Circular patterns of calcium oxalate crystals induced by defective Langmuir-Blodgett film

The injury of the renal epithelial cell membrane can promote the nucleation of nascent crystals, as well as adhesion of crystals on it. It thus accelerates the formation of renal calculi. In this paper, the defective Langmuir-Blodgett (LB) films were used as a model system to simulate the injured renal epithelial cell membrane. The microcosmic structure of the defective LB film and the molecular mechanism of the effect of this film on nucleation, growth, deposited patterns and adhesion of calcium oxalate monohydrate (COM) were investigated. The circular defective domains were formed in dipalmitoylphosphatidylcholine (DPPC) LB film after the film was treated by potassium oxalate. These domains could induce ring-shaped patterns of COM crystals. In comparison, the LB film without pretreatment by potassium oxalate only induced random growth of hexagonal COM crystals. As the crystallization time increased, the size of COM crystals in the patterns increased, the crystal patterns changed from empty circles to solid circles, and the number of the circular patterns with small size (5-20 μm) increased. The results would shed light on the molecular mechanism of urolithiasis induced by injury of the renal epithelial membrane at the molecular and supramolecular level.     

草酸钾诱导的LB膜缺陷及对草酸钙堆积图形的影响

采用扫描电子显微镜(SEM)和原子力显微镜(AFM)研究了经不同浓度草酸钾(K2C2O4)处理后二棕榈酰磷酯酰胆碱(DPPC)的缺陷LB膜及其对一水草酸钙(COM)成核和生长的影响. K2C2O4的处理可进一步破坏LB膜中圆形畴区内的分子列阵, 尤其是使处在液态扩张相(LE)/液态凝集相(LC)边界的分子列阵无序程度增加, 从而促进了COM晶体在此处的成核和生长, 最终诱导圆形堆积的COM晶体图形出现. 随着损伤LB膜的K2C2O4浓度c(K2C2O4)从0.3 mmol/L增加到5.0 mmol/L, 其对LB膜畴区有序结构的破坏作用逐渐增强, 圈状堆积的晶体图形数量增多. 当c(K2C2O4)为0.3 mmol/L时, 主要诱导实心的圆形堆积的COM晶体图形, 而当c(K2C2O4)增加至5.0 mmol/L时, 生成圈状COM晶体图形, 且图形的半径减小. 这一研究结果将有助于从分子和超分子水平上了解肾小管上皮细胞膜损伤后的微结构变化及其与肾结石形成的关系.     

缺陷LB膜诱导草酸钙晶体的生长

肾结石形成与肾上皮细胞膜损伤密切相关, 但细胞膜损伤后的微结构及其与肾结石微晶粘附的分子机制仍不清楚. 本文采用经草酸钾处理后存在缺陷的二棕榈酰磷酯酰胆碱(DPPC)的LB膜为模型, 采用原子力显微镜(AFM)、荧光显微镜和扫描电子显微镜(SEM)研究了模型膜的缺陷畴区及其对一水草酸钙(COM)晶体生长的促进作用. LB膜内圆形的缺陷畴区可以诱导圆形COM晶体图形生成, 圆形晶体图形的直径从3 mm到150 mm不等. 在圆形区域内, 单个COM晶体的尺寸大都在1～3 μm, 以针状、四边形或不规则的形状存在; 而在同等条件下正常LB膜诱导的COM晶体没有圆形聚集现象, 单个COM晶体在LE/LC相边界生长, 其尺寸显著增加至5～10 mm. 不同性质LB膜促进COM成核和生长的强弱依次为: 经草酸钾处理的LB膜缺陷畴区>>正常LB膜的LC/LE边界＞正常LB膜非边界区域>>无膜诱导. 从缺陷LB膜的活性位点及其对COM晶体成核的促进作用等方面讨论了上述实验结果.     

缺陷LB膜诱导特异形貌草酸钙堆积图形

A special pattern of calcium oxalate monohydrate (COM) crystals was induced by DPPC Langmuir-Blodgett films with defects. The pattern was that a large hexagonal COM crystal located in the middle of a ring-shaped pattern of needle-liked crystals. The number of such special patterns with a diameter between 10 μm and 40 μm accounted for about 5% of the whole crystal patterns. It is due to the “islands” composed of aggregated film-forming molecules in the middle of the liquid-condensed domains. The effects of the concentration of potassium oxalate and the growth time on the crystal patterns were studied. When the concentration of potassium oxalate(c_K2C2O4) was 0.6 mmol·L^-1, the needle-liked COM crystals on the rings grew towards inside part of the patterns as the induced-time increased from 1 h to 4 h. After 2 h, the solid circle patterns were formed. On the other hand, the size of the hexagonal COM crystal in the middle of the pattern increased. The size of the COM crystals on the rings were about 3 μm × 2 μm, and that of three-dimensional COM crystals in the middle of the patterns were about 16 μm × 7 μm × 6 μm after 4 h. However, when c_K2C2O4 was increased to 5.0 mmol·L^-1, there was only a large COM crystal grown in the middle of the circular COM crystallites no matter 1 h or 4 h of crystal growth, and the ratio of these special COM patterns increased. It can be explained that the interaction between oxalate and DPPC molecules is enhanced as the increase of c_K2C2O4, so more and more DPPC molecules fled away from the substrate surface, resulting in decrease of the nucleating sites in the circle.     

影响Langmuir-Blodgett膜中缺陷畴区的因素

采用扫描电子显微镜(SEM)和荧光显微镜研究了基片种类、温度、制膜参数(如Langmuir-Blodgett膜沉积压、压膜速度、提膜速度等)和LB膜层数对LB膜中缺陷畴区的影响及其对尿石矿物——水草酸钙(COM)晶体生长的指导作用. LB膜中的缺陷畴区可以诱导圆形COM沉积图形形成, 但在石英基片上的图形数量只有云母基片上的5%左右. 制膜温度由25 ℃降低至18 ℃时, 出现非圆形COM沉积图形, 尺寸亦有增大的趋势. 随着沉积压从2 mN/m增大到10 mN/m, 云母基片上圆形COM晶体沉积图形数量减少, 沉积图形尺寸趋于均一, 非圆形图形数量增加. 随着压膜速度增加, 膜中缺陷增加. 当LB膜的层数由1层增加到2, 3, 5层后, 其诱导的COM图形数量逐渐减少, 尺寸也相应减小, 即单层LB膜的缺陷比多层膜的多, 且更容易受到基片的影响.     

Structuring of tricarbocyanine dye molecules in Langmuir-Blodgett films

The problems of formation of stable Langmuir monolayers containingN-sulfopropyl substituted thiatricarbocyanine dyes are considered: the effects of the composition of the mixture applied on the surface of an aqueous subphase and of the extent of compression of the monolayer on processes of ordering of molecular structure. Dyes are introduced into complex monolayers at the water-air interface and then are transferred on solid substrates as multilayered Langmuir-Blodgett (LB) films. For the first time the formation of J-aggregates has been observed for two tricarbocyanine dyes. The structure of J-aggregates depends on the composition of the mixture and the value of the constant pressure at which the transfer occurs. LB films of J-aggregated dyes are optically anisotropic, which is related to the fact that they are formed in the monolayer on the surface and there is no interlayer aggregation during the transfer to substrates. Heterodimers are formed in complex monolayers containing oppositely charged ions of dyes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1278–1283, July, 1995.The work was partially financially supported by the Foundation for Basic Research of the State Committee on Science and Technologies of the Ukraine (Project No. 2.2/48 Normal').     

Inhibition of the crystal growth and aggregation of calcium oxalate by elemental selenium nanoparticles

Chemical modulation of calcium oxalate (CaC₂O₄) crystals morphologies by elemental selenium nanoparticles (nanoSe⁰) was investigated with scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), Fourier transform infrared spectrometry (FTIR), and X-ray diffraction (XRD) analysis. The coordination between nanoSe⁰ and C₂O₄²⁻ had great effect on the formation of CaC₂O₄ crystals. NanoSe⁰ inhibited the growth of calcium oxalate monohydrate (COM) crystals, prevented the aggregation of COM crystals and induced the formation of the spherical calcium oxalate dihydrate (COD) crystals containing selenium, which are the thermodynamically less stable phase and has a weaker affinity to the cell membranes than COM crystals. The inhibition of the crystal growth and aggregation of CaC₂O₄ crystals by nanoSe⁰ displayed concentration effects.     

Surface forces in foam films from DPPC and lung surfactant phospholipid fraction

Surface properties of foam films formed from aqueous dispersions of dipalmitoyl-phosphatidylcholine (DPPC) and from solutions of a phospholipid fraction of lung surfactant (TPL) are studied employing the foam film method. Experiments are carried out within a wide range of NaCl concentrations (C_el) and the ranges of C_el determining formation of common films (CF), common black films (CBF) and bilayer Newton black films (NBF) are found. The thickness (h) of the CF and CBF decreases with the increase of C_el until the critical electrolyte concentrations (C_{el, cr}) is reached. The determined C_{el, cr} that characterize the transition to NBF show that C_{el, cr} of the TPL films is an order of magnitude higher than that of the DPPC films. The measured h of the TPL films is higher than that of the DPPC films in the whole C_el range. Besides, only the h(C_el) curve of the DPPC films outlines a metastable C_el range where both CF and NBF are obtained. Both the h(C_el) curves and the direct measurements of the disjoining pressure isotherms of the DPPC films (Π(h) isotherms) demonstrate the role of electrostatic repulsive forces for the stability of the phospholipid films The obtained results are compared with the DLVO theory equations and the evaluated potentials of the diffuse electric layer φ₀  20 mV for the DPPC films and φ₀  100 mV for TPL films show the strong effect of the charged phospholipids in the TPL mixture on the electric properties at the film interfaces.     

Controlled growth of calcium oxalate crystal in bicontinuous microemulsions containing amino acids

The growth of calcium oxalate (CaC₂O₄) crystal in water channels of three kinds of bicontinuous microemulsions, consisted of P-octyl polyethylene glycol phenylether (OP)/n-amyl alcohol/cyclohexane/water and above microemulsions containing tryptophan (Trp) or aspartic acid (Asp) has been studied. The products were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The results indicated that both surfactant and amino acids all could prompt the growth of calcium oxalate monohydrate (COM) crystal, but the crystal morphology varied with the different microemulsions, pH values of the aqueous solution in channels and concentrations of the reactants. Various crystal morphologies such as butterfly-like, hollow and spiny spherical could be observed easily. A model of molecular identification – organized assembly – pervasion-combination balance was proposed to explain the formation mechanism of CaC₂O₄ crystals in the microemulsions containing Asp.     

Langmuir-Blodgett films as aligning layers for homeotropic alignment of liquid crystal molecules

The first single crystal structure of a Group VA halide salt with three equivalent long n-alkyl chains, benzyltrioctadecylammonium bromide (BzN18Br), is reported. It consists of alternating interdigitated and non-interdigitated regions of alkyl chains separated by ionic planes. Two chains per molecule are paired and extend to one side in a non-interdigitated region. The third chain is on the opposite side of the ionic plane and pairs intermolecularly to form an adjacent, interdigitated region. The thickness of two nearly extended molecules defines the bilayer unit-two ionic planes flanked by a region with intramolecularly paired chains and separated by an interdigitated chain region. Powder X-ray diffraction and optical microscopy data of liquid crystalline BzN18Br are consistent with an enantiotropic smectic A₂ (SmA₂) phase: the three n-alkyl chains of each molecule are projected from one side of an ionic plane, and head groups of neighbouring molecules are oriented head-to-head, in a non-interdigitated bilayer assembly. The structure of BzN18Br fills an important gap in our knowledge about the crystal packing of ammonium and phosphonium salts with one-four equivalent long n-alkyl chains. A comparison of their packing arrangements is made and the transitional nature of the BzN18Br structures is demonstrated. Although salts with one, two, or three long n-alkyl chains form SmA₂ phases, each is distinctive in its molecular packing. A large molecular reorganization accompanies the crystal-to-liquid crystal transition of BzN18Br.     

Langmuir-Blodgett films of polymethacrylates with side chains containing functionalized aromatic schiff's bases

Langmuir-Blodgett (LB) film formation has been investigated for polymers in which non-linear optical (NLO) moieties are attached to the side chain of a polymethacrylate (PMA) backbone. Polymer monolayers were successfully transferred onto hydrophilic glass substrates using a moving-wall type LB trough. The LB films were characterized by pressure-area isotherms, polarized ultraviolet visible spectra, ellipsometry, and second harmonic generation measurements. The characterization shows that NLO moieties in the side chain are inclined at a shallow angle to the plane of the substrate. The second-order nonlinear optical coefficient and molecular hyperpolarizability were also calculated. © 1993 John Wiley & Sons, Inc.     

两亲性芳香亚胺环钯化合物及其Langmuir-Blodgett膜的制备、表征及催化活性

合成并表征了一系列新型两亲性芳香亚胺环钯化合物.结果显示,该系列环钯催化剂可高效催化均相条件下的Heck和Suzuki偶联反应.将两亲性芳香亚胺环钯二聚体制成LB膜,其在异相条件下的催化活性是均相条件下的25倍.     

Highly Efficient Photochromism of a Crown Ether-derived Azobenzene in Langmuir-Blodgett Films

A novel crown ether-azobenzene derivative (CAD) was synthesized. It was formed in a stable monolayer at air-water interface, and could be transferred to both ITO glasses and CaF₂ substrates with near unity of transfer ratio. Under irradiations of UV and visible light,the CAD molecules showed a highly efficient photochromic behavior in the rigid Langmuir-Blodgett films.The trans-cis conversion rate reached 76%,comparable with that obtained in chloroform solution.     

Growth of GeO2 Crystallite Thin Film on Si Substrate by Langmuir-Blodgett Technique

IntroductionIn recent years,Ge and its oxide haveattracted a considerable interest for their potentialapplication in optical filterdesign[1— 6 ] .To fabricateoptical devices,sometimes it is necessary todevelop a Ge O2 thin film on the surface of othermaterial,e.g.,silica.It is well known that silicasurface is quite inert and it is pretty difficult tosynthesize thin inorganic films on it.Inorganic thinfilms on silica surface are generally prepared byphysical methods,such as ion beam reactive…     

A hydrogen peroxide biosensor based on Langmuir-Blodgett technique: Direct electron transfer of hemoglobin in octadecylamine layer

The present paper describes the modification of hemoglobin (Hb)-octadecylamine (ODA) Langmuir-Blodgett (LB) film on a gold electrode surface to develop a novel electrochemical biosensor for the detection of hydrogen peroxide. Atomic force microscopy (AFM) image of Hb-ODA LB film indicated Hb molecules existed in ODA layer in a well-ordered and compact form. The immobilized Hb displayed a couple of stable and well-defined redox peaks with an electron transfer rate constant of 4.58 ± 0.95 s⁻¹ and a formal potential of −185 mV (versus Ag/AgCl) in phosphate buffer (1.0 mM, pH 5.0) contain 0.1 M KCl at a scan rate of 200 mV s⁻¹, characteristic of Hb heme Fe(III)/Fe(II) redox couple. The formal potential of Hb heme Fe(III)/Fe(II) redox couple in ODA film shifted linearly between pH 5 and 8 with a slope of −23.8 mV pH⁻¹, suggesting that proton took part in electrochemical reaction. The ODA could accelerate the electron transfer between Hb and the electrode. This modified electrode showed an electrochemical activity to the reduction of hydrogen peroxide (H₂O₂) without the aid of any electron mediator.     

J-aggregation and its characterization in Langmuir-Blodgett films of merocyanine dyes

Langmuir-Blodgett (LB) films are constructed by successively transferring monomolecular layers formed at the air-water interface onto solid substrates. One of the advantages of the LB technique in fabricating molecular aggregates lies in the fact that it can employ various kinds of molecules by mixing them at the air-water interface. The mixed system may exhibit new properties that are not observed for individual components. This method would be useful, for example, in the studies of the formation and control of the J-aggregates of functional dyes that attract attention both in science and technology. In this paper, I review this subject mainly based on our recent results in merocyanines. LB films of merocyanine dyes, mixed with arachidic acid (C(20)), exhibit J-aggregate formation and have been serving as typical systems in revealing the physical and structural aspects of nanosized molecular aggregates constructed as monolayers. In the case of LB films of a merocyanine dye having benzothiazole as donor nucleus (abbreviated as DS), electron spin resonance (ESR) spectroscopy has been successful in determining the characteristic in-plane orientation of dye molecules with respect to the dipping direction, which led to the discovery of the flow orientation effect during the dipping process of LB films as the origin of optical dichroism often observed in LB films. In this article, after an introduction of ESR spectroscopy, three major topics on the merocyanine J-aggregation and its characterization in mixed films are discussed. The first topic is the observation and control of the size of J-aggregates in the dilution limit of dyes in arachidic acid matrix for a methyl-substituted DS (6-Me-DS). Dependence of atomic force microscopy (AFM) patterns on the molar ratio allows the identification of dye domains. J-band optical peak analysis based on the Kuhn's extended dipole model, supplemented by a novel application of femtosecond pump-probe optical spectroscopy, yields the size of the J-aggregates of 10(3). The second topic is the control of the J-band peak wavelengths by mixing two different kinds of dye molecules. The first case is the mixture of a J-forming 6-Me-DS and non-J-forming merocyanine analog, DO with benzo-oxazole instead of benzothiazole of DS. The second case is the mixture of both J-forming dyes but with different J-band peak positions, 6-Me-DS and another analog of 5-Cl-DS. The optical peak shifts depending on the molar mixing ratio will be presented. The last topic is related to the elucidation of electronic states of dye molecules in the J-aggregates. Light-induced ESR (LESR) of DS films with stable isotope ((15)N or (13)C)-substituted dyes provide clear evidence for the photoinduced charge transfer by the detection of hyperfine structures. Moreover, infrared (IR) spectroscopy of (13)C-enriched dye identifies the IR absorption peak of the relevant carbon in the chromophore. The results give evidence for the enhanced intramolecular charge transfer of dyes in the J-aggregates compared with an isolated merocyanine composed of donor and acceptor moiety. Lastly, the Cl attachment in 5-Cl-DS leads to a significant enhancement of the nitrogen hyperfine coupling in the LESR spectra. These examples and others demonstrate the potential of LB films of merocyanines in the studies of the nanosized molecular aggregates in monolayer assemblies.     

Simulation of calcium oxalate stone in vitro

Urolithiasis constitutes a serious health problem that affects a significant section of mankind. Between 3% and 14% of the population, depending on the geographical region, suffer from this illness[1]. For example, the incidence of urolithiasis in Florida in the United States of America was 15.7 in 100000 people and increased to 20.8 in 1996. Urolithiasis remains a major medical prob-lem in China, especially in Guangdong Province. A survey in 1997 in Shenzhen City, the most southern city i…     

Electrophoretic behaviour of calcium oxalate monohydrate in liquid mixtures

An experimental investigation on electrophoresis of calcium oxalate monohydrate in several liquid mixtures (methanol-, ethanol-, 2-propanol-, and methanol-acetonewater) is described.The electrophoretic transport is considered from the view-point of the Thermodynamics of Irreversible Processes. Linear relations have always been found between the mass flux and the applied electric field. The -potential of the interface C.O.M./liquid mixture has been estimated by using the classial theory of electrophoretic mobility of colloidal particles. The influence of the composition of the mixture on the electrophoretic coefficient has been discussed on the basis of the variation of -potential, viscosity and dielectric constant with the molar fraction of alcohol for binary mixtures and acetone for ternary mixtures. The concentration dependence of the electrophoretic coefficient is found to be linear only in the latter case.     

Morphological control of calcium oxalate particles in the presence of poly-(styrene-alt-maleic acid)

Calcium oxalate (CaOx) particles exhibiting different shapes and phase structures were fabricated by a simple precipitation reaction of sodium oxalate with calcium chloride in the absence and presence of poly-(styrene-alt-maleic acid) (PSMA) as a crystal modifier at room temperature. The as-obtained products were characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of reaction conditions including pH, [Ca²⁺]/[C₂O₄²⁻] ratio and concentration of PSMA and CaC₂O₄ on the crystal forms and morphologies of the as-obtained calcium oxalate were investigated. The results show that various crystal morphologies of calcium oxalate, such as parallelograms, plates, spheres, bipyramids etc. can be obtained depending on the experimental conditions. Higher polymer concentration favors formation of the metastable calcium oxalate dihydrate (COD) crystals. Lower pH is beneficial to the formation of plate-like CaOx crystals. Especially, the monodispersed parallelogram-like CaOx crystals can be produced by PSMA as an additive at pH 2. PSMA may act as a good inhibitor for urolithiasis since it induces the formation of COD and reduces the particle size of CaOx. This research may provide new insight into the morphological control of CaOx particles and the prevention of urolithiasis.     

二维琼脂凝胶体系中过渡金属离子对草酸钙晶体生长和周期性沉淀的影响

在二维凝胶圆盘体系中,研究过渡金属离子对草酸钙晶体生长和周期性环状沉淀的影响,并对其形成机理进行探讨.结果表明:在一定浓度的Fe3 存在下,体系中出现了周期性环状沉淀现象.同时发现在此条件下抑制了一水合草酸钙(COM)晶型生成.此外,加入Zn2 、Co2 、Ni2 体系中的晶体都以二水合草酸钙(COD)为主;而加Cu2 离子的圆盘中,三水合草酸钙(COT)占据了主要的成分,这说明不同的过渡金属离子对三种草酸钙晶型的生成影响不同.另外,还对出现的与尿结石有关的特殊现象(白斑和放射状的条纹)进行了探讨.