Yi Li Normal University

Yining, China

Yi Li Normal University

Yining, China

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Zhao X.-J.,Xinjiang Normal University | Zhang G.-L.,Yi Li Normal University
Chinese Journal of Polymer Science (English Edition) | Year: 2014

A theoretical investigation on the pH-induced switching of mixed polyelectrolyte brushes was performed by using a molecular theory. The results indicate that the switching properties of mixed polyelectrolyte brushes are dependent on the pH values. At low pH, negatively charged chains adopt a compact conformation on the bottom of the brush while positively charged chains are highly stretched away from the surface. At high pH values, the inverse transformation takes place. The role of pH determining the polymer chains conformation and charge behavior of mixed polyelectrolyte brushes was analyzed. It is found that there exists a mechanism for reducing strong electrostatic repulsions: stretching of the chains. The H+ and OH- units play a more important role as counterions of the charged polymers do. The collapse of the polyelectrolyte chains for different pH values could be attributed to the screening of the electrostatic interactions and the counterion-mediated attractive interaction along the chains. © 2014 Chinese Chemical Society, Institute of Chemistry, Chinese Academy of Sciences and Springer-Verlag Berlin Heidelberg.


Li K.,Chinese University of Hong Kong | Li K.,Sun Yat Sen University | Zhou X.,Chinese University of Hong Kong | Liu C.-L.,Chinese University of Hong Kong | And 6 more authors.
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences | Year: 2016

Gallocatechin gallate (GCG) possesses multiple potential biological activities. However, the content of GCG in traditional green tea is too low which limits its in-depth pharmacological research and application. In the present study, a simple, efficient and environment-friendly chromatographic separation method was developed for preparative enrichment and separation of GCG from cocoa tea (Camellia ptilophylla) which contains high content of GCG. In the first step, the adsorption properties of selected resins were evaluated, and XAD-7HP resin was chosen by its adsorption and desorption properties for GCG. In order to maximize column efficiency for GCG collection, the operating parameters (e.g., flow rate, ethanol concentration, and bed height) were optimized. We found that the best combination was the feed concentration at 20 mg/mL, flow rate at 0.75 BV/h and the ratio of diameter to bed heights as 1:12. Under these conditions, the purity of GCG was 45% with a recovery of 89%. In order to obtain pure target, a second step was established using column chromatography with sephadex LH-20 gel and 55% ethanol-water solution as eluent. After this step, the purity of the GCG was 91% with a recovery of 68% finally. © 2015 Elsevier B.V.


PubMed | Chinese University of Hong Kong, Yi Li Normal University and Sun Yat Sen University
Type: | Journal: Journal of chromatography. B, Analytical technologies in the biomedical and life sciences | Year: 2016

Gallocatechin gallate (GCG) possesses multiple potential biological activities. However, the content of GCG in traditional green tea is too low which limits its in-depth pharmacological research and application. In the present study, a simple, efficient and environment-friendly chromatographic separation method was developed for preparative enrichment and separation of GCG from cocoa tea (Camellia ptilophylla) which contains high content of GCG. In the first step, the adsorption properties of selected resins were evaluated, and XAD-7HP resin was chosen by its adsorption and desorption properties for GCG. In order to maximize column efficiency for GCG collection, the operating parameters (e.g., flow rate, ethanol concentration, and bed height) were optimized. We found that the best combination was the feed concentration at 20mg/mL, flow rate at 0.75 BV/h and the ratio of diameter to bed heights as 1:12. Under these conditions, the purity of GCG was 45% with a recovery of 89%. In order to obtain pure target, a second step was established using column chromatography with sephadex LH-20 gel and 55% ethanol-water solution as eluent. After this step, the purity of the GCG was 91% with a recovery of 68% finally.


Zhu T.,Nanjing University | Jiang Z.,Nanjing University | Jiang Z.,Yi Li Normal University | Ma Y.,Nanjing University | Ma Y.,Soochow University of China
Applied Physics Letters | Year: 2013

Particle adsorption on lipid membrane is critical to biomedical applications. Gravity effect on the process has long been ignored. A combination of the upright and inverted configuration measurements was developed to exhibit that gravity causes a particle adsorption disparity on membrane between the different heights of medium. The more homogeneous adsorption tendency of nanoparticle aggregate compared to nanoparticle under the same gravitational motive force is attributed to the larger hydrodynamic diameter induced lower concentration disparity. © 2013 AIP Publishing LLC.


Zhu T.,Nanjing University | Jiang Z.,Nanjing University | Jiang Z.,Yi Li Normal University | Nurlybaeva E.M.R.,Kazakh National Technical University | And 3 more authors.
Langmuir | Year: 2013

There is currently a lack of comprehensive understanding of osmotic effect on lipid vesicle fusion on solid oxide surface. The question has both biological and biomedical implications. We studied the effect by quartz crystal microbalance with dissipation monitoring using NaCl, sucrose as osmolytes, and two different osmotic stress imposition methods, which allowed us to separate the osmotic effects from the solute impacts. Osmotic stress was found to have limited influence on the fusion kinetics, independently of the direction of the gradient. Further atomic force microscopy experiments and energy consideration implied that osmotic stress spends the majority of chemical potential energy associated in directed transport of water across membrane. Its contribution to vesicle deformation and fusion on substrate is therefore small compared to that of adhesion. © 2013 American Chemical Society.


Fang J.,Nanjing University | Ren C.,Nanjing University | Zhu T.,Nanjing University | Wang K.,Nanjing University | And 4 more authors.
Analyst | Year: 2015

A molecular level understanding of the phenomena taking place at solid-liquid interfaces, ranging from changes in mass to conformation changes, is the key to developing and improving many chemical and biological systems and their scientific and medical applications. Surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) techniques are often coupled to achieve this understanding. We divided various experimentally relevant scenarios into the following six categories: boundary solutions; surface modifications; conformation; viscoelastic properties; molecular ruler; and mass sensitivity. For each case, based on theoretical analyses, we discuss the following four points with respect to discrete adsorbates at solid-liquid interfaces: (1) the different types of information that can be obtained, why it can be obtained and how to obtain it; (2) the origins of many current approaches and why they are imperfect; (3) guidelines for experimental design; and (4) possible studies, such as the effect of dimensional confinement and adsorption forces on the ability of conformational changes to occur on the receipt of external stimuli and the hysteresis in these changes. This journal is © The Royal Society of Chemistry 2015.


Zhu T.,Nanjing University | Jiang Z.,Nanjing University | Jiang Z.,Yi Li Normal University | Ma Y.,Nanjing University | Ma Y.,Soochow University of China
Colloids and Surfaces B: Biointerfaces | Year: 2012

Intermembrane lipid exchange is critical to membrane functions and pharmaceutical applications. The exchange process is not fully understood and it is explored by quartz crystal microbalance with dissipation monitor method in this research. It is found that intermembrane lipid exchange is accelerated with the decrease of vesicle size and the increase of charge and liquid crystalline lipid composition ratio. Vesicle adsorption rate, membrane lateral pressure gradient, and lipid lateral diffusion coefficient are inferred to be critical in deciding the lipid exchange kinetics between membranes. Besides that, the membrane contact situation during lipid exchange is also studied. The maximum total membrane contact area is found to increase with the decrease of vesicle size, charged and liquid crystalline lipid composition ratio. A competition mechanism between the vesicle adsorption rate and the intermembrane lipid exchange rate was proposed to control the maximum total membrane contact area. © 2012 Elsevier B.V.


Zhu T.,Nanjing University | Jiang Z.,Yi Li Normal University | Jiang Z.,Nanjing University | Ma Y.,Nanjing University | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2016

Preservation of structural integrity under various environmental conditions is one major concern in the development of the supported lipid membrane (SLM)-based devices. It is common for SLMs to experience temperature shifts from manufacture, processing, storage, and transport to operation. In this work, we studied the thermal adaption of the supported membranes on silica substrates. Homogenous SLMs with little defects were formed through the vesicle fusion method. The mass and fluidity of the bilayers were found to deteriorate from a heating process but not a cooling process. Fluorescence characterizations showed that the membranes initially budded as a result of heating-induced lipid lateral area expansion, followed by the possible fates including maintenance, retraction, and fission, among which the last contributes to the irreversible compromise of the SLM integrity and spontaneous release of the interlipid stress accumulated. Based on the mechanism, we developed a strategy to protect SLMs from thermal disruption by increasing the solute concentration in medium. An improved preservation of the membrane mass and fluidity against the heating process was observed, accompanied by a decrease in the retraction and fission of the buds. Theoretical analysis revealed a high osmotic energy penalty for the fission, which accounts for the depressed disruption. This osmotic-based protection strategy is facile, solute nonspecific, and long-term efficient and has little impact on the original SLM properties. The results may help broaden SLM applications and sustain the robustness of SLM-based devices under multiple thermal conditions. © 2016 American Chemical Society.


PubMed | Yi Li Normal University and Nanjing University
Type: Journal Article | Journal: ACS applied materials & interfaces | Year: 2016

Preservation of structural integrity under various environmental conditions is one major concern in the development of the supported lipid membrane (SLM)-based devices. It is common for SLMs to experience temperature shifts from manufacture, processing, storage, and transport to operation. In this work, we studied the thermal adaption of the supported membranes on silica substrates. Homogenous SLMs with little defects were formed through the vesicle fusion method. The mass and fluidity of the bilayers were found to deteriorate from a heating process but not a cooling process. Fluorescence characterizations showed that the membranes initially budded as a result of heating-induced lipid lateral area expansion, followed by the possible fates including maintenance, retraction, and fission, among which the last contributes to the irreversible compromise of the SLM integrity and spontaneous release of the interlipid stress accumulated. Based on the mechanism, we developed a strategy to protect SLMs from thermal disruption by increasing the solute concentration in medium. An improved preservation of the membrane mass and fluidity against the heating process was observed, accompanied by a decrease in the retraction and fission of the buds. Theoretical analysis revealed a high osmotic energy penalty for the fission, which accounts for the depressed disruption. This osmotic-based protection strategy is facile, solute nonspecific, and long-term efficient and has little impact on the original SLM properties. The results may help broaden SLM applications and sustain the robustness of SLM-based devices under multiple thermal conditions.


Zhang Y.,Yi Li Normal University | Li Z.-W.,Yi Li Normal University | He X.-Y.,Yi Li Normal University | Wang X.-L.,Yi Li Normal University
Xiandai Huagong/Modern Chemical Industry | Year: 2015

The CdS: Mn quantum dots are synthesized by using solvothermal method in oleylamine at 160℃ for 12 hours. The as-prepared CdS: Mn quantum dots are investigated by X-ray diffraction, Fourier transform infrared spectroscopy and fluorescence spectroscopy. The results show that the JCPDS# of CdS: Mn quantum dots is 80-0019. The carboxyl group (-COOH) is successfully introduced onto the surface of CdS: Mn quantum dots. The main peak of modified CdS: Mn quantum dots is blueshifted from 526 nm to 488 nm. It is found that DNA can quench the luminescence of the particles effectively. And there is a quantitative relation of luminescence quenching with the amount of nucleic acids. Under pH=6.6, the fluorescence intensity of functionalized material (-COOH/CdS: Mn) is proportional to the concentration over the range of 0.30-0.90 mg/L for herring sperm DNA (hs-DNA). The linear regression equation is ΔF =78.69-0.179 c. The corresponding detection limit, R and RSD are 0.053 mg/L, 0.998 8 and 0.27%, respectively. ©, 2015, Xiandai Huagong/Modern Chemical Industry. All right reserved.

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