Cholate Solution Research Articles

Collection of Partition Coefficients in Hexadecyltrimethylammonium Bromide, Sodium Cholate, and Lithium Perfluorooctanesulfonate Micellar Solutions: Experimental Determination and Computational Predictions.

This study focuses on determining the partition coefficients (logP) of a diverse set of 63 molecules in three distinct micellar systems: hexadecyltrimethylammonium bromide (HTAB), sodium cholate (SC), and lithium perfluorooctanesulfonate (LPFOS). The experimental log p values were obtained through micellar electrokinetic chromatography (MEKC) experiments, conducted under controlled pH conditions. Then, Quantum Mechanics (QM) and machine learning approaches are proposed for the prediction of the partition coefficients in these three micellar systems. In the applied QM approach, the experimentally obtained partition coefficients were correlated with the calculated values for the case of the 15 solvent mixtures. Using Density Function Theory (DFT) with the B3LYP functional, we calculated the solvation free energies of 63 molecules in these 16 solvents. The combined data from the experimental partition coefficients in the three micellar formulations showed that the 1-propanol/water combination demonstrated the best agreement with the experimental partition coefficients for the SC and HTAB micelles. Moreover, we employed the SVM approach and k-means clustering based on the generation of the chemical descriptor space. The analysis revealed distinct partitioning patterns associated with specific characteristic features within each identified class. These results indicate the utility of the combined techniques when we want an efficient and quicker model for predicting partition coefficients in diverse micelles.

Liquid Phase Exfoliation of Rubrene Single Crystals into Nanorods and Nanobelts.

Liquid phase exfoliation (LPE) is a popular method to create dispersions of two-dimensional nanosheets from layered inorganic van der Waals crystals. Here, it is applied to orthorhombic and triclinic single crystals of the organic semiconductor rubrene with only noncovalent interactions (mainly π-π) between the molecules. Distinct nanorods and nanobelts of rubrene are formed, stabilized against aggregation in aqueous sodium cholate solution, and isolated by liquid cascade centrifugation. Selected-area electron diffraction and Raman spectroscopy confirm the crystallinity of the rubrene nanorods and nanobelts while the optical properties (absorbance, photoluminescence) of the dispersions are similar to rubrene solutions due to their randomized orientations. The formation of these stable crystalline rubrene nanostructures with only a few molecular layers by LPE confirms that noncovalent interactions in molecular crystals can be strong enough to enable mechanical exfoliation similar to inorganic layered materials.

Investigating the synergistic initiating effect on promoting methane hydrate formation via mixed graphene and sodium cholate

Gas hydrate is viewed as a promising form to store and transport methane, while the sluggish formation kinetics limits its large-scale utilization. Recently, many nanomaterials have been reported to accelerate the formation of methane hydrate, but their performance is difficult to satisfy the practical application. Additionally, the promoting mechanism of the nanomaterials is yet to be figured out. Here we studied the effect of graphene and sodium cholate on methane hydrate formation. Graphene and sodium cholate show a synergistic effect on methane hydrate formation, corresponding to the induction time halved in the mixture of them than sodium cholate solution. This acceleration was achieved by the increase of intermediate water (IW) induced by the added graphene. IW has the potential to accelerate the nucleation of methane hydrate based on its partial hydrogen-bonded structure. Meanwhile, the mixture of graphene and sodium cholate express excellent recycling stability during the repeated methane hydrate formation − dissociation. The insight of this study can apply to develop high-efficiency kinetic additives for methane hydrate.

Effect of Maltodextrin and Temperature on Micellar Behavior of Bile Salts in Aqueous Medium: Conductometric and Spectrofluorimetric Studies

Abstract Conductivity and fluorescence probe techniques have been employed to study the micellar behavior of bile salts i.e. sodium cholate (1–20 mmol⋅kg−1) and sodium deoxycholate (0.5–10.0 mmol⋅kg−1) in aqueous solutions of maltodextrin (0.0, 0.5, 1.1, and 1.6 mmol⋅kg−1) at different temperatures. The influence of maltodextrin on the micellization behavior of bile salts has been determined in terms of critical micelle concentration (CMC) values obtained from conductivity measurement. The variation in CMC values has been discussed by considering the alteration in the hydrophobic environment of maltodextrin-sodium cholate/sodium deoxycholate complex imparted by the carbohydrate molecules. In order to substantiate the CMC values determined from conductivity method, the fluorescence probe study of aqueous sodium cholate and sodium deoxycholate solutions in presence of fluorescent, pyrene has also been carried. The CMC values obtained from both techniques are in full agreement with each other. Moreover, application of charged pseudo-phase separation model has been made to discuss the thermodynamics of the system.

Quantitative 31P NMR Method for Individual and Concomitant Determination of Phospholipid Classes in Polar Lipid Samples.

Herein, to achieve individual and concomitant quantifications of phospholipid classes, an absolute quantification 31P NMR method using an internal standard was examined. Phospholipid standards and dietary foods were dispersed to prepare test solutions in an anionic surfactant (sodium cholate) solution containing EDTA, as a modification based on a reported method. Each phospholipid class showed a reproducible chemical shift at a near-neutral test solution pH of 6.90±0.04 and temperature of 30.0±0.1°C. The quantity of synthetic phosphatidylcholine measured using 31P NMR was consistent with that measured by 1H NMR using an internal standard. As the principal phospholipid class of soybean and egg yolk lecithin is phosphatidylcholine, the measurement conditions of 31P NMR (pulse interval time and number of scans) were optimized such that minor phospholipids, including lysophospholipids, also present in lecithin could be quantified simultaneously. Phospholipid classes in commercial polar lipid samples derived from porcine brain, yeast, and soybean were individually quantified using the above conditions. Using phosphoserine as the internal standard material allowed the absolute molar quantity of the phospholipid class to be precisely determined with traceability to the SI. The determined molar amounts of phospholipid classes were then translated to the weight amount by assuming that each phospholipid class contained two stearic acid molecules as the constituent fatty acid. The calculated total contents of each phospholipid class by 31P NMR were in good agreement with those obtained by molybdenum blue colorimetry. Furthermore, the quantitative values of the principal phospholipid classes in the polar lipid samples obtained by 31P NMR corresponded in a broad view, however, was more informative for the separation of individual phospholipid species rather than the quantitative 2D thin-layer chromatography.

Spectral Inhomogeneities in Swcnts Sorted By Nonlinear Dgu

Single-walled nanotubes are widely studied nanomaterials because of their unusual properties and potential applications. Unfortunately all practical current growth methods produce nanotubes with a variety of (n,m) structures and therefore physical properties. This inhomogeneity hinders some studies and applications in which samples with a single structure or a narrow range of structures are needed. To date, a number of sorting methods have been introduced to separate single-walled from multi-walled nanotubes, individualized from aggregated, metallic from semiconducting, water-filled from empty, and even right-handed from left-handed forms of the same (n,m) SWCNT species. Nonlinear density gradient ultracentrifugation (nDGU) separation has been shown to be one of the most selective tools for preparing high purity SWCNT samples. However, there has been little study of whether nDGU fractions actually are highly homogeneous. We have analyzed such fractions and find that layers containing enantiomers of individual (n,m) species show unexpected spectral inhomogeneities. Each enantiomeric layer of (6,5) SWCNTs was extracted into three or four 48 µL fractions using a custom-built high precision automated fractionator. These extracted fractions were analyzed for their fluorescence and absorption spectra. They were then diluted into sodium cholate solution to provide uniform coatings, and the spectral measurements were repeated along with determinations of their absolute fluorescence quantum yields and measurements of variance spectra. The undiluted fractions within a single layer showed significant differences in spectral peak position and line width. Dilution reduced these inhomogeneities and caused ca. 50 cm-1 blue shifts in E11 peak positions for the upper enantiomer band but only 5 cm-1 shifts for the lower one. Emission line widths were also decreased substantially and quantum yields increased by a factor of ca. 2. Nevertheless, the diluted fractions gave quantum yields of 0.8 ± 0.1% and varied by a factor of 1.5 within the lower layer. They reached a maximum of approximately 1%, which is similar to that for SWCNTs wrapped by PFO in toluene. Further insight was obtained from variance spectral data, which confirmed the differences in emission per nanotube within layers and revealed that the low frequency wing of the E11 emission band of each fraction results from inhomogeneous broadening. Our results show that even the use of a highly selective SWCNT sorting method may not ensure spectroscopic homogeneity within the separated samples.

Interaction Potency of Single-Walled Carbon Nanotubes with DNAs: A Novel Assay for Assessment of Hazard Risk.

Increasing use of single-walled carbon nanotubes (SWCNTs) necessitates a novel method for hazard risk assessment. In this work, we investigated the interaction of several types of commercial SWCNTs with single-stranded (ss) and double-stranded (ds) DNA oligonucleotides (20-mer and 20 bp). Based on the results achieved, we proposed a novel assay that employed the DNA interaction potency to assess the hazard risk of SWCNTs. It was found that SWCNTs in different sizes or different batches of the same product number of SWCNTs showed dramatically different potency of interaction with DNAs. In addition, the same SWCNTs also exerted strikingly different interaction potency with ss- versus ds- DNAs. The interaction rates of SWCNTs with DNAs were investigated, which could be utilized as the indicator of potential hazard for acute exposure. Compared to solid SWCNTs, the SWCNTs dispersed in liquid medium (2% sodium cholate solution) exhibited dramatically different interaction potency with DNAs. This indicates that the exposure medium may greatly influence the subsequent toxicity and hazard risk produced by SWCNTs. Based on the findings of dose-dependences and time-dependences from the interactions between SWCNTs and DNAs, a new chemistry based assay for hazard risk assessment of nanomaterials including SWCNTs has been presented.

Production of well dispersible single walled carbon nanotubes via a “floating catalyst”-method

In this paper, we present a unique process chain for the production of single-walled carbon nanotubes (SWCNT) and document the relationship between the process parameters in gas phase production, the dispersibility of SWCNTs in aqueous solutions of sodium cholate and their properties. SWCNTs were prepared by a “floating catalyst” method using a solution of ferrocene in ethanol as precursor. Production rates in the range from 5 to 20mg/h were achieved by using an optimized riser reactor design, which enables reduction of undesired wall-sticking of the catalyst particles and SWCNTs. Products featuring iron catalyst contents less than 30wt% were obtained for low precursor concentrations in combination with short residence time in the reactor. Transmission electron microscopy (TEM) and statistical Raman analyses of the products reveal that the SWCNTs exhibit a diameter distribution ranging from 0.5 to 2.0nm. Processing conditions, including precursor concentration, residence time, etc. were found to have only a slight impact on the mean geometric SWCNT diameter. Sonication based post-processing of the as-prepared SWCNTs in aqueous solutions of sodium cholate leads to an effective individualization of SWCNTs as proven by atomic force microscopy (AFM), 3D fluorescence spectroscopy, and by multi-wavelength analytical ultracentrifugation (AUC). Overall, the dispersibility of the non-purified SWCNTs in a 2wt% aqueous solution of sodium cholate increases as the ferrocene partial pressure is decreased and, in turn, the catalyst concentration is reduced in the gas phase. Statistical Raman spectroscopy performed with the SWCNTs reveals that more than 75% of the produced carbon species are SWCNTs and that about 2/3 are semiconducting.

Purification of Carbon Nano-Onions Fabricated by Arc Discharge

Soot containing carbon nano-onions was synthesized by traditional electric arc-discharge method with nickel powder as catalyst. After heating at 400°C for 2 h, the arc discharged soot was soaked in hydrochloric acid solution 8 h, and then ultrasonically dispersed into sodium cholate solution. Such obtained dispersion was filtrated with a medium-speed filter paper, and the filtrate was further filtered with a 0.2 μm polytetrafluoroethylene membrane to collect the purified carbon nano-onions. SEM (scanning electron microscope) and TEM (transmission electron microscope) observation showed that carbon nano-onions with hollow or nickel-encapsulated cavities were observed and they had a wide size distribution with an averaged diameter of 24.4 nm. XRD (X-ray diffraction) and Raman scattering investigations evidenced a high degree graphitization of such obtained carbon nano-onions. The XPS (X-ray photoemission spectroscopy) analysis, survey to surface chemistry, demonstrated that oxygen-containing and nitrogen-containing functional groups and the metal catalyst were removed from the surface of carbon nano-onions after purification.

Effect of the Structure and Morphology of Natural, Synthetic and Post-processed Graphites on Their Dispersibility and Electronic Properties

Twenty-two different graphite grades of the families natural, synthetic, intercalated, expanded, amorphous, and turbostratic graphite, as well as platelets and activated carbon, were analyzed on their dispersibility in N-methylpyrrolidone, cyclohexylpyrrolidone and water-sodium cholate solution. They were characterized for their properties (grain size, density, purity, surface area, pH in water) and morphology. Thermogravimetric analysis, Raman spectroscopy studies, and electrical conductivity measurements were also used. XRPD followed by a Rietveld refinement provided information on the amounts of the rhombohedral (3R) and hexagonal (2H) phases for the crystalline part of the material and the interlayer distances. The properties of graphites favoring better dispersibility are: small grain size and bulk density, neutral pH in water. The electrical conductivity in inversely proportional to the Raman D-band intensity and is highest for the graphites with shortest interlayer spacing. The D-, G- and 2D-bands in the Raman spectra of graphites are in an exponential relation.

Analyzing Surfactant Structures on Length and Chirality Resolved (6,5) Single-Wall Carbon Nanotubes by Analytical Ultracentrifugation

The structure and density of the bound interfacial surfactant layer and associated hydration shell were investigated using analytical ultracentrifugation for length and chirality purified (6,5) single-wall carbon nanotubes (SWCNTs) in three different bile salt surfactant solutions. The differences in the chemical structures of the surfactants significantly affect the size and density of the bound surfactant layers. As probed by exchange of a common parent nanotube population into sodium deoxycholate, sodium cholate, or sodium taurodeoxycholate solutions, the anhydrous density of the nanotubes was least for the sodium taurodeoxycholate surfactant, and the absolute sedimentation velocities greatest for the sodium cholate and sodium taurodeoxycholate surfactants. These results suggest that the thickest interfacial layer is formed by the deoxycholate, and that the taurodeoxycholate packs more densely than either sodium cholate or deoxycholate. These structural differences correlate well to an observed 25% increase in fluorescence intensity relative to the cholate surfactant for deoxycholate and taurodeoxycholate dispersed SWCNTs displaying equivalent absorbance spectra. Separate sedimentation velocity experiments including the density modifying agent iodixanol were used to establish the buoyant density of the (6,5) SWCNT in each of the bile salt surfactants; from the difference in the buoyant and anhydrous densities, the largest hydrated diameter is observed for sodium deoxycholate. Understanding the effects of dispersant choice and the methodology for measurement of the interfacial density and hydrated diameter is critical for rationally advancing separation strategies and applications of nanotubes.

Investigation of the Mechanism of Temperature-Responsiveness of Metal-Cholate Supramolecular Hydrogels

Temperature-promoted hydrogel formation was investigated in a mixed solution of sodium cholate and metal ions. Transmission electron microscopy (TEM) was used to characterize the morphology of the microstructures of the hydrogels, and nanofibers were observed. The arrangement of the cholate and metal ions was proposed according to the X-ray diffraction (XRD) measurements. Rheological measurements revealed that the strength of the hydrogels increases with increasing temperature, while the fluorescence of the gels increased as well. Increasing the temperature also increased the gel formation rate. The critical micelle concentration of sodium cholate solution decreased slightly with increasing temperature. On the basis of the experimental results, we propose that the increased hydrophobicity of cholate ions with increasing temperature leads to stronger hydrogen bonding between cholate ions, which accounts for the unique heating-enhanced gelation behavior.

Metal cholate hydrogels: versatile supramolecular systems for nanoparticle embedded soft hybrid materials

This work describes the formation of hydrogels from sodium cholate solution in the presence of a variety of metal ions (Ca2+, Cu2+, Co2+, Zn2+, Cd2+, Hg2+ and Ag+). Morphological studies of the xerogels by electron microscopy reveal the presence of helical nanofibres. The rigid helical framework in the calcium cholate hydrogel was utilised to synthesize hybrid materials (AuNPs and AgNPs). Doping of transition metal salts into the calcium cholate hydrogel brings out the possibility of synthesising metal sulphide nano-architectures keeping the hydrogel network intact. These novel gel–nanoparticle hybrid materials have encouraging application potentials.

Effects of Micelle Properties on the Conformation of Oligocholates and Importance of Rigidity of Foldamers

The conformation of a cholate hexamer with a clicked tether in between two tricholate units and pyrene groups at the chain ends was studied by fluorescence spectroscopy. In contrast to the parent cholate hexamer that folded in all micelles investigated, the folding of the clicked hexamer was highly dependent on the type of surfactant used to solubilize the compound. The clicked oligocholate folded in the Brij 35 micelle, possibly due to the latter's small size and strong internal hydrophobicity. The oligocholate formed intermolecular aggregates in SDS solutions below the CMC of the surfactant. The aggregates were dissociated by the SDS micelles but the individual oligocholate stayed unfolded. In Triton X-100 and sodium cholate solutions, the aggregated, unfolded, and folded oligocholates coexisted and gradual unfolding occurred with an increasing concentration of the surfactant. The conformation of the clicked oligocholate was sensitive to the nonideal mixing of ionic/nonionic micelles and to the unconventional aggregation of sodium cholate.

Antimicrobial Activity of Single-Walled Carbon Nanotubes Suspended in Different Surfactants

We investigated the antibacterial activity of single-walled carbon nanotubes (SWCNTs) dispersed in surfactant solutions of sodium cholate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate. Among the three surfactants, sodium cholate demonstrated the weakest antibacterial activity againstSalmonella enterica,Escherichia coli, andEnterococcus faeciumand thereby was used to disperse bundled SWCNTs in order to study nanotube antibiotic activity. SWCNTs exhibited antibacterial characteristics for bothS. entericaandE. coli. With the increase of nanotube concentrations from 0.3 mg/mL to 1.5 mg/mL, the growth curves had plateaus at lower absorbance values whereas the absorbance value was not obviously affected by the incubation ranging from 5 min to 2 h. Our findings indicate that carbon nanotubes could become an effective alternative to antibiotics in dealing with drug-resistant and multidrug-resistant bacterial strains because of the physical mode of bactericidal action that SWCNTs display.

Synthesis of Graphene Layers Using Graphite Dispersion in Aqueous Surfactant Solutions

Graphene layers were synthesized using ultrasonic dispersion of graphite flakes followed by ultracentrifugation in sodium cholate and polyoxyethylene nonylphenyl ether aqueous solutions. The synthesized graphene layers were characterized using Raman spectroscopy and atomic force microscopy (AFM). Typical G-band and 2D-band Raman signatures of graphene at ∼1590 cm−1 and ∼2695 cm−1, respectively, were observed in the Raman spectra of the synthesized graphene samples. The AFM height profiles of the synthesized graphene samples on SiO2 substrates show features that can be attributed to graphenes of a single layer or a few layers.

In Situ FTIR ATR Spectroscopic Study of the Interaction of Immobilized Human Serum Albumin with Cholate in Aqueous Environment

Fourier transform infrared (FTIR) attenuated total reflection (ATR) spectroscopy is increasingly used for the investigation of processes at or near interfaces. Exposing HSA dissolved in phosphate buffered saline (PBS) to a clean germanium (Ge) multiple internal reflection element (MIRE) led to the formation of a stable compact monolayer with a surface concentration of (5.31 ± 0.49) × 10−12 mol cm−2. Using a flow-through cuvette enabled in situ the monitoring of the HSA layer preparing and the interaction of this layer with a 5 mM solution of cholate in PBS. In order to achieve optimum sensitivity, two enhanced spectroscopic techniques have been applied: single-beam-sample-reference (SBSR) technique and concentration-modulated excitation (c-ME). Solutions of cholate and pure PBS were pumped alternatively with frequency ω through the sample compartment containing the immobilized HSA monolayer. Spectral changes due to interaction between cholate and HSA were now marked by the same frequency ω and could therefore be separated from the dominating unaffected part of the spectrum by phase-sensitive detection (PSD). It was found that at 5.0 mM bulk concentration of cholate 6.1 ± 1.0 cholate molecules were bonded by one immobilized HSA molecule. Furthermore, an increase of α-helical structures in HSA was initiated by cholate bonding.

Computational modeling and molecular imprinting for the development of acrylic polymers with high affinity for bile salts

This work has focused on the rational development of polymers capable of acting as traps of bile salts. Computational modeling was combined with molecular imprinting technology to obtain networks with high affinity for cholate salts in aqueous medium. The screening of a virtual library of 18 monomers, which are commonly used for imprinted networks, identified N-(3-aminopropyl)-methacrylate hydrochloride (APMA·HCl), N,N-diethylamino ethyl methacrylate (DEAEM) and ethyleneglycol methacrylate phosphate (EGMP) as suitable functional monomers with medium-to-high affinity for cholic acid. The polymers were prepared with a fix cholic acid:functional monomer mole ratio of 1:4, but with various cross-linking densities. Compared to polymers prepared without functional monomer, both imprinted and non-imprinted microparticles showed a high capability to remove sodium cholate from aqueous medium. High affinity APMA-based particles even resembled the performance of commercially available cholesterol-lowering granules. The imprinting effect was evident in most of the networks prepared, showing that computational modeling and molecular imprinting can act synergistically to improve the performance of certain polymers. Nevertheless, both the imprinted and non-imprinted networks prepared with the best monomer (APMA·HCl) identified by the modeling demonstrated such high affinity for the template that the imprinting effect was less important. The fitting of adsorption isotherms to the Freundlich model indicated that, in general, imprinting increases the population of high affinity binding sites, except when the affinity of the functional monomer for the target molecule is already very high. The cross-linking density was confirmed as a key parameter that determines the accessibility of the binding points to sodium cholate. Materials prepared with 9% mol APMA and 91% mol cross-linker showed enough affinity to achieve binding levels of up to 0.4 mmol g −1 (i.e., 170 mg g −1) under flow (1 mL min −1) of 0.2 mM sodium cholate solution.

Mono-dispersed single-walled carbon nanotubes made by using arc-burning method in nitrogen atmosphere

Single-walled carbon nanotubes made by using arc-burning technique in nitrogen atmosphere were dispersed in sodium cholate (SC) solution, and the diameter and chirality distribution of semiconductive SWNTs was investigated by UV-VIS-NIR and Raman spectroscopy, and photoluminescence mapping technique. In the typical formation condition, the diameter distribution of them is found to be relatively narrow (1.2 nm-1.4 nm in diameter), less chirality dependent, almost the same as the diameter distribution of SWNTs obtained by using laser-furnace technique.

Preparation of clear solutions of reconstituted acetylcholinesterase Effect of ionic strength and lipid/protein ratio

The detergent-soluble globular dimer of acetylcholinesterase from Torpedo californica was reconstituted through dialysis into preformed egg phosphatidylcholine vesicles. The formation of the enzyme-lipid complexes depended on the ionic strength of the dialysis buffer as well as the molar lipid/protein ratio (R). The enzyme was unstable at I less than 0.05; increasing the ionic strength increased the size of the complex. A too low R value (e.g. 1000) would promote self-aggregation of the enzyme and produce heterogeneous complexes, especially at high I values. On the other hand, a too high R value (e.g. greater than 5000) favored the formation of large enzyme-lipid complexes; their solutions were too turbid for optical studies. The enzyme reconstituted at I = 0.07 and R = 4000 gave a clear solution and showed no artifacts due to light scattering. The conformation based on circular dichroism and enzymatic activity of the detergent-soluble enzyme were unchanged upon reconstitution. The reconstituted enzyme in lipid vesicles seemed to be slightly more stable against thermal denaturation than the protein in sodium cholate solution.