scholarly journals The potential of magnetisation transfer NMR to monitor the dissolution process of cellulose in cold alkali

Cellulose ◽  
2019 ◽  
Vol 26 (18) ◽  
pp. 9403-9412 ◽  
Author(s):  
Maria Gunnarsson ◽  
Merima Hasani ◽  
Diana Bernin
Keyword(s):  
Hydrophobic Interactions ◽  
Dissolution Process ◽  
Mechanistic Study ◽  
Dissolution Mechanism ◽  
Hydroxyl Groups ◽  
Similar Amount ◽  
Magnetisation Transfer ◽  
Promising Alternative ◽  
Nmr Methods ◽  
Increasing Temperature

Abstract Cellulose is the most important biopolymer on earth and, when derived from e.g. wood, a promising alternative to for example cotton, which exhibits a large environmental burden. The replacement depends, however, on an efficient dissolution process of cellulose. Cold aqueous alkali systems are attractive but these solvents have peculiarities, which might be overcome by understanding the acting mechanisms. Proposed dissolution mechanisms are for example the breakage of hydrophobic interactions and partly deprotonation of the cellulose hydroxyl groups. Here, we performed a mechanistic study using equimolar aqueous solutions of LiOH, NaOH and KOH to elucidate the dissolution process of microcrystalline cellulose (MCC). The pH was the highest for KOH(aq) followed by NaOH(aq) and LiOH(aq). We used a combination of conventional and advanced solution-state NMR methods to monitor the dissolution process of MCC by solely increasing the temperature from − 10 to 5 °C. KOH(aq) dissolved roughly 25% of the maximum amount of MCC while NaOH(aq) and LiOH(aq) dissolved up to 70%. Water motions on nanoscale timescales present in non-frozen water, remained unaffected on the addition of MCC. Magnetisation transfer (MT) NMR experiments monitored the semi-rigid MCC as a function of temperature. Interestingly, although NaOH(aq) and LiOH(aq) were able to dissolve a similar amount at 5 °C, MT spectra revealed differences with increasing temperature, suggesting a difference in the swollen state of MCC in LiOH(aq) already at − 10 °C. Furthermore, MT NMR shows a great potential to study the water exchange dynamics with the swollen and semi-rigid MCC fraction in these systems, which might give valuable insights into the dissolution mechanism in cold alkali.

Silica Sol-Gel Microbead Encapsulation as a Novel Delivery Method for Symbiotic Microbes

2020 ◽  
Author(s):  
Luke Elissiry ◽  
Jingwen Sun ◽  
Ann M. Hirsch ◽  
Chong Liu
Keyword(s):  
Plant Growth ◽  
Crop Yields ◽  
Sol Gel ◽  
Plate Count ◽  
Similar Amount ◽  
Delivery Method ◽  
Hormone Production ◽  
Promising Alternative ◽  
Synthetic Fertilizer ◽  
Inorganic Nanomaterials

Synthetic fertilizer is responsible for the greatly increased crop yields that have enabled worldwide industrialization. However, the production and use of such fertilizers are environmentally unfriendly and unsustainable; synthetic fertilizers are produced via non-renewable resources and fertilizer runoff causes groundwater contamination and eutrophication. A promising alternative to synthetic fertilizer is bacterial inoculation. In this process, a symbiotic relationship is formed between a crop and bacteria species that can fix nitrogen, solubilize phosphorus, and stimulate plant hormone production. The bacteria carrier developed here aims to maintain bacteria viability while in storage, protect bacteria while encapsulated, and provide a sustained and controllable bacterial release. This novel bacterial delivery method utilizes inorganic nanomaterials, silica microbeads, to encapsulate symbiotic bacteria. These microbeads, which were produced with aqueous, non-toxic precursors, are sprayed directly onto crop seeds and solidify on the seeds as a resilient silica matrix. The bacterial release from the carrier was found by submerging coated seeds in solution to simulate degradation in soil environments, measuring the number of bacteria released by the plate count technique, and comparing the carrier to seeds coated only in bacteria. The carrier’s effectiveness to enhance plant growth was determined through greenhouse plant assays with alfalfa (<i>Medicago sativa</i>) plants and the nitrogen-fixing <i>Sinorhizobium meliloti</i> Rm1021 strain. When compared to bacteria-only inoculation, the silica microbead carrier exhibited significantly (P < 0.05) increased holding capacity of viable bacteria and increased plant growth by a similar amount, demonstrating the capability of inorganic nanomaterials for microbial delivery. The carrier presented in this work has potential applications for commercial agriculture and presents an opportunity to further pursue more sustainable agricultural practices.

Silica Sol-Gel Microbead Encapsulation as a Novel Delivery Method for Symbiotic Microbes

2020 ◽  
Author(s):  
Luke Elissiry ◽  
Jingwen Sun ◽  
Ann M. Hirsch ◽  
Chong Liu
Keyword(s):  
Plant Growth ◽  
Crop Yields ◽  
Sol Gel ◽  
Plate Count ◽  
Similar Amount ◽  
Delivery Method ◽  
Hormone Production ◽  
Promising Alternative ◽  
Synthetic Fertilizer ◽  
Inorganic Nanomaterials

Synthetic fertilizer is responsible for the greatly increased crop yields that have enabled worldwide industrialization. However, the production and use of such fertilizers are environmentally unfriendly and unsustainable; synthetic fertilizers are produced via non-renewable resources and fertilizer runoff causes groundwater contamination and eutrophication. A promising alternative to synthetic fertilizer is bacterial inoculation. In this process, a symbiotic relationship is formed between a crop and bacteria species that can fix nitrogen, solubilize phosphorus, and stimulate plant hormone production. The bacteria carrier developed here aims to maintain bacteria viability while in storage, protect bacteria while encapsulated, and provide a sustained and controllable bacterial release. This novel bacterial delivery method utilizes inorganic nanomaterials, silica microbeads, to encapsulate symbiotic bacteria. These microbeads, which were produced with aqueous, non-toxic precursors, are sprayed directly onto crop seeds and solidify on the seeds as a resilient silica matrix. The bacterial release from the carrier was found by submerging coated seeds in solution to simulate degradation in soil environments, measuring the number of bacteria released by the plate count technique, and comparing the carrier to seeds coated only in bacteria. The carrier’s effectiveness to enhance plant growth was determined through greenhouse plant assays with alfalfa (<i>Medicago sativa</i>) plants and the nitrogen-fixing <i>Sinorhizobium meliloti</i> Rm1021 strain. When compared to bacteria-only inoculation, the silica microbead carrier exhibited significantly (P < 0.05) increased holding capacity of viable bacteria and increased plant growth by a similar amount, demonstrating the capability of inorganic nanomaterials for microbial delivery. The carrier presented in this work has potential applications for commercial agriculture and presents an opportunity to further pursue more sustainable agricultural practices.

scholarly journals Study on the Dissolution Mechanism of Cellulose by ChCl-Based Deep Eutectic Solvents

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 278 ◽  
Author(s):  
Heng Zhang ◽  
Jinyan Lang ◽  
Ping Lan ◽  
Hongyan Yang ◽  
Junliang Lu ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Oxalic Acid ◽  
Deep Eutectic Solvents ◽  
Solvent System ◽  
Hydroxyl Group ◽  
Regenerated Cellulose ◽  
Dissolution Mechanism ◽  
Hydroxyl Groups ◽  
Type I ◽  
Hydrogen Bond Donor

Four deep eutectic solvents (DESs), namely, glycerol/chlorocholine (glycerol/ChCl), urea/ChCl, citric acid/ChCl, and oxalic acid/ChCl, were synthesized and their performance in the dissolution of cellulose was studied. The results showed that the melting point of the DESs varied with the proportion of the hydrogen bond donor material. The viscosity of the DESs changed considerably with the change in temperature; as the temperature increased, the viscosity decreased and the electrical conductivity increased. Oxalic acid/ChCl exhibited the best dissolution effects on cellulose. The microscopic morphology of cellulose was observed with a microscope. The solvent system effectively dissolved the cellulose, and the dissolution method of the oxalic acid/ChCl solvent on cellulose was preliminarily analyzed. The ChCl solvent formed new hydrogen bonds with the hydroxyl groups of the cellulose through its oxygen atom in the hydroxyl group and its nitrogen atom in the amino group. That is to say, after the deep eutectic melt formed an internal hydrogen bond, a large number of remaining ions formed a hydrogen bond with the hydroxyl groups of the cellulose, resulting in a great dissolution of the cellulose. Although the cellulose and regenerated cellulose had similar structures, the crystal form of cellulose changed from type I to type II.

Structure of β-casein

1979 ◽  
Vol 46 (2) ◽  
pp. 281-282 ◽  
Author(s):  
Shunrokuro Arima ◽  
Ryoya Niki ◽  
Kenji Takase
Keyword(s):  
Electron Microscopy ◽  
Phosphate Buffer ◽  
Analytical Ultracentrifugation ◽  
Hydrophobic Interactions ◽  
Gel Filtration ◽  
Random Coil ◽  
Free Energies ◽  
Gel Filtration Chromatography ◽  
Increasing Temperature

SUMMARYThe temperature and concentration dependent association of β-casein was studied by means of viscometry, gel filtration chromatography, electron microscopy, analytical ultracentrifugation and UV difference spectrophotometry. Degrees of polymerization of 12, 22 and 49 and free energies of association of –21, –23 and – 25 kJ/mole monomer were found at temperatures of 10, 15 and 20 °C respectively in 0·2 M Na phosphate buffer pH 6·7.Monomeric β-casein was not a completely random coil but became more compact with increasing temperature, due to hydrophobic interactions.

Transport of Methane Confined in Nanoscale Silica Pores

2011 ◽  
Vol 347-353 ◽  
pp. 3425-3429
Author(s):  
Qing Yin Zhang ◽  
Dong Lai Qi
Keyword(s):  
Natural Gas ◽  
Molecular Simulation ◽  
Amorphous Silica ◽  
Diffusion Coefficients ◽  
Nanoporous Materials ◽  
Surface Structures ◽  
Compressed Natural Gas ◽  
Promising Alternative ◽  
Increasing Temperature ◽  
Diffusion Behaviors

Natural gas (methane is the primary constituent) adsorbed on nanoporous materials is a promising alternative to compressed natural gas as a cleaning fuel. To understand the transport of methane confined in a nanoscale pore is useful for developing and optimizing some related industry processes. Equilibrium molecular simulation were carried out to study the transport behaviors of methane confined in two types silica pores, a cristobalite silica pore and an amorphous silica pore. Many factors, such as temperatures, densities of methane and surface structures of pore, which could affect the transport of methane, were examined in simulations. Simulations calculated the diffusion coefficients of methane at different densities and temperatures. The detailed microscopic structures of pores have a great correlation with the diffusion behaviors of methane. The diffusion coefficients of methane increased with increasing temperature, but decreased with the increase of density.

scholarly journals Strategy for Designing Selective Lysosomal Acid α-Glucosidase Inhibitors: Binding Orientation and Influence on Selectivity

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2843 ◽  
Author(s):  
Atsushi Kato ◽  
Izumi Nakagome ◽  
Mizuki Hata ◽  
Robert J. Nash ◽  
George W. J. Fleet ◽  
...  
Keyword(s):  
Alkyl Chain ◽  
Hydrophobic Interactions ◽  
Antiviral Agents ◽  
Design Strategy ◽  
Docking Study ◽  
Piperidine Ring ◽  
Hydroxyl Groups ◽  
Storage Site ◽  
Molecular Docking Study ◽  
Lysosomal Acid

Deoxynojirimycin (DNJ) is the archetypal iminosugar, in which the configuration of the hydroxyl groups in the piperidine ring truly mimic those of d-glucopyranose; DNJ and derivatives have beneficial effects as therapeutic agents, such as anti-diabetic and antiviral agents, and pharmacological chaperones for genetic disorders, because they have been shown to inhibit α-glucosidases from various sources. However, attempts to design a better molecule based solely on structural similarity cannot produce selectivity between α-glucosidases that are localized in multiple organs and tissues, because the differences of each sugar-recognition site are very subtle. In this study, we provide the first example of a design strategy for selective lysosomal acid α-glucosidase (GAA) inhibitors focusing on the alkyl chain storage site. Our design of α-1-C-heptyl-1,4-dideoxy-1,4-imino-l-arabinitol (LAB) produced a potent inhibitor of the GAA, with an IC50 value of 0.44 µM. It displayed a remarkable selectivity toward GAA (selectivity index value of 168.2). A molecular dynamic simulation study revealed that the ligand-binding conformation stability gradually improved with increasing length of the α-1-C-alkyl chain. It is noteworthy that α-1-C-heptyl-LAB formed clearly different interactions from DNJ and had favored hydrophobic interactions with Trp481, Phe525, and Met519 at the alkyl chain storage pocket of GAA. Moreover, a molecular docking study revealed that endoplasmic reticulum (ER) α-glucosidase II does not have enough space to accommodate these alkyl chains. Therefore, the design strategy focusing on the shape and acceptability of long alkyl chain at each α-glucosidase may lead to the creation of more selective and practically useful inhibitors.

Hydrogen-Bonded Macrocluster Formation of 1-Propanol and 2-Propanol on Silica Surfaces

2003 ◽  
Vol 56 (10) ◽  
pp. 1071 ◽  
Author(s):  
Masashi Mizukami ◽  
Kazue Kurihara
Keyword(s):  
Hydrogen Bonding ◽  
Long Range ◽  
Hydroxyl Groups ◽  
Similar Amount ◽  
Colloidal Probe ◽  
Force Microscopy ◽  
Silica Surfaces ◽  
Atomic Force ◽  
Aggregation Structure ◽  
Hydrogen Bonded

We have investigated the adsorption of 1- and 2-propanol on silica surfaces from their mixtures with cyclohexane using a combination of colloidal probe atomic force microscopy, adsorption excess isotherms, and FTIR spectroscopy in the ATR mode. The adsorption isotherm indicated that a similar amount of each alcohol was adsorbed on the silica surfaces. FTIR spectra revealed that 1-propanol adsorbed on the surface employing hydrogen-bonding between the surface silanol groups and the hydroxyl groups of 1-propanol as well as between the hydroxyl groups of 1-propanol in the form of a linear zig-zag structure. This structure is similar to the linear hydrogen-bonded structure of ethanol, which we have found on silica and called a ‘surface molecular macrocluster’ (M. Mizukami, M. Moteki, K. Kurihara, J. Am. Chem. Soc. 2002, 124, 12 889). The contact of adsorbed layers of 1-propanol on the opposed silica surfaces brought about the long-range attraction extending to 69 ± 9 nm at 0.1 mol-% 1-propanol. 2-Propanol was also adsorbed on the surface by the hydrogen-bonding, however, in the form of a cyclic structure. No long-range attraction was observed in the 2-propanol/cyclohexane binary liquids at 0.1–6.0 mol-%. The absence of a long-range attraction can be explained by the cyclic aggregation structure of 2-propanol on the surface.

scholarly journals Potential of Kale and Lettuce Residues as Natural Adsorbents of the Carcinogen Aflatoxin B1 in a Dynamic Gastrointestinal Tract-Simulated Model

Toxins ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 771
Author(s):  
Alma Vázquez-Durán ◽  
María de Jesús Nava-Ramírez ◽  
Daniel Hernández-Patlán ◽  
Bruno Solís-Cruz ◽  
Víctor Hernández-Gómez ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Gastrointestinal Tract ◽  
Aflatoxin B1 ◽  
Electrostatic Interactions ◽  
Hydrophobic Interactions ◽  
Maximum Adsorption Capacity ◽  
Promising Alternative ◽  
Simulated Model ◽  
Dipole Interactions ◽  
Natural Adsorbents

Adsorption of the carcinogen aflatoxin B1 (AFB1) onto agro-waste-based materials is a promising alternative over conventional inorganic binders. In the current study, two unmodified adsorbents were eco-friendly prepared from kale and lettuce agro-wastes. A dynamic gastrointestinal tract-simulated model was utilized to evaluate the removal efficiency of the sorptive materials (0.5%, w/w) when added to an AFB1-contaminated diet (100 µg AFB1/kg). Different characterization methodologies were employed to understand the interaction mechanisms between the AFB1 molecule and the biosorbents. Based on adsorption results, the biosorbent prepared from kale was the best; its maximum adsorption capacity was 93.6%, which was significantly higher than that of the lettuce biosorbent (83.7%). Characterization results indicate that different mechanisms may act simultaneously during adsorption. Non-electrostatic (hydrophobic interactions, dipole-dipole interactions, and hydrogen bonding) and electrostatic interactions (ionic attractions) together with the formation of AFB1-chlorophyll complexes appear to be the major influencing factors driving AFB1 biosorption.

scholarly journals First Principles Mechanistic Study of Self-Limiting Oxidative Adsorption of Remote Oxygen Plasma During the Atomic Layer Deposition of Alumina

2018 ◽  
Author(s):  
Glen N. Fomengia ◽  
Michael Nolan ◽  
Simon D. Elliott
Keyword(s):  
Atomic Layer Deposition ◽  
First Principles ◽  
Density Functional ◽  
Atomic Layer ◽  
Molecular Water ◽  
Mechanistic Study ◽  
Hydroxyl Groups ◽  
Layer Deposition ◽  
Surface Intermediates ◽  
By Products

Plasma-enhanced atomic layer deposition (ALD) of metal oxides is a rapidly gaining interest especially in the electronics industry because of its numerous advantages over the thermal process. However, the underlying reaction mechanism is not sufficiently understood, particularly regarding saturation of the reaction and densification of the film. In this work, we employ first principles density functional theory (DFT) to determine the predominant reaction pathways, surface intermediates and by-products formed when constituents of O<sub>2</sub>-plasma or O<sub>3</sub> adsorb onto a methylated surface typical of TMA-based alumina ALD. The main outcomes are that a wide variety of barrierless and highly exothermic reactions can take place. This leads to the spontaneous production of various by-products with low desorption energies and also of surface intermediates from the incomplete combustion of –CH<sub>3</sub> ligands. Surface hydroxyl groups are the most frequently observed intermediate and are formed as a consequence of the conservation of atoms and charge when methyl ligands are initially oxidized (rather than from subsequent re-adsorption of molecular water). Anionic intermediates such as formates are also commonly observed at the surface in the simulations. Formaldehyde, CH<sub>2</sub>O, is the most frequently observed gaseous by-product. Desorption of this by-product leads to saturation of the redox reaction at the level of two singlet oxygen atoms per CH<sub>3</sub> group, where the oxidation state of C is zero, rather than further reaction with oxygen to higher oxidation states. We conclude that the self-limiting chemistry that defines ALD comes about in this case through the desorption by-products with partially-oxidised carbon. The simulations also show that densification occurs when ligands are removed or oxidised to intermediates, indicating that there may be an inverse relationship between Al/O coordination numbers in the final film and the concentration of chemically-bound ligands or intermediate fragments covering the surface during each ALD pulse. Therefore reactions that generate a bare surface Al will produce denser films in metal oxide ALD.

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