Reagents

thumb|Reagents, such as sulfur (pictured), are the starting materials used in chemical reactions.

chemical compound

'''N-Ethylmaleimide (NEM''') is an organic compound that is derived from maleic acid. It is a unstable substance that reacts rapidly with thiols and is commonly used to modify cysteine residues in proteins and peptides.

X-Gluc is a chemical compound with the molecular formula C14H13BrClNO7. It is used as a reagent to detect β-glucuronidase, an enzyme produced by the E. coli bacterium. It is used to detect E. coli contamination in food, water and the urinary tract. In addition, it is widely used in molecular biology experiments to mark and select the expression of target genes (GUS reporter system).