Novel hybrid vesicles co-assembled from a cationic lipid and PAAc-g-mPEG with pH-triggered transmembrane channels for controlled drug release

This work presents an important example of novel hybrid vesicles with pH-triggered transmembrane channels prepared by co-assembly of poly(acrylic acid)-g-poly(monomethoxy ethylene glycol) (PAAc-g-mPEG) with a cationic lipid, didodecyldimethylammonium bromide (DDAB), via electrostatic interaction for effective doxorubicin (DOX) release

Classification and nondegeneracy of SU(n+1)SU(n+1) Toda system with singular sources

We consider the following Toda system \Delta u_i + \D \sum_{j = 1}^n a_{ij}e^{u_j} = 4\pi\gamma_{i}\delta_{0} \text{in}\mathbb R^2, \int_{\mathbb R^2}e^{u_i} dx -1$,$\delta_0$is Dirac measure at 0, and the coefficients$a_{ij}$form the standard tri-diagonal Cartan matrix. In this paper, (i) we completely classify the solutions and obtain the quantization result:$$\sum_{j=1}^n a_{ij}\int_{\R^2}e^{u_j} dx = 4\pi (2+\gamma_i+\gamma_{n+1-i}), \;\;\forall\; 1\leq i \leq n.$$This generalizes the classification result by Jost and Wang for$\gamma_i=0$,$\forall \;1\leq i\leq n$. (ii) We prove that if$\gamma_i+\gamma_{i+1}+...+\gamma_j \notin \mathbb Z$for all$1\leq i\leq j\leq n$, then any solution$u_i$ is \textit{radially symmetric} w.r.t. 0. (iii) We prove that the linearized equation at any solution is \textit{non-degenerate}. These are fundamental results in order to understand the bubbling behavior of the Toda system.Comment: 28 page

Conformal Affine Toda Soliton and Moduli of IIB Superstring on AdS5×S5AdS_5\times S^5

In this paper we interpret the hidden symmetry of the moduli space of IIB superstring on $AdS_{5}\times S^{5}$ in terms of the chiral embedding in $AdS_{5}$, which turns to be the $\mathbb{CP}^{3}$ conformal affine Toda model. We review how the position $\mu$ of poles in the Riemann-Hilbert formulation of dressing transformation and how the value of loop parameters $\mu$ in the vertex operator of affine algebra determines the moduli space of the soliton solutions, which describes the moduli space of the Green-Schwarz superstring. We show also how this affine SU(4) symmetry affinize the conformal symmetry in the twistor space, and how a soliton string corresponds to a Robinson congruence with twist and dilation spin coefficients $\mu$ of twistor.Comment: Final version, Misprints corrected, Note adde

Two-stage thermally induced stable colloidal assemblies from PAAc/PNIPAAm/mPEG graft copolymer in water

A facile approach of forming stable polymeric complexes by the two-stage phase transition of the graft copolymer comprising poly(acrylic acid) (PAAc) as the backbone and poly(N-isopropylacrylamide) (PNIPAAm) and monomethoxy poly(ethylene glycol) (mPEG) as the grafts in water was illustrated. Rather loose and hydrated polymeric aggregates with a characteristic hydrophobic multicore structure, achieved by the first-stage thermally induced phase transition of PNIPAAm grafts, underwent the core structure rearrangement (including multicore fragmentation and fusion) upon the second-stage dehydration of mPEG grafts at 90 degrees C. This was followed by hydrogen-bond pairings of mPEG and PNIPAAm chain segments with unionized AAc residues acting as an effective protective shell against potential hydration of the hydrophobic inner cores during the annealing process. The polymer complexes thus obtained show surprisingly enhanced hydrophobicity of inner cores at 25 degrees C in water and excellent stability of the morphological structure in response to the temperature disturbance. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved

Synthesis and characterization of amphiphilic graft copolymers with poly(ethylene glycol) and cholesterol side chains

Amphiphilic graft copolymers comprising monomeric units of methoxy poly(ethylene glycol) (mPEG)-acrylate, 2-hydroxyethyl methacrylate (HEMA)-cholesterol conjugates and HEMA were synthesized and their properties characterized. The value of the critical micelle concentration (CMC) for these copolymers is linearly proportional to the ratio of the number of mPEG-acrylates to that of the HEMA-cholesterol conjugates per macromolecule (N-PEG/N-c), which is the most important parameter which influences the formation of polymeric micelles. The latter show excellent colloidal stability and their sizes decrease with increasing CMC. Based on the quenching of pyrene fluorescence, the relatively high levels of the loading capacity of pyrene are attributed to the elevated hydrophobicity of the micelle core. The loading capacity of pyrene decreases with increasing CMC. The weight-average partition coefficient for pyrene in polymeric micelles increases with increasing polymer concentration because more micelles are available for accommodating pyrene. (C) 2004 Society of Chemical Industry

Preparation and characterization of amphiphilic poly(ethylene glycol) graft copolymers

Amphiphilic graft copolymers of alkyl methacrylates, methoxy poly(ethylene glycol) (PEG) acrylate, and acrylic acid were synthesized by free radical polymerization. PEG graft copolymers with respect to structure, composition, and average molecular weight were characterized by FT-IR,H-1 NMR, and GPC. The critical micelle concentration and molar mass of the polymeric micelles were determined by fluorescence spectroscopy using pyrene as the fluorescence probe and static laser light scattering, respectively. The formation of polymeric micelles was influenced by the balance of hydrophobicity and hydrophilicity and other factors such as molecular weight of the copolymer products. The molar mass of polymeric micelles increased with mole content of hydrophobic comonomers. Loading capacity and weight average partition coefficient for the pyrene molecules into polymeric micelles were estimated via fluorescence quenching by Cu2+. Fluorescence quenching studies of pyrene indicated that a loose structure of micelles was formed from the graft copolymer containing high content of hydrophilic monomethoxy poly(ethylene glycol) (mPEG) and acrylic acid

Interactions between nonionic Triton X surfactants and cholesterol-containing phosphatidylcholine liposomes

Solubilization kinetics experiments were developed to study the effects of the polyethylene glycol chain length of Triton X surfactants on their interactions with the cholesterol-containing phosphatidylcholine vesicles. An empirical liposome stability ratio was used to describe the vesicle solubilization process. The effectiveness of Triton X surfactants in solubilizing vesicles decreases with increasing polyethylene glycol chain length of surfactants. It was also shown that vesicles containing the intercalated surfactant molecules with the largest number of ethylene glycol units per molecule exhibited the exceedingly retarded solubilization behavior. Independent experiments based on a thermodynamic approach provide supporting evidence for the conclusions obtained from solubilization kinetics experiments. (c) 2006 Elsevier Inc. All rights reserved

(33(4):345-353)Mutagenic Efficiency of Sodium Azide on Rice Variety Tainung 67

在pH 3 的磷酸緩衝溶液中，以3 及6 小時二種處理時問和0.0、1.0 、1.5 及2.0 mM 四種濃度，探討疊氮化鈉對臺農67 號的種根長、萌芽出土率、幼苗高、結實率和存活率等之影響。結果處理時問對幼苗高之效果無顯著差異外，其餘性狀皆與處理時間和濃度呈顯著的負相關，其中種根長和存活率對處理濃度呈現二次曲線迴歸關係，餘三種反應對處理濃度呈直線迴歸關係。五種反應中，種根長和結實率之相關最高。本試驗結論建議：疊氮化鈉處理時間不宜太長，種根長和結實率可作為實用處理時間的指標。 The presoaked seed of rice variety Tainung 67 were treated with sodium azide for 2 time periods, 3 and 6 hrs, at 4 concentrations, 0.0, 1.0, 1.5 and 2.0mM in a pH 3 potassium phosphate buffer solution for mutation breeding. Five related traits at M1 generation were observed, they were seminal root length, germination rate in greenhouse, seedling height, seedset rate and survival rate [percentage of plants that bore one or more seeds]. Except the seedling height on time periods of treatment, there existed a significantly negative correlation regression of all traits on the time duration and concentrations of treatment. The regressions of seminal root length and survival rate on the concentrations showed a quadratic nature, while other traits, respectively, showed a linear regression on the treated concentrations. The highest correlation was found between seminal root length and seedset rate of M1 generation. It is suggested to use a relatively short time period of treatment and to use the seminal root length and seed-set rate of M1 plant as the indicator to eveluate the mutagenic efficiency of sodium azide in rice mutation breeding

Thermoresponsive Interpolymeric Complex Assemblies from Co-association of Linear PAAc Homopolymers with PNIPAAm Segments Containing PAAc-Based Graft Copolymer

In aqueous solution at pH 3.0 and 20 degrees C, poly(acrylic acid)-g-poly(N-isopropylacrylamide)/monomethoxy poly(ethylene glycol) (PAAc-g-PNIPAAm/mPEG) can assemble spontaneously with linear poly(acrylic acid) homopolymers (homoPAAc) into interpolymeric complexes (IPC). The resultant IPC assemblies exhibit a core-corona structure consisting of a hydrophobic PAAc/PNIPAAm complex core surrounded by hydrated PNIPAAm/mPEG coronas. At temperatures above 30 degrees C, the assemblies transform into a core-shell-corona micelle. Highly loose, irregular IPC assemblies developed at a reduced weight ratio of homoPAAc with the graft copolymer at 20 degrees C show particle size enlargement and structural variation above 30 degrees C. By contrast, co-assembly of long homoPAAc chains with the copolymer leads to large aggregates comprising several IPC assemblies interconnected by homoPAAc chain segments

Temperature/pH-induced morphological regulations of shell cross-linked graft copolymer assemblies

Shell cross-linked (SCL) assemblies are prepared from the thermally induced three-layered, onion-like micelles of graft copolymers comprising acrylic acid (AAc) and 2-methacryloylethyl acrylate (MEA) as the backbone units and poly(N-isopropylacrylamide) (PNIPAAm) and monomethoxy poly(ethylene glycol) (mPEG) as the grafts via radical polymerization of the MEA residues within the AAc-rich interfacial layers in the aqueous phase of pH 5.0 at 60 degrees C. The resulting nanosized SCL assemblies exhibit versatile structural regulations in a fully reversible manner in response to changes in pH and temperature. At 20 degrees C, SCL assemblies retain the morphology of vesicle-like hollow microspheres with pH-controlled water influx and particle size. At pH 7.0, SCL assemblies remain invariant in both vesicular structure and size irrespective of the temperature increase beyond the coil-to-globule phase transition of PNIPAAm grafts occurring primarily in a highly individual manner. When the temperature increases from 20 to 60 degrees C at pH 5.0, the hollow particle size is greatly reduced, accompanied by the development of hydrophobic, impermeable PNIPAAm lumens attached to the inside surfaces of the interfacial gel layers. In addition, SCL assemblies undergo a dramatic thermally induced transformation from the vesicle-like to micelle-like morphology by virtue of yielding hydrophobic PNIPAAm inner cores at pH 3.0. The thermally evolved morphology of SCL assemblies is governed by the vesicle structure in response to the effect of pH on the AAc ionization within the interfacial gel layers at ambient temperature. (C) 2010 Elsevier Ltd. All rights reserved