PEG&多糖系列产品储存和使用须知 PEG & Polysaccharide Products Storage & Usage Instructions

Q: What are the storage conditions for PEG products?

A: PEG products could be sensitive to temperature, light or moisture. They should be stored in a freezer of -15°C or colder immediately upon arrival. PEG 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.

Q: What procedure is recommended to aliquot/rebottle PEG products?

A: 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.

Q: What is the difference between monodispersed PEG and polydispersed PEG?

A: 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.

Q: What is mPEG?

A: 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.

Q: What is the difference between homobifunctional PEG and heterobifunctional PEG?

A: 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.

Q: What is PEGylation?

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

Q: What is the definition for Labeling Degree (%) of the fluorescently-labeled polysaccharide products?

A: 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.

Q: What success has PEGylation achieved on the market?

A: 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.

Q: What solvents can PEG be dissolved in?

A: 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.

Q: What PEG products are particularly sensitive to light or oxygen?

A: 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.