Introduction:  

Propyl ether-PEG3-Propyl ether is a reagent with an extended spacer arm. This reagent is soluble in organic solvents such as DMSO or DMF. Once dissolved in an organic solvent, the reagent is further diluted in a non-amine containing aqueous buffer. NHS esters react efficiently with primary amino groups (-NH2) in pH 7-9 buffers to form stable amide bonds. Because antibodies and other proteins generally contain multiple lysine (K) residues in addition to the N-terminus of each polypeptide, they have multiple primary amines available as targets for labeling with NHS-activated PEG reagents.

Important Product Information:

Propyl ether-PEG3-Propyl ether is moisture-sensitive. Store the vial of the reagent at -20°C with desiccant. To avoid moisture condensation onto the product, equilibrate vial to room temperature before opening.

Dissolve NHS-PEG-linker immediately before use. The NHS-ester moiety readily hydrolyzes and becomes non-reactive; therefore, weigh and dissolve only a small amount of the reagent at a time and do not prepare stock solutions for storage. Discard any unused reconstituted reagent.

? Avoid buffers containing primary amines (e.g., Tris or glycine) as these compete with the intended reaction. If necessary, dialyze or otherwise desalt to exchange the protein sample into an amine-free buffer such as phosphate buffered saline.