13C Cross-polarization Magic-angle Spinning NMR Research Articles

Solid-State NMR Characterization of Mefloquine Resinate Complexes Designed for Taste-Masking Pediatric Formulations

Mefloquine (MQ) is an antimalarial medication prescribed to treat or malaria prevention.. When taken by children, vomiting usually occurs, and new doses of medication frequently need to be taken. So, developing pediatric medicines using taste-masked antimalarial drug complexes is mandatory for the success of mefloquine administration. The hypothesis that binding mefloquine to an ion-exchange resin (R) could circumvent the drug’s bitter taste problem was proposed, and solid-state 13C cross-polarization magic angle spinning (CPMAS) NMR was able to follow MQ–R mixtures through chemical shift and relaxation measurements. The nature of MQ–R complex formation could then be determined. Impedimetric electronic tongue equipment also verified the resinate taste-masking efficiency in vitro. Variations in chemical shifts and structure dynamics measured by proton relaxation properties (e.g., T1ρH) were used as probes to follow the extension of mixing and specific interactions that would be present in MQ–R. A significant decrease in T1ρH values was observed for MQ carbons in MQ–R complexes, compared to the ones in MQ (from 100–200 ms in MQ to 20–50 ms in an MQ–R complex). The results evidenced that the cationic resin interacts strongly with mefloquine molecules in the formulation of a 1:1 ratio complex. Thus, 13C CPMAS NMR allowed the confirmation of the presence of a binding between mefloquine and polacrilin in the MQ–R formulation studied.

In Situ Multinuclear Magic-Angle Spinning NMR: Monitoring Crystallization of Molecular Sieve AlPO4-11 in Real Time.

Molecular sieves are crystalline three-dimensional frameworks with well-defined channels and cavities. They have been widely used in industry for many applications such as gas separation/purification, ion exchange, and catalysis. Obviously, understanding the formation mechanisms is fundamentally important. High-resolution solid-state NMR spectroscopy is a powerful method for the study of molecular sieves. However, due to technical challenges, the vast majority of the high-resolution solid-state NMR studies on molecular sieve crystallization are ex situ. In the present work, using a new commercially available NMR rotor that can withhold high pressure and high temperature, we examined the formation of molecular sieve AlPO4-11 under dry gel conversion conditions by in situ multinuclear (1H, 27Al, 31P, and 13C) magic-angle spinning (MAS) solid-state NMR. In situ high-resolution NMR spectra obtained as a function of heating time provide much insights underlying the crystallization mechanism of AlPO4-11. Specifically, in situ 27Al and 31P MAS NMR along with 1H → 31P cross-polarization (CP) MAS NMR were used to monitor the evolution of the local environments of framework Al and P, in situ 1H → 13C CP MAS NMR to follow the behavior of the organic structure directing agent, and in situ 1H MAS NMR to unveil the effect of water content on crystallization kinetics. The in situ MAS NMR results lead to a better understanding of the formation of AlPO4-11.

Influence of Air Humidity Level on the Structure and Mechanical Properties of Thermoplastic Starch-Montmorillonite Nanocomposite during Storage.

Thermoplastic starch (TPS) consisting of corn starch and glycerol as a plasticizer, and TPS-montmorillonite (MMT) nanocomposite were stored at room temperature in the air with relative humidities (RH) of 11, 55 and 85% for seven weeks. Mechanical testing and dynamic mechanical thermal analysis (DMTA) were performed to detect changes in their mechanical properties. Solid-state NMR spectroscopy monitoring the changes in molecular mobility in the samples provided an insight into relations between mechanical properties and local structure. The results of mechanical testing indicated that the addition of MMT results in the increase in the tensile strength and Young's modulus while elongation at break decreased, indicating the reinforcing effect of MMT. DMTA experiments revealed a decrease in glass transition temperature of starch-rich phase below room temperature for samples stored at higher RH (55 and 85%). This indicates that absorbed water molecules had additional plasticizing effect on starch resulting in higher mobility of starch chain segments. Recrystallization in these samples was deduced from the shape of cross-polarization magic-angle spinning 13C NMR spectra. The shape of broad-line 1H NMR spectra reflected changes in molecular mobility in the studied samples during seven weeks of storage and revealed that a high amount of water molecules impacts the starch intermolecular hydrogen bond density.

Structure of a Luminescent MOF-2 Derivative with a Core of Zn(II)-Terephthalate-Isoquinoline and Its Application in Sensing of Xylenes

A new blue photoluminescent 2D metal–organic framework, 1, with formula {[Zn2(μ2-BDC)2(iQ)2]}∞ has been synthesized in a high yield under solvothermal conditions by reacting Zn(II) ions with 1,4-benzenedicarboxylic acid (H2BDC) and isoquinoline (iQ) in DMF. Compound 1 was thoroughly characterized by single-crystal X-ray diffraction, solid-state cross-polarization magic-angle spinning 13C NMR, X-ray powder diffraction, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), and thermoanalysis. The crystal structure of 1 showed interpenetrated 2D frameworks consisting of dinuclear paddle-wheel cores Zn2; moreover, this material possessed thermostability up to 310 °C. The CPMAS 13C-NMR spectrum of 1 is consistent with the symmetry of the crystal structure. Luminescence studies showed that 1 strongly enhances its fluorescence emission in the presence of xylene isomers with a pronounced selectivity to p-xylene.

2-Mercaptopyrimidine-functionalized mesostructured silicas to develop electrochemical sensors for a rapid control of scopolamine in tea and herbal tea infusions

Mesostructured silicas were synthesized and chemically functionalized with a 2-mercaptopyrimidine (MPY)-derivative. Bare and functionalized silicas (MSU-2, HMS, SBA-15, MSU-2-MPY, HMS-MPY and SBA-15-MPY) were characterized by powder X-ray diffraction, nitrogen adsorption-desorption isotherms, transmission electron and scanning electron microscopy, 29Si and 13C cross-polarization magic-angle spinning NMR spectroscopy and elemental analysis, and used to prepare modified carbon paste electrodes (CPEs). The electrodes properties were studied using potassium ferrocyanide and scopolamine as probes employing cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Results proved that MPY groups on the silica surface were necessary to improve the sensitivity in the voltammetric determination of scopolamine. CPE modified with HMS-MPY exhibited higher peak current toward the oxidation of scopolamine, with a well-defined oxidation peak at + 1.1 V (vs. Ag/AgCl) in DPV. This fact can be attributed to the high electroactive area of this material, with 3 D wormhole-like channel structure that favored the scopolamine diffusion. Under optimum conditions, HMS-MPY-CPE exhibited a wider linearity range, from 0.9 to 200 μM, with a detection limit of 0.3 μM and good reproducibility by DPV. The developed sensor was successfully applied for a rapid determination of scopolamine in spiked tea and herbal tea infusion samples with good recoveries (between 83 ± 5 and 101 ± 1%).

Synthesis of anionic ionic liquids@TpBd-(SO3)2 for the selective adsorption of cationic dyes with superior capacity.

The discharge of industrial printing and dyeing wastewater is one of the main reasons for the increasing water shortage and deterioration. The treatment of dyestuff wastewater is an issue and needs to be urgently solved. In this work, anionic ionic liquid functional covalent organic materials (COMs) were firstly synthesized and used for the selective adsorption of cationic dyes. First, a series of sulfonic acid group (SO3H)-functionalized anionic TpPa-SO3, TpBd-(SO3)2, and TpCR-(SO3)2 were prepared, respectively, and then imidazole was grafted onto TpBd-(SO3)2 to obtain ImI@TpBd-(SO3)2. The full characterization using X-ray diffraction, FT-IR spectroscopy, 13C cross-polarization magic-angle spinning NMR spectroscopy, zeta-potentials, BET surface and pore analysis indicated that these COMs and ImI@TpBd-(SO3)2 exhibited different morphologies, porosities, and potentials. The effects of the type of dye, adsorption time, initial dye concentration, and pH on the adsorption of dyes on ImI@TpBd-(SO3)2 were systematically investigated, respectively. The results revealed that ImI@TpBd-(SO3)2 possessed good adsorption performance for nine different cationic dyes with adsorption capacities in the range from 2865.3 mg g−1 for methylene blue (MB) to 597.9 mg g−1 for basic orange 2 (BO), but little adsorption for anionic and neutral dyes, revealing charge selectivity. The adsorption ratio of ImI@TpBd-(SO3)2 for MB was as high as 74.0% at 10 min by using 1.0 mg material, owing to the post modification of TpBd-(SO3)2 with imidazole. The adsorption of MB on ImI@TpBd-(SO3)2 was pH dependent. The adsorption isotherm and kinetics fitted well with the Freundlich and pseudo second-order kinetic model, respectively. Finally, the very outstanding advantages of superior selective adsorption, desorption, convenient preparation, and low density of ImI@TpBd-(SO3)2 predicted its research and application potential in dye wastewater recovery.

Integrated analysis of modified Japanese cypress using solid-state NMR spectra and nuclear magnetic relaxation times

Acetylation and resin impregnation of Japanese cypress and subsequent heating of these modified cypresses were examined using an integrated analysis of solid-state NMR spectra and relaxation times. The 1H magic angle spinning NMR showed altered moisture balance after chemical and thermal modifications because of changed hydrophobicity. The 13C cross-polarization/magic angle spinning (CP-MAS) NMR spectra showed that acetylation predominately occurred for carbohydrates while phenol formaldehyde (PF) and melamine formaldehyde (MF) resins permeated all biomass constituents in cypress samples. Spin–lattice relaxation times in the laboratory frame, T1H and T1C, increased with chemical modifications although T1C decreased with the curing of both resins. In contrast, 1H spin–lattice relaxation in the rotation frame, T1ρH, increased with the curing as well as acetylation. The tendencies of relaxation times with curing suggested that faster molecular motions were suppressed in the MHz frequency range, and slower molecular motions were enhanced in the kHz frequency range, which generally matched with the signal changes in the 13C pulse saturation transfer/magic angle spinning NMR spectra. Scanning electron microscope observation showed different adhesion distribution between PF and MF resins, affecting the cellulose signals of 13C CP-MAS NMR and T1H change due to the curing.

Synthesis of Nitrogen-Rich Polymers by Click Polymerization Reaction and Gas Sorption Property.

Microporous organic polymers (MOPs) are promising materials for gas sorption because of their intrinsic and permanent porosity, designable framework, and low density. The introduction of nitrogen-rich building block in MOPs will greatly enhance the gas sorption capacity. Here, we report the synthesis of MOPs from the 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine unit and aromatic azides linkers by click polymerization reaction. Fourier transform infrared (FTIR) and solid-state 13C CP-MAS (Cross Polarization-Magic Angle Spinning) NMR confirm the formation of the polymers. CMOP-1 and CMOP-2 exhibit microporous networks with a BET (Brunauer–Emmett–Teller) surface area of 431 m2·g−1 and 406 m2·g−1 and a narrow pore size distribution under 1.2 nm. Gas sorption isotherms including CO2 and H2 were measured. CMOP-1 stores a superior CO2 level of 1.85 mmol·g−1 at 273 K/1.0 bar, and an H2 uptake of up to 2.94 mmol·g−1 at 77 K/1.0 bar, while CMOP-2, with its smaller surface area, shows a lower CO2 adsorption capacity of 1.64 mmol·g−1 and an H2 uptake of 2.48 mmol·g−1. In addition, I2 vapor adsorption was tested at 353 K. CMOP-1 shows a higher gravimetric load of 160 wt%. Despite the moderate surface area, the CMOPs display excellent sorption ability for CO2 and I2 due to the nitrogen-rich content in the polymers.

Silane-based hyper-cross-linked porous polymers and their applications in gas storage and water treatment

A series of novel silane-based hyper-cross-linked porous polymers was prepared through the Friedel–Crafts alkylation reaction of dimethyldiphenylsilane as the monomer and formaldehyde dimethyl acetal as the external cross-linker. The structures of the polymers were confirmed by FTIR and solid-state cross-polarization magic-angle spinning 13C NMR. We investigated the porous polymers with different ratios of dimethyldiphenylsilane to formaldehyde dimethyl acetal. Porous properties were determined by nitrogen, carbon dioxide and hydrogen adsorptions. The results revealed that the porous materials possessed surface areas from 742 to 1205 m2 g−1 with the increasing amount of formaldehyde dimethyl acetal. Moreover, this material exhibited high thermal stabilities, good CO2 capture, and H2 storage capacities. The material was also used as adsorbent for organic dyes in aqueous solution and showed an excellent adsorption capacity of 952 mg g−1 for Congo red dye. These results suggest that the silane-based hyper-cross-linked porous polymers are promising materials for CO2 capture, H2 storage, and water treatment.

Instrumental analyses of nanostructures and interactions with water molecules of biomass constituents of Japanese cypress

Nanostructures consisting of the biomass constituents of the denatured Japanese cypress (Chamaecyparis obtusa) were examined by instrumental analyses at multiple hierarchical levels. Delignification with NaClO2 solution smoothly proceeded to reveal a distorted cell by scanning electron microscopy; however, a trace amount of lignin still remained in the delignified sample according to attenuated total reflection infrared spectra (ATR-IR). Although hemicellulose could be removed by a treatment with NaOH solution, thermogravimetric analysis and 13C cross-polarization/magic angle spinning (CP-MAS) NMR showed a certain amount of hemicellulose remaining. Reaction of the delignified sample with NaOH solution produced a shrunken cell wall that consisted of cellulose with small amounts of lignin and hemicellulose, which were detected by ATR-IR and 13C CP-MAS NMR, respectively. These samples from which lignin and/or hemicellulose had been removed easily released water molecules, producing a decrease in the 1H signal intensity and longer 1H spin–lattice relaxation time (T1H) values in variable temperature 1H MAS NMR. The T1H values provided information about nano-scale molecular interaction difficult to obtain by other instrumental analyses and they greatly changed depending on the water content and ratio of the biomass constituents. The spin–lattice relaxation of all samples occurred via water molecules under humid conditions that provided sufficient water. Under heat-dried conditions, the spin–lattice relaxation mainly occurred via lignin for the samples with lignin remaining while it occurred via cellulose/hemicellulose for the samples without lignin. The variable temperature T1H analysis indicated that predominant spin–lattice relaxation route via lignin was caused by higher molecular mobility of lignin-containing samples compared with lignin-free samples.

Facile Method for Fluorescent Labeling of Starch Nanocrystal

Fluorescently labeled starch nanocrystal (FL-SNC) was synthesized using a simple, low-cost, and scalable two-step chemical modification process. Reactive amino groups were introduced onto the SNC surface through silanization with 3-aminopropyl triethoxysilane (APTES), and fluorescein isothiocyanate (FITC) groups were covalently attached through thiourea. Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, solid-state cross-polarization magic-angle spinning 13C NMR, UV–visible absorbance spectrophotometry, and fluorescence emission spectroscopy confirmed the successful introduction of the fluorescent groups. Transmission electron microscopy and X-ray diffraction data indicated that the dispersibility of FL-SNC was significantly improved, and the original crystallinity and morphology were retained. Compared with a mixture of uncoupled FITC and SNC, covalently connected FL-SNC displayed a more obvious fluorescence intensity and higher photostability. Furthermore, FL-SNC was biocompatib...

Large-Pore 3D Cubic Mesoporous (KIT-6) Hybrid Bearing a Hard–Soft Donor Combined Ligand for Enhancing U(VI) Capture: An Experimental and Theoretical Investigation

A preorganized tetradentate phenanthrolineamide (DAPhen) ligand with hard and soft donors combined in the same molecule has been found to possess high extraction ability toward actinides over lanthanides from acidic aqueous solution in our previous work. Herein we grafted phenanthrolineamide groups onto a large-pore three-dimensional cubic silica support by the reaction of DAPhen siloxane with KIT-6 substrate to prepare a novel uranium-selective sorbent, KIT-6-DAPhen. The as-synthesized sorbent was well-characterized by scanning electron microscopy, high-resolution transmission electron microscopy, N2 adsorption/desorption, X-ray diffraction, FT-IR, 13C cross-polarization magic-angle spinning NMR, and TGA techniques, which confirmed the consummation of the functionalization. Subsequently, the effects of contact time, solution pH, initial U(VI) concentration, and the presence of competing metal ions on the U(VI) sorption onto KIT-6-DAPhen sorbent were investigated in detail. It was found that KIT-6-DAPhen showed largely enhanced sorption capacity and excellent selectivity toward U(VI). The maximum sorption capacity of KIT-6-DAPhen at pH 5.0 reaches 328 mg of U/g of sorbent, which is superior to most of functionalized mesoporous silica materials. Density functional theory coupled with quasi-relativistic small-core pseudopotentials was used to explore the sorption interaction between U(VI) and KIT-6-DAPhen, which gives a sorption reaction of KIT-6-DAPhen + [UO2(H2O)5]2+ + NO3- ⇄ [UO2(KIT-6-DAPhen)(NO3)]+ + 5H2O. The findings of the present work provide new clues for developing new actinide sorbents by combining new ligands with various mesoporous matrixes.

Ionic π-Conjugated Polymer Networks by Catalyst-Free Polymerization, Photoluminescence and Gas Sorption Behavior

Four monomers of the bis(pyridyl)acetylene and bis[(pyridyl)ethynyl]benzene types containing either 2-pyridyl or 4-pyridyl groups are polymerized into respective networks of the conjugated polyelectrolyte (CPE) type by catalyst-free polymerization via activation with 1,4-bis(bromomethyl)benzene as quaternization agent (QA). Prepared CPE networks are characterized by elemental analysis (EA), TGA analysis, 13C cross-polarization magic-angle spinning NMR, IR, UV/vis, and photoluminescence spectroscopies. Highly cross-linked network structure containing both π-conjugated polyacetylene type chains and ionic alternating type chains is proposed. According to EA analysis, the mole ratio of units derived from monomer molecules and QA molecules is close to unity in all prepared networks. The CPE networks based on 4-pyridyl monomers exhibit strong photoluminescence in the visible region after irradiation with light of wavelength of 378 nm. Prepared CPE networks also show moderate efficiency in CO2 sorption up to 13.6 cm3 g−1 (STP) and exceptionally high ethanol vapor capture efficiency up to 24.5 wt% (293 K). The specific interactions of ionic network and adsorbed molecules and also temporary pores formation are assumed to play important role in sorption processes.

Preparation and characterisation of Ce:YAG -polycarbonate composites for white LED

Ce:YAG-polycarbonate composites were prepared with several amounts of Ce:YAG in the range 0.1–5 wt.% by using melt compounding. The structure and morphology of the composites were investigated by means of X-ray diffractometry and transmission electron microscopy. The optical properties of the composites were studied by using photoluminescence spectroscopy. The intermolecular interaction between the polymer and the filler surface was investigated using 13C cross-polarization magic-angle spinning NMR spectroscopy (13C {1H} CP-MAS NMR). The results showed that the dispersion of the particles in the polymer, and the optical properties, depend on the Ce:YAG amount. The composites were combined with a blue LED in order to test their performance in a white LED device. Results indicate that more suitable light is obtained using the Ce:YAG-PC composite loaded at 2 wt.%.

Concentration-dependant selective removal of Cr(III), Pb(II) and Zn(II) from aqueous mixtures using 5-methyl-2-thiophenecarboxaldehyde Schiff base-immobilised SBA-15

5-Methyl-2-thiophenecarboxaldehyde (MTC)-derived Schiff base was immobilised over SBA-15 (TS-SBA-15) via a two-step modification procedure. Initially, (3-aminopropyl)triethoxysilane (APTES) was heterogenised over SBA-15 (NH2-SBA-15), and the Schiff base formation was followed by a reaction with MTC in hot methanol. X-ray diffraction and transmission electron microscopy showed that the SBA-15, NH2-SBA-15 and TS-SBA-15 materials had mesoscopically ordered, hexagonal symmetry and well-defined morphologies. 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy revealed a change in the silicon environment during modification. The N2 sorption experiments showed that the material has a large surface area (623 m2 g−1), acceptable pore diameter (6.5 nm) and reasonable pore volume (1.23 cm3 g−1) to accommodate the guest molecules inside the pore channels. Organic functionalisation was determined successfully by Fourier transform infrared and 13C cross-polarisation magic-angle spinning NMR spectroscopy. The optimal condition for the removal of Cr(III), Pb(II) and Zn(II) from water was explored by varying the parameters, such as pH, stirring time, initial concentration and amount of adsorbent. The results suggested that TS-SBA-15 can achieve the adsorption maximum within 6 h at pH 6.5. The adsorbent exhibited moderate-to-good adsorption ability towards the three metal ions under these experimental conditions. The selective adsorption performance of TS-SBA-15 from binary mixture was examined by keeping equal concentrations of metal ions in the mixture. TS-SBA-15 was more selective towards Cr(III) ions from both the binary and ternary mixtures at pH 6.5. The effect of the metal ion concentration over mole adsorption selectivity in the ternary mixture was examined by doubling the concentration of at least one metal ion in the mixture. The result was compared with the ternary mixture containing equal concentrations of metal ions. The reusability test showed that TS-SBA-15 can be recycled for at least six consecutive cycles without losing its adsorption ability.

Solid-state characterization of sertraline base–β-cyclodextrin inclusion complex

Sertraline is one of the serotonin-specific reuptake inhibitors that is effective in treating several disorders such as major depression, obsessive–compulsive disorder, panic disorder, and social phobia. It is marketed in the form of its hydrochloride salt, which exhibits better solubility in water than its free base form. However, the absorption of sertraline through biological membranes could be improved by enhancing the solubility of its base because it is more hydrophobic than sertraline hydrochloride. To clarify the mechanism for the interaction of sertraline base with β-CD, it is important to study the basic interaction between the β-CD ring and sertraline base. Therefore, in this study, the currently used hydrochloride salt form was converted into the free base and β-CD was used as a model for β-CD derivatives to evaluate the interaction between β-CD and the sertraline base. The solid-state physicochemical characteristics of the sertraline–β-CD complex were investigated by the phase solubility method, differential scanning calorimetry, Fourier transform IR spectroscopy, FT-Raman spectroscopy, powder X-ray diffraction, and 13C cross-polarization magic-angle spinning NMR measurements. The results showed that sertraline base and β-CD form an inclusion complex, and the stoichiometric ratio of the solid-state sertraline base–β-CD complex is 1:1, which was estimated by the 1H NMR measurements of the complex dissolved in DMSO-d6.

Ce:Y3Al5O12–Poly(methyl methacrylate) Composite for White-Light-Emitting Diodes

A Ce:YAG-poly(methyl methacrylate) (PMMA) composite was prepared by using the melt compounding method. The structure and morphology were investigated by X-ray diffractometry, transmission electron microscopy, and small-angle X-ray scattering. The optical properties (emission, excitation, and fluorescence decay rate) of the composite were studied by using photoluminescence spectroscopy. The polymer–filler interactions were studied using 13C cross-polarization magic-angle spinning NMR spectroscopy (13C{1H} CP-MAS NMR). The results indicated that Ce:YAG particles are well-dispersed in the PMMA matrix without loss of their luminescence properties or significant spectral shift, thus suggesting that this composite can be valuable for advanced applications in white LED manufacture. A demonstration of its efficiency in white LED devices is also reported.

DFT, FT-Raman, FT-IR, solution and solid state NMR studies of 2,4-dimethoxyphenylboronic acid

The possible stable forms and molecular structures of 2,4-dimethoxyphenylboronic acid (2,4-dmpba) have been experimentally and theoretically studied using FT-IR, Raman and solution and solid state NMR spectroscopic methods. FT-IR and Raman spectra were recorded in the region of 4000–400 cm−1. 13C cross-polarization magic-angle spinning NMR and solution phase 1H, 13C and HETCOR NMR spectra of 2,4-dmpba ((CH3O)2C6H3B(OH)2) have been reported. The optimized geometric structures concerning to the minimum on the potential energy surface was investigated by Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional theory method together with 6-31++G(d,p) basis set. The vibrational wavenumbers and 1H, 13C NMR chemical shifts of 2,4-dmpba have been calculated by means of B3LYP density functional methods with 6-31++G(d,p) basis set. Reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated with scaled quantum mechanical (SQM) method. Comparison between the experimental and the theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting vibrational wavenumbers and nuclear magnetic shielding tensors. Furthermore, the cis–trans (ct) form of 2,4-dmpba with Cs point group has been found to be the most stable conformer.

Granule Structure and Distribution of Allomorphs in C-Type High-Amylose Rice Starch Granule Modified by Antisense RNA Inhibition of Starch Branching Enzyme

C-type starch, which is a combination of both A-type and B-type crystal starch, is usually found in legumes and rhizomes. We have developed a high-amylose transgenic line of rice (TRS) by antisense RNA inhibition of starch branching enzymes. The starch in the endosperm of this TRS was identified as typical C-type crystalline starch, but its fine granular structure and allomorph distribution remained unclear. In this study, we conducted morphological and spectroscopic studies on this TRS starch during acid hydrolysis to determine the distribution of A- and B-type allomorphs. The morphology of starch granules after various durations of acid hydrolysis was compared by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results showed that amorphous regions were located at the center part of TRS starch subgranules. During acid hydrolysis, starch was degraded from the interior of the subgranule to the outer surface, while the peripheral part of the subgranules and the surrounding band of the starch granule were highly resistant to acid hydrolysis. The spectroscopic changes detected by X-ray powder diffraction, 13C cross-polarization magic-angle spinning NMR, and attenuated total reflectance Fourier transform infrared showed that the A-type allomorph was hydrolyzed more rapidly than the B-type, and that the X-ray diffraction profile gradually changed from a native C-type to a CB-type with increasing hydrolysis time. Our results showed that, in TRS starch, the A-type allomorph was located around the amorphous region, and was surrounded by the B-type allomorph located in the peripheral region of the subgranules and the surrounding band of the starch granule. Thus, the positions of A- and B-type allomorphs in the TRS C-type starch granule differ markedly from those in C-type legume and rhizome starch.

ChemInform Abstract: Azo Pigments and Their Intermediates. A Reinvestigation of the Tetrazotization of 1,4-Diaminoanthraquinone.

The azotization of 1,4-diaminoanthraquinone (1) by n-amyl nitrite in glacial acetic was reinvestigated. The structure of a red-brown precipitate, which was previously identified as anthraquinone-1,4-tetrazonium dichloride (3) by Schaarschmidt, was found to be incorrect. In this work, we have identified the red-brown solid as 4-aminoanthraquinone-1-diazonium chloride (2), a diazotized product of 1. The yield of 2 was 80%. The tetrazonium dichloride 3 was actually formed in minute quantity and is soluble in acetic acid. The tetrazonium product of 1 can be isolated as tetrafluoroborate salt 4 in 3.4% yield by adding fluoboric acid into the acetic acid solution. The structure 4 was confirmed by IR and cross-polarization magic angle spinning13C NMR spectroscopy. Further investigations showed that 1 can be quantitatively tetrazotized by nitrosylsulfuric acid in 78% sulfuric acid. The tetrazonium product was isolated as 4 in 74% yield. Key words: 1,4-diaminoanthraquinone, diazotization, tetrazotization, azo pigm...