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:

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

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

The quadrupolar interaction experienced by the spin-1 14N nucleus is known to be extremely sensitive to local structure and dynamics. Furthermore, the 14N isotope is 99.6% naturally abundant, making it an attractive target for characterisation of nitrogen-rich biological molecules by solid-state NMR. In this study, dynamic nuclear polarization (DNP) is used in conjunction with indirect 14N detected solid-state NMR experiments to simultaneously characterise the quadrupolar interaction at multiple 14N sites in the backbone of the microcrystalline protein, GB3. Considerable variation in the quadrupolar interaction (>700 kHz) is observed throughout the protein backbone. The distribution in quadrupolar interactions observed reports on the variation in local backbone conformation and subtle differences in hydrogen-bonding; demonstrating a new route to the structural and dynamic analysis of biomolecules.

Monitoring diffuse volcanic degassing during volcanic unrests: the case of Campi Flegrei (Italy).

In volcanoes with active hydrothermal systems, diffuse CO2 degassing may constitute the primary mode of volcanic degassing. The monitoring of CO2 emissions can provide important clues in understanding the evolution of volcanic activity especially at calderas where the interpretation of unrest signals is often complex. Here, we report eighteen years of CO2 fluxes from the soil at Solfatara of Pozzuoli, located in the restless Campi Flegrei caldera. The entire dataset, one of the largest of diffuse CO2 degassing ever produced, is made available for the scientific community. We show that, from 2003 to 2016, the area releasing deep-sourced CO2 tripled its extent. This expansion was accompanied by an increase of the background CO2 flux, over most of the surveyed area (1.4 km2), with increased contributions from non-biogenic source. Concurrently, the amount of diffusively released CO2 increased up to values typical of persistently degassing active volcanoes (up to 3000 t d-1). These variations are consistent with the increase in the flux of magmatic fluids injected into the hydrothermal system, which cause pressure increase and, in turn, condensation within the vapor plume feeding the Solfatara emission.

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

The order parameter, Szz, where z is the para axis of the difluoroterphenyl groups in DTC5C9, has been obtained from chemical shift anisotropies measured by (13)C - {(1)H} NMR experiments at temperatures throughout the nematic, NU, and twist-bend nematic, NTB, phases shown by this compound. The order parameter temperature profiles are unusual in having a maximum value in the NU phase and then decreasing until the NTB phase is reached. There is a small discontinuity (∼2%) in Szz at TNNTB and then a gradual decrease until a new phase appears. This behaviour is interpreted as revealing a temperature-dependent tilting of local directors in both phases away from the applied magnetic field direction. In the enantiomorphic twist-bend phase this tilt is consistent with the structure of the phase as a helical arrangement of local directors, whilst in the high-temperature non-chiral nematic the tilt must involve a non-chiral arrangement. It is proposed that in both phases the tilting of directors has a common origin in the bent shape of the molecules.

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.

Procaterol metered aerosol in patients with chronic obstructive pulmonary disease.

The activity and tolerability of procaterol, a recently introduced beta 2-adrenergic drug, were evaluated in comparison with fenoterol and a placebo in a single blind, cross-over study, using a metered aerosol formulation. Twelve patients suffering from chronic obstructive pulmonary disease with reversible bronchial obstruction were enrolled. Before and 30, 120, 240, 360, 480 min after drug administration, forced vital capacity (FVC), forced expiratory volume at the first second, forced expiratory flow at 25-75% and 75-85% respectively of the FVC, thoracic gas volume and the specific airways conductance were calculated. Procaterol 20 mcg showed a significant bronchodilating activity as well as fenoterol 400 mcg. This activity was already significant within 30 min, achieved its maximum after two hours and lasted more than eight hours. Side-effects were complained of by 41% of patients treated with procaterol and by 50% treated with fenoterol; procaterol showed less cardiovascular effects than fenoterol.

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)