Bifunctional 8-Arm PEG reagents have two functional groups X/Y with 1:7, 2:6, 4:4 , 6:2, 7:1 ratios. We started offering this series of special reagents as customs synthesis with the following combinations. We are also listing some of these reagents as regular catalog products that are ready to ship overnight. 8-Arm PEG-X/Y is prepared using our proprietary chemistry resulting in precisely controlled ratios.
We offer five different ratios for each pair of functional groups. 1:7, 2:6, 4:4, 6:2, 7:1. Other ratios may be also offered. An example is listed below.
Amine(1)/Acid(7) - 1 amine group and 7 acid groups,
Amine(4)/Acid(4) - 4 amine groups and 4 acid groups,
Amine(7)/Acid(1) - 7 amine groups and 1 acid group.
Other pairs of functional groups include:
Molecular weight: 8-Arm PEG MW refers to the MW of the entire PEG molecule. The MW of each arm is 1/8 of the MW indicated in the product name. MW of PEG was measured by MALDI-MS or GPC. PDI (polydispersity index) of our 8-Arm PEG is 1.02-1.06 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 certain special 8-arm PEGs, it may appear as wax-like, semi-solid material due to 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.