Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Isolation and expansion of self-renewing neural cells ex vivo are required for neural tissue repair in regenerative medicine. Neurogenesis occurs in restricted areas of postnatal mammalian brain including dentate gyrus and subventricular zone. We developed a simple method to entrap migrating neural cells (potential neuroprogenitors) from postnatal hippocampal organotypic cultures in three-dimensional (3-D) peptide nanofiber scaffolds. A few hours after placing the hippocampal slices in culture, cell proliferation activity at the "interface zone" between the tissue slice and the membrane culture surface was observed. Pulse-chase experiments using 5-bromodeoxyuridine (BrdU), which measures mitotic activity, showed that a number of cells incorporated BrdU at the interface zone. The number of BrdU+ cells increased exponentially during the first 3 days of exposure to the label. The BrdU+ cells also stained positive for glial fibrillary acidic protein (2.2 ± 0.5%), a marker for astroglia; and for βIII tubulin (...

Entrapment of migrating hippocampal neural cells in three-dimensional peptide nanofiber scaffold.

The self-assembling peptide EAK16-II is capable of stabilizing hydrophobic compounds to form microcrystal suspensions in aqueous solution. Here, the ability of this peptide to stabilize the hydrophobic anticancer agent ellipticine is investigated. The formation of peptide-ellipticine suspensions is monitored with time until equilibrium is reached. The equilibration time is found to be dependent on the peptide concentration. When the peptide concentration is close to its critical aggregation concentration, the equilibration time is minimal at 5 h. With different combinations of EAK16-II and ellipticine concentrations, two molecular states (protonated or cyrstalline) of ellipticine could be stabilized. These different states of ellipticine significantly affect the release kinetics of ellipticine from the peptide-ellipticine complex into the egg phosphatidylcholine vesicles, which are used to mimic cell membranes. The transfer rate of protonated ellipticine from the complex to the vesicles is much faster than that of crystalline ellipticine. This observation may also be related to the size of the resulting complexes as revealed from the scanning electron micrographs. In addition, the complexes with protonated ellipticine are found to have a better anticancer activity against two cancer cell lines, A549 and MCF-7. This work forms the basis for studies of the peptide-ellipticine suspensions in vitro and in vivo leading to future development of self-assembling peptide-based delivery of hydrophobic anticancer drugs.

Self‐Assembling Peptide as a Potential Carrier for Hydrophobic Anticancer Drug Ellipticine: Complexation, Release and In Vitro Delivery

Beyond molecular chemistry based on the covalent bond, supramolecular chemistry aims at developing highly complex chemical systems from components interacting through noncovalent intermolecular forces. Over the past quarter century, supramolecular chemistry has grown into a major field and has fueled numerous developments at the interfaces with biology and physics. Some of the conceptual advances and future challenges are profiled here.

https://dialnet.unirioja.es/descarga/articulo/1051047.pdf

Toward self-organization and complex matter

The phosphorus bond in chemical systems, which is an inter- or intramolecular noncovalent interaction, occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a covalently or coordinately bonded phosphorus atom in a molecular entity and a nucleophile in another, or the same, molecular entity. It is the second member of the family of pnictogen bonds, formed by the second member of the pnictogen family of the periodic table. In this overview, we provide the reader with a snapshot of the nature, and possible occurrences, of phosphorus-centered pnictogen bonding in illustrative chemical crystal systems drawn from the ICSD (Inorganic Crystal Structure Database) and CSD (Cambridge Structural Database) databases, some of which date back to the latter part of the last century. The illustrative systems discussed are expected to assist as a guide to researchers in rationalizing phosphorus-centered pnictogen bonding in the rational design of molecular complexes, crystals, and materials and their subsequent characterization.

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The Phosphorus Bond, or the Phosphorus-Centered Pnictogen Bond: The Covalently Bound Phosphorus Atom in Molecular Entities and Crystals as a Pnictogen Bond Donor

Publisher Summary Molecular self-assembly is the spontaneous organization of molecules under near thermodynamic equilibrium conditions into structurally well-defined and stable arrangements through non-covalent interactions. Such interactions typically include hydrogen bonding, electrostatic attraction, and van der Walls interactions. Frequently, molecular self assembly relies on chemical complementarity and structural compatibility. These fundamentals are critical to the design of molecular building blocks required for the fabrication of functional macrostructures. Molecular fabrication involves not only the understanding of molecular self-assembly, but also the knowledge of surface science. Materials communicate with their environment via their interfaces. Such communications are determined by the interfacial properties of the materials. In particular, understanding the molecular mechanisms and signaling cascades between living cells and their environment is crucial to fabricate novel biomaterials; biomineralization requires functional templates to direct and regulate the mineral deposition and the crystal growth. The molecular interactions in molecular self-assembly, in guest-host molecular recognition, and in molecular biomimetics are governed by the interfacial communications, which eventually control the material structures and their mechanical, electronic, magnetic, and solution properties.

S.Y. Fung

Papers

12 – Self-assembly of peptides and its potential application