The solvatochromic fluorescent probe 8-anilino-1-naphthalenesulfonate (ANS) has been used to study the hydrophobicity and conformational dynamics of lecithin:cholesterol acyltransferase (LCAT). The ANS to LCAT binding constant was estimated from titrations with ANS, keeping a constant concentration of LCAT (2 microM). Apparent binding constant was found to be dependent on the excitation. For the direct excitation of ANS at 375 nm the binding constant was 4.7 microM(-1) and for UV excitation at 295 nm was 3.2 microM(-1). In the later case, not only ANS but also tryptophan (Trp) residues of LCAT is being excited. Fluorescence spectra and intensity decays show an efficient energy transfer from tryptophan residues to ANS. The apparent distance from Trp donor to ANS acceptor, estimated from the changes in donor lifetime was about 3 nm and depends on the ANS concentration. Steady-state and time-resolved fluorescence emission and anisotropies have been characterized. The lifetime of ANS bound to LCAT was above 16 ns which is characteristic for it being in a hydrophobic environment. The ANS labeled LCAT fluorescence anisotropy decay revealed the correlation time of 42 ns with a weak residual motion of 2.8 ns. These characteristics of ANS labeled LCAT fluorescence show that ANS is an excellent probe to study conformational changes of LCAT protein and its interactions with other macromolecules. 相似文献
Three types of multiple emulsions were prepared with lecithin. The morphology, stability, and rheological properties of the three types of W/O/W multiple emulsions were evaluated. The formulation factors, including salts and aliphatic alcohol, were further examined. The three types of multiple emulsions were formed by different emulsifiers. An excellent multiple emulsion occurred with 2?wt% lecithin concentration, stabilized by 0.05?wt% NaCl. All multiple emulsions showed shear-thinning behavior, i.e., the apparent viscosity decreased with the increase of the shear rate. With the high concentration of lecithin, the multiple emulsions exhibited the highest viscosity at low shear rate and had higher storage modulus (G′) and the loss modulus (G″). This study was conducted to reveal that different types of multiple emulsions can be formed with lecithin, and that the stability and rheological properties were different with different types of multiple emulsions. 相似文献
Abstract A rapid, sensitive and reproducible chronoarnperometric method for the determination of lecithin is described. The method is based on the inhibition of the oxygen reduction process by the adsorption of lecithin at the mercury -solution interface. Current-time curves recorded during the growth of single mercury drops at ?0.200 V (vs SCE) in aqueous-ethanolic solutions of lecithin are employed. The adsorption effect may be evaluated by measuring the time necessary for a complete drop surface coverage, “to”, interpolating the descending branch of the i-t curves linearly to zero current. The influence of the variables that affect the inhibition process is studied and a linear relationship between t1/2o and lecithin concentration in the 20–80 μg/ml range is found. The relative standard deviation of the proposed method is 1.3%. 相似文献
Abstract A new type of acetylcholine sensor was made with an Ion Sensitive Field Effect Transistor (ISFET) and acetylcholine receptor. The acetylcholine receptor was fixed on a polyvinylbutyral membrane which covered the ISFET gate. When acetylcholine was injected into this system, the differential gate output voltage gradually Shifted to the positive side and reached a constant value. This response was due to the positive charge of acetylcholine. A linear relationship was obtained between the initial rate of the differential gate output voltage change and the logarithmic value of the acetylcholine concentration. Acetylcholine was fixed in the range 0.1-10μM. When the acetylcholine receptor was immobilized with the lipid membrane, the response was amplified with both the positive charge of acetylcholine and sodium ion flux through the acetylcholine receptor's channel. Therefore, the difference in the differential voltage between the acetylcholine receptor-ISFET systems with and without the lipid membrane was caused by sodium ion flux through the acetylcholine receptor's channel. 相似文献
Abstract A new procedure for the determination of lecithin and sphingomyelin in amniotic fluid is described. rapid column chromatography in the sample preparation steps with computer-assisted infrared spectroscopy in the final determination. Lipids are extracted from amniotic fluid with a chloroform/methanol solvent. The organic layer is separated and evaporated to dryness. The residue is The new method couples the use of simple, redissolved i n chloroforn and Fassed through a hydroxyapatite column to remove interfering constituents. The complete isolation cflecithin and sphingomyelin fror other li Fidsis confimec by both infrared spectroscopy and thin layer chronatcgrayhy. 相似文献
Red fluorescent organic nanoparticles (FONs) based on a cyano-substituted diarylethylene and tetraphenylethene derivative conjugated molecule (R-TPE) were facilely prepared via surfactant modification with lecithin for the first time. The obtained R-TPE-LEC FONs were characterized by a series of techniques including fluorescence and UV spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Biocompatibility evaluation and cell uptake behavior of R-TPE-LEC FONs were further investigated to explore their potential biomedical application. We demonstrated that such red FONs exhibit anti-aggregation-caused quenching property, broad excitation wavelength, high water dispersibility, uniform morphology (40–60 nm), and excellent biocompatibility, making them promising for cell imaging application. 相似文献
In the present study, the heat-induced interaction between whey proteins and casein micelles was studied. To that end, the particle size distribution of 5.5% (w/w) casein micellar dispersions was determined by photon correlation spectroscopy as a function of both the whey protein concentration and heating time at 80 °C. The results clearly indicated that heat-induced aggregation of the casein micelles only occurred in the presence of whey proteins.
In an effort to overcome the heat-induced interactions between whey proteins and casein micelles, the influence of different soybean lecithins was investigated. Comparing native to hydrolysed, as well as hydroxylated soybean lecithin, it was observed that the heat-stabilising effect of the lecithins was directly related to their hydrophilicity: whereas native soybean lecithin had hardly any beneficial effect, highly hydrolysed as well as hydroxylated soybean lecithin largely prevented heat-induced casein micelle aggregation in the presence of whey proteins.
From experimental observations on the heat-induced decrease of whey protein solubility both in the absence and presence of hydrolysed lecithin, it was deduced that the latter may stabilise the exposed hydrophobic surface sites of heat-denatured whey proteins. Dynamic surface tension measurements indicated that the heat-stabilising properties of lecithins were mainly determined by their critical aggregation concentration. 相似文献