Genetic Synthesis of Periodic Protein Materials

Genetic engineering offers a novel approach to the development of advanced polymeric materials, in particular protein-based materials. Biological synthesis provides levels of control of polymer chain architecture that cannot yet be attained by current methods of chemical synthesis. In addition to employing naturally occurring genetic templates artificial genes can be designed to encode completely new materials with customized properties. In the present paper we: 1) review the concepts and technology of creating protein-based materials by genetic engineering, 2) discuss the merits of producing crystalline lamellar proteins by this approach, and 3) review progress made by our group in generating such materials by genetic strategies. Full descriptions appear elsewhere about the parameters to be considered in designing artificial protein genes of this type, the effectiveness of different gene construction and expression strategies utilized by us thus far and, the specific properties of the various materials derived from these efforts (1,2). Progress made by other groups involved in developing periodic proteins by molecular biological strategies are described in refs. 3-8. The latter studies include genetic engineering of artificial silk-like proteins (3,4), poly-aspartylphenylalanine (5), an α/β barrel domain (octarellin; 6), the collagen tripeptide GlyProPro (7) and human tropoelastin (8). Advances with the silk-like proteins (SLP) have been particularly impressive. In addition to producing multi-gram quantities of pure SLP homopolymers, this group has successfully generated block copolymers of SLP interspersed with core peptides of mammalian elastin and the human fibronectin cell attachment element. While publications are still lacking it appears that a numiber of groups are striving to create genetically engineered variants of the repetitive bioadhesive proteins produced by mussels and barnacles (9)

Biocatalytic Synthesis of Polymers of Precisely Defined Structures

The fabrication of functional nanoscale devices requires the construction of complex architectures at length scales characteristic of atoms and molecules. Currently microlithography and micro-machining of macroscopic objects are the preferred methods for construction of small devices, but these methods are limited to the micron scale. An intriguing approach to nanoscale fabrication involves the association of individual molecular components into the desired architectures by supramolecular assembly. This process requires the precise specification of intermolecular interactions, which in turn requires precise control of molecular structure

Neurosarcoidosis resembling meningioma: MRI characteristics and pathologic correlation.

A 37-year-old woman had visual changes. Magnetic resonance imaging showed an extraaxial mass in the anterior clinoid region that was presumed to be meningioma. There was no evidence of systemic or leptomeningeal disease. Pathologic findings were consistent with sarcoidosis. Isolated mass-like neurosarcoidosis, without systemic or leptomeningeal disease is difficult to diagnose preoperatively

Biomimetic organization: Octapeptide self-assembly into nanotubes of viral capsid-like dimension

The controlled self-assembly of complex molecules into well defined hierarchical structures is a promising route for fabricating nanostructures. These nanoscale structures can be realized by naturally occurring proteins such as tobacco mosaic virus, capsid proteins, tubulin, actin, etc. Here, we report a simple alternative method based on self-assembling nanotubes formed by a synthetic therapeutic octapeptide, Lanreotide in water. We used a multidisciplinary approach involving optical and electron microscopies, vibrational spectroscopies, and small and wide angle x-ray scattering to elucidate the hierarchy of structures exhibited by this system. The results revealed the hexagonal packing of nanotubes, and high degree of monodispersity in the tube diameter (244 Å) and wall thickness (≈18 Å). Moreover, the diameter is tunable by suitable modifications in the molecular structure. The self-assembly of the nanotubes occurs through the association of β-sheets driven by amphiphilicity and a systematic aromatic/aliphatic side chain segregation. This original and simple system is a unique example for the study of complex self-assembling processes generated by de novo molecules or amyloid peptides