Silk-like Protein Research Articles

Arthropod cuticle: a natural composite shell system

Abstract The cuticle of arthropods (jointed-limb animals), and especially of insects is, by biological standards, a relatively simple composite. It is a single external layer of material forming the skeleton and many sense organs. The fibrous phase is crystalline chitin making nanofibrils of about 3 nm diameter, a few hundreds of nanometers long and a modulus probably in excess of 150 GPa. At least two surfaces of the nanofibril can have silk-like protein attached through specific H-bonds; the rest of the protein is globular. The protein matrix stiffens through dehydration controlled by the introduction of hydrophobic phenolics. Crustacea add up to 40% calcium salts. The stiffness of cuticle can range from tens of GPa to 1 kPa. It can be hardened by the addition of Zn or Mn. It can form springs and change its stiffness and plasticity under the control of the animal.

Mechanical properties of biocompatible protein polymer thin films

A silklike protein with fibronectin functionality (SLPF) (ProNectin F®, Protein Polymer Technologies, Inc.) is a genetically engineered protein polymer containing structural and biofunctional segments. The mechanical properties and deformation mechanisms of electrostatically deposited SLPF thin films were examined by scratch testing, tensile testing, and nanoindentation. Scanning electron microscopy and scanned probe microscopy revealed that the macroscopic properties were a sensitive function of microstructure. The SLPF films were relatively brittle in tension, with typical elongation-to-break values of 3%. Nanoindentation data were fit to a power law relationship.

Ultrastructural and chemical examination of paper and pedicel from laboratory and field nests of the social waspPolistes metricus say

The ultrastructure and chemical composition of paper and pedicel from nests ofPolistes metricus that were constructed in the laboratory from known building material were compared to paper and pedicel from nests constructed in the field. Scanning electron micrographs showed the addition of a gluelike secretion from the wasp to the construction material. Solid-state [(13)C]NMR, elemental analyses, and amino acid analyses indicate that this secretion is a silklike protein with serine, glycine, alanine, and proline comprising 65-73% of the identified residues.

Protein synthesis in the salivary glands of Rhynchosciara americana

During the fourth larval instar the salivary gland of Rhynchosciara americana is engaged in the synthesis of a silk-like protein secretion. This secretion is composed of a small number of polypeptides whose molecular weights vary between 20,300 and 152,000. The polypeptide composition of this secretion changes as the larvae pass through different periods in the fourth instar toward pupation, and the size of its constituent polypeptides generally decreases. When the larvae stop feeding at the beginning of communal cocoon spinning (third period), an exponential increase in the production of secretion occurs until it represents 75% of the protein synthesis in the gland. In vitro experiments with [ 3H]leucine incorporation show that all the major secreted polypeptides are produced in the posterior region of the gland, with the anterior region making only a small contribution. Each polypeptide is produced during a specific stage of larval development. Thus the salivary gland follows a precise developmental pattern of protein synthesis which is typical of highly specialized organs.