Effect Of Trifluoroacetic Acid Research Articles

Effect of trifluoroacetic acid on the antigenicity of capsular polysaccharides obtained from various Streptococcus pneumoniae serotypes

Determining the safety, antigenicity, and immunogenicity by in vitro and in vivo studies is a prerequisite for the development of new vaccines. And this study investigated it for a vaccine made from Streptococcus pneumoniae serotypes 2, 5, 12F, 18C, and 22F. The crude CPS was purified and partially depolymerized by conventional and trifluoroacetic acid methods. 1H NMR analysis confirmed the identity of the depolymerized CPS which gave similar profiles to reference polysaccharides, except for serotype 18C which was de-O-acetylated during TFA treatment. The antigenicity of the depolymerized CPS prepared by either method was comparable to that of the native CPS for serotypes 2, 5, 18C, and 22F based on multiplex bead based competitive inhibition assay. This study demonstrated a relationship between antigenicity and immunogenicity, which offers more suitable candidates for conjugation. It was found that after partial depolymerization process, the CPS with optimal molecular size resulted in higher antigenicity. The immunogenicity of S. pneumoniae serotype 2 conjugates in mice was evaluated by opsonophagocytic assay and a multiplex bead-based assay, wherein on day 42 after immunization, the total and functional IgG titer was found to be increased by 32-fold.

Effect of trifluoroacetic acid on InP/ZnSe/ZnS quantum dots: mimicking the surface trap and their effects on the photophysical properties.

Understanding the precise effects of defects on the photophysical properties of quantum dots (QDs) is essential to their development with near-unity luminescence. Because of the complicated nature of defects in QDs, the origins and detailed roles of the defects still remain rarely understood. In this regard, we used detailed chemical analysis to investigate the effect of surface defects on the optical properties of InP/ZnSe/ZnS QDs by introducing shell defects through controlled trifluoroacetic acid (TFA) etching. TFA treatment on the InP/ZnSe/ZnS QDs partially removed the ZnS shell as well as ligands and reduced the quantum yield by generating energetically deep surface traps. The surface defects of QDs by TFA cause charged trap sites inducing an Auger recombination process with a rate of ca. 200 ps. Based on these results, we proposed possible trap-assisted non-radiative decay pathways between the band-edge state and surface deep traps in InP/ZnSe/ZnS QDs.

The Effect of Trifluoroacetic Acid on the Properties of Imidazole-Functionalized Cellulose Nanocrystalline Membranes

The Effect of Trifluoroacetic Acid on the Properties of Imidazole-Functionalized Cellulose Nanocrystalline Membranes

The Effect of Trifluoroacetic Acid on Molecular Weight Determination of Polyesters: An in Situ NMR Investigation

Due to the poor solubility of aromatic polyesters in common organic solvents, trifluoroacetic acid is usually used as a co-solvent to increase their solubility for characterizations. However, only few works have reported the side reactions induced by it. We present here the application of in-situ 1H NMR techniques to explore its effect on the hydroxyl end-groups, which are usually used for the molecular weight determination of polyesters by end-group estimation method. Using bis(2-hydroxyethyl) terephthalate (BHET) as model compound, 1H quantitative NMR results show the peak integration of hydroxyethyl end-groups decreased with time via a pseudo-first-order kinetics in d-trifluoroacetic acid/d-chloroform mixture solvent (1:10 in volume). This is due to the esterification of hydroxyethyl groups with trifluoroacetic acid, revealed by the 1H-13C gradient-enhanced heteronuclear multiple bond correlation (gHMBC) spectrum. The mixtures of dimethyl terephthalate and BHET with different molar ratio were used to represent poly(ethylene terephthalate) (PET) with different degree of polymerization, and the effect of trifluoroacetic acid on the estimation of hydroxyethyl groups and subsequent molecular weight determination of polyesters was studied. Our results show that if a relative error of 5% is allowed, the NMR measurements must be finished within 1.3 h of solution preparation at 25 C in the mixture solvent. The results were confirmed in PET sample, while in poly(ethylene adipate), the obtained esterifaction constant is faster that those in aromatic system. The results can be applied to other polymer systems with alcohol functionalized groups, and used as a guideline for the characterization of polyesters and polyethers by end-group estimation method.

The application of ion‐pair high performance countercurrent chromatography monitored by off‐line LC‐ESI‐MS/MS injections to study betalain metabolite from Vietnamese red dragon fruit (Hylocereus polyrhizus)

AbstractThe pre‐purified betalain extract from Vietnamese red dragon fruits (Hylocereus polyrhizus) was fractionated by a high performance countercurrent chromatography (HPCCC) device using the ion‐pair forming biphasic solvent of tert‐butylmethylether/n‐butanol/acetonitrile/1% aqueous trifluoroacetic acid (2:2:1:5, v/v/v/v). The J‐type HPCCC centrifuge with a 240g centrifugal force field was able to fractionate seven pigments from a 350 mg enriched crude pigment fruit extract, resulting in purified fractions for qualitative identification by LC‐ESI‐MS/MS. This approach fractionated the main betacyanin epimers namely 15R/15S‐betanin (m/z 551), 15R/15S‐phyllocactin (m/z 637), and apiosyl‐15R/15S‐betanin (m/z 683) from the solely existing betaxanthin indicaxanthin. In addition, few minor betacyanins such as 2’‐apiosyl‐15R/15S‐phyllocactin (m/z 769) were concentrated in a few fractions. That method also allowed the better detection of cacti fruit pigment 15R/15S‐hylocerenin (m/z 695), and 15R/15S‐betanidin 5‐O‐β‐sophoroside (m/z 713). However, the separation of these highly polar compounds was incomplete due to insufficient force of the ion‐pairing effect of trifluoroacetic acid (TFA).

English

A nickel vanadyl molecularly imprinted nanofiber (NVMIN) was developed by the electrospinning technique, employing polyethylene terephthalate (PET) and linear polyethylenimine (L-PEI) as the matrix polymers, nickel tetraphenylporphyrin (NTPP) and vanadyl tetraphenylporphyrin (VTPP) as the mixed-template molecules. The fabricated NVMIN was evaluated as a sorbent for the removal of NTPP and VTPP from organic media. The effects of trifluoroacetic acid (TFA), dichloromethane (DCM), dimethyl sulphoxide (DMSO), pentane (PEN) on electro-spinnability of the PET/L-PEI solutions and the morphological appearance of the PET/L-PEI fibers were investigated qualitatively by means of a scanning electron microscope (SEM). Electrospinning of 14 to 30% w/v PET/L-PEI solutions in TFA produced beaded and smooth fibers, depending on the concentration range. The addition of DCM and PEN as modifiers helped improve the electrospinnability, with PEN being the best, while the addition of DMSO made the solutions not spinnable. The results indicated that the NVMIN showed higher affinity (99% higher) for NTPP than the non-imprinted nanofiber (NIN) indicating that the NVMIN contained a lot of specific binding sites. It was determined that the NVMIN exhibited the same selectivity specialism for both NTPP and VTPP. However, the interaction strength was strongly dependant on the type of solvent, where the strongest interaction was achieved in chloroform. In addition, the thermodynamic parameters calculated from the adsorption data suggested that the adsorption of NTPP onto NVMIN was a spontaneous and exothermic process. Key words: Electrospinning, mixed-templates, adsorption, demetallation, solvents.

Effect of trifluoroacetic acid on the properties of polyvinyl alcohol and polyvinyl alcohol–cellulose composites

Highly stretchable polyvinyl alcohol (PVA) films with a strain at break of around 700% were obtained from solutions in trifluoroacetic acid (TFA). Structural and chemical analysis by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (ATR–FTIR) showed that TFA is retained by PVA via hydrogen bonds between the carboxylic acid groups and the hydroxyl groups of the polymers causing a strong plasticizing effect. Additionally, composites of PVA with cellulose could be developed using TFA as common solvent. The morphological and mechanical properties of the polymer composites could be accurately tuned by modifying the relative concentrations of the two polymers. Data from water adsorption isotherms and wetting measurements indicated that the presence of trifluoromethyl groups in PVA render the composite films relatively hydrophobic.

Hydrogen atom transfer from 1,n-alkanediamines to the cumyloxyl radical. Modulating C-H deactivation through acid-base interactions and solvent effects.

A time-resolved kinetic study on the effect of trifluoroacetic acid (TFA) on the hydrogen atom transfer (HAT) reactions from 1,n-alkanediamines (R2N(CH2)nNR2, R = H, CH3; n = 1-4), piperazine, and 1,4-dimethylpiperazine to the cumyloxyl radical (CumO(•)), has been carried out in MeCN and DMSO. Very strong deactivation of the α-C-H bonds has been observed following nitrogen protonation and the results obtained have been explained in terms of substrate basicity, of the distance between the two basic centers and of the solvent hydrogen bond acceptor ability. At [substrate] ≤ 1/2 [TFA] the substrates exist in the doubly protonated form HR2N(+)(CH2)nN(+)R2H, and no reaction with CumO(•) is observed. At 1/2 [TFA] < [substrate] ≤ [TFA], HAT occurs from the C-H bonds that are α to the nonprotonated nitrogen in R2N(CH2)nN(+)R2H. At [substrate] > [TFA], HAT occurs from the α-C-H bonds of R2N(CH2)nNR2, and the mesured kH values are very close to those obtained in the absence of TFA. Comparison between MeCN and DMSO clearly shows that in the monoprotonated diamines R2N(CH2)nN(+)R2H remote C-H deactivation can be modulated through solvent hydrogen bonding.

Вплив трифтороцтової кислоти на кластеризацію води в частково дегідратованій тканині печінки щурів з карциномою Герена

Вплив трифтороцтової кислоти на кластеризацію води в частково дегідратованій тканині печінки щурів з карциномою Герена

Cellulose 2,3-Di(p-chlorophenylcarbamate) Bonded to Silica Gel for Resolution of Enantiomers

In this study, 6-azido-2,3-di(p-chlorophenylcarbamoylated) cellulose was synthesized and bonded onto aminized silica gel to obtain a new chiral stationary phase. Enantioselectivity of the chiral stationary phase and Chiralcel OF suggested promising chiral separation ability of the new cellulose chiral stationary phase. In addition, the effect of trifluoroacetic acid, diethylamine on enantioselectivity and retention factors on the chiral stationary phase in high performance liquid chromatography was investigated. Experimental results revealed that resolution increased as the trifluoroacetic acid concentration increased to 0.3% while resolution declined as the diethylamine concentration increased. Therefore, the optimal concentrations of trifluoroacetic acid and diethylamine were determined to be 0.3 and 0.1%, respectively. In most cases, trifluoroacetic acid shortened the retention of the first eluted enantiomer while it increased the retention of the other. For acidic compounds, with the existence of diethylamine in the mobile phase, the retention of both enantiomers decreased. But for basic compounds, the retention of both enantiomers increased.

Optimization in Detecting Multiply-charged Protein Ions using MALDI TOF-MS

The effects of trifluoroacetic acid (TFA) were evaluated on the generation of multiply charged ions of cytochrome c in a 2-nitrophloroglucinol (2-NPG) matrix in high-vacuum, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The presence of 1% TFA in the 2-NPG matrix solution was more effective in generating multiply charged protein ions than matrix solutions containing 0.1% or 0% TFA. Regarding the matrix itself, with 1% TFA, 2-NPG was significantly more effective in generating multiply charged ions than 2,5-dihydroxybenzoic acid (2,5-DHB). The maximum charge state of cytochrome c was +8 when using a 2-NPG matrix containing 1% TFA.

Implementation of a design space approach for enantiomeric separations in polar organic solvent chromatography

This paper focuses on implementing a design space approach and on the critical process parameters (CPPs) to consider when applying the Quality by Design (QbD) concepts outlined in ICH Q8(R2), Q9 and Q10 to analytical method development and optimization for three chiral compounds developed as modulators of small conductance calcium-activated potassium (SK) channels. In this sense, an HPLC method using a polysaccharide-based stationary phase containing a cellulose tris (4-chloro-3-methylphenylcarbamate) chiral selector in polar organic solvent chromatography mode was considered. The effects of trifluoroacetic acid (TFA) and n-hexane concentration in an acetonitrile (MeCN) mobile phase were investigated under a wide range of column temperatures.Good correlations were found between the observed data obtained after using a central composite design and the expected chromatographic behaviours predicted by applying the design of experiments-design space (DoE-DS) methodology. The critical quality attribute represented here by the separation criterion (Scrit) allowed assessing the quality of the enantioseparation. Baseline separation for the compounds of interest in an analysis time of less than 20min was possible due to the original and powerful tools applied which facilitated an enhanced method comprehension.Finally, the advantage of the DoE-DS approach resides in granting the possibility to concurrently assess robustness and identify the optimal conditions which are compound dependent.

Effects of TFA addition on the growth of sintered YBa2Cu3Oy superconductors

Abstract The effects of trifluoroacetic acid (TFA) addition on the growth of a superconducting phase in sintered YBCO samples were investigated. YBCO samples with TFA addition were prepared by adding TFA (99.0%) to YBCO powder and then pressed into pellets and heated 1173 K – 1213 K for 12 - 20 hr in air. After the heat treatment, the TFA-added sample showed large grain sizes and highly c -axis oriented structures compared to pure YBCO samples, which indicates the enhancement of the grain growth of YBCO sintered samples by the TFA addition. The J c (0) value and J c/ J c (0T) properties of the sintered samples was improved by the TFA addition.

Separation of peptides by HPLC using a surface-confined ionic liquid stationary phase

A butylimidazolium bromide surface-confined ionic liquid stationary phase was synthesized in-house. The synthesized phase was investigated for the separation of five peptides (Gly-Tyr, Val-Tyr-Val, leucine enkephalin, methionine enkephalin, and angiotensin-II). The peptides were successfully separated in less than 5 min. The effect of trifluoroacetic acid (TFA) on the separation of peptides was evaluated with results confirming that TFA was not acting as ion-pairing agent in separation of peptides on this phase.

Enantiomer Separation of α‐Dimethyl Dicarboxylate Biphenyl and Related Biphenyl Compounds by Normal Phase HPLC on Polysaccharide Based Chiral Stationary Phases

AbstractCellulose tris(4‐methylphenylcarbamate), amylose tris(3,5‐dimethylphenylcarbamate) and amylose tris (phenylcarbamate) were prepared by the method reported by Okamoto and were coated onto an aminopropylated mesoporous spherical silica gel. These final products were used as chiral stationary phases of high performance liquid chromatography for the eighteen structurally related biphenyl compounds. The resolution was made using normal‐phase methodology with a mobile phase consisting of n‐hexane‐alcohol (ethanol, 1‐propanol, 2‐propanol or 1‐butanol). The effects of various aliphatic alcohols in the mobile phase were studied. The structural features of the solutes that influence their k′were discussed. A dominant effect of trifluoroacetic acid on chiral separation of acidic solutes was noted.

The Effect of Trifluoroacetic Acid, a Metabolite of Isoflurane on the ATP-sensitive Potassium Channel in Rabbit Ventricular Myocytes

The Effect of Trifluoroacetic Acid, a Metabolite of Isoflurane on the ATP-sensitive Potassium Channel in Rabbit Ventricular Myocytes

Structural studies of some 1-polymethyleneimino-2,4-dinitrobenzenesand related compounds; crystal structure of 1-(cis-2′,6′-dimethylpiperidin-1′-yl)-2,4-dinitrobenzene

The ultraviolet and 1H n.m.r. spectra of some 1-polymethyleneimino-2,4-dinitrobenzenes and related compounds are discussed. The effect of trifluoroacetic acid on these spectra was also investigated; with 1-azetidinyl-2,4-dinitrobenzene, acid-catalysed ring opening was observed. The solid-state conformation of 1-(cis-2′,6′-dimethylpiperidin-1′-yl)-2,4-dinitrobenzene has been defined by single-crystal X-ray crystallography. Triclinic crystals belong to the space group P–1 with a 8.165(1), b 7.865(1), c 11.148(1) Å, α 95.23(1), β 106.00(1), γ 92.63(1)˚ and Z 2. The structure was refined to a final R of 0.048 for the 2222 observed data. In the crystal, the phenyl ring adopts a slight boat conformation, while the amino and o-nitro groups are significantly twisted from the mean plane of the ring.

Study of the Effect of Mobile Phase Additives on Retention in Reversed Phase HPLC Using Linear Solvation Energy Relationships

Linear solvation energy relationships (LSERs) were used to delineate which specific intermolecular interactions are responsible for changes in retention for a variety of well characterized analytes when acidic and basic additives were used in reversed phase HPLC. The effects of trifluoroacetic acid, triethylamine and a combination of trifluoroacetic acid and triethylamine on the LSERs were compared to those observed in the absence of additives. These effects were examined using four different mobile phase modifiers and five different stationary phases. Trifluoroacetic acid alone and in combination with triethylamine produced LSER regression coefficients nearly identical to those obtained with no additive present in the mobile phase. Triethylamine alone produced different LSER regression coefficients from the other systems unless the mobile phase contained trifluoroethanol as the mobile phase modifier, or the stationary phase consisted of a polymeric support.

Effect of Fluoroacetates on Methanogenesis in Samples from Selected Methanogenic Environments

Trifluoroacetic acid (TFA) is an atmospheric decomposition product of a new generation of refrigerants that will replace current ozone-depleting CFCs. The effect of trifluoroacetic acid on microbial methanogenesis was assessed using environmental samples from four distinct methanogenic systems: the anaerobic digestor, the rumen, freshwater sediments, and marine sediments. TFA exhibited no toxcity, as evidenced by the rate of methanogenesis, at concentrations up to 10 mM. [1-14C]TFA was used to test for biodegradation (release of 14CO2) in methanogenic marine sediments. No significant release of 14CO2 was observed. As a control, the toxic monofluoroacetate (MFA), which is not an atmospheric degradation product of CFC replacements, was found to inhibit methanogenesis in freshwater and anaerobic digestor samples at or above concentrations of 0.1 mM. We conclude that TFA is inert in these methanogenic systems and there is no evident toxicity to either the methanogenic or fermentative populations.

Effects of trifluoroacetic acid, a halothane metabolite, on C6 glioma cells

Effects of trifluoroacetic acid (TFA) on cell growth, DNA, glycoprotein, and dolichol-linked oligosaccharides synthesis and ribonucleotide triphosphate concentrations were examined in exponentially growing C6 murine glioma cells. One day of treatment with TFA caused a slight concentration-dependent enhancement of cell growth and [3H]thymidine incorporation. Exposure for 1 or 5 d to TFA (0.5-7.0 mM) elevated the [3H]leucine incorporation in a dose- and time-dependent manner. The results suggested that TFA stimulated cell growth and enhanced protein synthesis. TFA also affected [3H]mannose incorporation into glycoproteins and dolichol-linked oligosaccharides in a dose-dependent fashion. In addition, it was found that TFA accelerated lectin-induced cell agglutination. These data suggest that TFA, the principle halothane metabolite, alters plasmalemmal glycoprotein synthesis. These findings should form a basis for further understanding on the mechanism underlying halothane-associated neurotoxicity.