Transformation of amyloid-like fibers, formed from an elastin-based biopolymer, into a hydrogel: an X-ray photoelectron spectroscopy and atomic force microscopy study.

Previous studies have revealed the propensity of elastin-based biopolymers to form amyloid-like fibers when dissolved in water. These are of interest when considered as "ancestral units" of elastin in which they represent the simplest sequences in the hydrophobic regions of the general type XxxGlyGlyZzzGly (Xxx, Zzz = Val, Leu). We normally refer to these biopolymers based on elastin or related to elastin units as "elastin-like polypeptides". The requirement of water for the formation of amyloids seems quite interesting and deserves investigation, the water representing the natural transport medium in human cells. As a matter of fact, the "natural" supramolecular organization of elastin is in the form of beaded-string-like filaments and not in the form of amyloids whose "in vivo" deposition is associated with some important human diseases. Our work is directed, therefore, to understanding the mechanism by which such hydrophobic sequences form amyloids and any conditions by which they might regress to a non-amyloid filament. The elastin-like sequence here under investigation is the ValGlyGlyValGly pentapeptide that has been previously analyzed both in its monomer and polymer form. In particular, we have focused our investigation on the apparent stability of amyloids formed from poly(ValGlyGlyValGly), and we have observed these fibers evolving to a hydrogel after prolonged aging in water. We will show how atomic force microscopy can be combined with X-ray photoelectron spectroscopy to gain an insight into the spontaneous organization of an elastin-like polypeptide driven by interfacial interactions. The results are discussed also in light of fractal-like assembly and their implications from a biomedical point of view.

AFM study of the elastin-like biopolymer poly(ValGlyGlyValGly).

In this paper, we report an AFM study on the supramolecular structures adopted by the synthetic polypentapeptide poly(ValGlyGlyValGly), whose monomeric sequence is an abundant, simple building block of elastin. The polypeptide was analyzed by deposition from both methanolic and aqueous suspensions, showing different behaviors. In methanol, the polypeptide is able to evolve, in a time-dependent way, from layers to ribbons to beaded filaments. When the equilibrium is reached, the formation of well-defined dendritic structures is also observed. This restructuring of the polypentapeptide seems to be reminiscent of a sort of Rayleigh instability. When deposited from aqueous suspensions, the polypeptide self-assembles either in fibrillar networks or in amyloid-like patterns, both of them being found in elastin or elastin-related polypeptides. As a general finding, poly(ValGlyGlyValGly) seems to constitute an excellent mimetic of the supramolecular properties of native elastin.

Hereditary symphalangism with associated tarsal synostosis and hypophalangism.

Symphalangism is a rare genetic condition that may represent the earliest documentation of mendelian inheritance in man. The disorder results in interphalangeal joint fusion in the hands and feet. The authors review this rare condition and present a case study consisting of four generations with 15 affected family members. The association of multiple tarsal synostosis and the previously unreported associated occurrence of pedal hypophalangism in this pedigree is presented.

Fifth metatarsal distal oblique wedge osteotomy utilizing cortical screw fixation.

A retrospective study of 26 tailor bunionectomies is presented. The use of an apical axis guide, reciprocal planing, and strict application of Association for Osteosynthesis principles offers ease of application, increased stability, and greater healing predictability than other techniques. Potential complications such as angular displacement, shortening, nonunion, and transfer lesions are minimized.

Chitin: New facets of research.

Research on chitin as a marine resource is pointing to novel applications for this cellulose-like biopolymer. Discovery of nondegrading solvent systems has permitted the spinning of filaments, for example, for use as surgical sutures. New methods for preparing the bioactive alkyl glycoside of N-acetyl-D-glucosamine (the monomer unit of chitin) and a microcrystalline chitin has encouraged their use as promoters for growth of bifidobacteria and as an aid in digestion of high-lactose cheese whey by domestic animals. Chitin-protein complexes of several crustacean species show great variability in ratios of chitin to covalently bound protein and in residual protein in the "purified" chitins.