Biochemical properties of genetic recombinant xylanase II

An ultraviolet (UV) coil reactor was designed and used for the online sterilization of cheese whey. Its microbial destruction efficiency was compared to that of the conventionally used UV reactor. Both reactors have the same geometry (840 ml volume and 17 mm gap size) and were tested at 11 flow rates of 5, 10, 15, 20, 25, 30, 35, 40, 50, 60, and 70 ml/min. The results obtained from this study showed that despite of its high turbidity, cheese whey could be sterilized using UV radiation if the proper reactor design and flow rate are used. The performances of the UV reactors were governed by the flow rate and the hydraulics of flow inside the reactor. The flow was laminar in both the reactors, as the Reynolds number was in the range of 1.39–20.10. The phenomenon of Dean Flow was observed in the coil reactor and the Dean number was in the range of 1.09–15.41. Dean vortices resulted in higher microbial destruction efficiency in the coil reactor in a shorter retention time. The rate of microbial destruction was found to be exponential in the conventional reactor and polynomial in the coil reactor. Increasing the flow rate from 5 ml/min to 70 ml/min decreased the microbial destruction efficiency of the conventional reactor from 99.40 to 31.58%, while the microbial destruction efficiency in the coil reactor increased from 60.77% at the flow rate of 5 ml/min to 99.98% at the flow rate of 30 ml/min and then decreased with further increases in flow rate reaching 46.2% at the flow rate of 70 ml/min. The maximum effluent temperatures in the conventional and coil reactors were 45.8 and 46.1°C, respectively. Fouling in the coil reactor was significantly less compared to the conventional reactor. The extent of fouling was influenced by flow rate and reactor’s hydraulics.     

Stable superhydrophobic polybenzoxazine surfaces over a wide pH range

In this study, we report on a simple two-step casting process designed to create a stable superhydrophobic surface. This method possesses the advantages of being both simple and inexpensive as well as utilizing non-fluorine-containing compounds. Most interestingly, we found that the as-prepared surface possesses superhydrophobic properties not only for pure water but also for corrosive water under both acidic and basic conditions. Furthermore, the superhydrophobic polybenzoxazine surfaces had excellent environmental stability with regard to both heating and organic solvent treatment in terms of the contact angle to water.     

Using swarm intelligence for finding transition states and reaction paths

We describe an algorithm that explores potential energy surfaces (PES) and finds approximate reaction paths and transition states. A few (≈6) evolving atomic configurations ("climbers") start near a local minimum M1 of the PES. The climbers seek a shallow ascent, low energy, path toward a saddle point S12, cross over to another valley of the PES, and climb down to a new minimum M2 that was not known beforehand. Climbers use both energy and energy derivatives to make individual decisions, and they use relative fitness to make team-based decisions. In sufficiently long runs, they keep exploring and may go through a sequence M1-S12-M2-S23-M3 ... of minima and saddle points without revisiting any of the critical points. We report results on eight small test systems that highlight advantages and disadvantages of the method. We also investigated the PES of Li(8), Al(7)(+), Ag(7), and Ag(2)NH(3) to illustrate potential applications of this new method.     

Highly efficient red-electrophosphorescent devices based on polyfluorene copolymers containing charge-transporting pendant units

We have systematically examined the photoluminescence (PL) and electroluminescence (EL) behavior of blends comprising two efficient red phosphors doped, respectively, into the blue-emitting polyfluorene derivatives PF-TPA-OXD and PF-OXD. The host polymers, which contain both hole- and electron-transporting or merely electron-transporting side chains, are capable of facilitating charge injection and transport. After determining the HOMO and LUMO energy levels of these materials, we were able to match the dopant with its most suitable host to achieve the direct formation and confinement of an exciton at the dopant. This configuration also leads to a reduction in the electrical excitation of the host polymer, which in turn decreases the degree of exciton loss arising from nonradiative decay of the host triplet. Using this approach, we were able to realize the production of high-performance red-electrophosphorescent devices. For Os(fppz)-doped devices, we obtain a balanced charge recombination in conjunction with higher current and luminance when using PF-TPA-OXD as the host matrix; this device reached a maximum external quantum efficiency of 8.37% with a peak brightness of 16 720 cd/m2. The absence of charge-transporting pendant units, i.e., the device fabricated from poly[9,9-dioctylfluorene-2,7-diyl] (POF), led, however, to relatively poor electroluminescence characteristics (5.81% and 2144 cd/m2).     

A rapid and simple HPLC-UV method for the determination of inhibition characteristics of farnesyl transferase inhibitors

Ras proteins play an important role in the development of cancer. Farnesyl transferase inhibitors (FTIs) block the first obligatory post-translational step for activation, prenylation, of Ras proteins. To find new potent FTIs, rapid enzyme activity assays are required to reduce FTI development time. Most assays to date are based on radioactive labelled substrates. We developed a new, in vitro, farnesyl transferase assay based on gradient chromatography coupled to UV detection. Unfarnesylated and farnesylated H-Ras proteins were resolved on a C18 wide-pore HPLC column and their concentrations were determined with use of a calibration curve of unfarnesylated H-Ras. The assay was used to investigate inhibition characteristics of FTIs. The IC50 values of the FTIs L778,123 and SCH66336 were 4.2 nm and 78 microm, respectively. This assay could support the screening and development of FTIs to obtain rapid insights into their inhibitory properties.     

First fluorescent sensor for fluoride based on 2-ureido-4[1H]-pyrimidinone quadruple hydrogen-bonded AADD supramolecular assembly

A simple, highly selective, neutral, fluorescent sensor for fluoride anions is reported. It is based on 2-ureido-4[1H]-pyrimidinone quadruple hydrogen-bonded AADD supramolecular assembly, and its assembling and disassembling processes are also able to respond to external stimuli reversibly.     

Photooxidation of olefins under oxygen in platinum(II) complex-loaded mesoporous molecular sieves

Cyclometalated platinum(II) complex has been successfully incorporated into the (3-aminopropyl) triethoxysilane-modified channels of ordered mesoporous silica SBA-15 that has large pore hexagonal channels. Studies on the (1)O(2) generation conclusively demonstrates that the olefins in the nano-channels of SBA-15 can be enriched 8 times higher than those in the homogeneous solution as the diffusion quantum yield of singlet oxygen ((1)O(2)) is assumed to be unit. The platinum(II) complex loaded in the channel of SBA-15 is stable, and the photosensitized oxidation occurs efficiently. No obvious degradation and leaching of photosensitizers is observed even after 10 runs. Only a simple filtration is needed for the recycled use of the expensive noble metal catalysts. This versatile system is a good example of photochemical reactions occurring in the mesoporous silica molecular sieve. SBA-15 not only provides a support for the photosensitizer, but also acts as a nano-reactor to facilitate the photooxidation.     

Photoinduced electron transfer in a supramolecular species building of mono-6-p-nitrobenzoyl-beta-cyclodextrin with naphthalene derivatives

Photoinduced electron transfer was observed in the supramolecular complexes of p-nitrobenzoyl-beta-cyclodextrin (NBCD) with a number of naphthalene derivatives, which were stabilized clearly via hydrophobic interactions in aqueous solution. Both steady-state and time-resolved fluorescence measurements were conducted, which revealed that there were two routes of electron transfer, i.e., electron transfer between the free donor and free acceptor in solution and electron transfer between the donor and acceptor bound in a supramolecular assembly. The evidence collected demonstrates that the latter route was very efficient. As a result, the rate and quantum yield of the fluorescence quenching in the present supramolecular system were appreciably large.     

Application of capillary electrophoresis for organic acid analysis in herbal studies

A capillary electrophoresis (CE) procedure has been developed for the separation of 25 inorganic and organic acid anions using a buffer system consisting of 15 mM tris(hydroxymethyl)aminomethane, 3 mM 1,2,4-benzenetricarboxylic acid, 1.5 mM tetraethylenepentaamine (TEPA) and 20% methanol with pH adjusted to 8.4. A good separation of organic acids extracted from a mixture of Chinese traditional medicine (TCM) containing three herbs, Flos chrysthemi, Spica prunellae, and Folium mori was obtained using the procedure developed with satisfactory working range (0.20-77 mg/g), low detection limit (90-190 microg/g), and good repeatability (relative standard deviation 4.47-6.99%, n = 4). A satisfactory extraction of organic acids was achieved within 20 min using 0.1 M NaOH. The addition of TEPA to provide a reduced electroosmotic flow (EOF) environment was shown to remove interfering organic compounds extracted from TCM. The applicability of using organic acids as markers for determining the mixing ratio of constituent herbs for a TCM mixture was investigated using a three-component mixture with a 1:1:1 mixing ratio. A satisfactory mixing ratio of 1.04:1.09:0.98 was obtained using the methodology developed based on organic acids as markers. The application of our method for determining more complicated TCM mixtures has been discussed.     

Electrostatic forces that determine O,O-trans versus O,S-cis conformers in the aminated porphyrin complexes of Cd(N-NHCO-2-C4H3O-tpp)(OAc) and Cd(N-NHCO-2-C4H3S-tpp)(OAc)

Two new diamagnetic, mononuclear and aminated porphyrin complexes of O,O-trans-Cd (3-trans) and O,S-cis-Cd (4-cis) have been synthesized and characterized by ¹H, ¹³C NMR spectroscopy. The crystal structures of (acetato)(N-2-furancarboxamido-meso-tetraphenylporphyrinato)cadmium(II) [Cd(N-NHCO-2-C₄H₃O-tpp)(OAc); 3-trans] and (acetato)(N-2-thiophenecarboxamido-meso-tetraphenylporphyrinato)cadmium(II) [Cd(N-NHCO-2-C₄H₃S-tpp)(OAc); 4-cis] were determined. The coordination sphere around Cd²⁺ is a distorted square-based pyramid in which the apical site is occupied by a bidentate chelating OAc⁻ group for 3-trans and 4-cis. The plane of three pyrrole nitrogen atoms [i.e., N(1), N(2), N(4) for 3-trans and N(1), N(2), N(3) for 4-cis] strongly bonded to Cd²⁺ is adopted as a reference plane 3N. The N(3) and N(4) pyrrole rings bearing the 2-furancarboxamido (Fr) and 2-thiophenecarboxamido groups in 3-trans and 4-cis, respectively, deviate mostly from the 3N plane, thus orienting separately with a dihedral angle of 33.4° and of 31.0°. In 3-trans, Cd²⁺ and N(5) are located on different sides at 1.06 and −1.49 Å from its 3N plane, while in 4-cis, Cd²⁺ and N(5) are also located on different sides at 1.04 and −1.53 Å from its 3N plane. An attractive electrostatic interaction between the Cd²⁺ and O(4)⁻ atoms in furan stabilizes the O,O-trans conformer of 3. A repulsive electrostatic interaction between Cd²⁺ and S(1)⁺ destabilizes the O,S-trans conformer of 4. Both of these repulsive and the mutually attractive interactions between S(1)⁺ and O(3)⁻ atoms favor the O,S-cis rotamer of 4 both in the vapor phase and in low polarity solvents. NOE difference spectroscopy, HMQC and HMBC were employed for the unambiguous assignment of the ¹H and ¹³C NMR resonances of 3-trans and 4-cis in CDCl₃ at 20 and −50 °C.