Product number 10994, Fmoc-N-amido-dPEG®4-NHS ester, is one of Quanta BioDesign’s peptide synthesis products. This product is activated with an N-hydroxysuccinimidyl (NHS) ester for direct conjugation to a peptide chain. The 17 atom, 18.1 Å, dPEG® spacer allows the introduction of a short, hydrophilic spacer into a peptide chain. The Fmoc protecting group on the N-terminus of the molecule cleaves easily with standard peptide chemistry.
PEGylation and dPEG® Products
PEGylation refers to the covalent addition of polyethylene glycol (PEG) to a compound or surface. PEGylated compounds include proteins, peptides, dyes or other labels, and small molecule drugs. Peptide synthesis frequently employs PEGylation to enhance the solubility of the peptide, because the amphiphilic character of PEG imparts tremendous water solubility to peptides. Moreover, peptide PEGylation prolongs in vivo circulation of peptide conjugates by both increasing the peptide’s hydrodynamic volume and protecting the peptide from proteolysis. Additionally, PEGylation reduces or eliminates the antigenicity of the conjugated peptide.
However, traditional PEG products are dispersed polymers (Đ > 1.00). A traditional PEG consists of multiple chain lengths, each with different molecular weights. The stated molecular weight for a conventional PEG indicates an average of the distribution of chain lengths and molecular weights.
Quanta BioDesign’s single molecular weight PEG products (known as “discrete PEG” and sold under the dPEG® trademark) provide all of the benefits of traditional, dispersed PEG without the analytical headache that comes from having an intractable mixture of conjugates, each with different PEG chain lengths. For a thorough discussion of dPEG® technology, please see our “What is dPEG®?” page. For answers to the questions that we are most often asked, please visit our page “Frequently Asked Questions (about dPEG® products).”
Using Fmoc-N-amido-dPEG®4-NHS ester
Fmoc-N-amido-dPEG®4-NHS ester permits our customers to insert a short dPEG® spacer into a peptide chain using standard Fmoc chemistry. The product works equally well in solid-phase and solution-phase synthetic processes. The dPEG® linker attaches at the N-terminal end of the peptide chain. Additional peptide synthesis can be carried out to extend the peptide further, creating a peptide with a flexible linker or spacer in the middle. Also, the dPEG® chain can provide spacing in a synthetic construct where steric hindrance is a problem. The amphiphilic nature of dPEG® means that the construct gains water solubility while remaining soluble in an organic solvent. The Fmoc protecting group removes easily with a solution of piperidine in N, N-dimethylformamide (DMF).
Tetrafluorophenyl (TFP) esters are generally superior to the more commonly used NHS esters. The 2,3,5,6-tetrafluorophenyl group is more stable to hydrolysis than NHS esters. Also, TFP esters are more reactive to amines than NHS esters. The optimum pH for NHS esters is 7.0 – 7.5, while the optimum pH for TFP esters is 7.5 – 8.0. NHS esters are more popular than TFP esters because they are familiar, well-understood reagents. Quanta BioDesign has additional information on why TFP esters are superior to NHS esters on our website.
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