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91.
Lee Kun Jong Kim Mee Ree Kim Yun-Bae Myung Pyung-Keun Sok Dai-Eun 《Neurochemical research》1997,22(12):1471-1476
The effect of divalent metal ions on the activity of glycerophosphocholine cholinephosphodiesterse from ox brain was examined. Zn2+- and Co2+-glycerophosphocholine cholinephosphodiesterases were prepared from the exposure of apoenzyme to Zn2+ and Co2+, respectively, and the properties of two metallo-phosphodiesterases were compared to those of native phosphodiesterase. Although two metallo-enzymes were similar in expressing Km value, optimum pH or sensitivity to Cu2+, they differed in the susceptibility to the inhibition by thiocholine or tellurite; while Co2+-phosphodiesterase was more sensitive to tellurites, Zn2+-phosphodiesterase was more susceptible to inhibition by thiocholine. In addition, Zn2+-phosphodiesterase was more thermo-stable than Co2+ enzyme. Separately, when properties of native phosphodiesterase were compared to those of each metallo-phosphodiesterase, native phosphodiesterase was found to be quite similar to Zn2+-phosphodiesterase in many respects. Even in thermo-stability, native enzyme resembled Zn2+-phosphodiesterase rather than Co2+-enzyme. Consistent with this, the stability of native phosphodiesterase was maintained in the presence of Zn2+, but not Co2+. Mn2+ was also as effective as Zn2+ in the stabilization of the enzyme. Noteworthy, the native enzyme was found to be inhibited competitively by Cu2+ with a Ki value of 20 M, and its inhibitory action was antagonized effectively by Zn2+ or Co2+. Also, choline, another competitive inhibitor of the enzyme, appeared to antagonize the inhibitory action of Cu2+. Taken together, it is suggested that there may be multiple binding sites for divalent metal ions in the molecule of glycerophosphocholine cholinephosphodiesterase. 相似文献
92.
Anja von Nahmen Andreas Post Hans-Joachim Galla M. Sieber 《European biophysics journal : EBJ》1997,26(5):359-369
Three compounds of the pulmonary surfactant – dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG),
and the surfactant associated protein C (SP-C) – were spread at the air-water interface of a Langmuir trough as a model system
to mimic the properties of natural surfactant. Fluorescence microscopical images of the film formed at the interface were
obtained during compression using a fluorescence dye bound covalently either to phosphatidylcholine or to SP-C. The images
were quantified using statistical methods in respect to relative areas and relative fluorescence intensities of the domains
found. In the early stage of compression, film pressure rose slightly and was accompanied by a phase separation which could
be recognized in the images by the formation of bright and dark domains. On further compression, after a steep increase of
film pressure, a plateau region of constant film pressure started abruptly. During compression in the plateau region, fluorescence
intensity of the bright domain formed in the early stage of compression increased. The increasing fluorescence intensity,
the non-Gaussian intensity distribution of the bright domain, and the small mean molecular area of the film in the plateau
region gave rise to the assumption that multilayer structures were formed in the late stage of compression. The formation
of the multilayer structures was fully reversible in repeated compression-expansion cycles including the plateau region of
the phase diagram. The ability of lipid/SP-C mixtures to form reversible multilayer structures during compression may be relevant
to stability in lungs during expiration and inhalation.
Received: 13 February 1997 / Accepted: 22 May 1997 相似文献
93.
The interaction between surfactant and fluorescein was studied, using a fluorescence spectroscopy and flow-injection (FI) chemiluminescence (CL) method. It was found that the cationic surfactant cetyltrimethylammonium bromide (CTAB) could cause the structural transformation of fluorescein from the quinone to the spirolactone form, and greatly enhance the CL intensity of the fluorescein-human serum albumin (HSA) complex. Based on this finding, a rapid and sensitive FI-CL method was developed for the determination of HSA. Under the optimum conditions, the proposed method has a linear range of 0.05-24.0 microg/mL, with a detection limit of 0.03 microg/mL for HSA (3sigma). The relative standard deviation (RSD) of 1.2 microg/mL HSA (n = 8) is 0.8%. The method was applied to the determination of protein content in urine samples, with satisfactory results. Density functional theory was used to study the mechanism of surfactant-enhanced CL intensity of the fluorescein-HSA complex. 相似文献
94.
Effect of surfactant protein A on the physical properties and surface activity of KL4-surfactant 下载免费PDF全文
Sáenz A Cañadas O Bagatolli LA Sánchez-Barbero F Johnson ME Casals C 《Biophysical journal》2007,92(2):482-492
SP-A, the major protein component of pulmonary surfactant, is absent in exogenous surfactants currently used in clinical practice. However, it is thought that therapeutic properties of natural surfactants improve after enrichment with SP-A. The objective of this study was to determine SP-A effects on physical properties and surface activity of a new synthetic lung surfactant based on a cationic and hydrophobic 21-residue peptide KLLLLKLLLLKLLLLKLLLLK, KL(4). We have analyzed the interaction of SP-A with liposomes consisting of DPPC/POPG/PA (28:9:5.6, w/w/w) with and without 0.57 mol % KL(4) peptide. We found that SP-A had a concentration-dependent effect on the surface activity of KL(4)-DPPC/POPG/PA membranes but not on that of an animal-derived LES. The surface activity of KL(4)-surfactant significantly improved after enrichment with 2.5-5 wt % SP-A. However, it worsened at SP-A concentrations > or =10 wt %. This was due to the fluidizing effect of supraphysiological SP-A concentrations on KL(4)-DPPC/POPG/PA membranes as determined by fluorescence anisotropy measurements, calorimetric studies, and confocal fluorescence microscopy of GUVs. High SP-A concentrations caused disappearance of the solid/fluid phase coexistence of KL(4)-surfactant, suggesting that phase coexistence might be important for the surface adsorption process. 相似文献
95.
The structure transition of λ-DNA induced by cationic surfactant cellar media was investigated by using CD, SEM and AFM. The experimental data of CD revealed that λ-DNA can be induced from B-form to a collapsed structure with the addition of the cationic surfactant CTAB to the system. The condensed process of λ-DNA from coil state to small globular state (diameter about 1.25 μm) and finally big globular state (diameter about 5.4 μm) was observed by using SEM and AFM. 相似文献
96.
与GA3单独处理相比,GA3与表面活性剂粤辅3号(YF3)混合使用,可降低GA3的表面张力及其受雨水冲刷程度,部分地溶解叶表面的硅质、蜡质和角质,使秧苗对GA3的吸附量增加3~5倍,吸收量加1~3倍;增加水稻幼苗的株高67%。 相似文献
97.
Maria Carafa Giuseppe Lucania Emilia Marchei Vincenza Dolo Maria Giammatteo Maria Rosaria Torrisi Eleanora Santucci Antonio Pavan 《Biotechnic & histochemistry》1999,74(2):77-84
We analyzed the binding and fusogenic properties of surfactant vesicles (SVs), composed of ionic and nonionic surfactants and cholesterol, with the surface of different human lymphoid cells. The influence of charge on SVs-cell interaction was evaluated by monitoring the presence of fluorescent sodium calcein artificially entrapped in the vesicles using optical fluorescence microscopy and laser scanning confocal microscopy. Our results clearly indicate that only negatively charged vesicles bind and fuse with the plasma membrane of human lymphoid cells, and the number of SVs bound to the cell surface was variable among the positive cells. Thin section electron microscopy illustrated that the fusogenic events of SVs with the cell plasma membrane mostly occurred at smooth and nonvillous regions of the cell surface. Taken together, our results suggest that binding and fusion of SVs with the cell plasma membrane might be dependent on interactions with specific membrane components that preferentially recognize negatively charged SVs. 相似文献
98.
Mohamad Osman Harald Hiland Holm Holmsen Yutaka Ishigami 《Journal of peptide science》1998,4(7):449-458
We have studied the effects of extrinsic environmental conditions on the conformation of surfactin, a heptapeptide biosurfactant from Bacillus subtilis, in aqueous solutions. It has been made clear that temperature, pH, Ca2+ ions and the synthetic nonionic surfactant hepta-ethylene glycol (C12E7) affect the conformation of surfactin in aqueous solutions. The β-sheet formation reached a maximum at 40°C both in presence and absence of (C12E7) and the nonionic surfactant enhances the β-sheet formation even at 25°C. Ca2+ induced the formation of a-helices and caused this transition at 0.3 mm with surfactin monomers or at 0.5 mm with surfactin micelles, but above these transition concentrations of Ca2+ β-sheets were observed. In micellar solution the β-sheet structure was stabilized at pH values below 7 or upon addition of Ca2+ in concentrations above 0.5 mm . Our results indicated that the bioactive conformation of surfactin is most likely the β-sheets when the molecules are assembled in micelles. The β-sheet structure in micelles could be retained by tuning the micelles. Surfactin micelles could be tuned in the bioactive conformation by manipulating pH, temperature, Ca2+ or (C12E7) concentrations in surfactin solutions. Our results strongly indicated that Ca2+ and other molecules (such as C12E7) may function as directing templates in the assembly and conformation of surfactin in micelles. Thus, we suggest environmental manipulation and template-aided micellation (TAM) as a new approach for preparing predesigned micelles, microemulsions or micro-spheres for specific application purposes. © 1998 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
99.
Xinxin Cao Anqiang Pan Sainan Liu Jiang Zhou Site Li Guozhong Cao Jun Liu Shuquan Liang 《Liver Transplantation》2017,7(20)
Sodium (Na) super ion conductor structured Na3V2(PO4)3 (NVP) is extensively explored as cathode material for sodium‐ion batteries (SIBs) due to its large interstitial channels for Na+ migration. The synthesis of 3D graphene‐like structure coated on NVP nanoflakes arrays via a one‐pot, solid‐state reaction in molten hydrocarbon is reported. The NVP nanoflakes are uniformly coated by the in situ generated 3D graphene‐like layers with the thickness of 3 nm. As a cathode material, graphene covered NVP nanoflakes exhibit excellent electrochemical performances, including close to theoretical reversible capacity (115.2 mA h g?1 at 1 C), superior rate capability (75.9 mA h g?1 at 200 C), and excellent cyclic stability (62.5% of capacity retention over 30000 cycles at 50 C). Furthermore, the 3D graphene‐like cages after removing NVP also serve as a good anode material and deliver a specific capacity of 242.5 mA h g?1 at 0.1 A g?1. The full SIB using these two cathode and anode materials delivers a high specific capacity (109.2 mA h g?1 at 0.1 A g?1) and good cycling stability (77.1% capacity retention over 200 cycles at 0.1 A g?1). 相似文献
100.
Charles Smith Zongyi Li Robert Holman Fang Pan Richard A. Campbell Mario Campana 《MABS-AUSTIN》2017,9(3):466-475
Surface and interfacial adsorption of antibody molecules could cause structural unfolding and desorbed molecules could trigger solution aggregation, resulting in the compromise of physical stability. Although antibody adsorption is important and its relevance to many mechanistic processes has been proposed, few techniques can offer direct structural information about antibody adsorption under different conditions. The main aim of this study was to demonstrate the power of neutron reflection to unravel the amount and structural conformation of the adsorbed antibody layers at the air/water interface with and without surfactant, using a monoclonal antibody ‘COE-3′ as the model. By selecting isotopic contrasts from different ratios of H2O and D2O, the adsorbed amount, thickness and extent of the immersion of the antibody layer could be determined unambiguously. Upon mixing with the commonly-used non-ionic surfactant Polysorbate 80 (Tween 80), the surfactant in the mixed layer could be distinguished from antibody by using both hydrogenated and deuterated surfactants. Neutron reflection measurements from the co-adsorbed layers in null reflecting water revealed that, although the surfactant started to remove antibody from the surface at 1/100 critical micelle concentration (CMC) of the surfactant, complete removal was not achieved until above 1/10 CMC. The neutron study also revealed that antibody molecules retained their globular structure when either adsorbed by themselves or co-adsorbed with the surfactant under the conditions studied. 相似文献