General and simple approach for control cage and cylindrical mesopores, and thermal/hydrothermal stable frameworks

Highly ordered cage and cylindrical mesoporeous silica monoliths (HOM) with 2- and 3-dimensional (2D and 3D, respectively) structures, mesopore/micropore volumes, and thick-walled frameworks were successfully fabricated by instant direct templating of lyotropic phases of copolymer (EO(m)-PO(n)-EO(m)) surfactants. Large cage-like pores with uniform constriction sizes up to 10 nm and open cylindrical channel-like mesopores can be easily achieved by this simple and efficient synthesis design. Our results show that the cage-like pores could be fabricated at relatively lower copolymer concentrations used in the lyotropic phase domains at copolymer/TMOS ratios of 35 wt %. These ordered cage pore architectures underwent transition to open-cylindrical pores by increasing the copolymer concentration. High EO/PO block copolymers, in general, were crucially affected on the increase of the interior cavity sizes and on the stability of the cage mesopore characters. However, for F108 (EO(141)PO(44)EO(141)) systems, the fabrication of ordered and stable cage pore monoliths was achieved with significantly higher copolymer concentrations up to 90 wt %. Interestingly, the effective copolymer molecular nature was also observed in the ability to design various ordered mesophase geometries in large domain sizes. Our findings here show evidence that the synthetic strategy provides realistic control over a wide range of mesostructured phase geometries and their extended long-range ordering in the final replicas of the silica monolith frameworks. In addition, the HOM silica monoliths exhibited considerable structural stability against higher thermal temperature (up to 1000 degrees C) and longer hydrothermal treatment times under boiling water and steam. The remarkable structural findings of 3D frameworks, transparent monoliths, and micropores combined with large cage- and cylindrical-like mesopores are expected to find promising uses in materials chemistry.     

Preparation, Characterization and Nonlinear Optical Properties of One-Dimensional Tetranuclear Platinum Complex/Alumina Composite Films

The preparation of transparent films consisting of one-dimensional tetranuclear platinum complex and an alumina gel was attempted. Characterization of the composite films obtained was performed by UV-Vis-NIR spectroscopy. From the redox behavior of the complex in films, it was confirmed that the complex maintains the tetranuclear structure in the alumina gel, when the content of the complex is low. However, it seems to turn into another complex with a longer platinum chain, as the content of complex in the gel increases. The third-order nonlinear susceptibility (³) values of composite films was estimated from the third harmonic generation (THG) Maker-fringe measurements of this preliminary study.     

Shape-Selective Alkylation of Isopropylnaphthalene over HM Zeolite. A Theoretical Study

A first principle quantum chemical method for determining the shape of molecules has been elaborated and its value in interpreting the experimentally found shape selectivity in isopropylation of isopropylnaphthalene on H-mordenite zeolite is demonstrated. In line with experimental results, it is found that 2,6-diisopropylnaphthalene is the most feasible product since it diffuses through the main channels of mordenite the easiest among the possible isomers.     

Enhancement in thermal stability and resistance to denaturants of lipase encapsulated in mesoporous silica with alkyltrimethylammonium (CTAB)

We assembled a highly durable conjugate with both a high-density accumulation and a regular array of lipase, by encapsulating it in mesoporous silica (FSM) with alkyltrimethylammonium (CTAB) chains on the surface. The activity for hydrolyzing esters of the lipase immobilized in mesoporous silica was linearly related to the concentration of lipase, whereas that of non-immobilized lipase showed saturation due to self-aggregation at a high concentration. The lipase conjugate also had increased resistance to heating when stayed in the silica coupling with CTAB. In addition, encapsulating the enzyme with FSM coupled CTAB caused the lipase to remain stable even in the presence of urea and trypsin, suggesting that the encapsulation prevented dissociation and denaturing. This conjugate had much higher activity and much higher stability for hydrolyzing esters when compared to the native lipase. These results show that FSM provides suitable support for the immobilization and dispersion of proteins in mesopores with disintegration of the aggregates.     

Use of zeolite to refold a disulfide-bonded protein

Zeolites are microporous crystalline aluminosilicates with a highly ordered structure. Using zeolite beta as an adsorbent, denatured/reduced hen egg lysozyme was refolded to the active form at high concentrations. The denatured/reduced lysozyme was adsorbed onto the zeolite and the protein was refolded by desorbing it into refolding buffer, consisting of redox reagents, guanidine hydrochloride, polyethylene glycol, and L-arginine. This zeolite refolding method could be highly effective for various kinds of proteins, refolding them with high efficiency even when they contain disulfide bonds.     

Coupling of Titanacyclopentadienes with a Cp Ligand and Elimination of One Substituent

Titanacyclopentadienes, prepared from [Cp₂TiBu₂] and either two equivalents of an alkyne or a diyne, were treated with PMe₃ (3 equiv) at 50 °C for 3 h and then with azobenzene at room temperature for 12 h to give 4,5,6‐trisubstituted indene derivatives with the loss of one substituent in good yields. This reaction contrasts sharply with our previously reported reaction for the formation of 4,5,6,7‐tetrasubstituted indene derivatives without the loss of substituents by the treatment of titanacyclopentadienes with azobenzene without PMe₃. ¹³C NMR spectroscopy of the product derived from a ¹³C‐enriched complex revealed that the five carbon atoms originating from a Cp ligand were arranged linearly in the trisubstituted indene derivatives, in contrast to the 4,5,6,7‐tetrasubsituted indene derivatives, in which the corresponding five carbon atoms are arranged in a ring.     

Intracellular protein labeling with prodrug-like probes using a mutant β-lactamase tag

Intracellular protein labeling with small molecular probes that do not require a washing step for the removal of excess probe is greatly desired for real-time investigation of protein dynamics in living cells. Successful labeling of proteins on the cell membrane has been performed using mutant β-lactamase tag (BL-tag) technology. In the present study, intracellular protein labeling with novel cell membrane permeable probes based on β-lactam prodrugs is described. The prodrug-based probes quickly permeated the plasma membranes of living mammalian cells, and efficiently labeled intracellular proteins at low probe concentrations. Because these cell-permeable probes were activated only inside cells, simultaneous discriminative labeling of intracellular and cell surface BL-tag fusion proteins was attained by using cell-permeable and impermeable probes. Thus, this technology enables adequate discrimination of the location of proteins labeled with the same protein tag, in conjunction with different color probes, by dual-color fluorescence. Moreover, the combination of BL-tag technology and the prodrug-based probes enabled the labeling of target proteins without requiring a washing step, owing to the efficient entry of probes into cells and the fast covalent labeling achieved with BL-tag technology after bioactivation. This prodrug-based probe design strategy for BL-tags provides a simple experimental procedure with application to cellular studies with the additional advantage of reduced stress to living cells.