Currently, sustainability initiatives that use green chemistry to improve and/or protect our global environment are becoming focal issues in many fields of research. Instead of using toxic chemicals for the reduction and stabilisation of metallic nanoparticles, the use of various biological entities has received considerable attention in the field of nanobiotechnology. Among the many possible natural products, polysaccharides and biologically active plant products represent excellent scaffolds for this purpose. Polysaccharides have hydroxyl groups, a hemiacetal reducing end, and other functionalities that can play important roles in both the reduction and the stabilisation of metallic nanoparticles. Among the various categories of compounds in plants that have potent biological activities, phytochemicals are emerging as an important natural resource for the synthesis of metallic nanoparticles. The focus of this review is the application of polysaccharides and phytochemicals in the green synthesis of gold and silver nanoparticles to afford biocomposites with novel uses in nanomedicine and as nanocomposites.

The solar water-splitting protein complex, photosystem II, catalyzes the light-driven oxidation of water to dioxygen in Nature. The four-electron oxidation reaction of water occurs at the tetranuclear manganese-calcium-oxo catalytic cluster that is present in the oxygen-evolving complex of photosystem II. The mechanism of light-driven water oxidation has been a subject of intense interest, and the oxygen-evolving complex of photosystem II has been studied extensively by structural and biochemical methods. While the recent X-ray crystal structures and single-crystal EXAFS investigations provide a model for the geometry of the tetranuclear manganese-calcium-oxo catalytic cluster, there is limited knowledge of the protein environment that surrounds the catalytic cluster. In this study, we demonstrate the application of two-dimensional hyperfine sublevel correlation spectroscopy to determine the magnetic couplings of the catalytic cluster with the (14)N atoms of surrounding amino acid residues in the S(2) state of the oxygen-evolving complex of photosystem II. We utilize two-dimensional difference spectroscopy to facilitate unambiguous assignments of the spectral features and identify at least three separate (14)N atoms that are interacting with the catalytic cluster in the S(2) state. The results presented here, for the first time, identify previously unknown ligands to the catalytic cluster of photosystem II and provide avenues for the assignment of residues by site-directed mutagenesis and the refinement of computational and mechanistic models of photosystem II.

Glycosaminoglycans are a family of polysaccharides widely distributed in all eukaryotic cells. These polyanionic, linear chain polysaccharides are composed of repeating disaccharide units that are often differentially substituted with sulfo groups. The diversity of glycosaminoglycan structures in cells, tissues and among different organisms reflect their functional an evolutionary importance. Glycosaminoglycan composition and structure also changes in development, aging and in disease progression, making their accurate and reliable analysis a critical, albeit, challenging endeavor. Quantitative disaccharide compositional analysis is one of the primary ways to characterize glycosaminoglycan composition and structure and has a direct relationship with glycosaminoglycan biological functions. In this study, glycosaminoglycan disaccharides, prepared from heparan sulfate/heparin, chondroitin sulfate/dermatan sulfate and neutral hyaluronic acid using multiple polysaccharide lyases, were fluorescently labeled with 2-aminoacridone, fractionated into 17 well-resolved components by reverse-phase ultra-performance liquid chromatography, and analyzed by electrospray ionization mass spectrometry. This analysis was successfully applied to cell, tissue, and biological fluid samples for the picomole level detection of glycosaminoglycan composition and structure.

A high resolution method for the separation and analysis of disaccharides prepared from heparin and heparan sulfate (HS) using heparin lyases is described. Ultraperformance liquid chromatography in a reverse-phase, ion-pairing mode efficiently separates eight heparin/HS disaccharides. The disaccharides can then be detected and quantified using electrospray ionization mass spectrometry. This method is particularly useful in the analysis of small amounts of biological samples, including cells, tissues and biological fluids, as it provides high sensitivity without being subject to interference from proteins, peptides and other sample impurities.

Proteoglycans, comprised of a core protein to which glycosaminoglycan chains are covalently linked, are an important structural and functional family of macromolecules found in the extracellular matrix. Advances in our understanding of biological interactions have lead to a greater appreciation for the need to design tissue engineering scaffolds that incorporate mimetics of key extracellular matrix components. A variety of synthetic and semisynthetic molecules and polymers have been examined by tissue engineers that serve as structural, chemical and biological replacements for proteoglycans. These proteoglycan mimetics have been referred to as neoproteoglycans and serve as functional and therapeutic replacements for natural proteoglycans that are often unavailable for tissue engineering studies. Although neoproteoglycans have important limitations, such as limited signaling ability and biocompatibility, they have shown promise in replacing the natural activity of proteoglycans through cell and protein binding interactions. This review focuses on the recent in vivo and in vitro tissue engineering applications of three basic types of neoproteoglycan structures, protein–glycosaminoglycan conjugates, nano-glycosaminoglycan composites and polymer–glycosaminoglycan complexes.