Plasmon Resonance Energy Transfer Nanoruler for Pinpointing Molecular Distance and Interaction on the Living Cell Membrane

Abstract

Developing novel strategies to measure nanoscale distance and molecular interaction on a living cell membrane is of great significance but challenging. Here we develop a model of a linker-free plasmon resonance energy transfer, termed "PRET nanoruler", which is composed of a single-sized nanogold-antibody conjugates donor (G 26 @antiCD71) and a fluorophore-labeled XQ-2d aptamer receptor (XQ-2d-Cy3), that produces a separation distance (r) dependent energy transfer (η PRET ). Both the theoretical finite element simulation and experiments evidence the observable PRET between single G 26 NPs and XQ-2d-Cy3. Regardless of the size of η PRET , we could confirm r is less than 5 nm, the separation of two binding sites is in the range of 13.0−18.0 nm. There is a competitive binding of Tf and XQ-2d-Cy3 on CD71 receptors. PRET nanoruler realizes the estimation of the nanoscale separation distance, and determines the molecular interaction and competitive binding. It is an alternative tool for observing nanoscale single molecular events in the future.

Single-Nucleobase-Resolved Nanoruler Determines the Surface Energy Transfer Radius on the Living Cell Membrane

“…As reported, R is 16.3 nm and d antiCD71 is 5.2 nm, according to eqs and ; using the triangle Pythagorean theorem, we could easily obtain the r 0TA value for different sizes of AuNP and FAM pairs. Also, according to the report, the length of each base pair is about 0.43 nm, which means that with the addition of each base, the FAM dye that is labeled on XQ-2d may move 0.43 nm toward the AuNP surface when the angular deviation is not considered. At this moment, we could calculate the r value of 1TA, 2TA, and 3TA, i.e., r 1TA , r 2TA , and r 3TA , respectively.…”

“…In detail, according to the definition of r 0 , when r and Φ are known, we can obtain the concrete value of r 0 . The r can be calculated by the triangle Pythagorean theorem according to our previously reported method R 2 = r 2 − d 2 d = r AuNP + d antiCD 71 where R is the distance between XQ-2d and antiCD71 binding sites on the CD71 receptor on the PL45 cell membrane, which has been estimated to be 16.3 nm by a plasmon resonance energy transfer nanoruler …”

“…For example, when using the NSET as a nanoruler to measure the separation among two binding sites of ligands, the r 0 value is considered a constant that could be 2–8 nm for a series of different sizes of AuNP . When using the NSET model to project the three-dimensional (3D) conformation of aptamer at its binding sites, we considered the r 0 value to be 13 nm for AuNP with a diameter of 5 nm (Au 5 ) and the FAM dye pair. , Still, of course, different sizes of AuNP and dye pairs possessed different r 0 values.…”

Temperature-sensitive metal-enhanced fluorescence and plasmon resonance energy transfer

“…In addition, the PRET is considered a reversible process of the NSET 9 and has been reported to sense molecular events within a distance between the donor and acceptor below 5 nm. 10 The occurrence of the MEF effect has also been reported to strictly depend on separation distances of 7–8 nm between a nanometal and a fluorophore. 11 Notably, the spectral overlap between a donor and an acceptor is considered one of the key parameters for PRET and MEF.…”