Figure 1: Reactive α,β-dicarbonyl-induced glycation damage in cells. Glycation by α,β-dicarbonyls like methylglyoxal and glyoxal affects all classes of biological macromolecules. Proteins, in particular arginine, lysine, and cysteine residues, are highly susceptible to glycation, forming protein cross-links and various AGE adducts, examples of which are shown here. Of these, the most important protein-AGEs quantitatively are arginine-derived hydroimidazolones, especially MG-H1. Formation of protein AGEs alters protein structure and function, leading to biochemical dysfunction. Nucleotides and lipids may also undergo glycation, with deoxyguanosine and basic phospholipids being particularly vulnerable. Consequences of nucleotide and lipid glycation damage are increased DNA mutations and compromised lipid membrane integrity, respectively. Within mitochondria, it is expected that glycation affects matrix and membrane proteins, phospholipids on the outer and inner mitochondrial membranes and mtDNA.