Total suppression of sidebands in CPMAS C-13 NMR

Dixon, William J.; Schaefer, Jacob; Sefcik, M. D.; Stejskal, E. O.; McKay, Robert A.

doi:10.1016/0022-2364(82)90199-8

Cited by 220 publications

(164 citation statements)

References 2 publications

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“…A Bruker MSL-300 (Bruker) spectrometer system equipped with a wide-bore superconducting magnet system and a multinuclear, double-bearing 7 mm CPMAS VT probe (Bruker) and associated with high-power pulse amplifiers provided high-resolution solid spectra of natural abundance "$C and $"P at a frequency of 75n48 MHz and 121n497 MHz, respectively. CPMAS spectra for "$C were acquired using total suppression of side bands (TOSS) (Dixon et al, 1982). Typical spectrometer conditions were a proton π\2 excitation pulse length of 6 µs and a contact time of 1 ms, and the resulting spectra were acquired under high-power decoupling.…”

Section: Methodsmentioning

confidence: 99%

Effects of hydration on molecular mobility in phase-bright Bacillus subtilis spores

Leuschner

Lillford

2000

Microbiology

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The molecular mobility of 31 P and 13 C in dormant Bacillus subtilis spore samples with different water concentrations was investigated by high-resolution solidstate NMR. Lowest molecular mobility was observed in freeze-dried preparations. Rehydration to a 10 % weight increase resulted in increases in molecular motions and addition of excess water furthered this effect. A spore slurry which had been freeze-dried displayed after addition of excess water similar NMR spectra to native wet preparations. Dipicolinic acid (DPA), which is mainly located in the core, was detected at all hydration levels in 13 C crosspolarization magic angle spinning (CPMAS) but not in single-pulse magic angle spinning (SPMAS) spectra, indicating that hydration had no effect on its mobility. The molecular mobility of 31 P, present mainly in core-specific components, was strongly dependent on hydration. This result suggests reversible water migration between inner spore compartments and the environment, whereas 13 C spectra of DPA indicate that it is immobilized in a water-insoluble network in the core. Scanning transmission electron microscopy revealed that freeze-dried spores were significantly longer and narrower than fully hydrated spores and had a 3 % smaller volume.

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Section: Methodsmentioning

confidence: 99%

Effects of hydration on molecular mobility in phase-bright Bacillus subtilis spores

Leuschner

Lillford

2000

Microbiology

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“…All spectra were acquired using ramp cross polarization and magic angle spinning (CP/ MAS) (12)(13)(14). A SPINAL-64 decoupling pulse sequence was used, and the spinning side bands were suppressed using total sideband suppression (15,16). A contact time of 1 ms, MAS frequency of 4.0 kHz, and a 1 H decoupling field of 70-80 kHz were used.…”

Section: Ssnmr Spectroscopymentioning

confidence: 99%

Investigating Gabapentin Polymorphism Using Solid-State NMR Spectroscopy

et al. 2012

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Abstract. Solid-state NMR spectroscopy (SSNMR), coupled with powder X-ray diffraction (PXRD), was used to identify the physical forms of gabapentin in samples prepared by recrystallization, spray drying, dehydration, and milling. Four different crystalline forms of gabapentin were observed: form I, a monohydrate, form II, the most stable at ambient conditions, form III, produced by either recrystallization or milling, and an isomorphous desolvate produced from desolvating the monohydrate. As-received gabapentin (form II) was ball-milled for 45 min in both the presence and absence of hydroxypropylcellulose (HPC). The samples were then stored for 2 days at 50°C under 0% relative humidity and analyzed by 13 C SSNMR and PXRD. High-performance liquid chromatography was run on the samples to determine the amount of degradation product formed before and after storage. The 1 H T 1 values measured for the sample varied from 130 s for the as-received unstressed material without HPC to 11 s for the material that had been ball-milled in the presence of HPC. Samples with longer 1 H T 1 values were substantially more stable than samples that had shorter T 1 values. Samples milled with HPC had detectable form III crystals as well. These results suggest that SSNMR can be used to predict gabapentin stability in formulated products.

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“…All solid-state experiments included ramped-amplitude cross polarization (28,29) and magic angle spinning (30) at a rate of 5 kHz, and SPINAL64 decoupling (31) at a field strength of ∼72 kHz. Spectral acquisitions included total suppression of spinning sidebands (32), and samples were externally referenced with 3-methylglutaric acid (33) Pulse delays of at least 1.5 times the 1 H T 1 (obtained via inversion recovery) were used 400, 65, and 45 s for LMT, CYA, and their salt, respectively. All spectral acquisitions took place at ambient temperature.…”

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confidence: 99%

Improvement of Physicochemical Properties of an Antiepileptic Drug by Salt Engineering

et al. 2012

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Abstract. The focus of the present investigation was to evaluate the feasibility of using cyclamic salt of lamotrigine in order to improve its solubility and intrinsic dissolution rate (IDR). The salt was prepared by solution crystallization method and characterized chemically by fourier transform infrared spectroscopy (FTIR), proton ( 1 H) and carbon ( 13 C) nuclear magnetic resonance (liquid and solid, NMR) spectroscopy, physically by powder X-ray diffraction (PXRD), thermally by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), physicochemically for solubility, IDR, solution and solid-state stability, and polymorphism by solution recrystallization and slurry conversion studies. The FTIR, NMR, PXRD, DSC, and TGA spectra and thermograms indicated the salt formation. The salt formation increased lamotrigine solubility by 19-fold and IDR by 4.9-fold in water. The solution and solid-state stability were similar to parent molecule and were resistant to polymorphic transformation. In conclusion, cyclamic salt of lamotrigine provides another potential avenue for the pharmaceutical development of lamotrigine with improved physicochemical properties especially for pediatric population. It is also possible that appropriate dosage forms can be formulated with much lower drug amount and better safety profile than existing products.

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Total suppression of sidebands in CPMAS C-13 NMR

Cited by 220 publications

References 2 publications

Effects of hydration on molecular mobility in phase-bright Bacillus subtilis spores

Effects of hydration on molecular mobility in phase-bright Bacillus subtilis spores

Investigating Gabapentin Polymorphism Using Solid-State NMR Spectroscopy

Improvement of Physicochemical Properties of an Antiepileptic Drug by Salt Engineering

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