A Robust Technique for Two-Dimensional Separation of Undistorted Chemical-Shift Anisotropy Powder Patterns in Magic-Angle-Spinning NMR

Sf, Liu; Jd, Mao; Schmidt‐Rohr, Klaus

doi:10.1006/jmre.2002.2503

Cited by 199 publications

(278 citation statements)

References 33 publications

(73 reference statements)

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“…The result clearly indicates that S 0 -S is nearly zero in all of the functional signals. The CSA principle axis values of all of the functional signals in iPB1 36 are very similar to other polyolefins. 25,35 Thus, this result demonstrates that there is no large amplitude motion in iPB1 during t mix ¼200 ms at ambient temperature.…”

Section: Differential Scanning Calorimetrymentioning

confidence: 63%

Critical roles of molecular dynamics in the superior mechanical properties of isotactic-poly(1-butene) elucidated by solid-state NMR

Miyoshi

Mamun

2011

Polym J

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Isotactic-poly(1-butene) (iPB1) shows superior mechanical properties after crystal-crystal transitions. Recently, Miyoshi et al. found that crystalline stems in metastable tetragonal crystal perform uniaxial rotational diffusions accompanying side-chain conformational transitions in the fast motional limit (correlation time, /s c S o10 À7 s; Macromolecules 2010, 43, 3986-3989.). In this study, molecular dynamics in stable trigonal crystal is investigated by solid-state nuclear magnetic resonance, which indicates that crystalline stems and side-chain conformations are completely fixed up to melting points (/s c S 410 s). In addition, lamellar thickness, /lS of iPB1 and a low isotacticity iPB1 (low_iPB1) with /mmmmS¼78%, respectively, were investigated by small-angle X-ray scattering. The low_iPB1 sample shows very week supercooling dependence of /lS (B5 nm), whereas iPB1 shows strong supercooling dependence of /lS (10-28 nm). On the basis of molecular dynamics and /lS results, molecular dynamics effects on structures and unique mechanical property of iPB1 are discussed.

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Section: Differential Scanning Calorimetrymentioning

confidence: 63%

Critical roles of molecular dynamics in the superior mechanical properties of isotactic-poly(1-butene) elucidated by solid-state NMR

Miyoshi

Mamun

2011

Polym J

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“…More detailed information about the structural incorporation of CO 2 and its motional behavior is obtained from the 13 C anisotropic chemical shift (CSA) (49). The CSA of rigid CO 2 is particularly large, 314.5 ppm (50).…”

Section: Resultsmentioning

confidence: 99%

High-temperature in situ crystallographic observation of reversible gas sorption in impermeable organic cages

Baek

Moon

Graf

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Crystallographic observation of adsorbed gas molecules is a highly difficult task due to their rapid motion. Here, we report the in situ single-crystal and synchrotron powder X-ray observations of reversible CO 2 sorption processes in an apparently nonporous organic crystal under varying pressures at high temperatures. The host material is formed by hydrogen bond network between 1,3,5-tris-(4-carboxyphenyl)benzene (H 3 BTB) and N,N-dimethylformamide (DMF) and by π-π stacking between the H 3 BTB moieties. The material can be viewed as a well-ordered array of cages, which are tight packed with each other so that the cages are inaccessible from outside. Thus, the host is practically nonporous. Despite the absence of permanent pathways connecting the empty cages, they are permeable to CO 2 at high temperatures due to thermally activated molecular gating, and the weakly confined CO 2 molecules in the cages allow direct detection by in situ single-crystal X-ray diffraction at 323 K. Variable-temperature in situ synchrotron powder X-ray diffraction studies also show that the CO 2 sorption is reversible and driven by temperature increase. Solid-state magic angle spinning NMR defines the interactions of CO 2 with the organic framework and dynamic motion of CO 2 in cages. The reversible sorption is attributed to the dynamic motion of the DMF molecules combined with the axial motions/angular fluctuations of CO 2 (a series of transient opening/closing of compartments enabling CO 2 molecule passage), as revealed from NMR and simulations. This temperature-driven transient molecular gating can store gaseous molecules in ordered arrays toward unique collective properties and release them for ready use.in situ X-ray diffraction | nonporous organic crystalline material | CO 2 sorption G uest capture, storage, and removal in porous materials have been interesting topics in chemistry (1-7). The porosity of solids is one of the important factors determining their potential applications in guest storage. Because the storage generally uses void spaces interconnected through large open channels between the voids inside the crystal, nonporous or seemingly nonporous materials have received less attention. Over the past decades, nevertheless, due to the potential for selective guest capture and release in a controlled manner there have been attempts to study such materials which include calixarenes (8-17), 4-phenoxyphenol (18), biconcave molecules (19), tris(5-acetyl-3-thienyl)methane (20), metallocyclic complex (21), clarithromycin (22), and metalorganic frameworks (23, 24).Single-crystal X-ray diffraction can provide the crucial information on the binding interactions or structural changes of guest molecules within pores (25-27). However, the crystallographic observation of adsorbed gas adsorbents generally has not been possible due to the poor crystalline order of adsorbents upon removing residual solvent/guest molecules and the high mobility of gases even at low temperatures. Only a limited number of gas-adsorbed single-crystal struct...

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“…35 This experiment yielded static-like chemical shift powder patterns under MAS by recoupling the CSA interaction with rotor-synchronized 360°pulses. The timing of the 360°pulses was chosen to give a CSA scaling factor of 0.155.…”

Section: Methodsmentioning

confidence: 99%

Structure of an elastin‐mimetic polypeptide by solid‐state NMR chemical shift analysis

et al. 2003

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The conformation of an elastin-mimetic recombinant protein, [(VPGVG)4(VPGKG)]39, is investigated using solid-state NMR spectroscopy. The protein is extensively labeled with 13C and 15N, and two-dimensional 13C-13C and 15N-13C correlation experiments were carried out to resolve and assign the isotropic chemical shifts of the various sites. The Pro 15N, 13Calpha, and 13Cbeta isotropic shifts, and the Gly-3 Calpha isotropic and anisotropic chemical shifts support the predominance of type-II beta-turn structure at the Pro-Gly pair but reject a type-I beta-turn. The Val-1 preceding Pro adopts mostly beta-sheet torsion angles, while the Val-4 chemical shifts are intermediate between those of helix and sheet. The protein exhibits a significant conformational distribution, shown by the broad line widths of the 15N and 13C spectra. The average chemical shifts of the solid protein are similar to the values in solution, suggesting that the low-hydration polypeptide maintains the same conformation as in solution. The ability to measure these conformational restraints by solid-state NMR opens the possibility of determining the detailed structure of this class of fibrous proteins through torsion angles and distances.

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A Robust Technique for Two-Dimensional Separation of Undistorted Chemical-Shift Anisotropy Powder Patterns in Magic-Angle-Spinning NMR

Cited by 199 publications

References 33 publications

Critical roles of molecular dynamics in the superior mechanical properties of isotactic-poly(1-butene) elucidated by solid-state NMR

Critical roles of molecular dynamics in the superior mechanical properties of isotactic-poly(1-butene) elucidated by solid-state NMR

High-temperature in situ crystallographic observation of reversible gas sorption in impermeable organic cages

Structure of an elastin‐mimetic polypeptide by solid‐state NMR chemical shift analysis

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