Controlled Genetic Encoding of Unnatural Amino Acids in a Protein Nanopore

Conventional protein engineering methods for modifying protein nanopores are typically limited to 20 natural amino acids, which restrict the diversity of the nanopores in structure and function. To enrich the chemical environment inside the nanopore, we employed the genetic code expansion (GCE) technique to site-specifically incorporate the unnatural amino acid (UAA) into the sensing region of aerolysin nanopores. This approach leveraged the efficient pyrrolysine-based aminoacyl-tRNA synthetase-tRNA pair for a high yield of pore-forming protein. Both molecular dynamics (MD) simulations and single-molecule sensing experiments demonstrated that the conformation of UAA residues provided a favorable geometric orientation for the interactions of target molecules and the pore. This rationally designed chemical environment enabled the direct discrimination of multiple peptides containing hydrophobic amino acids. Our work provides a new framework for endowing nanopores with unique sensing properties that are difficult to achieve using classical protein engineering approaches.     

Synthesis, Characterization, and Evaluation of Antimicrobial Activity of Some 1,2,4-Triazole Derivatives Bearing an Antipyryl Moiety

Summary.  Some novel 4-[[2-[[5-(2-furanyl)-4-alkyl/aryl-4H-1,2,4-triazol-3-yl]thio]-acetyl/propionyl]-amino]-1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazoles were synthesized and evaluated for in vitro antibacterial activity against Staphylococcus aureus ATCC 29213, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, and Enterococcus faecalis ATCC 29212 and antifungal activity against Candida albicans ATCC 10231, Candida parapsilosis ATCC 22019, Candida krusei ATCC 6258, Candida parapsilosis, Trichophyton mentagrophytes var. erinacei NCPF 375, Microsporum gypseum NCPF 580, and Trichophyton rubrum using the microbroth dilution method. All of the compounds were found to be ineffective against the above bacteria within the applied MIC ranges. On the other hand, they were effective against fungi to different degrees. Three compounds showed high activity against C. parapsilosis and T. mentagrophytes var. erinacei NCPF 375 (MIC = 8 μg cm⁻³). The in vitro antimycobacterial activity of the new compounds was also investigated against Mycobacterium tuberculosis H₃₇RV (ATCC 27294) in BACTEC 12B medium using a broth microdilution assay, the Microplate Alamar Blue Assay (MABA). Compounds exhibiting fluorescence were tested in the BACTEC 460 radiometric system. The most active compound was found with 66% inhibition at >6.25 μg cm⁻³. Corresponding author. E-mail: nurayulusoy@yahoo.com Received July 24, 2002; accepted August 26, 2002     

Synthesis, Characterization, and Biological Activity of Amino Acid Derivatives of the Heteropolytungstophosphoric Acid

Summary. Compounds of phosphotungstic acid (WPA) containing the amino acids alanine (WPA–Ala) or glycine (WPA–Gly) as counter cations were synthesized and characterized by elemental analysis, thermal analysis, and IR spectroscopy. Cellular toxicity was assessed by the trypan blue exclusion method, and the antiviral activity of WPA and the modified WPA compounds was tested against herpes simplex viruses (HSV) type 1 and type 2. Biological assays indicate that the newly synthesized compounds exhibit no evident cytotoxic effects on Vero cells and negligible antiviral activity against HSV-1 and HSV-2.     

Investigating the Ultrafast Dynamics and Long-Term Photostability of an Isomer Pair,Usujirene and Palythene,from the Mycosporine-like Amino Acid Family

Mycosporine-like amino acids are a prevalent form of photoprotection in micro- and macro-organisms. Using a combination of natural product extraction/purification and femtosecond transient absorption spectroscopy, we studied the relaxation pathway for a common mycosporine-like amino acid pair, usujirene and its geometric isomer palythene, in the first few nanoseconds following photoexcitation. Our studies show that the electronic excited state lifetimes of these molecules persist for only a few hundred femtoseconds before the excited state population is funneled through an energetically accessible conical intersection with subsequent vibrational energy transfer to the solvent. We found that a minor portion of the isomer pair did not recover to their original state within 3 ns after photoexcitation. We investigated the long-term photostability using continuous irradiation at a single wavelength and with a solar simulator to mimic a more real-life environment; high levels of photostability were observed in both experiments. Finally, we employed computational methods to elucidate the photochemical and photophysical properties of usujirene and palythene as well as to reconcile the photoprotective mechanism.     

室温下以原位生成的醋酸咪唑鎓盐为催化剂和酰化剂用于醇、酚和胺的乙酰化反应(英文)

Acylimidazolium acetate was readily prepared in situ from the reaction of imidazole with acetic anhydride and subsequently acted as a catalyst and acylating agent for the efficient acetylation of alcohols, phenols, and amines at ambient temperature.     

Synthesis and Characterization of Some Amino Acid Derived Schiff Bases Bearing Nonionic Species as Corrosion Inhibitors for Carbon Steel in 2N HCl

A novel series of nonionic amino acid Schiff-Bases were synthesized and characterized using different spectroscopic tools to elucidate their chemical structures. The surface and thermodynamic properties of these compounds were studied using classical measurements including surface and interfacial tension and emulsification tendency. The surface parameters of these compounds including surface tension, critical micelle concentration (CMC), effectiveness (π_cmc), efficiency (Pc₂₀), maximum surface excess (Γ_max), and minimum surface area (A_min) showed their good surface activity. Their thermodynamic parameters of adsorption and micellization including free energy change of micellization and adsorption showed their tendency toward adsorption at the interfaces and also micelle formation at lower concentrations. The synthesized compounds were also evaluated as corrosion inhibitors for carbon steel at different doses (400, 200, 100, 50, and 25 ppm) in 2 N HCl using gravimetric technique (weight loss). The results showed that these inhibitors are characterized by very high corrosion inhibition efficiency ranged between 99.93% and 97.98% and low corrosion rates varied between 0.09 mpy and 0.17 mpy for higher doses (400 ppm). The efficiency of inhibition was decreased by increasing the exposure time. The most efficient corrosion inhibitor of the synthesized compounds was the inhibitor which contains polyethylene oxide chain length of 23 EO units and alkyl chain length of 12 methylene groups. The effect of the hydrophobic and hydrophilic chain length in the inhibitor molecules was discussed and rationalized with their inhibition efficiency. The tendency of these inhibitors toward complexation with the transition metals was also discussed in order to explain their higher efficiency.     

介孔硅铝分子筛的合成、表征及其作为固体酸催化苯酚与1-辛烯的烷基化反应

以异丙醇铝、硅酸四乙酯和十六烷基三甲基溴化胺为原料,以乙酰丙酮为螯合剂,采用溶胶-凝胶法合成了硅铝比分别为25,50,100和150的介孔硅铝分子筛,并用其催化苯酚与1-辛烯的液相烷基化反应.X射线衍射、N2吸附、高分辨透射电镜及27Al核磁共振光谱表征结果表明,该介孔分子筛具有蠕虫状骨架结构.在160℃时,硅铝比为25的介孔硅铝分子筛催化剂上苯酚可以完全转化为单烷基苯酚.     

Xanthan Sulfuric Acid as an Efficient Biodegradable and Recyclable Catalyst for the One‐Pot Synthesis of α‐Amino Phosphonates

A convenient and efficient procedure for the synthesis of α‐amino phosphonates by a one‐pot, three‐component condensation of aldehydes, amine, and diethyl phosphite in the presence of xanthan sulfuric acid as a bio‐supported catalyst under solvent‐free conditions has been developed. A wide range of α‐amino phosphonates have been obtained in high to excellent yields. Furthermore, the catalyst can be recovered simply and reused several times in subsequent reactions.     

Asymmetric Catalytic Aminoalkylations: New Powerful Methods for the Enantioselective Synthesis of Amino Acid Derivatives,Mannich Bases,and Homoallylic Amines

Modern methodologies such as the design of chiral catalysts using combinatorial techniques play a key role in the development of asymmetric aminoalkylations. Thus, powerful enantioselective syntheses for many attractive target compounds using chiral Lewis acid or base catalysts like 1 or 2 were created.     

Silica Supported Methanesulfonic Acid as an Efficient and Reusable Heterogeneous Catalyst for the Synthesis of Amidoalkyl Naphthols

A green protocol for the preparation of amidoalkyl naphthols from three‐component one‐pot condensation of 2‐naphthol, aldehydes, amides or urea in the presence of silica supported methanesulfonic acid under thermal solvent‐free conditions has been described. The catalyst is stable, efficient, easily prepared, and reusable. The remarkable features of this methodology are short reaction time, excellent yields, simple experimental and work‐up procedures.     

rGO-WO3 Heterostructure: Synthesis,Characterization and Utilization as an Efficient Adsorbent for the Removal of Fluoroquinolone Antibiotic Levofloxacin in an Aqueous Phase

Herein, the heterostructure rGO-WO₃ was hydrothermally synthesized and characterized by HRTEM (high-resolution transmission electron microscopy), FESEM (field emission scanning electron microscopy), XRD (X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy), XPS (X-ray photoelectron microscopy), nitrogen physisorption isotherm, Raman, TGA (thermogravimetric analysis) and zeta potential techniques. The HRTEM and FESEM images of the synthesized nanostructure revealed the successful loading of WO₃ nanorods on the surface of rGO nanosheets. The prepared heterostructure was utilized as an efficient adsorbent for the removal of a third-generation fluoroquinolone antibiotic, i.e., levofloxacin (LVX), from water. The adsorption equilibrium data were appropriately described by a Langmuir isotherm model. The prepared rGO-WO₃ heterostructure exhibited a Langmuir adsorption capacity of 73.05 mg/g. The kinetics of LVX adsorption followed a pseudo-second-order kinetic model. The adsorption of LVX onto the rGO-WO₃ heterostructure was spontaneous and exothermic in nature. Electrostatic interactions were found to have played a significant role in the adsorption of LVX onto the rGO-WO₃ heterostructure. Thus, the prepared rGO-WO₃ heterostructure is a highly promising material for the removal of emerging contaminants from aqueous solution.     

Silica Sulfuric Acid as an Efficient Reagent for the Synthesis of Symmetrical Ethers Under Mild and Heterogeneous Conditions

A mild and efficient method for the synthesis of symmetrical ethers using silica sulfuric acid is reported. All reactions are performed under compeletly heterogeneous conditions in good to high yields.     

Efficient and Convenient Protocol for the Synthesis of 3,5-Disubstituted 1,2,4-Oxadiazoles Using HClO4-SiO2 as a Heterogeneous Recyclable Catalyst

Silica-supported perchloric acid (HClO₄-SiO₂) was found to be a new, highly efficient, inexpensive, and reusable catalyst for a rapid and efficient synthesis of various 1,2,4-oxadiazoles with good to excellent yields under solvent-free conditions. The present methodology has been effectively utilized for the synthesis of oxolamine, an anti-inflammatory drug.     

Amino Acid Based Low‐Molecular‐Weight Ionogels as Efficient Dye‐Adsorbing Agents and Templates for the Synthesis of TiO2 Nanoparticles

The gelation of ionic liquids is attracting significant attention because of its large spectrum of applications across different disciplines. These ‘green solvents’ have been the solution to a number of common problems due to their eco‐friendly features. To expand their applications, the gelation of ionic liquids has been achieved by using amino acid‐based low‐molecular‐weight compounds. Variation of individual segments in the molecular skeleton of the gelators, which comprise the amino acid and the protecting groups at the N and C termini, led to an understanding of the structure–property correlation of the ionogelation process. An aromatic ring containing amino acid‐based molecules protected with a phenyl or cyclohexyl group at the N terminus were efficient in the gelation of ionic liquids. In the case of aliphatic amino acids, gelation was more prominent with a phenyl group as the N‐terminal protecting agent. The probable factors responsible for this supramolecular association of the gelators in ionic liquids have been studied with the help of field‐emission SEM, ¹H NMR, FTIR, and luminescence studies. It is the hydrophilic–lipophilic balance that needs to be optimized for a molecule to induce gelation of the green solvents. Interestingly, to maximize the benefits from using these green solvents, these ionogels have been employed as templates for the synthesis of uniform‐sized TiO₂ nanoparticles (25–30 nm). Furthermore, as a complement to their applications, ionogels serve as efficient adsorbents of both cationic and anionic dyes and were distinctly better relative to their organogel counterparts.     

Alumina Sulfuric Acid as an Efficient and Recyclable Heterogeneous Catalyst for the O-Silylation of Alcohols,Phenols, and Oximes

Alumina sulfuric acid as a recyclable catalyst conducts the transformation of various types of alcohol, phenols, and oximes with hexamethyldisilazane (HMDS) to the corresponding O-trimethylsilylated compounds in good to excellent yields under mild and ambient conditions with short reaction times. The method is highly selective for the conversion of primary alcohols in the presence of secondary and tertiary alcohols. Additionally, the catalyst can be easily recovered and reused at least eight times without detectable loss of reactivity.     

分析用标准样品氟铃脲的合成、纯化及表征

合成了氟铃脲农药粗品,通过活性炭吸附、重结晶进行初步纯化;然后采用柱层析分离技术,以硅胶为填料,乙酸乙酯／石油醚（30～60℃）（1：3,V／V）为展开剂（Rf≈0．5）进行提纯。用紫外光谱（UV）、红外光谱（IR）、核磁共振（^1H NMR,^13C NMR）及质谱（MS）进行了结构表征;以高效液相色谱法测得该试样纯度在99％以上。