FITC-PEG-SH is a linear bifunctional PEG reagent with a fluorescein dye. Fluorescein often called FITC is a common fluorescent tracer in biology for staining cells, tissues, biomarkers or nanoparticles. It has peak absorption or excitation at 494 nm and maximum emission at 521 nm. Fluorescent PEG is common for PEGylation to label or tag biomolecules and nanoparticles with dye and tracer. It has a reactive free thiol, SH, cysteine, sulfhydryl, or mercapto group that selectively reacts with maleimide and novel metal surface including gold, silver, etc.. It is useful for reversible PEGylation. Rhodamine or other dyes including NIR dyes labeled PEG-SH is available through custom synthesis.
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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