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Recently, magnesium has been investigated as a promising bioresorbable orthopedic biomaterial. Its mechanical properties are very similar to natural bone, making it appropriate for load-bearing orthopedic fracture repair applications. However, significant hurdles remain regarding the design of practical implants and methods to control degradation and enhance biocompatibility. Although attempts have been made to hinder magnesium's rapid corrosion via alloying and coating, these studies have used solid monoliths. In an effort to reduce the amount of alloy used for implantation in a shape that mimics cortical bone shape, this study used a thin sheet of Mg AZ31 which was rolled into hollow cylindrical scaffolds. The scaffold was coated with different amounts of Ca-P; this implant demonstrated slowed corrosion in simulated body fluid (SBF) as well as enhanced biocompatibility for mesenchymal stem cells (MSC). In vivo implantation of magnesium alloy scaffold adjacent to the rat femur showed significant biointegration with further deposition of complex Mg-Ca phosphates/carbonates typical of natural bone. Finally, the implant was placed in a critical-size ulna defect in live rabbits, which lead to radiographic union and partial restoration of biomechanical strength in the defect. This study demonstrated that a thin sheet of coated Mg alloy that was spirally wrapped wound be a promising orthopedic biomaterial for bone repair.

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Alkylation of cysteine residues has been used extensively for characterization of proteins and their mode of action in biological systems, research endeavors that are at the core of proteomics. Treatment with a simple alkylating agent such as [2-(13)C] bromoethylamine would result in labeled thialysine at the ε-position. This chemical modification of proteins would allow investigations via both (13)C NMR spectroscopy and mass spectrometry. However [2-(13)C] labeled bromoethylamine is not available commercially. We investigated its synthesis at acid pH with the goal of obtaining singly labeled bromoethylamine and understanding the mechanistic details of the reaction. Based on our experimental and theoretical results, bromination of [2-(13)C] labeled ethanolamine in acidic conditions takes place via exclusive attack of the nucleophile (HBr) at the hydroxyl bearing C. Moreover, hydrogen bonding guides the nucleophilic attack, resulting in no label scrambling of the bromoethylamine product. Protein alkylation at cysteine residue with the synthesized Br(13)CH(2)CH(2)NH(2)-HBr is successful. Ab initio calculations in which CH(3)SH serves as a model for the cysteine residue suggest that in gas phase intermolecular attack by the sulfur bearing nucleophile is favored over the intramolecular substitution by the amino group by 15.4 kJ mol(-1). Solution modeling shows that the trend is preserved at basic pH, which is the experimental one, but is reversed at neutral pH.