Year: 2025
Type: article
Abstract: . Standard solution NMR measurements use 5-mm outer diameter (OD) sample tubes that require ca 0.5 mL of solvent to minimize “end effects” on magnetic field homogeneity in the active volume of the sample. Shigemi cells reduce the solvent requirement to ca 0.29 mL. At high ionic strength, or at ultrahigh magnetic fields, smaller OD samples are needed to study samples in conductive, radiofrequency absorbing solvents such as water. We demonstrate an effective and inexpensive alternative for reducing the active sample volume to 0.13 mL by 3D printing of ellipsoidal shaped cells that are inserted into 5-mm OD NMR tubes. Static magnetic susceptibility, χ, of printer resin was measured using a simple slice-selection pulse sequence. We found that the χ of water increases linearly with NaCl concentration, from -9.05 ppm to -8.65 ppm for 0 to 2 M NaCl. The χ of D2O was measured to be -9.01 ppm. The susceptibility difference between the resin (χ= -9.40 ppm) and water can be minimized by paramagnetic doping of the resin. Such doping was found unnecessary for obtaining high quality protein NMR spectra when using ellipsoidal shaped cells that are insensitive to susceptibility mismatching. The microcells offer outstanding RF and good Bo homogeneities. Integrated 600-MHz HSQC signal intensities for the microcell sample in PBS buffer were 6.5±4 % lower than for 0.5 mL of the same protein solution in a regular 5-mm sample tube. The cell is demonstrated for N-acetylated α-synuclein in PBS buffer, and for observing tetramerization of melittin at 2 M NaCl.
Source: Magnetic Resonance
Language: English
Subfield: Spectroscopy
Field: Chemistry
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $992
Award: G6288077373
OpenAlex ID: W4412725845