HO-PEG-COOH is a linear heterobifunctional PEG derivative with one hydroxyl group and one carboxyl group. It is a useful cross-linking reagent with a PEG spacer. There is a methylene (CH2) linkage between PEG and COOH, often called AA (acetic acid) or CM (carboxyl methyl). Heterobifunctional PEG products with other carboxylic acid such as GA (glutaric acid), SA (succinic acid), GAA (glutaramide acid), and SAA (succinamide acid) may be offered through our custom synthesis service. It is also a useful monofunctional acid PEG reagent with a terminal hydroxyl group instead of methoxy as in mPEG-Acid. Hydroxyl terminated PEG has reported to have different immune responses such as antibody generation to methoxy-terminated PEG as in mPEG.
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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