Table 1.
Comparison of 2D diffusive behaviour for OMPs determined using different SPT methods
| Proteina (E. coli strain or PSM) |
SPT methodb (imaging rate) |
SPT probec | Brownian diffusion (MSD = 4Dt) |
Anomalous subdiffusion (MSD = 4Dtα) |
Reference | |
|---|---|---|---|---|---|---|
|
D (μm2/s) |
Confinement diameter (μm) |
Exponentf (α) |
||||
| LamBbiotin (S2188:pLO16) |
BFM (25 Hz) | 0.53 μm SA-PS bead held in optical tweezers | 0.15 | 0.03 | NR | [13•] |
| LamBAu-BE (lamB–) |
DICM (1 Hz) | 20 nm colloidal gold | NRd | NRe, < 0.2 | NR | [14] |
| LamBAu-BE (lamB+) |
DICM (1 Hz) | 20 nm colloidal gold | NRd | NRe, < 0.2 | NR | [14] |
| LamB (LE392) |
FM (30 Hz) | eYFP-λ phage particle | 0.059 | NR, < 0.4 | 0.3 | [15] |
| LamBbiotin (lamB–) |
FM (30 Hz) | SA–Qdot | 0.058 | NR, < 0.4 | NR | [15] |
| BtuB (K17) |
FM (40 Hz) | AF555Antibody | 0.05 | NR | 0.56 | [16] |
| BtuB (K17) |
FM (40 Hz) | OG488Colicin E3 | 0.1 | NR | 0.75 | [16] |
| BtuBTonBboxmutant (btuB–) |
FM (40 Hz) | AF555Antibody | 0.27 | NR | 0.56 | [16] |
| BtuB (JM83) |
FM (30 Hz) | AF488Colicin E9S-S | 0.013 | 0.6 | 0.53 | [12••] |
| BtuB (PSM BtuB1000x) |
FM (30 Hz) | ™RColicin E9S-S | 0.013 | 0.6 | 0.34 | [12••] |
| BtuB (PSM BtuB1x:OmpF1000x) |
FM (30 Hz) | ™RColicin E9S-S | 0.012 | 0.6 | 0.51 | [12••] |
| BtuB (JM83) |
FM (56 Hz) | AF488Colicin E9S-S | 0.025 (N = 54) |
0.5 | 0.62 | unpublished |
| BtuB (JM83) |
FM (30 Hz) | AF488Δ1-52Colicin E9S-S | 0.0081 | 0.5 | 0.64 | [12••] |
| BtuB (BZB1107) |
FM (30 Hz) | AF488Colicin E9S-S | 0.018 | 0.5 | 0.11 | [12••] |
| Cir (JM83) |
FM (30 Hz) | AF488Colicin IaS-S | 0.019 | 0.6 | 0.20 | [12••] |
| Cir (BZB1107) |
FM (30 Hz) | AF488Colicin IaS-S | 0.011 | 0.5 | 0.86 | [12••] |
| OmpF (K17) |
FM (40 Hz) | AF555Antibody | 0.006 | 0.1 | 0.14 | [16] |
Au-BE denotes gold-binding epitope. PSM denotes in vitro polymer-supported membrane containing reconstituted BtuB and/or OmpF (see [12••] for experimental details).
BFM denotes bright-field microscopy. DICM denotes differential interference contrast microscopy. FM denotes fluorescence microscopy.
AF488, AF555, OG488 and TMR denote the following fluorescent dyes (respectively): Alexa Fluor 488, Alexa Fluor 555, Oregon Green 488 and tetramethyl rhodamine. S–S denotes disulphide top-lock in R-domain to prevent colicin translocation across the bacterial outer membrane.
Motion of colloidal gold was tracked for 5 min at 1 Hz. Immobile (20–50 nm displacement) and somewhat mobile (100–300 nm displacement) particles were observed in both the presence and absence of wild-type LamB.
Confinement diameter was estimated from the asymptotic MSD value at 10 s. This parameter was not reported in Ref. [14].
This exponent term (α) describes the non-linear scaling of the MSD in time, with α < 1 indicating anomalous subdiffusion and α = 1 indicating normal Brownian diffusion.