mPEG-Dansyl is a stable blue or green fluorescent sulfonamide adduct between mPEG-amine and dansyl chloride (DNSC) through the formation of dansyl amide. Dansyl is a relatively lipophilic or hydrophobic dye particularly at high pH. The dansyl group is highly fluorescent, and it has a very high Stokes Shift. The excitation maximum (ca 350 nm) is essentially independent on the medium, whereas the emission maximum strongly depends on the solvent and varies from 520 to 550 nm, giving blue or green emission depending on the solvent.
Molecular weight: MW of PEG was measured by MALDI-MS or GPC. PDI (polydispersity index) of our linear PEG is 1.02-1.05 with very narrow MW distribution. The number of repeating ethylene oxide units (CH2CH2O) or the degree of polymerization is calculated dividing the PEG MW by 44 (44 is the molecular mass of one repeating unit).
Solubility: Soluble in water and aqueous buffer, chloroform, methylene chloride, DMF, DMSO, and less soluble in alcohol, toluene. Not soluble in ether.
Density: PEG density is approximately 1.125 g/mL
Physical form: PEG products generally appear as white or off-white powder, and for very low MW linear PEG such as MW 1k or less, it may appear as wax-like, semi-solid material due to the low MW and the type of functional groups.
Storage condition: PEG product shall be stored in the original form as received in a freezer at -20C or lower for long term storage. Stock solution of PEG reagents that do not contain oxygen or moisture sensitive functional groups may be temporarily stored in a refrigerator or ambient temperature for multiple days. Stock solution should avoid repeated freeze-and-thaw cycles. See Documents section for detailed storage and handling conditions.
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