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81.
The effect of Cibacron Blue 3GA (CB) on the fluorescence emission spectra of bovine serum albumin (BSA) was investigated in
cationic reversed micelles formed with cetyltrimethylammonium bromide (CTAB) compared with that in aqueous phase. The anionic
CB had electrostatic interactions with cationic CTAB and affinity interactions with BSA in the reversed micelles. The addition
of CB in the reversed micellar phase led to a great decrease in the fluorescence intensity of BSA and a remarkable red shift
of the wavelength of emission maximum (λmax). The fluorescence intensity of BSA decreased and the λmax decreased 5 nm (blue shift) without the addition of CB in the reversed micellar phase. The fluorescence intensity of BSA
with the addition of CB had the strongest value in the aqueous phase with the presence of CTAB, a less strong value in the
reversed micellar phase, and a weak value in the aqueous phase without the presence of CTAB. The increase in λmax of BSA with the addition of CB in the reversed micellar phase might indicate the decrease in the hydrophobic microenvironment
of the Trp residue of BSA, contrary to those microenvironments in the absence of CB. 相似文献
82.
顶空固相微萃取-气质联用分析小麦储藏过程中挥发性成分变化 总被引:16,自引:0,他引:16
采用顶空固相微萃取(HS-SPME)和气相色谱-质谱联用(GC-MS)对不同储藏时间弱(强)筋小麦中的挥发性物质进行提取、鉴定与分析.选用复合萃取纤维二乙烯基苯-炭烯-聚二甲硅氧烷共聚物(DVB/CAR/PDMS)50 μm涂层,对萃取温度、时间、样品用量和解析时间进行优化.结果表明: HS-SPME测定挥发性物质的最佳前处理条件样品量20 g, 萃取温度75 ℃, 萃取时间60 min, 260 ℃条件下解析5 min;经鉴定分析小麦挥发性成分主要有烃类、醛类,其次为醇类、酮类;挥发性成分总含量在储藏6个月内均呈现先降后增的趋势.弱筋小麦的烃类挥发物相对量随储藏时间延长而快速增加,醛类相对含量先降后升,而酮类和醇类相对含量则逐渐下降;强筋小麦中除烃类相对含量呈先下降而后快速增加外,其余各类挥发物含量均与弱筋小麦呈现相同的规律.储藏6个月后,变化较明显的挥发性物质有己醇、己醛、2,6,10-三甲基-十二烷、十五烷和二十烷. 相似文献
83.
84.
Huan-Quan Sun Lei Zhang Zhen-Quan Li Xin-Wang Song Xu-Long Cao Lu Zhang Sui Zhao Jia-Yong Yu 《Colloid and polymer science》2012,290(1):31-40
The dynamic dilational properties of sodium 2-(2-(alkylaryloxy)-alkylamido)ethanesulfonates (12+nB-Ts) at the air–water interfaces
were investigated by drop shape analysis, and their foam properties were also measured. The influences of time and bulk concentration
on surface dilational properties were expounded. The results show that the molecular interaction controls the nature of adsorption
film during lower concentration range, and the film behaves elastic in nature. During higher concentration range, the diffusion
exchange process controls the dynamic dilational properties and the surface film shows remarkable viscoelasticity. An increase
in hydrophobic chain length enhances the molecular interaction at low concentration and speeds up the diffusion exchange process
at high concentration, which results in the different variations of modulus at different concentration regions. For 12+nB-Ts,
too short a chain probably produces bad film elasticity, whereas too great a length produces too fast liquid drainage. Therefore
the optimal length in the branched chain leads to the best foam stability. 相似文献
85.
以尿素、四水合氯化锰和氧化石墨烯为原料,采用水热法并通过热分解制备了一种具有石墨烯包覆结构的石墨烯-二氧化锰复合材料,利用扫描电子显微镜、X射线衍射、比表面积(BET)、拉曼光谱和热失重等技术对其形貌、晶体结构及表面结构进行了表征;在三电极条件下利用循环伏安法、恒流充放电法和交流阻抗法测试了材料的电化学性能,并考察了不同石墨烯含量对材料比电容的影响.结果表明,在不添加模板剂的条件下制备的复合材料中二氧化锰是具有介孔结构的α-MnO2,当复合15%(质量分数)的石墨烯后材料的比表面积从109 m2·g-1提高到168 m2·g-1.复合材料具有更好的电化学性能,在0.2 A·g-1电流密度下复合材料的比电容达到最大值(454 F·g-1),远高于纯二氧化锰的值(294 F·g-1).在2 A·g-1的电流密度下恒流充放电2000次后复合材料的比电容保持率为92%. 相似文献
86.
87.
Jia-Yong Wu 《Journal of Mathematical Analysis and Applications》2010,369(1):400-407
Let (M,g) be a complete noncompact Riemannian manifold with the m-dimensional Bakry-Émery Ricci curvature bounded below. In this paper, we give a local Li-Yau type gradient estimate for the positive solutions to a general nonlinear parabolic equation
ut=Δu−∇?⋅∇u−aulogu−qu 相似文献
88.
Jia-Yong Wu 《Results in Mathematics》2010,57(3-4):377-386
In this note we generalize the Huisken’s (J Diff Geom 21:47–62, 1985) result to Riemannian orbifolds. We show that on any n-dimensional (n ≥ 4) orbifold of positive scalar curvature the metric can be deformed into a metric of constant positive curvature, provided the norm of the Weyl conformal curvature tensor and the norm of the traceless Ricci tensor are not large compared to the scalar curvature at each point, and therefore generalize 3-orbifolds result proved by Hamilton [Three- orbifolds with positive Ricci curvature. In: Cao HD, Chow B, Chu SC, Yau ST (eds) Collected Papers on Ricci Flow, Internat. Press, Somerville, 2003] to n-orbifolds (n ≥ 4). 相似文献
89.
The recovery of α-amylase from the crude enzyme preparation by the reversed micellar liquid-liquid extraction was investigated.
The reversed micellar solution was formed by dissolving a cationic surfactant Aliquat 336 in six different alkanes (cyclohexane,
n-hexane, isooctane, n-octane, n-decane, and n-dodecane) respectively with addition of a cosolvent n-octanol. It was found
that a minimal quantity of noctanol was needed for Aliquat 336 to dissolve in apolar solvent and form reversed micelles. Furthermore,
this minimal amount of n-octanol needed was found to be different when Aliquat 336 was dissolved in different alkanes. It
tended to increase with the number of carbon atoms in alkane and also depended on the solvent structure. During the forward
extraction process, it was revealed that a high value of solubilization of protein in Aliquat 336 reversed micelles could
be achieved when four out of the six alkanes (cyclohexane, n-hexane, isooctane, noctane) were used as the solvent for Aliquat
336. After a full forward and backward extraction cycle, however, a high recovery of both the protein mass and a-amylase activity
in the stripping solution could be obtained only when two out of the six alkanes (n-hexane and isooctane) were used as the
solvent for Aliquat 336. When n-hexane and isooctane were used as the solvent for Aliquat 336, up to 80% of the total α-amylase
activity in the crude enzyme preparation could be recovered at the end of extraction cycle, meanwhile α-amylase could be concentrated
about 1.4-fold. In the cases of other four alkanes (cyclohexane, n-octane, n-decane, and n-dodecane) as solvent, most of the
α-amylase activity in the crude enzyme preparation would be denatured after an extraction cycle. 相似文献
90.