Identification, classification, and signal amplification capabilities of high-turnover gas binding hosts in ultra-sensitive NMR

Abstract

Labile complexation of cucurbit[6]uril with xenon becomes detectable through saturation transfer with highly efficient gas turnover for ultra-sensitive NMR applications.

Protein Nanostructures Produce Self-Adjusting Hyperpolarized Magnetic Resonance Imaging Contrast through Physical Gas Partitioning

“…The much higher turnover rate of GVs, and other fast-exchanging xenon hosts such as cucurbituril, 13,33 compared to CrA, suggests a proportionally lower detection limit for these agents. However, other limitations come into play in approaching such dilute detection limits.…”

“…Host structures with (relative) fast Xe exchange provide high CEST efficiency (see Supporting Information S7). 13 However, the high turnover in combination with the large chemical shift separations (~10 kHz at 9.4 T) can cause a significant exchange-mediated spin-spin relaxation effect that manifests as a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 12 shortened apparent relaxation time, T 2,app . 30 As mentioned above, this is of particular importance for hyperpolarized nuclei because they are preferably detected with echo trains to improve SNR from each batch of transverse magnetization 17 or to encode as much spatial information as possible.…”

“…The product of the number of xenon atoms hosted by each contrast agent with the exchange rate provides a fundamental measure of contrast amplification. 13 By this accounting, GVs derived from Ana are the most efficient contrast agents on a per particle consideration with a turnover of ca. 92 × 10 6 s -1 , closely followed by Halo with ca.…”

“…Prominent examples for imaging applications are based on cryptophane-A (CrA) [10][11][12] or cucurbit [6,7]uril (CB6,7). [13][14][15] (Hyper-)CEST efficiency scales with the concentration of bound nuclei, [B] (Figure 1). …”

Rotaxane probes for protease detection by 129Xe hyperCEST NMR

“…Cucurbit [6]uril (CB6) was also reported as a promising 129 Xe host for hyperCEST NMR. 18,19 Recent work has taken advantage of known CB6 supramolecular host-guest interactions 20 to alter the ability of CB6 to participate in CEST in response to enzymatic reactions or protein binding. This strategy enabled detection of avidin, carbonic anhydrase II, and lysine decarboxylase.…”