Organic Cosolvents Research Articles

Cholesterol Chip for the Study of Cholesterol-Protein Interactions Using SPR.

Cholesterol, an important lipid in animal membranes, binds to hydrophobic pockets within many soluble proteins, transport proteins and membrane bound proteins. The study of cholesterol–protein interactions in aqueous solutions is complicated by cholesterol’s low solubility and often requires organic co-solvents or surfactant additives. We report the synthesis of a biotinylated cholesterol and immobilization of this derivative on a streptavidin chip. Surface plasmon resonance (SPR) was then used to measure the kinetics of cholesterol interaction with cholesterol-binding proteins, hedgehog protein and tyrosine phosphatase 1B.

Inhibitory Effect of DMSO on Halohydrin Dehalogenase: Experimental and Computational Insights into the Influence of an Organic Co-solvent on the Structural and Catalytic Properties of a Biocatalyst.

Invited for the cover of this issue are Zlatko Brkljača, Maja Majerić Elenkov and co-workers at the Ruđer Bošković Institute and University of Zagreb. The image depicts the enzyme halohydrin dehalogenase HheC, which is made up of four identical subunits, with marked catalytic residues and volumetric maps of water and DMSO in the active site. Read the full text of the article at 10.1002/chem.202201923.

Inhibitory Effect of DMSO on Halohydrin Dehalogenase: Experimental and Computational Insights into the Influence of an Organic Co-solvent on the Structural and Catalytic Properties of a Biocatalyst.

Although the application of organic solvents in biocatalysis is well explored, in-depth understanding of the interactions of solvent with proteins, in particular oligomeric ones, is still scant. Understanding these interactions is essential in tailoring enzymes for industrially relevant catalysis in nonaqueous media. In our study, the homotetrameric enzyme halohydrin dehalogenase (HHDH) from Agrobacterium radiobacter AD1 (HheC) was investigated, as a model system, in DMSO/water solvent mixtures. DMSO, the most commonly used co-solvent for biocatalytic transformations, was found to act as a mixed-type inhibitor with a prevalent competitive contribution. Even 5 % (v/v) DMSO inhibits the activity of HheC by half. Molecular dynamics (MD) simulations showed that DMSO keeps close to Ser-Tyr catalytic residues forming alternate H-bonds with them. Stability measurements paired with differential scanning calorimetry, dynamic light scattering methods and MD studies revealed that HheC maintains its structural integrity with as much as 30 % (v/v) DMSO.

FRET pumping of rhodamine-based probe in light-harvesting nanoparticles for highly sensitive detection of Cu2+

In this work we presented novel strategy for increasing the performance of popular fluorescent probes on the basis of rhodamine-lactam platform. This strategy is based on the incorporation of probe molecules into the light-harvesting nanoparticles to pump modulated optical signal by Förster resonant energy transfer. Using the commercially available Cu2+ probe as a reference chemical, we have developed an efficient approach to significantly improve its sensing performance. Within obtained nanoparticles coumarin-30 nanoantenna absorbs excitation light and pumps incorporated sensing molecules providing bright fluorescence to a small number of emitters, while changing the probe-analyte equilibrium from liquid-liquid to solid-liquid significantly increased the apparent association constant, which together provided a ∼100-fold decrease in the detection limit. The developed nanoprobe allows highly sensitive detection of Cu2+ ions in aqueous media without organic co-solvents usually required for dissolution of the probe, and demonstrate compatibility with inexpensive fluorometers and the ability to detect low concentrations with the naked eye.

A New Logistically Simple Solution for Implementing Alkali-Surfactant-Polymer/Alkali-Cosolvent-Polymer in Difficult Environments: Evaluation of Concept with High Total Acid Number Viscous Crude Oil

Summary Research on alkali-assisted chemical enhanced oil recovery (EOR) technology [alkali-surfactant-polymer (ASP)/alkali-cosolvent-polymer (ACP)] with high total acid number (TAN) crude oils has led to developments with liquid organic alkalis and cosolvents (Southwick et al. 2020; Fortenberry et al. 2015; Schumi et al. 2019; Upamali et al. 2018). Both concepts afford potential significant cost reduction in field operations, but to date it has not been demonstrated that these two concepts can work together. Monoethanolamine (MEA) alkali and a wide variety of liquid cosolvents are evaluated with high TAN crude oil (1.5 mg KOH/g oil). Formulations are found that give ultralow interfacial tension (UL-IFT) at a specified injection salinity. Fine tuning the formulation to different injection salinities can be done by choosing alternate cosolvents (or a cosolvent blend). A formulation comprising 1% MEA and a novel high molecular weight (3152 g/gmol) cosolvent, 0.5% glycerin alkoxylate with 30 mol of propylene oxide and 35 mol of ethylene oxide (glycerin-30PO-35EO), gave UL-IFT in 21,000 total dissolved solids (TDS) injection brine and gave 100% oil recovery in Bentheimer sandstone with 3,500 ppm FP 3630Ss (SNF Flopaam 3630Sis partially hydrolyzed polyacrylamide) as mobility control agent. All oil was produced clean, no separation of emulsion was needed to measure oil recovery. Alkali consumption tests were also performed with a high-permeability reservoir sandstone. Results confirmed earlier data published with Boise outcrop sandstone (Southwick et al. 2020) showing low alkali consumption with MEA. On a mass basis, only 12% of the amount of MEA is consumed relative to the amount of sodium carbonate consumed. This reduces the logistical challenges of shipping chemicals to remote locations. MEA is also a low-viscosity liquid which further simplifies field handling.

Engineered living hydrogels for robust biocatalysis in pure organic solvents

Engineered living hydrogels that can protect cells from harsh environments have achieved preliminary successes in biomedicine and environmental remediation. However, their biocatalytic applications in pure organic solvents have not been explored. Here, living hydrogels were engineered by integrating genetically modified Escherichia coli cells into alginate hydrogels for robust biocatalysis in pure organic solvents. The biocompatible hydrogels could not only support cell growth and diminish cell escape but could also act as protective matrices to improve organic solvent tolerance, thereby prolonging catalytic activity of whole-cell biocatalysts. Moreover, the influence of hydrogel microenvironments on biocatalytic efficiency was thoroughly investigated. Importantly, the versatility of engineered living hydrogels paves the way to achieve robust biocatalytic efficiency in a variety of pure organic co-solvents. Overall, we are able to engineer living hydrogels for regio-selective synthesis in pure organic solvents, which may be particularly useful for the innovation of living hydrogels in biocatalysis. • Living hydrogels are engineered by integrating microbial cells and alginate hydrogels • Hydrogel microenvironments modulate catalytic efficiency of engineered living hydrogels • Engineered living hydrogels enable improved solvent tolerance in pure organic solvents • The versatility of engineered living hydrogels for robust biocatalysis is verified A versatile strategy to improve the organic solvent tolerance of whole-cell biocatalysts is highly demanded. Gao et al. design engineered living hydrogels using genetically modified microbial cells for improved organic solvent tolerance and robust biocatalysis in pure organic solvents.

Sulphoxidation reactions catalysed by the Baeyer-Villiger monooxygenase OTEMO from Pseudomonas putida ATCC 17453

The Baeyer-Villiger monooxygenase OTEMO from Pseudomonas putida ATCC 17453 has been employed as biocatalyst in the asymmetric synthesis of a set of optically active sulphoxides. Several alkyl aryl sulphides are oxidized by this biocatalyst leading to the (S)-sulphoxides. Especially for those substrates containing electron-donating groups in the aromatic ring or in the alkyl moiety, good to high enantiopurities can be obtained. OTEMO is also able to perform the kinetic resolution of racemic sulphoxides, but with low enantioselectivities. Finally, parameters that can affect its biocatalytic properties, such as pH, temperature, organic cosolvents and substrate concentration, have been tested to get a better insight into the biocatalytic potential of this hitherto poorly explored oxidative biocatalyst.

Spectroscopic investigation of preferential solvation of N-confused tetraphenylporphyrinin binary mixtures of dichloromethane with organic cosolvents

Spectroscopic behaviour of porphyrin is known to be sensitive to the choice of the solvent and has been used to probe solvation phenomena. The UV–visible spectra of N-confused tetraphenylporphyrin are observed in a series of binary solvent mixtures – (dichloromethane + diethyl ether), (dichloromethane + chlorobenzene) and (dichloromethane + ethyl acetate). The resulting ET scale for NCTPP solvation indicates nonlinear behaviour and preferential solvation by a solvent–solvent complex in all the three solvents – with the dichloromethane + ethyl acetate system showing the largest deviation from ideality. The data is fitted to the model based on solvent exchange equilibria for determining the preferential solvation parameters which are specific to the probe as well as the identity of solvents in the binary mixture. Further analysis using polarity parameters from literature indicate that the solvation of NCTPP in the (dichloromethane + ethyl acetate) mixture is dependent on the hydrogen bond accepting capacity and polarizability of the medium. Excess spectra derived from ATR-FTIR measurement of dichloromethane + ethyl acetate solutions lead to important inferences about the structure and role of solvent–solvent interactions responsible for the preferential solvation.

Oleic acid based experimental evolution of Bacillus megaterium yielding an enhanced P450 BM3 variant

BackgroundUnlike most other P450 cytochrome monooxygenases, CYP102A1 from Bacillus megaterium (BM3) is both soluble and fused to its redox partner forming a single polypeptide chain. Like other monooxygenases, it can catalyze the insertion of oxygen unto the carbon-hydrogen bond which can result in a wide variety of commercially relevant products for pharmaceutical and fine chemical industries. However, the instability of the enzyme holds back the implementation of a BM3-based biocatalytic industrial processes due to the important enzyme cost it would prompt.ResultsIn this work, we sought to enhance BM3’s total specific product output by using experimental evolution, an approach not yet reported to improve this enzyme. By exploiting B. megaterium’s own oleic acid metabolism, we pressed the evolution of a new variant of BM3, harbouring 34 new amino acid substitutions. The resulting variant, dubbed DE, increased the conversion of the substrate 10-pNCA to its product p-nitrophenolate 1.23 and 1.76-fold when using respectively NADPH or NADH as a cofactor, compared to wild type BM3.ConclusionsThis new DE variant, showed increased organic cosolvent tolerance, increased product output and increased versatility in the use of either nicotinamide cofactors NADPH and NADH. Experimental evolution can be used to evolve or to create libraries of evolved BM3 variants with increased productivity and cosolvent tolerance. Such libraries could in turn be used in bioinformatics to further evolve BM3 more precisely. The experimental evolution results also supports the hypothesis which surmises that one of the roles of BM3 in Bacillus megaterium is to protect it from exogenous unsaturated fatty acids by breaking them down.

Highly stable gold nanoparticles in an aqueous solution without any stabilizer prepared by a solution plasma process evaluated through capillary zone electrophoresis.

Gold nanoparticles (AuNP) were prepared by a solution plasma process in the presence of H2O2, and they were dispersed in an aqueous solution without any stabilizer generally used. The dispersion stability of the AuNP in an aqueous solution was evaluated by capillary zone electrophoresis (CZE). An anionic broad peak was detected with the AuNP by CZE based on its wide variations in size and net charge. The broad peak also suggests that the AuNP were well dispersed in an aqueous solution. The dispersion stability of AuNP was evaluated from the viewpoints of long-term dispersion, salt concentration, and organic co-solvent. The anionic broad peak attributed to the dispersed AuNP was successfully detected for at least 55weeks from the preparation with less shot signals of the aggregates. The AuNP was also well dispersed in aqueous NaCl solutions with its concentrations up to 30mmol L-1, as well as with ethanol co-solvent up to 40%(v/v). The AuNP prepared by the solution plasma process was proved to be highly stable in an aqueous solution.

Comparing the effects of organic cosolvents on acetylcholinesterase and butyrylcholinesterase activity

The use of cosolvents to solubilize compounds under investigation while having minimal effects on enzyme activity is an important component in many biochemical studies. Predicting the effects of cosolvents on enzyme activity can be complicated, as enzymes with similar overall structures might exhibit different behaviors in different cosolvents. In this study, the effects of several commonly used cosolvents: Methanol, acetonitrile, acetone, and dimethyl sulfoxide (DMSO), on two cholinesterases, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), were evaluated. Although the overall structures are highly similar, AChE activity was more sensitive to the organic cosolvents tested compared to BChE. Effects of the cosolvents on activity did not vary over time and activity was restored upon dilution of the cosolvent. Michaelis-Menten kinetics experiments showed that Vmax values were not substantially affected, while KM values increased up to ∼20-fold for AChE and ∼4-fold for BChE in the presence of 5% DMSO or acetone. The results suggest that BChE demonstrates more robustness to its cosolvent environment compared to AChE, and that cosolvents effects may arise from the molecules acting as inhibitors. The results may aid decisions of cosolvents used in enzyme assays and may help guide experimental conditions and design when conducting experiments comparing different enzymes.

Aqueous Electrolytes with Hydrophobic Organic Cosolvents for Stabilizing Zinc Metal Anodes.

Rechargeable aqueous zinc (Zn) batteries are promising for large-energy storage because of their low cost, high safety, and environmental compatibility, but their implementation is hindered by the severe irreversibility of Zn metal anodes as exemplified by water-induced side reactions (H2 evolution and Zn corrosion) and dendrite growth. Here, we find that the introduction of a hydrophobic carbonate cosolvent into a dilute aqueous electrolyte exhibits a much stronger ability to address the reversible issues facing Zn anodes than that with hydrophilic ones. Among the typical carbonates (ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate (DEC)), DEC as the most hydrophobic additive enables the strongest breaking of water's H-bond network and replaces the solvating H2O in a Zn2+-solvation sheath, which significantly reduces the water activity and its decomposition. Additionally, DEC molecules preferentially adsorb onto the Zn surface to create an H2O-poor electrical double layer and render a dendrite-free Zn2+-plating behavior. The formulated hybrid 2 m Zn(OTf)2 + 7 m DEC electrolyte endows the Zn electrode with an ability to achieve high cycling stability (over 3500 h at 5 mA cm-2 with 2.5 mA h cm-2) and supports the stable operation of Zn||V2O5·nH2O full battery. This efficient strategy with hydrophobic cosolvent suggests a promising direction for designing aqueous battery chemistries.

Assessing Peroxygenase-Mediated Oxidations in the Presence of High Concentrations of Water-Miscible Co-Solvents

The use of water-miscible organic co-solvents in biocatalysis is a simple procedure for obtaining higher enzymatic activities toward hydrophobic substrates. However, effects on activity and stability have to be carefully evaluated, also with regard to the type and concentration of the respective co-solvent. In this contribution, we investigated and evaluated the effect of some common water-miscible co-solvents on the biocatalytic performance of the recombinant unspecific peroxygenase rAaeUPO from Agrocybe aegerita. rAaeUPO showed promising activities in the presence of high concentrations of the best co-solvent acetonitrile, which enabled to use higher substrate concentrations (≥100 mM). Employing high acetonitrile concentrations for UPO-mediated oxidation of ethylbenzene to (R)-1-phenylethanol was demonstrated under preparative scale conditions and led to product accumulation rates of 31 mM h−1.

Water‐Soluble (Poly)acylhydrazones: Syntheses and Applications

AbstractAcylhydrazone‐based (macro)molecules display an increasingly broad spectrum of applications, from small therapeutic molecules and metal‐ions probes to self‐healing films and biorelevant dynamic polymers. The acylhydrazone function is indeed of prime interest since its unique design combines hydrogen bonds, pH‐dependent reversibility, ability to undergo molecular exchanges, and a possible polyvalency. However, a key parameter of its use in aqueous media is the associated water‐solubility of the resulting (macro)molecule. This property can indeed become a limitation for applications requiring high concentrations or no organic cosolvent. This review first focuses on describing the acylhydrazone function, its properties, and its relevancy in dynamic combinatorial chemistry. Then it details the synthesis strategies (molecular design, cosolvent, reaction conditions) reported in the literature to ensure a sufficient solubilization of both single‐bond and multiple‐bond acylhydrazone (macro)molecules, together with their various applications.

Expanding Access to Optically Active Non-Steroidal Anti-Inflammatory Drugs via Lipase-Catalyzed KR of Racemic Acids Using Trialkyl Orthoesters as Irreversible Alkoxy Group Donors

Studies into the enzymatic kinetic resolution (EKR) of 2-arylpropanoic acids (‘profens’), as the active pharmaceutical ingredients (APIs) of blockbuster non-steroidal anti-inflammatory drugs (NSAIDs), by using various trialkyl orthoesters as irreversible alkoxy group donors in organic media, were performed. The enzymatic reactions of target substrates were optimized using several different immobilized preparations of lipase type B from the yeast Candida antarctica (CAL-B). The influence of crucial parameters, including the type of enzyme and alkoxy agent, as well as the nature of the organic co-solvent and time of the process on the conversion and enantioselectivity of the enzymatic kinetic resolution, is described. The optimal EKR procedure for the racemic profens consisted of a Novozym 435-STREM lipase preparation suspended in a mixture of 3 equiv of trimethyl or triethyl orthoacetate as alkoxy donor and toluene or n-hexane as co-solvent, depending on the employed racemic NSAIDs. The reported biocatalytic system provided optically active products with moderate-to-good enantioselectivity upon esterification lasting for 7–48 h, with most promising results in terms of enantiomeric purity of the pharmacologically active enantiomers of title APIs obtained on the analytical scale for: (S)-flurbiprofen (97% ee), (S)-ibuprofen (91% ee), (S)-ketoprofen (69% ee), and (S)-naproxen (63% ee), respectively. In turn, the employment of optimal conditions on a preparative-scale enabled us to obtain the (S)-enantiomers of: flurbiprofen in 28% yield and 97% ee, ibuprofen in 45% yield and 56% ee, (S)-ketoprofen in 23% yield and 69% ee, and naproxen in 42% yield and 57% ee, respectively. The devised method turned out to be inefficient toward racemic etodolac regardless of the lipase and alkoxy group donor used, proving that it is unsuitable for carboxylic acids possessing tertiary chiral centers.

Cyclodextrins and Drug Membrane Permeation: Thermodynamic Considerations

Cyclodextrins are hydrophilic oligosaccharides that can increase aqueous solubility of lipophilic drugs through formation of water-soluble drug/cyclodextrin complexes. Although the complexes are hydrophilic, and as such do not permeate biological membranes, the complexes are known to enhance drug permeation through lipophilic membranes and improve drug bioavailability after, for example, oral administration. However, it is not clear how cyclodextrins enhance the permeation. An artificial biomembrane (PermeaPad®) was used to study the effect of donor medium composition on drug permeation. It was observed that in aqueous solutions the hydrophilic cyclodextrins behave not like disperse systems but rather like organic cosolvents such as ethanol, increasing the solubility without having significant effect on the molecular mobility and ability of lipophilic drug molecules to partition into the lipophilic membrane. Also, that partition of dissolved drug molecules from the aqueous exterior into the membrane is at its maximum when their thermodynamic activity is at its maximum. In other words, that drug flux from aqueous cyclodextrin solutions through lipophilic membranes depends on both the concentration and the thermodynamic activity of dissolved drug. Maximum flux is obtained when both the drug concentration and thermodynamic activity of the dissolved drug molecules are at their maximum value.

Dependence of Quinone Electrochemistry on Solvent Polarity and pH

We studied the polarographic reduction of quinones in aqueous/organic mixtures with dielectric constants (ε) from 78.4 down to 47. Added organic co-solvents were either protic or aprotic. The increase in polarographic half-wave potential, E 1/2, with declining ε was successfully fit to the Born equation down to ε ≈ 55. Cu2+ and ubiquinone0 were reduced in a single two-electron step that was more ε-sensitive when the added organic co-solvent was aprotic. Naphtho- and anthraquinone were reduced in two successive one-electron steps that were influenced identically by protic or aprotic organic co-solvents. The product of the first reduction wave was neutral semiquinone (·QH), which surprisingly, had to be protonated to ·QH2 + before reduction in the second wave. Except for r H+, radii derived from fitting our E 1/2 vs ε results to the Born equation were too small; in other words, non-electrostatic effects destabilized the oxidized species, greatly enhancing the Born electrostatic increase in E 1/2 with declining ε. Additionally, for ε < 55, we observed deviation from the Born equation, which may be due to changes in solvent structure and dynamics, and solvent-solute interactions. Finally, we studied quinones incorporated into phosphatidyl choline sonicated bilayer vesicles: Ubiquinone0 had two distinct irreversible two-electron reduction waves, one due to a population bound at the membrane surface, and another (whose E 1/2 was negatively shifted by 150 mV) due to a population localized in the membrane interior. Ubiquinone10 had a single irreversible two-electron reduction wave that was 250 mV more negative than the UQ0 membrane-interior population.

Widom and extrema lines as criteria for optimizing operating conditions in supercritical processes

This work focuses on the supercritical region of fluid phase equilibria, just above the critical point. It is already known that in this area, two different zones can be distinguished, one where supercritical fluids (SCFs) have liquid-like properties, and the other one where SCFs have gas-like properties; these two zones being delimited by the Widom and extrema lines. This work draws attention to these lines, indicating that they may serve to guide the choice of process operating conditions. Three simple approaches for the prediction of the Widom line and extrema lines of binary mixtures involving CO2 for any composition are proposed. The Widom line and extrema lines of binary mixtures involving CO2 with eight very common organic cosolvents, as well as water, are predicted for different compositions (5%, 10% and 50% of cosolvent).

Room temperature synthesis of lanthanum phosphates with controlled nanotexture as host for Ln(III) through the Epoxide Route

Herein, the Epoxide Route, a one-pot room temperature alkalinization method based on the reaction between a nucleophile and an epoxide, has been employed to synthesize LaPO4 in the form of a Rhabdophane phase. The intrinsic features of this synthetic approach allow the reaction to be followed by pH monitoring, making possible the identification of the different precipitation steps involved in the formation of the solid. Once demonstrated the effectiveness of this chemical methodology, the size and shape of the LaPO4 particles were controlled by varying the identity and proportion of the organic co-solvents employed to perform the reaction. By these means, crystalline particles with dumbbell, urchin and needle shapes were obtained, with sizes that ranged from less than 200 nm to more than 5 μm. Finally, luminescent materials in the form of a LnPO4Rhabdophane structure were easily obtained by the incorporation of EuIII along the whole composition range. Additionally, photophysical characterization of selected samples was performed, with a promising outcome. The results presented in this work pave the way to obtaining a wide variety of luminescent materials with sizes and morphologies adjustable on demand, by using a simple and reliable synthetic approach.The Epoxide Route has been adapted to drive the precipitation of lanthanum phosphates exhibiting high control on size and morphology through a solvent-controlled growth approach. Additionally, this synthetic scenario allows the obtaining of luminescent materials by simply incorporating Eu(III) in the whole composition range.

LDAmy, an α-amylase from Colorado potato beetle (Leptinotarsa decemlineata) with transglycosylation activity

Potential of α-amylase from the gut of Leptinotarsa decemlineata (LDAmy) to catalyse transfer reactions was investigated. LDAmy as a component of insect gut extract showed significant transfer activity on reducing-end- and both-end-protected maltoheptamer substrates. Transfer reaction was examined using purified enzyme, 2-chloro-4-nitrophenyl β-d-glucopyranoside as acceptor and starch and maltooligosaccharides as donors. In addition to suitability of various donors, effect of pH and acetonitrile (MeCN) concentration were also studied. The reactions were followed using separation of reaction products by a reversed phase HPLC method. LDAmy catalysed the hydrolysis and transglycosylation of the both-end-protected substrate 4,6-O-benzylidene-4-nitrophenyl β-maltoheptaoside in parallel reactions. Shorter and longer both-end-protected products with degree of polymerization 4–10 were formed. Identification of products was carried out based on HPLC retention time, UV and mass spectra. Ratio of transglycosylation to hydrolysis reached 0.5 in presence of 20% MeCN as organic solvent. Aromatic protecting group at the non-reducing end was favourable for transfer reaction. Lack of the mobile loop and presence of more nonpolar aromatic moieties near to the active site may be the reason for the enhanced transfer activity of LDAmy based on the comparison of the sequence and structure of mammalian and insect-derived α-amylases. Highlights Transferase activity of Colorado potato beetle derived α-amylase LDAmy is presented. Effect of pH and organic co-solvent on transfer reaction of LDAmy were studied. Shorter and longer products were formed from a both-end protected maltoheptamer. The unusual transfer ability was explained by sequence differences of α-amylases.