Cholesterol In Aqueous Solution Research Articles

Identification of cholesterol in different media by using the FT-IR, FT-Raman and UV–visible spectra combined with DFT calculations

In this investigation, the experimental FT-IR and FT-Raman spectra of cholesterol in the solid phase and in ethanol solution have been combined with the B3LYP/6–311++G** calculations and the scaled quantum mechanical force field (SQMFF) methodology, normal internal coordinates and transferable scaling factors to obtain the complete vibrational assignments of 216 vibration modes expected. Hence, complete vibrational assignments for that steroid of greatest biological importance are reported for first time in gas phase and ethanol solution together with its scaled force constants. Changes in the positions of some bands and in force constants values are observed in the different media due to the predicted intra-molecular interactions between CH3/CH3, CH3/CH2 and CH2/CH2 groups by atoms in molecules (AIM) calculations. The 1H- and 13C NMR chemical shifts of normal and deuterated cholesterol in aqueous solution confirm that the H atom of OH group is involved in the formation of H bonds in solution. Studies of experimental electronic spectra of cholesterol in different concentrations of ethanol revealed that the positions of peaks maxima increase conform increase the solution concentration. The natural bond orbital (NBO) analyses reveal that the polar OH group and the four fused rings play important roles in the stability and properties of cholesterol than the large hydrophobic moiety. Frontier orbitals predicted low reactivity of cholesterol in ethanol probably due to its high ω value in this medium.

Molecularly imprinted polymer coating-assisted CsPbBr3 perovskite quantum dots/TiO2 inverse opal heterojunctions for the photoelectrochemical detection of cholesterol.

Photoelectrochemical sensors have outstanding advantages including high sensitivity and miniaturization for outdoor use. Recently, perovskite quantum dots have attracted significant attention due to their high photoluminescence quantum yield. Nonetheless, there is still a strong need to improve their performance in challenging aqueous biological applications. In this paper, based on the molecularly imprinted polymer encapsulation of CsPbBr3 perovskite quantum dot/TiO2 inverse opal heterojunction structures, linear photoelectrochemical detection of cholesterol in aqueous solution was obtained without the involvement of an enzyme. The attenuation of photocurrent intensity under intermittent irradiation within 900 s (45 on/off cycles) was only 8.6%, demonstrating the superior stability of CsPbBr3 based sensor here. At the same time, the minimum detection limit of 1.22 × 10-9 mol L-1 in buffer conditions was lower than that reported for cholesterol photoelectric sensors. It has also been shown that the photoelectrochemical sensor of CsPbBr3 here outperformed that of CH3NH3PbBr3, which is another important member of the perovskite family. Finally, the proposed photoelectrochemical sensor platform was successfully applied in the determination of cholesterol in challenging serum with satisfactory recovery. The synergism among CsPbBr3 perovskite quantum dots, TiO2 inverse opal structure and imprinted polymer has led to greatly improved water stability, super selectivity and sensitivity, thus promoting the development of perovskite-based biological sensors.

Characterization and uncertainty evaluation of aqueous reference materials for cholesterol

Objective: Characterization and evaluation of the uncertainty of the reference materials of cholesterol in aqueous solution. Methods: The certified reference material GBW09203b was weighed accurately and dissolved into methyl cyclodextrin aqueous solution to prepare six kinds of candidate reference materials of cholesterol according to the concentration. The materials were tested for homogeneity and stability using routine methods and were evaluated the uncertainty derived from the inhomogeneity and instability. The uncertainty due to measurement was derived from the purity of the raw material, the weighing and the density measurement. The certified values and expanded uncertainties were calculated according to the ISO Guide. The expanded uncertainty of the certified value was the combination of standard uncertainty of measurement, inhomogeneity and instability. The coverage factor, k, was determined from the Student's t-distribution corresponding to the calculated effective degrees of freedom and 95% level of confidence. Results: It showed that the six candidate reference materials were homogeneous and were tested to be stable for at least 1 year at -70 ℃ and -20 ℃ using the isochronous stability study. The relative uncertainties due to the inhomogeneity were 0.14%, 0.11%, 0.13%, 0.47%, 0.39% and 0.11%. The relative uncertainty due to the instability was 0.25% at -70 ℃. The uncertainties of measurement were 0.06%, 0.05%, 0.05%, 0.05%, 0.05% and 0.05%.The certified values (reference value ± expanded uncertainty, mmol/L) were as follows: (0.651±0.004), (1.310 ±0.007), (2.574±0.015), (5.210±0.055), (7.710±0.072), (10.242±0.056) mmol/L. Conclusions: Six kinds of certified reference materials for cholesterol in aqueous solution have been prepared, which were homogeneity, stable and reliable. It showed that the uncertainty of measurement was very small compared with the uncertainty due to inhomogeneity and instability.

Colorimetric detection of cholesterol based on enzyme modified gold nanoparticles

We develop a simple colorimetric method for determination of free cholesterol in aqueous solution based on functionalized gold nanoparticles with cholesterol oxidase. Functionalized gold nanoparticles interact with free cholesterol to produce H2O2 in proportion to the level of cholesterol visually is being detected. The quenching in optical properties and agglomeration of functionalized gold nanoparticles play a key role in cholesterol sensing due to the electron accepting property of H2O2. While the lower ranges of cholesterol (lower detection limit i.e. 0.2mg/dL) can be effectively detected using fluorescence study, the absorption study attests evident visual color change which becomes effective for detection of higher ranges of cholesterol (lower detection limit i.e. 19mg/dL). The shades of red gradually change to blue/purple as the level of cholesterol detected (as evident at 100mg/dL) using unaided eye without the use of expensive instruments. The potential of the proposed method to be applied in the field is shown by the proposed cholesterol measuring color wheel.

Structure of small associates of glycyrrhizic acid with cholesterol in aqueous solution: Molecular dynamics simulation

In a recent work by Zelikman et al.(J. Struct. Chem., 2015, 56(1)), the molecular dynamics simulation of dimers of glycyrrhizic acid (GA) arising from the spontaneous collision of two GA molecules in water is performed. Several relatively stable dimer structures are found, and when a cholesterol molecule is inserted, associates are observed constituting a GA dimer with a cholesterol molecule “stuck” to it. Here, we simulate the associates consisting of three and four GA molecules and a cholesterol molecule. It appears that the cholesterol molecule, as a rule, also locates at the surface of the GA associate. Therewith, the trimers do not form any clear characteristic structures, as dimers do, and the tetramers can be two stuck dimers.

Solubilization of Hydroxypropyl-β-Cyclodextrin on Cholesterol in Aqueous Solution

Hydroxypropyl-β-Cyclodextrin (HP-β-CD), prepared via reaction of β-Cyclodextrin (β-CD) and propylene oxide (PO), is utilized to research solubilization of HP-β-CD on cholesterol in aqueous solution. HP-β-CD is characterized by Fourier Transform Infrared Spectrometry (FT-IR), and concentrations of cholesterol solution are measured by ultraviolet and visible (UV VIS) spectrophotometer. The research on optimal synthesis conditions of HP-β-CD indicates that sodium hydroxide amounts have the most effect on yields of product. The maximum solubilization multiples of HP-β-CD reaches 15, below which molecular rate of HP-β-CD and cholesterol in inclusion complex is 1:1.

Solubilization of cholesterol in aqueous solution by two β-cyclodextrin dimers and a negatively charged β-cyclodextrin derivative

Two βCD dimers (linked by succinic acid, 2, or ethylenediaminetetraacetic acid, EDTA, 3, bridges) and a negatively charged monomer derivative of βCD, 1, have been synthesized and their ability to solubilize cholesterol in aqueous solution was studied. The three compounds exhibit a great capacity in solubilizing cholesterol as, for instance, concentrations up to 6 mM of cholesterol were measured in the presence of 25 mM of 3. The phase-solubility diagrams of the two dimers exhibit A L type profiles while the monomer 1 follows an A P isotherm. The cholesterol/dimer complexes have 1:1 stoicheiometries while monomer 1 forms two complexes with molar ratios of 1:1 and 1:2 (cholesterol/1). The equilibrium constants are K 1:1 = (5.9 ± 0.3) × 104 M−1 and K 1:1 = (8.8 ± 0.2) × 104 M−1 for 2 and 3, respectively, and K 1:1 = 73 ± 19 M−1 and K 1:2 = 204 ± 65 M−1 for 1. The comparison of K 1:1(3) with the product K 1:1 × K 1:2 (1) reveals that a chelate effect in binding the cholesterol by 3 exists. The structure of the cholesterol/3 complex was studied by ROESY experiments and by molecular dynamics simulations.

Immobilization of cholesterol oxidase in LbL films and detection of cholesterol using ac measurements

The preserved activity of immobilized biomolecules in layer-by-layer (LbL) films can be exploited in various applications, including biosensing. In this study, cholesterol oxidase (COX) layers were alternated with layers of poly(allylamine hydrochloride) (PAH) in LbL films whose morphology was investigated with atomic force microscopy (AFM). The adsorption kinetics of COX layers comprised two regimes, a fast, first-order kinetics process followed by a slow process fitted with a Johnson–Mehl–Avrami (JMA) function, with exponent ~ 2 characteristic of aggregates growing as disks. The concept based on the use of sensor arrays to increase sensitivity, widely employed in electronic tongues, was extended to biosensing with impedance spectroscopy measurements. Using three sensing units, made of LbL films of PAH/COX and PAH/PVS (polyvinyl sulfonic acid) and a bare gold interdigitated electrode, we were able to detect cholesterol in aqueous solutions down to the 10 − 6 M level. This high sensitivity is attributed to the molecular-recognition interaction between COX and cholesterol, and opens the way for clinical tests to be made with low cost, fast experimental procedures.

Effect of hydration on the structure of solid-supported Niosomal membranes investigated by in situ energy dispersive X-ray diffraction

The supramolecular structure of Niosomal vesicles (Niosomes) made of a binary mixture of polysorbate 20 (Tween 20) and Cholesterol in aqueous solution was investigated by means of synchrotron small angle X-ray scattering (SAXS). Solid-supported Niosomal membranes at full hydration exhibit the same structural properties, as determined by in situ energy dispersive X-ray diffraction (EDXD), than their counterpart in solution. Both Niosomes and solid-supported Niosomal membranes are made of highly swollen bilayers rich in Tween 20 coexisting with Cholesterol crystallites. EDXD patterns from oriented samples suggest that at least some Cholesterol crystals are aligned along the normal to the solid support.

Bile salts and gallstone disease.

Bile salts play an important role in maintaining cholesterol in aqueous solution in bile. There is evidence that in some patients at least gallstones arise as a result of bile salt deficiency. The evidence to date suggests that although oral bile salts may be of use in treating some gallstone patients they are unlikely to replace cholecystectomy in the foreseeable future. The instillation of bile salts via an indwelling T-tube may well be of great use in the management of stones retained in the common duct after choledocholithotomy. There is no doubt that in this branch of medicine as in all others prevention is better than cure and our aim should be to perfect our technique so that we do not leave stones behind. However, should the situation occur we may soon have safe effective physiological solvents to dissolve our mistakes.

Interaction of Heptakis (2,3,6-Tri-<i>O</i>-methyl)-β-cyclodextrin with Cholesterol in Aqueous Solution

The interaction of cholesterol with heptakis (2,3,6-tri-O-methyl)-beta-cyclodextrin (TOM-beta-CyD) was investigated in water using solubility method. It was found that TOM-beta-CyD forms two kinds of soluble complexes, with molar ratios of 1:1 and 1:2 (cholesterol:TOM-beta-CyD). The thermodynamic parameters for 1:1 and 1:2 complex formation of cholesterol with TOM-beta-CyD were: DeltaG0(1:1)=-11.0 kJ/mol at 25 degrees C (K1:1=7.70 x 10 M(-1)); DeltaH0(1:1)=-1.28 kJ/mol; TDeltaS0(1:1)=9.48 kJ/mol; DeltaG0(1:2)=-27.8 kJ/mol at 25 degrees C (K1:2)=7.55 x 10(4) M(-1)); DeltaH0(1:2)=-0.57 kJ/mol; TDeltaS0(1:1)=27.3 kJ/mol. The formation of the 1:2 complex occurred much more easily than that of the 1:1 complex. The driving force for 1:1 and 1:2 complex formation was suggested to be exclusively hydrophobic interaction. Based on the measurements of proton nuclear magnetic resonance spectra and studies with Corey-Pauling-Koltun atomic models, the probable structures of the 1:2 complex were estimated. In addition, the interaction of TOM-beta-CyD with cholesterol was compared with that of heptakis (2,6-di-O-methyl)-beta-CyD (DOM-beta-CyD). The interaction of TOM-beta-CyD is more hydrophobic than that of DOM-beta-CyD, and the life time of the complexed TOM-beta-CyD is sufficiently long to give separated signals, at the NMR time scale, which differs from that of complexed DOM-beta-CyD.

ChemInform Abstract: Macrotricyclic Steroid Receptors by Pd0‐Catalyzed Cross‐Coupling Reactions: Dissolution of Cholesterol in Aqueous Solution and Investigations of the Principles Governing Selective Molecular Recognition of Steroidal Substrates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Study of the required HLB for the solubilization of cholesterol in aqueous solution

The solubilization of cholesterol by anionic surfactant mixtures was studied as a function of their HLB values. The relationship between the logarithm of the critical micelle concentration and the HLB value of the mixtures was not linear, which was attributed to a lack of strict additivity of the HLB values. The solubilized cholesterol/surfactant ratio was determined and it was found to be higher than that in bile salts in all the studied surfactant mixtures.

Macrotricyclic Steroid Receptors by Pd°‐Catalyzed Cross‐Coupling Reactions: Dissolution of cholesterol in aqueous solution and investigations of the principles governing selective molecular recognition of steroidal substrates

AbstractThree double‐decker cyclophane receptors, (±)‐2, (±)‐3, and (±)‐4 with 11–13‐Å deep hydrophobic cavities were prepared and their steroid‐binding properties investigated in aqueous and methanolic solutions. Pd°‐Catalyzed cross‐coupling reactions were key steps in the construction of these novel macrotricyclic structures. In the synthesis of D2‐symmetrical (±)‐2, the double‐decker precursor (±)‐7 was obtained in 14% yield by fourfold Stille coupling of equimolar amounts of bis(tributylstannyl)acetylene with dibromocyclophane 5 (Scheme 1). For the preparation of the macrotricyclic precursor (±)‐15 of D2‐symmetrical (±)‐3, diiodocylophane 12 was dialkynylated with Me3SiCCH to give 13 using the Sonogashira cross‐coupling reaction; subsequent alkyne deprotection yielded the diethynylated cyclophane 14, which was transformed in 42% yield into (±)‐15 by Glaser‐Hay macrocyclization (Scheme 2). The synthesis of the C2‐symmetrical conical receptor (±)‐4 was achieved via the macrotricyclic precursor (±)‐25, which was prepared in 20% yield by the Hiyama cross‐coupling reaction between the diiodo[6.1.6.1]paracyclophane 19 and the larger, dialkynylated cyclophane 17 (Scheme 4). Solid cholesterol was efficiently dissolved in water through complexation by (±)‐2 and (±)‐3, and the association constants of the formed 1:1 inclusion complexes were determined by solid‐liquid extraction as Ka = 1.1 × 106 and 1.5 × 105 l mol−1, respectively (295 K) (Table 1). The steroid‐binding properties of the three receptors were analyzed in detail by 1H‐NMR binding titrations in CD3OD. Observed steroid‐binding selectivities between the two structurally closely related cylindrical receptors (±)‐2 and (±)‐3 (Table 2) were explained by differences in cavity width and depth, which were revealed by computer modeling (Fig. 4). Receptor (±)‐2, with two ethynediyl tethers linking the two cyclophanes, possesses a shallower cavity and, therefore, is specific for flatter steroids with a C(5)C(6) bond, such as cholesterol. In contrast, receptor (±)‐3, constructed with longer buta‐1,3‐diynediyl linkers, has a deeper and wider hydrophobic cavity and prefers fully saturated steroids with an aliphatic side chain, such as 5α‐cholestane (Fig. 7). In the 1:1 inclusion complexes formed by the conical receptor (±)‐4 (Table 3), testosterone or progesterone penetrate the binding site from the wider cavity side, and their flat A ring becomes incorporated into the narrower [6.1.6.1]paracyclophane moiety. In contrast, cholesterol penetrates (±)‐4 with its hydrophobic side chain from the wider rim of the binding side. This way, the side chain is included into the narrower cavity section shaped by the smaller [6.1.6.1]paracyclophane, While the A ring protrudes with the OH group at C(3) into the solvent on the wider cavity side (Fig. 8). The molecular‐recognition studies with the synthetic receptors (±)‐2, (±)‐3, and (±)‐4 complement the X‐ray investigations on biological steroid complexes in enhancing the understanding of the principles governing selective molecular recognition of steroids.

Solubilization and precipitation of cholesterol in aqueous solution of bile salts and their mixtures

Solubilization of cholesterol by mixed micelles of sodium chenodeoxycholate with sodium ursodeoxycholate was investigated in carbonate-tetraborate buffer (Kolthoff) solution at pH 10 and 37°C. It was found that the mixing of the two bile salts gives a negatively synergetic effect on solubilization of cholesterol. The solubilizing power of bile salts for cholesterol was remarkably influenced with the change in mole fraction of sodium ursodeoxycholate (XUDC).

Cavity depth and width effects on cyclophane-steroid recognition: molecular complexation of cholesterol and progesterone in aqueous solution

Recent X-ray crystal structures show that steroid-binding proteins contain deep hydrophobic cavities defined by aromatic amino-acid side chains which encapsulate steroid molecules. These cavities resemble the binding site of a synthetic macrotricyclic cyclophane receptor which we recently reported to form complexes with cholesterol in aqueous solution. The binding affinity of the cyclophane-cholesterol complex (Ka approximately 10(6) M-1, 295 K) is similar to that measured for the cholesterol complex of steroid-transport proteins such as sterol carrier protein-2 (SCP-2). Here we describe synthesis and binding studies of a related receptor with a cavity that is wider and 2 A deeper than that of the previous cyclophane, and a comparison of the steroid-binding affinity and selectivity of the two synthetic receptors. A new tricyclic cyclophane receptor with a 13 A deep cavity was synthesized to study the effect of increased cavity depth on receptor selectivity for steroids. NMR analysis demonstrated that this receptor provided increased steroidal side-chain encapsulation with a corresponding gain in binding free energy of 0.9 kcal mol-1 (in d4-methanol) as compared to our previously reported 11 A deep receptor. An unexpected consequence of the increase in cavity depth was a corresponding enlargement of the cavity width, as indicated both by steroid-binding studies and molecular modeling. This enlargement in cavity width increases binding affinity for saturated steroids while decreasing the association strength of unsaturated steroids such as cholesterol. In water, cholesterol binds to the new receptor with Ka approximately 1.5 x 10(5) M-1 and exhibits a significant complexation-mediated solubility increase. Small changes in steroid receptor dimensions have resulted in large differences in steroid selectivity and binding affinity. These results indicate that potentially large gains in steroid-binding free energy may be obtainable from complete hydrophobic encapsulation of the flexible aliphatic steroidal side chain. These results have implications for the design of synthetic receptor mimics of natural steroid binding proteins.

Rod-like cholesterol micelles in aqueous solution studied using polarized and depolarized dynamic light scattering

Micelles of cholesterol in aqueous solution have been investigated using polarized and depolarized dynamic light scattering. They are shown to be highly extended and characterized by a narrow size distribution. It is shown that a rod-like model is applicable with length, L = 580 nm. Determination of the rotational diffusion coefficient by analysis of the autocorrelation function gave a value of theta = 150 s-1, which is close to the calculated value for the rod with this dimension. Depolarized dynamic light scattering measurements as a function of angle gave a value of 110 s-1.

Interaction of bile salt monomer and cholesterol in the aqueous phase

The purpose of the present study was to evaluate the possible interaction of bile salt monomer and cholesterol in the intermicellar aqueous phase. Cholesterol and taurocholate monomer concentrations in the intermicellar aqueous phase were determined using 0–20 mM taurocholate solutions saturated with cholesterol. Maximal solubilities of cholesterol in aqueous solutions having various concentrations of taurocholate, especially below its intermicellar monomer concentration (critical micellar concentration), were determined and compared with the intermicellar cholesterol concentration. The intermicellar monomer concentration of taurocholate was constant (6 mM) and independent of taurocholate concentrations. The cholesterol concentration in the intermicellar aqueous phase gradually increased, depending upon taurocholate concentrations, and became constant (1,3 μM) above 10 mM taurocholate. The solubility of cholesterol increased linearly with the taurocholate concentration even below the critical micellar concentration, and was 0.3 μM at 6 mM taurocholate, which was approx. 20-times higher than the aqueous solubility of cholesterol, but a fifth of the maximal intermicellar cholesterol concentration. The results indicate that the higher cholesterol concentration in the intermicellar aqueous phase compared to its aqueous solubility can be primarily ascribed to the interaction of cholesterol with bile salt monomers possibly forming bile salt-cholesterol dimers, and partly to the sustaining forces induced by numerous micelles.

Interaction of lucensomycin with membranes: the role of non-steroidal components

The binding of lucensomycin to unilamellar phospholipid / cholesterol vesicles and to colloidal emulsions of cholesterol in aqueous solutions was studied by monitoring the changes in the electronic absorption spectra of the polyene antibiotic. The total extent of the absorption variations was a direct function of cholesterol concentration and quite independent of the nature of the emulsion. The rate of binding, relatively slow in the colloidal systems, was greatly enhanced when cholesterol was included in phospholipid-containing membranes. The rate of lucensomycin binding to colloidal cholesterol increased with increasing cholesterol concentrations and / or stirring the heterogeneous suspension. The time course of lucensomycin binding to vesicles appeared to be independent of the concentrations of phospholipids and cholesterol.

ChemInform Abstract: EFFECTS OF PH, PNA, AND TEMPERATURE ON MICELLE FORMATION AND SOLUBILIZATION OF CHOLESTEROL IN AQUEOUS SOLUTIONS OF BILE SALTS

Chemischer InformationsdienstVolume 13, Issue 41 Article ChemInform Abstract: EFFECTS OF PH, PNA, AND TEMPERATURE ON MICELLE FORMATION AND SOLUBILIZATION OF CHOLESTEROL IN AQUEOUS SOLUTIONS OF BILE SALTS G. SUGIHARA, G. SUGIHARASearch for more papers by this authorK. YAMAKAWA, K. YAMAKAWASearch for more papers by this authorY. MURATA, Y. MURATASearch for more papers by this authorM. TANAKA, M. TANAKASearch for more papers by this author G. SUGIHARA, G. SUGIHARASearch for more papers by this authorK. YAMAKAWA, K. YAMAKAWASearch for more papers by this authorY. MURATA, Y. MURATASearch for more papers by this authorM. TANAKA, M. TANAKASearch for more papers by this author First published: October 12, 1982 https://doi.org/10.1002/chin.198241077AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume13, Issue41October 12, 1982 RelatedInformation