Igi xe 2000

Hyperpolarized (hp) ¹²⁹Xe was generated using the spin-exchange optical pumping (SEOP) method with a home-built ¹²⁹Xe polarizer based on the IGI.Xe.2000 commercial model by GE. A Shark 65 W tunable ultra-narrow band diode laser (OptiGrate) set to 795 nm was used for optical pumping of Rb vapor. A gas mixture of 88% helium, 10% nitrogen, and 2% natural abundance xenon (Linde Group, NJ) was used as the hyperpolarizer input. ¹²⁹Xe hyperpolarization level was roughly 10–15%. For each data point in the hyper-CEST z-spectra, hp ¹²⁹Xe was bubbled into a 10-mm NMR tube containing 2.5 mL of sample through capillaries for 20 s, followed by a 3-s delay to allow bubbles to collapse. A Dsnob saturation pulse with 690 Hz bandwidth was used. Pulse length t_pulse = 3.80 ms, field strength B_1,max = 77 μT, number of pulses n_pulse = 400, saturation time T_sat = 1.52 s. NMR experiments were performed using a Bruker BioDRX 500 MHz NMR spectrometer and a 10-mm PABBO probe at 300 K. A 90° hard pulse of this probe has a pulse length of 22 μs. For all experiments, the cryptophane and/or protein concentration was 5 μM, in pH 7.2 PBS, with 0.1% DMSO and 0.1% (v/v) Pluronic L81 (Aldrich) to mitigate foaming. Measurements were averaged over 3 trials.

Hp ¹²⁹Xe gas was generated through SEOP² using a home-built ¹²⁹Xe polarizer based on the IGI.Xe.2000 commercial model (GE). A Shark 65 W tunable ultranarrow band diode laser (OptiGrate) set to 795 nm was used to optically polarize Rb vapor. The efficiency of hyperpolarization was typically 10 to 15%. For direct-detection experiments, generated hp ¹²⁹Xe gas was collected as solid in a cold trap cooled by liquid N₂ and sublimed using a boiling water bath when needed. In a typical hp ¹²⁹Xe NMR experiment, 2.5 mL of sample in a 10 mm NMR tube was degassed by dynamic vacuum (< 4 Pa), followed by pressurizing the headspace to ca. 2.5 × 10⁵ Pa with hp ¹²⁹Xe and subsequent mixing by manually shaking for 5 s. All ¹²⁹Xe NMR experiments were performed on a Bruker BioDRX 500 MHz NMR spectrometer equipped with a 10 mm PABBO probe and a N₂ temperature control unit. An EBURP-1 selective pulse with 660 Hz bandwidth was used to acquire ¹²⁹Xe NMR spectra. Line-broadening corrections of 30–40 Hz were applied to address the weak signals.