Optimization of Xenon Biosensors for Detection of Protein Interactions

Abstract

Hyperpolarized129 Xe NMR can detect the presence of specific lowconcentration biomolecular analytes by means of the xenon biosensor, which consists of a water-soluble, targeted cryptophane-A cage that encapsulates xenon. In this work we use the prototypical biotinylated xenon biosensor to determine the relationship between the molecular composition of the xenon biosensor and the characteristics of protein-bound resonances.The effects of diastereomer overlap, dipole-dipole coupling, chemical shift anisotropy, xenon exchange, and biosensor conformational exchange on protein-bound biosensor signal were assessed. It was found that optimal protein-bound biosensor signal can be obtained by minimizing the number of biosensor diastereomers and using a flexible linker of appropriate length.Both the linewidth and sensitivity of chemical shift to protein binding of the xenon biosensor were found to be inversely proportional to linker length.

Temperature‐Controlled Molecular Depolarization Gates in Nuclear Magnetic Resonance

“…When using temperature to control depolarization transfer, three effects should be considered: First, increasing temperature increases the exchange rate of xenon with the cage molecules (6,9,10). Second, the binding constant of the cage-xenon complex tends to increase as temperature increases (11), making more xenon susceptible to selective saturation.…”

Sensitivity enhancement by exchange mediated magnetization transfer of the xenon biosensor signal

“…Xenon was introduced into the samples using a flow apparatus as described in reference [12]. The biosensor used was composed of cryptophane-A cage linked to biotin via 6 glycine units with an additional peptide that solubilizes the biosensor (structure 3 described in reference [10]). Data acqui-sition was done using the pulse sequence in Figure 1A, using two selective gaussian pulses separated by a parametric delay t 1 .…”

“…The FID was zero-filled to 256 points then Fourier transformed as shown in Figure 2C. The temperature during experiments was maintained at 20 o C in order to maintain a constant exchange rate of the biosensor [10].…”

“…Xenon biosensors [9] advantageously use the above-mentioned properties. An avidin specific sensor has previously been used to detect the presence of avidin protein at low concentrations [10]. The potential for these sensors as targeted contrast agents for imaging was also recently shown [11].…”

129Xe NMR-based sensors: biological applications and recent methods

“…Some studies have noted that the tether between the host molecule and the antenna has a crucial importance. 26 If the ligand and/or the biological receptor have high molecular weights, a too short or too rigid tether makes that the moiety hosting xenon can have the same correlation time as the macromolecule. This leads to accelerated xenon transverse relaxation, which has the main consequence of broadening the signal of bound xenon and impedes its direct detection.…”