A Spectrofluorimetric Sequential Injection Method for the Determination of Penicillamine Using Fluorescamine in the Presence of β-cyclodextrins

A simple, robust and sensitive sequential injection spectrofluorimetric method for the determination of penicillamine (PA) in pharmaceutical formulations is developed. The method is based on the formation of a highly fluorescent derivative when penicillamine is reacted with fluorescamine (FL) in borate buffer of pH 9.3. The derivative produced is monitored at an emission wavelength of 495 nm using an excitation wavelength of 355 nm. The optimum conditions for the determination of PA with FL were: 3 mM FL, pH 9.3, 5 mM methyl-β-cyclodextrin, sample volume of 75 μL and reagent volume of 75 μL. Furthermore, the effect of various media on the fluorescence intensity of the PA–FL derivative was studied and methyl-β-cyclodextrin was found to give the largest enhancement. A linear dynamic range for the determination of PA of 5–80 ppm was obtained with a sampling frequency of 50 h⁻¹ and a relative standard deviation of less than 2.5%. The method was applied to the determination of PA in pharmaceutical formulations with reasonable recoveries ranging from 101.0–103.1%, indicating that no interference is observed from concomitants usually present in dosage forms.     

C-13 NMR Investigation of Cellobiose in the Presence and Absence of β-Glucosidase

T1(C-13) NMR measurements of cellobiose in aqueous solutions at pH=5 in the presence and absence of enzyme β-glucosidase detected at T=276°K a fast interaction between cellobiose and the enzyme at C1′α level of the disaccharide molecule. T1(C-13) measurements of equal solutions of cellobiose in the presence and absence of EDTA at the same temperatures suggest also a competitive interaction of cellobiose, at C1′α level, with EDTA complexed with a metal ion. T1 data justify a nearly spherical shape of cellobiose in solution.     

Transport properties of aqueous solutions of calcium lactate in the absence and presence of β-cyclodextrin

Mutual diffusion coefficients and electrical conductivity of a well-known food additive and supplement, or excipient in pharmaceutical formulations, calcium lactate, have been measured in the absence and presence of β-cyclodextrin in aqueous solutions, at 298.15 K. The dependence of conductivity on concentration has been analysed using the Fuoss-Edelson method. The values of the Nernst diffusion coefficients, for binary solutions, derived from conductance and from diffusion experiments are in good agreement. The presence of β-cyclodextrin leads to a non-expected effect on the transport properties of the aqueous solutions of calcium lactate. These data have been justified with help of ¹H NMR spectroscopy. The effect on the water structure, reducing the hydration shell of lactate, is argued. This leads to an increase of the effective concentration of calcium lactate in solution contributing to an increase in the diffusion coefficients and a decrease in the dependence of the electrical conductance on the concentration.     

Morphological Distribution in Micro-Injected Polypropylene Parts in the Presence of β-Nucleating Agent

Micro-injection molding is attracting much attention nowadays. Characterization of the morphological distribution in parts prepared by micro-injection molding is thus of growing importance. The morphological features of micro-parts may strongly differ from those of the macro-parts prepared by conventional injection molding, resulting in specific physical properties. In the present study, β-nucleated isotactic polypropylene micro-parts (μPPB) with 200 μm thickness, as well as macro-parts (PPB) with 2000 μm thickness, were prepared. Polarized light microscopy (PLM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction (WAXD) were used to investigate their morphological features. The results show that the morphology distribution in μPPB had many differences from that of the PPB. The one-dimensional WAXD and DSC analysis showed similar results; the degree of crystallinity of the μPPB was higher than that of the PPB. However, the content of β-crystals of μPPB was lower than that of the PPB. This can be explained by the restraining effect for the formation of β-crystals in β-nucleated isotactic polypropylene (iPP) under the strong shear field. The through-the thickness-morphology of both μPPB and PPB exhibited a “skin-core” structure from PLM observations, but the former had a large fraction of shear layer in comparison to the latter implied. The SEM observations showed that the shear layer of μPPB consisted of a highly oriented shish-kebab structure, while that of the core layer consisted of deformed spherulites structure. The two-dimensional WAXD pattern of the core layer of PPB, showing full Debye rings, indicated an overall random orientation of the iPP chains, while the arcing indicated a pronounced orientation in the shear layer. The more pronounced arcing of the μPPB indicated a more pronounced orientation.     

Stoichiometrically Different Inclusion Complexes of 2-Aminofluorene and 2-Amino-9-Hydroxyfluorene in β-Cyclodextrin: A Spectrofluorimetric Study

β-cyclodextrin (β-CDx) forms inclusion complexes with 2-aminofluorene (2AF) and 2-amino-9-hydroxyfluorene (2AHF) in different stoichiometries (Guest-host ratio 1:1 and 1:2 respectively) which is discussed on the basis of study by absorption and fluorescence spectroscopy. The ground and the excited state acidity constants for the neutral‒monocation equilibrium of the two fluorophores in aqueous β-CDx medium are determined by spectrophotometric and fluorimetric titration methods respectively. The dual fluorescence observed for 2AHF monocation in aqueous solution is due to the formation of monocation-water exciplex. This monocation-water exciplex formation is hindered in β-CDx solution by the inclusion complexation. Based on the results obtained, the structures of the inclusion complexes are proposed.     

Diffusion coefficients of sodium dodecylsulfate in aqueous solutions and in aqueous solutions of β-cyclodextrin

Differential diffusion coefficients have been measured of sodium dodecylsulfate (SDS) in aqueous solutions of β-cyclodextrin (β-CD) at 298.15 K over the concentration range 0.001 M to 0.0817 M using a conductimetric cell and an automatic apparatus to follow the diffusion. The cell uses an open ended capillary method, while a conductimetric technique is used to follow the diffusion process by measuring the resistance of a solution inside the capillaries, at various recorded times. The β-CD is known to for strong 1:1 complexes with SDS, and the effect of this on the diffusion of this electrolyte was investigated. The presence of β-cyclodextrin can influence the diffusion coefficients of sodium dodecylsulfate both above and below the critical micelle concentration (cmc) of this surfactant. For concentrations of β-cyclodextrin of 0.001 mol dm⁻³ the behaviour of the diffusion of SDS in aqueous solutions is the same in the absence or the presence of β-cyclodextrin. In contrast, when the β-CD concentration is 0.016 mol dm⁻³ we obtain diffusion coefficients higher than those obtained in aqueous solutions. Further, we do not observe the dramatic decrease in diffusion normally found at the cmc of the surfactant. These results are interpreted in terms of the effect of incorporation of dodecylsulfate chains inside the cyclodextrin cavities.     

Monte Carlo Study of the Neutron Detection Wall at RIBLLⅡ in HIRFL-CSR

With the construction of the new Radioactive Ion Beam Line in Lanzhou (RIBLLⅡ) which connects the CSRm and the CSRe, an experimental setup for physics research is highly required. A large area neutron detection wall is the main part of the setup. This paper introduced the detection principle of the neutron detection wall and the Monte-Carlo simulation of its design under the environment of the Geant4 toolkit. We presented the final design with the optimized parameters and the performance of the wall.     

Ambiguities of the Seiberg-Witten Map in the Presence of Matter Field

The ambiguities of the Seiberg-Witten map for gauge field coupled with fermionic matter are discussed.We find that only part of the ambiguities can be absorbed by gauge transformation and/or field redefinition and thus are negligible.The existence of matter field makes some other part of the ambiguities difficult to be absorbed by gauge transformation of field regefinition.     

Time-Resolved and Pulse EPR Study of Triplet States of Alkylketones in β-Cyclodextrin

The triplet states of deoxybenzoin (DOB) and benzophenone (BP) molecules in randomly methylated β-cyclodextrin (CD) cavity are studied by time-resolved (TR) and pulse electron paramagnetic resonance (EPR). The observed TR EPR spectrum of DOB in β-CD at 30 K is close to the spectrum measured in polar solvent trifluoroethanol, revealing strong hydration by water molecules. At the same time, TR EPR spectrum of BP in β-CD corresponds to nonpolar surrounding of the CO-group. The electron spin relaxation times T ₁ and T ₂ of triplet BP at 30 K measured by pulse EPR are found to be different in β-CD compared to nonpolar toluene glass. The observed increase of T ₂ by up to a factor of four in β-CD is caused by the lower vibration amplitude of CO-bond of BP due to the confinement in β-CD. The influence of β-CD with covalently attached nitroxide on the triplet states of DOB and BP is principally different: the excited triplet states could not be observed by TR EPR due to the efficient quenching of the excited states by nitroxide.     

EPR Detection of Possible Superparamagnetic Polyiron Nanoparticles and Free Radicals in the Blood Serum of Patients with Homozygous β-Thalassemia

In homozygous β-thalassemia blood transfusions and chelating therapy cannot prevent completely hemochromatosis. Labile ‘free’ iron forms in blood serum and evolves into insoluble inorganic deposits in tissues. Using X-band EPR at 163 K, we detected a new species of polynuclear iron in serum of some thalassemic patients. It showed a broad g < 2 line and an unusually high dynamic magnetic susceptibility due to ordered magnetism, which was detected by a decreased Q factor of the resonant cavity at B = 0. To explain the ordered magnetism and large line, we postulated either ferri- or ferromagnetic nanocrystals with non-zero residual magnetization, or superparamagnetic nanoparticles with antiferromagnetic ordering and incomplete spin compensation—or maybe both. While the results were not sufficient to check the first hypothesis, they are fully consistent with the second. The new species is similar to, but distinct from, ferritin’s mineral core, as it does not correlate with the ferritin concentration. The spectra suggest particles of ~1.7–4.1 nm diameter, plausibly containing ~40–300 Fe(III) ions coupled by oxygen bridges, but further confirmation is needed. The nanoparticles apparently formed a hydrophilic colloidal dispersion, being probably decorated with hydrophilic small organic molecules. They are postulated to form by heterogeneous nucleation around the ‘free’ iron, then aggregate in chains and eventually precipitate in the tissues. Stable free radicals detected in serum were tentatively identified as the hydroxyperoxyl and monodehydroascorbate radicals forming adducts with Cu(II)-ceruloplasmin, and the Hb–porphyrin–Fe(IV)=O oxoferryl radical probably stabilized on haptoglobin. They are consistent with oxy-radicals promoted both by ‘free’ iron and by polyiron nanoparticles. Potential medical applications like early assessment of patient’s evolution trend toward hemochromatosis and monitoring of the transfusional suppression of endogenous erythrocyte synthesis are suggested.     

Fluorimetric Study on Molecular Recognition of β-cyclodextrin with 2-amino-9-fluorenone

The molecular recognition interaction of β-cyclodextrin (β-CDx) was investigated using 2-amino-9-fluorenone (2AFN) by UV, steady-state fluorescence and time-resolved fluorescence measurements in aqueous solution at various pH. The effect of acidity on the ground and excited state equilibria between the neutral and the monocationic forms of 2AFN in water and in β-CDx environments are studied. Based on the change in the fluorescence spectrum and lifetimes of 2AFN by the addition of β-CDx, it is found that the unsubstituted part of the 2AFN is encapsulated in the hydrophobic cavity of β-CDx. The unusual red shift obtained for the protonation of amino group in water and β-CDx solution is due to large solvent relaxation of the monocation. The structure of the 1:1 inclusion complex between 2AFN and β-CDx has been proposed on the basis of ground and excited state pK _a values and the bond distances obtained by MOPAC/AM 1 data.     

Studies on the Interaction of Tricyclazole with β-cyclodextrin and human Serum Albumin by Spectroscopy

The interaction of tricyclazole (TCZ) with β-cyclodextrin (β-CD) and human serum albumin (HSA) were studied by fluorescence spectrum, UV-visible spectrum and second-order scattering technology. It was shown that TCZ has quite a strong ability to quench the fluorescence launching from HSA by reacting with it and forming a certain kind of new compound. The quenching and the energy transfer mechanisms were discussed, respectively. The binding constants and thermodynamic parameters at four different temperatures, the binding locality, and the binding power were obtained. The conformation of HSA was discussed by synchronous and three-dimensional fluorescence techniques. The inclusion reaction between β-CD and TCZ was explored by scattering method, the inclusion constants and the thermodynamic parameters at 297 K and 311 K were figured out, respectively. The mechanism of inclusion reaction was speculated and linkage among the toxicity of TCZ, the exterior environment and its concentration was attempted to explain on molecule level.     

Molecular encapsulation of amodiaquine in 2-hydroxypropyl β-cyclodextrin cavity. Characterization and its in vitro cytotoxicity

Amodiaquine has been used widely as an antimalarial drug. Amodiaquine is a mannich base 4-amino quinolone with a mode of action similar to that of chloroquine. The inclusion complex of amodiaquine with 2-(hydroxypropyl)-beta-cyclodextrin in solution phase is studied from the ground and excited state with absorption and fluorescence spectroscopic techniques, respectively. A binding constant and stoichiometric ratio between amodiaquine and 2-(hydroxypropyl)-beta-cyclodextrin are calculated by the use of Benesi–Hildebrand equation. The solid complexes are prepared by physical, kneading and coprecipitation methods. The solid complexes are characterized by Fourier-transform infrared spectral analysis, Differential scanning calorimetric curves and powder X-ray diffraction patterns. The anticancer activity was tested for pure amodiaquine and their complex with 2-(hydroxypropyl)-beta-cyclodextrin against MDA MB 231 cell line. It clearly showed that a significant improvement of anticancer activity of amodiaquine when forming a complex with 2-(hydroxypropyl)-beta-cyclodextrin.     

Detection of a Physical Difference between the CDM Halos in Simulation and in Nature

Numerical simulation is an important tool that is helpful for us to understand the process of structure formation in the universe. However, many simulation results of cold dark matter （CDM） halos on a small scale are inconsistent with observations： the central density profile is too cuspy and there are too many substructures, Here we point out that both the problems may be connected with a hitherto unrecognized bias in the simulated halos. Although CDM halos in nature and in simulation are both virialized systems of collisionless CDM particles, gravitational encounter cannot be neglected in the simulated halos because they contain many fewer particles. We demonstrate this by two numerical experiments, showing that there is a difference on the microcosmic scale between the natural and simulated halos. The simulated halo is more akin to globular clusters where gravitational encounter is known to lead to such drastic phenomena as core collapse. Such an artificial core collapse process appears to link the two problems together in the bottom-up scenario of structure formation in the ACDM universe. The discovery of this bias also has implications on the applicability of the Jeans theorem in galactic dynamics.     

Encapsulation of Labetalol, Pseudoephedrine in β-cyclodextrin Cavity: Spectral and Molecular Modeling Studies

The absorption and fluorescence spectra of labetalol and pseudoephedrine have been studied in different polarities of solvents and β-cyclodextrin (β-CD). The inclusion complexation with β-CD is investigated by UV-visible, steady state and time resolved fluorescence spectra and PM3 method. In protic solvents, the normal emission originates from a locally excited state and the longer wavelength emission is due to intramolecular charge transfer (TICT). Labetalol forms a 1:2 complex and pseudoephedrine forms 1:1 complex with β-CD. Nanosecond time-resolved studies indicated that both molecules show triexponential decay. Thermodynamic parameters (ΔG, ΔH, ΔS) and HOMO, LUMO orbital investigations confirm the stability of the inclusion complex. The geometry of the most stable complex shows that the aromatic ring is deeply self included inside the β-CD cavity and intermolecular hydrogen bonds were established between host and guest molecules. This suggests that hydrophobic effect and hydrogen bond play an important role in the inclusion process.     

Computer Modelling of Metal Dissolution in the Presence of Aqueous Electrolyte

The semi-empirical Hartree-Fock intermediate neglect of differential overlap (INDO) method was used to explore the potential energy surface of adsorbed water molecules and to speculate,using fairly simple chuster models,on the reaction path followed by metal ions leaving the surface.As an example,INDO calculations were used to calculate the potential energy curve for a metal atom leaving the surface and entering into a solvation cage composed of tetrahedral arranged water molecules.The effect of adding a NaCl ion pair to the system with the halide ion above the dissolving atom was also explored.     

Dielectric behaviour of α-cyclodextrin,heptakis (2,3,6-tri-Omethyl)-β-cyclodextrin,randomly methylated β-cyclodextrin and low frequency Raman spectra of α- and β-cyclodextrins

The frequency and temperature dependence of the real (?′) and imaginary (?″)parts of the dielectric constant of α-cyclodrextrin (form 1; α-CD. 5.9H₂O) and α-cyclodextrin (form III; α-CD.7.6H₂O) and of the corresponding dried forms (α-CD.1.1H₂O, α-CD.2.9H₂O, respectively) has been investigated over the frequency range 0–100 k Hz and temperature range 130–350 K. In addition the dielectric behaviour has been investigated of heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (β-CD.TRIME. 0.3H₂O) and randomly methylated β-cyclodextrin (β-CD.RAME.0.8H₂O). The dielectric behaviour is described well by Debyetype relaxation (α-disperson). All α-CD systems exhibit an additional ω-dispersion at low frequencies, which is attributed to proton transport. The fact that the ?′ values of α-CD form III are larger than those of α-CD form I is attributed to the different numbers and different strengths of the intramolecular hydrogen bonds. Form III has a stable conformation which is shown by the constant values of ?′ in the temperature range 125–250 K. By contrast, in form I the ?′ values increased linearly with temperature, indicating that the system passed through succesive conformations. The temperature dependence of ?″ and phase shift ∞ in all the specimens of α-CD (forms I, III) and fully methylated β-CD do not reveal any orderdisorder transition, because the developed hydrogen bonds ae not of the flip-flop type according to their crystal structures. The partially methylated β-CD reveals the characteristics of the order-disorder transition, which was observed before in the systems dried β-CD.2H₂O and non-dried β-CD.9.8H₂O. There is a direct relation between the hydroxyl groups of β-CD and the order-disorder transition. The order-disorder transition could also be shown in dried β-CD.2.4H₂O and non-dried β-CD.9.8H₂O samples but not in dried α-CD.1.1H₂O and non-dried a-CD.5.9H₂O samples, by low frequency Raman spectroscopy (< 180 cm^?1). The step-like temperature dependence of the band at 33.7cm^?1 reveals a transition at about 223K for both β-CD samples. In the case of α-CD samples the almost linear temperature dependence of the band at 49.1 cm^?1 does not reveal any transition.     

Generalized Brans-Dicke Cosmology in the Presence of Matter and Dark Energy

We study the Generalized Brans-Dicke cosmology in the presence of matter and dark energy. Of particular interest for a constant Brans-Dicke parameter, the de Sitter space has also been investigated.     

Reducing the Entropic Uncertainty via Non-Markovian Effect and Detuning in the Presence of Quantum Memory ∗

The influence of non-Markovian effect and detuning on the entropic uncertainty in the presence of quantum memory is studied by the time-convolutionless master-equation approach. The result shows that the entropic uncertainty in the presence of quantum memory is obviously dependent on both detuning and non-Markovian effect. The bigger the detuning is and the stronger the non-Markovian effect is, the smaller the entropic uncertainty is. Its physical explanation is that the known quantum information stored in the quantum memory can reduce or eliminate the entropic uncertainty about the measurement outcomes of another particle, which is entangled with the quantum memory.