Improvement of Porcine Interferon-α Production by Recombinant <Emphasis Type="Italic">Pichia pastoris</Emphasis> via Induction at Low Methanol Concentration and Low Temperature

Improved porcine interferon-α (pIFN-α) production by recombinant Pichia pastoris was achieved by culture conditions optimization in a 5-l bioreactor. The results indicated that the pIFN-α concentration, specific methanol consumption rate, specific activities of alcohol oxidase, formaldehyde dehydrogenase, and formate dehydrogenase could be significantly enhanced by decreasing induction temperature. The highest pIFN-α concentration (1.35 g l⁻¹) was obtained by simultaneously controlling methanol concentration at 5 g l⁻¹ and induction temperature at 20 °C, which was about 1.6-fold higher than the maximum obtained with previous optimal methanol concentration level (about 10 g l⁻¹) when inducing at 30 °C. The potential mechanisms behind low temperature and low methanol concentration effect on pIFN-α production may be ascribed to higher cell metabolic activity, more carbon flux towards pIFN-α production, and less intracellular/extracellular protease release.     

Low temperature and size controlled synthesis of monodispersed γ-Fe<Subscript>2</Subscript>O<Subscript>3 </Subscript>nanoparticles by an epoxide assisted sol–gel route

Monodispersed γ-Fe₂O₃ nanoparticles were prepared by a procedure-simple and precursor-cheap route, epoxide assisted sol–gel method. The γ-Fe₂O₃ nanoparticles were obtained by the reaction of FeCl₂ in ethanol solution with propylene oxide to form the sol, following by the boiling of the solution. As compared with other metal ions of +2 formal charge, the unexpected acidity of FeCl₂ in ethanol solution assure the formation of sol. As an advantage, the unique chemistry of this route results in the low temperature of synthesis, leading to the extremely small particle size of 2.3 nm and non-aggregation state of the particles.     

Influence of the Water Content on the Thermal Behaviour of β-Cyclodextrin at Low and Very Low Temperature

Heat capacities of -CD·9.7H₂O weremeasured by adiabatic calorimetry in the temperature range10–300 K. Differential scanning calorimetry wasused to follow the evolution of the thermalbehaviour versus hydration ratio between 170 and300 K. At least three different behaviours wereobserved, according to the number, n, of watermolecules: 0 < n < 7, 7 < n < 10, and n > 10.These macroscopic results are discussed in terms oforganization differences between the most or theleast hydrated -CD. The structuring effectof the hydration water molecules is emphasised. Theexistence of two energetically distinct -CDhydrates (n < 10 and n > 10) seems to be confirmed. Thishypothesis is discussed in comparison with previousspectroscopic and structural studies.     

Low temperature heat capacity of bulk and nanophase ZnO and Zn1−xCoxO wurtzite phases

The low temperature heat capacity of the ZnO–CoO solid solution system was measured from 2 to 300 K using the heat capacity option of a Quantum Design Physical Property Measurement System (PPMS). The thermodynamic functions in this temperature range were derived by curve fitting. The standard entropies of bulk ZnO and bulk ZnO–CoO (wurtzite, 18 mol% CoO) at T = 298.15 K were calculated to be (43.1 ± 0.4) J · mol⁻¹ · K⁻¹ and (45.2 ± 0.5) J · mol⁻¹ · K⁻¹, respectively. The surface entropy of ZnO was evaluated to be (0.02 ± 0.01) mJ · K⁻¹ · m⁻², which is essentially zero. No sharp magnetic transitions were observed in the solid solution samples. The nanophase solid solution, 12 mol% CoO, appears to bind H₂O on its surface more strongly than ZnO.     

Upconverting‐Nanoparticle‐Assisted Photochemistry Induced by Low‐Intensity Near‐Infrared Light: How Low Can We Go?

Upconverting nanoparticles (UCNPs) convert near‐infrared (NIR) light into UV or visible light that can trigger photoreactions of photosensitive compounds. In this paper, we demonstrate how to reduce the intensity of NIR light for UCNP‐assisted photochemistry. We synthesized two types of UCNPs with different emission bands and five photosensitive compounds with different absorption bands. A λ=974 nm laser was used to induce photoreactions in all of the investigated photosensitive compounds in the presence of the UCNPs. The excitation thresholds of the photoreactions induced by λ=974 nm light were measured. The lowest threshold was 0.5 W cm^?2, which is lower than the maximum permissible exposure of skin (0.726 W cm^?2). We demonstrate that low‐intensity NIR light can induce photoreactions after passing through a piece of tissue without damaging the tissue. Our results indicate that the threshold for UCNP‐ assisted photochemistry can be reduced by using highly photosensitive compounds that absorb upconverted visible light. Low excitation intensity in UCNP‐assisted photochemistry is important for biomedical applications because it minimizes the overheating problems of NIR light and causes less photodamage to biomaterials.     

Low temperature preparation and electric properties of highly (100)-oriented Pb<Subscript>0.8</Subscript> La<Subscript>0.1</Subscript>Ca<Subscript>0.1</Subscript>Ti<Subscript>0.975</Subscript>O<Subscript>3</Subscript> thin films prepared by a sol–gel route

Highly (100)-oriented Pb_0.8La_0.1Ca_0.1Ti_0.975O₃ (PLCT) thin films deposited on Pt/Ti/SiO₂/Si substrate were successfully achieved by a sol–gel route. The influence of annealing temperature on microstructures and electric properties was investigated; it was found that the PLCT film could be crystallized only at 450 °C. When the annealing temperature increased to 500 °C, the PLCT film exhibited highly (100)-oriented, which also possessed higher remnant polarization Pr (27 μC/cm²) and better pyroelectric figure of merit (F _d = 205 μC/m²k) at room temperature. It was also found too high annealing temperature (625 °C) could lead to recrystallization of film, and the small grains caused by recrystallization could make polarization reversal difficult and disturbed the preferred crystal growth in film, which was not benefit to obtain enhanced electric properties.     

Low temperature ionic conductor: ionic liquid incorporated within a metal–organic framework

Ionic liquids (ILs) show promise as safe electrolytes for electrochemical devices. However, the conductivity of ILs decreases markedly at low temperatures because of strong interactions arising between the component ions. Metal–organic frameworks (MOFs) are appropriate microporous host materials that can control the dynamics of ILs via the nanosizing of ILs and tunable interactions of MOFs with the guest ILs. Here, for the first time, we report on the ionic conductivity of an IL incorporated within a MOF. The system studied consisted of EMI-TFSA (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide) and ZIF-8 (Zn(MeIM)₂, H(MeIM) = 2-methylimidazole) as the IL and the MOF, respectively. While the ionic conductivity of bulk EMI-TFSA showed a sharp decrease arising from freezing, the EMI-TFSA@ZIF-8 showed no marked decrease because there was no phase transition. The ionic conductivity of EMI-TFSA@ZIF-8 was higher than that of bulk EMI-TFSA below 250 K. This result points towards a novel method by which to design electrolytes for electrochemical devices such as batteries that can operate at low temperatures.     

Low temperature synthesis of Co<Subscript>2</Subscript>SiO<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> nanocomposite using a modified sol–gel method

The paper presents a study on the preparation of Co₂SiO₄/SiO₂ nanocomposites by a new modified sol–gel method. We have prepared gels starting from tetraethylorthosilicate (Si(OC₂H₅)₄), cobalt nitrate Co(NO₃)₂·6H₂O and some diols: ethylene glycol (C₂H₆O₂), 1,2propanediol (C₃H₈O₂) and 1,3propanediol (C₃H₈O₂), for a final composition: 30% CoO/70% SiO₂. During the heating of the gels at 140 °C, a redox reaction takes place between NO₃ ⁻ ions and diol with formation of some carboxylate anions. These carboxylate anions react with the Co(II) ions to form coordination compounds embedded in silica matrix, as evidenced by FT-IR spectrometry and thermal analysis. These Co(II) coordinative compounds thermally decompose in the range 250–300 °C to the corresponding oxides: CoO and/or Co₃O₄ inside the matrices pores. When CoO results, it reacts with SiO₂ at low temperature leading to Co₂SiO₄, which crystallizes at 700 °C. XRD patterns of the samples annealed at temperatures lower than 700 °C were characteristic to amorphous phases. The samples annealed at temperatures ≥700 °C, contain Co₂SiO₄ (olivine) as unique crystalline phase inside the amorphous silica matrix, according to XRD patterns. As evidenced by TEM images, Co₂SiO₄ nanoparticles are homogenously dispersed inside the silica matrix.     

Primary photophysical and photochemical processes upon UV excitation of PtBr<Subscript>6</Subscript><Superscript>2–</Superscript> and PtCl<Subscript>6</Subscript><Superscript>2–</Superscript> complexes in water and methanol

Primary photophysical and photochemical processes were studied for Pt^IVBr₆ ^2– and Pt^IVCl₆ ^2– complexes in water and methanol by ultrafast kinetic spectroscopy upon excitation in the band region of charge transfer from the ligand-centered group π-orbitals to the e_g*-orbital of Pt^IV complex anion (LMCT bands). The data obtained earlier upon excitation in the region of d—d bands were compared. Irrespective of the excitation wavelength, the photochemical properties of complexes are caused by the reactions of intermediates proceeding in the picosecond time range. These intermediates were identified as Pt^IVBr₅ ^– upon photolysis of Pt^IVBr₆ ^2– and, presumably, the Adamson radical pair [Pt^IIICl₅ ^2–(C _4v )...Cl?] upon photolysis of Pt^IVCl₆ ^2–. The difference in the exciting light wavelengths has an impact only on the first step of these processes, i.e., transition from the Franck—Condon excited state to intermediates.     

Thermal,XRD, and magnetization studies on ZnAl<Subscript>2</Subscript>O<Subscript>4</Subscript> and NiAl<Subscript>2</Subscript>O<Subscript>4</Subscript> spinels,synthesized by citrate precursor method and annealed at 450 and 650 °C

Two aluminate spinel materials (ZnAl₂O₄ and NiAl₂O₄) were synthesized by the citrate precursor method. The citrate precursors consisting of coprecipitated citrates of Zn²⁺ or Ni²⁺ and aluminum were first subjected to thermal analysis (TG-DSC) for determining the optimum temperature for annealing. Two step decomposition was observed incorporating dehydration and formation of the aluminate. The second step gives an endo peak (−2937 J/g) at 356 °C in the DSC curve of the coprecipitated nickel(II) citrate–aluminum citrate gel in O₂ atmosphere. Kinetic/mechanistic analysis of the TG data has also been carried out and values of E _a, ΔS ^#, ΔG ^#, and A were approximated. On the basis of the findings, 450 °C has been chosen for annealing of the gels. Annealing has also been done at 650 °C for 1 h in muffle furnace in an attempt to obtain nanometric particles of aluminates (MAl₂O₄) {M = Ni, Zn} and to find out their magnetic properties which could render them useful for chemical sensing applications, etc. The TG-DSC curves of various powders which were obtained on annealing at the two temperatures did exhibit thermal instability when carried out in N₂ atmosphere. NiAl₂O₄ and ZnAl₂O₄ spinels (particle size 17 and 34 nm, respectively) are obtained in pure crystalline phase at 650 °C. ZnAl₂O₄ prepared this way shows coercivity values of 470 and 58.37 G and NiAl₂O₄, 107 and 23.24 G when annealed at 450 and 650 °C, respectively. ZnAl₂O₄ prepared by a polymer precursor method and annealed at 1000 °C, has earlier been reported to have coercivity value of 469 G. Thus, the citrate precursor method is good for the synthesis of ZnAl₂O₄, producing single phase nanocrystalline powder of high quality and crystallinity. The value of magnetization was found to be small in the present case for the NiAl₂O₄ spinel obtained at 450 °C.     

Microwave-assisted hydrothermal synthesis and electrochemical studies of α- and h-MoO<Subscript>3</Subscript>

Two modifications of molybdenum trioxide with orthorhombic (α-MoO₃) and hexagonal (h-MoO₃) crystal structure have been synthesized by a microwave-assisted hydrothermal method, facilitated by formic acid. Characterization by means of X-ray diffraction, scanning electron microscopy, specific surface analysis, and Fourier-transform infrared, Raman, and UV-Vis spectroscopy reveals phase-pure crystalline powder samples of hexagonal h-MoO₃ microrods and of α-MoO₃ nanobelt bundles, respectively. The electrochemical properties of the MoO₃ compounds, studied by cyclic voltammetry and galvanostatic cycling vs. Li/Li⁺, strongly depend on the structure and the applied potential range. In the range of 1.5–3.5 V, Li⁺-ions can be reversibly intercalated into the α-MoO₃ nanobelts. Utilizing the material in this way as intercalation cathode material yields an initial discharge capacity of 295 mA h g^?1 at 100 mA g^?1 and comparably moderate capacity fading of 25% between cycles 20 and 100. Extending the potential range to 0.01–3.0 V induces the conversion reaction to Mo, which for both modifications yields high initial capacities of around 1500 mA h g^?1 but is associated with much stronger capacity fading.     

&“RuNO&”6 and &“RhNO&”6 compexes with 2,2′-bipyridine and 1,10-phenanthroline

The reactions of nitrosyl halides NOX (X = Cl, Br or Br₃) and N₂O₃ with RuCl₃(H₂O)₃ and RhCl₃(H₂O)₃ in the presence of 2,2′-bipyridine and 1,10-phenanthroline results in the formation of neutral nitrosyl complexes of types Ru(NO)X₃(L-L) and Rh(NO)X₂(L-L) (L-L = 2,2′-bipyridine or 1,10-phenanthroline).     

High performance liquid chromatographic separation of <Superscript>228,229</Superscript>Th and <Superscript>232,233</Superscript>U and their estimation by α- and γ-ray spectrometry

The activities of ^228,229Th and ^232,233U from an irradiated ThO₂ sample were radiochemicaly separated by using high performance liquid chromatography. Plancheted sources of the separated samples were made and the amount of ^232,233U and ^228,229Th were estimated by using alpha and gamma-ray spectrometric techniques. These estimations are important for the Th–U fuel reprocessing cycle of advanced heavy water reactor and accelerator driven sub-critical system.     

Low solubility of unconjugated bilirubin in dimethylsulfoxide – water systems: implications for pK<Subscript><Emphasis Type="Italic">a</Emphasis></Subscript> determinations

Background

Aqueous pK _a values of unconjugated bilirubin are important determinants of its solubility and transport. Published pK _a data on an analog, mesobilirubin-XIIIα, studied by ¹³C-NMR in buffered solutions containing 27 and 64 vol% (C²H₃)₂SO because of low aqueous solubility of mesobilirubin, were extrapolated to obtain pK _a values in water of 4.2 and 4.9. Previous chloroform-water partition data on bilirubin diacid led to higher estimates of its pK _a , 8.12 and 8.44, and its aqueous solubility. A thermodynamic analysis, using this solubility and a published solubility in DMSO, suggested that the systems used to measure ¹³C-NMR shifts were highly supersaturated. This expectation was assessed by measuring the residual concentrations of bilirubin in the supernatants of comparable DMSO-buffer systems, after mild centrifugation to remove microprecipitates.

Results

Extensive sedimentation was observed from numerous systems, many of which appeared optically clear. The very low supernatant concentrations at the lowest pH values (4.1-5.9) were compatible with the above thermodynamic analysis. Extensive sedimentation and low supernatant concentrations occurred also at pH as high as 7.2.

Conclusions

The present study strongly supports the validity of the aqueous solubility of bilirubin diacid derived from partition data, and, therefore, the corresponding high pK _a values. Many of the mesobilirubin systems in the ¹³C-NMR studies were probably supersaturated, contained microsuspensions, and were not true solutions. This, and previously documented errors in pH determinations that caused serious errors in pK _a values of the many soluble reference acids and mesobilirubin, raise doubts regarding the low pK _a estimates for mesobilirubin from the ¹³C-NMR studies.

     

Sol–gel synthesis and characterization of polycrystalline GdFeO<Subscript>3</Subscript> and Gd<Subscript>3</Subscript>Fe<Subscript>5</Subscript>O<Subscript>12</Subscript> thin films

Thin films of the perovskite and garnet structured gadolinium ferrites GdFeO₃ and Gd₃Fe₅O₁₂ have been synthesized by a sol–gel method, based on stoichiometric mixtures of acetyl acetone chelated Gd³⁺ and Fe³⁺ dissolved in 2-methoxy ethanol. After spin coating onto Si wafers, and heating in air at 700 °C for 20 h, neatly grown essentially single phase films were obtained. From X-ray photoelectron spectroscopy an iron deficiency is observed in the uppermost layer of both films, implying that the crystallites preferably end in planes rich in Gd and O but not in Fe. The films were also characterized by X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, and magnetic measurements.     

A theoretical investigation on the structures and stabilities of C<Subscript>60</Subscript>X<Subscript>18</Subscript> and C<Subscript>70</Subscript>X<Subscript>10</Subscript> (X = H,F, Cl,and Br)

A density functional theory study was performed on fullerene derivatives C₆₀X₁₈ and C₇₀X₁₀ (X = H, F, Cl, and Br). The calculated results show that the lowest energy isomers are IPR-satisfying for C₆₀X₁₈ (X = H, F, Cl, and Br). It is found that the addition patterns of X (X = Cl and Br) are different from those of X (X = H and F) for C₆₀, demonstrating that the stability of fullerene derivatives is partly attributed to the steric repulsion and electronegativity of added atoms. However, the lowest energy isomers are IPR-violating for C₇₀X₁₀ (X = H, F, and Cl), suggesting that many more fullerene derivatives may violate the isolated pentagon rule.