Biomolecules, modification

Synthetic organic chemistry has provided countless powerful and elegant strategies for the construction of complex natural products. Generally, the reactions used for this purpose arise from the systematic optimization of reaction parameters, such as solvent, temperature, concentration, and protecting groups, until the desired reactivity and selectivity are achieved. In sharp contrast, reactions for biomolecule modification cannot be developed with this flexibility because they must be carried out under a narrow set of conditions to maintain the properly folded structure of the protein substrates. Ideally, they should proceed in aqueous solution within a pH range of 6-8,... 

Xu, W.Z., Zhang, X., Kadla, J.F. Design of functionalized cellulosic honeycomb films site-specific biomolecule modification via click chemistry . Biomacromolecules 13, 350-357... 

Scheme 9.30 (a) The strain-promoted azide-alkyne [3-1-2] cycloaddition (SPAAC) as developed by Wittig and Krebs and reintroduced/reexploited by Bertozzi and co orkers in 2004 [76, 77]. (b) The biotinylated cyclooctene analog for selective biomolecule modification studies [76]. 

In this chapter we describe the basic principles involved in the controlled production and modification of two-dimensional protein crystals. These are synthesized in nature as the outermost cell surface layer (S-layer) of prokaryotic organisms and have been successfully applied as basic building blocks in a biomolecular construction kit. Most importantly, the constituent subunits of the S-layer lattices have the capability to recrystallize into iso-porous closed monolayers in suspension, at liquid-surface interfaces, on lipid films, on liposomes, and on solid supports (e.g., silicon wafers, metals, and polymers). The self-assembled monomolecular lattices have been utilized for the immobilization of functional biomolecules in an ordered fashion and for their controlled confinement in defined areas of nanometer dimension. Thus, S-layers fulfill key requirements for the development of new supramolecular materials and enable the design of a broad spectrum of nanoscale devices, as required in molecular nanotechnology, nanobiotechnology, and biomimetics [1-3]. 

Recent developments in DNA/RNA chemical synthesis have allowed us to attach some functional groups covalently to nucleic acids, thus permitting the introduction of a functionality or properties not normally present in the native biomolecule The use of non-nucleosidic linkers is probably the most popular approach for the 5 -terminal modification of chemically synthesized nucleic acid oligonucleotides and a number of such linkers are commercially available. The linker shown in Fig. 2 is designed as a phosphoramidate derivative so that it can be incorporated into the 5 -terminus of the sequence as the last... 

The dansyl derivative 9-azidononyl-5-(dimethylamino)naphthalene-l-sulfonate 35 was used by Yi and collaborators [91] as an azido-fluorescent label in a tandem method of sulfonium alkylation and click chemistry for the modification of biomolecules. Fluorescent labeling of a protein was successfully carried out after simple incubation of BSA with sulfonium salt 36 followed by azido-containing fluorophore 35, at room temperature. 

Wachtershauser provides a detailed discussion of whether particular crystal modifications of pyrite could have led to homochirality in the biomolecules produced, but his theory appears to be extremely speculative. 

Nanoparticle surface modification is of tremendous importance to prevent nanoparticle aggregation prior to injection, decrease the toxicity, and increase the solubility and the biocompatibility in a living system [20]. Imaging studies in mice clearly show that QD surface coatings alter the disposition and pharmacokinetic properties of the nanoparticles. The key factors in surface modifications include the use of proper solvents and chemicals or biomolecules used for the attachment of the drug, targeting ligands, proteins, peptides, nucleic acids etc. for their site-specific biomedical applications. The functionalized or capped nanoparticles should be preferably dispersible in aqueous media. 

Other than the epoxy groups available on one Priostar dendrimer type and a methyl ester available on a PAMAM dendrimer, the commercial suppliers generally don t offer a selection of spontaneously reactive dendrimers for bioconjugation purposes. For this reason, most of the applications published for coupling biomolecules to dendrimers have used various modification or activation steps to create the appropriate reactive groups for conjugation (e.g., Leon etal., 1996). 

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