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排序方式: 共有74条查询结果,搜索用时 156 毫秒
1.
采用分光光度法和气相色谱法研究了柿单宁对胰脂酶活性和胆固醇酯酶活性的抑制作用,以及柿单宁与胆汁酸、胆固醇的结合能力。结果表明:柿单宁对胰脂酶具有显著的抑制效果,其半数抑制浓度(half inhibitory concentration,IC50)为(0.445±0.021)mg/m L;抑制类型为非竞争性抑制,抑制常数Ki为0.406 mg/m L;柿单宁对胆固醇酯酶也具有显著的抑制作用,其半数抑制浓度IC50为(0.442±0.017)mg/m L,抑制类型为非竞争性抑制,抑制常数Ki为0.488 mg/m L。不同质量浓度的柿单宁对胆酸(cholic acid,CA)、脱氧胆酸(deoxycholic acid,DCA)都有一定的结合能力,10 mg/m L的单宁与CA、DCA的结合率分别为58%和94%;柿单宁对胆固醇胶束化溶液有较强的结合能力,0.20 mg/m L的单宁对其抑制率达到了67%。另外,在不同的p H值下,柿单宁对胆固醇都有一定的结合作用,其中p H 7.0时的结合能力明显强于p H 2.0时的结合能力。总之,柿单宁可抑制胰脂酶活性和胆固醇酯酶活性,并与胆固醇和胆汁酸结合,减少胃肠道对脂肪的吸收,这可能是柿单宁在体内发挥强降胆固醇作用的原因之一。 相似文献
2.
《国际聚合物材料杂志》2012,61(1):53-63
AbstractPhoto-cleavable polymers containing 5-hydroxy-2-nitrobenzyl alcohol (ONB) junction point between the target molecule of folic acid (FA) and the hydrophobic poly(4-substituted-?-caprolactone) (PXCLn) chain were synthesized. FA –terminated ONB-PXCLn polymers formed micelles with critical micelle concentration (CMC) 1.2 – 64.3?mg L?1. Fluorescence emission spectroscopy indicated the release of Nile red encapsulated FA-ONB-PXCLn micelles in response to irradiation. Light-triggered bursts released were observed for drug-loaded FA-ONB-PXCLn micelles. The nanoparticles exhibited nonsignificant toxicity at concentrations up to 300?µg mL?1. Flow cytometry revealed that the uptake of folate-targeted doxorubicin (DOX) -encapsulated micelles by HeLa cells was faster than that of free DOX. 相似文献
3.
Siqi Zheng Shuxian Shi Yuzheng Xia Qijiayu Wu Zhiqiang Su Xiaonong Chen 《应用聚合物科学杂志》2010,118(2):671-677
A kind of thermo‐sensitive macromonomer, styrene‐terminated poly(N‐isopropylacrylamide‐butyl acrylate) [P(NIPAm‐BA)] has been synthesized in this work. With the help of ultraviolet spectrum (UV), proton nuclear magnetic resonance (1H‐NMR), potentiometric titration and dynamic light scattering (DLS), the molecular structure, thermo‐sensitive characteristics, and micellization behaviors of this kind of macromonomer have been investigated. The obtained results demonstrate that, the molecular structure of thermo‐sensitive macromonomer, including the content of comonomer unit on the backbones and the variety of terminal groups, has great influence on its low critical solution temperature (LCST) and critical micelle concentration (CMC). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
4.
The preparation of dibasic acid-containing soy phospholipid was made by transesterification reaction with alkyl ester of diabasic acid with both lipase and alkoxide as a catalyst. The extent of incorporation of a dibasic acid varied with the molecular size of the dibasic acid. The extent of incorporation in soy phospholipids was 4–13% in the case of adipic acid and 9–20% in the case of sebacic acid. The surface-active properties of these modified soy phospholipids were examined and were found to be different from those of the original (unmodified) soy phospholipid. The interfacial properties such as critical micelle concentration (CMC), γCMC, surface excess concentration Γmax, and minimum area per molecule (Å), and thermodynamic parameters such as standard free energy of micellization, were found to depend on the hydrophobic part of the dibasic acids. 相似文献
5.
Jan Blaszczak Jolanta Zimoch Wieslaw Hreczuch Aleksander Matuszewski Jan Szymanowski 《Journal of surfactants and detergents》1999,2(1):29-37
Surface and interfacial tension isotherms for narrow-range distribution ALFOL 1214 alcohol oxyethylates were determined and
compared with those obtained for broad-range alcohol oxyethylates. Various adsorption parameters were estimated. The effectiveness
of surface tension reduction decreases when the length of polyoxyethylene hydrophile increases. Micellization is observed
at log cmc ranging from −4.7 to −3.3. Effects of the length and distribution of the polyoxyethylene chain on cmc are very
small. A minimum of A
min/N
av
0.5 is obtained for N
av=8, where A
min and N
av denote the minimum interfacial area occupied by a statistical molecule at the saturated interface and the average degree
of oxyethylation, respectively. The interface becomes saturated at pC
20=−5.61±0.35, where pC
20 denotes the logarithm of concentration required to obtain the surface pressure equal to 20 mNm−1. The highest and lowest values of the surface excess at saturation and the free energy of adsorption, respectively, are obtained
for an average degree of oxyethylation equal to 8. Parameters are correlated with the average degree of oxyethylation and
the oxyethylene chain distribution parameter according to empirical second-order polynomials. Small differences in adsorption
abilities at the water/air interface are only observed for narrow- and broad-range distributed oxyethylates. The differences
become important for adsorption at the hexadecane/water interface. The lowest values of interfacial tension are obtained for
narrow-range oxyethylates with N
av=7 and 8. The Krefeld fabric detergency tests indicated that the best detergency was observed for alcohol oxyethylates with
N
av=5–7. Narrow-range oxyethylates exhibit somewhat better washing abilities than the broad-range products. No relationship between
detergency of alcohol oxyethylates and their abilities to adsorb at the water/air and water/hydrocarbon interfaces is observed. 相似文献
6.
用I2 探针增溶分光光度方法 ,考察了Pluronic两亲嵌段共聚物P94/L6 4二元混合水溶液的胶束化行为 ,发现在溶液体相中L6 4的质量摩尔分数XL64 <0 4时 ,由于P94/L6 4混合预胶束的形成 ,导致P94分子在较高浓度时才生成单组分胶束 ;当XL64 >0 4后 ,溶液中生成了P94/L6 4混合胶束。P94和L6 4二种分子PPO嵌段长度不同 ,造成这种不同浓度比例区间内胶束组成的差异。温度升高促进了胶束化行为 相似文献
7.
A correlation for the estimation of critical micellization concentrations and temperatures of polyols in aqueous solutions 总被引:1,自引:0,他引:1
Paschalis Alexandridis Josef F. Holzwarth T. Alan Hatton 《Journal of the American Oil Chemists' Society》1995,72(7):823-826
An empirical correlation is presented for the estimation of critical micellization concentrations (CMC) and critical micellization
temperatures (CMT) for poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) copolymers in aqueous solutions. The CMC and CMT are expressed as a function of the polyol molecular
weight, composition, and temperature (for CMC determination) or concentration (in the case of CMT). The correlation was developed
from experimental CMT data for a set of 12 polyols that covered a wide range of molecular weights (2900–14600) and poly(ethylene
oxide) contents (30–80 wt%) and is based on a simple expression for the standard free energy of micellization. Such a correlation
should be useful to practitioners of the field as it allows easy prediction of CMC and CMT for a wide range of polyols with
a minimal number of input parameters. 相似文献
8.
Synthesis and evaluation of new amphiphilic polyethylene glycol-based triblock copolymer surfactants
M.?Z.?Mohamed D.?A.?Ismail A.?S.?MohamedEmail author 《Journal of surfactants and detergents》2005,8(2):175-180
We report in this investigation the synthesis of a new series of amphiphilic ABA-triblock copolymers consisting of double-chain
hydrophobic moieties (A) of different chain lengths attached to each end of polyethylene glycols of different molecular weights
(B). The identities of the prepared compounds were confirmed by elemental and Fourier transform infrared analyses. The prepared
compounds showed good water solubility. Some of their surface properties, such as the critical micelle concentration, effectiveness
of water surface tension reduction, surface excess concentration, standard free energies of adsorption and micellization,
and surface area per molecule, were determined. 相似文献
9.
ABSTRACT The paper describes the effect of time and pressure on liquid product yields when Green River shale was exposed to supercritical methanol-water at 400°C and then extracted with benzene-methanol. Reaction times between 1 second and 34 minutes were studied as were pressures between 1800 and 5200 psi. Maximum yields of liquid product were obtained after a methanol-water treatment time of about 34 minutes. Presssure did not have a significant effect on product yields. Chemical characterization of Selected liquid products is reported and shows that the product composition varies with time. Exfoliation of shale also increases with treatment time. This phenomenon is discussed and illustrated. 相似文献
10.
设计合成了3种基于五苯基苯骨架结构的苝二酰亚胺衍生物n-PDI(n 2,3,4)双子表面活性剂,利用红外光谱仪、核磁共振氢谱仪、热重分析仪,对所合成的3种目标产物结构进行表征与确认,它们的分解温度均在200℃以上。研究了3种双子表面活性剂表面活性参数和热力学参数,结果表明双子表面活性剂分子在水溶液中形成胶束和在气-液界面处的吸附过程是自发的;且双子表面活性剂分子形成胶束的过程易于进行;随温度的升高ΔGmic?、ΔHmic?、ΔSmic?均减小,表明ΔHmic?对ΔGmic?的贡献有增大趋势,ΔSmic?对ΔGmic?的贡献有下降趋势,即胶束化过程为熵驱动力在减小而焓驱动力在增大的过程。由SEM测试表明双子表面活性剂能有效吸附在锌电极表面,对其具有缓蚀作用。 相似文献