Table 2. Properties of Various SM-PEGn Linkers from Different Suppliersa.
| linker | physical appearance | MW from supplier | MW by mass spectrometryb | purity by RP-HPLC | purity by qNMR | maleimide reactivity | NHS release T50c |
|---|---|---|---|---|---|---|---|
| SM-PEG6 | viscous, pasty | 601.6 | 601.0 | 100% | 97–99% | ND | 26 min |
| SM-PEG24 | viscous, pasty | 1395.0 | 1395.0 | 97% | 94–100% | 100% | 34 min |
| SM-PEG45 | powder, white | 2294.0 | 2324.0 | ND | 100% | 64% | 6 min |
| SM-PEG70 | powder, white | 3380.0 | 3601.0 | ND | 97% | 87% | ND |
a
SM-PEG6 and SM-PEG24 from Thermo/Quanta (supplier A) SM-PEG45 from NOF Corp. (supplier B) and SM-PEG70 from Nanocs (supplier C).
b
Mass spectrometry performed by HT Laboratories Inc., San Diego, CA.
c
Release rate of 50% of total NHS present in the linker reagent. (ND = not determined).