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Hanrahan MP, Chen Y, Blome-Fernández R, Stein JL, Pach GF, Adamson MAS, Neale NR, Cossairt BM, Vela J, Rossini AJ. Probing the Surface Structure of Semiconductor Nanoparticles by DNP SENS with Dielectric Support Materials. J Am Chem Soc 2019; 141:15532-15546. [PMID: 31456398 DOI: 10.1021/jacs.9b05509] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Surface characterization is crucial for understanding how the atomic-level structure affects the chemical and photophysical properties of semiconducting nanoparticles (NPs). Solid-state nuclear magnetic resonance spectroscopy (NMR) is potentially a powerful technique for the characterization of the surface of NPs, but it is hindered by poor sensitivity. Dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP SENS) has previously been demonstrated to enhance the sensitivity of surface-selective solid-state NMR experiments by 1-2 orders of magnitude. Established sample preparations for DNP SENS experiments on NPs require the dilution of the NPs on mesoporous silica. Using hexagonal boron nitride (h-BN) to disperse the NPs doubles DNP enhancements and absolute sensitivity in comparison to standard protocols with mesoporous silica. Alternatively, precipitating the NPs as powders, mixing them with h-BN, and then impregnating the powdered mixture with radical solution leads to further 4-fold sensitivity enhancements by increasing the concentration of NPs in the final sample. This modified procedure provides a factor of 9 improvement in NMR sensitivity in comparison to previously established DNP SENS procedures, enabling challenging homonuclear and heteronuclear 2D NMR experiments on CdS, Si, and Cd3P2 NPs. These experiments allow NMR signals from the surface, subsurface, and core sites to be observed and assigned. For example, we demonstrate the acquisition of DNP-enhanced 2D 113Cd-113Cd correlation NMR experiments on CdS NPs and natural isotropic abundance 2D 13C-29Si HETCOR of functionalized Si NPs. These experiments provide a critical understanding of NP surface structures.
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Affiliation(s)
- Michael P Hanrahan
- Iowa State University , Department of Chemistry , Ames , Iowa 50011 , United States.,US DOE Ames Laboratory , Ames , Iowa 50011 , United States
| | - Yunhua Chen
- Iowa State University , Department of Chemistry , Ames , Iowa 50011 , United States.,US DOE Ames Laboratory , Ames , Iowa 50011 , United States
| | | | - Jennifer L Stein
- University of Washington , Department of Chemistry , Seattle , Washington 98195 , United States
| | - Gregory F Pach
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , 15013 Denver West Parkway , Golden , Colorado 80401 , United States
| | - Marquix A S Adamson
- Iowa State University , Department of Chemistry , Ames , Iowa 50011 , United States
| | - Nathan R Neale
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , 15013 Denver West Parkway , Golden , Colorado 80401 , United States
| | - Brandi M Cossairt
- University of Washington , Department of Chemistry , Seattle , Washington 98195 , United States
| | - Javier Vela
- Iowa State University , Department of Chemistry , Ames , Iowa 50011 , United States.,US DOE Ames Laboratory , Ames , Iowa 50011 , United States
| | - Aaron J Rossini
- Iowa State University , Department of Chemistry , Ames , Iowa 50011 , United States.,US DOE Ames Laboratory , Ames , Iowa 50011 , United States
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Baquero EA, Ojo WS, Coppel Y, Chaudret B, Urbaszek B, Nayral C, Delpech F. Identifying short surface ligands on metal phosphide quantum dots. Phys Chem Chem Phys 2016; 18:17330-4. [PMID: 27314745 PMCID: PMC5154294 DOI: 10.1039/c6cp03564g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 06/13/2016] [Indexed: 11/21/2022]
Abstract
The control and understanding of the chemical and physical properties of quantum dots (QDs) demands detailed surface characterization. However, probing the immediate interface between the inorganic core and the ligands is still a major challenge. Here we show that using cross-polarization magic angle spinning (MAS) NMR, unprecedented information can be obtained on the surface ligands of Cd3P2 and InP QDs. The resonances of fragments which are usually challenging to detect like methylene or methyl near the surface, can be observed with our approach. Moreover, ligands such as hydroxyl and ethoxide which have so far never been detected at the surface can be unambiguously identified. This NMR approach is versatile, applicable to any phosphides and highly sensitive since it remains effective for identifying quantities as low as a few percent of surface atoms.
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Affiliation(s)
- Edwin A Baquero
- LPCNO (Laboratoire de Physique et Chimie des Nano-Objets), Université de Toulouse, INSA, UPS, CNRS, 135, avenue de Rangueil, F-31077 Toulouse, France.
| | - Wilfried-Solo Ojo
- LPCNO (Laboratoire de Physique et Chimie des Nano-Objets), Université de Toulouse, INSA, UPS, CNRS, 135, avenue de Rangueil, F-31077 Toulouse, France.
| | - Yannick Coppel
- Laboratoire de Chimie de Coordination, UPR-CNRS 8241, 205 route de Narbonne, 31077 Toulouse Cedex, France
| | - Bruno Chaudret
- LPCNO (Laboratoire de Physique et Chimie des Nano-Objets), Université de Toulouse, INSA, UPS, CNRS, 135, avenue de Rangueil, F-31077 Toulouse, France.
| | - Bernhard Urbaszek
- LPCNO (Laboratoire de Physique et Chimie des Nano-Objets), Université de Toulouse, INSA, UPS, CNRS, 135, avenue de Rangueil, F-31077 Toulouse, France.
| | - Céline Nayral
- LPCNO (Laboratoire de Physique et Chimie des Nano-Objets), Université de Toulouse, INSA, UPS, CNRS, 135, avenue de Rangueil, F-31077 Toulouse, France.
| | - Fabien Delpech
- LPCNO (Laboratoire de Physique et Chimie des Nano-Objets), Université de Toulouse, INSA, UPS, CNRS, 135, avenue de Rangueil, F-31077 Toulouse, France.
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Raskar DB, Eckert H, Ewald B, Kniep R. Characterization of local environments in crystalline borophosphates using single and double resonance NMR. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2008; 34:20-31. [PMID: 18723330 DOI: 10.1016/j.ssnmr.2008.07.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Accepted: 07/02/2008] [Indexed: 05/26/2023]
Abstract
(11)B and (31)P magic-angle spinning as well as (11)B{(31)P} and (31)P{(11)B} rotational echo double resonance (REDOR) NMR have been applied to characterize the local environments in the crystalline borophosphates K(3)[BP(3)O(9)(OH)(3)], NH(4)[ZnBP(2)O(8)] and Rb(3)[B(2)P(3)O(11)(OH)(2)]. Dipolar second moment values extracted from the REDOR curves at short evolution times (DeltaS/S(0) < or = 0.2) are in reasonable agreement with those calculated from the internuclear distances in the corresponding crystal structures. In particular, the method is found to be useful for distinguishing between boron and phosphorus local environments with different numbers of B-O-P connectivities, making REDOR a well-suited tool for medium-range order investigations in glasses.
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Affiliation(s)
- Devidas B Raskar
- Institut für Physikalische Chemie, Westfälische Wilhems-Universität Münster, Correnstrasse 30, D48149 Münster, Germany
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Hologne M, Bertani P, Azaïs T, Bonhomme C, Hirschinger J. 1H/31P distance determination by solid state NMR in multiple-spin systems. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2005; 28:50-6. [PMID: 15899581 DOI: 10.1016/j.ssnmr.2005.04.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2005] [Revised: 04/19/2005] [Accepted: 04/20/2005] [Indexed: 05/02/2023]
Abstract
The results of two techniques of dipolar recoupling, REDOR and CPMAS, are compared in the case of a coupled multiple-spin system. A fundamentally different behavior is observed for these two techniques. In REDOR, the terms associated with each interaction S-I(k) commute with each other and no truncation takes place so that each addition of spin I(k) causes a splitting with its dipolar frequency. In CPMAS, the flip-flop terms of the dipolar Hamiltonian do not commute with the dominant term from the strongly coupled spin pair so that the weak coupling terms from the neighboring spin I(k) are effectively truncated by the dominant pair interaction. Spin dynamics calculations are in agreement with the experimental data in a cubane shaped cluster.
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Affiliation(s)
- Maggy Hologne
- Institut de Chimie, FRE 2446 CNRS, Université Louis Pasteur, BP 296, 67008 Strasbourg Cedex, France
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Strojek W, Kalwei M, Eckert H. Dipolar NMR Strategies for Multispin Systems Involving Quadrupolar Nuclei: 31P{23Na} Rotational Echo Double Resonance (REDOR) of Crystalline Sodium Phosphates and Phosphate Glasses. J Phys Chem B 2004. [DOI: 10.1021/jp037041c] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Wenzel Strojek
- Institut für Physikalische Chemie, Westfälische Wilhelms−Universität Münster, Corrensstrasse 30, D-48149 Münster, Germany
| | - Martin Kalwei
- Institut für Physikalische Chemie, Westfälische Wilhelms−Universität Münster, Corrensstrasse 30, D-48149 Münster, Germany
| | - Hellmut Eckert
- Institut für Physikalische Chemie, Westfälische Wilhelms−Universität Münster, Corrensstrasse 30, D-48149 Münster, Germany
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Bertani P, Raya J, Hirschinger J. 19F/29Si rotational-echo double-resonance and heteronuclear spin counting under fast magic-angle spinning in fluoride-containing octadecasil. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2002; 22:188-203. [PMID: 12469810 DOI: 10.1006/snmr.2002.0081] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
19F/29Si rotational-echo double-resonance (REDOR) and theta-REDOR NMR techniques have been applied under fast magic-angle spinning to a powder sample of fluoride-containing octadecasil. Efficient dipolar recoupling was observed and the effect of finite pulse lengths was found to be negligible using standard radiofrequency field strengths. Moreover, the determined internuclear distance of the 19F-29Si spin pairs formed by the silicons in the D4R units (T-1 site) and the fluoride anions is in very good agreement with previous REDOR and Hartmann-Hahn cross-polarization measurements. Numerical simulation of the REDOR dephasing curves at both the T-1 and T-2 sites considering all fluoride anions in the infinite solid lattice clearly confirm the X-ray crystal structure of octadecasil. Heteronuclear spin-counting theta-REDOR experiments are found to be very useful to obtain direct insight into the local network of dipolar interactions. Indeed, while 19F-29Si pair-like behavior is confirmed at the T-1 site, multiple dipolar interactions are clearly evidenced at the T-2 site.
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Affiliation(s)
- Philippe Bertani
- Institut de Chimie, FRE 2446 CNRS, Université Louis Pasteur, BP 296, 67008 Strasbourg Cedex, France
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Fyfe CA, Brouwer DH, Lewis AR, Villaescusa LA, Morris RE. Combined solid state NMR and X-ray diffraction investigation of the local structure of the five-coordinate silicon in fluoride-containing as-synthesized STF zeolite. J Am Chem Soc 2002; 124:7770-8. [PMID: 12083931 DOI: 10.1021/ja012558s] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The local structure of the [SiO(4/2)F]- unit in fluoride-containing as-synthesized STF zeolite has been experimentally determined by a combination of solid-state NMR and microcrystal X-ray diffraction to be very close to trigonal bipyramidal. Because the fluoride ions are disordered over two sites, the resulting local structure of the [SiO(4/2)F]- unit from a conventional XRD refinement is an average between tetrahedral SiO(4/2) and five-coordinate [[SiO(4/2)F]-, giving an apparent F-Si distance longer than expected. The correct F-Si distance was determined by slow spinning MAS and fast spinning (19)F/(29)Si CP and REDOR solid-state NMR experiments and found to be between 1.72 and 1.79 A. In light of this, the X-ray structure was re-refined, including the disorder at Si3. The resulting local structure of the [SiO(4/2)F]- unit was very close to trigonal bipyramidal with a F-Si distance of 1.744 (6) A, in agreement with the NMR results and the prediction of Density Functional Theory calculations. In addition, further evidence for the existence of a covalent F-Si bond is provided by a (19)F-->(29)Si refocused INEPT experiment. The resonance for the five-coordinate species at -147.5 ppm in the (29)Si spectrum is a doublet due to the (19)F/(29)Si J-coupling of 165 Hz. The peaks in this doublet have remarkably different effective chemical shift anisotropies due to the interplay of the CSA, dipolar coupling, and J-coupling tensors. The distortions from tetrahedral geometry of the neighboring silicon atoms to the five-coordinate Si3 atom are manifested in increased delta(aniso) values. This information, along with F-Si distances measured by (19)F-->(29)Si CP experiments, makes it possible to assign half of the (29)Si resonances to unique tetrahedral sites. As well as determining the local geometry of the [SiO(4/2)F]- unit, the work presented here demonstrates the complementarity of the solid-state NMR and X-ray diffraction techniques and the advantages of using them together.
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Affiliation(s)
- Colin A Fyfe
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada.
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Chan JCC, Eckert H. C-rotational echo double resonance: Heteronuclear dipolar recoupling with homonuclear dipolar decoupling. J Chem Phys 2001. [DOI: 10.1063/1.1394217] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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9
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Fyfe CA, Lewis AR. Investigation of the Viability of Solid-State NMR Distance Determinations in Multiple Spin Systems of Unknown Structure. J Phys Chem B 1999. [DOI: 10.1021/jp9924530] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Colin A. Fyfe
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver B.C. V6T 1Z1 Canada
| | - Andrew R. Lewis
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver B.C. V6T 1Z1 Canada
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10
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Bertmer M, Eckert H. Dephasing of spin echoes by multiple heteronuclear dipolar interactions in rotational echo double resonance NMR experiments. SOLID STATE NUCLEAR MAGNETIC RESONANCE 1999; 15:139-152. [PMID: 10672938 DOI: 10.1016/s0926-2040(99)00050-8] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The application of rotational echo double resonance (REDOR) nuclear magnetic resonance (NMR) for accurate distance measurements has thus far been largely restricted to isolated heteronuclear two-spin systems. In the present paper, the informational content of REDOR curves is explored for systems characterized by multi-spin interactions. To this end, numerical REDOR simulations are presented for cases in which single observe spins S are dipolarly coupled to groups of spins I in distinct geometries. To develop the utility of REDOR for characterizing dipolar couplings in unknown and/or ill-defined geometries, the validity ranges and systematic errors of certain analytical approximations are studied. In the limit of short dipolar evolution times where 0 < deltaS/S0 < or = 0.2 to 0.3, the REDOR difference signal intensity increases approximately proportional to the square of the dipolar evolution time. Here, the curvature depends simply on the second moment M2 characterizing the overall strength of the heterodipolar coupling, irrespective of specific molecular geometries. Fitting experimental REDOR data in this manner produces slight systematic underestimates of M2. However, these errors tend to be counterbalanced by additional systematic errors made by neglecting weak couplings to more remote spins and distribution effects caused by disorder. Based on these findings, the results suggest a convenient method of obtaining site-resolved second moment information in disordered materials.
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Affiliation(s)
- M Bertmer
- Institut für Physikalische Chemie, Westfälische Wilhelms-Universit, Münster, Germany
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11
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Fyfe CA, Lewis AR, Chézeau JM. A comparison of NMR distance determinations in the solid state by cross polarization, REDOR, and TEDOR techniques. CAN J CHEM 1999. [DOI: 10.1139/v99-199] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Solid-state NMR distance determinations using Hartmann-Hahn cross polarization between spin-1/2 nuclei (19F/29Si) are reported. 19F –> 29Si polarization transfer for the T-1 silicon site in the clathrasil octadecasil shows an oscillatory behaviour as a function of the contact time. These oscillations were observed for non-spinning powder samples and also for different spinning speeds at the various MAS sideband matching conditions. Three analytical functions that allow efficient nonlinear least-square regression analyses of the experimental data to determine the internuclear distances for non-spinning powder samples as well as at the ±1 and ±2 MAS sideband matching conditions are reported. Using these functions, a 19F-29Si distance of 2.53 ± 0.04 Å was determined for the T-1 silicon in octadecasil from fitting of the oscillatory behaviour. This distance is in good agreement with that known from the X-ray structure and the previous 19F/29Si REDOR and TEDOR distance measurements. The advantages and limits of the different dipolar-based NMR techniques for heteronuclear distance determinations are examined and discussed.Key words: cross polarization (CP), NMR distance measurements, octadecasil, 19F-29Si distances, REDOR, TEDOR.
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12
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Chan JCC, Bertmer M, Eckert H. Site Connectivities in Amorphous Materials Studied by Double-Resonance NMR of Quadrupolar Nuclei: High-Resolution 11B ↔ 27Al Spectroscopy of Aluminoborate Glasses. J Am Chem Soc 1999. [DOI: 10.1021/ja983385i] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jerry C. C. Chan
- Contribution from the Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, Schlossplatz 7, D-48149 Münster, Germany
| | - Marko Bertmer
- Contribution from the Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, Schlossplatz 7, D-48149 Münster, Germany
| | - Hellmut Eckert
- Contribution from the Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, Schlossplatz 7, D-48149 Münster, Germany
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13
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Fretigny C. Analysis of the REDOR signal and inversion. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 1998; 133:273-280. [PMID: 9716468 DOI: 10.1006/jmre.1998.1462] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
An inversion of the REDOR signal to recover the dipolar couplings has been recently proposed [K. T. Mueller et al., Chem. Phys. Lett. 242, 535 (1995)]: The corresponding integral transform was performed by tabulation of the kernel followed by numerical integration. After explicit determination of the inverse REDOR kernel by the Mellin transform method, we propose an alternative inversion method based on Fourier transforms. Representation of the inverse REDOR kernel by its asymptotic expansion reveals that the inverse REDOR operator is essentially a weighted sum of a cosine transform and of its derivative. Consequently, known properties of Fourier transforms can easily be transposed to the REDOR inversion, allowing for a precise discussion of the value of the method. Moreover, the first term of the asymptotic expansion leading to a derivative of a cosine transform, the REDOR inversion is found to be extremely sensitive to noise, thus considerably reducing the useful part of the theoretical dipolar window. Copyright 1998 Academic Press.
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Fyfe CA, Lewis AR, Chézeau JM, Grondey H. 19F/29Si Distance Determinations in Fluoride-Containing Octadecasil from Solid-State NMR Measurements. J Am Chem Soc 1997. [DOI: 10.1021/ja9701873] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Colin A. Fyfe
- Contribution from the Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1
| | - Andrew R. Lewis
- Contribution from the Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1
| | - Jean Michel Chézeau
- Contribution from the Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1
| | - Hiltrud Grondey
- Contribution from the Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1
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Klug CA, Lee PL, Lee ISH, Kreevoy MM, Yaris R, Schaefer J. Structure of a Dihydrated, Strongly Hydrogen-Bonded Crystal. J Phys Chem B 1997. [DOI: 10.1021/jp971146w] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Christopher A. Klug
- Department of Chemistry, Washington University, St. Louis, Missouri 63130; Department of Science Education, Kangweon National University, Korea; and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - Patricia Lani Lee
- Department of Chemistry, Washington University, St. Louis, Missouri 63130; Department of Science Education, Kangweon National University, Korea; and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - I.-S. H. Lee
- Department of Chemistry, Washington University, St. Louis, Missouri 63130; Department of Science Education, Kangweon National University, Korea; and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - Maurice M. Kreevoy
- Department of Chemistry, Washington University, St. Louis, Missouri 63130; Department of Science Education, Kangweon National University, Korea; and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - Robert Yaris
- Department of Chemistry, Washington University, St. Louis, Missouri 63130; Department of Science Education, Kangweon National University, Korea; and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - Jacob Schaefer
- Department of Chemistry, Washington University, St. Louis, Missouri 63130; Department of Science Education, Kangweon National University, Korea; and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
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McDowell LM, Barkan D, Wilson GE, Schaefer J. Structural constraints on the complex of elongation factor Tu with magnesium guanosine diphosphate from rotational-echo double-resonance NMR. SOLID STATE NUCLEAR MAGNETIC RESONANCE 1996; 7:203-210. [PMID: 9050158 DOI: 10.1016/s0926-2040(96)01270-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Rotational-echo, double-resonance (REDOR) NMR measurements of 31P-15N dipolar couplings have been made on a complex of Mg guanosine diphosphate (MgGDP) with uniformly 15N-labeled elongation factor Tu. The complex was embedded in a lyophilized buffer glass. The observed 15N REDOR dephasing by 31P was accounted for quantitatively by distances from 15N of Gly23 and Lys24 to P alpha and P beta of MgGDP as determined by X-ray crystallography of MgGDP complex formed using an elongation factor Tu that is missing a 15 residue loop in the vicinity of the binding site.
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Affiliation(s)
- L M McDowell
- Department of Chemistry, Washington University, St. Louis, MO 63130, USA
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Abstract
Solid-state NMR experiments have recently provided a number of biochemical insights: motionally averaged 2H lineshapes have shown that the motion of a backbone loop protecting a protein binding site is not ligand gated; isotropic 13C chemical shifts of freeze-quenched enzyme-ligand intermediates have revealed mechanistic details of reaction pathways; multiple heteronuclear distance determinations have characterized the binding-site geometry of a 46 kDa noncrystalline enzyme complex; and homonuclear recoupling experiments have established that insoluble amyloid fibrils form a pleated beta sheet.
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Affiliation(s)
- L M McDowell
- Department of Chemistry, Washington University, St Louis, MO 63130, USA
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