Trifluoroacetic Acid Solution Research Articles

Preparation of Polyacrylic Acid/TiO<sub>2 </sub>Nanocomposites and its Application in Photodegradation of Methyl Orange

In this paper, polyacrylic acid (PAA)/TiO2 nanocomposites with photocatalytic activity were prepared via in-situ growth of anatase TiO2 nanoparticles in polyacrylic acid matrix using a simple hydrothermal method. First, water-soluble titania xerogel was prepared by a modified sol-gel procedure involving hydrolyzation of titania precursor, tetra-n-butyl titanate (TBT), in trifluoroacetic acid solution. Then, titania xerogel was dissolved in water and formed a homogeneous solution. Sequentely, polyacrylic acid as an adsorbed polymer was put into the solution and a hydrogel containing titania xerogel was obtained. After hydrothermal treatment for 10h at 100 °C, polyacrylic acid/TiO2 nanocomposites were obtained. The structure and morphology of as-prepared samples were characterized by Raman, SEM, and TEM. The photocatalytic activity of nanocomposites was evaluated by photodegradation of methyl orange under UV irradiation. The result showed that TiO2 nanocomparticles in anatase phase was in-situ generated inside PAA matrix and revealed a high photocatalytic activity, which can be used in environment purification and water treatment.

Studies of Electrospun Cellulose Acetate Nanofibrous Membranes

The objective of this work was to study the feasibility of preparing cellulose acetate (CA) nanofibrous membranes by electrospinning with single solvent and their potential applying as affinity membrane. CA solutions in dichloromethane (DCM), formic acid, acetic acid and trifluoroacetic acid (TFA) were electrospun into nonwoven fiber membranes, respectively. The scanning electron microscope (SEM) results showed that the as-spun CA nanofibers using TFA as solvent were continuous and smooth with the fiber diameter ranging from 100-300nm. Furthermore, their properties such as specific surface area, porosity and mechanical properties were investigated. The nanofibrous membranes exhibited high surface area and high porosity compared with common filter paper, which reached 2.020� 10 7 m -1 and 87%, respectively. Also, the membranes displayed a very high water permeability and a good hydrolytic stability. These characteristic properties were very effective for the separation of particles. As a result of X-ray diffraction (XRD), the obtained fibers were mainly amorphous, but characterized for good mechanical properties.

The UHPLC-DAD fingerprinting method for analysis of extracellular metabolites of fungi of the genus Geosmithia (Acomycota: Hypocreales)

A new simple ultra-high-performance liquid chromatography method with diode array detection (UHPLC-DAD) was developed for chemical fingerprinting analysis of extracellular metabolites in fermentation broth of Geosmithia spp. The SPE method employing Oasis MCX strong cation-exchange mixed-mode polymeric sorbent was chosen for extraction of the metabolites. The analyses were performed on an Acquity UPLC BEH C18 column (100 × 2.1 mm i.d.; particle size, 1.7 μm; Waters) using a gradient elution program with an aqueous solution of trifluoroacetic acid and acetonitrile as the mobile phase. The applicability of the method was proved by analysis of 38 strains produced by different species and isolated from different sources (hosts). The results revealed the correlation of obtained UHPLC-DAD fingerprints with taxonomical identity.

Imaging and Identification of Phospholipids in Mouse Liver Tissue by Matrix-Assisted Laser Desorption Ionization-Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Matrix-assisted laser desorption/ionization-fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR MS)-based mass spectrometric imaging (MSI) was applied to profile and identify phospholipid molecules in mouse liver tissues, which were cut into tissue sections (7 μm) by a cryostat at −20°C and covered with 7 g L−1 of alpha-cyano-4-hydroxycinnamic acid as matrix in 50% methanol/0.2% trifluoroacetic acid solution. 13 phospholipid compounds, which are classified as 5 different classes, phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, and phosphatidylserine, were accurately identified. Their molecular weights are between 700 and 900 Da. The results indicate that MALDI-FTICR MS-based MSI is a powerful tool to explore the distributions of disease-related molecules and drug metabolites in tissues.

One-Step Purification of Punicalagin by Preparative HPLC and Stability Study on Punicalagin

A novel, rapid, and high efficiency method to purify natural punicalagin by preparative HPLC is described. The optimum purification condition for punicalagin purification was 14% methanol in 0.1% trifluoroacetic acid solution as the mobile phase. The flow rate was 12 ml/min. 81.7 mg punicalagin at 98.05% purity was obtained from 300 mg crude extract containing 30% punicalagin. The stability of purified punicalagin was also studied. Heating, solar radiation, the pH value, and a strong oxidizer decreased its stability in water. Fe3+ and Cu2+ were complexed by punicalagin. Punicalagin was stable with ultrasonication, ultraviolet radiation, and commonly used food and cosmetic additives.

Homogeneous catalytic oxidation of light alkanes: C-C bond cleavage under mild conditions

The combined oxidation of CO and C2–C4 alkanes (associated petroleum gas and natural gas components) under the action of oxygen in trifluoroacetic acid solutions in the presence of rhodium and copper chlorides was accompanied by the oxidative degradation of C-C bonds in a hydrocarbon chain with the formation of carbonyl compounds, alcohols, and esters. For butane and isobutane, the reaction path with C-C bond cleavage was predominant. The buildup curves of isobutane oxidation products (both with the retention and with the degradation of the chain) were S-shaped and characterized by the same induction period; they did not pass through a maximum. A reaction scheme was proposed to reflect the main special features of the mechanism of transformations occurring in the O2/Rh/Cu/Cl− oxidation system.

Fundamental study of crystallization, orientation, and electrical conductivity of electrospun PET/carbon nanotube nanofibers

AbstractThe morphology, structure, and properties of polyethylene terephthalate (PET)/Carbon Nanotubes (CNT) conductive nanoweb were studied in this article. Nanocomposite nanofibers were obtained through electrospinning of PET solutions in trifluoroacetic acid (TFA)/dichloromethane (DCM) containing different concentrations and types of CNTs. Electrical conductivity measurements on nanofiber mats showed an electrical percolation threshold around 2 wt % multi‐wall carbon nanotubes (MWCNT). The morphological analysis results showed smoother nanofibers with less bead structures development when using a rotating drum collector especially at high concentrations of CNTs. From crystallographic measurements, a higher degree of crystallinity was observed with increasing CNT concentrations above electrical percolation. Spectroscopy results showed that both PET and CNT orientation increased with the level of alignment of the nanofibers when the nanotube concentration was below the electrical percolation threshold; while the orientation factor was reduced for aligned nanofibers with higher content in CNT. Considerable enhancement in mechanical properties, especially tensile modulus, was found in aligned nanofibers; at least six times higher than the modulus of random nanofibers at concentrations below percolation. The effect of alignment on the mechanical properties was less important at higher concentrations of CNTs, above the percolation threshold. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2052–2064, 2010

ChemInform Abstract: Oxidation of Ethane and Propane with Cobalt(II) Catalyst: Unexpected Formation of 1,2-Diol Esters and C-C Bond Cleavage.

Ethane reacts with both cobalt(III) and O2–cobalt(II) in trifluoroacetic acid solution to form ethyl trifluoroacetate and 1,2-bistrifluoroacetoxyethane in successive reactions, along with the products of C–C bond cleavage; propane undergoes similar oxidative reactions.

ChemInform Abstract: An Influence of a Basic Side Chain Moiety on the Tautomer Ratio Between the Enamine and Methylene Imine Forms in Azole Condensed Quinoxalines.

The reaction of 7-chloro-4-(2-cyano-2-hydroxyvinyl)tetrazolo[1,5-α]quinoxaline 2a with 4-aminopyridine, p-toluidine or p-aminophenol gave 7-chloro-4-(4-pyridylcarbamoylmethylene)-4,5-dihydrotetrazolo[1,5-α]-quinoxaline 7a, 7-chloro-4-(p-tolylcarbamoylmethylene)4, 5-dihydrotetrazolo[1,5-α]quinoxaline 8a or 7-chloro-4-(p-hydroxyphenylcarbamoylmethylene)-4,5-dihydrotetrazolo[1,5-α]quinoxaline 9a, respectively. The reaction of 7-chloro-4-(2-cyano-2-hydroxyvinyl)-1,2,4-triazolo[4,3-α]quinoxaline 2b with 4-aminopyridine, p-toluidine or p-aminophenol afforded 7-chloro4-(4-pyridylcarbamoylmethylene)-4,5-dihydro-1,2,4-triazolo-[4,3-α]quinoxaline 7b, 7-chloro-4-(p-tolylcarbamoylmethylene)-4,5-dihydro-1,2,4-triazolo[4,3-α]quinoxaline 8b or 7-chloro-4-(p-hydroxyphenylcarbamoylmethylene)-4,5-dihydro-1,2,4-triazolo[4,3-α]quinoxaline 9b, respectively. The reaction of compound 2a with 2-aminopyridine or 3-aminopyridine provided 7-chloro-4-(2-pyridyl-carbamoylmethylene)-4,5-dihydrotetrazolo[1,5-α]quinoxaline 10 or 7-chloro-4-(3-pyridyl-carbamoylmethylene)-4,5-dihydrotetrazolo[1,5-α]quinoxaline 11, respectively. Compounds 7a,b(4-pyridylcarbamoyl) predominated as the enamine tautomer A in a trifluoroacetic acid solution, while compounds 8a,b (p-tolylcarbamoyl) and compounds 9a,b (p-hydroxyphenylcarbamoyl) coexisted as the enamine A and methylene imine B tautomers in a trifluoroacetic acid solution. Moreover, the ratio of the enamine tautomer A elevated in an order of compound 11 (3-pyridylcarbamoyl), compound 10 (2-pyridylcarbamoyl) and compound 7a (4-pyridylcarbamoyl), reflecting an order of the increase in the pKa values of the aminopyridine side chain moieties. In general, the ratio of the enamine tautomer A was higher in the basic carbamoyl derivatives 7–11 than in the neutral ester derivatives 3a,b. From these results, the basic side chain moiety of the tetrazolo[1,5-α]quinoxalines 7a-11 or 1,2,4-triazolo[4,3-α]quinoxalines 7b-9b was found to increase the ratio of the enamine tautomer A in trifluoroacetic acid media.

Stability comparison between sample preparation procedures for mass spectrometry-based targeted or shotgun peptidomic analysis

The quantification of neuropeptides may play a significant role in future drug development targeting central nervous system functions. Adequate method precision and accuracy is essential, and sample stability is an important factor. This study compares three sample preparation protocols and assesses the stability of targeted neuropeptides under standard laboratory conditions. The results show that the concentrations of substance P, dynorphin A, and calcitonin gene-related peptide (CGRP) change significantly in time when spinal cord tissues are homogenized in phosphate-buffered saline (PBS) buffer or PBS buffer containing a mammalian protease inhibitor cocktail but is stabilized when tissues are homogenized in a 0.25% trifluoroacetic acid solution.

Removal of fluorions from trifluoroacetic acid by reverse osmosis

The separation characteristics of fluorions and trifluoroacetic acid (TFA) by reverse osmosis (RO) were investigated in detail. Separation results revealed that the fluorion rejection depended strongly on pH of the feed solution. The fluorion rejection could be very low by adjusting pH of the feed solution to acidic condition. Under operating pressure of 2.5 MPa, the fluorion rejection decreased sharply from 96% to 17.71% with the feed pH decreased from 6.7 to 2.75. Experimental results illustrated that RO separation can effectively remove fluorions from TFA solutions. Multi-stage RO separation can decrease the fluorion concentration to desirable level. Therefore, RO separation is an efficient and alternative method to remove fluorions from waste effluents or other fluorine compounds.

Y65C Missense Mutation in the WW Domain of the Golabi-Ito-Hall Syndrome Protein PQBP1 Affects Its Binding Activity and Deregulates Pre-mRNA Splicing

The PQBP1 (polyglutamine tract-binding protein 1) gene encodes a nuclear protein that regulates pre-mRNA splicing and transcription. Mutations in the PQBP1 gene were reported in several X chromosome-linked mental retardation disorders including Golabi-Ito-Hall syndrome. The missense mutation that causes this syndrome is unique among other PQBP1 mutations reported to date because it maps within a functional domain of PQBP1, known as the WW domain. The mutation substitutes tyrosine 65 with cysteine and is located within the conserved core of aromatic amino acids of the domain. We show here that the binding property of the Y65C-mutated WW domain and the full-length mutant protein toward its cognate proline-rich ligands was diminished. Furthermore, in Golabi-Ito-Hall-derived lymphoblasts we showed that the complex between PQBP1-Y65C and WBP11 (WW domain-binding protein 11) splicing factor was compromised. In these cells a substantial decrease in pre-mRNA splicing efficiency was detected. Our study points to the critical role of the WW domain in the function of the PQBP1 protein and provides an insight into the molecular mechanism that underlies the X chromosome-linked mental retardation entities classified globally as Renpenning syndrome.

Laser-induced Propagation and Destruction of Amyloid β Fibrils

The amyloid deposition of amyloid beta (Abeta) peptides is a critical pathological event in Alzheimer disease (AD). Preventing the formation of amyloid deposits and removing preformed fibrils in tissues are important therapeutic strategies against AD. Previously, we reported the destruction of amyloid fibrils of beta(2)-microglobulin K3 fragments by laser irradiation coupled with the binding of amyloid-specific thioflavin T. Here, we studied the effects of a laser beam on Abeta fibrils. As was the case for K3 fibrils, extensive irradiation destroyed the preformed Abeta fibrils. However, irradiation during spontaneous fibril formation resulted in only the partial destruction of growing fibrils and a subsequent explosive propagation of fibrils. The explosive propagation was caused by an increase in the number of active ends due to breakage. The results not only reveal a case of fragmentation-induced propagation of fibrils but also provide insights into therapeutic strategies for AD.

10.1007/s11498-008-1004-4

New bis(α-diketones) with thiophene and benzothiophene moieties were synthesized. A series of new polyphenylquinoxalines containing these moieties in side chains was prepared via polycondensation of these diketones with different aromatic tetramines. The polymers are soluble in a variety of organic solvents, and their solutions form transparent films having a tensile strength of σ = 80–100 MPa and an elongation at break of ɛ = 5–12%. The polymers exhibit fluorescence in solution in trifluoroacetic acid and in films with a maximum at 430–570 and 460–480 nm. The 10% mass loss temperature in air ranges within 440–490°C.

Activation of molecular oxygen in trifluoroacetic acid

The interaction of molecular oxygen with aqueous trifluoroacetic acid (TFA) led to an increase in pH. This effect was explained by a decrease in the concentration of the protonated CF3CO2H 2 + and H3O+ species after oxygen was fed in the reactor. Quantum-chemical calculations show that a radical pair can be formed in an activation-free exothermal reaction involving the radical residue of the acid, the CF3CO2H 2 + ...3O2...CF3CO 2 − peroxide radical, and the acid molecule in the CF3C 2 · ...HOO· collision complex. It was assumed that the activation of molecular oxygen in aqueous TFA solutions, providing the activity of the system in oxidations of various organic and inorganic substrates, is related to the formation of peroxide radicals in them.

An approach to on-line electrospray mass spectrometric detection of polypeptide antibiotics of enramycin for high-speed counter-current chromatographic separation

In the field of pharmaceutical and biomedical analysis of peptides, a rapid on-line detection and identification for a methodology have been required for the discovery of new biological active products. In this study, a high-speed counter-current chromatography with electrospray mass spectrometry (HSCCC/ESI-MS) was developed for the on-line detection and purification of polypeptide antibiotics of enramycin-A and -B. The analytes were purified on HSCCC model CCC-1000 (multi-layer coil planet centrifuge) with a volatile solvent of two-phase system composed of n-butanol/hexane/0.05% aqueous trifluoroacetic acid solution (43/7/50, V/V/V), and detected on an LCMS-2010EV quadrupole mass spectrometer fitted with an ESI source system in positive ionization following scan mode ( m/ z 100–2000). The HSCCC/ESI-MS peaks indicated that enramycin-A (major m/ z 786 [M+3H] 3+ and minor m/ z 1179 [M+2H] 2+) and enramycin-B (major m/ z 791 [M+3H] 3+ and minor m/ z 1185 [M+2H] 2+) have the peak resolution value of 2.9 from 15 mg of loaded enramycin powder. The HSCCC collected amounts of the peak fractions were additionally 4.3 mg (enramycin-A), and 5.9 mg (enramycin-B), respectively. These purified substances were analyzed by LC/ESI-MS with scan positive mode. Based on the LC/ESI-MS chromatograms and spectra of the fractions, enramycin-A and -B were estimated to be over 95% purity. The overall results indicate that this approach of HSCCC/ESI-MS is a powerful technique for the purification and identification of bioactive peptides.

The fabrication method of unsubstituted planar phthalocyanine thin films by a spin-coating technique

We have successfully obtained spin-coated films of unsubstituted planar phthalocyanines (free-base and copper phthalocyanine) from trifluoroacetic acid and chlorobenzene mixed solutions for the first time. The pre-annealed films did not consist of pure phthalocyanines; these films contained the solvent molecules. However, the residual solvent molecules could be removed by annealing at 425 K for 2 h in vacuum. This technique is useful for fabricating unsubstituted planar phthalocyanine thin films.

Dissolution of copper phthalocyanine and fabrication of its nano-structure film

The mono-protonated and di-protonated forms of copper phthalocyanine (CuPc) were obtained by increasing concentrations of trifluoroacetic acid (TFA) solution to a fixed concentration of CuPc solutions. UV-Vis spectrum shows that the Q bands of these two derivatives split and shift to the red, which means successive protonation happened and caused the two derivatives to lose their symmetry. After the protonation step, the solubility of protonated CuPc in organic solvent increased 60 times. The CuPc film was fabricated by the electrophoretic deposition (EPD) method from the protonated CuPc dissolved in nitromethane containing TFA. Scanning electron microscopy (SEM) showed that the deposited CuPc film on the indium tin oxide (ITO) substrate is composed of thread-like nanobelts with diameters between 100 nm and 200 nm. Furthermore, the CuPc film is in α phase with stacking direction (b-axis) parallel to the substrate, which was detected by X-ray diffraction.

Generation and properties of the 1,3-dimethyl-2,4-dioxo-1H,2H,3H,4H-pyrano[4,3-d]pyrimidinium cation in a chloroform–trifluoroacetic acid solution

The 1,3-dimethyl-2,4-dioxo-1H,2H,3H,4H-pyrano[4,3- d ]pyrimidinium cation has been prepared by means of acid-catalyzed cyclization of 1,3-dimethyl-6-(2-dimethylaminoethenyl)pyrimidine-2,4(1H,3H)-dione in a chloroform–trifluoroacetic acid solution, and its reactivity towards N-nucleophiles has been determined.

Investigation of the adsorption mechanism of a peptide in reversed phase liquid chromatography, from pH controlled and uncontrolled solutions

The single-component equilibrium adsorption of the tripeptide Leucyl-Leucyl-Leucine (LLL) on a high-efficiency Jupiter Proteo column ( C 12 ) was investigated experimentally and modeled theoretically. The experimental equilibrium isotherms of LLL for adsorption on a C 12 packing material from an aqueous solution of methanol (48%) and trifluoroacetic acid (0.1%) were measured by frontal analysis (FA). The FA measurements were done with two solutions, one in which the pH was controlled, the other in which it was not. Two solutions of LLL in the mobile phase were prepared (4.3 and 5.4 g/L) and their pH measured (2.94 and 2.88), respectively. The first solution was titrated with TFA to match the pH of the mobile phase (2.03), so its pH was controlled. The pH of the other solution was left uncontrolled. In both cases the isotherms could be modeled by a bi-Langmuir equation, a choice consistent with the bimodal affinity energy distribution (AED) obtained for LLL. The isotherm parameters derived from the inverse method (IM) of isotherm determination under controlled pH conditions (by fitting calculated profiles to experimental breakthrough profiles) are in a good agreement with those derived from the FA data. Under uncontrolled pH conditions, the application of IM suggests the coexistence of two different adsorption mechanisms. According to the isotherm parameters found by these three methods (FA, AED and IM), the C 12 -bonded silica can adsorb around 500 and 70 g/L of LLL under controlled and uncontrolled pH conditions, respectively. The adsorption of LLL on the C 12 material strongly depends on the pH of the mobile phase and on the quantity of TFA added, which plays the role of an ion-pairing agent.