Construction of recombinant Escherichia coli strais for production of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate)

Plastic wastes constitute a worldwide environmental problem, and the demand for biodegradable plastics has become high. One of the most important characteristics of microbial polyesters is that they are thermoplastic with environmentally degradable properties. In this study, pUC 19/PHA was cloned and transformed into three different Escherichia coli strains. Among the three strains that were successfully expressed in the production of polyhydroxyalkanoates (PHA), E. coli HMS174 had the highest yield in the production of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (P[HB-HV]). The cell dry weight and PHA content of recombinant HMS174 reached as high as 10.27 g/L and 43% (w/w), respectively, in fed-batch fermentor culture. The copolymer of PHA, P(HB-HV), was found in the cells, and the biopolymers accumulated were identified and analyzed by gas chromatography, proton nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. We demonstrated clearly that the E. coli host for PHA production has to be carefully selected to obtain a high yield. The results obtained indicated that a superior E. coli with high PHA production can be constructed with a desirable ratio of P(HB-HV), which has potential applications in industry and medicine.     

Comparison of liquid chromatography/mass spectrometry, ELISA, and phosphatase assay for the determination of microcystins in blue-green algae products

More than 100 samples of blue-green algae products (consisting of Aphanizomenon, Spirulina, and unidentified blue-green algae) in the form of pills, capsules, and powders were collected from retail outlets from across Canada. The samples were extracted with 75% methanol in water and centrifuged to remove solids. Aliquots of the extracts along with spiked blank sample extracts were sent to each participating laboratory and independently analyzed for microcystins by enzyme-linked immunosorbent assay (ELISA), protein phosphatase inhibition assay, and by liquid chromatography-tandem mass spectrometry (LC-MS/MS) after sample cleanup using C18 solid-phase extraction. The results obtained by ELISA and LC-MS/MS agreed very well over a concentration range of about 0.5-35 microg/g. The colorimetric phosphatase results generally agreed with the other 2 methods. While the 2 biochemical assays measured total microcystin content compared with a standard of microcystin LR, the LC-MS/MS method measured specific microcystins (LA, LR, RR, YR) using external standards of these for identification and quantitation. Microcystin LR was found in all positive samples by LC-MS/MS. Microcystin LA was the only other microcystin found in the samples analyzed. These 2 microcystins represent essentially all the microcystins that were present in the extracts. Otherwise, the LC-MS/MS results would have been significantly lower than the results of the biochemical assays had other unknown microcystins been present.     

Reverse micelles dissolved in supercritical xenon: an NMR spectroscopic study

Reverse micelles currently gain increasing interest in chemical technology. They also become important in biomolecular NMR due to their ability to host biomolecules such as proteins. In the present paper, a procedure for the preparation of high-pressure NMR samples containing reverse micelles dissolved in supercritical xenon is presented. These reverse micelles are formed by sodium bis(2-ethylhexyl) sulfosuccinate (AOT). For the first time, NMR spectroscopy could be applied to reverse micelles in supercritical xenon. The AOT/H(2)O/Xe system was studied as a function of experimental parameters such as xenon pressure, water content, and salt concentration. Optimum conditions for reverse micelle formation in supercritical xenon could be determined. It is, furthermore, demonstrated that biomolecules such as amino acids and proteins can be incorporated into the reverse micelles dissolved in supercritical xenon.     

Development and validation of analytical methodology using capillary electrophoresis for separation and determination of anions in rainwater

A new capillary electrophoresis (CE) procedure was developed for simultaneous determination of both organic and inorganic anions in rain water using a background electrolyte (BGE) containing 5 mM molybdate, 0.15 mM CTAH, 0.01% PVA and 5 mM Tris buffer to adjust pH at 7.9. Under optimised conditions, good repeatability (RSD for sulphate in migration time=0.36% and peak area=4.2%), low detection limit (2 ppb for chloride) and satisfactory working range (50 ppb-20 ppm for hydrodynamic injection, 10 ppb-3 ppm for electrokinetic injection for chloride) were obtained. The reliability of the CE procedure developed was established by satisfactory recovery tests and good agreement of results obtained by both the CE and ion chromatography (IC) methods. The procedure developed had been successfully applied for field monitoring of rainwater showing good repeatability and capability of detecting trace anions at ppb levels beyond the IC working range. Thus, the new CE procedure developed provides a quick, sensitive, economic and reliable method to meet the need for the simultaneous determination of both organic and inorganic anions in the acid rain monitoring programme.     

Heterometallic MIIRuIII2 compounds constructed from trans-[Ru(Salen)(CN)2]- and trans-[Ru(Acac)2(CN)2]-. Synthesis, structures, magnetic properties, and density functional theoretical study

The synthesis, structures, and magnetic properties of four cyano-bridged M(II)Ru(III)2 compounds prepared from the paramagnetic Ru(III) building blocks, trans-[Ru(salen)(CN)2]- 1 [H2salen = N,N'-ethylenebis(salicylideneimine)] and trans-[Ru(acac)2(CN)2]- (Hacac = acetylacetone), are described. Compound 2, {Mn(CH3OH)4[Ru(salen)(CN)2]2}.6CH3OH.2H2O, is a trinuclear complex that exhibits antiferromagnetic coupling between Mn(II) and Ru(III) centers. Compound 3, {Mn(H2O)2[Ru(salen)(CN)2]2.H2O}n, has a 2-D sheetlike structure that exhibits antiferromagnetic coupling between Mn and Ru, leading to ferrimagnetic-like behavior. Compound 4, {Ni(cyclam)[Ru(acac)2(CN)2]2}.2CH3OH.2H2O (cyclam = 1,4,8,11-tetraazacyclotetradecane), is a trinuclear complex that exhibits ferromagnetic coupling. Compound 5, {Co[Ru(acac)2(CN)2]2}n, has a 3-D diamond-like interpenetrating network that exhibits ferromagnetic ordering below 4.6 K. The density functional theory (DFT) method was used to calculate the molecular magnetic orbitals and the magnetic exchange interaction between Ru(III) and M(II) (Mn(II), Ni(II)) ions.     

Application of Cleavable Linkers to Improve Therapeutic Index of Radioligand Therapies

Radioligand therapy (RLT) is an emergent drug class for cancer treatment. The dose administered to cancer patients is constrained by the radiation exposure to normal tissues to maintain an appropriate therapeutic index. When a radiopharmaceutical or its radiometabolite is retained in the kidneys, radiation dose deposition in the kidneys can become a dose-limiting factor. A good exemplar is [¹⁷⁷Lu]Lu-DOTATATE, where patients receive a co-infusion of basic amino acids for nephroprotection. Besides peptides, there are other classes of targeting vectors like antibody fragments, antibody mimetics, peptidomimetics, and small molecules that clear through the renal pathway. In this review, we will review established and emerging strategies that can be used to mitigate radiation-induced nephrotoxicity, with a focus on the development and incorporation of cleavable linkers for radiopharmaceutical designs. Finally, we offer our perspectives on cleavable linkers for RLT, highlighting future areas of research that will help advance the technology.     

Physical fabrication of colloidal ZnO nanoparticles combining wet-grinding and laser fragmentation

Combination of wet-grinding and laser fragmentation is a promising approach to advance both methods: Laser fragmentation will be more efficient when combined with mechanical treatment and wet-grinding may take advance of the abrasion-free laser process to achieve fabrication of smaller particles. By mechanical pre-treatment of zinc oxide microparticles in a stirred-media mill, the starting material is activated by generation of crystallographic defects, which strongly enhance the efficiency of subsequent laser fragmentation. Picosecond-laser irradiation of mechanically treated and untreated microparticles suspended in water yielded in colloidal zinc oxide nanoparticles. Furthermore, nanoparticle productivity and properties can be controlled by variation of anionic surfactant concentration.