Frequently Asked Questions
Technical support with product storage and handling conditions and procedures; product specification and data.
How does Creative PEGWorks ship your products?
All of our products are shipped at room temperature for overnight delivery in the US. International shipments should take 3-5 days depending on the continent and it typically takes three days to deliver to destinations in European countries. Our choice of carrier is FedEx. Shipping cost will be prepaid and added to invoice unless the customer provides a valid FedEx or UPS account number.
What are the storage conditions for your products?
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.
What procedure does Creative PEGWorks recommend to aliquot/rebottle your products?
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.
How can I request a copy of SDS or COA for your products?
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.
What is the difference between monodispersed PEG and polydispersed PEG?
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.
What is mPEG?
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.
What is the difference between homobifunctional PEG and heterobifunctional PEG?
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.
What is PEGylation?
PEGylation is a chemistry process to covalently attach PEG polymers to a substrate including molecules, macromolecules, biologics, polymers, dendrimers, particles, surfaces etc.
What types of multi-arm PEG do you offer?
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).
What is the definition for Labeling Degree (%) of your fluorescently-labeled polysaccharide products?
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.
What success has PEGylation achieved on the market?
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.
What solvents can PEG be dissolved in?
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.
What PEG products are particularly sensitive to light or oxygen?
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.
I need a special PEG reagent that cannot be found in your online catalog. Can you custom synthesize it?
Do you provide protocols or procedures for the use of your products?
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.
Which products do you recommend for my applications?
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.
What are the differences among your PEG NHS ester products?
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.
|PEG NHS esters||Structural characteristics||Amine reactivity||Stability|
|Type A: SCM||Methylene (CH2) linkage between PEG and NHS ester||Highly reactive||Hydrolysis half-life: less than five minutes. It often requires the use of a large excess of PEG reagents.|
|Type B: SG||C4 aliphatic ester linkage between PEG and NHS ester||Very reactive||Hydrolysis half-life: around 20 minutes.|
|Type C: SS||C3 aliphatic ester linkage between PEG and NHS ester||Very reactive||Hydrolysis half-life: around 10 minutes.|
|Type D: GAS||C4 aliphatic amide linkage between PEG and NHS ester||Very reactive||Hydrolysis half-life: around 20 minutes.|
|Type E: SAS||C3 aliphatic amide linkage between PEG and NHS ester||Very reactive||Hydrolysis half-life: around 10 minutes.|
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.
|PEG acids||Structural characteristics|
|Type A: AA||Methylene (CH2) linkage between PEG and acid (COOH)|
|Type B: GA||C4 aliphatic ester linkage between PEG and acid (COOH)|
|Type C: SA||C3 aliphatic ester linkage between PEG and acid (COOH)|
|Type D: GAA||C4 aliphatic amide linkage between PEG and acid (COOH)|
|Type E: SAA||C3 aliphatic amide linkage between PEG and acid (COOH)|
AA: Acetic Acid, also called CM – Carboxyl Methyl; GA: Glutaric Acid; SA: Succinic Acid; GAA: Glutaramide Acid; SAS: Succinamide Acid
Disclaimer: The information abovementioned serves only as a general guide for selecting PEGylation reagents or providing general information for the convenience of our customers. Please refer to publications for detailed and specific PEGylation procedures. Creative PEGWorks assumes no liability for the information provided within this web page.