Table 2.
List of the main labeled NGF (nerve growth factor) derivatives reported in literature.
| NGF Labeling Strategy | Ratio of Probes Per NGF Molecule | Cellular Model Testing NGF Activity | References |
|---|---|---|---|
| 125I-NGF | n.d. | Sympathetic neurons | [115] |
| Biotinylated NGF (NGF-b) | ~3 biotin molecules per NGF subunit | PC12 | [119] |
| NGF-b/Streptavidin Alexa647 | ~9 biotins per NGF molecule; 20 nM NGF-b is given to the cells and further detected with Streptavidin Alexa647 | PC12 and PC12nnr5 | [120] |
| NGF-b/streptavidin Qdot | ≤3 biotins per NGF subunit; NGF-b is conjugated to streptavidin-Qdot at a molar ratio of 1 NGF:1 Qdot | PC12 | [121,122] |
| ~1 biotin was bound per NGF molecule; 2nM NGF-b is given to the cells and further detected with 50–500 pM streptavidin-coated Qdot | Differentiated PC12 | [123] | |
| ~3 biotins per NGF dimer; NGF-b is conjugated to streptavidin-Qdot at a molar ratio of 1 NGF:1 Qdot | Rat DRG neurons | [83] | |
| Cy3-NGF or Cy3.5-NGF | ~1.0–1.1 ratio between fluorophore and NGF | Chick embryonic DRG neurons; PC12 | [124,125,126] |
| Mono-biotinylated NGF via chemical tag | AVI-tag fused at NGF C-terminus; NGF-b is obtained transfecting the construct in HEK293FT cells together with the biotinylating BirA enzyme; NGF-b is conjugated to streptavidin-Qdot at a molar ratio of 1 NGF:1 QD | Rat DRG neurons | [127] |
| A4-tag fused at NGF C-terminus; NGF-b is obtained by labeling the purified protein with CoenzymeA-biotin substrates and PPTase enzyme | PC12 | [128] |
Qdot: quantum-dot.