DMSO-water Mixtures Research Articles

Synthesis, characterization, and application of pyrene-based chalcones AIEgens for cellular and intracellular activity

Herein, we described the design and synthesis of MAN-Br, MAN-I and MAN-OH, a novel pyrene-based chalcones with aggregation induced emission (AIE), DFT, and cellular imaging properties. MAN-Br, and MAN-I exhibited AIE in DMSO-water mixture and this was confirmed by fluorescence spectroscopy studies. These three compounds MAN-Br, MAN-I and MAN-OH was investigated by computational analysis in which their HUMO-LUMO, optimized geometry, molecular electrostatic potential (MEP) are included. The synthesized AIE compound MAN-Br, and MAN-I was found to be non-toxic and promising candidate for biological studies. Cell imaging experiments reveals that MAN-Br, and MAN-I can effectively enhance the signal-to-noise ratio of imaging by reducing the interference from background due to their impressive AIE characteristics. This work will provide guidance for the construction of biological applications on the base of AIE-active compounds, which offers multiple opportunities for multiple clinical applications under hypoxic conditions.

Electrometric Study on Nature and Stability of CoII, NiII and CuII Complexes with 5-Sulfosalicylic Acid in DMSO-Water Mixtures

Electrometric Study on Nature and Stability of CoII, NiII and CuII Complexes with 5-Sulfosalicylic Acid in DMSO-Water Mixtures

Solvent-induced modulation of sensitivity and selectivity in the self-assembly of tetracationic cyclophanes with cholesterol sulphate, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate: Observations of significant shifts

Cyclophane CP-1 demonstrates markedly distinct sensitivities toward Cholesterol sulfate (CH-S), Sodium Dodecyl Sulfate (SDS), and Sodium Dodecyl Benzene Sulfonate (SDBS) when the solvent is shifted minimally from a 95 % to a 98 % HEPES-DMSO mixture. In a 98:2 HEPES-DMSO mixture, CP-1 engages in highly selective self-assembly with CH-S, which is characterized by aggregation-induced emission enhancement (AIEE) in contrast to other steroidal sulfates such as pregnenolone sulfate (PRG-S), dehydroisoandrosterone sulfate (DIAND-S), taurocholic acid (TACH-S), and the surfactants SDS and SDBS. This assembly results in an approximate 40-fold increase in fluorescence intensity with three equivalents of CH-S and allows for the detection of concentrations as low as 200 nM under physiological conditions. Dynamic light scattering (DLS) studies illustrate the aggregation of CP-1 and CH-S, with the zeta potential of each shifting from negative values to nearly zero in a 1:2 CP-1:CH-S mixture, indicating self-assembly. This aggregation behavior is reversible, as demonstrated by a corresponding decrease and then increase in fluorescence intensity with temperature variations from 25 °C to 70 °C and back to 25 °C. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses show that CP-1 forms aggregates ranging from 100 to 180 nm, which increase to 150–250 nm upon interaction with CH-S. In a 95:5 HEPES-DMSO mixture, CP-1 exhibits a stronger AIEE response with SDS and SDBS compared to CH-S. Cyclophane CP-2, when dissolved in binary DMSO-water mixtures with water content exceeding 80 %, shows similar AIEE phenomena and undergoes selective fluorescence quenching with SDS and only a 50 % increase in fluorescence intensity with CH-S, irrespective of the HEPES concentration (95 % or 98 %).

A ‘Turn-on’ fluorogenic probe for selective and specific detection of Hg(II) ions

Mercury (Hg2+) and its associated compounds have drawn serious concern from the scientific communities for their extreme toxicity to human beings. The present article introduced a chromone-benzoxazole embracing an effective fluorogenic probe, (E)-3-(((4-(benzo[d]oxazol-2-yl) phenyl) imino) methyl)-2-methoxy-2H-chromen-4-ol (BPMC) for selective and specific detection of Hg2+ ions having detection and quantification limit in the µM range. A significant photoluminescence enhancement has been observed from BPMC solution (water-DMSO mixture, 50 % v/v) displaying low to highly intense blue-violet photoluminescence under a 365 nm UV lamp due to the inhibition of intramolecular charge transfer (ICT) and excited state intramolecular proton transfer (ESIPT) processes involved in BPMC. Furthermore, to achieve on-site detection of Hg2+ ions and investigate the practical utility of our developed probe, we have fabricated a BPMC-stained paper-strips-based test kit and demonstrated its practical effectiveness for on-spot detection. The details of the detection mechanism have been revealed through 1H NMR, FT-IR, and high-resolution mass spectrometric analysis. The present report evokes a broader perspective for tailoring ICT and ESIPT-based chromo-fluorogenic probes to accelerate their real-world application and environmental monitoring.

Nonlinear composition dependence of hydrogen bond lifetime in water-DMSO binary mixtures: The role of hydrophobic interaction.

The lifetime of a hydrogen bond between water and dimethyl sulfoxide (DMSO) is found to be considerably longer than that between two water molecules in neat water. This is counter-intuitive because the charge on the oxygen in DMSO is considerably less than that in water. Additionally, the strength of the water-dimethyl sulfoxide (w-D) hydrogen bond is found to be strongly composition dependent; the lifetime of the hydrogen bond is ten times larger at 30% than at very low concentrations. Using computer simulations, we perform microscopic structural and dynamic analysis to find that these anomalies arise at least partly from an "action-at-a-distance" effect where the attraction between the hydrophobic methyl groups results in the self-aggregation of DMSO molecules that "cages" both the rotational and linear motions of the molecules involved. This is reflected in the observed strong correlation of the lifetime with the local coordination number of the associated methyl groups. The elongated w-D h-bond lifetime causes a slowdown of collective dynamics and affects the lifetime of the w-w h-bond. This nonlinear feedback mechanism explains the strong composition dependence of viscosity and is anticipated to play a dominant role in many self-assemblies. Furthermore, the w-D hydrogen bond breaking mechanism changes from low to high DMSO concentration, a phenomenon not anticipated a priori. We introduce a new order parameter-based free energy surface of the bond breaking pathway. A two-dimensional transition state rate theory calculation is performed for the lifetime of the w-D h-bond that is found to be semi-quantitatively accurate.

Aggregation-induced emission active multianalyte sensor: Detection of pH, carbonate, bi-carbonate and nitroaromatics in water

An aggregation-induced emission (AIE) based multi-tasking probe DAAQ (5-(dimethylamino)-N-(9,10-dioxo-9,10-dihydroanthracen-2-yl)naphthalene-1-sulfonamide) has been reported for detecting multiple analytes such as anions (carbonate and bicarbonate ions) and nitroaromatic compounds (2,4-DNP and TNP). Probe DAAQ displayed the photophysical properties of aggregation-induced emission (AIE) in DMSO-water mixture, acidochromism and detected various analytes, making DAAQ a multi-tasking probe. DAAQ respond to carbonate and bicarbonate (CO32− and HCO3−) with a colour change from pale yellow to dark orange. The limit of detections (LOD) was estimated as 0.486 mg/L and 41.35 mg/L for CO32− and HCO3−, respectively. The applications of DAAQ were also explored to detect CO32− ions in water samples collected from various sources and soft drinks. Further, the probe also explored detecting neural aromatic compounds such as 2,4-DNP and TNP by a naked eye colour change and the LODs were calculated as 12.6 µM and 8.19 µM, respectively. DFT calculations were applied for the confirmation binding studies of DAAQ with multiple analytes. The sensing of 2,4-DNP and TNP were achieved through PET with a Turn-Off response. The sensing mechanisms were confirmed with 1H NMR experiments.

Agglomeration in dimethyl sulfoxide and water binary System: A comprehensive study through thermodynamics, vibrational spectroscopy, quantum mechanical calculations and morphology

Some nano- or micro-sized agglomerates with different morphologies in the dimethyl sulfoxide (DMSO) and water binary system at different molar fractions were characterized using Scanning Electron Microscope (SEM) and Dynamic Light Scattering (DLS) for the first time. Four fundamental clusters with the composition of [(DMSO)2], [(DMSO)3], [(DMSO)2∙ H2O] and [(DMSO)3∙ H2O] were identified through the combination of quantum mechanical calculations and vibrational spectroscopy. These clusters act as seeds for the growth of agglomerates both in pure DMSO and in DMSO-water binary mixtures. According to SEM images, the morphology of the agglomerates varies with the molar fraction, wherein two main kinds were observed, viz. one growing from the center and spreading out to the surrounding, and the other growing into a chain-like structure. Inter-cluster and/or inter-agglomerate interactions are responsible for the molar fraction dependence of density, viscosity and other related thermodynamic properties. The present work is the first to study the morphology of agglomerates in the DMSO-water binary system and the first to propose the essential roles played by four dominant clusters in the agglomerating process.

Nature and Stability of Co(II), Ni(II) and Cu(II) Complexes with 5-Hydroxysalicylic Acid in DMSO-Water Mixtures: An Electrometric Investigation

The main objective of the present study is to conduct an experiment to analyze the variation of protonation-deprotonation equilibria with regards to the dielectric constants of an organic medium, influence of errors on protonation constants and effect of pH chemical species distribution. The present investigation was carried out by using pH meter, processing of data was done by Gran titration. To obtain best fit chemical models, a modelling strategy such as SCPHD was used and a computer program was used for the refinement of results. In the present study, we studied the influence of dielectric constants of a medium DMSO on stability constants of Co(II), Ni(II) and Cu(II) with 5-hydroxysalicylic acid (5-HSA). The species distribution diagrams were presented. The metal-ligand equilibria of the ligands revealed the calculated statistical parameters such as χ2, skewness, kurtosis and R-factor. Significant influence of co-solvent dimethyl sulfoxide (DMSO)-Water mixtures on the stability constants of metal-ligand complexes was observed.

Controlling Interfacial Hydrogen Bonding at a Gold Surface: The Effect of Organic Cosolvents.

Water often serves as both a reactant and solvent in electrocatalytic reactions. Interfacial water networks can affect the transport and kinetics of these reactions, e.g., hydrogen evolution reaction and CO2 reduction reaction. Adding cosolvents that influence the hydrogen-bonding (H-bonding) environment, such as dimethyl sulfoxide (DMSO), has the potential to tune the reactivity of these important electrocatalytic reactions by regulating the interfacial local environment and water network. We investigate interfacial H-bonding networks in water-DMSO cosolvent mixtures on gold surfaces by using surface-enhanced infrared absorption spectroscopy and molecular dynamics simulations. Experiments and simulations show that the gold surface is enriched with dehydrated DMSO molecules and the mixture phase-separates to form water clusters. Simulations show a "buckled" water conformation at the surface, further constraining interfacial H-bonding. The small size of these water clusters and the energetically unfavorable H-bond conformations might inhibit H-bonding with bulk water, suppressing the proton diffusion required for efficient hydrogen evolution reaction processes.

Polymorphism Dependent Cytotoxicity, Cellular Uptake, and Live Cell Imaging Studies on Napthalimide-Vinyl-Phenothiazine Conjugate.

Polymorphism-dependent cytotoxicity and cellular uptake of drug molecules have been studied for the past two decades. However, the visualization of polymorph-dependent cellular uptake and cytotoxicity using microscopy imaging techniques has not yet been reported. The luminescent polymorph is an ideal candidate to validate the above hypothesis. Herein, we report the polymorph-dependent cellular uptake, cytotoxicity, and bio-imaging functions of polymorphs 1Y and 1R of a naphthalimide-phenothiazine dyad. These polymorphs show different luminescence colors in the solid state and exhibit aggregation-induced enhanced emission (AIEE) in the DMSO-Water mixture. Bioimaging, cytotoxicity assay, and fluorescence-activated cell sorting (FACS) studies revealed that these polymorphs show different levels of cytotoxicity, cellular uptake, localization, and imaging potential. Detailed photophysical, morphological, and biological studies revealed that the difference in molecular conformation in these polymorphs enables them to form aggregates of different sizes and morphology, which leads to the differential uptake of these into the cells and consequently shows different cytotoxicity and imaging potentials.

Ionic Pairing and Selective Solvation of Butylmethylimidazolium Chloride Ion Pairs in DMSO-Water Mixtures: A Comprehensive Examination via Molecular Dynamics Simulations and Potentials of Mean Force Analysis.

Ionic liquids (ILs) with dimethyl sulfoxide (DMSO) and water act as a promising solvent medium for the dissolution of cellulose in an efficient manner. To develop a proper solvent system, it is really important to understand the thermodynamics of the molecular solutions consisting of ILs, DMSO, and water. The ion-pairing propensity of the ILs in the presence of DMSO and water plays a crucial role in governing the property of the solvent mixtures. Employing all-atom molecular dynamics simulations, we estimate the potentials of mean force between BMIM+ and Cl- ions in DMSO-water mixtures. Analysis reveals a significant increase in the thermodynamic stability of both contact ion pair (CIP) and solvent-assisted ion pair (SAIP) states with a rising DMSO mole fraction. Thermodynamic assessments highlight the entropic stabilization of CIP states and SAIP states in pure water, in DMSO-water mixtures, and in pure DMSO. The structural analysis reveals that in comparison to the DMSO local density, the local water density is relatively very high around ion pairs, more specifically in the solvation shell of a chloride ion. Preferential binding coefficients also consistently indicate exclusion of DMSO from the ion pair in DMSO-water mixtures. To enhance our understanding regarding the solvent molecules kinetics around the ion pairs, the survival probabilities of DMSO and water are computed. The calculations reveal that the water molecules prefer a prolonged stay in the solvation shell of Cl- ions.

Water sensitive fluorescence tuning of V-shaped ESIPT fluorophores: Substituent effect and trace amount water sensing in DMSO

Highly sensitive nature of excited state intramolecular proton transfer (ESIPT) functionality in organic fluorophores made them potential candidates for developing environmental sensors and bioimaging applications. Herein, we report the synthesis of V-shaped Dapsone based Schiff base ESIPT derivatives (1–3) and water sensitive wide fluorescence tuning from blue to red in DMSO. Solid-state structural analysis confirmed the V-shaped molecular structure with intramolecular H-bonding and substituent dependent molecular packing in the crystal lattice. 1 showed strong solid-state fluorescence (λmax = 554 nm, Φf = 21.2 %) whereas methoxy substitution (2 and 3) produced tunable but significantly reduced fluorescence (λmax = 547 (2) and 615 nm (3), Φf = 2.1 (2) and 6.5 % (3)). Interestingly, aggregation induced emission (AIE) studies in DMSO-water mixture revealed water sensitive fluorescence tuning. The trace amount of water (less than 1 %) in DMSO converted the non-emissive 1–3 into highly emissive state due to keto tautomer formation. Further increasing water percentage produced deprotonated state of 1–3 in DMSO and enhanced the fluorescence intensity with red shifting of emission peak. At higher water fraction, 1–3 in DMSO produced aggregates and red shifted the emission with reduction of fluorescence intensity. The concentration dependent fluorescence study revealed the very low detection limit of water in DMSO. The limit of detection (LOD) of 1, 2 and 3 were 0.14, 1.04 and 0.65 % of water in DMSO. Hence, simple Schiff bases of 1–3 showed water concentration dependent keto isomer, deprotonated and aggregated state tunable fluorescence in DMSO. Further, scanning electron microscopic (SEM) studies of 1–3 showed water concentration controlled self-assembly and tunable fluorescence.

Synthesis of a Series of Trimeric Branched Glycoconjugates and Their Applications for Supramolecular Gels and Catalysis.

Carbohydrate-derived molecular gelators have found many practical applications as soft materials. To better understand the structure and molecular gelation relationship and further explore the applications of sugar-based gelators, we designed and synthesized eight trimeric branched sugar triazole derivatives and studied their self-assembling properties. These included glucose, glucosamine, galactose, and maltose derivatives. Interestingly, the gelation properties of these compounds exhibited correlations with the peripheral sugar structures. The maltose derivative did not form gels in the tested solvents, but all other compounds exhibited gelation properties in at least one of the solvents. Glucose derivatives showed superior performance, followed by glucosamine derivatives. They typically formed gels in toluene and alcohols; some formed gels in ethanol-water mixtures or DMSO water mixtures. The glycoclusters 9 and 10 demonstrated rate acceleration for the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. These were further studied for their metallogels formation properties, and the copper metallogels from compound 9 were successfully utilized to catalyze click reactions. These metallogels were able to form a gel column, which was effective in converting the reactants into the triazole products in multiple cycles. Moreover, the same gel column was used to transform a second click reaction using different reactants. The synthesis and characterization of these compounds and their applications for catalytic reactions were discussed.

Spectroscopic behavior differences between lumazine and alloxazine in the DMSO-water mixture

The absorption and emission spectra were investigated for lumazine, alloxazine and their cyanated or fluorinated derivatives, respectively. The spectroscopic properties were modulated by varying water concentration in dimethyl sulfoxide (DMSO). Some intriguing experimental results were found for the samples containing 65 % of water and 35% of DMSO. This finding is consistent with previously published molecular dynamics (MD) simulations confirming the concept of the ‘local bulk’ model. In this case, a notable decrease in absorption and emission intensities was registered, even larger than the water quenching observed in other cases. The changes in midrange DMSO concentrations could be explained by the formation of local solvents structures as predicted by MD, specifically the formation of DMSO·2H2O dimers. Experimentally, the cyano-substituted lumazine has shown a remarkable sensitivity to DMSO concentration. The spectroscopic measurements were interpreted using the density functional theory where the implicit DMSO solvent model was combined with explicit water molecules. Together with its enhanced water solubility, the cyanated lumazine derivate could be used for non-destructive DMSO detection in vitro for applications such as drug uptake monitoring, since DMSO is often used in pharmaceutical practice.

Design, synthesis, and applications of pyrene-quinoline based cell-permeable AIEgen for cellular imaging and antibacterial activity

Herein, we describe the design and synthesis of PyQ, a novel pyrene-quinoline based cell-permeable aggregation-induced emission luminogen (AIEgen) with implications in cellular imaging and antibacterial activity. The synthesised compound was characterised by NMR, HR-MS and IR studies. PyQ exhibited AIE in the DMSO-water mixture and this was confirmed by fluorescence spectroscopic studies. The addition of water to the DMSO solution of PyQ resulted in enhanced fluorescence emission for up to 70% water in DMSO. The SEM and TEM data also confirmed the aggregate formation in addition to DLS, quantum yield and lifetime measurements. The synthesised AIE compound was found to be non-toxic and cell-permeable that could readily label the cytoplasm and plasma membrane. Of note, PyQ exhibited both blue and green emission inside the cell. We further evaluated the antibacterial activity of PyQ aggregates against the model Gram-negative bacteria, Escherichia coli (E. coli) using the standard colony forming unit (CFU) counting assay. The results suggest that the aggregates were potent antibacterial agents and the SEM data clearly showed the disruption of the bacterial membrane. Taken together, this work provides a simple and efficient technique for the development of an AIEgen with antibacterial activity as well as rapid cellular imaging with both blue and green emission.

Effect of hydrogen bonding on the mixing behaviour of ternary aqueous mixtures

This study correlates the solution behaviour of an aqueous mixture to hydrogen bonding between its three components (water, liquid Pluronic L31 and either tetrahydrofuran, THF or dimethyl-sulfoxide, DMSO). Pluronic L31 is miscible in either THF, DMSO or water, but separates from ternary mixtures, at specific solvent to water ratios. Water species can either donate a single (SD) or two hydrogens (DD), and accept a single (SA) or two (DA) hydrogens, depending on the other components in the mixture. This is reflected in the OH stretch band, as probed using attenuated total reflectance-Fourier transform infrared spectroscopy. Pluronic L31 and THF both compete for hydrogen bonding with DD-DA, with up to 30% THF (v/v, relative to water), where separation occurs. Above 30% THF, Pluronic L31 and THF do not compete for the same water species and mix freely. Pluronic L31 separates from DMSO-water mixtures with 10–80% DMSO. Competition for similar water species explains separation up to 50% DMSO. Above 50% DMSO, we must also consider two-way interactions between all components. At low DMSO concentrations, DMSO mainly interacts with water trough the SO group, while methyl groups from DMSO can interact with Pluronic L31. At higher DMSO contents, the methyl groups of DMSO interact more markedly with water. The second derivative of the νasCH3 peak displays a split with ≤ 50% DMSO, which disappears at higher DMSO percentages. The four peaks in the second derivative of the of the νasCH3 peak correlate to the interactions between DMSO and the four water species.

Water-DMSO Co–Solvent effect and kinetics of acid catalyzed Hydrolysis of butyl formate and Influence on Activation Parameters

The acid catalyzed hydrolysis of butyl formate in presence of 0.1N-HCI in water and the presence of water-DMSO mixture containing up to 30-70% (v/v) was studied over the temperature ranging from 20-400C. The rate of reaction decreases with decrease of water content of the solvent mixture and reached minima at about 70% of organic solvent. The number of water molecule associated with activated complex was showing decrease in trend with increase of temperature, is an indication of change in mechanism from unimolecular to bimolecular in reaction media. The parameters of thermodynamic activation were also calculated and discussed in terms of solvent effect with help of plots of ΔH* versus ΔS*, the isokinetic temperature was calculated and found to be greater than 300.

2D-IR Spectroscopy of Nitrosyl Stretch of Sodium Nitroprusside Reveals the Elusive Two Anomalous Regions in the DMSO–Water Mixture

DMSO-water mixtures provide an intriguing hydrogen-bonding environment which has been a subject of various theoretical and experimental investigations. The structural dynamics of aqueous DMSO solutions has been investigated, using nitrosyl stretch of sodium nitroprusside (SNP, Na2[Fe(CN)5NO]) as a local vibrational probe, with the help of infrared (IR) absorption spectroscopy, vibrational pump-probe spectroscopy, and two-dimensional IR spectroscopy (2D-IR). Fourier transform infrared spectra of the nitrosyl stretch of SNP reveals that both the peak position and spectral broadening are very sensitive to the composition of the DMSO-water mixture and the subsequent structural changes occurring due to the addition of DMSO to water. The vibrational lifetime of the nitrosyl stretch displays two different linear variation regimes as a function of mole fraction of DMSO which has been assigned presumably to two different predominant structures at these compositions. However, the rotational depolarization measurements show that the reorientational times follow a bell-shaped profile, imitating the changes in the composition-dependent physical properties (viscosity) of DMSO-water solvent mixtures. To get a holistic picture of the system, 2D-IR spectroscopy of the NO stretch of SNP has been employed to study time scales of hydrogen-bond reorganization dynamics existing at different compositions. The analysis of frequency-frequency correlation function (FFCF) decay times reveal that the dynamics gets slower in intermediate DMSO concentrations than that of pure DMSO or pure water. A careful analysis reveals two anomalous regions of hydrogen-bond dynamics: XDMSO ∼0.2 and 0.4, which indicates that different hydrogen-bonded structures exist in these regions that can be effectively probed by SNP which has remained mostly elusive to previous vibrational probe-based investigations.

Metal-organic framework nanopesticide carrier for accurate pesticide delivery and decrement of groundwater pollution

The motivation of the present study was a synthesis of the nanocomposites of UiO-66@ZnO/Biochar to embed carbendazim (CBZ) pesticide inside its porous structures for smart spraying and cleaner production. CBZ@UiO-66@ZnO/Biochar had the purpose of not only smart spraying to avoid releasing a large amount of CBZ into the groundwater but also of accurately delivering the CBZ pesticide to the desired grass/plant. High-resolution electron microscopy was introduced to characterise the morphologies of prepared composites with spatial elemental distribution mapping. X-ray diffraction (XRD) patterns and micro-Raman spectroscopy were employed for the crystal structures of UiO-66@ZnO. Spectral UV–Vis and Fourier transform-infrared (FT-IR) tools were utilized to estimate the UiO-66@ZnO/Biochar-based adsorption and release of CBZ into the dimethyl sulfoxide (DMSO)-water mixture. Our results indicated that the adsorption capacities of CBZ into the DMSO-water mixture onto UiO-66@ZnO and UiO-66@ZnO/Biochar nanocomposites were obtained at 68.8% and 72.6%. The half-life of photodegradation rate constants for CBZ@UiO-66@ZnO/Biochar was found to be 12.3 times longer than that of free CBZ. Notably, CBZ@UiO-66@ZnO/Biochar inhibitory concentration 50% (IC50) determination was estimated at 73.8 μg/L and 209 μg/L for Fusarium oxysporum and Aspergillus niger. This work provides a comprehensive experimental scheme for the chemisorption process of CBZ onto the UiO-66@ZnO/Biochar composite materials and the nanopesticide applications in sustainable agriculture towards cleaner productions.

Cosolvent effects on the structure and thermoresponse of a polymer brush: PNIPAM in DMSO–water mixtures

Structural characterisation of thermoresponsive polymer brushes in binary DMSO–water mixtures reveals both LCST and UCST behaviour.