Biomolecules, modification carbohydrates

Specific groups involved in covalent immobilization of biomolecules to the surface are very often introduced into the structure of this molecule, especially in oligonucleotides and carbohydrates. Carboxylic and amino functionalities are the modifications most frequently used, although aldehyde, thiol, and oxyamino are useful alternatives. In some cases coupling molecules (cross-linkers) are necessary to increase the affinity (or reactivity) of the interacting groups. 

Abstract This review provides an overview of some of the more recent work directed to exploit radical-based chemistry for the modification of some of Natures most important biomolecules, such as amino acids, peptides, and carbohydrates. Radical reactions are particularly advantageous for carrying out a variety of structural modifications on biomolecules as the reaction conditions are typically compatible with a wide variety of functional groups and solvents. An array of effective synthetic transformations will he discussed including selective side chain and backbone modifications of amino acids and peptides, along with methods for the transformation of carbohydrate substituents, as well as fragmentation and cyclizations reactions for the preparation of either structurally modified carbohydrates or chiral building blocks. 

Despite the proven occurrence of relatively large quantities of D-fructosamine derivatives in some common dehydrated foods, such as tomato or milk powders, no official or even recommended methods for their routine analysis in foods have thus far been offered. The situation is somewhat better with the fructosamine assay introduced into clinical practice however, the assay is not particularly selective and evaluates total fructosamine modification on circulating proteins, peptides, and other biomolecules combined. Difficulties with development of universal, fast, and reliable analytical methods for fiuctosamine derivatives originate Irom the chemical nature of this carbohydrate structure, which is unstable at elevated temperatures and in the presence of nucleophilic and oxidation agents. It does not absorb appreciably in the UV-Vis range, is highly hydrophilic, and is not readily modified into analytically useful derivatives. 

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