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Kharkov BB, Corkery RW, Dvinskikh SV. Phase transitions and chain dynamics of surfactants intercalated into the galleries of naturally occurring clay mineral magadiite. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:7859-7866. [PMID: 24921951 DOI: 10.1021/la501898x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We investigate conformational dynamics and phase transitions of surfactant molecules confined in the layered galleries of the organo-modified, natural polysilicate clay, magadiite. We have shown that our approach to studying this class of materials is capable of delivering detailed information on the molecular mobility of the confined molecules. From the analysis of the measured heteronuclear dipolar couplings, the orientational order parameters of the C-H bonds along the hydrocarbon chain have been determined. Three phases have been observed in the nanocomposite, characterized by distinct dynamical states of the surfactant. At room temperature, restricted mobility of the molecules led to the adoption of an essentially all-trans conformation by the chains. This behavior can be described by a model incorporating small-angle wobbling around the long molecular axes of the chains. Upon heating, dynamic transformation takes place, resulting in a rotator type solid phase where molecules in extended all-trans conformations undergo fast and unrestricted rotation about their respective symmetry axes. The second phase transition is associated with chain melting and the onset of translational dynamics and results in an essentially liquid-crystalline-like state of the organic component. The mobility of the surfactant is one of the key factors facilitating the efficient penetration of macromolecules in the process of preparing of polymer/organoclay nanocomposites. The exploration of dynamic properties of the functionalizing organic layer should provide important input into the improved design of new organic-inorganic hybrid materials.
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Affiliation(s)
- Boris B Kharkov
- Royal Institute of Technology KTH , Department of Chemistry, Teknikringen 36, SE-10044 Stockholm, Sweden
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Cifelli M, Domenici V, Veracini CA. Recent advancements in understanding thermotropic liquid crystal structure and dynamics by means of NMR spectroscopy. Curr Opin Colloid Interface Sci 2013. [DOI: 10.1016/j.cocis.2013.03.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Kharkov BB, Chizhik VI, Dvinskikh SV. Sign-sensitive determination of heteronuclear dipolar coupling to spin-1 by selective decoupling. J Chem Phys 2012; 137:234902. [DOI: 10.1063/1.4771697] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Lobo NP, Prakash M, Narasimhaswamy T, Ramanathan KV. Determination of 13C Chemical Shift Anisotropy Tensors and Molecular Order of 4-Hexyloxybenzoic Acid. J Phys Chem A 2012; 116:7508-15. [DOI: 10.1021/jp302291u] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nitin P. Lobo
- Department of Physics, Indian Institute of Science, Bangalore-560012, India
| | - M. Prakash
- Chemical Lab & Polymer Lab, CSIR-Central Leather Research Institute, Adyar, Chennai-600 020, India
| | - T. Narasimhaswamy
- Chemical Lab & Polymer Lab, CSIR-Central Leather Research Institute, Adyar, Chennai-600 020, India
| | - K. V. Ramanathan
- NMR Research Center, Indian Institute of Science, Bangalore-560012, India
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Zhang R, Chen Y, Chen T, Sun P, Li B, Ding D. Accessing Structure and Dynamics of Mobile Phase in Organic Solids by Real-Time T1C Filter PISEMA NMR Spectroscopy. J Phys Chem A 2012; 116:979-84. [DOI: 10.1021/jp2078902] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Rongchun Zhang
- School of Physics, Nankai University, Tianjin 300071, People's Republic of China
| | - Yuzhu Chen
- Key Laboratory of Functional Polymer Materials, Ministry of Education, College of Chemistry, Nankai University, Tianjin 300071, People's Republic of China
| | - Tiehong Chen
- Key Laboratory of Functional Polymer Materials, Ministry of Education, College of Chemistry, Nankai University, Tianjin 300071, People's Republic of China
| | - Pingchuan Sun
- Key Laboratory of Functional Polymer Materials, Ministry of Education, College of Chemistry, Nankai University, Tianjin 300071, People's Republic of China
| | - Baohui Li
- School of Physics, Nankai University, Tianjin 300071, People's Republic of China
| | - Datong Ding
- School of Physics, Nankai University, Tianjin 300071, People's Republic of China
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Gopinath T, Mote KR, Veglia G. Proton evolved local field solid-state nuclear magnetic resonance using Hadamard encoding: theory and application to membrane proteins. J Chem Phys 2011; 135:074503. [PMID: 21861572 DOI: 10.1063/1.3622604] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
NMR anisotropic parameters such as dipolar couplings and chemical shifts are central to structure and orientation determination of aligned membrane proteins and liquid crystals. Among the separated local field experiments, the proton evolved local field (PELF) scheme is particularly suitable to measure dynamically averaged dipolar couplings and give information on local molecular motions. However, the PELF experiment requires the acquisition of several 2D datasets at different mixing times to optimize the sensitivity for the complete range of dipolar couplings of the resonances in the spectrum. Here, we propose a new PELF experiment that takes the advantage of the Hadamard encoding (HE) to obtain higher sensitivity for a broad range of dipolar couplings using a single 2D experiment. The HE scheme is obtained by selecting the spin operators with phase switching of hard pulses. This approach enables one to detect four spin operators, simultaneously, which can be processed into two 2D spectra covering a broader range of dipolar couplings. The advantages of the new approach are illustrated for a U-(15)N NAL single crystal and the U-(15)N labeled single-pass membrane protein sarcolipin reconstituted in oriented lipid bicelles. The HE-PELF scheme can be implemented in other multidimensional experiments to speed up the characterization of the structure and dynamics of oriented membrane proteins and liquid crystalline samples.
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Affiliation(s)
- T Gopinath
- Department of Biochemistry, Molecular Biology, and Biophysics, Minneapolis, Minnesota 55455, USA
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Kalaivani S, Narasimhaswamy T, Das BB, Lobo NP, Ramanathan K. Phase Characterization and Study of Molecular Order of a Three-Ring Mesogen by 13C NMR in Smectic C and Nematic Phases. J Phys Chem B 2011; 115:11554-65. [DOI: 10.1021/jp203388v] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- S. Kalaivani
- Polymer Laboratory, Central Leather Research Institute (Council of Scientific & Industrial Research, CSIR), Adyar, Chennai 600 020, India
| | - T. Narasimhaswamy
- Polymer Laboratory, Central Leather Research Institute (Council of Scientific & Industrial Research, CSIR), Adyar, Chennai 600 020, India
| | - Bibhuti B. Das
- Department of Physics and ‡NMR Research Center, Indian Institute of Science, Bangalore 560 012, India
| | - Nitin P. Lobo
- Department of Physics and ‡NMR Research Center, Indian Institute of Science, Bangalore 560 012, India
| | - K.V. Ramanathan
- Department of Physics and ‡NMR Research Center, Indian Institute of Science, Bangalore 560 012, India
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Lobo NP, Ramanathan KV. Sensitivity Enhancement in Solid-State Separated Local Field NMR Experiments by the Use of Adiabatic Cross-Polarization. J Phys Chem Lett 2011; 2:1183-1188. [PMID: 26295323 DOI: 10.1021/jz200345q] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Measurement of dipolar couplings using separated local field (SLF) NMR experiment is a powerful tool for structural and dynamics studies of oriented molecules such as liquid crystals and membrane proteins in aligned lipid bilayers. Enhancing the sensitivity of such SLF techniques is of significant importance in present-day solid-state NMR methodology. The present study considers the use of adiabatic cross-polarization for this purpose, which is applied for the first time to one of the well-known SLF techniques, namely, polarization inversion spin exchange at the magic angle (PISEMA). The experiments have been carried out on a single crystal of a model peptide, and a dramatic enhancement in signal-to-noise up to 90% has been demonstrated.
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Affiliation(s)
- Nitin P Lobo
- †Department of Physics and ‡NMR Research Centre, Indian Institute of Science, Bangalore 560012, India
| | - Krishna V Ramanathan
- †Department of Physics and ‡NMR Research Centre, Indian Institute of Science, Bangalore 560012, India
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Gopinath T, Veglia G. Improved Resolution in Dipolar NMR Spectra Using Constant Time Evolution PISEMA Experiment. Chem Phys Lett 2010; 494:104-110. [PMID: 20814452 PMCID: PMC2929988 DOI: 10.1016/j.cplett.2010.05.078] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The atomic structure of small molecules and polypeptides can be attained from anisotropic NMR parameters such as dipolar couplings (DC) and chemical shifts (CS). Separated local field experiments resolve DC and CS correlations into two dimensions. However, crowded NMR spectra represent a significant obstacle for the complete resolution of these anisotropic parameters. Using the PISEMA (Polarization Inversion Spin Exchange at the Magic Angle) experiment as a foundation, we designed new pulse schemes that use a constant time evolution in the dipolar (indirect) dimension to measure DC and CS correlations at high resolution. We demonstrated this approach on a 4-pentyl-4'-cyanobiphenyl (5CB) liquid crystal sample, achieving a resolution enhancement ranging from 30 to 60 % for the resonances in the dipolar dimension. These new experiments open the possibility of obtaining significant resolution enhancement for multidimensional NMR experiments carried out on oriented liquid crystalline samples as well as oriented membrane proteins.
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Affiliation(s)
- T. Gopinath
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455
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Affiliation(s)
- Shi Bai
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
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Jian F, Wang J, Xiao H, Zhao P, Sun P, Huang L. [60]Fullerene metal complexes with large effective two-photon absorption cross-section. Dalton Trans 2010; 39:11045-52. [DOI: 10.1039/b926935e] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Gopinath T, Veglia G. Sensitivity enhancement in static solid-state NMR experiments via single- and multiple-quantum dipolar coherences. J Am Chem Soc 2009; 131:5754-6. [PMID: 19351170 PMCID: PMC3481552 DOI: 10.1021/ja900096d] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present a new method for enhancing the sensitivity in static solid-state NMR experiments for a gain in signal-to-noise ratio of up to 40%. This sensitivity enhancement is different from the corresponding solution NMR sensitivity enhancement schemes and is achieved by combining single- and multiple-quantum dipolar coherences. While this new approach is demonstrated for the polarization inversion spin exchange at magic angle (PISEMA) experiment, it can be generalized to the other separated local field experiments for solid-state NMR spectroscopy. This method will have a direct impact on solid-state NMR spectroscopy of liquid crystals as well as of membrane proteins aligned in lipid membranes.
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Affiliation(s)
- T. Gopinath
- Department of Chemistry andDepartment of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Gianluigi Veglia
- Department of Chemistry andDepartment of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
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