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Uncontrollable growth of Zn dendrites, irreversible dissolution of cathode material and solidification of aqueous electrolyte at low temperatures severely restrict the development of aqueous Zn‐ion batteries. In this work, 2,2,2‐trifluoroethanol (TFEA) with a volume fraction of 50% as a highly compatible polar‐solvent is introduced to 1.3 M Zn(CF3SO3)2 aqueous electrolyte, achieving stable high‐performance Zn‐ion batteries. Massive theoretical calculations and characterization analysis demonstrate that TFEA weakens the tip effect of Zn anode and restrains the growth of Zn dendrites due to electrostatic adsorption and coordinate with H2O to disrupt the hydrogen bonding network in water. Furthermore, TFEA increases the wettability of the cathode and alleviates the dissolution of V2O5, thus improving the capacity of the full battery. Based on those positive effects of TFEA on Zn anode, V2O5 cathode, and aqueous electrolyte, the Zn//Zn symmetric cell delivers a long cycle‐life of 782 h at 5 mA cm−2 and 2 mA h cm−2. The full battery still declares an initial capacity of 116.78 mA h g−1, and persists 87.73% capacity in 2000 cycles at −25 °C. This work presents an effective strategy for fully compatible co‐solvent to promote the stability of Zn anode, V2O5 cathode and aqueous electrolyte for high‐performance Zn‐ion batteries. [ABSTRACT FROM AUTHOR]

Here, An efficient approach to obtaining previously unknown furo[2′,3′:2,3]pyrrolo[2,1-a]isoquinoline derivatives from readily available 1-R-1-ethynyl-2-vinylisoquinolines is described. The reaction features a simple procedure, occurs in hexaflouroisopropanol and does not require elevated temperatures. It has been found that the addition of glacial acetic acid significantly increases the yields of the target spirolactone products. Using trifluoroethanol instead of hexaflouroisopropanol results in the formation of pyrido[2,1-a]isoquinolines. [ABSTRACT FROM AUTHOR]

The cosolvent 2,2,2‐trifluoroethanol (TFE) is often used to mimic protein desiccation. We assessed the effects of TFE on cytosolic abundant heat soluble protein D (CAHS D) from tardigrades. CAHS D is a member of a unique protein class that is necessary and sufficient for tardigrades to survive desiccation. We find that the response of CAHS D to TFE depends on the concentration of both species. Dilute CAHS D remains soluble and, like most proteins exposed to TFE, gains α‐helix. More concentrated solutions of CAHS D in TFE accumulate β‐sheet, driving both gel formation and aggregation. At even higher TFE and CAHS D concentrations, samples phase separate without aggregation or increases in helix. Our observations show the importance of considering protein concentration when using TFE. [ABSTRACT FROM AUTHOR]

Membrane proteins are one of the keystone objects in molecular biology, but their structural studies often require an extensive search for an appropriate membrane-like environment and an efficient refolding protocol for a recombinant protein. Isotropic bicelles are a convenient membrane mimetic used in structural studies of membrane proteins. Helical membrane domains are often transferred into bicelles from trifluoroethanol–water mixtures. However, the protocols for such a refolding are empirical and the process itself is still not understood in detail. In search of the optimal refolding approaches for helical membrane proteins, we studied here how membrane proteins, lipids, and detergents interact with each other at various trifluoroethanol–water ratios. Using high-resolution NMR spectroscopy and dynamic light scattering, we determined the key states of the listed compounds in the trifluoroethanol/water mixture, found the factors that could be critical for the efficiency of refolding, and proposed several most optimal protocols. These protocols were developed on the transmembrane domain of neurotrophin receptor TrkA and tested on two model helical membrane domains—transmembrane of Toll-like receptor TLR9 and voltage-sensing domain of a potassium channel KvAP. [ABSTRACT FROM AUTHOR]

Thermo-reversible gel of myofibrillar protein (MP) can be made by tactics of elaborate deamidation using protein-glutaminase (PG), and this work aimed to disclose the link between thermally reversible gelation of MP and the coiled-coil (CC). Enzymatic deamidation fragmented myofibril filaments and triggered structural reassembly to create small-sized aggregates. The coiling and dissociation of CC structure in the myosin tails is the fundamental structural basis of the PG deamidated MP (DMP) in the dynamic evolution of reversible gelation. After specific inhibition of CC assembly by trifluoroethanol (TFE), the thermo-reversible gel ability of DMP was impaired, which confirmed that the dynamic assembly of CC with temperature response played a key role in the thermo-reversible gelation of DMP. The findings may broaden the molecular basis of natural CC reversible gelation and foster advances for the development of new muscle protein products.

Alpha-Synuclein is a presynaptic neuronal protein whose masses are involved in Parkinson's disease, a chronic and progressive neurodegenerative disorder of the central nervous system. It has been observed that upon exposure to anionic surfactants, fluorinated alcohols and membranes in vitro, α -synuclein adopts alpha helix structure and can be fibrillated, while in aqueous solution, the protein is intrinsically disordered and the fibrillation is undesirable. Solvent is one of the most critical environmental parameters in biological studies as well as computer simulations. In this paper, we have investigated the effect of solvent composition on the conformation of α -synuclein protein using molecular dynamics (MD) simulations. For this purpose, the effect of different combinations of water and trifluoroethanol (TFE) solvents on the secondary structure of a fragment of α -synuclein was investigated. Moreover, thermodynamic calculations were performed through a coarse-grained (CG) model of solutions with different concentrations of α -synuclein in the aqueous phase and in TFE medium. The potential of mean force (PMF) calculations was performed as a function of separation distance between the centers of masses of two peptides. The results indicated that in the presence of TFE, the secondary structures have a regular arrangement of amino acids stabilized by hydrogen bonding patterns. In addition, decreasing the TFE concentration reduces the stability of α -helix structures of the protein. It seems that in diluted TFE solutions, high concentrations of water in the medium lead to the breakage of peptide–TFE hydrogen bonds. However, the hydrophobic nature of TFE and α -synuclein molecules prevents further aggregation in the concentrated solutions. The α-synuclein can be fibrillated in the presence of Trifluoroethanol (TFE). Stability of α-helix structure of peptide reduces as TFE concentration decreases. Hydrophobic nature of TFE and α-synuclein molecules prevents further aggregation. [ABSTRACT FROM AUTHOR]

An approach based on experimental and theoretical methods was used to compare the self‐assembly [i.e., determination of the critical micelle concentration (CMC), degree of ionization (α) and counterion binding (β)] of sodium dodecyl sulfate (SDS) and didodecyl dimethyl ammonium bromide (DDAB) in deionized water and 10 mM NaCl and 10 (vol) % trifluoroethanol solutions. Experimental methods consisted of electrical conductometry, tensiometry, fluorimetry, and determination of Krafft temperature. A critical analysis of the thermodynamics of self‐assembly by the Gibbs–Helmholtz equation and the van't‐Hoff rationale provided values of several parameters, such as the change of Gibbs free energy and enthalpy change of micellization (ΔGm0 and ΔHm0, respectively) and the Gibbs free energy of surfactant tail groups (∆G0trans). Interfacial properties, aggregation number (Nagg), micropolarity (I1/I3), microviscosity (η), packing parameter (P), dielectric constant (D), anisotropy (r), and Stern–Volmer binding constant (KSV) for SDS and DDAB in different temperatures and different systems were determined. [ABSTRACT FROM AUTHOR]

An efficient decarboxylative addition reaction of β‐ketoacids with miscellaneous electrophiles in 2,2,2‐trifluoroethanol (TFE) is reported. The reaction proceeds smoothly without any base and metal catalysts, affording a broad range of diarylmethanes, β‐hydroxy ketones and 3,3‐disubstituted oxindoles with moderate to excellent yields under essentially neutral conditions. [ABSTRACT FROM AUTHOR]

A facile sol-gel method was proposed to prepare fluorine-containing hydrophobic SiO2 coating using trifluoroethanol (TFE) as the dispersant and hydrophobic modifier simultaneously. FTIR and XPS analysis indicated that CF3 groups were incorporated onto the surface of SiO2 particles. The resultant SiO2 coating possessed excellent hydrophobicity with a water contact angle (WCA) of 145°. This provides a new method for the preparation of fluorine-containing sol-gel SiO2 coating without the expensive long-chain alkyl fluorosilane.

Lactams are essential compounds in medicinal chemistry and key intermediates in the synthesis of natural products. The Castagnoli–Cushman reaction (CCR) of homophthalic anhydride with imines is an exciting method for accessing cyclic densely substituted lactam products. Most CCRs need to be catalyzed or heated. Herein, we report a new, efficient, metal and catalyst-free CCR for the synthesis of poly-substituted 3,4-lactams utilizing the unique properties of trifluoroethanol (TFE). This procedure provides high-speed and smooth access to a broad range of densely substituted 3,4-lactams in good yields and a 100% atom-economical fashion.

The ability of antibodies to switch between specific and nonspecific recognition of antigens under various factors is the key issue. Here we demonstrate that 2,2,2-trifluoroethanol (TFE) is one of these factors influencing the ability of monoclonal antibodies to react specifically with corresponding antigen (ovalbumin) and transforming them into polyreactive immunoglobulins (PRIGs) that are strong but nonspecific binders with various antigens. Such switching of antibody reactivity is nonlinear and even nonmonotonous function of TFE concentration and depends strongly on incubation time and temperature. At room temperatures (25 °C) the specific antibodies under 30% TFE action are transformed into PRIGs. However, at 0 °C the variation of antibody reactivity is complicated. TFE is known as the alcohol with one of the strongest proton-donor abilities in hydrogen bonding and its effect is probably in binding to specific sites that switch the antibody recognition ability.

Fluorinated alcohols have been widely used in the synthetic organic chemistry over the past decades. The unique properties such as the strong hydrogen‐bonding donor ability and low nucleophilicity allow them to promote organic reactions in the absence of any catalyst. These approaches have distinct advantages in terms of operational simplicity, practicability and environmental friendliness. Reactions promoted by fluorinated alcohols, including nucleophilic substitution reactions, annulation reactions, electrophilic reactions, dearomatization reactions, functionalization of multiple bond, epoxidation reactions and miscellaneous reactions have been summarized in this account. [ABSTRACT FROM AUTHOR]

Abstract Steady state and time resolved spectral properties of 7,8-benzoquinoline (7,8-BQ) have been reinvestigated in a series of organic solvents of different proticity, polarity and wide range of pH. The salient features of this work are the effect of hydrogen bonding in protonation reaction which is explored through its behaviour in water and strong hydrogen bond donating solvent (trifluoroethanol). Quantum yield and rates (radiative, non-radiative and excited state protonation) have been calculated and discussed. Irreversible diffusion controlled excited state proton transfer in water and faster excited state protonation in trifluoroethanol is observed. Graphical abstract Graphical abstract indicating protonation of 7,8-BQ in water. Image 1017 Highlights • Steady state and time resolved properties of 7,8-benzoquinoline are reinvestigated. • Depending on media and pH, neutral and protonated species are present in the ground and excited states. • Irreversible diffusion controlled excited state proton transfer is observed in water. • Much faster excited state protonation is observed in trifluoroethanol. • Results indicate evidence of promoting of protonation by hydrogen bonding. [ABSTRACT FROM AUTHOR]

The synthesis of a molecularly diverse library of tetrasubstituted alkenes containing a barbiturate motif is described. Base-induced condensation of N1-substituted pyrimidine-2,4,6(1H,3H,5H)-triones with 5-(bis(methylthio)methylene)-2,2-dimethyl-1,3-dioxane-4,6-dione gave 3-substituted 5-(methylthio)-2H-pyrano[2,3-d]pyrimidine-2,4,7(1H,3H)-triones (‘pyranopyrimidinones’), regioselectively. A sequence of reactions involving ring-opening of the pyran moiety, displacement of the methylthio group with an amine, re-formation of the pyran ring, and after its final cleavage with an amine, gave tetrasubstituted alkenes (3-amino-3-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)propanamides) with a diversity of substituents. Cleavage of the pyranopyrimidinones with an aniline was facilitated in 2,2,2-trifluoroethanol under microwave irradiation. Compounds were tested against Escherichia coli, Staphylococcus aureus, the yeast Schizosaccharomyces pombe, and the pathogenic fungus Candida albicans. No compounds exhibited activity against E. coli, whilst one compound was weakly active against S. aureus. Three compounds were strongly active against S. pombe, but none was active against C. albicans.

An angular displacement-enhanced heterodyne polarimeter has been employed to investigate the interplay between trifluoroethanol (TFE) and glycerol on the thermal denaturation of type I collagen. The concentration of the collagen solution was fixed at 0.341 (mg/mL), and was heated from 25 °C to 55 °C. TFE solutions with concentrations of 5%, 10%, 15%, 20%, 40% and 80% (v/v) were prepared and the phase change was recorded for the determination of thermal denaturation. It was observed that the thermal denaturation temperature (Td) is decreased with increasing TFE concentration due to the partial cleavage of the triple-helical structure. With TFE concentration higher than 20% (v/v), the degree of optical rotation appears to be nearly the same, reflecting that the collagen triple helices have been completely destructed. Moreover, the addition of glycerol in inhibiting the thermal denaturation of collagen is investigated. It has been shown that glycerol can improve the thermal denaturation of both collagen and TFE-mixed collagen. Experimental results show that, in the presence of 2 M glycerol, the Td of collagen remained at around 41.9 °C, meanwhile the Td of 20% (v/v) TFE-mixed collagen is significantly restored to 32.8 °C.

Thermo-reversible gel of myofibrillar protein (MP) can be made by tactics of elaborate deamidation using protein-glutaminase (PG), and this work aimed to disclose the link between thermally reversible gelation of MP and the coiled-coil (CC). Enzymatic deamidation fragmented myofibril filaments and triggered structural reassembly to create small-sized aggregates. The coiling and dissociation of CC structure in the myosin tails is the fundamental structural basis of the PG deamidated MP (DMP) in the dynamic evolution of reversible gelation. After specific inhibition of CC assembly by trifluoroethanol (TFE), the thermo-reversible gel ability of DMP was impaired, which confirmed that the dynamic assembly of CC with temperature response played a key role in the thermo-reversible gelation of DMP. The findings may broaden the molecular basis of natural CC reversible gelation and foster advances for the development of new muscle protein products., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

A novel protocol is reported for the N-formylation of amines with formic acid by using the nanoporous zeolitic imidazolate framework ZIF-8 as a heterogeneous catalyst in 2,2,2-trifluoroethanol. [ABSTRACT FROM AUTHOR]

The aza-Michael addition of functionally substituted anilines to enoates is significantly affected by the hydrogen bond donor ability of the solvent. Very polar protic fluorinated alcohols (hexafluoroisopropanol and trifluoroethanol) favor the addition of weak nucleophiles, whereas these solvents are no longer required for anilines bearing additional OH or NH 2 group. [ABSTRACT FROM AUTHOR]

An efficient and versatile mechanochemical route for the synthesis of chromene and isoindolo[2,1-a]quinazoline scaffolds has been developed via a simple mortar and pestle liquid-assisted grinding method using 2,2,2-trifluoroethanol (TFE) as an efficient catalyst. The present protocol is very efficient as it offers reaction in mild reaction condition, cleaner reaction profiles, effortless work-up step with excellent purity, and high yield of the desired products with short reaction time. [ABSTRACT FROM AUTHOR]

Abstract: Alterations in the local dynamics of Cu/Zn Superoxide dismutase (SOD1) due to mutations affect the protein folding, stability, and function leading to misfolding and aggregation seen in amyotrophic lateral sclerosis (ALS). Here, we study the structure and dynamics of the most devastating ALS mutation, A4V SOD1 in aqueous trifluoroethanol (TFE) through experiments and simulation. Far‐UV circular dichroism (CD) studies shows that TFE at intermediate concentrations (∼15% ‐ 30%) induce partially unfolded β‐sheet‐rich extended conformations in A4V SOD1 which subsequently aggregates. Molecular dynamics (MD) simulation results shows that A4V SOD1 increases local dynamics in the active site loops that leads to the destabilization of the β‐barrel and loss of hydrophobic contacts, thus stipulating a basis for aggregation. Free energy landscape (FEL) and essential dynamics (ED) analysis demonstrates the conformational heterogeneity in A4V SOD1. Our results thus shed light on the role of local unfolding and conformational dynamics in aggregation of SOD1. [ABSTRACT FROM AUTHOR]

Cold-regulated (COR) 15A is an intrinsically disordered protein (IDP) from Arabidopsis thaliana important for freezing tolerance. During freezing-induced cellular dehydration, COR15A transitions from a disordered to mostly α-helical structure. We tested whether mutations that increase the helicity of COR15A also increase its protective function. Conserved glycine residues were identified and mutated to alanine. Nuclear magnetic resonance (NMR) spectroscopy was used to identify residue-specific changes in helicity for wildtype (WT) COR15A and the mutants. Circular dichroism (CD) spectroscopy was used to monitor the coil–helix transition in response to increasing concentrations of trifluoroethanol (TFE) and ethylene glycol. The impact of the COR15A mutants on the stability of model membranes during a freeze–thaw cycle was investigated by fluorescence spectroscopy. The results of these experiments showed the mutants had a higher content of α-helical structure and the increased α-helicity improved membrane stabilization during freezing. Comparison of the TFE- and ethylene glycol-induced coil–helix transitions support our conclusion that increasing the transient helicity of COR15A in aqueous solution increases its ability to stabilize membranes during freezing. Altogether, our results suggest the conserved glycine residues are important for maintaining the disordered structure of COR15A but are also compatible with the formation of α-helical structure during freezing induced dehydration.

Asymmetric alkylation is one of the most useful carbon–carbon bond-forming reactions in synthetic organic chemistry. Chiral-amine-catalyzed alkylation reactions often lack regioselectivity owing to multiple reactive centers. In particular, the alkylation of linear 2-enals through dienamine catalysis produces a mixture of regioisomers owing to reactive α- and γ-positions. A few attempts have been made to mask the α-reactive center to achieve γ-selectivity. Controlling the enantioselectivity at the remote γ-position has also been found to be quite challenging. Herein, we achieved the highly regioselective γ-alkylation of linear α, β-unsaturated aldehydes by using trifluoroethanol (TFE) as a cosolvent. Further, we demonstrated in situ kinetic resolution for enantioenrichment of the γ-alkylated products. This method brings together the activation of an electrophile facilitated by TFE and in situ kinetic resolution to achieve excellent selectivity in dienamine catalysis. [ABSTRACT FROM AUTHOR]

Glucoamylase (EC 3.2.1.3) from Aspergillus niger possesses 31% α-helix, 36% β structure and rest aperiodic structure. A transition of glucoamylase structure in the presence of varying concentrations of glyoxal (GO) and trifluoroethanol (TFE) was studied by using multi-methodological approaches. At 20% GO, glucoamylase exists as molten globule state as evident by high tryptophan and ANS fluorescence, retention of secondary structure and loss of native tertiary structure. This state precedes the onset of the aggregation process and maximum is achieved at the highest concentration i.e . at 90% of GO. In parallel study TFE, on increasing concentration up to 25% induces secondary structure transformation leading to accumulation of intermolecular β sheets, altered tryptophan environment, high ANS and ThT fluorescence resulting in the formation of glucoamylase aggregates. Isothermal titration calorimetric curve is sigmoidal, indicating the weak binding of GO/TFE and glucoamylase. TEM studies showed that glucoamylase exists as globular and amorphous aggregates at 90% glyoxal and 25% TFE respectively. Further, TFE at 70% causes inhibition of enzyme aggregates; the majority of secondary structures observed at this concentration are α helices. Alpha helices being the main key player relocates glucoamylase native environment as evident by CD, FTIR and TEM. Hence induction of β sheet promotes protein aggregation and α helices inhibits protein aggregation. [ABSTRACT FROM AUTHOR]

It is shown that C4(S)-NH2 /OH/NHCHO-prolyl polypeptides exhibit PPII conformation in aqueous medium, but in a relatively hydrophobic solvent trifluoroethanol (TFE) transform into an unusual β-structure. The stereospecific directing effect of H-bonding in defining the specific structure is demonstrated by the absence of β-structure in the corresponding C4(S)-guanidinyl/(NH/O)-acetyl derivatives and retention of β-structure in C4(S)-(NHCHO)-prolyl polypeptides in TFE. The distinct conformations are identified by the characteristic CD patterns and supported by Raman spectroscopic data. The solvent dependent conformational effects are interpreted in terms of intraresidue H-bonding that promotes PPII conformation in water, switching over to interchain H-bonding in TFE. The present observations add a new design principle to the growing repertoire of strategies for engineering peptide secondary structural motifs for innovative nanoassemblies and new biomaterials. [ABSTRACT FROM AUTHOR]

[Display omitted] An efficient and green synthesis protocol has been developed for construction of triarylmethane scaffold using trifluoroethanol as a recyclable solvent. Significantly, recyclable solvent and product could be separated by filtration. The expected product could be afforded in good to excellent yield under standard conditions. Meanwhile, recyclable trifluoroethanol solvent could be reused directly for a new reaction. Furthermore, trifluoroethanol could be recovered through distillation with excellent yield, which can be used for other reaction. [ABSTRACT FROM AUTHOR]

• The indirect introduction of perfluoroalkyl groups into allene benzazecines has been developed. • The cytotoxic activity of perfluoroalkyl substituted compounds has been evaluated. • The reaction mechanistic features have been refined. New approach for the introduction of a perfluoroalkynyl fragment into 1-R2–2-methyl-1,2,3,4-tetrahydroisoquinolines has been developed. Synthesized 1,1-disubstituted isoquinoline compounds under the action of methyl propiolate (24 °C) and acetylacetylene (-17 °C) in trifluoroethanol are converted into 6-perfluoroalkyl substituted allene benzazecines. The synthesized isoquinoline derivatives 2 , and benzazecines 3 – 4 were evaluated against four cancer cell lines. The results revealed that compound 2h (R2 = C 6 H 4 - p -OMe; R F = CF(CF 3) 2) displayed good cytotoxic effects on four tested cell lines with IC 50 values ranging from 5 to 50 μM. To create your abstract, type over the instructions in the template box below. Fonts or abstract dimensions should not be changed or altered. [Display omitted] [ABSTRACT FROM AUTHOR]

Revised descriptors are determined for fifteen phthalate esters for use in the solvation parameter model and form part of the Wayne State University (WSU) compound descriptor database. For thirteen phthalate esters a comparison is made with the same compounds in the Abraham descriptor database. Gas chromatographic retention factors on poly(methyloctylsiloxane), SPB-Octyl, and poly(cyanopropylphenyldimethylsiloxane), DB-225, stationary phases are used to facilitate an assessment of the contribution of cavity formation and dispersion interactions, L descriptor, and dipole-type interactions, S descriptor, to the experimental retention factors (log k) for the phthalate esters with minimum interference from competing intermolecular interactions. The results indicate a systematic overprediction of the cavity and dispersion interaction term and underprediction of dipole-type interactions for the Abraham descriptors compared with the WSU descriptors for the phthalate esters. The average absolute deviation (AAD) for 13 phthalate esters on SPB-Octyl is 0.039 (WSU descriptors) compared with 0.252 (Abraham descriptors) and for 9 phthalate esters on DB-225 0.030 (WSU descriptors) compared with 0.167 (Abraham descriptors). The results for dipole-type interactions are confirmed and extended to include the hydrogen-bond basicity of the phthalate esters, B descriptor, by evaluation of partition constants in aqueous biphasic systems and the n-heptane-2,2,2-trifluoroethanol biphasic system. Differences in the contribution of the hydrogen-bond basicity of the phthalate esters to the experimental partition constants are largely random with respect to database selection but important for the accurate prediction of the partition constants. The AAD for the partition constant for 15 phthalate esters is 0.063 (WSU descriptors) compared with 0.320 (Abraham descriptors) for the heptane-2,2,2-trifluoroethanol biphasic system and 0.13 (WSU descriptors) compared with 0.25 (Abraham descriptors) for 9 phthalate esters in the octanol-water biphasic system. The WSU descriptors for the phthalate esters exhibit a better fit with the experimental data for separation systems and are free of the extreme values predicted for the Abraham descriptors for several phthalate esters., Competing Interests: Declaration of Competing Interest The author declares that he has no conflicts of interest in connection with this study., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The cosolvent 2,2,2-trifluoroethanol (TFE) is often used to mimic protein desiccation. We assessed the effects of TFE on cytosolic abundant heat soluble protein D (CAHS D) from tardigrades. CAHS D is a member of a unique protein class that is necessary and sufficient for tardigrades to survive desiccation. We find that the response of CAHS D to TFE depends on the concentration of both species. Dilute CAHS D remains soluble and, like most proteins exposed to TFE, gains α-helix. More concentrated solutions of CAHS D in TFE accumulate β-sheet, driving both gel formation and aggregation. At even higher TFE and CAHS D concentrations, samples phase separate without aggregation or increases in helix. Our observations show the importance of considering protein concentration when using TFE., (© 2023 The Protein Society.)

Although rarely used in nature, fluorine has emerged as an important elemental ingredient in the design of proteins with altered folding, stability, oligomerization propensities, and bioactivity. Adding to the molecular modification toolbox, here we report the ability of privileged perfluorinated amphiphiles to noncovalently decorate proteins to alter their conformational plasticity and potentiate their dispersion into fluorous phases. Employing a complementary suite of biophysical, in-silico and in-vitro approaches, we establish structure-activity relationships defining these phenomena and investigate their impact on protein structural dynamics and intracellular trafficking. Notably, we show that the lead compound, perfluorononanoic acid, is 10 6 times more potent in inducing non-native protein secondary structure in select proteins than is the well-known helix inducer trifluoroethanol, and also significantly enhances the cellular uptake of complexed proteins. These findings could advance the rational design of fluorinated proteins, inform on potential modes of toxicity for perfluoroalkyl substances, and guide the development of fluorine-modified biologics with desirable functional properties for drug discovery and delivery applications., (© 2023 The Authors. ChemBioChem published by Wiley-VCH GmbH.)

The facile synthesis of 4-acetyl-2-hydroxy-2,5-dimethylfuran-3(2H)-one (4) was achieved by the Mn(OAc)3-mediated aerobic oxidation of 2,4-pentanedione or the direct reaction of Mn(acac)3 in AcOH-TFE at room temperature under a dried air stream.

This article describes one-pot synthesis of new fluorinated hexahydroquinoline derivatives via unsymmetric Hantzsch reaction involving 5-trifluoromethyl-1,3-cyclohexanedione, aldehydes, acetoacetate ester, and ammonium acetate in trifluoroethanol (TFE). The reaction is simple and rapid with high yield.

The facile synthesis of 4-acetyl-2-hydroxy-2,5-dimethylfuran-3(2H)-one (4) was achieved by the Mn(OAc)3-mediated aerobic oxidation of 2,4-pentanedione or the direct reaction of Mn(acac)3 in AcOH-TFE at room temperature under a dried air stream. [ABSTRACT FROM AUTHOR]

Fib having intrinsically disordered αC domains is involved in coagulation cascade and thrombosis. Fib molecules forms prefibrillar oligomers at 30%, and associate in 40 and 50% TFE to proceed α to β transition, suggesting the formation of an intermolecular β-structure. AFM images confirmed the nature of Fib aggregates at 40 and 50% TFE to be prefibrillar and fibrillar respectively. These aggregates possess high thioflavin T fluorescence with a shifted Congo red absorbance. Kinetics of Fib aggregation data at 50% TFE supports nucleation-dependent polymerization mechanism. At 60 and 70% TFE, no aggregation was observed. The inhibition of protein aggregation appears due to weakening of the hydrophobic interactions that were initially stabilizing the intermolecular β-sheet structure in the protein aggregation. The loss of hydrophobic contacts seems to favor the formation of intramolecular hydrogen bonds over intermolecular hydrogen bonds leading to helix formation. To conclude, protein aggregation is accompanied by the formation of β-sheet conformation, and induction of non-native helical segments in the protein inhibits aggregation. The discrepancy of the secondary structures on aggregation is proposed to stem from the disparity in the nature of the hydrogen bonds and packing of hydrophobic residues of the side chains in the β-sheet and α-helix conformation. [ABSTRACT FROM AUTHOR]

Background: Formation of inclusion bodies poses a major hurdle in recovery of bioactive recombinant protein from Escherichia coli. Urea and guanidine hydrochloride have routinely been used to solubilize inclusion body proteins, but many times result in poor recovery of bioactive protein. High pH buffers, detergents and organic solvents like n-propanol have been successfully used as mild solubilization agents for high throughput recovery of bioactive protein from bacterial inclusion bodies. These mild solubilization agents preserve native-like secondary structures of proteins in inclusion body aggregates and result in improved recovery of bioactive protein as compared to conventional solubilization agents. Here we demonstrate solubilization of human growth hormone inclusion body aggregates using 30 % trifluoroethanol in presence of 3 M urea and its refolding into bioactive form. Results: Human growth hormone was expressed in E. coli M15 (pREP) cells in the form of inclusion bodies. Different concentrations of trifluoroethanol with or without addition of low concentration (3 M) of urea were used for solubilization of inclusion body aggregates. Thirty percent trifluoroethanol in combination with 3 M urea was found to be suitable for efficient solubilization of human growth hormone inclusion bodies. Solubilized protein was refolded by dilution and purified by anion exchange and size exclusion chromatography. Purified protein was analyzed for secondary and tertiary structure using different spectroscopic tools and was found to be bioactive by cell proliferation assay. To understand the mechanism of action of trifluoroethanol, secondary and tertiary structure of human growth hormone in trifluoroethanol was compared to that in presence of other denaturants like urea and guanidine hydrochloride. Trifluoroethanol was found to be stabilizing the secondary structure and destabilizing the tertiary structure of protein. Finally, it was observed that trifluoroethanol can be used to solubilize inclusion bodies of a number of proteins. Conclusions: Trifluoroethanol was found to be a suitable mild solubilization agent for bacterial inclusion bodies. Fully functional, bioactive human growth hormone was recovered in high yield from inclusion bodies using trifluoroethanol based solubilization buffer. It was also observed that trifluoroethanol has potential to solubilize inclusion bodies of different proteins. [ABSTRACT FROM AUTHOR]

We describe herein a new method for cleaving from resin and removing acid-labile protecting groups in solid-phase peptide synthesis in the presence of a polyfluorinated alcohol (either trifluoroethanol, TFE, or hexafluoroisopropanol, HFIP). It was shown that 0.1 M HCl in hexafluoroisopropanol or trifluoroethanol removes the acid-labile protecting groups commonly used in Fmoc SPPS for the protection of amino acid side-chains, such as t-butyl ester and ether, Boc, trityl, and Pbf groups including the most acid-resistant p-hydroxymethylphenoxyacetyl group (HMPA), p-benzyloxy benzyl ester (Wang resin), Rink amide, and peptide amide linker (PAL). The addition of 5-10% of a hydrogen-bonding solvent was shown to considerably retard or even fully inhibit the reaction. However, nonhydrogen-bonding solvents, such as dichloromethane, do not slow down the reaction. [ABSTRACT FROM AUTHOR]

Trifluoroethanol as an efficient media for the domino Knoevenagel-hetero-Diels-Alder reaction of O-propargyloxy benzaldehydes as non-activated terminal alkynes with some active methylene compounds has been described. Short reaction time, easy work-up, good to high yields, and mild reaction conditions are advantages of this new media. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A 'double-hydrophobic' elastin-like triblock polypeptide GPG has been constructed by mimicking the localization of proline- and glycine-rich hydrophobic domains of native elastin, a protein that provides elasticity and resilience to connective tissues. In this study, the effects of trifluoroethanol (TFE), an organic solvent that strongly affects secondary structures of polypeptides on self-assembly of GPG in aqueous solutions were systematically studied. Beaded nanofiber formation of GPG, where nanoparticles are initially formed by coacervation of the polypeptides followed by their connection into one-dimensional nanostructures, is accelerated by the addition of TFE at the concentrations up to 30% (v/v), whereas aggregates of nanoparticles are formed at 60% TFE. The concentration-dependent assembly pattern discussed is based on the influence of TFE on the secondary structures of GPG. Well-defined nanofibers whose diameter and secondary structures are controlled by TFE concentration may be ideal building blocks for constructing bioelastic materials in tissue engineering. © 2014 Wiley Periodicals, Inc. Biopolymers 103: 175-185, 2015. [ABSTRACT FROM AUTHOR]

Natively unfolded (intrinsically disordered) proteins have attracted growing attention due to their high abundance in nature, involvement in various signalling and regulatory pathways and direct association with many diseases. In the present work the combined effect of temperature and alcohols, trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP), on the natively unfolded 4E-BP1 protein was studied to elucidate the balance between temperature-induced folding and unfolding in intrinsically disordered proteins. It was shown that elevated temperatures induce reversible partial folding of 4E-BP1 both in buffer and in the mixed solutions containing denaturants. In the mixed solutions containing TFE (HFIP) 4E-BP1 adopts a partially folded helical conformation. As the temperature increases, the initial temperature-induced protein folding is replaced by irreversible unfolding/melting only after a certain level of the protein helicity has been reached. Onset unfolding temperature decreases with TFE (HFIP) concentration in solution. It was shown that an increase in the temperature induces two divergent processes in a natively unfolded protein-hydrophobicity-driven folding and unfolding. Balance between these two processes determines thermal behaviour of a protein. The correlation between heat-induced protein unfolding and the amount of helical content in a protein is revealed. Heat-induced secondary structure formation can be a valuable test to characterise minor changes in the conformations of natively unfolded proteins as a result of site-directed mutagenesis. Mutants with an increased propensity to fold into a structured form reveal different temperature behaviour. [ABSTRACT FROM AUTHOR]

The spectroscopic, electrochemical and coreactant electrogenerated chemiluminescence (ECL) properties of Ir(ppy)3 (where ppy = 2-phenylpyridine) have been obtained in aqueous buffered (KH2PO4), 50 : 50 (v/v) acetonitrile-aqueous buffered (MeCN-KH2PO4) and 30% trifluoroethanol (TFE) solutions. Tri-n-propylamine was used as the oxidative-reductive ECL coreactant. The photoluminescence (PL) efficiency (ϕem) of Ir(ppy)3 in TFE (ϕem ≈ 0.029) was slightly higher than in 50 : 50 MeCN-KH2PO4 (ϕem ≈ 0.0021) and water (ϕem ≈ 0.00016) compared to a Ru(bpy)32+ standard solution in water (Φem ≈ 0.042). PL and ECL emission spectra were nearly identical in all three solvents, with dual emission maxima at 510 and 530 nm. The similarity between the ECL and PL spectra indicate that the same excited state is probably formed in both experiments. ECL efficiencies (ϕecl) in 30% TFE solution (ϕecl = 0.0098) were higher than aqueous solution (ϕecl = 0.00092) system yet lower than a 50% MeCN-KH2PO4 solution (ϕecl = 0.0091). Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Conformational alterations and aggregates of chickpea cystatin (CPC) were investigated upon sequential addition of trifluoroethanol (TFE) over a range of 0–70% v/v. CPC on 30% and 40% v/v TFE addition exhibited non-native β-sheet, altered intrinsic fluorescence, increased thioflavin T fluorescence, prominent red shifted shoulder peak in Congo red absorbance, and enhanced turbidity as well as Rayleigh scattering, suggesting the aggregate formation. TEM results confirmed the formation of fibrillar aggregates at 30% and 40% v/v TFE. On increasing concentration of TFE to 70% v/v, CPC showed retention of native-like secondary structure, increased intrinsic and ANS fluorescence. Thus our results show that favourable condition for fibrillation of CPC is in the range of 30–40% TFE. Moreover, anti-aggregational effects of polyphenols, epicatechin (EC) and tannic acid (TA) were analysed using ThT binding assay and other biophysical assays. EC and TA produced a concentration dependent decline in ThT fluorescence suggesting inhibition of the fibril formation. Furthermore, TA in comparison to EC, served as a more effective inhibitor against amyloid fibril formation of CPC. This work supports the universality of the amyloid-like aggregation not restricted to some special categories of protein and the fact that this aggregation can be prevented. [ABSTRACT FROM AUTHOR]

Δ78Δ is a second generation functional all-β sheet variant of IFABP (intestinal fatty acid binding protein) corresponding to the fragment 29-106 of the parent protein. This protein and its predecessor, Δ98Δ (segment 29-126 of IFABP), were initially uncovered by controlled proteolysis. Remarkably, although IFABP and Δ98Δ are monomers in solution, Δ78Δ adopts a stable dimeric structure. With the aim of identifying key structural features that modulate the aggregation of β-proteins, we evaluate here the structure and aggregation propensity of Δ78Δ. The 2,2,2-trifluoroethanol (TFE) induced aggregation of this protein shows a primary nucleation-elongation mechanism, characterized by the stabilization of a dimeric nucleus. Its rate of production from the co-solvent induced aggregation prone state governs the kinetics of polymerization. In this context, the value of Δ78Δ lies in the fact that - being a stable dimeric species - it reduces an otherwise bimolecular reaction to a unimolecular one. Interestingly, even though Δ78Δ and IFABP display similar conformational stability, the abrogated form of IFABP shows an enhanced aggregation rate, revealing the ancillary role played on this process by the free energy of the native proteins. Δ78Δ share with IFABP and Δ98Δ a common putative aggregation-prone central peptide. Differences in the exposure/accessibility of this segment dictated by the environment around this region might underlie the observed variations in the speed of aggregation. Lessons learnt from this natural dimeric protein might shed light on the early conformational events leading to β-conversion from barrels to amyloid aggregates. [ABSTRACT FROM AUTHOR]

The inclusion of peptoid monomers into antimicrobial peptides (AMPs) increases their proteolytic resistance, but introduces conformational flexibility (reduced hydrogen bonding ability and cis/trans isomerism). We here use NMR spectroscopy to answer how the insertion of a peptoid monomer influences the structure of a regular α‐helical AMP upon interaction with a dodecyl phosphocholine (DPC) micelle. Insertion of [(2‐methylpropyl)amino]acetic acid in maculatin‐G15 shows that the structural change and conformational flexibility depends on the site of insertion. This is governed by the micelle interaction of the amphipathic helices flanking the peptoid monomer and the side chain properties of the peptoid and its preceding residue.A high‐resolution structure of a peptoid–peptide hybrid (“peptomer”) is presented. The peptoid residue breaks the helix and displays cis/trans isomerism. Maculatin‐Nleu11 displays only the trans isomer. Maculatin‐Nleu13 displays almost equimolar amounts of cis and trans conformers. Peptide amphipathicity and peptoid hydrophobicity govern the cis/trans isomerism. [ABSTRACT FROM AUTHOR]

Aggregation of protein into insoluble intracellular complexes and inclusion bodies underlies the pathogenesis of human neurodegenerative diseases. Importance of cytochrome c (cyt c) arises from its involvement in apoptosis, sequence homology and for studying molecular evolution. A systemic investigation of polyethylene glycol (PEG) and trifluoroethanol (TFE) on the conformational stability of cyt c as a model hemeprotein was made using multi-methodological approach. Cyt c exists as molten globule (MG) at 60 % PEG-400 and 40 % TFE as confirmed by far-UV CD, attenuated total reflection Fourier transform infrared spectroscopy, Trp environment, 8-anilino-1-naphthalene-sulfonic acid (ANS) binding and blue shift in the soret band. Q-band splitting in MG states specifies conformational changes in the hydrophobic heme-binding pocket. Aggregates were detected at 90 % PEG-400 and 50 % TFE as confirmed by increase thioflavin T and ANS fluorescence and shift in Congo red absorbance. Detection of prefibrils and protofibrils at 90 % PEG-400 and 50 % TFE was possible after 72-h incubation. Single cell gel electrophoresis of prefibrils and protofibrils showed DNA damage confirming their toxicity and potential health hazards. Scanning electron microscopy and XRD analysis confirmed prefibrillar oligomers and protofibrils of cyt c. [ABSTRACT FROM AUTHOR]

Highlights: [•] HCAII forms amyloid-like aggregates at moderate concentration of trifluoroethanol. [•] Protein adopts a state between β-sheet and α-helix at moderate % of TFE. [•] Hydrophobic surface(s) of partially structured conformation forms amyloid. [•] High % of TFE induces stable α-helical state preventing aggregation. [Copyright &y& Elsevier]