Xenon–Protein Interactions: Characterization by X-Ray Crystallography and Hyper-CEST NMR

Abstract

The physiological activity of xenon has long been recognized, though the exact nature of its interactions with biomolecules remains poorly understood. Xe is an inert noble gas, but can act as a general anesthetic, most likely by binding internal hydrophobic cavities within proteins. Understanding Xe-protein interactions, therefore, can provide crucial insight regarding the mechanism of Xe anesthesia and potentially other general anesthetic agents. Historically, Xe-protein interactions have been studied primarily through X-ray crystallography and nuclear magnetic resonance (NMR). In this chapter, we first describe our methods for preparing Xe derivatives of protein crystals and identifying Xe-binding sites. Second, we detail our procedure for Xe hyper-CEST NMR spectroscopy, a versatile NMR technique well suited for characterizing the weak, transient nature of Xe-protein interactions.

Binding site exchange kinetics revealed through efficient spin–spin dephasing of hyperpolarized129Xe

“…This technique has a potential for many applications since Xe is oen used as a surrogate for O 2 to study gas binding proteins. 38,39 Signicant chemical shis have been observed in such proteins [40][41][42] (with 60-80 ppm downeld shi) or macrocyclic hosts in ternary systems that are of pharmacological interest 43,44 (ca. 100 ppm upeld shi).…”

Xenon as a transdermal enhancer for niacinamide in Strat-M™ membranes

“…Studies have been focused on the biologically active properties of xenon used in vivo , 7 8 9 10 in vitro , 11 12 13 14 15 and in silico , 16 17 through which detailed data on the anesthetic and analgesic properties of xenon are obtained. However, the experimental in vivo approach, where xenon can affect biomolecules by contact with the skin, is completely overlooked.…”

129Xe NMR-Protein Sensor Reveals Cellular Ribose Concentration

“…[32][33][34][35][36][37][38] Protein-based hyper-CEST contrast agents have previously been developed for the sensitive detection of biological structures. [39][40][41] The monomeric proteins TEM-1 β-lactamase (Bla) [42][43][44] and maltose-binding protein (MBP) 45 were previously identified by our laboratory as contrast agents for 129 Xe hyper-CEST.…”

“…Previously, we showed that the 'closed' conformation that MBP adopts upon maltose binding is required for generating hyper-CEST contrast, making MBP an ultrasensitive "smart" contrast agent for maltose detection. 45 We sought to extend these studies to other PBPs as potential 129 Xe MR contrast agents. Here, our laboratory investigated ribosebinding protein (RBP) as a hyper-CEST contrast agent for the detection and quantitation of ribose in biological fluids (Scheme 1).…”