Dichloromethyl alkyl ethers have been synthesized from alkyl formates (C1–C4) and oxalyl chloride in the presence of catalytic amount of N-methylformanilide. N,N-Dimethylformamide is not suitable for the reaction. The method has the advantages of simple experimental procedure, which is applicable to large scale synthesis, without use of harmful reagents. 相似文献
Dietary fiber can be obtained by dextrinization, which occurs while heating starch in the presence of acids. During dextrinization, depolymerization, transglycosylation, and repolymerization occur, leading to structural changes responsible for increasing resistance to starch enzymatic digestion. The conventional dextrinization time can be decreased by using microwave-assisted heating. The main objective of this study was to obtain dietary fiber from acidified potato starch using continuous and discontinuous microwave-assisted heating and to investigate the structure and physicochemical properties of the resulting dextrins. Dextrins were characterized by water solubility, dextrose equivalent, and color parameters (L* a* b*). Total dietary fiber content was measured according to the AOAC 2009.01 method. Structural and morphological changes were determined by means of SEM, XRD, DSC, and GC-MS analyses. Microwave-assisted dextrinization of potato starch led to light yellow to brownish products with increased solubility in water and diminished crystallinity and gelatinization enthalpy. Dextrinization products contained glycosidic linkages and branched residues not present in native starch, indicative of its conversion into dietary fiber. Thus, microwave-assisted heating can induce structural changes in potato starch, originating products with a high level of dietary fiber content. 相似文献
Starch isolated from an under-utilized legume plant (pigeon pea) was carboxymethylated. Influences of reaction parameters were investigated on the degree of substitution (DS) and the reaction efficiency (RE). Studies showed that optimal DS of 1.12 could be reached at reaction efficiency of 80.6% in isopropanol-water reaction medium (40 °C, 3 h). Scanning electron microscopy showed that after carboxymethylation, the granular appearance of the native starch was distorted. Wide-angle X-ray diffractometry revealed that crystallinity was reduced significantly after carboxymethylation. The infrared spectra revealed new bands in the carboxymethyl starch at ν = 1600, 1426 and 1324 cm−1 which were attributed to carbonyl functional groups vibration, -CH2 scissoring and OH bending vibration, respectively. Broad-band 13C NMR of carboxymethyl starch showed an intense peak at δ = 180.3 ppm which was assigned to carbonyl carbon on the carboxymethyl substituent on the AGU (Anhydroglucose Unit). DEPT (Distortionless Enhancement by Polarization Transfer) 135 NMR showed negative signals which correspond to methylene carbons on the AGU. Differential Scanning Calorimetry (DSC) suggests loss of crystallinity after carboxymethylation. Thermogravimetry (TG), Derivative Thermogravimetry (DTG) and Differential Thermal Analysis (DTA) show that thermal stability improved after carboxymethylation. The study provides information on the preparation and characterization of a biomaterial from a new source which could be used alone or in the preparation of other functional polymers for diverse polymer applications. 相似文献
Starch has been tested as single-fuel and in a two-fuel mixture, together with N-methylurea, in a new combustion-based synthesis of zinc aluminate oxides, using different fuel compositions and equivalence ratios Φe (Φe = fuel/oxidant). The combustion process has been analyzed by simultaneous thermal analysis. The corresponding oxides were characterized by X-ray diffraction analysis, UV-Vis spectroscopy, scanning electron microscopy and BET investigations. Crystal structures were refined by Rietveld method. The morphology, specific surface area and optical properties of the obtained zinc aluminate have proved to be strongly dependent on the fuel nature and composition. The lowest crystallite size (131 Å) is achieved for the oxide generated from the starch-based precursor, while the highest surface area (20.69 m2/g) has been obtained for a 3:1 N-methylurea/starch fuel composition. The non-zero value for microstrain has indicated spinelic defects in the starch-fuel corresponding oxide. UV-Vis spectroscopic analysis have confirmed the intrinsic properties of the resulted mixed metal oxide, but also shows the presence of a certain disorder degree for all the other samples. The superior values of the band gap (4.2-4.7 eV) for the obtained oxides relative to the bulk case (3.8 eV) are the result of the nanometric dimensions of the particles. 相似文献
Transitory starch plays a central role in the life cycle of plants. Many aspects of this important metabolism remain unknown; however, starch granules provide insight into this persistent metabolic process. Therefore, monitoring alterations in starch granules with high temporal resolution provides one significant avenue to improve understanding. Here, a previously established method that combines LCSM and safranin-O staining for in vivo imaging of transitory starch granules in leaves of Arabidopsis thaliana was employed to demonstrate, for the first time, the alterations in starch granule size and morphology that occur both throughout the day and during leaf aging. Several starch-related mutants were included, which revealed differences among the generated granules. In ptst2 and sex1-8, the starch granules in old leaves were much larger than those in young leaves; however, the typical flattened discoid morphology was maintained. In ss4 and dpe2/phs1/ss4, the morphology of starch granules in young leaves was altered, with a more rounded shape observed. With leaf development, the starch granules became spherical exclusively in dpe2/phs1/ss4. Thus, the presented data provide new insights to contribute to the understanding of starch granule morphogenesis. 相似文献
Copolymerization of acrylic acid (AAc) and gelatinized maize starch in aqueous medium using γ‐irradiation, followed by neutralization with alkali solution was carried out. The preparation conditions, such as irradiation dose and starch/AAc compositions were investigated. The higher the irradiation dose, as well as the AAc content in the feed solution, the higher the gel content. The copolymers were characterized by FTIR spectroscopy, thermo‐gravimetric analysis (TGA) and scanning electron microscopy (SEM). SEM revealed that the higher the dose, the lower the copolymer pore size. Starch/AAc copolymers have thermal stability higher than that for starch and poly acrylic acid individually. The swelling of starch/AAc hydrogels reduced as the gel content increases. The maximum water absorption obtained for starch/AAc hydrogels in distilled water was 200 g/g, and for neutralized starch/AAc hydrogels was 350 g/g. The swelling ratio of starch/AAc hydrogels of different compositions in NaCl solution is lower than that obtained in distilled water. The results suggest that the neutralized starch/AAc hydrogels have a high swelling property, and can be used in a variety of commercial applications. 相似文献
The reaction of N-acylamino-2-bromoacetes 2 (via N-acylimino acetates 3) with higher order mixed cuprates, trimethysilyl enol ether and β-dicarbonyl compounds leads to a variety of α-amino acid derivatives. Their conversion into the free amino acids can be conveniently carried out by the use of t-butyl protection. In case of the N-acetyl compounds cleavage of the protecting group and optical resolution can be achieved in one step by hog renal acylase. 相似文献
Starch is the primary form of reserve carbohydrate storage in plants. Rice (Oryza sativa L.) is a monocot whose reserve starch is organized into compounded structures within the amyloplast, rather than a simple starch grain (SG). The mechanism governing the assembly of the compound SG from polyhedral granules in apposition, however, remains unknown. To further characterize the proteome associated with these compounded structures, three distinct methods of starch granule preparation (dispersion, microsieve, and flotation) were performed. Phase separation of peptides (aqueous trypsin-shaving and isopropanol solubilization of residual peptides) isolated starch granule-associated proteins (SGAPs) from the distal proteome of the amyloplast and the proximal ‘amylome’ (the amyloplastic proteome), respectively. The term ‘distal proteome’ refers to SGAPs loosely tethered to the amyloplast, ones that can be rapidly proteolyzed, while proximal SGAPs are those found closer to the remnant amyloplast membrane fragments, perhaps embedded therein—ones that need isopropanol solvent to be removed from the mature organelle surface. These two rice starch-associated peptide samples were analyzed using nano-liquid chromatography–tandem mass spectrometry (Nano-HPLC-MS/MS). Known and novel proteins, as well as septum-like structure (SLS) proteins, in the mature rice SG were found. Data mining and gene ontology software were used to categorize these putative plastoskeletal components as a variety of structural elements, including actins, tubulins, tubulin-like proteins, and cementitious elements such as reticulata related-like (RER) proteins, tegument proteins, and lectins. Delineating the plastoskeletal proteome begins by understanding how each starch granule isolation procedure affects observed cytoplasmic and plastid proteins. The three methods described herein show how the technique used to isolate SGs differentially impacts the subsequent proteomic analysis and results obtained. It can thus be concluded that future investigations must make judicious decisions regarding the methodology used in extracting proteomic information from the compound starch granules being assessed, since different methods are shown to yield contrasting results herein. Data are available via ProteomeXchange with identifier PXD032314. 相似文献
The present study aimed to determine changes in the properties of starch triggered by its long-lasting (1, 2, 4, 7, 10, or 14 days) retention with citric acid (5 g/100 g) at a temperature of 40 °C. The starch citrates obtained under laboratory conditions had a low degree of substitution, as confirmed via NMR and HPSEC analyses. The prolonging time of starch retention with citric acid at 40 °C contributed to its increased esterification degree (0.05–0.11 g/100 g), swelling power (30–38 g/g), and solubility in water (19–35%) as well as to decreased viscosity of the starch pastes. Starch heating with citric acid under the applied laboratory conditions did not affect the course of DSC thermal characteristics of starch pasting. The low-substituted starch citrates exhibited approximately 15% resistance to amylolysis. 相似文献
We synthesized 5-hydroxymethylfurfural (HMF) from carbohydrates using metal chloride catalysts. A 33.2 % yield of HMF was obtained from raw Dioscorea composita biomass with high starch by using a catalyst system composed of CrCl3·6H2O and LaCl3·6H2O at 120 °C for 4 h in N,N-dimethylacetamide containing lithium chloride. The catalyst system is also cost-effective for the conversion of soluble starch into HMF. In addition, levulinic acid was not formed in the reactions. 相似文献
TiO2 materials with a hierarchical meso/macropore organization were fabricated by using titanium dioxide nanoparticles and starch gel templates. Starch sponges with high internal macroporosities were prepared by freezing and thawing of starch gels and were then infiltrated with colloidal suspensions of titania nanoparticles and air-dried to produce TiO2-starch foams with pores up to 200 m across depending on the starch concentration and the TiO2 loading. The TiO2 nanoparticles were deposited as coherent layers on the thin walls of the starch framework, which was removed by calcination without significant disruption of the TiO2 framework. The three dimensional macroporous structures of TiO2-starch sponge composite and TiO2 sponge induced extremely high photocatalytic activity. 相似文献
The Cu/γ-Al2O3 catalysts with different Cu loadings were prepared by impregnation method. The physicochemical properties of these Cu/γ-Al2O3 catalysts were characterized by H2-TPR, XRD, and in-situ XPS. The catalytic hydrogenation performances of methyl laurate over Cu/γ-Al2O3 catalysts were studied. The results show that the hydrogenation performances of methyl laurate on Cu/γ-Al2O3 catalyst are related to the dispersion, crystallite size, and content of the active component Cu0. The 10CA catalyst has the best hydrogenation performances for methyl laurate to produce C12 alcohol. At 300 °C, the conversion of methyl laurate and the selectivity of C12 alcohol are 55.6% and 30.4%, respectively. 相似文献
Alpha- and beta-linked 1,3-glucans have been subjected to conversion with p-toluenesulfonic acid (tosyl) chloride and triethylamine under homogeneous reaction conditions in N,N-dimethyl acetamide/LiCl. Samples with a degree of substitution of tosyl groups (DSTs) of up to 1.91 were prepared by applying 5 mol reagent per mole repeating unit. Hence, the reactivity of α-1,3-glucan is comparable with cellulose and starch, while the β-1,3-linked glucan curdlan is less reactive. The samples dissolve in aprotic dipolar media independent of the DSTs and possess a solubility in less polar solvents that depends on the DSTs. NMR studies on the tosyl glucans and of the peracylated derivatives showed a preferred tosylation of position 2 of the repeating unit. However, the selectivity is less pronounced compared with starch. It could be concluded that the α-configurated glycosidic bond directs tosyl groups towards position 2. 相似文献
The rate of carboxylic ester cleavage by amphiphilic low-molecular-weight and polymeric amines in the presence of polyoxyethylated calix[4]arenes with different degrees of oxyethylation is determined by the formation of mixed aggregates, by the shift of pKa of the amine, and the character of the distribution of the reactants in functional micelles. All of the systems show a high substrate specificity. In the case of octyl- and decylamines, the reaction of p-nitrophenyl acetate is catalyzed and the reaction of more hydrophobic p-nitrophenyl laurate is inhibited. An opposite situation is observed in the systems based on branched polyethyleneimine: the reaction of p-nitrophenyl acetate is inhibited and the process involving p-nitrophenyl laurate is accelerated. 相似文献
Practical preparations of dichloromethyl alkyl ethers are described, based on the reaction of alkyl formates with oxalyl chloride in the presence of N-methylformanilide. The method involves a simple procedure that does not require the use of harmful reagents. Dichloromethyl propyl and dichloromethyl butyl ethers represent secure synthetic equivalents to dichloromethyl methyl ether. Formylations of both electron-deficient and electron-rich aromatics with these dichloromethyl alkyl ethers in the presence of AlCl3, FeCl3, or TiCl4 have been systematically investigated. A plausible mechanism of formylation is discussed. 相似文献
A large quantity of longan fruits (Dimocarpus longan Lour.) produced annually are processed into many products, one of which is black longan, from which the dried, dark-brown meat has been used medicinally in traditional medicine, while the starch-containing seeds are discarded. In this study, starch samples (BLGSs) were isolated from seeds of black longan fruits prepared using varied conditions. The in vitro digestibility was determined in comparison with those extracted from fresh (FLGS) and dried (DLGS) seeds. Scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy were employed to evaluate the starch properties. The results showed that the yields of FLGS, DLGS, and BLGSs were 20%, 23%, and 16–22% w/w, respectively. SEM images showed starch granules of mixed shapes, with sizes up to 15 µm in all samples. XRD patterns confirmed an A-type crystallinity for FLGS and DLGS, with strong refraction peaks at 2θ = 15°, 17°, 18°, and 23°, while BLGSs also showed detectable peaks at 2θ = 10° and 21°, which suggested V-type structures. Thermal properties corroborated the changes by showing increases in peak gelatinization temperature (Tp) and enthalpy energy (ΔH) in BLGSs. The paste viscosity of BLGSs (5% w/w) decreased by 20–58% from that of FLGS. The FTIR peak ratio at 1045/1022 and 1022/995 cm−1 also indicated an increase in ordered structure in BLGSs compared to FLGS. The significant increase in the amounts of slowly digestible starch (SDS) and resistant starch (RS) in BLGSs compared to FLGS, especially at a prolonged incubation time of 20 (4.2×) and 30 days (4.1×), was proposed to be due to the heat-induced formation of starch inclusion with other components inside the seed during the black longan production process. Thus, black longan seed could be a new source of starch, with increased RS content, for potential use in the food and related industries. 相似文献
Complete dissolution is needed for the separation, characterization, or homogeneous labeling of whole starch molecules. A method is presented to quantify the extent of starch dissolution in DMSO for the first time; it is validated on a commercial rice starch. It is used directly on starch dispersions containing possible undissolved or co‐dissolved species. High‐amylose maize starches, known to be digested slowly in vivo, only quantitatively dissolve in the presence of high concentrations of an H‐bond disrupter, LiBr, although they form clear dispersions at low LiBr concentrations. Starch quantitatively dissolves from waxy rice flours; non‐starch components partially co‐dissolve but do not interfere with the dissolution quantification.