Proton-decoupled deuterium NMR study of an asymmetric liquid crystal dimer having two nematic phases

Proton-decoupled deuterium NMR spectra were obtained for an asymmetric liquid crystal dimer 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl)hexane (CB6OCB) containing a single -CD_{2}- group. The sample has two nematic liquid crystal phases: a twist-bend nematic, N_{TB}, at the lowest temperature followed by a uniaxial nematic, N_{U}, on increasing the temperature. Proton decoupling reduces the linewidths of the peaks in the deuterium spectrum from kHz to ∼100Hz, enabling quadrupolar splittings, Δν, to be obtained with enhanced precision as well as the dipolar coupling between deuterium nuclei within the CD_{2} group, hence enhancing the information content.

Phase transitions in a high magnetic field of an odd, symmetric liquid crystal dimer having two nematic phases, N_{U} and N_{TB}, studied by NMR spectroscopy

Both ^{1}H and ^{13}C NMR spectra have been obtained in a static magnetic field of 23.5 T on a bent-shaped dimer molecule, 1^{''},7^{''}-bis(4-cyanobiphenyl-4'-yl) nonane (CB9CB), which shows the sequence of liquid crystal phases twist-bend nematic, N_{TB}, and uniaxial nematic, N_{U}, before entering the isotropic phase. The ^{1}H spectra are used to locate the temperature at which the sample melts to form a twist-bend nematic, T_{CrN_{TB}}, and then T_{N_{U}I} when the isotropic phase is entered, both in a magnetic field of 23.5 T, and to compare these with those measured at the Earth's field. The differences between these transition temperatures are found to be zero within the error in their measurement, in stark contrast to previous measurements by Salili et al. [Phys. Rev. Lett. 116, 217801 (2016)10.1103/PhysRevLett.116.217801]. In the isotropic phase in the presence of the field the sample exists in a paranematic phase in which the molecules of CB9CB are partially ordered. The ^{1}H and ^{13}C NMR spectra in the paranematic phase are used to measure the critical temperature T* below which this phase is unstable. The spectra are also used to study the structure, molecular orientational order, and distribution of molecular conformations in the paranematic phase.

Publisher's Note: ^{13}C NMR study of the director distribution adopted by the modulated nematic phases formed by liquid-crystal dimers with odd numbers of atoms in their spacers [Phys. Rev. E 96, 062702 (2017)]

This corrects the article DOI: 10.1103/PhysRevE.96.062702.

^{13}C NMR study of the director distribution adopted by the modulated nematic phases formed by liquid-crystal dimers with odd numbers of atoms in their spacers

The orientational order of the molecules in the bent mesogen CB6OCB has been studied throughout the range of temperature stability of both the N_{U} and N_{TB} liquid-crystal phases by ^{13}C NMR spectroscopy. These spectra provide local order parameters for the para axes of both of the nonequivalent cyanobiphenyl groups and show how they change on entering the twist-bend nematic phase. A key feature of the order parameters is a weak, but clear maximum in the temperature variation of the order parameter prior to the N_{TB} phase. This suggests that the directors in both the N_{U} and N_{TB} phases are tilted with respect to the magnetic field of the spectrometer. Significantly the conformational states of the spacer are comparable in both phases, although the low temperature nematic is chiral but not that at high temperature. It is proposed that the higher temperature, tilted phase could be the splay-bend nematic phase.

Measurement of 14N quadrupole couplings in biomolecular solids using indirect-detection 14N solid-state NMR with DNP

Insights into protein structure through the determination of ¹⁴N quadrupolar interactions using magic-angle spinning dynamic nuclear polarization NMR.

Similarities and differences between molecular order in the nematic and twist-bend nematic phases of a symmetric liquid crystal dimer

Carbon-13 chemical shift anisotropies reveal an unusual temperature dependence of the order parameters, S_zz, for the difluoroterphenyl groups in the normal nematic, N and the twist-bend nematic, N_TB, phases.

Benzene at 1GHz. Magnetic field-induced fine structure

The deuterium NMR spectrum of benzene-d6 in a high field spectrometer (1GHz protons) exhibits a magnetic field-induced deuterium quadrupolar splitting Δν. The magnitude of Δν observed for the central resonance is smaller than that observed for the (13)C satellite doublets Δν'. This difference, Δ(Δν)=Δν'-Δν, is due to unresolved fine structure contributions to the respective resonances. We determine the origins of and simulate this difference, and report pulse sequences that exploit the connectivity of the peaks in the (13)C and (2)H spectra to determine the relative signs of the indirect coupling, JCD, and Δν. The positive sign found for Δν is consonant with the magnetic field biasing of an isolated benzene molecule-the magnetic energy of the aromatic ring is lowest for configurations where the C6 axis is normal to the field. In the neat liquid the magnitude of Δν is decreased by the pair correlations in this prototypical molecular liquid.

Highly efficient cellular uptake of c-myb antisense oligonucleotides through specifically designed polymeric nanospheres

c-myb antisense oligonucleotides (AS ODNs) were reversibly immobilized to a novel polymeric core shell nanosphere and their cellular uptake and inhibitory effect on HL60 leukemia cell proliferation studied. The nanosphere surface was so designed as to directly bind ODNs via ionic interactions and reversibly release them inside the cells. Compared with the cellular uptake of free oligonucleotide, the use of AS ODN (immobilized to the nanospheres) produced a 50-fold increase in the intracellular concentration. Specifically, a single dose of 320 nM of AS ODN immobilized to the nanospheres was capable of inhibiting HL60 cell proliferation with the same degree of efficiency obtained using a 50-fold higher dose of free AS ODN. Flow cytometric experiments with fluoresceinated ODNs showed a temperature-dependent uptake, which was detectable as early as 2 h after the beginning of treatment. The inhibitory effect on cell proliferation was maintained for up to 8 days of culture. Moreover, the level of c-Myb protein decreased by 24% after 2 days and by 60% after 4 days of treatment, thus indicating a continuous and sustained release of non-degraded AS ODN from the nanospheres inside the cells.

Comparison of bronchodilator effects of Duovent and Reproterol in patients with chronic reversible airway obstruction

The bronchodilator effect of Duovent (a combination of a beta-2-agonist, fenoterol, and an anticholinergic, ipratropium bromide) was compared with that of Reproterol (a pharmacological hybrid which presents both resorcinol and theophylline portions) in 16 patients suffering from chronic reversible airway obstruction. Each of the 16 patients (14 males and 2 females, mean age 65.8 years) had a baseline FEV1 ranging from 30 to 70% of their predicted values (CECA values) (mean value +/- SE of the group: 1,238 +/- 78 ml), which increased at least 15% after the inhalation of two puffs of 400 micrograms fenoterol (percent increase of the group: 26.5 +/- 2%, mean +/- SE). This single-blind study was carried out on 3 different days, between 8:30 a.m. and 4:30 p.m. After measurement of the baseline functional parameters [FVC (forced vital capacity), FEV1 (1-second forced expiratory volume), and FEF25-75 (forced expiratory flow between 25 and 75% of vital capacity)], each patient was given two puffs of placebo the 2nd day, and either of Duovent (200 micrograms of fenoterol and 80 micrograms of ipratropium bromide) or of Reproterol (1 mg) the 1st or the 3rd day, at random. The measurements of functional parameters were repeated after 30, 120, 240, 360 and 480 min. Blood pressure, heart rate and possible side effects were recorded at the same time. Both Duovent and Reproterol, at all times, produced a statistically significant increase in FEV1 and FEF25-75.(ABSTRACT TRUNCATED AT 250 WORDS)