉ1. The simulation of the breakthrough curve was successful with the BDST and Yoon–Nelson models, but the entire breakthrough curve was best predicted by the Clark model. The design of a fixed bed column for Cu(II)removal from wastewater by biosorption onto coconut shell can be done based on these models.
Anatoliy Zavdoveev,A. Len,E. Pashinska 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.3
Small angle neutron scattering was applied to steel produced by rolling with shear (RS) technology and compared to samplesproduced by standard technology (ST). Based on small angle neutron scattering measurements the morphology of the grainsand pores of RS steels were compared to those of the ST steels. The scattering in small scattering vector region showedanisotropy, attributed to the elongation of the pores; the pearlite lamellae distances along and perpendicular to the rollingdirections differed by a factor of 1.5. The results of the Small angle neutron scattering measurements were in accordancewith the electrical characteristics of the specimens. They showed smaller and less anisotropic average sizes of the cracksand nanopores for the RS samples than for the ST rods. This confirms the dynamic healing of the nanosized defects duringthe cold drawing of the RS rods. This fundamental result shows that during severe plastic deformation a cyclic process ofnucleation and healing of the nanovoids took place. However, during the standard deformation process only nucleation ofthe nanovoids is present.
Kanjanapruthipong, J.,Len, R.A. Asian Australasian Association of Animal Productio 1998 Animal Bioscience Vol.11 No.3
The paper presented here is aimed at increasing knowledge on purine metabolism in ruminants and hence the quantification of microbial cells entering the small intestine from urinaη excretion of purine derivatives. Nucleic acid metabolisms of micro-organisms in the rumen, digestion and absorption of nucleic acids entering the intestines, metabolisms of absorbed and endogenous purines involving de novo synthesis of nucleic acids in the ruminants host, and the relationship between absorbed and excreted purines are reviewed. Principal concerns about an amount of purine derivatives excreted in urine in relation to a change in purine-N: total-N ratios in rumen microbes that leave the rumen are discussed. The use of urinary excretion of purine derivatives as an indicator of the amount of microbial biomass leaving the rumen has to be done with some caution since it may be impossible to get a representative sample of microbes entering the intestine and thus yield estimates are relative rather than absolute.