Table 3.
Forces reported to be generated by single integrins on extracellular ligands. RGD and cRGD are linear or cyclic peptides containing the integrin ligand RGD. FNIII9-10 is the two-domain protein segment that is the natural ligand for α5ß1 integrin.
| Ligand | Force per integrin, pN | comments | Force sensor | reference |
|---|---|---|---|---|
| cRGD | 1 | Range 1–15 pN | FRET unquench; PEG-82 wlc | Liu…Salaita 2013 [31] |
| cRGD, RGD | ~15 | Sensors crowded, 10 nm apart, maybe few are engaged | FRET unquench; PEG-24 wlc | Chang…Salaita 2016 [32] |
| RGD, cRGD | > 4.7, > 13 | Only ~10% of sensors over FA were engaged | FRET unquench; DNA zipper hairpin | Zhang…Salaita 2014 [33] |
| RGD FNIII9-10 | 36, 110 | 36 pN from I27 unfolding 110 from S-S reduction | FRET unquench; unfold I27 | Galior…Salaita 2015 **[34] |
| RGD | > 6, > 17 | Fraction of sensors engaged not deter-mined, may be small | FRET unquench; DNA zipper hairpin | Blakeley…Chen 2014 [35] |
| RGD | 40 | Before FA formation, 5–30 min | DNA zipper-release | Wang and Ha 2013 [36] |
| cRGD | > 54 | Within established FA, 2 hr | DNA zipper-release | Wang…Ha 2015 [37] |
| RGD | 2 | Sensors 25 nm apart, 90% of sensors in FA were engaged | FRET index/efficiency; peptide wlc | Morimatsu…Dunn 2013 **[30] |
| RGD FNIII9-10 | 1–3 (60–80%) 3–7 (20–30%) >7 (10%) | Single molecule FRET distinguishes sensors engaged | FRET efficiency; peptide wlc | Chang…Dunn 2016 **[38] |