3 research outputs found

    Undulating the Lamellar Interface of Polymer–Surfactant Complex by Dendrimer

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    Self-assembly of the supramolecules formed by the complexation between poly­(amidoamine) (PAMAM) generation four (G4) dendrimer and the surfactant, dodecylbenzene­sulfonic acid (DBSA), generated a hexagonal columnar phase and a typical flat lamellar phase at low and high surfactant binding ratio, respectively, due to the dominance of the dendrimer to attain its natural curvature and the surfactant alkyl tails to reduce their hydrophobic interaction energy and packing frustration. Most strikingly, the delicate balance between these two free energy components at the intermediate binding ratios resulted in an undulated lamellar structure characterized by the centered rectangular unit cell. The finding demonstrates the power of dendrimer as a building block for expanding the morphological window of polymeric assemblies by modulating the interfacial curvature of microphase-separated structure

    Spatial Distributions of Guest Molecule and Hydration Level in Dendrimer-Based Guest–Host Complex

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    Using the electrostatic complex of G4 poly­(amidoamine) (PAMAM) dendrimer with an amphiphilic surfactant as a model system, contrast variation small angle neutron scattering (SANS) is implemented to resolve the key structural characteristics of dendrimer-based guest–host system. Quantifications of the radial distributions of the scattering length density and the hydration level within the complex molecule reveal that the surfactant is embedded in the peripheral region of dendrimer and the steric crowding in this region increases the backfolding of the dendritic segments, thereby reducing the hydration level throughout the complex molecule. The insights into the spatial location of the guest molecules as well as the perturbations of dendrimer conformation and hydration level deduced here are crucial for the delicate design of dendrimer-based guest–host system for biomedical applications

    PEGylation Site-Dependent Structural Heterogeneity Study of MonoPEGylated Human Parathyroid Hormone Fragment hPTH(1–34)

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    The structures of C- and N-terminally monoPEGylated human parathyroid hormone fragment hPTH(1–34) as well as their unmodified counterparts, poly­(ethylene glycol) (PEG) and hPTH(1–34), have been studied by small-angle neutron scattering (SANS). The scattering results show that free hPTH(1–34) in 100 mM phosphate buffer (pH 7.4) aggregates into clusters. After conjugation with PEG, the PEG–peptide conjugates self-assemble into a supramolecular core–shell structure with a cylindrical shape. The PEG chains form a shell around the hPTH­(1–34) core to shield hPTH(1–34) from the solvent. The detailed structural information on the self-assembled structures is extracted from SANS using a model of the cylindrical core with a shell of Gaussian chains attached to the core surface. On the basis of the data, because of the charge–dipole interactions between the conjugated PEG chain and the peptide, the conjugated PEG chain forms a more collapsed conformation compared to free PEG. Moreover, the size of the self-assembled structures formed by the C-terminally monoPEGylated hPTH­(1–34) is about 3 times larger than that of the N-terminally monoPEGylated hPTH(1–34). The different aggregation numbers of the self-assembled structures, triggered by different PEGylation sites, are reported. These size discrepancies because of different PEGylation sites could potentially affect the pharmacokinetics of the hPTH(1–34) drug
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