Description
Fmoc-NH-PEG-SCM is a linear heterobifunctional PEG reagent with Fmoc protected amine and activated carboxylic acid NHS ester. SCM stands for succinimidyl carboxyl methyl ester and is one type of NHS esters. It is a useful crosslinking reagent with a PEG spacer. Heterobifunctional PEG derivative with other types of NHS ester may be available through custom synthesis. These NH esters may include succinimidyl glutarate (SG), succinimidyl succinate (SS), glutaramide succinimidyl (GAS) and succinamide succinimidyl (SAS).
The fluorenylmethoxycarbonyl (Fmoc) is a base-labile protecting group in organic synthesis and peptide synthesis. Fmoc deprotection typically occurs after the SCM has reacted. A common deprotection method is: 20% piperidine in dimethylformamide (DMF). Fmoc group has an approximate half life of 6 seconds in this solution, per  "Greene's Protective Groups in Organic Synthesis"; DOI: 10.1002/9780470053485.
Properties
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.
References
1. Polyelectrolyte Nanogels Decorated with Monoclonal Antibody for Targeted Drug Delivery, React Funct Polym. 2011 March 1; 71(3): 315, 323) , Â Text.
2. Crosslinking Biotin to Small Molecule Drug – A prodrug nanoassembly entrapping drugs as a tumor-targeted delivery system, Chem. Commun., 2013, 49, 801-803, Â Text.
3. Â Deep tumor penetration of drug-loaded nanoparticles by click reaction-assisted immune cell targeting strategy, J. Am. Chem. Soc. 2019, doi: Â 10.1021/jacs.9b04621
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