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51.
Karina A. Araus Roberto I. Canales José M. del Valle Juan C. de la Fuente 《The Journal of chemical thermodynamics》2011,43(12):1991-2001
Modification of an experimental device and methodology improved speed and reproducibility of measurement of solubility of β-carotene in pure and modified SuperCritical (SC) CO2 at (313 to 333) K. Solubilities of β-carotene in pure CO2 at (17 to 34) MPa ranged (0.17 to 1.06) μmol/mol and agreed with values reported in literature. The solubility of β-carotene in CO2 modified with (1.2 to 1.6) % mol ethanol increased by a factor of 1.7 to 3.0 as compared to its solubility in pure CO2 under equivalent conditions. The concentration of triolein in equilibrated ternary (CO2 + β-carotene + triolein) mixtures having excess triolein reached values (0.01 to 0.39) mmol/mol corresponding to its solubility in pure SC CO2 under equivalent conditions. Under these conditions, the solubility of β-carotene in triolein-modified CO2 increased by a factor of up to 4.0 in relation with its solubility in pure CO2 at comparable system temperature and pressure, reaching an uppermost value of 3.3 μmol/mol at 333 K and 32 MPa. Unlike in the case of ethanol, where enhancements in solubility where relatively independent on system conditions, solubility enhancements using triolein as co-solvent increased markedly with system pressure, being larger than using (1.2 to 1.6) % mol ethanol at about (24 to 28) MPa, depending on system temperature. The increase in the solubility β-carotene in SC CO2 as a result of using ethanol or triolein as co-solvent apparently does not depend on the increase in density associated with the dissolution of the co-solvent in CO2. Enhancements may be due to an increase in the polarizability of SC CO2, which possibly growths markedly as triolein dissolves in it when the system pressure becomes higher. 相似文献
52.
结合方差分析(ANOVA)和偏最小二乘法判别分析(PLS-DA)两种分析技术,对素食和普食人群的尿液1H NMR谱进行分析.利用ANOVA方法将数据矩阵分解为几个独立因素矩阵,滤除干扰因素后,再利用PLS-DA对单因素数据进行建模分析.实验结果表明,ANOVA/PLS-DA方法可以有效地减少饮食因素和性别因素之间的相互... 相似文献
53.
油纸复合介质中水分子扩散行为的分子动力学模拟 总被引:3,自引:0,他引:3
对不同温度下水分子在油纸复合介质中的扩散行为进行了分子动力学模拟研究. 通过分析水分子与纤维素形成的氢键发现, 油中的水分子在模拟过程中会逐渐扩散到纤维素内并与之形成氢键, 而纤维素内的水分子则与纤维素形成氢键后被束缚于纤维素中. 通过分析水分子的扩散系数发现, 由于油和纤维素的极性不同, 使得水分子在油和纤维素两种单介质中的扩散行为有较大差别, 而在复合介质中的扩散系数受水分子在油和纤维素中的比例影响较大, 两者表现出很强的相关性. 水分子和两介质的相互作用与两介质的极性也存在很大的关系, 且不同温度下水分子与两介质的相互作用能和水分子在油和纤维素中的比例也表现出了较强的相关性. 不同温度下水分子的不同分布弱化了温度对扩散系数的影响. 相似文献
54.
George Khelashvili Xiaolu Cheng Maria E. Falzone Milka Doktorova Alessio Accardi Harel Weinstein 《Journal of computational chemistry》2020,41(6):538-551
Recent discoveries about functional mechanisms of proteins in the TMEM16 family of phospholipid scramblases have illuminated the dual role of the membrane as both the substrate and a mechanistically responsive environment in the wide range of physiological processes and genetic disorders in which they are implicated. This is highlighted in the review of recent findings from our collaborative investigations of molecular mechanisms of TMEM16 scramblases that emerged from iterative functional, structural, and computational experimentation. In the context of this review, we present new MD simulations and trajectory analyses motivated by the fact that new structural information about the TMEM16 scramblases is emerging from cryo-EM determinations in lipid nanodiscs. Because the functional environment of these proteins in in vivo and in in vitro is closer to flat membranes, we studied comparatively the responses of the membrane to the TMEM16 proteins in flat membranes and nanodiscs. We find that bilayer shapes in the nanodiscs are very different from those observed in the flat membrane systems, but the function-related slanting of the membrane observed at the nhTMEM16 boundary with the protein is similar in the nanodiscs and in the flat bilayers. This changes, however, in the bilayer composed of longer-tail lipids, which is thicker near the phospholipid translocation pathway, which may reflect an enhanced tendency of the long tails to penetrate the pathway and create, as shown previously, a nonconductive environment. These findings support the correspondence between the mechanistic involvement of the lipid environment in the flat membranes, and the nanodiscs. © 2019 Wiley Periodicals, Inc. 相似文献
55.
Determining accurate dissociation constants for equilibrium processes involving a fluorescent mechanism can prove to be quite challenging. Typically, titration curves and nonlinear least squares fitting of the data using computer programs are employed to obtain such constants. However, these approaches only consider the total fluorescence signal and often ignore other energy transfer processes within the system. The current model considers the impact on fluorescence from equilibrium binding (viz., metal-ligand, ligand-substrate, etc.), quenching, and resonance energy transfer. This model should provide more accurate binding constant as well as insights into other photonic processes. The equations developed for this model are discussed and are applied to experimental data from titrimetric experiments. Since the experimental data are generally in excess of the number of parameters that are needed to define the system, fitting is operated in an overdetermined mode and employs error minimization (either absolute or relative) to define goodness of fit. Examples of how changes in certain parameters affect the shape of the titrimetric curve are also presented. The current model does not consider chelation-enhanced fluorescence. 相似文献
56.
57.
以自来水厂和污水处理厂的污泥为研究对象,采用Tessier五步法和火焰原子吸收光谱法研究污泥中重金属(Zn、Cu、Cd、Ni、Mn)含量、形态分布以及可浸出性。结果发现,在自来水厂污泥和污水处理厂污泥中重金属总量大小依次为Zn〉Mn〉Ni〉Cu〉Cd,Zn〉Mn〉Cu〉Ni〉Cd,污泥中Zn含量最高,为448.17mg.kg-1;Cd含量最低,为27.17mg.kg-1,超过国家标准,限制了污泥的农用。Tessier形态分析结果表明,污泥中Zn、Cu、Cd主要以稳定态存在;Mn主要以有效态存在,潜在的迁移性和植物毒性最值得关注;Cu浸出率最高,为14.8%,Zn浸出率最低,为0.11%,因此浸出率不仅与金属和污泥的特性有关,而且金属在污泥中赋存的化学形态对其可浸出性也有重要的影响。 相似文献
58.
59.
通过对不同产地几种中药材中砷、铅、镉、铜以及无机砷、三价砷含量的分析测定,得出样品中砷、铅、镉、铜以及无机砷、无机三价砷的测定RSD〈3%,加标回收率在91.32%—109.7%之间。11个样品的总砷含量在0.047—1.681μg/g之间,均低于2μg/g;无机砷含量为0.023—1.294μg/g;无机三价砷含量为0.019—0.918μg/g;铅含量两份样品未检出,其余样品为0.007—0.786μg/g,均低于5μg/g;镉的测定,两份样品未检出,其余样品含量为0.007—2.129μg/g,其中两份样品大于0.3μg/g;铜含量为4.441—14.07μg/g,均低于20μg/g。研究发现同种药材不同产地的重金属含量差异较大,部分产地金银花中镉含量超标严重,无机砷和三价砷含量相对较高,需引起重视。 相似文献
60.