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Junbai Li

Publications and source records attributed to Junbai Li.

25 records · Page 2Linked to original sources
PubMed2003

Highly flexible polyelectrolyte nanotubes.

A pressure-filter-template approach was employed to prepare polyelectrolyte nanotubes through layer-by-layer deposition in the alumina template. With the thicker wall, the ordered polymer nanotubes possess a high flexibility. The results demonstrate that the electrostatic interactions of polyelectrolytes play a key role in fabricating water-soluble charged polymer nanotubes. The structure of the polyelectrolyte nanotube was confirmed by SEM, TEM, and UV, respectively.

Journal Article↗
PubMed2003

Phospholipase A2 hydrolysis of mixed phospholipid vesicles formed on polyelectrolyte hollow capsules.

Mixtures of the phospholipids L-alpha-dimyristoylphosphatidic acid (DMPA) and L-alpha-dipalmitoylphosphatidylcholine (DPPC) have been successfully adsorbed onto the charged surface of multilayer polyelectrolyte capsules to form a novel vesicle. Leaving such vesicles in phospholipase A(2) solution, we observed the hydrolysis reaction on the surface of the lipid/polymer vesicles and a permeability change before and after the reaction by confocal-laser scanning microscopy (CLSM). A capsule with adjustable permeability was constructed. This method may provide new features for drug-release vesicles.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2003

Direct observations of the cleavage reaction of an L-DPPC monolayer catalyzed by phospholipase A2 and inhibited by an indole inhibitor at the air/water interface.

The enzymatic hydrolysis of an L-dipalmitoylphosphatidylcholine (L-DPPC) monolayer at the air/water interface, catalyzed by phospholipase A(2) (PLA(2)), serves as a model for biospecific interfacial reactions. The cleavage of L-DPPC was investigated by Brewster angle microscopy. Different types of domain defects were observed to form in the coexisting liquid expanded and liquid condensed phases during the hydrolysis reaction. The adsorption of the enzyme was quantitatively recorded as the increase of the surface pressure over a fixed molecular area with time. In the case of L-DPPC, the surface pressure first increases and then starts to decrease, which indicates that a soluble product (lysolipid) is produced during the catalytic cleavage reaction. The increase and decrease of the surface pressure, which corresponds to the change of shape and number density of domains, indicated the occurrence of the following processes: adsorption of PLA(2), cleavage reaction, and rearrangement of substrate and product molecules at the interface. Addition of a PLA(2) inhibitor to the lipid monolayer leads to a fast surface pressure increase after enzyme injection. The surface pressure reaches a maximum value and then does not change for a long time. During this period, no change in the domain shape and number density was observed, which indicates that the enzyme is inhibited for a certain period of time. The experimental results provide the possibility of a direct way to prove inhibitor activity.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2003

Polymer-stabilized phospholipid vesicles formed on polyelectrolyte multilayer capsules.

Phospholipid vesicles on polyelectrolyte multilayer shells can be stabilized against ethanol by coating a single cationic polyelectrolyte. Confocal laser scanning microscopy (CLSM) proved that the lipids were stabilized by cationic polyelectrolytes and the permeability to small hydrophilic dyes was decreased. Measurements of fluorescence recovery after photo-bleaching (FRAP) with individual capsules enable quantification of release profiles.

Biopolymers↗
PubMed2003

Dynamic and morphological investigation of phospholipid monolayer hydrolysis by phospholipase C.

The hydrolytic reaction of L-alpha-dipalmitoylphosphatidylcholine (L-DPPC) monolayer catalyzed by phospholipase C (PLC) has been investigated using monomolecular membrane technique and Brewster angle microscopy (BAM) at the air/water interface. The curves of surface pressure as a function of time determined a lag-burst process of L-DPPC monolayer hydrolysis by PLC. The BAM images recorded the changes of domains formed in the coexistence region of liquid-condensed (LC) and liquid-expanded (LE) phases during the monolayer hydrolysis. The changes of domain shape and size and the increase of domain number reflect the decrease of reactant and molecular rearrangement process of the main hydrolysis product, dipalmitoylglycerol (DPG). A new phase was observed after the hydrolysis reaction was completed.

1,2-Dipalmitoylphosphatidylcholine↗