Multifarious Polymorphism of a Multiblock Amphiphilic Macrocycle Bearing Thermally Responsive Polyether Segment

Formation of multiple crystalline phases of a multiblock amphiphilic macrocycle <b>AT2B</b> is demonstrated. <b>AT2B</b> forms a single crystal (Cr-α) by vapor diffusion and shows reversible single-crystal-to-single-crystal transition between two crystalline phases (Cr-α and Cr-β) by a temperature change, and crystalline <b>AT2B</b> (Cr-β) melts at 422 K, and the cooling rate from the melt influences the phase of the solid formed. By cooling at 1.0 K min^–1, <b>AT2B</b> forms crystalline phases (Cr-γ and Cr-δ), which are different from both Cr-α and Cr-β. On the other hand, cooling at 2.0 K min^–1 results in the formation of an amorphous phase, and a mechanical stress also triggers a crystal-to-amorphous solid transition. Interestingly, the amorphous solid crystallizes to give the fifth crystalline phase (Cr-γ) upon heating before melting. It is suggested that these multiple phase transitions are driven by thermal conformational changes at the tetraethylene glycol chains of <b>AT2B</b>

Contrasting Topological Effect of PEG-Containing Amphiphiles to Natural Lipids on Stability of Vesicles

Topology of amphiphiles is important to control physicochemical properties of supramolecular assemblies. Nature demonstrates higher stability of membrane composed of lipids with a macrocyclic aliphatic tail than those with linear tails, which likely results from the restricted molecular structures of the macrocyclic lipids, allowing for closer molecular packing. In contrast, here we report that a PEG-containing macrocyclic amphiphile shows lower stability of vesicles than the corresponding acyclic one. The macrocyclic amphiphile consists of an aromatic hydrophobic part with chirality in which both ends are strapped by octaethylene glycol via phosphoric ester groups, while the acyclic amphiphile bears tetraethylene glycol chains attached to both ends of the hydrophobic part. Because of the thermoresponsive property of PEG to change its conformation, the hydrophobic part of the macrocyclic amphiphile undergoes a larger thermal conformational change than that of the acyclic one. In addition, the cyclic amphiphile has a larger molecular area, which likely reduces the vesicular stability compared with the acyclic one. Such a contrasting topological effect caused by macrocyclization at the aliphatic part seen in the natural system and at the hydrophilic part demonstrated in this study leads to expand the molecular design of amphiphiles for both increasing and decreasing the stability of vesicles by molecular topology

A plausible reaction mechanism of the intra- and intermolecular nucleophilic substitutions to prompt transetherification.

<p>A plausible reaction mechanism of the intra- and intermolecular nucleophilic substitutions to prompt transetherification.</p

Ether formation between 1 and 2.

<p>Ether formation between 1 and 2.</p

Ether formation between tetraethylene glycol tosylate 2a and a) monoalcohol 8, b) propane-1,3-diol 11 and c) 2-(hydroxymethyl)propane-1,3-diol 13.

<p>Reaction time was 12 h. Yields were calculated based on the isolated amounts. ND: not detected.</p

MALDI-TOF-MS spectrum of the crude product extracted by CHCl₃ for the reaction in Table 1, Entry 1.

<p>Structures of 6 and 7 are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091912#pone-0091912-g003" target="_blank">Figure 3</a>. Matrix: α-cyano-4-hydroxycinnamic acid.</p

Coacervate Formation of Elastin-like Polypeptides in Explicit Aqueous Solution Using Coarse-Grained Molecular Dynamics Simulations

We performed coarse-grained molecular dynamics simulations with the Martini3 force field to investigate elastin-like polypeptide (ELP) coacervate formation and its internal structural and dynamics properties. Coacervate formation was found to be enhanced with increasing polymer concentration and polymer length, whereas no significant changes in the structural and dynamic properties inside the coacervate phase were observed among coacervates with different polymer concentrations and polymer lengths. The ion and water concentrations as well as the diffusion coefficients of water inside a coacervate were found to be reduced compared with that in bulk water. In addition, ELP phase separation behaviors were also observed experimentally and the trend of ELP concentration/length-dependent formation of a coacervate in the simulations was found to be in qualitative agreement with our experimental observations. Furthermore, simulations of the partitioning of RNA polymers demonstrate that an RNA polymer with ethyl (hydrophobic) modification favors the inside of a coacervate and shows a larger radius of gyration in comparison with a normal RNA polymer without modification (negatively charged). Our simulations provide a means to explore the requirement for control over coacervate formation and stability in a wide range of conditions. Understanding how specific sequence and structural features affect coacervate morphology and stability could help in the design of new biopolymers with additional desirable properties

Coacervate Formation of Elastin-like Polypeptides in Explicit Aqueous Solution Using Coarse-Grained Molecular Dynamics Simulations

We performed coarse-grained molecular dynamics simulations with the Martini3 force field to investigate elastin-like polypeptide (ELP) coacervate formation and its internal structural and dynamics properties. Coacervate formation was found to be enhanced with increasing polymer concentration and polymer length, whereas no significant changes in the structural and dynamic properties inside the coacervate phase were observed among coacervates with different polymer concentrations and polymer lengths. The ion and water concentrations as well as the diffusion coefficients of water inside a coacervate were found to be reduced compared with that in bulk water. In addition, ELP phase separation behaviors were also observed experimentally and the trend of ELP concentration/length-dependent formation of a coacervate in the simulations was found to be in qualitative agreement with our experimental observations. Furthermore, simulations of the partitioning of RNA polymers demonstrate that an RNA polymer with ethyl (hydrophobic) modification favors the inside of a coacervate and shows a larger radius of gyration in comparison with a normal RNA polymer without modification (negatively charged). Our simulations provide a means to explore the requirement for control over coacervate formation and stability in a wide range of conditions. Understanding how specific sequence and structural features affect coacervate morphology and stability could help in the design of new biopolymers with additional desirable properties

Coacervate Formation of Elastin-like Polypeptides in Explicit Aqueous Solution Using Coarse-Grained Molecular Dynamics Simulations

We performed coarse-grained molecular dynamics simulations with the Martini3 force field to investigate elastin-like polypeptide (ELP) coacervate formation and its internal structural and dynamics properties. Coacervate formation was found to be enhanced with increasing polymer concentration and polymer length, whereas no significant changes in the structural and dynamic properties inside the coacervate phase were observed among coacervates with different polymer concentrations and polymer lengths. The ion and water concentrations as well as the diffusion coefficients of water inside a coacervate were found to be reduced compared with that in bulk water. In addition, ELP phase separation behaviors were also observed experimentally and the trend of ELP concentration/length-dependent formation of a coacervate in the simulations was found to be in qualitative agreement with our experimental observations. Furthermore, simulations of the partitioning of RNA polymers demonstrate that an RNA polymer with ethyl (hydrophobic) modification favors the inside of a coacervate and shows a larger radius of gyration in comparison with a normal RNA polymer without modification (negatively charged). Our simulations provide a means to explore the requirement for control over coacervate formation and stability in a wide range of conditions. Understanding how specific sequence and structural features affect coacervate morphology and stability could help in the design of new biopolymers with additional desirable properties

Coacervate Formation of Elastin-like Polypeptides in Explicit Aqueous Solution Using Coarse-Grained Molecular Dynamics Simulations

We performed coarse-grained molecular dynamics simulations with the Martini3 force field to investigate elastin-like polypeptide (ELP) coacervate formation and its internal structural and dynamics properties. Coacervate formation was found to be enhanced with increasing polymer concentration and polymer length, whereas no significant changes in the structural and dynamic properties inside the coacervate phase were observed among coacervates with different polymer concentrations and polymer lengths. The ion and water concentrations as well as the diffusion coefficients of water inside a coacervate were found to be reduced compared with that in bulk water. In addition, ELP phase separation behaviors were also observed experimentally and the trend of ELP concentration/length-dependent formation of a coacervate in the simulations was found to be in qualitative agreement with our experimental observations. Furthermore, simulations of the partitioning of RNA polymers demonstrate that an RNA polymer with ethyl (hydrophobic) modification favors the inside of a coacervate and shows a larger radius of gyration in comparison with a normal RNA polymer without modification (negatively charged). Our simulations provide a means to explore the requirement for control over coacervate formation and stability in a wide range of conditions. Understanding how specific sequence and structural features affect coacervate morphology and stability could help in the design of new biopolymers with additional desirable properties