Aqueous Buffer Research Articles

Centrifugal partition chromatography as a potential method of isolation and purification of amphiphilic substances from a solid-state fermentation process

Separating amphiphilic compounds from complex matrix is challenging. Surfactin, cyclic lipopeptides group, was used as a model to find the proper separation conditions and parameters. The aim of the work was to solve the emulsification plug problem in countercurrent partition chromatography (CPC). The selected solvent system was a composition of n-heptane/n-butanol/methanol/aqueous buffer (20 mM disodium phosphate with 50 mM NaCl) at a ratio of 2:3:2:3. Several elution method modifications were applied. The most important was an appropriate mobile phase flow rate adjustment (flow rate gradient), minimizing the risk of stationary phase leakage. During the CPC procedures, the hydrostatic pressure was monitored as a factor of stationary phase retention. The hydrostatic pressure indicated the biphasic system’s stability. A flow rate of 2 ml/min resulted in column stabilization and peak resolution during chromatographic separation. In order to avoid uncontrolled leakage, the flow rate was increased gradually. At 3.5 ml/min, there was a small loss of the stationary phase as the hydrostatic pressure decreased from 32 to nearly 18 bar. After designing the method, it was tested with SU containing extracts obtained from SSF to show its effectiveness. Our results showed that the single dual-mode method can be used to remove matrix’s impurities and separate surfactin as a mixture of homologues with more than 80% purity. Moreover, application of the double dual-mode method allows for the isolation of fractions containing individual surfactin homologues in amounts of about 70% of the sample, which makes it possible to conduct further biological research.

Effect of structure isomerism of pyridine monocarboxylic acids on thermodynamic properties of l-lysine complexation in aqueous buffer solution

The thermodynamic characteristics (lgKc, ΔcG, ΔcH, ΔcS) of complexation of l-lysine, a polar basic amino acid, with isomeric pyridine monocarboxylic acids (picolinic acid, nicotinic acid, isonicotinic acid) in buffer solution (pH 7.4) have been obtained at 298.15 K by calorimetry method. The results indicate the formation of molecular complexes between Lys and pyridine carboxylic acids (PyCOOH) with 1:1 stoichiometry in the buffer solution. The complexation of amino acid is influenced by position of –COOH group in the pyridine ring relative to the nitrogen atom. The binding affinity of Lys with PyCOOH isomers follows the order as PA < NA < INA. The measured density values were used to calculate the apparent molar and the partial molar volumes at infinite dilution for PyCOOH isomers in Lys buffer solutions. The results revealed formation of Lys complexes with above pyridine monocarboxylic acids. The positive transfer volumes for the PyCOOH isomers decrease in the series NA ≥ INA > PA. The effects of solute concentration and structure isomerism of PyCOOH on the volume properties were discussed in terms of predominant types of molecular interactions (hydrophilic, hydrophobic, ionic and zwitterionic) on the basis of co-spheres overlap model.

Molecular Recognition of Imidazole-Based Drug Molecules by Cobalt(III)- and Zinc(II)-Coproporphyrins in Aqueous Media.

The methods of 1H NMR, spectrophotometric titration, mass spectrometry and elemental analysis are applied to determine the selective binding ability of Co(III)- and Zn(II)-coproporphyrins I towards a series of imidazole-based drug molecules with a wide spectrum of pharmacological activity (metronidazole, histamine, histidine, tinidazole, mercazolil, and pilocarpine) in phosphate buffer (pH 7.4) simulating the blood plasma environment. It is shown that in aqueous buffer media, Co(III)-coproporphyrin I, unlike Zn(II)-coproporphyrin I, binds two imidazole derivatives, and the stability of mono-axial Co-coproporphyrin imidazole complexes is two to three orders of magnitude higher than that of similar complexes of Zn-coproporphyrin I. The studied porphyrinates are found to have the highest binding ability to histamine and histidine due to the formation of two additional hydrogen bonds between the carboxyl groups of the porphyrinate side chains and the binding sites of the ligands in the case of histidine and a hydrogen bond between the amino group of the ligand and the carbonyl oxygen atom of the carboxyl group of the porphyrinate in the case of histamine. The structures of the resulting complexes are optimized by DFT quantum chemical calculations. The results of these studies may be of use in the design of biosensors, including those for the detection, control and verification of various veterinary drug residues in human food samples.

Design and Synthesis of Novel Helix Mimetics Based on the Covalent H-Bond Replacement and Amide Surrogate.

A novel hydrogen bond surrogate-based (HBS) α-helix mimetic was designed by the combination of covalent H-bond replacement and the use of an ether linkage to substitute an amide bond within a short peptide sequence. The new helix template could be placed in position other than the N-terminus of a short peptide, and the CD studies demonstrate that the template adopts stable conformations in aqueous buffer at exceptionally high temperatures.

Luminescence Sensing of Biomacromolecules Heparin and Protamine in 100% Human Serum and Plasma by Supramolecular Polymeric Assemblies.

Heparin, an anionic biomacromolecule, is routinely used as an anticoagulant during medical surgery to prevent blood clot formation and in the treatment of several heart, lung, and circulatory disorders having a higher risk of blood clotting. We herein report supramolecular polymeric nanoassemblies of cationic pyrene-tagged bis-imidazolium amphiphiles for heparin detection with high sensitivity and selectivity in aqueous buffer, plasma, and serum media. The nano-assemblies exhibited cyan-green excimeric emission in aqueous media, and their multivalent array of positive surface charges allowed them to form co-assemblies with heparin, resulting in significantly enhanced emission. This provided a convenient method for heparin detection in buffer at nanomolar concentrations, and most notably, a ratiometric fluorescence response was obtained even in highly competitive 100% human serum and 100% human plasma in a clinically relevant concentration range. Moreover, using the heparin-based luminescent co-assemblies, protamine sulfate, a clinically administered antidote to heparin, was also detected in 100% human serum and 100% human plasma at sub-micromolar concentrations.

Proton-Conductive and Electrochemical-Sensitive Sensing Behavior of a New Mn(II) Chain Coordination Polymer

In this work, a novel Mn(II) chain coordination polymer (Mn-CP), {[Mn(iip)(2bbpum)0.5(H2O)3]·2H2O}n [H2iip = 5-iodoisophthalic acid, 2bbpum = N,N′-bis(2-pyridinemethyl)oxamide] was synthesized under ambient conditions. Mn-CP further assembles into a 3D supramolecular architecture through hydrogen bonds, halogen bonds, and ππ stacking interactions. The composite Mn-CP/nafion membrane has low activation energy for proton transfer, which results in its temperature-insensitive proton conductivity. The cyclic voltammetry demonstrates that the Mn-CP electrode (Mn-CP/GCE) shows quite different redox properties in 0.1 M H2SO4 and 0.1 M PBS aqueous solutions. The Mn-CP/GCE exhibits a couple of irreversible redox peaks with an oxidation peak potential suitable for the nitrite oxidation in 0.1 M H2SO4. Quite differently, in the PBS aqueous buffer solution, the Mn-CP electrode has a couple of irreversible redox peaks. The reduction peak potential is appropriate for the H2O2 reduction. So, the Mn-CP/GCE can be used not only in the electrocatalytic oxidation of NO2– but also in the electrocatalytic reduction of H2O2. The amperometric response reveals that the Mn-CP/GCE exhibits high-selective and extremely sensitive oxidation sensing of NO2– and reduction sensing of H2O2. The exponential detection range is 0.01–20 mM for NO2– and 0.01–10.5 mM for H2O2. The linear detection range for both H2O2 and NO2– is 0.01–0.10 mM. The detection limit is 1.865 μM for NO2– and 8.57 μM for H2O2. The Mn-CP/GCE exhibits high electrochemical stability and fine reproducibility. Moreover, the strategy can be translated to a portable screen-printed electrode (SPE). The Mn-CP/SPE shows more sensitive sensing to NO2– and H2O2 than Mn-CP/GCE. Moreover, it can detect NO2– and H2O2 efficiently in the real-world samples. So, Mn-CP may be a potential dual nonenzymatic electrochemical sensory material for NO2–via oxidation sensing and H2O2via reduction sensing.

Sustainable synthesis of hierarchically grown chloramphenicol‐imprinted poly(caffeic acid) nanostructured films

AbstractHierarchically nanostructured chloramphenicol (CLP) imprinted thin polymer films have been developed using a renewable monomer, the antioxidant caffeic acid (CA), using sacrificial nanostructures to induce porosity into the films. The poly(caffeic acid) (PCA) films were synthesized on Au/quartz resonators via greener polymerization conditions (clean energy electropolymerization in aqueous buffer or a non‐ionic deep eutectic solvent). The sacrificial nanostructures explored included zein‐based protein nanobeads, anodized alumina membrane, and Tween 20‐derived polysorbate micelles, where dissolution of the sacrificial nanostructure templates from the PCA films afforded uniform long‐range hyperporous networks, nanowires and nanoparticles, respectively, as revealed by SEM studies. Selective extraction of the CLP template from PCA films, was monitored by XPS, and afforded CLP selective cavities. The CLP‐imprinted PCAzein films demonstrated eight‐ to 25‐fold higher sensitivity than the other nanostructures in a QCM‐sensor format, the limit of detection (LOD) under optimized FIA conditions was 50 mM. Significant sensitivities for CLP in milk were observed (1.5 μg/ml to 3 mg/ml), covering the clinically relevant concentration range. The PCAzein thin films selectively differentiate CLP from structurally related antibiotics and are robust. Their production from renewable feedstocks of biological origin highlights the potential of this class of nanostructured materials for applications utilizing thin films.

Chemical synthesis of a reported p47phox/p22phox inhibitor and characterization of its instability and irreproducible activity.

The nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) multi-subunit complex is a highly abundant and central source of reactive oxygen species. NOX2 is a key enzyme of the innate immune system involved in antibacterial response, but excessive NOX2 activity is involved in oxidative stress and inflammation in many diseases. Inhibition of NOX2 has great potential as a therapeutic strategy. An intriguing pharmacological approach for inhibiting NOX2 is to target the p47phox subunit and thereby block the protein-protein interaction with p22phox, whereby assembling and activation of NOX2 is prevented. However, the shallow binding pocket of p47phox makes it difficult to develop drug-like p47phox/p22phox inhibitors. Recently, the small molecule LMH001 was reported to inhibit the p47phox/p22phox interaction, reduce endothelial NOX2 activity, and protect mice from angiotensin II-induced vascular oxidative stress. These noteworthy results could have significant impact on the field of NOX2 pharmacology, as specific and efficient inhibitors are scarce. Here, we synthesized and tested LMH001 to have it available as a positive control. We established a robust synthetic route for providing LMH001, but subsequently we experienced that LMH001 is chemically unstable in aqueous buffer. In addition, neither LMH001 nor its breakdown products were able to inhibit the p47phox/p22phox interaction in a non-cellular fluorescence polarization assay. However, LHM001 was a weak inhibitor of NOX2 in a functional cell assay, but with same low potency as one of its breakdown products. These findings question the activity and suggested mechanism of LMH001 and constitute important information for other researchers interested in chemical probes for studying NOX2 biology.

Dissolvable microneedles for transdermal drug delivery showing skin penetration and modified drug release

Topical therapies for chronic skin diseases suffer from a low patient compliance due to the inconvenient treatment regimens of available products. Dissolvable microneedles (MN) with modified release offer an interesting possibility to increase the compliance by acting as a depot in the skin and thereby decreasing the dosing frequency. Furthermore, the bioavailability can be increased significantly by bypassing the barrier of the skin by the direct penetration of the MN into the skin. In this study the depot effect and skin penetration of an innovative dissolvable MN patch was assessed by insertion in ex vivo human skin and in vivo using minipigs. The MN patches are based on biodegradable polymers and the active pharmaceutical ingredients calcipotriol (Calci) and betamethasone-17–21-dipropionate (BDP) used to treat psoriasis. Using computed tomography (CT) and Coherent anti-Stokes Raman scattering (CARS) microscopy it was possible to visualize the skin penetration and follow the morphology of the MN as function of time in the skin. The depot effect was assessed by studying the modified in vitro release in an aqueous buffer and by comparing the drug release of a single application of a patch both ex vivo and in vivo to daily application of a marketed oleogel containing the same active pharmaceutical ingredients. The CT and CARS images showed efficient penetration of the MN patches into the upper dermis and a slow swelling process of the drug containing tip over a period of 8 days. Furthermore, CARS demonstrated that it can be used as a noninvasive technique with potential applicability in clinical settings. The in vitro release studies show a release of 54% over a time period of 30 days. The pharmacological relevance of MNs was confirmed in human skin explants and in vivo after single application and showed a similar response on calcipotriol and BDP mediated signaling events compared to daily application of the active oleogel. Altogether it was demonstrated that the MN can penetrate the skin and have the potential to provide a depot effect.

In-depth study of anticancer drug diffusion through a cross-linked ­pH-responsive polymeric vesicle membrane

Post-encapsulation and release of the anticancer drug doxorubicin hydrochloride (DOX·HCl) through cell-like transmission functions of polymeric vesicles were studied using cross-linked pH-responsive polymeric vesicles. The vesicles were fabricated for the first time via the redox-initiated reversible addition-fragmentation chain transfer dispersion polymerization in ethanol-water mixture, using 2-(diisopropylamino)ethyl methacrylate and glycidyl methacrylate, and the vesicle membrane was modified post-cross-linking by using ethylenediamine. A phase diagram was constructed for reproducible fabrication of the polymeric vesicles, and well-shaped vesicles were formed when the target degree of polymerization of the hydrophobic polymer chains was equal to or higher than 50 with solid content in the range of 10–30 wt%. The cross-linked vesicle membrane served as a gate enabling “open” and “closed” states in response to pH stimulation. Up to 50% drug loading efficiency and 39% drug loading content could be achieved, and in vitro release of the DOX-loaded vesicles in aqueous buffer solutions showed a much faster DOX release rate at pH 5.0 than at pH 6.5. The polymeric vesicles were of very low cytotoxicity to A549 cells up to the concentration of 2 mg/mL, and the IC50 of DOX-loaded vesicles were higher than that of the free DOX. The intracellular DOX release study indicated higher cellular uptake capability for DOX-loaded vesicles than that of free DOX.

Optical photothermal infrared spectroscopy and discrete wavenumber imaging for high content screening of single cells.

Major drawbacks of direct mid-infrared spectroscopic imaging of single cells in an aqueous buffer are strong water absorption, low resolution typically above 10 μm, and Mie scattering effects. This study demonstrates how an indirect detection principle can overcome these drawbacks using the optical photothermal infrared (O-PTIR) technique for high-resolution discrete wavenumber imaging and fingerprint spectroscopy of cultivated cells as a model system in a simple liquid sample chamber. The O-PTIR spectra of six leukemia- and cancer-derived cell lines showed main IR bands near 1648, 1547, 1447, 1400, 1220, and 1088 cm-1. Five spectra of approximately 260 single cells per cell type were averaged, the O-PTIR data set was divided into leukemia-derived cells (THP-1, HL 60, Jurkat, and Raji) and cancer cells (HeLa and HepaRG), and partial least squares linear discriminant analysis (PLS-LDA) was applied in the spectral range 800-1800 cm-1 to train three classification models. A leukemia versus cancer cell model showed an accuracy of 90.0%, the HeLa versus HepaRG cell model had an accuracy of 95.4%, and the model for the distinction of leukemia cells had an accuracy of 75.4%. IR bands in linear discriminants (LDs) of the models were correlated with second derivative spectra that resolved more than 25 subbands. The IR and second derivative spectra of proteins, DNA, RNA and lipids were collected as references to confirm band assignments. O-PTIR images of single cells at a 200 nm step size were acquired at 1086, 1548, and 1746 cm-1 to visualize the nucleic acid, protein, and lipid distribution, respectively. Variations in subcellular features and in the lipid-to-protein and nucleic acid-to-protein ratios were identified that were consistent with biomolecular information in LDs. In conclusion, O-PTIR can provide high-quality spectra and images with submicron resolution of single cells in aqueous buffers that offer prospects in high-content screening applications.

SIMBA Method-Simultaneous Detection of Antimicrobial and Anti-biofilm Activity of New Compounds Using Salmonella Infantis.

The development of antimicrobial resistance and the formation of Salmonella biofilms are serious public health problems. For this reason, new natural compounds with antimicrobial and anti-biofilm activity are being sought, and wild fungi represent an untapped potential. Various extraction agents, including organic solvents and aqueous buffers, can be used to obtain bioactive compounds from natural sources. To evaluate their bioactivity, extensive screening studies are required to determine antimicrobial and anti-biofilm activity using methods such as broth microdilution or crystal violet assay, respectively, but none of these methods allow simultaneous evaluation of both activities against bacteria. Cold water extraction from wild fungi offers the advantage of extracting water-soluble compounds. The SIMultaneous detection of antiMicrobial and anti-Biofilm Activity (SIMBA) method combines the testing of both types of activity against bacteria with the evaluation of the 20 h growth curve of the Salmonella Infantis ŽM9 strain determined with absorbance measurements at 600 nm in a 96-well plate. SIMBA method thus shortens the time to determine the bioactivity of extracts, reduces material consumption, and eliminates the need for additional reagents. SIMBA enables rapid selection of bioactive extracts for their fractionation and shortens the time to determine new natural products with antimicrobial and anti-biofilm activity. Graphical overview.

One-pot cascade reactions for the synthesis of dinitroalkanes in aqueous buffer

A one-pot combination of biocatalysis and organocatalysis converts aliphatic alcohols to dinitroalkanes in mild conditions at room temperature.

X-ray radio-enhancement by Ti3C2Tx MXenes in soft tissue sarcoma.

Radiotherapy is a cornerstone of cancer treatment. However, due to the low tissue specificity of ionizing radiation, damage to the surrounding healthy tissue of the tumor remains a significant challenge. In recent years, radio-enhancers based on inorganic nanomaterials have gained considerable interest. Beyond the widely explored metal and metal oxide nanoparticles, 2D materials, such as MXenes, could present potential benefits because of their inherently large specific surface area. In this study, we highlight the promising radio-enhancement properties of Ti3C2Tx MXenes. We demonstrate that atomically thin layers of titanium carbides (Ti3C2Tx MXenes) are efficiently internalized and well-tolerated by mammalian cells. Contrary to MXenes suspended in aqueous buffers, which fully oxidize within days, yielding rice-grain shaped rutile nanoparticles, the MXenes internalized by cells oxidize at a slower rate. This is consistent with cell-free experiments that have shown slower oxidation rates in cell media and lysosomal buffers compared to dispersants without antioxidants. Importantly, the MXenes exhibit robust radio-enhancement properties, with dose enhancement factors reaching up to 2.5 in human soft tissue sarcoma cells, while showing no toxicity to healthy human fibroblasts. When compared to oxidized MXenes and commercial titanium dioxide nanoparticles, the intact 2D titanium carbide flakes display superior radio-enhancement properties. In summary, our findings offer evidence for the potent radio-enhancement capabilities of Ti3C2Tx MXenes, marking them as a promising candidate for enhancing radiotherapy.

Impact of mobile phase composition on reverse-phase separation of polar basic compounds

Method development for determination of polar basic compounds on ion-suppression reverse-phase liquid chromatography, requires appropriate selection of stationary phase and composition and pH value of the mobile phase. The addition of the organic solvent in aqueous buffers with defined pH value, results in shift of the pH value of the mobile phase, resulting in significant change in chromatographic retention and selectivity. The aim of this study was to evaluate the impact of the variation of pH value of the mobile phase and percentage of the organic solvent, on the chromatographic separation of basic compound (octenidine dihydrochloride). The design of experiment was used for the optimization of the chromatographic conditions and selection of the most suitable mobile phase composition. The optimal composition of the mobile phase, providing satisfactory chromatographic performance based on ion-suppression reverse-phase chromatography, included 0.1M citric acid/0.2M sodium dihydrogen phosphate, pH =2.5, combined with 70% v/v organic solvent-acetonitrile. The suitability of the method was confirmed by satisfactory results for the system suitability parameters, specificity, linearity and precision. Key Words: polar basic compounds, ion-suppression, pH value, composition of mobile phase

Zirconium-based MOF nanocrystals confined on amphoteric halloysite nanotubes for promoting the catalytic hydrolysis of an organophosphorus nerve agent simulant.

Exploiting efficient and practical catalysts for hydrolyzing organophosphorus nerve agents is significant and highly desirable. Herein, a new class of self-detoxifying composites, namely, halloysite nanotubes@NU-912 (HNTs@NU-912), HNTs@NU-912-I and HNTs@UiO-66-NH2, is constructed by in situ synthesis of hexanuclear zirconium cluster-based metal-organic frameworks (Zr-MOFs) NU-912, NU-912-I and UiO-66-NH2, respectively, with HNTs, which are natural nanotubular materials consisting of Si-O-Si tetrahedral sheets on the outer surface and Al-OH octahedral sheets on the inner surface. The results show that crystalline Zr-MOFs uniformly cover the outer surface of HNTs and the particle size of Zr-MOFs is greatly reduced to less than 50 nm. Furthermore, HNTs@NU-912, HNTs@NU-912-I and HNTs@UiO-66-NH2 display much higher catalytic efficiency for the hydrolysis of dimethyl-4-nitrophenyl phosphate (DMNP) than the corresponding Zr-MOFs both in an aqueous N-ethylmorpholine (NEM) buffer solution and under ambient conditions. Specifically, HNTs@NU-912-I shows a turnover frequency (TOF) of 0.315 s-1 in aqueous buffer solution, placing it among the best Zr-MOF-based heterogeneous catalysts for the hydrolysis of DMNP. The composites show high stability, and more importantly, can replace the buffer solvent and control the pH to a certain degree by virtue of its acidic Si-O-Si sheets and alkaline Al-OH sheets. This work provides a certain reference for the subsequent development of personal protective equipment.

The preservation of sarin and O,O'-diisopropyl fluorophosphate inside coordination cage hosts.

The host-guest chemistry of O,O'-diisopropyl fluorophosphate (DFP), a phosphonofluoridate G-series chemical warfare agent simulant, was investigated in the presence of a number of octanuclear cubic coordination cage hosts. The aim was to demonstrate cage-catalysed hydrolysis of DFP at near neutral pH: however, two octanuclear coordination cages, HPEG (containing water-solubilising PEG groups) and HW (containing water-solubilising hydroxymethyl groups), were actually found to increase the lifetime of DFP in aqueous buffer solution (pH 8.7). Crystallographic analysis of DFP with a structurally related host cage revealed that DFP binds to windows in the cage surface, not in the internal cavity. The phosphorus-fluorine bond is directed into the cavity rather than towards the external environment, with the cage/DFP association protecting DFP from hydrolysis. Initial studies with the chemical warfare agent (CWA) sarin (GB) with HPEG cage in a buffered solution also showed a drastically reduced rate of hydrolysis for sarin when bound in the host cage. The ability of these cages to inhibit hydrolysis of these P-F bond containing organophosphorus guests, by encapsulation, may have applications in forensic sample preservation and analysis.

Controlling DNA nanodevices with light-switchable buffers.

Control over synthetic DNA-based nanodevices can be achieved with a variety of physical and chemical stimuli. Actuation with light, however, is as advantageous as difficult to implement without modifying DNA strands with photo-switchable groups. Herein, we show that DNA nanodevices can be controlled using visible light in photo-switchable aqueous buffer solutions in a reversible and highly programmable fashion. The strategy presented here is non-invasive and allows the remote control with visible light of complex operations of DNA-based nanodevices such as the reversible release/loading of cargo molecules.

Development and characterization of the freeze-thaw and oxidative stability of edible rice bran wax-gelatin biphasic gels

Edible biphasic gels with high lipid fractions (>50%) were developed and characterized for their freeze-thaw and lipid oxidation stability. Gels consisted of gelatin in aqueous buffer (hydrogel; HG), and rice bran wax (RBW) in high-oleic soybean oil (oleogel; OG). Freeze-thaw stability was studied by rheology, liquid loss measurement, and microstructural characterization of the gels before and after one freeze-thaw cycle. Biphasic gels were stored for 6 months under accelerated oxidation conditions to assess oxidative stability through peroxide value (PV) analysis. Biphasic gels led to superior systems compared to control OG and HG. The storage modulus (G′) increased with increasing OG. Yield stress (σ*) for biphasic gels were greater than for OG alone, and σ*increased as the proportion of HG increased. Micrographs of biphasic gels showed OG-in-HG matrix for all gels, including those of >50% OG. After one freeze-thaw cycle, biphasic gels had less total liquid loss by approximately 50% compared to the controls and showed an increase in G′. No samples were rancid after the storage period, as demonstrated by the low PV (<3 meq/kg). Changing the ratio of OG:HG for this biphasic gel demonstrates the potential to design semi-solid fat replacers of desired properties with good overall physico-chemical stability.

Effective Production of Selected Dioxolanes by Sequential Bio- and Chemocatalysis Enabled by Adapted Solvent Switching.

Most combinations of chemo- and biocatalysis take place in aqueous media or require a solvent change with complex intermediate processing. Using enzymes in the same organic solvent as the chemocatalyst eliminates this need. Here, it was shown that a complete chemoenzymatic cascade to form dioxolanes could be carried out in a purely organic environment. The result, including downstream processing, was compared with a classical mode, shifting solvent. First, a two-step enzyme cascade starting from aliphatic aldehydes to chiral diols (3,4-hexanediol and 4,5-octanediol) was run either in an aqueous buffer or in the potentially biobased solvent cyclopentyl methyl ether. Subsequently, a ruthenium molecular catalyst enabled the conversion to dioxolanes [e. g., (4S,5S)-dipropyl-1,3-dioxolane]. Importantly, the total synthesis of this product was not only highly stereoselective but also based on the combination of biomass, CO2 , and hydrogen, thus providing an important example of a bio-hybrid chemical.