Characterization of heterogeneous interaction in binary mixtures of ethylene glycol oligomer with water, ethyl alcohol and dioxane by dielectric analysis

The associating behaviour of the binary mixtures of ethylene glycol oligomer (EGO), i.e. ethylene glycol (EG), diethylene glycol (DEG) and poly(ethylene glycol)s (PEG200, PEG300, PEG400 and PEG600) with water (W), ethyl alcohol (EA) and 1,4-dioxane (DX) over the entire concentration range at 25 °C have been investigated through their accurately measured values of dielectric constant. The static dielectric constant ε_o, high frequency limiting dielectric constant ε_∞, dielectric relaxation strength Δε, excess dielectric parameters ε^E₀ and ε^E_∞, effective Kirkwood correlation factor g^eff and corrective correlation factor g_f of EGO–W, EGO–EA and EGO–DX mixtures were determined to obtain qualitative and quantitative information about the complex formation through H-bond in these systems. Most of the evaluated dielectric parameters of EG and DEG in different ‘cosolvents’ have different characteristics as compared to the PEG–cosolvent mixture. The observed linear and non-linear behaviour of Δε against EGO monomer unit mole fraction X confirms the variation in the homogeneous structures in their binary mixtures with concentration variation. Appearance of the maximum in ε^E₀ against X plots indicates that a complex stable adduct is formed in the EGO–W mixtures at stoichiometric ratio 1:1.7 for lower oligomers but this ratio seems to be 1.7:1 for higher EGO molecules, which confirms that the EGO size and chain flexibility affects the complex formation between EGO and W. In case of EG–EA mixture 1:1 stoichiometric ratio form stable adduct whereas for higher EGO–EA, it is 3:1, at EGO monomer unit level. The complex formation behaviour of DEG–EA has entirely different characteristics when compared to the other studied EGO–EA mixtures. Although, 1,4-dioxane has weak polar behaviour dielectric properties of EG–DX and DEG–DX confirm the formation of stable adducts at the stoichiometric ratio 2:1 of EGO monomer unit mole fraction to the DX. For the higher EGO–DX mixtures, stable adduct forms at the stoichiometric ratio 9:1. Except DEG–EA mixtures, the EGO–W and EGO–EA form the complex with reduction in the effective number of dipoles. In EG–DX mixtures, the heterogeneous species form with a large reduction in the effective number of dipoles, which changes as the effective number of dipoles increases with the increase in monomer repeat units of EGO. Further the net electronic polarization in these binary mixtures increases due to heterogeneous interaction over the entire mixing concentration range.     

Destabilization of artificial biomembrane induced by the penetration of tryptophan

The effect of tryptophan on the membrane stability was studied by using three artificial biological membranes including liposome, Langmuir monolayer and solid supported bilayer lipid membrane (s-BLM) as models. All the results indicate that the penetration of tryptophan can destabilize different artificial biological membranes. The diameter of liposome and the leakage of calcein from liposome increased with the increase of tryptophan concentration because the penetration of tryptophan was beneficial for dehydrating the polar head groups of lipids and the formation of fusion intermediates. π-A isotherms of lecithin on the subphase of tryptophan solution further confirm that tryptophan can penetrate into lipid monolayer and reduce the stability of lipid monolayer. When the concentration of tryptophan increased from 0 to 2 × 10⁻³ mol L⁻¹, the limiting molecular area of lecithin increased from 110.5 to 138.5 Å², but the collapse pressure of the monolayer decreased from 47.6 to 42.3 mN m⁻¹, indicating the destabilization of lipid monolayer caused by the penetration of tryptophan. The resistance spectra of s-BLM demonstrate that the existence of tryptophan leads to the formation of some defects in s-BLM and the destabilization of s-BLM. The values of electron-transfer resistance and double layer capacitance respectively decreased from 5.765 × 10⁶ Ω and 3.573 × 10⁻⁸ F to 1.391 × 10⁶ Ω and 3.340 × 10⁻⁸ F when the concentration of tryptophan increased from 0 to 2 × 10⁻³ mol L⁻¹. Correspondingly, the breakdown voltage of s-BLM decreased from 2.51 to 1.72 V.     

Ultrasonic and DFT study of intermolecular association through hydrogen bonding in aqueous solutions of glycerol

The experimental measurements of density, viscosity and ultrasonic velocity of aqueous glycerol solutions were carried out as functions of concentration (0.1 ≤ m [mol kg^− 1] ≤ 1.0) and temperature (303.15 ≤ T [K] ≤323.15). The isentropic compressibility (β_s), acoustic impedance (Z), hydration number (H_n), intermolecular free length (L_f), classical sound absorption (α/f²)_class and shear relaxation time (τ) were calculated by using the measured data. These parameters have been interpreted in terms of solute–solvent interactions. The quantum chemical calculations were performed to study the hydrogen bonding in interacting complex formed between glycerol and water molecules. Computations have been done by using Density Functional Theory (DFT) method at B3LYP/6–31 + g(d) level of theory to study the equilibrium structure of glycerol, glycerol–water interacting complex and vibrational frequencies. The solution phase study was carried out using Onsager's reaction field model in water solvent. The computed vibrational frequencies are in good agreement with the main features of the experimental spectrum when four water molecules are considered explicitly with glycerol. The interaction energy (E_total), hydrogen bond lengths and dipole moment (µ_m) of the interacting complex are also presented and discussed with in the light of solute–solvent interactions.     

An analysis of the beam interaction characteristics of selected lasers with an alpha-alumina bioceramic

Certain differences between the interaction characteristics of a CO₂ laser, a Nd:YAG laser and a high power diode laser with an alpha-alumina bioceramic have been investigated. For each laser the fluence threshold values at which significant material removal occurs were found graphically. Through the implementation of a derivative of Beer–Lambert's law, the laser beam absorption lengths were calculated along with the thermal loading values. An examination of the laser-induced meltpool propagation in the alpha-alumina revealed good agreement with the Stefan solution to the heat diffusion equation for the lasers. Absorptivity measurements revealed that there was no correlation between the actual absorptivity of the alpha-alumina and the absorption length for each of the three lasers on account of the absorptivity measurements being similar for each laser. However, differences in the depth of melting experienced by the alpha-alumina meant that it is reasonable to assume that absorption length is the principal influence on the melt depth.     

哈密顿正则方程在生物膜与胶体粒子相互作用研究中的应用

介绍经典分析力学中的哈密顿正则方程在生物膜与胶体粒子相互作用研究中的一个具体应用.由Helfricb理论模型得到体系的哈密顿,用正则方程给出一组常微分方程,并用打靶法对其进行求解得到体系的稳定构型随膜参数变化的规律.     

相互作用势对模拟计算单壁碳纳米管物理吸附储氢的影响

采用巨正则Monte Carlo方法模拟氢分子在单壁碳纳米管中的储存与分布,重点研究了Lennard-Jones势、Crowell-Brown势和Silvera- Goldman势对模拟计算单壁碳纳米管物理吸附储氢的影响.计算结果显示,碳纳米管与氢分子间的相互作用宜采用Lennard-Jones势描述;氢分子与氢分子间相互作用的描述则与碳纳米管的管径有关,管径较小时选Lennard-Jones势较佳,管径偏大时取七参数Silvera-Goldman 势更为合理,而三参数Silvera-Goldman势则不宜采用;并给出了相应的理论解释.     

Magnetic resonance imaging of isolated single liposome by magnetic resonance force microscopy

Magnetic resonance imaging (MRI) is very useful spectroscopy to visualize a three-dimensional (3D) real structure inside the sample without physical destruction. The spatial resolution of the readily available MRI spectrometer is, however, limited by a few ten to hundreds of microns due to a technological boundary of generating larger magnetic field gradient and to the insensitivity inherent to the inductive signal detection. Magnetic resonance force microscopy (MRFM) is new alternative MRI spectroscopy which is anticipated to significantly surpass the conventional MRI in both resolution and sensitivity. We report two imaging experiments on our MRFM spectrometer operated at room temperature and in vacuum approximately 10(-3)Pa. One is for approximately 20 microm liposome membrane labeled entirely by a nitroxide imaging agent and the other for approximately 15 microm DPPH particles, both are nearly the same size as that of human cell. The reconstructed images at spatial resolution approximately 1 microm were in satisfactory agreement with the scanning electron microscope images. The potential capability of visualizing intrinsic radicals in the cell is suggested to investigate redox process from a microscopic point of view.     

Fluorimetric study of interaction of benzidine with trypsin

The interaction of benzidine (BEN) with trypsin was studied by fluorescence spectrum. It was shown that BEN has quenched the fluorescence launching from trypsin by reacting with it and forming a certain kind of new complex. The quenching and energy transfer mechanisms were discussed. The binding constants and thermodynamic parameters at three different temperatures, the binding locality, and the binding power were obtained. The conformation of trypsin was discussed by synchronous and three-dimensional fluorescence techniques.     

带电纳米颗粒与相分离的带电生物膜之间相互作用的分子模拟

纳米颗粒在纳米医药、细胞成像等领域有着非常广泛的应用,深入理解纳米颗粒与生物膜之间相互作用的微观机制是纳米颗粒合成与应用的重要基础.本文采用粗粒化分子动力学模拟的方法研究了带电配体包裹的金纳米颗粒与相分离的带电生物膜之间的相互作用.结果表明,通过改变金纳米颗粒表面的配体密度、配体带电种类和比例,以及膜内带电脂分子的种类,可以方便地调控纳米颗粒在膜表面或膜内停留的位置和状态.进一步从自由能的角度分析了带电纳米颗粒与带电生物膜之间相互作用的微观物理机制.本文对纳米粒子在纳米医药、细胞成像等领域的应用具有一定的理论参考意义.     

RSM and ANN modeling-based optimization approach for the development of ultrasound-assisted liposome encapsulation of piceid

Piceid, a naturally occurring derivative of resveratrol found in many plants, has recently been considered as a potential nutraceutical. However, its poorly water-soluble property could cause a coupled problem of biological activities concerning drug dispersion and absorption in human body, which is still unsolved now. Liposome, a well-known aqueous carrier for water-insoluble ingredients, is commonly applied in drug delivery systems. In this study, a feasible approach for solving the problem is that the targeted piceid was encapsulated into a liposomal formula as aqueous substrate to overcome its poor water-solubility. The encapsulation process was assisted by ultrasound, with investigation of lipid content, ultrasound power and ultrasound time, for controlling encapsulation efficiency (E.E%), absolute loading (A.L%) and particle size (PS). Moreover, both RSM and ANN methodologies were further applied to optimize the ultrasound-assisted encapsulation process. The data indicated that the most important effects on the encapsulation performance were found to be of lipid content followed by ultrasound time and ultrasound power. The maximum E.E% (75.82%) and A.L% (2.37%) were exhibited by ultrasound assistance with the parameters of 160 mg lipid content, ultrasound time for 24 min and ultrasound power of 90 W. By methodological aspects of processing, the predicted E.E% and A.L% were respectively in good agreement with the experimental results for both RSM and ANN. Moreover, RMSE, R² and AAD statistics were further used to compare the prediction abilities of RSM and ANN based on the validation data set. The results indicated that the prediction accuracy of ANN was better than that of RSM. In conclusion, ultrasound-assisted liposome encapsulation can be an efficient strategy for producing well-soluble/dispersed piceid, which could be further applied to promote human health by increased efficiency of biological absorption, and the process of ultrasound-mediated liposome encapsulation can be well established by a methodological approach using either RSM or ANN, but it is worth mentioning that the ANN model used here showed the superiority over RSM for predicting and optimizing encapsulation.     

超声增强脂质体与细胞相互作用的研究

理论及实验研究了超声增强脂质体与细胞的相互作用.实验制作了包裹荧光素的脂质体,利用1 MHz聚焦超声增强脂质体与乳癌细胞的相互作用,采用荧光显微镜观察与荧光素结合前后细胞的变化,流式细胞仪定量检测细胞中包含的荧光素.结果表明,在声压幅度为0.24 MPa超声作用40 s后,细胞吸收荧光素能力比对照组（无超声作用）有8.78％的提高.理论讨论了超声增强脂质体与细胞相互作用的可能物理机制,指出超声诱发的脂质体运动及脂质体的粒径变化是超声增强脂质体与细胞相互作用的原因. 关键词： 脂质体 药物传递 超声辐射力     

2,7-二氯荧光素与蛋白质相互作用的分光光度法研究

首次采用分光光度法研究了模拟生理条件(pH 7.4 Tris-HCl缓冲溶液,离子强度I=0.1)下2,7-二氯荧光素与牛血清白蛋白(BSA)相互作用的情况.研究结果表明:两者相互作用形成稳定的复合物,最大吸收波长为509nm,与2,7-二氯荧光素的最大吸收波长502nm比较,红移了7nm;两者之间主要通过静电引力结合,但并不排除疏水作用力和氢键;两者之间的结合数为32.     

Fluorescence quenching of betacarboline (9H-pyrido[3,4-b]indole) induced by intermolecular hydrogen bonding with pyridines

The influence of the hydrogen bond acceptor properties of pyridine derivatives on the fluorescence quenching mechanism of the betacarboline (9H-pyrido[3,4-b]indole) (BC) has been investigated. Absorption measurements suggest the sequential formation of two BC-pyridine hydrogen-bonded complexes: a covalent hydrogen-bonded complex (HBC) and its proton transfer tautomer (PTC). Steady-state and time-resolved fluorescence measurements reveal that the BC fluorescence quenching has static and dynamic components due to the ground and the excited state formation of the very weakly fluorescent PTC. Since the excited state HBC formation is a diffusion-controlled process, the efficiency of dynamic quenching is mainly determined by the relative magnitudes of the HBC backward reaction and the PTC formation rate constants.     

Testing the interaction model with cosmological data and gamma-ray bursts

We use the new gamma-ray bursts (GRBs) data, combined with the baryon acoustic oscillation (BAO) observation from the spectroscopic Sloan digital sky survey (SDSS) data release, the newly obtained A   parameter at z=0.6$z=0.6$ from the WiggleZ dark energy survey, the cosmic microwave background (CMB) observations from the 7-year Wilkinson microwave anisotropy probe (WMAP7) results, and the type Ia supernovae (SNeIa) from Union2 set, to constrain a phenomenological model describing possible interactions between dark energy and dark matter, which was proposed to alleviate the coincidence problem of the standard ΛCDM model. By using the Markov chain Monte Carlo (MCMC) method, we obtain the marginalized 1σ   constraints _Ωm=0.2886±0.0135${\Omega }_m=0.2886\pm 0.0135$, _rm=−0.0047±0.0046$r_m=-0.0047\pm 0.0046$, and _wX=−1.0658±0.0564$w_X=-1.0658\pm 0.0564$. We also consider other combinations of these data for comparison. These results show that: (1) the energy of dark matter is slightly transferring to that of dark energy; (2) even though the GRBs + BAO + CMB data present less stringent constraints than SNe + BAO + CMB data do, the GRBs can help eliminate the degeneracies among parameters.     

The interaction region of the large detector concept

The recently optimised interaction region of the LDC detector is presented in this paper together with the requirements for the planned detector hall.      

An interaction potential based lattice Boltzmann method with adaptive mesh refinement (AMR) for two-phase flow simulation

The lattice Boltzmann method (LBM) for two-phase flow simulation is often hindered by insufficient resolution at the interface. As a result, the LBM simulation of bubbles in bubbling flows is commonly limited to spherical or slightly deformed bubble shapes. In this study, the adaptive mesh refinement method for the LBM is developed to overcome such a problem. The approach for this new method is based on the improved interaction potential model, which is able to maintain grid-independent fluid properties in the two-fluid phases and at the interface. The LBM–AMR algorithm is described, especially concerning the LBM operation on a non-uniform mesh and the improved interaction potential model. Numerical simulations have been performed to validate the method in both single phase and multiphase flows. The 2D and 3D simulations of the buoyant rise of bubbles are conducted under various conditions. The agreement between the simulated bubble shape and velocity with experiments illustrates the capability of the LBM–AMR approach in predicting bubble dynamics even under the large bubble deformation conditions. Further, the LBM–AMR technique is capable of simulating a complex topology change of the interface. Integration of LBM with AMR can significantly improve the accuracy and reduce computation cost. The method developed in this study may appreciably enhance the capability of LBM in the simulation of complex multiphase flows under realistic conditions.     

Studies on the arctiin and its interaction with DNA by spectral methods

The emission spectra of arctiin were determined under various experimental conditions. In addition, a fluorescence method was developed to obtain the binding constants and sites of the interaction between arctiin and DNA. A competitive binding experiment and melting temperature mensuration were carried out to investigate the binding mechanism of arctiin and DNA. The experimental results showed that the interaction between arctiin and DNA belongs to a groove binding mode.     

Selective hydrogen bond disruption in adenine monolayer films by reaction with water

High-resolution X-ray photoelectron spectroscopy of two-dimensional films of adenine on a highly oriented pyrolitic graphite [0 0 0 1] surface reveal bonding changes induced by exposure to water. The hydrogen-bond interactions between adenine molecules were replaced by adenine–water hydrogen bonds in a stepwise pattern. This reaction destroyed the film network and changed the chemical state of the nitrogen sites. The reaction with water molecules affected both the donor and acceptor states of the oxygen atoms, as compared to those in water.     

已知结构的短肽段的不同位点之间氨基酸残基的相关性

构筑了一个9个残基长度的短肽段库，根据短肽段的结构把它们分成不同的簇，用卡方分析每个簇，鉴别不同位点之间的相关性．同时还构筑了一个序列比对的评分函数，这个评分函数不但包含单个位点的信息，也包含不同位点之间相关性的信息．结果表明, 位点之间的相关性能够提供一些新颖的信息，这些信息一般都与短肽段不同位点之间的相互作用有关，相关性信息的引入能够明显的提高短肽段结构的预测准确度．     

Spectroscopic Studies of Intra- and Inter-Molecular Hydrogen Bonding of Some O-Hydroxylbenzenesulfonanilides in Solutions

The effect of solvent on the electronic spectra of some fasciolici-dal o–-hydroxylbenzenesulfonanilides is examined and discussed. It is revealed that in solution these compounds exist in both intramolecular hydrogen bond form and intermolecular hydrogen bond form occurring between solute and solvent molecule. In solutions containing large amount of apolar aprotic solvents such as dioxane, compounds studied are mainly intramolecular hydrogen bond form and exhibit a weak transition band which is presumably attributed to the transition of n-electrons of oxygen atom in the intramolecular hydrogen bonded six-membered ring of the compounds.