Determination of the three-dimensional structure for weakly aligned biomolecules by NMR spectroscopy

Shahkhatuni, Astghik A.

doi:10.1070/rc2002v071n12abeh000757

Cited by 9 publications

(4 citation statements)

References 327 publications

(488 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recently, the order parameters of mixtures of 1P10Cl or 1P10Br and various concentrations of water or different alcohols were calculated and correlated with the phase structures. , The order parameters were found to be near 10 −2 , much lower than the values commonly encountered for nonionic, thermotropic liquid-crystalline phases. With the development of weak alignment techniques for three-dimensional structure determination of molecules by NMR spectroscopy, − it has became increasingly important to find weakly aligning media for molecules soluble in organic solvents. Most of the applications to date have concentrated on the structures of biomolecules, and most of the weakly aligning systems currently in use are aqueous.…”

Section: Introductionmentioning

confidence: 99%

Designing Amphotropic Smectic Liquid Crystals Based on Phosphonium Salts for Partial Ordering of Solutes as Monitored by NMR Spectroscopy

Shahkhatuni

Weiss

2009

J. Phys. Chem. B

View full text Add to dashboard Cite

The ordering parameters of selected solutes from NMR spectroscopic measurements have been assessed in the thermotropic and amphotropic smectic liquid-crystalline phases of a wide structural range of phosphonium salts with three equivalent long n-alkyl chains, one shorter chain, and various anions. The nature of the added liquids that convert the salts to amphotropic phasesalcohols and other small organic moleculesand their concentrations have been determined. These factors are correlated with the NMR-derived parameters in order to understand how the phases can be optimized to maximize information about the solutes. The various salts cover a range of liquid crystallinity from -40 to 100 degrees C. The phosphonium salts are easily aligned in the strong magnetic fields of the spectrometers. In several of the systems, a coexistence of isotropic and anisotropic phases is observed over a wide range of temperatures. The order parameters of the amphotropic liquid-crystalline phases vary from high to very low values, and some of the systems provide good spectral resolution for the solute molecules. Also, structural and orientational parameters of a model molecule, (13)C-enriched acetonitrile, have been calculated in various systems in order to evaluate more precisely the applicability of the host systems for determining solute structures by NMR. The results, in toto, indicate that several of the phosphonium salts are very promising as hosts to determine solute structures.

show abstract

Section: Introductionmentioning

confidence: 99%

Designing Amphotropic Smectic Liquid Crystals Based on Phosphonium Salts for Partial Ordering of Solutes as Monitored by NMR Spectroscopy

Shahkhatuni

Weiss

2009

J. Phys. Chem. B

View full text Add to dashboard Cite

show abstract

“…Aqueous-based lyotropic liquid crystals (N.B. ‘bicellar’ media) and compressed hydrogels have been exploited for this purpose to a much greater extent than ordered media with organic liquids because the order parameters of the organic-based systems are usually too high to yield simple spectra of solutes. – This report includes our efforts to develop nonaqueous, nonpolymeric media with low order parameters for the purpose of 3-dimensional structural analyses of organic solute molecules.…”

Section: Introductionmentioning

confidence: 99%

Room-Temperature and Low-Ordered, Amphotropic-Lyotropic Ionic Liquid Crystal Phases Induced by Alcohols in Phosphonium Halides

Shahkhatuni

Somashekhar

et al. 2008

Langmuir

View full text Add to dashboard Cite

Tri- n-decylmethylphosphonium chloride and bromide ( 1P10X) salts are not liquid crystalline. However, mesophases are induced by adding very small amounts of an alcohol or water. The temperature ranges of the induced smectic A 2 (SmA 2) liquid-crystalline phases can be very broad and the onset temperatures can be below room temperature depending upon the concentration of the alcohol or water and the structure of the alcohol. At least one molar equivalent of hydroxyl groups is necessary to convert the 1P10X completely into a liquid crystal. Strong association between the hydroxyl groups of an alcohol or water and the head groups of the 1P10X is indicated by spectroscopic, diffraction, and thermochemical data. Unlike many other smectic phases, those of the 1P10X/alcohol complexes are easily aligned in strong magnetic fields and the order parameters of selectively deuterated alcohols as measured by (2)H NMR spectroscopy, approximately 10 (-2), are much lower than the values found when the host is a commonly employed thermotropic liquid crystal. The dependence of the specific values of the order parameters on temperature, the nature of the halide anion, and the structure and concentration of the alcohol are reported. In sum, a detailed picture is presented to explain how and why an alcohol or water induces liquid crystallinity in the 1P10X salts. The data also provide a blueprint for designing media with even lower order parameters that can be hosts to determine the conformations and shapes of guest molecules.

show abstract

“…[1][2][3] In general, these structures, calculated using the simplest RDC interpretation models, show good agreement with their X-ray counterparts. [3][4][5][6] In contrast, structural parameters calculated from NMR spectra of small molecules in thermotropic liquid crystalline solvents sometimes display substantial disagreement with one another, despite the use of more advanced interpretation schemes and the high precision of the individual measurements. More-over, they sometimes show large discrepancies from the expected values, either from theoretical predictions or from other structural methods, such as diffraction experiments and microwave spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

“…Historically, structural NMR spectroscopists have used thermotropic liquid crystals rather than lyotropic ones due to the high solubility and alignment of many small molecules in these solvents. However, in recent studies, the three-dimensional structures have been calculated from orientation-dependent NMR parameters, such as residual dipolar couplings (RDC), of weakly aligned biomolecules in lyotropic liquid crystalline solvents. − In general, these structures, calculated using the simplest RDC interpretation models, show good agreement with their X-ray counterparts. − …”

Section: Introductionmentioning

confidence: 99%

NMR Studies of ¹³C-Iodomethane: Different Behavior in Thermotropic and Lyotropic Liquid Crystals

et al. 2004

View full text Add to dashboard Cite

High-resolution NMR spectra of 13C-iodomethane dissolved in thermotropic and lyotropic liquid crystalline solvents have been used to measure 1H−H and 13C−1H dipolar couplings. The ratio of these two couplings, which is a function of the H−C−H bond angle in 13C-iodomethane, is, in general, different from that expected from the known molecular structure; solvent−solute interactions in liquid crystalline solutions are responsible for this difference. In thermotropic liquid crystalline solutions, the apparent bond angle deviation (Δθa) increases with decreasing molecular ordering. In contrast, in lyotropic liquid crystals, no significant spectral aberration has been observed. These results indicate a fundamental physicochemical difference between the intermolecular interactions that prevail in thermotropic and lyotropic liquid crystals.

show abstract

Determination of the three-dimensional structure for weakly aligned biomolecules by NMR spectroscopy

Cited by 9 publications

References 327 publications

Designing Amphotropic Smectic Liquid Crystals Based on Phosphonium Salts for Partial Ordering of Solutes as Monitored by NMR Spectroscopy

Designing Amphotropic Smectic Liquid Crystals Based on Phosphonium Salts for Partial Ordering of Solutes as Monitored by NMR Spectroscopy

Room-Temperature and Low-Ordered, Amphotropic-Lyotropic Ionic Liquid Crystal Phases Induced by Alcohols in Phosphonium Halides

NMR Studies of ¹³C-Iodomethane: Different Behavior in Thermotropic and Lyotropic Liquid Crystals

Contact Info

Product

Resources

About

Determination of the three-dimensional structure for weakly aligned biomolecules by NMR spectroscopy

Cited by 9 publications

References 327 publications

Designing Amphotropic Smectic Liquid Crystals Based on Phosphonium Salts for Partial Ordering of Solutes as Monitored by NMR Spectroscopy

Designing Amphotropic Smectic Liquid Crystals Based on Phosphonium Salts for Partial Ordering of Solutes as Monitored by NMR Spectroscopy

Room-Temperature and Low-Ordered, Amphotropic-Lyotropic Ionic Liquid Crystal Phases Induced by Alcohols in Phosphonium Halides

NMR Studies of 13C-Iodomethane: Different Behavior in Thermotropic and Lyotropic Liquid Crystals

Contact Info

Product

Resources

About

NMR Studies of ¹³C-Iodomethane: Different Behavior in Thermotropic and Lyotropic Liquid Crystals