Photophysical Characterization of Insulin Denaturation and Aggregation at Hydrophobic Interfaces

Abstract

The peak III/I ratio of pyrene monomer fluorescence was used to characterize surface-induced insulin denaturation and aggregation. An indicator of the hydrophobicity of pyrene's microenvironment, the IIM ratio can be used to study self-association of amphipathic molecules. In sodium lauryl sulfate (NaLS), the III/I ratio was 0.71 below the critical micelle concentration (CMC) and increased to 0.98 when the concentration was above the CMC. When insulin was placed in a polystyrene cuvet for 2 days at 37°C, the IWI ratio decreased from 0.84 to 0.78. The decrease in III/I ratio corresponds to surface-induced denaturation of insulin which exposed pyrene to a more polar environment. Increasing the duration of incubation for up to 12 days increased the III/I ratio to 1.06. Increased hydrophobicity of pyrene's environment correlates with the self-association of insulin. Once the aggregates reached a critical size, they began precipitating as was evident by an increase in the turbidity (absorbance at 600 nm) of solution. The results of this study support previous hypothesis that the aggregation and precipitation of insulin at hydrophobic interfaces is initiated by adsorption and surface-induced denaturation.     

利用APT研究RPV模拟钢中相界面原子偏聚特征

提高了Cu含量的核反应堆压力容器(RPV)模拟钢经调质处理(880℃保温0.5h,水淬;660℃保温10h)以及400℃时效1000h后,采用原子探针层析技术(APT)研究了碳化物/α-Fe基体,富Cu相/α-Fe基体以及富Cu相/碳化物界面处溶质或杂质原子的偏聚特征。结果表明:在碳化物/α-Fe基体界面处P原子偏聚最明显;在富Cu相/α-Fe基体界面处Ni原子偏聚最明显,Mn原子也有微弱的偏聚;在富Cu相/碳化物界面处未发现溶质或杂质原子的偏聚现象。不同相界处原子偏聚不仅与界面本身微观结构有关,也与相界附近化学特性有关。     

表面疏水纳米碳酸钙制备及表征

采用3-氨丙基三乙氧基硅烷（APTES）、3-巯丙基三乙氧基硅烷（MPTES）、3-甲基丙烯酰氧基丙基三甲氧基硅烷（KH570）3种硅烷偶联剂,对纳米碳酸钙进行表面改性,制备了具有表面疏水性能的纳米碳酸钙。采用红外光谱仪器与接触角测定仪对玫性前后的纳米碳酸钙进行了表征与比较,结果表明：硅烷偶联剂能成功连接到纳米碳酸钙表面;3种硅烷改性剂中,KH570改性后的接触角最大,改性效果最好;表面疏水改性有助于提高纳米碳酸钙在亲油相和在有机相中的分散性能。     

Adsorption of Gelatin at Solid-liquid Interfaces

Abstract

The adsorption of acid processed gelatin on to silica has been studied from the aqueous solution of gelatin at room temperature (25 °C). Various adsorption and kinetic parameters have been evaluated, such as the adsorption coefficient, rate constants for the adsorption and desorption, and diffusion constants and the effects of different factors on the extent of adsorption have been studied such as the pH of the solution, presence of inorganic salts and solvents, and temperature of the reaction medium.     

Discovering Reactant Supply Pathways at Electrode/PEM Reaction Interfaces Via a Tailored Interface-Visible Characterization Cell

In situ and micro-scale visualization of electrochemical reactions and multiphase transports on the interface of porous transport electrode (PTE) materials and solid polymer electrolyte (SPE) has been one of the greatest challenges for electrochemical energy conversion devices, such as proton exchange membrane electrolyzer cells (PEMECs), CO₂ reduction electrolyzers, PEM fuel cells, etc. Here, an interface-visible characterization cell (IV-CC) is developed to in situ visualize micro-scaled and rapid electrochemical reactions and transports in PTE/SPE interfaces. Taking the PEMEC of a green hydrogen generator as a study case, the unanticipated local gas blockage, micro water droplets, and their evolution processes are successfully visualized on PTE/PEM interfaces in a practical PEMEC device, indicating the existence of unconventional reactant supply pathways in PEMs. Further comprehensive results reveal that PEM water supplies to reaction interfaces are significantly impacted with current densities. These results provide critical insights about the reaction interface optimization and mass transport enhancement in various electrochemical energy conversion devices.     

Interfacial Phase Transitions at Solid-Fluid and Liquid-Vapor Interfaces

To study the interface between a solid surface and nitrogen vapor, the theory of Cahn was applied. The Peng-Robinson equation of state (PREOS) was incorporated in the theory of Cahn to model the thermodynamic functions of the fluid. In this study the wetting transition, as earlier reported by Cahn, was shown. In addition, wetting transitions occurring at a liquid-vapor interface of the three-phase LLV equilibrium of the binary mixtures hexane/water and benzene/water were examined. It was found that by making use of the gradient theory of van der Waals, in which the PREOS was incorporated, the transitions seem to be of third order. For the case where the PREOS was replaced by the Associated-Perturbed-Anisotropic-Chain-Theory, no wetting region was found. It was argued that, in principle, it should he possible to model first-order wetting transitions with the square gradient theory.     

憎水二氧化硅膜的制备、表征及水热稳定性研究

用甲基三乙氧基硅烷(MTES)代替部分正硅酸乙酯(TEOS)作为前驱物,通过共水解缩聚反应可制得甲基修饰的二氧化硅膜.通过TGA、FTIR以及气体渗透等测试手段对甲基修饰的SiO₂膜进行研究,发现随着MTES/TEOS摩尔比例的增大,二氧化硅膜的憎水性能逐渐增强,当MTES/TEOS达到0.8时,二氧化硅膜的孔表面几乎不再吸附水气.氢气在MTES/TEOS为1的支撑体二氧化硅膜的输运受温度的控制,200℃时H₂的渗透率达到6.0×10^-7mol·m^-2.Pa^-1·s^-1,H₂/CO₂分离系数达到6.0,于200℃以及水蒸气压力为3564Pa的环境中陈化近110h后H2渗透率基本保持不变,H₂/CO₂分离系数有所增大,说明经过甲基修饰的二氧化硅膜比纯二氧化硅膜具有更好的水热稳定性.     

直接沉淀法制备疏水性氢氧化镁及其表征

以苦卤和氨水为原料,硬脂酸镧为改性剂,采用常温一步直接沉淀法制备疏水性氢氧化镁纳米粒子;用扫描电子显微镜、傅里叶红外光谱、热重分析、X射线衍射、疏水性分析等手段对所得产物进行表征分析并进行疏水性测试。结果表明,在合成的过程中,硬脂酸镧通过化学反应改变了氢氧化镁的表面性质,改性后的Mg(OH)2为非极性,可漂浮在水面,表现为疏水性;硬脂酸镧并未改变Mg(OH)2的晶型,但是在X射线衍射中出现La(OH)3的杂质峰;硬脂酸根离子吸附在Mg(OH)2纳米粒子表面,使其表面有机化,同时提高了分散性和热稳定性。     

Reactions and Microstructure at Selected Ceramic/Metal Interfaces

The reactions of Ti and Zr with A1N, Al₂0₃and mullite were studied. The substrates were selected to represent a simple nitride (A1N), a simple oxide (Al₂O₃), and a complex oxide (mullite). The activities of the Ti and Zr were varied by dissolving them at 1 and 5 wt% in the 72Ag-28Cu eutectic composition, which is otherwise unreactive with the ceramics. Reactions were studied by measuring the variation of the alloy contact angle on the ceramic with time at temperature and by determining the compositions of interfacial reaction products. The reaction products were determined by SEM-liDS, EPMA and XRD analysis. Contact angles were lower for Ti alloys than for those containing Zr. Reaction products were primarily the nitrides of Zr and Ti for reaction with A1N and the respective oxides for reaction with A1₂0₃. Complex alloy phases were found in the metal away from the ceramic-metal reaction zone.     

Monte Carlo Modeling of Phonons at Crystal Interfaces

One of the strategies in the effort to directly detect dark matter particles is to measure the phonon and charge signals produced in an incidental collision of a weakly interacting massive particle with a nucleon in a crystalline detector. Proper calibration of the detected phonon energy relies on detailed models of phonon propagation through the crystal to the instrumented surface. Previous Detector Monte Carlo incorporate probabalistic anharmonic decay and mass defect scattering but neglect the mode dependent scattering at crystal boundaries. We calculate mode specific reflection and transmission at detector interfaces with a simple acoustic mismatch model. We find that mode preserving transmission is the most probable outcome at germanium-aluminum detector interfaces, but the probability of reflection is not negligible. The average phonon reflection probability at near normal angles of incidence at a Ge/Al interface is near 20 %, but grows dramatically for oblique incidence. We develop a code using Geant4, which should allow modeling extensions to all phonon mediated dark matter detection schemes. Our models are adaptable to other crystal materials and are generally useful in any phonon interface problem.     

魔芋葡甘聚糖基缓释膜材料的结构表征

以魔芋葡甘聚糖和大豆油为原料通过碱催化制备魔芋葡甘聚糖脂肪酸酯疏水膜(F-KGM);采用紫外-可见分光光度计、傅立叶变换红外光谱仪、十八角静态激光光散射仪、X射线衍射仪、热分析仪和扫描电子显微镜对其进行结构表征。结果表明,F-KGM的重均分子量(-Mw)为3.653×106g/mol,明显高于KGM的1.619×106g/mol,魔芋葡苷聚糖与脂肪酸分子形成酯键,KGM经酯化后,改变了原有的晶体结构,结晶度降低,具有更高的热稳定性,分子乳化融合流延成膜过程中发生分子自组装行为,形成性质稳定且具有良好疏水性能的缓释膜材料。     

Electron Energetics at Surfaces and Interfaces: Concepts and Experiments

We present a concise, although admittedly non‐exhaustive, but hopefully didactic review and discussion of some of the central and basic concepts related to the energetics of surfaces and interfaces of solids. This is of particular importance for surfaces and interfaces that involve organic molecules and molecular films. It attempts to pull together different views and terminologies used in the solid state, electrochemistry, and electronic device communities, regarding key concepts of local and absolute vacuum level, surface dipole, work function, electron affinity, and ionization energy. Finally, it describes how standard techniques like photoemission spectroscopy can be used to measure such quantities.     

Monolayers of Linear Saturated Succinate Polyesters at Air-Liquid Interfaces

The surface pressure-area isotherms at 25 °C are reported for some linear saturated polyesters spread as monolayers at air-aqueous interfaces. Monolayers of poly (ethylene succinate), poly (pentamethylene succinate), and poly (neopentyl succinate) were studied on distilled water and 0.01 N hydrochloric acid subphases.Poly (ethylene succinate) monolayers are in the expanded state and collapse at low surface pressures. Poly (pentamethylene succinate) monolayers are also expanded, but show no definite collapse, even at the highest surface pressures studied. Monolayers of poly (neopentyl succinate) collapse at high surface pressures, and are less expanded, over the entire surface pressure range studied, than the monolayers of the other polymers studied. The specific area for each polymer and the effect of structure on the surface pressure-area isotherms of poly (pentamethylene succinate) and poly (neopentyl succinate) are discussed.     

Aggregation of cyanine dyes at Langmuir-Blodgett monolayers

Cyanine dyes are adsorbed from aqueous solution to Langmuir-Blodgett (LB) films, forming monolayers of Scheibe or J aggregates, whereas the dye in solution is in monomeric state. As well as J aggregates other types of aggregates (H, H^* aggregates, oligomers, dimers) can form and interchange at the LB interface depending on conditions and the structures of the dyes and amphiphiles. Reflection spectroscopy proved to be a useful method for studying aggregates and kinetic processes at the air-water interface as the bulk subphase is not recorded by this method.

Aggregation of dyes seems to be controlled by Coulomb interactions and the surface structure of the interacting monolayers. Cationic cyanine dyes are adsorbed only at negatively charged monolayers (e.g. fatty acids) whereas cyanine dyes with negative net charge form aggregates only at positively charged monolayers (e.g. amphiphilic ammonium salts).

Aggregation of cyanine dyes has also been found at LB monolayers of amphiphilic nucleic acids which have been synthesized for the first time. Aggregates of adsorbed cyanine dyes can be transferred to solid substrates by the LB method and investigated by other spectroscopic methods or microscopy.

Adsorption of cyanine dyes at vesicle bilayers has been reported; this was studied by absorption spectroscopy of vesicular dye solutions. Comparison of these spectra with reflection spectra of corresponding LB films reveals significant differences between the effects in LB monolayers and those in vesicular bilayers.     

Self‐Assembly of Graphene Oxide at Interfaces

Due to its amphiphilic property, graphene oxide (GO) can achieve a variety of nanostructures with different morphologies (for example membranes, hydrogel, crumpled particles, hollow spheres, sack‐cargo particles, Pickering emulsions, and so on) by self‐assembly. The self‐assembly is mostly derived from the self‐concentration of GO sheets at various interfaces, including liquid‐air, liquid‐liquid and liquid‐solid interfaces. This paper gives a comprehensive review of these assembly phenomena of GO at the three types of interfaces, the derived interfacial self‐assembly techniques, and the as‐obtained assembled materials and their properties. The interfacial self‐assembly of GO, enabled by its fantastic features including the amphiphilicity, the negatively charged nature, abundant oxygen‐containing groups and two‐dimensional flexibility, is highlighted as an easy and well‐controlled strategy for the design and preparation of functionalized carbon materials, and the use of self‐assembly for uniform hybridization is addressed for preparing hybrid carbon materials with various functions. A number of new exciting and potential applications are also presented for the assembled GO‐based materials. This contribution concludes with some personal perspectives on future challenges before interfacial self‐assembly may become a major strategy for the application‐targeted design and preparation of functionalized carbon materials.