Pyrazole‐substituted Near‐infrared Cyanine Dyes Exhibit pH‐dependent Fluorescence Lifetime Properties

Near‐infrared heptamethine cyanine dye is functionalized with pyrazole derivatives at the meso‐position to induce pH‐dependent photophysical properties. The presence of pyrazole unsubstituted at ¹N‐position is essential to induce pH‐dependent fluorescence intensity and lifetime changes in these dyes. Replacement of meso‐chloro group of cyanine dye IR820 with ¹N‐unsubstituted pyrazole resulted in the pH‐dependent fluorescence lifetime changes from 0.93 ns in neutral media to 1.27 ns in acidic media in DMSO. Time‐resolved emission spectra (TRES) revealed that at lower pH, the pyrazole consists of fluorophores with two distinct lifetimes, which cor‐responds to pH‐sensitive and non‐pH‐sensitive species. In contrast, ¹N‐substituted pyrazoles do not exhibit pH response, suggesting excited state electron transfer as the mechanism of pH‐dependent fluorescence lifetime sensitivity for this class of compounds.     

Matrix isolation FT-IR, FT-Raman spectroscopy, conformational ab initio calculations, and vibrational frequencies of meso and racemic-2,4-pentanediol

The infrared spectra of meso-2,4-pentanediol and racemic-2,4-pentanediol were measured in an argon matrix at 20 K. The Raman spectra of the pure liquids (meso and racemic) were measured at room temperature. The spectra were obtained using a Fourier transform spectrophotometer and a cryostat for the low temperature matrix. The meso and racemic forms of the diol were separated by means of a spinning band distillation column. The energies of nine possible conformers of the meso form and nine conformers of the racemic form were calculated. Extensive ab initio calculations using B3LYP, MP2 and HF methods with several basis sets consistently gave the lowest energy for the TT conformer of the meso form and the G⁻T (=TG⁻) conformer of the racemic form. Ab initio calculations at the B3LYP/6-31G** level were performed for the lowest energy conformer of meso and racemic pentanediol to obtain the equilibrium geometry, vibrational frequencies, and infrared and Raman intensities. Calculated and experimental frequencies were compared to make vibrational assignments.     

Carbon-13 nuclear magnetic resonance quantitative measurements of average sequence lengths of like stereochemical additions in polypropylene and polystyrene

Sequence lengths of stereochemical additions in vinyl polymers are described in terms of the number average lengths of like configurational placements. Under these circumstances, a pure syndiotactic polymer has a number average sequence length of 1.0; a polymer with 50:50 meso, racemic additions has a number average sequence length of 2.0 and polymers with more meso than racemic additions have number average sequence lengths greater than 2. Amorphous and crystalline polypropylenes and an amorphous polystyrene are examined using ¹³C NMR as examples of the applicability of the average sequence length method. The results appear to be accurate for amorphous and semicrystalline polymers but limitations are present when this method is applied to highly stereoregular vinyl polymers containing predominantly isotactic sequences.     

Stability of oil/water (ethanol,lysozyme or lysine) emulsions

Emulsions of n-tetradecane in water (0.1%^v/_^V) homogenized by ultrasounds (1 5 min) were stabilized by 0.5 or 1.0 M ethanol and in the presence of lysozyme (4 mg 100 ml⁻¹) or 1 mM lysine monohydrochloride (14.6 mg 100 ml⁻¹). The zeta potentials and multimodal size distributions of the droplets after 5, 15, 30, 60, 120 min, and 1 and 2 days were determined by dynamic light scattering technique using ZetaPlus apparatus (Brookhaven Instr., USA). Both parameters were determined on the same sample subsequently without any mixing. The effect of pH [4, 6.8 (natural), and 11] was also investigated. The most stable emulsions in 1 M ethanol solutions alone were at pH 6.8 and 11 (the effective diameter D_eff and 350 nm, respectively), while in 0.5 M at pH 4 (D_eff nm). The most stable emulsions with lysozyme were obtained at pH 4 and 1 M ethanol (D_eff nm), and with lysine at pH 6.8 and 0.5 M ethanol (D_eff nm). Except for the emulsions with lysozyme at pH 4 and 6.8, in the rest systems the zeta potentials were negative and ranged between −5 and −85 mV as a function of time and pH. The changes of zeta potential indicate that H⁺ ions are not much potential determining, while OH⁻ ions increase the negative zeta potentials. However, H⁺ ions affect functional groups of lysozyme molecules adsorbed on the alkane droplet, what appears in essential changes of zeta potential and even reversed sign of it in some systems. The results point that stability of these emulsions may also be determined by hydrogen bonding.     

The NMR spectra of porphyrins—19: 13C and proton NMR spectra of metal-free porphyrins with the Type-IX substituent orientation,and of their zinc(II) complexes

The ¹³C and proton NMR spectra of six porphyrins bearing the substituent orientation characteristic of the natural “Type-IX” arrangement are reported and assigned. Significant concentration effects in the spectra of the free base porphyrins, together with the broadening of the C_α (and occasionally C_β) carbon resonances due to NH tautomerism caused a significant loss of data in these spectra. However, the spectra of the corresponding zinc(II) porphyrins (with addition of excess pyrrolidine) show that both these extraneous effects are completely removed to give well-resolved spectra with accurately reproducible chemical shifts. These spectra are assigned and an analysis of the chemical shifts allows the deduction of substituent chemical shift (SCS) parameters for the peripheral substituents at the beta and meso carbons. There is no global effect of these beta substituents, the beta carbon SCS being confined to the immediate pyrrole ring, and the meso carbon SCS to the two adjacent pyrrole rings. The SCS parameters are analyzed and it is shown how they can be used to predict the peripheral and meso carbon chemical shifts of any porphyrin bearing the substituents discussed.     

Study of adduct ions of meso-phenyl-substituted tetrabenzoporphyrins by fast-atom bombardment mass spectrometry

Mass spectra of meso-phenyl-substituted tetrabenzoporphyrins were investigated by fast-atom bombardment mass spectrometry and tandem mass spectrometry. A cluster of adduct ions with mass-to-charge ratio values higher than the corresponding molecular ions of the porphyrins has been observed. The mass number differences among the series of cluster ions are constant depending on the para-phenyl substituents. Under certain conditions, dimers or trimers of molecular ions with low abundances have been detected. To trace the origin of the adduct ions, a series of experiments based on mass spectrometry have been carried out. The mass spectrum of tetrabenzoporphyrin showed no adduct ions with mass number differences of 90 even with the addition of phenylacetic acid. The mass spectrum of meso-tetraphenylte-trabenzoporphyrin ¹³C-labeled at the meso carbons showed adduct ions with mass number differences of 91. Product spectra of [2M + H]⁺ or [3M + H]⁺ of porphyrins exhibited adduct ions. All these results suggest that fragmentations of [2M + H]⁺ or [3M + H]⁺ may be one of the many possible routes to form the adduct ions, and the mass number differences among the series of these cluster ions should correspond to the benzyl group from the meso positions of meso-phenyl-substituted tetrabenzoporphyrins.     

Reaction mechanism of the benzoquinone/hydroquinone couple at platinum electrodes in aqueous solutions: Retardation and enhancement of electrode kinetics by single chemisorbed layers

The electrochemical kinetics of the benzoquinone (Q)/hydroquinone (H₂Q) redox couple at platinum electrodes in aqueous solutions has been found to be extremely sensitive to the nature of species adsorbed on the electrode surface at monolayer coverages. Experimental measurements were based on thin-layer cyclic voltammetry; the use of thin-layer electrodes was dictated by the need to minimize surface contamination. Bulky neutral or anionic aromatic adsorbates led to the familiar U-shaped rate-vs.-pH curves; the rate minimum occurred near pH 4. Kinetic effects due to oriental changes of chemisorbed species were noted only when the rate was low. Adsorbed 1 atoms led to comparatively rapid reactivity (rate constant k° > 10^?3 cm s^?1) and virtual independence of pH. Profound retardation resulted from pretreatment ofthe surface with CN^? and SCN^?; total irreversibility (k° < 10^?6 cm s^?1) was observed at pH 4, with a further decrease in rate at pH 7. In contrast, when the surface contained n layer of chemisorbed phenyltriethylammonium cations, the electrode rate increased with increasing pH. The results indicate that different reaction pathways predominate when different absorbates are present.     

Fluorescence studies on the interaction of hydrophobic ligands with Momordica charantia (bitter gourd) seed lectin

The interaction of Momordica charantia (bitter gourd) seed lectin (MCL) with several nucleic acid bases has been investigated by monitoring changes induced in the protein fluorescence by ligand binding. Values of the binding constant, K_a were obtained as 1.1 × 10⁴, 1.56 × 10⁴ and 2.2 × 10³ M^?1 for adenine, cytosine and uracil, respectively. In addition, binding of 8-anilinonaphthalene 1-sulfonate (ANS) with MCL was investigated by fluorescence spectroscopy. Interaction with MCL at low pH results in a large enhancement of the fluorescence intensity of ANS with a concomitant blue shift in the emission λ_max, whereas at neutral and basic pH changes in both fluorescence intensity and emission maximum were very small, clearly suggesting that the MCL–ANS interaction is stronger at lower pH values. When excited at 295 nm in the presence of ANS, the protein fluorescence decreased with a concomitant increase in the emission intensity of ANS, suggesting resonance energy transfer from the tryptophan residues of MCL to ANS. Gel filtration profiles of MCL at pH values 2.0 and 7.4 are similar indicating that the tetrameric nature of MCL is retained even at low pH. Addition of lactose or adenine to MCL–ANS mixture did not alter the change in ANS fluorescence suggesting that lactose, adenine and ANS bind to MCL at independent and non-interacting sites. These results are relevant to understanding the functional role of MCL in the parent tissue.     

The effect of environmental factors on the uptake of 60Co by Paecilomyces catenlannulatus

Paecilomyces catenlannulatus (P. catenlannulatus), a kind of important pathogenic fungi of forest pests, can be regarded as an excellent material to retard the fate and transport of radionuclides. The effect of environmental factors (i.e., pH, ionic strength, temperature and solution concentration) on the uptake of ⁶⁰Co by P. catenlannulatus was investigated by batch technique. The results showed that the uptake of ⁶⁰Co by P. catenlannulatus was independent of pH at pH < 5.0, whereas the enhanced uptake of ⁶⁰Co was observed with increasing pH from 5.0 to 8.0, then remained the high-level uptake at pH > 8.0 due to occurrence of precipitates. It is found that ⁶⁰Co uptake significantly decreased with increasing ionic strength at low pH, whereas little change was observed at high pH. The pH dependence adsorption indicates that the interaction mechanism between ⁶⁰Co and P. catenlannulatus is ion exchange at low pH and surface complexation at high pH conditions, respectively. Compared to Freundlich model, the adsorption isotherms can be fitted by Langmuir model very well. The thermodynamic data calculated from the temperature adsorption isotherms indicated that the uptake process of ⁶⁰Co by P. catenlannulatus was an endothermic and spontaneous process. This paper focused on potential application of P. catenlannulatus as suitable bio-materials for the preconcentration and removal of radionuclides from aqueous solutions in environmental pollution management.     

Spectroscopic studies of dipyridamole derivatives in homogeneous solutions: Effects of solution composition on the electronic absorption and emission

Electronic absorption and fluorescence spectra of three different dipyridamole (DIP) derivatives, RA 39, RA 14 and RA 25, were monitored in aqueous solution as a function of pH in the range 2–13. Extinction coefficients, quantum yields and fluorescence lifetimes were obtained in aqueous solutions at different pHs and in several other solvents. The absorption spectra are characterized by two broad bands centered at 405–415 nm and 290 nm for RA 39 and RA 14 and at 370 and 270 nm for RA 25. The first band used for fluorescence excitation has a value of ε ≌ 5 × 10³ M⁻¹ cm⁻¹ characteristic of a π → π* transition. An increase in pH is accompanied by both fluorescence and absorption sharp changes around pH 6 giving a pK ≌ 5.8 for RA 39 and RA 14, similar to the one observed for DIP. In the case of RA 25 two pKs are observed below 6.5, namely a pK₁ ≌ 2.25 and pK₂ = 5.20. These changes are associated to protonation equilibria of nitrogens in the π-conjugated system of the pyrimido—pyrimidine ring. At high pH a second transition is observed only in fluorescence with pK ≌ 12.5 for RA 39 which is similar to DIP and pK ≌ 12.1 for RA 25. For RA 14 this transition was not observed. Estimates of the pK* for the first singlet excited state showed that in comparison to the ground state pK ≌ 5.8 or 5.2 (RA 25), the excited state pK* is more acid by almost a unit. In the case of RA 25 and the lowest pK of 2.25, an excited state reaction, possibly of proton transfer, seems to take place since emission and absorption data give opposite effects for pK*.     

The effect of pH on some outer-sphere electrode reactions at carbon electrodes

The apparent heterogeneous rate constant, k°_app, for three couples known to undergo outer-sphere electron transfer reactions has been investigated at carbon, gold, and platinum electrodes as a function of solution pH. The rates are found to be pH dependent at two different types of glassy carbon and at carbon paste but not at metallic electrodes. The rate is found to decrease with increasing pH for Fe(CN)^{$\text{3?}\text{4?}$}₆ and IrCl^{$\text{2?}\text{3?}$}₆, and the opposite effect is observed for the Ru(NH₃)^{$\text{3+}\text{2+}$}₆ couple. For the three compounds examined, the magnitude of the pH dependent rate changes can be associated with a change in the magnitude of the potential of the reaction layer induced by a change in surface charge of ～ 2 × 10^?7 C cm^?2. The pH dependence of the observed rate constant at glassy carbon can be attenuated by heat treatment, chemical reduction, or esterification of the surface. This behaviour is consistent with the theory that the pH dependence of k°_app arises from the presence of functional groups on the carbon surface.     

Pulse radiolysis of 3-pyridine methanol and 3-pyridine carboxaldehyde in aqueous solutions

Reactions of e_aq ^-, H-atom and OH radicals with 3-pyridine methanol (3-PM) and 3-pyridine carboxaldehyde (3-PCA) have been studied at various pHs using pulse radiolysis technique. e_aq ^- was found to be highly reactive with both 3-PM and 3-PCA (k approx. 10¹⁰ dm³ mol 1 s^-1). Semi-reduced species formed in both cases were strongly reducing in nature. In the case of 3-PM, electron addition leads to the formation of pyridinyl radicals whereas in the case of 3-PCA, PyCHOH type radicals are formed. At pH 6.8, H-atom reaction with 3-PCA also gives semi-reduced species (PyCHOH), whereas at pH 1, H-atoms add to the ring. (CH₃)₂ ^·COH radicals were found to transfer electron to 3-PCA at all the pH values tested and by making use of changes in the absorption spectra, pK _a values of the semi-reduced species were determined to be 4.5 and 10.6. OH radicals were found to undergo addition reaction with 3-PCA, whereas in the case of 3-PM they reacted by H-abstraction as well as addition reaction. By following the yield of methylviologen radical cation formed by electron transfer reaction, it was estimated that approx. 50% of OH radicals react with 3-PM by H-atom abstraction at pH 6.8, giving reducing radicals, whereas at pH 3.2, where 3-PM is in the protonated form, the same is only about 10%. At pH 13, O^-· radical anions were found to react exclusively by H-atom abstraction. Reaction of SO₄ ^-· radicals with 3-PCA was found to give a species identical to the one formed by one electron reduction of nicotinic acid at acidic pH values.     

Development of a ratiometric time-resolved luminescence sensor for pH based on lanthanide complexes

Time-resolved luminescence bioassay technique using lanthanide complexes as luminescent probes/sensors has shown great utilities in clinical diagnostics and biotechnology discoveries. In this work, a novel terpyridine polyacid derivative that can form highly stable complexes with lanthanide ions in aqueous media, (4′-hydroxy-2,2′:6′,2′′-terpyridine-6,6′′-diyl) bis(methylenenitrilo) tetrakis(acetic acid) (HTTA), was designed and synthesized for developing time-resolved luminescence pH sensors based on its Eu³⁺ and Tb³⁺ complexes. The luminescence characterization results reveal that the luminescence intensity of HTTA–Eu³⁺ is strongly dependent on the pH values in weakly acidic to neutral media (pK_a = 5.8, pH 4.8–7.5), while that of HTTA–Tb³⁺ is pH-independent. This unique luminescence response allows the mixture of HTTA–Eu³⁺ and HTTA–Tb³⁺ (the HTTA–Eu³⁺/Tb³⁺ mixture) to be used as a ratiometric luminescence sensor for the time-resolved luminescence detection of pH with the intensity ratio of its Tb³⁺ emission at 540 nm to its Eu³⁺ emission at 610 nm, I_540 nm/I_610 nm, as a signal. Moreover, the UV absorption spectrum changes of the HTTA–Eu³⁺/Tb³⁺ mixture at different pHs (pH 4.0–7.0) also display a ratiometric response to the pH changes with the ratio of absorbance at 290 nm to that at 325 nm, A_290 nm/A_325 nm, as a signal. This feature enables the HTTA–Eu³⁺/Tb³⁺ mixture to have an additional function for the pH detection with the absorption spectrometry technique. For loading the complexes into the living cells, the acetoxymethyl ester of HTTA was synthesized and used for loading HTTA–Eu³⁺ and HTTA–Tb³⁺ into the cultured HeLa cells. The luminescence imaging results demonstrated the practical utility of the new sensor for the time-resolved luminescence cell imaging application.     

Use of Styrene as Sole Carbon Source by the Fungus Exophiala oligosperma: Optimization and Modeling of Biodegradation, Pathway Elucidation, and Cell Membrane Composition

Biodegradation of styrene by Exophiala sp. was tested at different initial concentrations (19.3?C170.6?mg?l^?1), pH (2.8?C8.7), and temperatures (19.8?C45.1?°C), for 120?h according to a 2³ full-factorial central composite design. The specific growth rate (SGR, per hour) and specific styrene utilization rate (SUR, milligrams of styrene per milligram of biomass per hour) values were used as the response variables for optimization purposes. The interactions between concentration and temperature (P?=?0.022), and pH and temperature (P?=?0.010) for SGR, and interactions between concentration and temperature (P?=?0.012) for SUR were found to be statistically significant. The optimal values for achieving high SGR (0.15?h^?1) and SUR (0.3622?mg styrene mg^?1 biomass h^?1) were calculated from the regression model equation. Those values are C _o ?=?89.1?mg?l^?1, pH?=?5.4, and T?=?31.5?°C for SGR and C _o ?=?69.2?mg?l^?1, pH?=?5.5, and T?=?32.4?°C for SUR. It was also observed that the Exophiala strain degrades styrene via phenylacetic acid, involving initial oxidation of the vinyl side chain. Besides, in the presence of styrene, changes in the fatty acids profile were also observed. It is hypothesized that an increasing amount of linoleic acid (18:2) may be involved in the protection of the fungus against toxic substrate.     

Thermo‐Viscoelastic Response of Polycarbonate Reinforced with Short Glass Fibers

Observations are reported for oscillatory torsion tests at several temperatures ranging from room temperature to 100 °C on a polymer composite consisting of a polycarbonate matrix reinforced with short glass fibers. Constitutive equations are derived for the linear viscoelastic behavior of the polymer composite, which is treated as an equivalent heterogeneous network of chains bridged by junctions (entanglements and glass fibers). The network is thought of as an ensemble of meso‐regions with arbitrary shapes and sizes. With reference to the concept of cooperative relaxation, the time‐dependent response of an ensemble is associated with the rearrangement of meso‐domains. The rearrangement events occur at random times as meso‐regions are agitated by thermal fluctuations. Stress–strain relations for isothermal deformation of an ensemble of meso‐domains are derived by using the laws of thermodynamics. The governing equations are determined by five adjustable parameters that are found by fitting the experimental data. The effects of temperature and filler content on the material parameters are studied in detail.

The shear modulus G GPa versus the content of short glass fibers ν wt.‐%. Symbols: treatment of observations in oscillatory torsion tests at T = 25 (unfilled circles) and T = 100 °C (filled circles). Solid lines: approximation of the experimental data by Equation (27). Curve 1: G₀ = 1.05, G₁ = 3.83 × 10⁻². Curve 2: G₀ = 0.91, G₁ = 3.65 × 10⁻².     

Thermodynamics of the complexing of uranyl ions with 1-phenyl-3-methyl-4-benzoylpyrazolone-5 in aqueous dioxane

The thermodynamics of the complexing between hexavalent U and 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (PMBP) have been studied in 70 vol% aqueous—dioxane medium at 25 and 35±0.1°C following the Bjerrum—Calvin pH titration technique, as applied by Van Uitert and Haas. The ligand is mono-protonic. The refinement of results of formation constants has been accomplished by the method of least squares treatment after an algebraic transformation. The formation of 1:1, 1:2 and 1:3 complexes has been observed, the order of stability being log K₁ > log K₂ > log K₃. The stability invariably increases with an increase in temperature both in aqueous as well as aqueous dioxane media. The changes in ΔG⁰, ΔH⁰ and ΔS⁰ at 25 and 35°C for the overall equilibrium constants have also been evaluated. Uranyl complexes of PMBP are entropy stabilized, the values of enthalpy changes being positive. Other factors which affect chelate stability are briefly discussed.     

Selective fluorometry of cytochrome c using glutathione-capped CdTe quantum dots in weakly basic medium

Glutathione-capped CdTe quantum dots (GSH-CdTe QDs) were synthesized in aqueous medium. Their interactions with proteins, especially three heme-containing proteins, were investigated over a broad pH range. At 6.0?<?pH?<?8.0, the fluorescence of the GSH-CdTe QDs can be effectively quenched by cytochrome c (Cyt. c) and hemoglobin, respectively. At pH?>?8.0, only cytochrome c quenched the fluorescence of the GSH-CdTe QDs, and no significant fluorescence changes were observed for hemoglobin or other proteins. Based on the distinct fluorescence response, a novel method has been developed for the selective determination of cytochrome c using GSH-CdTe QDs as the fluorescence probe at pH 9.0. Under optimum conditions, the linear range of the calibration curve is from 3.2?×?10^?8 to 2.4?×?10^?6?mol L^?1 and the detection limit is 3.0?×?10^?9?mol L^?1. The method has been applied to the determination of cytochrome c in three synthetic and real samples, and satisfactory results were obtained with QDs through selecting the proper pH value.     

Ratiometric Near-Infrared Fluorescent Probes Based on Hemicyanine Dyes Bearing Dithioacetal and Formal Residues for pH Detection in Mitochondria

Ratiometric near-infrared fluorescent probes (AH⁺ and BH⁺) have been prepared for pH determination in mitochondria by attaching dithioacetal and formal residues onto a hemicyanine dye. The reactive formyl group on probe BH⁺ allows for retention inside mitochondria as it can react with a protein primary amine residue to form an imine under slightly basic pH 8.0. Probes AH⁺ and BH⁺ display ratiometric fluorescent responses to pH changes through the protonation and deprotonaton of a hydroxy group in hemicyanine dyes with experimentally determined pKa values of 6.85 and 6.49, respectively. Calculated pK_a values from a variety of theoretical methods indicated that the SMD_BONDI method of accounting for solvent and van der Waals radii plus including a water molecule located near the site of protonation produced the closest overall agreement with the experimental values at 7.33 and 6.14 for AH⁺ and BH⁺ respectively.     

Voltammetric behavior of neptunium(vi) in glutamic acid media at the rotating glassy carbon electrode

The voltammetry of neptunium(VI) glutamate was investigated over the pH range 3.8–10.0. A reversible, one-electron wave was obtained for glutamate concentrations above 0.1 M in the pH range 3.8–6.1, or above 0.3 M in the pH range 6.1–10.0. At pH 3.8–6.1, the half-wave potential was independent of pH, but at pH 6.1–10.0, it was a function of pH. The metal-ligand ratio was found to be 1:2 by conductometric titration. The limiting current was proportional to the concentration of the neptunium(VI) from 7.83·10^-5 to 1.96·10^-3M. The diffusion coefficient was 0.35·10^-5 cm² sec^-1 at pH 4.5 and 0.30·10^-5 cm² sec^-1 at pH 9.4.     

Effect of external factors on the curcumin/2-hydroxypropyl-β-cyclodextrin: in vitro and in vivo study

The effect of 2-hydroxypropyl-β-cyclodextrin (HPβCD) on solubility, stability and oral bioavailability of curcumin by external factors adjustment, was investigated with an aim of a simple, stable and effective formulation. The phase solubility studies showed the solubility of curcumin increased slightly with increasing pH. However, the apparent stability constant (K _S) were found to decrease with increasing pH from 1.29?×?10⁴?M^?1 at pH 3.0 to 5.22?×?10³?M^?1 at pH 7.0. The thermodynamic parameters were calculated for inclusion complex formation in aqueous solution. Interestingly, it could be concluded that the degrees of curcumin stability improved by HPβCD grew with increasing drug–cyclodextrin binding ability. Furthermore, in vivo study not only revealed that the bioavailability of curcumin after oral administration to rats was significantly improved by curcumin/HPβCD inclusion complex, but also showed more dramatic changes in the plasma concentration–time curve (1752.76–866.70?ng?mL^?1?h) and the peak plasma concentration (370.10–178.11?ng?mL^?1) of drug by formation of complexes in pH 3–7 solution.