Bifunctional Template Research Articles

Amphiphilic Polypeptides as a Bifunctional Template in the Mineralization of Calcium Carbonate at the Air/Water Interface

A well-defined amphiphilic polypeptide, poly(glutamic acid)22 -block-poly(alanine)8 (PGlu22 -b-PAla8 ), which plays the roles of both soluble (functional) additive and insoluble (structural) matrix, is employed to mediate the mineralization of CaCO3 at the air/water interface. X-ray diffraction (XRD) and Raman spectroscopy, for example, show that the polymorph of CaCO3 particles obtained is calcite. The observations from SEM and TEM suggest that PGlu22 -b-PAla8 initiates the amorphous precursor phase and heterogeneous nucleation of CaCO3 at the air/water interface, while temporarily stabilizes the gelatinous precursors as a process-directing agent; nevertheless, the initial concentration of Ca(2+) controls the procedure of crystallization and the final morphology of CaCO3 particles. Such "bifunctional" amphiphilic-polypeptide-regulated mineralization at the air/water interface may be applied to the synthesis of many kinds of symmetrical inorganic/organic hybrids.

Novel selective catalyst derived from uniform clustered NaY zeolite microspheres

The design and preparation of a new “self-protected” zeolite catalyst are reported in this paper for the first time, in order to face the challenges arising from environmental protection, in selective catalytic degrading of tobacco specific nitrosamine (TSNA) carcinogens in environmental tobacco smoke (ETS). A new method to synthesize NaY zeolite with uniform microsphere morphology via an organic amine TMAOH as bifunctional template is reported in this study. The spherical zeolite is prepared by a one-step hydrothermal crystallization without any post-treatment or other shape-directing agent. It has a rugged surface like a cluster of crystal grains and its crystallization process is monitored in detail by means of XRD and SEM. To assess how the zeolite morphology affects its catalytic performance in complex systems, this material was directly mixed with tobacco shred and added into cigarettes to in situ degrade TSNA in smoke. As a result, the clustered zeolite microsphere can avoid the interference of particulate matter in smoke and shows a high selectivity in the removal of TSNA. This synthetic method offers a novel way of preparing zeolites with a spherical morphology, which has great potential application in the fields of catalysis, adsorption and separation.

Copper containing TUD-1: synthesis, characterization and catalytic behavior in liquid-phase oxidation of ethylbenzene

Three dimensional amorphous mesoporous material, TUD-1 with different Cu-loading were prepared by using triethanolamine (TEA) as cheap, small, bi-functional template which acts as a mesoporous directing agent as well as an anchoring agent for copper active sites on the mesoporous wall. The materials thus prepared have been characterized by X-ray diffraction, N2 sorption, FT-IR, TEM, DR-UV–Vis and ICP-OES. The catalytic activities of the prepared material (CuTUD-1) were tested in liquid phase oxidation of ethylbenzene with tert-butyl hydroperoxide (TBHP) as an oxidant. Influence of various reaction parameters such as time, temperature, Si to Cu ratio, oxidant and solvent were studied. Isolated framework substituted Cu sites are active for ethylbenzene conversion (35.2%) with 67% selectivity towards acetophenone.

Design, synthesis and biological evaluation of non-peptide PAR1 thrombin receptor antagonists based on small bifunctional templates: arginine and phenylalanine side chain groups are keys for receptor activity

In the present study, we report the synthesis and biological evaluation of a series of new non-peptide PAR(1) mimetic receptor antagonists, based on conformational analysis of the S(42)FLLR(46) tethered ligand (TL) sequence of PAR(1). These compounds incorporate the key pharmacophore groups in the TL sequence, guanidyl, amino and phenyl, which are essential for triggering receptor activity. Compounds 5 and 15 (50-100 microM) inhibited both TFLLR-amide (10 microM) and thrombin-mediated (0.5 and 1 U/ml; 5 and 10 microM) calcium signaling in a cultured human HEK cell assay.

Assembly of polystyrene microspheres and its application in cell micropatterning

Cell micropatterning has important applications in the development of biosensors and lab-on-a-chip devices, tissue engineering and fundamental cell biology studies. The conventional micropatterning techniques involve patterning of cells over a planar substrate. In this paper, we propose the introduction of topographical features on cell adhesive regions to enhance cell adhesion and function. The textured surface is created by assembly of polystyrene microspheres and the topographical parameters can be varied systematically by changing the size and density of the particles. A technique of generating spatial arrangement of microspheres on a nonfouling background is developed. This is achieved by using a bi-functional template which has a patterned hydrophobic parylene film to facilitate self-assembly of particles; after assembly, the film is liftoff, revealing a cell resistance background which is compatible with cell micropatterning. Particles were assembled by selective wetting of the hydrophobic–hydrophilic template. A fluidic chamber was designed to control the movement of the particle suspension across the template so as to attain uniform particle array over large area. This method of cell micropatterning can improve the efficiency and functionality of cell-based devices. It can also be used for examining the effects of topographical cues on cell–substrate adhesion which can provide valuable insights into cell biology and design of biomaterials.

A new bifunctional template for the enzymatic synthesis of conducting polyaniline

Water soluble conducting polyaniline (PANI) is prepared using a new bifunctional template (sodium dodecyl diphenyloxide disulphonate, DODD) during the enzymatic polymerization of aniline. The bifunctional character of this new template allows an optimal environment for complex formation and polymerization, leading to PANI/DODD complexes. Electrical conductivity values of 5 × 10 −2 S/cm are obtained for PANI/DODD films, whereas water solubilities of PANI/DODD complexes are superior than previously reported ones for monofunctional templates such as dodecylbenzene sulphonic acid (DBSA). The study carried out shows that electrochemical activity and reversibility properties of PANI are not affected by the use of this new structured template.

Chromium-incorporated TUD-1 as a new visible light-sensitive photo-catalyst for selective oxidation of propane

Chromium was incorporated in the framework of TUD-1 mesoporous silica by a one-pot synthesis procedure, using triethanolamine as a bi-functional template. The Cr-TUD-1 catalyst was characterized by means of X-ray diffraction, high-resolution transmission electron microscopy, UV–vis and Raman spectroscopy, as well as elemental analysis and N 2 sorption measurements. The results indicate that chromium is incorporated as tetrahedrally co-ordinated Cr 6+ in the framework of TUD-1. When tested as a catalyst for the photo-oxidation of propane, Cr-TUD-1 showed high activity and high selectivity towards acetone under visible light irradiation ( λ = 435 nm).

Double functionalization of cholestanol directed by selective bifunctional templates

3-α-Cholestanyl esters of bipyridine acids and of iodophenylpyridine acids can direct radical chlorination to both C-9 and C-17 of the steroid, with high efficiency. The reaction is quite sensitive to reaction conditions and precise geometry.