JOURNAL OF MOLECULAR STRUCTURE
·
2018
·
IF 2.011
Feng Su,Ziqing Sun,Weike Su,Xianrui Liang
The tautomerism of three benzimidazole compounds: Omeprazole sulfide, 1 , (R)-Lansoprazole, 2 , and Omeprazole sulfone , 3 were investigated by NMR with the effect of variant solvents and temperature. The dielectric constant of the medium and the ability of solvents to form hydrogen bond with the tautomer had a profound effect on the tautomeric equilibration. The chemical shifts and resonance lines of compounds 1–3 differed greatly in different solvent system mainly due to intra- and intermolecular hydrogen bonds. Variable temperature-nuclear magnetic resonance (VT-NMR) experiments showed that at 203 K the two tautomers of compound 1 were separated and determined to be 6:4 and those of compound 3 be 7:3. In contrast, compound 2 presented only one tautomer at the same temperature while the tautomerism was observed again with temperature increasing. The free energy of activation of the tautomeric interchange of compounds 1 – 3 were 13.77 kcal/mol, 13.47 kcal/mol and 13.06 kcal/mol, respectively. Density function theory (DFT) calculations results showed the tautomers of compound 2 had higher energy differences among the three compounds demonstrating only one preferred conformation existed at 203 K. The preferred conformations of compounds 1 and 3 were also given.
研究领域:
化学
·
物理化学
·
光谱学
·
理论化学
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产品关联
DOI
高影响因子
CARBOHYDRATE POLYMERS
·
2025
·
IF 12.5
Shasha Tian,Zian Mao,Yuexia Wang,Kewei Li,Yafei Li,Bingqi Zhu,Fangmei Zhou,Jingchao Li,Yingzhi Shen,Zhishan Ding
Tetrastigma hemsleyanum Diels et Gilg ( T. hemsleyanum ) is a rare traditional Chinese medicine with high medicinal value and T. hemsleyanum polysaccharides (THPs) have attracted increasing attention in recent years. However, detailed structural and functional insights into THPs remain limited. Here, a novel pectic polysaccharide (STHP4) with an average molecular weight (Mw) of 119 kDa was extracted and purified from the aboveground part of T. hemsleyanum . Structurally, STHP4 was mainly composed of galacturonic acid, glucuronic acid, and galactose, with minor glucose, rhamnose, arabinose, and mannose, and its primary backbone was 1,4-GalA. Pectinase treatment of STHP4 yields two distinct fractions: STHP4-1 and STHP4-2. STHP4-1 shared the same types of monosaccharides with STHP4, except for the absence of glucose, but had a broad Mw distribution (9.9 to 251 kDa). Another product, STHP4-2, a mixture of oligosaccharides and free monosaccharides, has a Mw of 1.387 kDa. Their structures were further elucidated via methylation analysis and NMR spectra. Furthermore, STHP4-1 exhibited superior immune regulatory effects on macrophages, including increased nitric oxide release and elevated interleukin-6, interleukin-1β, and tumor necrosis factor α expression. These findings suggest that STHP4-1 might be the core active domain of STHP4, and both STHP4 and STHP4-1 are potential immune enhancers.
研究领域:
植物化学
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免疫学
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药理学
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产品关联
DOI
PubMed
高影响因子
NEW JOURNAL OF CHEMISTRY
·
2019
·Vol. 43
·期 18
·7028-7034
·
IF 3.069
Weitao Xu,Ming Liu,Mary Clare Escaño,Carl Redshaw,Bing Bian,Ying Fan,Zhu Tao,Xin Xiao
The interaction between cucuribit[10]uril (Q[10]) and a series of 4-pyrrolidinopyridinium salts bearing aliphatic substituents at the pyridinium nitrogen, namely 4-(C4H8N)C5H5NRBr, where R = Et (g1), n-butyl (g2), n-pentyl (g3), n-hexyl (g4), n-octyl (g5), n-dodecyl (g6), has been studied in aqueous solution by 1H NMR spectroscopy, electronic absorption spectroscopy and mass spectrometry. The results revealed that the guests g1–g5 are located completely inside the cavity differing only in the orientation of g1, g4 and g5 which are aligned with the portal, whilst g2 and g3 are perpendicular to it. For g6, the tetrahydropyrrole moiety remains outside of the portal. DFT calculations confirm the stability of the guests in the Q[10] and the possibility of their curved structure inside the Q[10].
研究领域:
化学
·
分子生物学
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产品关联
DOI
高影响因子
Polymer Chemistry
·
2022
·Vol. 13
·期 27
·4054-4063
·
IF 5.364
Tianxiao Chang,Hongyi Qi,Chenxi Liang,Yanbin Huang,Wantai Yang
Benzothiophene is an under-explored monomer for free radical polymerization. Here we report the preparation of poly(benzothiophene-alt-maleic anhydride) (PBTMA) microspheres with high yield by self-stabilized precipitation polymerization. The chemical structure of the PBTMA copolymer was characterized by 1H-NMR, 13C-NMR, FT-IR and MALDI-TOF MS analyses. The effects of various reaction parameters, including the reaction medium, the monomer concentration, the initiator concentration and the reaction time, on the morphology, particle size and molecular weight (Mn) of the resultant PBTMA microspheres were investigated systematically. The experimental results demonstrated that the PBTMA copolymer was an alternating copolymer, whose composition was independent of the monomer composition. Uniform PBTMA microspheres with the diameter in the range of 400 nm to 3000 nm and Mn up to 12 000 g mol−1 were easily prepared. PBTMA had good solubility in common polar organic solvents and possessed much higher thermal stability than other maleic anhydride copolymers. PBTMA also showed interesting fluorescence properties both in the solid state and in solution. This research has laid the foundation for the further development of PBTMA copolymers as a new material.
研究领域:
高分子科学
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材料科学
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化学工程
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产品关联
DOI
高影响因子
JOURNAL OF PHARMACEUTICAL AND BIOMEDICAL ANALYSIS
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2023
·
IF 3.4
Yuzhu Chai,Erlong Zhang,Zhuoer Cai,Dan Xu,Chunxia Zhu,Baiwang Sun
Letermovir is a cytomegalovirus inhibitor for cytomegalovirus infection a hematopoietic-cell transplantation. In the degradation test of Letermovir, five new impurities were detected at levels of ND ∼ 2.21 % (by oxide, thermal or photolytic). These impurities were synthesized directly, characterized and identified by HRMS NMR spectra and X-ray crystallography. Then co-injected with commercial products to confirm their retention times in HPLC . The possible formation pathways and synthetic methods of these impurities were discussed in details. Furthermore, the toxicological properties of impurities were evaluated by ACD/Percepta 14.52.0 (Build 3525) software.
研究领域:
药学
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分析化学
·
毒理学
✓ 已验证
DOI
PubMed
高影响因子
JOURNAL OF CHEMICAL AND ENGINEERING DATA
·
2014
·
IF 2.045
Jia-rong Guo,Ling-Hua Zhuang,Guo-Wei Wang,Yan Wang,Jie Sun
The chemical structure of a new gemini dicationic imidazolium ionic liquid, 1,1′-[1,2-ethanediylbis(oxy-1,2-ethanediyl)]bis-[3-methyl-1H-imidazolium-1-yl] dihexafluorophosphate ([C6O2(mim)2][PF6]2), was established by 1HNMR. The thermal stability of [C6O2(mim)2][PF6]2 was studied with differential scanning calorimetry and thermogravimetric analyses. With the use of the analytical stirred-flask method at atmospheric pressure, the solubilities of [C6O2(mim)2][PF6]2 in water, methanol, ethanol, dimethylformamide, dimethyl sulfoxide, and (acetone + water) binary solvent mixtures were measured from (283.00 to 323.00) K. The experimental data was correlated with the modified Apelblat equation.
研究领域:
化学
·
材料科学
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DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2019
·Vol. 136
·期 47
·48208
·
IF 2.188
Chengbing Yu,Yilin Lu,Fangfang Wu
Polyester fabrics are usually difficult in dyeing deeply due to their dense structure and high surface refractive index, and deepening finishing is an effective method to obtain dark polyester fabrics. In this article, octamethyl cyclotetrasiloxane (D 4 ), 1,3,5-tris(3,3,3-trifluoropropyl)-methylcyclotrisiloxane (D 3 F), and silane coupling agent KH-902 were used as main monomers to synthesize organic fluorosilicone, and further to prepare cationic organofluorosilicone (COFS) and COFS darkening agent. FTIR and 1 H-NMR were used to characterize the structure of synthetic products. The finishing experiments confirmed that COFS darkening agent had good shade darkening on dyed polyester fabrics with small color change. The optimum conditions of deepening finishing were COFS darkening agent concentration of 20%, the pick-up of 85%, and the curing temperature of 180 °C. After finishing, the dyed fabric had no lowering effect on color fastness, all at grade 4 or above. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 48208.
研究领域:
材料科学
·
纺织工程
·
有机化学
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DOI
高影响因子
JOURNAL OF MOLECULAR LIQUIDS
·
2024
·
IF 5.3
Xin Hu,Yang Guo,Feng Xia,Shangwu Ding,Zhong Chen,Xiaohong Cui
Micellar solubilization is considered as a key factor affecting the recovery efficiency in chemically enhanced oil recovery (cEOR). However, it is poorly understood how polymers in surfactant-polymer (SP) flooding influences the micellar solubilization. Guar gum (GG) and hydroxyethyl cellulose (HEC) are two important and widely used polysaccharide polymers. In this work, the effect of GG and HEC on the solubilization of a crude oil model compound methyl benzoate (MB) in anionic sodium dodecyl sulfate (SDS) micelles and the underlying mechanism were explored at the molecular scale by NMR spectroscopy. GG and HEC slightly increased the MB solubility in SDS micelles but did not change the solubilization capacity. No correlation peak was observed to demonstrate the attractive interaction between polymer and SDS. After examination, there is weak electrostatic repulsion between HEC/GG and SDS, which made the polymer independent from SDS micelles and was unable to participate in the formation of micelles to alter micellar structure and solubilization behavior. Although the solubility of MB was slightly increased, this increase should originate from weak molecular interactions between polymers, surfactants and hydrophobic molecules, including hydrogen bonding, van der Waals forces and hydrophobic interactions, etc. In summary, without strong electrostatic attraction between polymer and surfactant, the solubilization of polymers and the solubilization of micelles proceed independently, resulting in that the solubilization capacity of SDS micelles was not improved.
研究领域:
化学工程
·
石油工程
·
分子生物学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Analysis and Testing
·
2024
·Vol. 8
·期 1
·1-8
·
IF 5.5
Tu Mengling,Zhang Wei,Zhu Yunxiao,Ma Wen,Li Xiao,Zhou Shukun,Li Hongmei,Li Xianjiang
Thiacloprid is the first-generation neonicotinoid insecticide, which is widely used in modern agriculture. Reference materials are essential for sound measurement and traceability of results in chemical analysis. Pure thiacloprid was comprehensively assessed by two orthonormal methods: mass balance (MB) and quantitative nuclear magnetic resonance spectroscopy (qNMR). From MB, its mass fraction value was 998.4 mg/g with the subtraction of structurally related impurities (99.87%), inorganic impurities (0.006 mg/g), water (0.33 mg/g), and volatile organic solvent (0 mg/g). To guarantee sufficient separation of structurally related purity, peak purity of thiacloprid was evaluated by five points of UV spectra. From the qNMR of hydrogen, its mass fraction value was 995.7 mg/g which was traced to the internal standard (methyl sulfone). Finally, the certified value was assigned to 997 mg/g, together with an expanded uncertainty of 3 mg/g ( k = 2). This high-purity thiacloprid can be applied to routine monitoring in agriculture and the food fields.
研究领域:
分析化学
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农业科学
·
食品科学
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产品关联
DOI
高影响因子
Carbohydrate Polymer Technologies and Applications
·
2025
·
IF 6.5
Yunning Yang,Chen Song,Xiaona Sun,Zhejin Chen,Tong Wu,Chunqing Ai,Fanhua Kong,Shuang Song
Although nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical tool, obtaining high-resolution NMR spectra of some high-molecular-weight and viscous polysaccharides remains challenging. Partial degradation could facilitate polysaccharides for NMR analysis, but potential composition alterations raise concerns, especially for sulfated polysaccharides. To explore the applicability of degradation approaches for sulfated polysaccharides, the present study compared outcomes of acid (HCl) and photoelectrocatalysis pretreatments for depolymerizing 2 representative sulfated polysaccharides, carrageenan and fucoidan. The results revealed that 1 M HCl at 100 °C could efficiently depolymerize carrageenan to 20 kDa within 30 min and fucoidan to 30 kDa within 10 min, but destruct more than half of sulfated polysaccharides. In contrast, photoelectrocatalysis could generate low-molecular-weight products while preserving structure blocks. Notably, both depolymerization pretreatments could facilitate sulfated polysaccharides for NMR analysis and enhance the spectral resolution. However, HCl tended to produce mono- and oligo-saccharides thereby affecting NMR spectra, while 50-min and 60-min photoelectrocatalysis treatments were suitable for carrageenan and fucoidan, respectively, to improve their NMR spectra without signal alterations. Therefore, the present study demonstrated photoelectrocatalysis depolymerization as a potential pretreatment for sulfated polysaccharides to facilitate their NMR analysis.
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产品关联
DOI
高影响因子
FUEL
·
2026
·
IF 7.5
Guo Wenying,Huang Guilan,Yuan Ling,Zhang Wenxin,Xia Mingzhu
Recently, higher alkanols have attracted the attention of researchers because, compared with other widely studied lower alkanols (such as ethanol and methanol), they have higher energy density, higher cetane number, better mixing stability and lower hygroscopicity. In biodiesel, alkanols are often added to improve the combustion performance of diesel engines. The qualitative of alkanol components is particularly important for the quality control of biodiesel. A reliable analysis method is demanded to distinguish the various alkanols in biodiesel. This study employed diffusion-ordered nuclear magnetic resonance spectroscopy (DOSY NMR) to establish a quantitative relationship model between diffusion coefficients and molecular weights of n-alkanols in DMSO‑ d 6 . It is found that the deviation from theoretical molecular weight (ΔMW) of the external calibration curves (ECCs) using dimethyl sulfoxide (DMSO) (0.46–1.88) as internal standards can significantly reduce the MW error than the internal calibration curves (ICCs) (1.05–2.65). The calibration curve of ECCs shows excellent fitting degree (R 2 = 0.999) and effectively mitigates the impact of external variables: ΔMW remains within ±7 when the concentration ranges from 0.05 to 100 mg/mL or the temperature varies from 288 K to 308 K. Based on the molecular weight determined by this method, n-alkanols that differ by only one carbon atom could be distinguished accurately, and the method has been validated in actual biodiesel samples containing C 4 -C 8 n-alkanols.
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DOI
高影响因子
Chemistry-An Asian Journal
·
2021
·Vol. 16
·期 22
·3658-3663
·
IF 4.568
Xueke Gao,Minjun Ma,Christian Marcus Pedersen,Rui Liu,Zhenzhou Zhang,Honghong Chang,Yan Qiao,Yingxiong Wang
Despite being used as an anti-leukemic drug, the poor solubility of 6-mercaptopurine (6-MP) limits its use in topical and parenteral applications. Dendrimers are commonly used as drug carriers to improve their solubility in aqueous solution. In this work, the interactions between 6-MP and the amine-terminated poly(amidoamine) dendrimers (PAMAM−NH 2 ) were investigated by various NMR technology. The chemical shift titrations disclosed that the 6-MP interacted with the surface of PAMAM−NH 2 mainly through electrostatics. The determination of diffusion coefficient and relaxation measurements further confirmed the presence of interactions in 6-MP/PAMAM−NH 2 complexes. In addition, the encapsulation of 6-MP within the cavity of PAMAM−NH 2 was revealed through nuclear Overhauser effect spectroscopy and Saturation Transfer Double Difference analysis. Finally, the binding strength (H-8 is 100% and H-2 is 70%) of 6-MP to PAMAM−NH 2 was quantitatively expressed using epitope maps. This study provides a systematic methodology for qualitative and quantitative studies of the interactions between dendrimers and drug molecules in general.
研究领域:
药物化学
·
纳米技术
·
药物递送系统
·
核磁共振光谱
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）