FAQ

Our products could be sensitive to temperature, light or moisture. They should be stored in a freezer of -15°C or colder immediately upon arrival. Our products are in dry powder form except those having very low molecular weight. Vials should be kept away from light particularly UV light. Before vials can be opened, please allow vials and products to equilibrate to room temperature to avoid absorbing moisture. For long term storage, we recommend that our products are stored as a dry powder form and not in any type of solutions. If you have to store products in a solution, be sure that the solvent is degassed and dried.

1) Allow vials and products to thaw and equilibrate to room temperature;
2) Glove box or any other dry packaging areas with access to inert gas (e.g. argon or nitrogen) should be used to aliquot and rebottle;
3) Open vials and quickly repackage;
4) Flush all vials with argon or nitrogen – caution: adjust gas flow so that dry powders will not be blown away;
5) Tightly cap all vials and wrap with parafilm; 6) Store at or below -15°C.

COA and SDS are shipped together with your order. However if you cannot locate SDS, COA or storage instructions in the package you received, please click Contact Us to submit a request.

Monodispersed PEG refers to PEG with a precise, discrete molecular weight (i.e. its molecular weight is a fixed value not a range). It is a pure compound with an exact molecular formula. Polydispersed PEG refers to PEG with its molecular weight distributed in a range. Often polydispersity index (PDI) is used to determine how narrow the molecular weight distribution is.

mPEG refers to methoxylpolyethylene glycol or polyethylene glycol monomethyl ether. mPEG derivatives refer to monofunctional linear PEG derivatives with a general formula of mPEG-X that has an inert methoxyl cap at one end and a functional group X at the other end of the PEG polymer chain.

Homobifunctional PEG with a general formula X-PEG-X has the same functional group at both terminals of the linear PEG chain; while heterobifunctional PEG (X-PEG-Y) derivatives have two different functional groups.

PEGylation is a chemistry process to covalently attach PEG polymers to a substrate including molecules, macromolecules, biologics, polymers, dendrimers, particles, surfaces etc.

We offer 4-arm and 8-arm PEG derivatives. The molecular weight (MW) of our multi-arm PEG products refers to the molecular weight of the entire molecule, and the molecule weight of each arm can be calculated by dividing the indicated MW by the indicated number of arms. For example, the average MW of each arm for our 4-Arm PEG-Amine, MW 10,000 is 2,500 (10,000/4).

Labeling Degree (%) is determined by dividing the number of covalently conjugated fluorescent dye or biotin molecules by the total number of monomeric units of a polysaccharide molecule chain. For instance, 1.0 MOL % labeling means that one of every one hundred monomeric units along the polysaccharide chain is fluorescently labeled.

There are currently about one dozen of PEGylated pharmaceuticals on the market with FDA approval. These products include PEGylated enzymes, monoclonal antibodies, glycoproteins, cytokines, human growth hormones, aptamers, synthetic peptides, and liposomes.

PEG products are very soluble in water and aqueous buffer solutions typically with solubility up to several hundred milligrams per milliliter (mg/mL). PEG products are also very soluble in a variety of organic solvents including dichloromethane, chloroform, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) etc, and could also be dissolved in alcohol (methanol, ethanol, isopropanol), toluene, and tetrahydrofuran (THF) when heated. DMF and DMSO could be used to prepare stock solutions of PEG reagents that consist of water sensitive functional groups for dilution with or mixed with aqueous buffer to conduct experiments that require the use of aqueous based solvents.

PEG products that contain unsaturated carbon-carbon bonds or bonds prone to be oxidized should be stored away from light and air. These products include PEG-acrylate, PEG-acrylamide, PEG-maleimide, PEG-thiol, fluorescent PEG etc. Under strong light illumination or exposure to air, they could polymerize to form insoluble gels or lose their reactivity or function.

We provide custom synthesis service for PEG and other polymers with a variety of functional groups and a broad range of molecular weights. Please visit the Custom Synthesis Service page to learn more and Contact Us for a quote.

We do not provide detailed protocols or procedures for the uses of our products because they can be used in very different experiments that often require tailored conditions. However, we have collected several dozens of published papers that describe the use of our products with experimental details. Please visit the PEGylation Literature page and select suitable publications as references.

Please contact us and we can provide technical assistance for the selection of products to meet your specifications. You may also visit PEGylation Chemistry page to learn more about PEGylation chemistry.

We offer a variety of PEG acid and PEG NHS ester. These NHS esters react with primary and secondary amine to form a stable amide linkage. This reaction may be carried out in an organic solution with an organic base or may be carried out in an aqueous solution at or around neutral pH or slightly acidic or basic. To PEGylate proteins or nanoparticles, it often requires a large excess of PEG NHS esters due to the competitive hydrolysis reaction in an aqueous solution. Stability of NHS esters is compared by their hydrolysis half-life (T1/2). To mitigate the competitive hydrolysis reaction, organic solvents such as amine-free, anhydrous DMF and DMSO may be used in combination with an aqueous buffer solution.

SCM: Succinimidyl Carboxyl Methyl ester; SG: Succinimidyl Glutarate ester; SS: Succinimidyl Succinate ester; GAS: Glutaramide Succinimidyl ester; SAS: Succinamide Succinimidyl ester. Note: hydrolysis half-life depends on pH, temperature and other factors of the testing conditions.

AA: Acetic Acid, also called CM – Carboxyl Methyl; GA: Glutaric Acid; SA: Succinic Acid; GAA: Glutaramide Acid; SAS: Succinamide Acid