Ultrafast multidimensional Laplace NMR for a rapid and sensitive chemical analysis

Traditional nuclear magnetic resonance (NMR) spectroscopy relies on the versatile chemical information conveyed by spectra. To complement conventional NMR, Laplace NMR explores diffusion and relaxation phenomena to reveal details on molecular motions. Under a broad concept of ultrafast multidimensional Laplace NMR, here we introduce an ultrafast diffusion-relaxation correlation experiment enhancing the resolution and information content of corresponding 1D experiments as well as reducing the experiment time by one to two orders of magnitude or more as compared with its conventional 2D counterpart. We demonstrate that the method allows one to distinguish identical molecules in different physical environments and provides chemical resolution missing in NMR spectra. Although the sensitivity of the new method is reduced due to spatial encoding, the single-scan approach enables one to use hyperpolarized substances to boost the sensitivity by several orders of magnitude, significantly enhancing the overall sensitivity of multidimensional Laplace NMR

Breast cancer management pathways during the COVID-19 pandemic: outcomes from the UK ‘Alert Level 4’ phase of the B-MaP-C study

Abstract: Background: The B-MaP-C study aimed to determine alterations to breast cancer (BC) management during the peak transmission period of the UK COVID-19 pandemic and the potential impact of these treatment decisions. Methods: This was a national cohort study of patients with early BC undergoing multidisciplinary team (MDT)-guided treatment recommendations during the pandemic, designated ‘standard’ or ‘COVID-altered’, in the preoperative, operative and post-operative setting. Findings: Of 3776 patients (from 64 UK units) in the study, 2246 (59%) had ‘COVID-altered’ management. ‘Bridging’ endocrine therapy was used (n = 951) where theatre capacity was reduced. There was increasing access to COVID-19 low-risk theatres during the study period (59%). In line with national guidance, immediate breast reconstruction was avoided (n = 299). Where adjuvant chemotherapy was omitted (n = 81), the median benefit was only 3% (IQR 2–9%) using ‘NHS Predict’. There was the rapid adoption of new evidence-based hypofractionated radiotherapy (n = 781, from 46 units). Only 14 patients (1%) tested positive for SARS-CoV-2 during their treatment journey. Conclusions: The majority of ‘COVID-altered’ management decisions were largely in line with pre-COVID evidence-based guidelines, implying that breast cancer survival outcomes are unlikely to be negatively impacted by the pandemic. However, in this study, the potential impact of delays to BC presentation or diagnosis remains unknown

Liquid crystal NMR: director dynamics and small solute molecules

Abstract The subjects of this thesis are the dynamics of liquid crystals in external electric and magnetic fields as well as the magnetic properties of small molecules, both studied by liquid crystal nuclear magnetic resonance (LC NMR) spectroscopy. Director dynamics of a liquid crystal 5CB in external magnetic and electric fields was studied by deuterium NMR and spectral simulations. A new theory was developed to explain the peculiar oscillations observed in the experimental spectra collected during fast director rotation. A spectral simulation program based on this new theory was developed and the outcome of the simulations was compared with the experimental results to verify the tenability of the theory. In the studies on the properties of small solute molecules, LC NMR was utilised to obtain information about anisotropic nuclear magnetic interaction tensors. The nuclear magnetic shielding tensor was studied in methyl halides, the spin-spin coupling tensor in methyl mercury halides and the quadrupolar coupling tensor in deuterated benzenes. The effects of small-amplitude molecular motions and solvent interactions on the obtained parameters were considered in each case. Finally, the experimental results were compared to the corresponding computational NMR parameters calculated in parallel with the experimental work

Low-concentration measurements of nuclear spin-induced optical rotation using SABRE hyperpolarization

Abstract Nuclear spin-induced optical rotation (NSOR) is a promising phenomenon for molecular structure elucidation due to its sensitivity to electronic structure near atomic nuclei. It is the only experimentally verified nuclear magneto-optic effect (NMOE), so far observed usually in neat liquids or in concentrated binary mixtures, with the proportion of the minor component at least 10%. We report a method to extend the lower-concentration range of NSOR measurements by 2 orders of magnitude by employing continuous-flow SABRE (signal amplification by reversible exchange) hyperpolarization. This approach significantly increases the sensitivity of NSOR and enables its detection in dilute samples, as demonstrated with measurements of NSOR of 90 mmol/L solutions of pyridine and pyrazine. The results are compared with first-principles calculations, and good agreement is found. The possibility to measure low-concentration solutions significantly extends the pool of samples available for further studies of NMOEs

Determination of Phenolic Hydroxyl Groups in Technical Lignins by Ionization Difference Ultraviolet Spectrophotometry (∆ε-IDUS method)

The amount of hydroxyl groups, particularly phenolic, is one of the most important parameters in lignins, as it is an indicator of lignin reactivity. Ultraviolet (UV) Spectrophotometry is a simple and inexpensive method for determining phenolic hydroxyls in lignin. Ionization Difference Ultraviolet Spectrophotometry (Δε-method) relies on the analysis of solubilized lignin at neutral and alkaline conditions with a UV spectrophotometer. We added a slope analysis to the ∆ε-method and dubbed the resulting method ∆ε-IDUS (Ionization Difference UV Spectrophotometry). We assessed the reliability of ∆ε-IDUS by studying the well-known Indulin AT lignin. Additionally, ∆ε-IDUS was applied to a previously uncharacterized milox lignin. When compared to 13C-NMR, ∆ε-IDUS underestimated the amount of phenolic hydroxyls for Indulin AT, possibly due to neglecting second phenolic hydroxyls in some lignin units, which resist ionization because of steric hindrance. Nevertheless, the results agreed with previously reported values and confirm that ∆ε-IDUS is useful to screen lignins based on their phenolic hydroxyl group content

Deuterium NMR spectroscopy and field-induced director dynamics in liquid crystals

Deuterium NMR spectroscopy together with spectral simulations have been used to investigate the field-induced director dynamics in a nematic liquid crystal, 4-pentyl-4'-cyanobiphenyl (5CB), confined in a slab between two electrodes. The NMR spectra have been measured when turning the electric field on and turning it off. Measurements were also made at different temperatures to explore how the temperature effects the director relaxation. At higher temperatures, some complications arise as peculiar oscillations are observed in the spectra. With spectral simulation this phenomena is shown to result from the relaxation of the director on a timescale comparable to that of the experiment which is the effective spin-spin relaxation time. The simulated spectra are compared with the experimental spectra for the specifically deuteriated 5CB-d(2)

Cellulose nanofibers from nonbleached and hydrogen peroxide bleached acidic thiourea treated sawdust

Abstract Here a single-step acidic thiourea delignification without and with sequential hydrogen peroxide bleaching were used as a pre-treatment for producing low-lignin-containing cellulose nanofibers (LCNF) and bleached cellulose nanofibers (BCNF), respectively. Without bleaching, LCNF contained 7 wt% lignin, resulting in a slightly yellowish color in both the water dispersion and film. Despite low gravimetric yield of nanosize fibers, 23 wt% after microfluidization, the LCNF films exhibited notable mechanical strength, with a tensile strength of 174 MPa and a modulus of 11 GPa. Upon introducing an additional bleaching step, the color was eliminated, reducing the lignin content to 3 wt%. This adjustment also led to a significant increase in the gravimetric yield of nanofibers, reaching 78 wt%. The BCNF films demonstrated even higher mechanical performance, with a tensile strength of 207 MPa and a modulus of 12 GPa. LCNF film exhibited a higher contact angle (≈70°) than BCNF (≈60°), presumably due to the higher lignin content of the nonbleached pulp. Furthermore, hot pressing of the films at 150 °C for 18 min substantially enhanced the wet strength of the films by over 50%, attributed to the residual lignin

Aqueous modification of chitosan with itaconic acid to produce strong oxygen barrier film

Abstract In this study, the chemical modification of chitosan using itaconic acid as a natural-based unsaturated dicarboxylic acid was investigated. In an aqueous environment, the amine group of chitosan reacts with itaconic acid to produce a chitosan derivative with pyrrolidone-4-carboxylic acid group. On the basis of the elemental analysis, 15% of the amine groups of chitosan reacted, thus creating modified chitosan with amine and carboxylic acid functionalities. Due to the presence of amine and carboxylic acid groups, the surface charge properties of the chitosan were notably altered after itaconic acid modification. In an aqueous solution, the modified chitosan exhibited zwitterionic properties, being cationic at low pH and turning anionic when the pH was increased over 6.5, whereas the original chitosan remained cationic until pH 9. Furthermore, it was demostrated that the modified chitosan was suitable for the preparation of a self-standing film with similarly high transparency but notably higher mechanical strength and oxygen barrier properties compared to a film made from the original chitosan. In addition, the thermal stability of the modified chitosan film was higher than that of the original chitosan film, and the modified chitosan exhibited flame-retardant properties