¹³C‐TmDOTA as versatile thermometer compound for solid‐state NMR of hydrated lipid bilayer membranes

Abstract

Recent advances in solid-state nuclear magnetic resonance (NMR) techniques, such as magic angle spinning and high-power decoupling, have dramatically increased the sensitivity and resolution of NMR. However, these NMR techniques generate extra heat, causing a temperature difference between the sample in the rotor and the variable temperature gas. This extra heating is a particularly crucial problem for hydrated lipid membrane samples. Thus, to develop an NMR thermometer that is suitable for hydrated lipid samples, thulium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (TmDOTA) was synthesized and labeled with (13) C (i.e., (13) C-TmDOTA) to increase the NMR sensitivity. The complex was mixed with a hydrated lipid membrane, and the system was subjected to solid-state NMR and differential scanning calorimetric analyses. The physical properties of the lipid bilayer and the quality of the NMR spectra of the membrane were negligibly affected by the presence of (13) C-TmDOTA, and the (13) C chemical shift of the complex exhibited a large-temperature dependence. The results demonstrated that (13) C-TmDOTA could be successfully used as a thermometer to accurately monitor temperature changes induced by (1) H decoupling pulses and/or by magic angle spinning and the temperature distribution of the sample inside the rotor. Thus, (13) C-TmDOTA was shown to be a versatile thermometer for hydrated lipid assemblies. Copyright © 2015 John Wiley & Sons, Ltd.

LnDOTA‐d8, a versatile chemical‐shift thermometer for 2H solid‐state NMR

“…Next, we examined the applicability of the 2 H chemical-shift thermometer ErDOTA-d 8 to the determination of the phase transition temperature of hydrated lipid bilayers. In our previous study on a 13 chemical-shift thermometer, [32] the thermometer compound was premixed with liposomes for solid-state NMR measurements because 13 C NMR measurements were largely performed under high-speed MAS conditions. Such conditions require well-balanced packing of the sample and high-power 1 H decoupling irradiation, which causes considerable inhomogeneity in temperature distribution.…”

“…[29][30][31] Recently, we reported that the 13 C chemical shift of the lanthanide Tm complex with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA is a non-deuterated form of 4 in Scheme 1), TmDOTA, is highly temperature dependent and serves as a chemical-shift thermometer for 13 C solid-state NMR measurements of lipid bilayers. [32] Thus, we postulated that the 2 H-labeled lanthanide-DOTA complex, LnDOTA, could be a candidate for a 2 H chemical-shift thermometer. In this study, we prepared a series of 2 H-labeled LnDOTAs and investigated their temperature-dependent chemicalshift changes.…”

19F VT NMR: Novel Tm3+ and Ce3+ Complexes Provide New Insight into Temperature Measurement Using Molecular Sensors

“…[20d,21] In addition to 19 F, other hetero nuclei are also of interest. Recent results showed very high sensitives for 31 P [22] and 59 Co (up to 150 ppm/ K), [23] but nuclei such as 13 C [24] and 2 H [25] are also of interest.…”

Asymmetry-enhanced 59Co NMR thermometry in Co(iii) complexes

“…One method for temperature detection via NMR utilizes a temperature-dependent chemical shift. This technique can use protons ( 1 H), 5-7 19 F, 8,9 13 C, 10,11 and 31 P. 12,13 Yet, the temperature sensitivities of these systems are often low, <1 ppm °C−1 (e.g, 0.01 ppm °C−1 for 1 H in H 2 O, 6 or 0.012 ppm °C−1 in 19 F as perfluorotributylamine 9 ). A related technique, PARACEST (PARAmagnetic Chemical Exchange Saturation Transfer), can imbue a temperature dependence to the 1 H chemical shift of bulk water through hyperfine coupling in open-shell lantha-nide complexes.…”