JEOL Resources

Fast MAS solid-state NMR toolbox for biomolecules_NM210002E

Fri, 17 Sep 2021 07:13:49 GMT

Introduction

Solid-state NMR is a useful tool to elucidate protein structures. Although fully ¹³C and ¹⁵N labelled samples are required, solid-state NMR provides complementary or unique information that is not accessible by other typical methods. For example, there are, in principle, no upper or lower limits to molecular weight in solid-state NMR, unlike solution NMR and cryo EM. In addition, solid-state NMR is a very sensitive probe of local dynamics. One of the stumbling block of solid-state NMR is sample amount. Indeed, 20 – 50 mg of fully labelled (expensive!) samples are required for 3.2 mm / 4 mm MAS rotors. However, the recent developments allowing MAS rates above 70 kHz change the situation completely. [1] Indeed, the 0.75 mm (1 mm) MAS rotors used for fast MAS experiments (up to 120 (80) kHz) only require 290 (800) nL of sample, enabling solid-state NMR measurements on sub-milligram amounts of sample. Another great advantage of fast MAS is the averaging out of most of the anisotropic interactions, allowing the use of low power schemes (decoupling, recoupling, cross-polarization etc.), which in turns avoids sample heating. High resolution ¹H spectra become readily available in these conditions, especially for microcrystalline proteins. This is the biggest advantage of fast MAS, since ¹H detection dramatically improves sensitivity compared to traditional ¹³C detection. As a consequence, fast MAS solid-state NMR is now a versatile tool to study the structure and dynamics of biomolecules, for which the first step is sequence-specific resonance assignment. To this end, requisite experiments for sequential backbone and sidechain assignments are well established. [2] Here, we introduce the tool box available for the Delta software together with examples on fully protonated Het-s (226-280) protein.

[1] Review: Y. Nishiyama, Solid State Nucl. Magn. Reson. 78 (2016) 24-36.
[2] E. Barbet-Massin et al., J. Am. Chem. Soc. 136 (2014) 12489-12497.

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19F solid state NMR by using 2mmMAS probe_NM180013E

Wed, 07 Jul 2021 08:38:12 GMT

¹⁹F solid state NMR by using 2mmMAS probe

JEOL 2mm MAS probe enables MA Spinning at nearly twice MAS speed of the conventional 3.2mm and 4mm MAS probe with 20 times the sample volume of the 1mm MAS probe. An attractive application of the 2mm MAS probe is ¹⁹F NMR. Strong ¹⁹F homonuclear dipolar coupling and wide chemical shift range cause a series of spinning side band (SSB) which make it difficult to analyze ¹⁹F spectra obtained by using the conventional 3.2mm and 4mm probes. The 2mm probe can achieve 40kHz MAS speeds, the resulting ¹⁹F spectra will had small well managed SSB’s.
Here, we introduce ¹⁹F solid state NMR spectra of Nafion known as a solid polymer electrolyte for fuel cells. Fig.1 shows ¹⁹F MAS spectra of Nafion at various MAS speeds. 40kHz MAS gives a clear ¹⁹F spectrum without overlapping of SSBs whereas overlap occur between center bands and their SSBs at MAS speeds less than 40kHz. Moreover, the much greater sensitivity of the 2mm probe than the 1mm probe enables direct observation of low sensitive nuclei such as ¹³C. Thus, ¹³C{¹⁹F} CPMAS( Fig.2) and ¹³C-¹⁹F 2D-HETCOR (Fig.3) can easily be obtained.

Chemical structure of Nafion

JNM-ECZ600R, 2mmHXMAS probe

Fig.1 ¹⁹F single pulse at various MAS frequencies. Peaks marked by * represent SSBs.

Fig.2 ¹³C {¹⁹F} CPMAS

Fig.3 ¹³C-¹⁹F HETCOR with high (left) and low (right) level thresholds.

Reference: Q. Chen and K. Schmidt-Rohr, Macromolecules 2004, 37, 5995-6003
Nafion is a trademark of The Chemorus Company.

2mm HXMAS probe Multi-use probe capable of high speed MAS and high sensitivity measurements_NM210001E

Wed, 07 Jul 2021 08:15:38 GMT

¹³C sensitivity

The 2mm probe can obtain ¹³C CPMAS spectra with a sensitivity of about 20 to 30% less than the 3.2mm probe although the sample volume is about 1/3. This probe can be used for a daily use of ¹³C measurement and is especially effective for measuring a small amount of sample.

Fig.1 Comparison of¹³C sensitivity among various probes. ¹³C CPMAS spectra for Hexamethylbenzen (HMB) were obtained using 3.2mm, 2mm, 1mm and 0.75mm HXMAS probes. SNRs were calculated using methyl signals of HMB.

Temperature increase caused by MAS

In solid state MAS measurement, the sample temperature rises due to the friction between the spinning control gas and the sample tube. Since the 2 mm probe can perform MAS more efficiently than the 3.2 mm probe, the rise in sample temperature can be suppressed. For example, 20kHz MAS raises nearly 40°C in the 3.2mm probe, while it raises only 5°C in the 2mm probe. The 2mm probe is recommended to obtain a ¹³C spectrum with less spinning sidebands while suppressing the sample temperature rise.

Fig.2 Relation between spinning frequency and temperature increase of samples for 3.2mm and 2mm probes.

¹H indirect detection

The sensitivities of nuclei with low gyromagnetic ratios can be dramatically improved by ¹H indirect methods owing to high sensitivity and resolution of ¹H at very fast MAS regime. 40kHz MAS achieved by the 2mm probe provides ¹H high resolution and allows to obtain ¹H indirect spectra. Although the sensitivity with the same sample volume is inferior to that of the 1mm probe, actual sensitivity of the ¹H indirect detection using the 2mm probe is much higher because of much larger sample volume. As an example, natural abundance ¹H/¹⁵N CP-based HSQC spectra of cimetidine measured by the 1mm and 2mm probes are shown.

Fig.3 Chemical structure of cimetidine

Fig.4 ¹H/¹⁵N CP-based HSQC 2D spectra of cimetidine obtained by 1mm and 2mm HXMAS probes. ¹H sliced spectra at ¹⁵N 163ppm are also shown.

MQMAS

The 2mm probe is also useful for MQMAS measurement of quadrupole nuclei. The MQMAS is a representative method for observing quadrupolar nuclei with high resolution, and is widely used because it is available with a standard solid state MAS probe. A strong rf magnetic field strength ,B₁, is essential for the MQMAS method because the excitation efficiency of multi-quantum excitation affects the sensitivity of MQMAS measurements. The 2mm probe can apply a stronger B₁ than the conventional 3.2mm probe, enabling highly sensitive MQMAS measurements. Here, we show the ²⁷Al 3QMAS spectra of kyanite (Al₂SiO₅) measured with the 3.2mm and the 2mm probes.

Fig.5 ²⁷Al 3QMAS spectra of kyanite (Al₂SiO₅) obtained by 3.2mm and 2mm HXMAS probes. The rf field strength B₁ of multi-quantum excitation are 77kHz for 3.2mm and 104kHz for 2mm, respectively.

Solid State NMR Brochure

Tue, 15 Jun 2021 14:30:13 GMT

JEOL offers a full range of Magic-Angle-Spinning (MAS) probes and tools matched to a wide variety of solid-state NMR applications. JEOL MAS probes feature sample tube diameters to match the user sample and sensitivity needs. JEOL narrow bore MAS probes offer improved stability for high-speed spinning or for very large volumes. The JNM-ECZ Series NMR Spectrometer automatically updates the relevant spectrometer settings for all NMR probes for fast and easy switching between solids and liquids NMR operation.

Please Click Below to Download the Full Brochure

Experimental set-up of high-resolution 1H solid-state NMR by wPMLG_NM200010E

Fri, 11 Sep 2020 14:41:48 GMT

1H, in principle, is very useful nucleus to investigate atomic-resolution structures and dynamics due to its high abundance (>99%) and gyromagnetic ratio (600 MHz at 14.1T). In fact 1H is the first choice of nucleus in solution NMR. On the other hand, 1H NMR of rigid solids is much less common. This is because 1H solid-state NMR gives very broad (~50 kHz) and featureless spectra (Fig 1a) due to strong 1H-1H dipolar coupling, which is dynamically averaged out in solution. Magic angle spinning (MAS) removes the broadening to the first order, but is not enough to achieve high resolution 1H NMR at moderate MAS rate (Fig 1b). Tremendous efforts were made to overcome this issue from the early dates of solid-state NMR towards high-resolution 1H NMR [1]. Most of them combine MAS with sophisticated 1H pulses which is dubbed CRAMPS (combined rotation and multiple pulse spectroscopy). Nowadays very fast MAS > 60 kHz can be used to achieve high-resolution 1H solid-state NMR (Fig 1c) [2]. However, the traditional CRAMPS is still useful as that can be performed with very conventional solid-state NMR equipment, for example 4 mm MAS probe with a 400 MHz spectrometer. Moreover, wPMLG at moderate MAS rate often overwhelms fast MAS in terms of resolution. In this note, we will describe tutorial guidance to optimize experimental parameters for CRAMPS.

2D homonuclear correlation 1H solid-state NMR by wPMLG_NM200011E

Fri, 11 Sep 2020 14:27:11 GMT

Multidimensional correlation NMR spectroscopies, which provides inter-nuclear proximity/connectivity, play a crucial role to probe the atomic resolution structures. Especially, 1H-1H homonuclear correlation spectroscopy is quite useful source of information because of high abundance (>99%) and gyromagnetic ratio, thus resulting in strong inter nuclear interactions. Thanks to the development of high resolution 1H solid-state NMR, now it is feasible to observe 1H-1H correlation high resolution solid-state NMR [1]. There are two distinctive categories; 1) single quantum (SQ)/SQ correlation and 2) double quantum (DQ)/SQ correlations. In this note we introduce 2D 1H SQ/ 1H SQ and 1H DQ/ 1H SQ correlation spectroscopy to probe the internuclear proximity using high-resolution 1H solid-state NMR techniques.

The occupied/emptied sites analysis of Lithium Titanium Oxide anodes: How can we obtain high resolution solid state Lithium NMR spectra? _NM200001E

Tue, 28 Jul 2020 16:10:43 GMT

Lithium ion secondary batteries using spinel-type lithium titanium oxide (LTO) as the negative electrode material are excellent in safety and cycle characteristics due to their chemical stability, and have already been put into practical use.

Visualization of hydrogen-bonding: Electron and NMR nano-crystallography_NM190004

Tue, 28 Jul 2020 15:43:43 GMT

Here, we combine ED and solid-state NMR through the first principle quantum computation with the NMR crystallography approach for crystalline structure solution. The method, electron and NMR nano-crystallography, can be applied to nano- to micro-crystals even for mixture samples.

Spectral Separation of mixtures by solid state NMR_NM180015E

Tue, 28 Jul 2020 15:39:05 GMT

Solid state NMR is a powerful tool to obtain information in the crystalline state which would be lost in the solution state.

A 1H Solid State NMR Application for Pharmaceutical Development by using Ultra Fast MAS: Drug-Polymer Intermolecular Interaction on Solid Dispersions_NM190003E

Tue, 28 Jul 2020 15:36:46 GMT

The low oral bioavailability of a drug due to its poor aqueous solubility is a major challenge for pharmaceutical development. Solid dispersion (SD), where the amorphous drug is dispersed into the polymer matrix, is one of the useful approaches to improve the aqueous solubility. However, thermodynamically unstable nature of an amorphous drug increases its susceptibility to recrystallize upon storage, which, in turn, reduces its solubility and dissolution. Therefore, design of thermodynamically stable SD is required.