Fibrous Polymers in Textile Prospect for Tissue Engineering Development

Tissue engineering as an interdisciplinary field implies fibrous polymers as extracellular matrix as biologic support. The paper is a review on basic lines of the answer of textiles items at the biologic complex action. One carries out the evolution usage of the following polysaccharide supports: cellulose, gellan, pullulan, chitosan, hyaluronic acid, as well the collagen as a protein representative for a potential usage in an extracellular matrix. One presents the advantages and drawbacks adjusted to an online system and to new procedures available to develop a biologic structure on a textile support according with the main achievements reported in the literature of last years.

TRY, a new computer program for crystal structure analysis from diffraction data based on internal coordinates and on a molecular modelling procedure free of redundant coordinates

A procedure is described which allows structure modelling using a number of internal coordinates that does not exceed the number of degrees of freedom of the problem. The modelling then becomes a strictly analytical procedure and structural refinement from diffraction data can be carried out avoiding the use of singular matrices. A practical `symbolic language' with a simple syntax allows easy molecular building even in intricate cases. Based on this procedure, a new computer program for the study of crystal structures (TRY), particularly suited for fibrous polymers, has been created. The program is available at http://www.theochem.unisa.it/try.html.

New solutions to the problems of chain orientation and chain continuity in structure analysis of fibrous polymers. A reconsideration of the structure of polyisobutene

Two points of general interest in structural refinement of polymers based on internal coordinates are discussed: the chain orientation and the chain continuity. Using a proprietary computer program, based on revised approaches to these questions, the structure of polyisobutene has been reconsidered, using new X-ray diffraction measurements (Fuji image plate) and performing a structure refinement based on internal coordinates. Three refinement schemes, with a decreasing number of degrees of freedom, have been considered, with the conclusion that the distortion from the 83regular helix, claimed by Tadokoro [(1979).Structure of Crystalline Polymers, p. 136. New York: Wiley-Interscience], is confirmed, though lower than supposed. The new procedures implemented for chain orientation and chain continuity work excellently.

A small surface hydrophobic stripe in the coiled-coil domain of type I keratins mediates tetramer stability

Intermediate filaments (IFs) are fibrous polymers encoded by a large family of differentially expressed genes that provide crucial structural support in the cytoplasm and nucleus in higher eukaryotes. The mechanisms involved in bringing together ∼16 elongated coiled-coil dimers to form an IF are poorly defined. Available evidence suggests that tetramer subunits play a key role during IF assembly and regulation. Through molecular modeling and site-directed mutagenesis, we document a hitherto unnoticed hydrophobic stripe exposed at the surface of coiled-coil keratin heterodimers that contributes to the extraordinary stability of heterotetramers. The inability of K16 to form urea-stable tetramers in vitro correlates with an increase in its turnover rate in vivo. The data presented support a specific conformation for the assembly competent IF tetramer, provide a molecular basis for their differential stability in vitro, and point to the physiological relevance associated with this property in vivo.