Solid State NMR Studies of the Adsorbed States of Formic Acid on Y Zeolites

1980 ◽  
Vol 3 ◽  
Author(s):  
T. Michael Duncan ◽  
Robert W. Vaughan
Keyword(s):  
Solid State ◽  
Formic Acid ◽  
Solid State Nmr ◽  
Double Resonance ◽  
Chemical Shift Anisotropy ◽  
Surface States ◽  
Cross Polarization ◽  
Nmr Studies ◽  
Y Zeolites ◽  
Nmr Techniques

ABSTRACTSeveral multiple-pulse double-resonance NMR techniques have been applied to isolate and characterize the spectra of the adsorbed states of formic acid on two Y zeolites. The two surface states, bidentatT3 and ynidentate, possess different motional properties and 13C - H cross-polarization techniques may be used to separate the spectra. The 13C chemical shift anisotropy is founa to iorrelate with the symmetry of the formate species. The H spectrum of the carbonyl hydrogen, selectively observed with the dipolardifference method, indicates that this hydrogen becomes more acidic upon adsorption.

scholarly journals Structure and Orientation of Pardaxin Determined by NMR Experiments in Model Membranes

2004 ◽  
Vol 279 (44) ◽  
pp. 45815-45823 ◽  
Author(s):  
Fernando Porcelli ◽  
Bethany Buck ◽  
Dong-Kuk Lee ◽  
Kevin J. Hallock ◽  
Ayyalusamy Ramamoorthy ◽  
...  
Keyword(s):  
Solid State ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Solid State Nmr ◽  
Double Resonance ◽  
Slow Motion ◽  
Solution Nmr ◽  
Helical Conformation ◽  
Hydrophobic Core ◽  
Nmr Studies

Pardaxins are a class of ichthyotoxic peptides isolated from fish mucous glands. Pardaxins physically interact with cell membranes by forming pores or voltage-gated ion channels that disrupt cellular functions. Here we report the high-resolution structure of synthetic pardaxin Pa4 in sodium dodecylphosphocholine micelles, as determined by1H solution NMR spectroscopy. The peptide adopts a bend-helix-bend-helix motif with an angle between the two structure helices of 122 ± 9°, making this structure substantially different from the one previously determined in organic solvents. In addition, paramagnetic solution NMR experiments on Pa4 in micelles reveal that except for the C terminus, the peptide is not solvent-exposed. These results are complemented by solid-state NMR experiments on Pa4 in lipid bilayers. In particular,13C-15N rotational echo double-resonance experiments in multilamellar vesicles support the helical conformation of the C-terminal segment, whereas2H NMR experiments show that the peptide induces considerable disorder in both the head-groups and the hydrophobic core of the bilayers. These solid-state NMR studies indicate that the C-terminal helix has a transmembrane orientation in DMPC bilayers, whereas in POPC bilayers, this domain is heterogeneously oriented on the lipid surface and undergoes slow motion on the NMR time scale. These new data help explain how the non-covalent interactions of Pa4 with lipid membranes induce a stable secondary structure and provide an atomic view of the membrane insertion process of Pa4.

New in situ solid-state NMR techniques for probing the evolution of crystallization processes: pre-nucleation, nucleation and growth

2015 ◽  
Vol 179 ◽  
pp. 115-140 ◽  
Author(s):  
Colan E. Hughes ◽  
P. Andrew Williams ◽  
Victoria L. Keast ◽  
Vasileios G. Charalampopoulos ◽  
Gregory R. Edwards-Gau ◽  
...  
Keyword(s):  
Solid State ◽  
Liquid State ◽  
Solid State Nmr ◽  
Crystallization Process ◽  
Solid Particles ◽  
Crystal Formation ◽  
Nmr Studies ◽  
Nmr Techniques ◽  
Solid Phases

The application of in situ techniques for investigating crystallization processes promises to yield significant new insights into fundamental aspects of crystallization science. With this motivation, we recently developed a new in situ solid-state NMR technique that exploits the ability of NMR to selectively detect the solid phase in heterogeneous solid–liquid systems (of the type that exist during crystallization from solution), with the liquid phase “invisible” to the measurement. As a consequence, the technique allows the first solid particles produced during crystallization to be observed and identified, and allows the evolution of different solid phases (e.g., polymorphs) present during the crystallization process to be monitored as a function of time. This in situ solid-state NMR strategy has been demonstrated to be a powerful approach for establishing the sequence of solid phases produced during crystallization and for the discovery of new polymorphs. The most recent advance of the in situ NMR methodology has been the development of a strategy (named “CLASSIC NMR”) that allows both solid-state NMR and liquid-state NMR spectra to be measured (essentially simultaneously) during the crystallization process, yielding information on the complementary changes that occur in both the solid and liquid phases as a function of time. In this article, we present new results that highlight the application of our in situ NMR techniques to successfully unravel different aspects of crystallization processes, focusing on: (i) the application of a CLASSIC NMR approach to monitor competitive inclusion processes in solid urea inclusion compounds, (ii) exploiting liquid-state NMR to gain insights into co-crystal formation between benzoic acid and pentafluorobenzoic acid, and (iii) applications of in situ solid-state NMR for the discovery of new solid forms of trimethylphosphine oxide and l-phenylalanine. Finally, the article discusses a number of important fundamental issues relating to practical aspects, the interpretation of results and the future scope of these techniques, including: (i) an assessment of the smallest size of solid particle that can be detected in in situ solid-state NMR studies of crystallization, (ii) an appraisal of whether the rapid sample spinning required by the NMR measurement technique may actually influence or perturb the crystallization behaviour, and (iii) a discussion of factors that influence the sensitivity and time-resolution of in situ solid-state NMR experiments.

Solid-state NMR studies of cadmium: 113Cd1H cross polarization and magic-angle spinning

1980 ◽  
Vol 41 (1) ◽  
pp. 158-168 ◽  
Author(s):  
T.T.P Cheung ◽  
L.E Worthington ◽  
P.Dubois Murphy ◽  
B.C Gerstein
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Cross Polarization ◽  
Nmr Studies ◽  
Angle Spinning

Chain Dynamics and Crystallinite Network Structure of Poly[R-3-hydroxybutyrate-co-4-hydroxybutyrate] as revealed by Solid-state NMR

Soft Matter ◽  
2021 ◽  
Author(s):  
Zhijie Xia ◽  
Haoyuan Zhao ◽  
Yu-Song Wang ◽  
Yiming Ma ◽  
Xiaoliang Wang ◽  
...  
Keyword(s):  
Solid State ◽  
High Resolution ◽  
Network Structure ◽  
Solid State Nmr ◽  
Cross Polarization ◽  
Chain Dynamics ◽  
Nmr Techniques ◽  
Direct Polarization

The chain dynamics and crystallinite network structure of Poly[R-3-hydroxybutyrate-co-4-hydroxybutyrate] (P(3HB-co-4HB)) were systematically investigated by the combination of various solid-state NMR techniques. The high-resolution 13C cross-polarization (CP) and direct-polarization (DP) MAS...

Solution and Solid State NMR Studies of the Structure and Dynamics of C60 and C70

1990 ◽  
Vol 206 ◽  
Author(s):  
R. D. Johnson ◽  
C. S. Yannoni ◽  
J. Salem ◽  
G. Meijer ◽  
D. S. Bethune
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Variable Temperature ◽  
Chemical Shift Anisotropy ◽  
Resonance Assignments ◽  
Powder Pattern ◽  
High Symmetry ◽  
Nmr Studies ◽  
Structure And Dynamics ◽  
C Nmr

ABSTRACTWe have investigated the structure and dynamics of C60 and C70 with 13C NMR spectroscopy. In solution, high-resolution spectra reveal that C60 has a single resonance at 143 ppm, indicating a strained, aromatic system with high symmetry. This is strong evidence for a C60 “soccer ball” geometry. A 2D NMR INADEQUATE experiment on 13C-enriched C70 reveals the bonding connectivity to be a linear string, in firm support of the proposed “rugby ball” structure with D5h symmetry, and furnishes resonance assignments. Solid state NMR spectra of C60 at ambient temperatures yield a narrow resonance, indicative of rapid molecular reorientation. Variable temperature T1 measurements show that the rotational correlation time is ∼ 10−9s at 230 K. At 77 K, this time increases to more than 1 ms, and the 13C NMR spectrum of C60 is a powder pattern due to chemical shift anisotropy (tensor components 220, 186, 40 ppm). At intermediate temperatures a narrow peak is superimposed on the powder pattern, suggesting a distribution of barriers to molecular motion in the sample, or the presence of an additional phase in the solid state. A Carr-Purcell dipolar experiment on C60 in the solid state allows the first precise determination of the C60 bond lengths: 1.45 and 1.40Å.

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