液相色谱-串联质谱测定降血糖功能食品中双胍类药物

建立了降血糖功能食品中二甲双胍和苯乙双胍的液相色谱-串联质谱测定方法。采用体积比1:1的甲醇-乙醇溶液超声提取降血糖功能食品降糖粉、奶粉、口服液、胶囊、清渴茶中的二甲双胍和苯乙双胍,提取液经WCX固相萃取柱净化后,以乙腈和2 mmol/L NH4Ac溶液(含0.1%甲酸)为流动相进行梯度洗脱,经Agilent ZORBAX Eclipse XDB-C18色谱柱分离,电喷雾正离子(ESI+)模式电离,多反应监测(MRM)模式检测,基质回收标准曲线定量。二甲双胍和苯乙双胍的定量限(LOQ)均为10.0μg/kg,在不同基质中添加水平为10.0,20.0,50.0μg/kg时,二甲双胍和苯乙双胍的平均回收率分别为92.7%～99.6%和91.3%～100.3%,RSD分别为2.1%～8.4%和1.1%～11%。本方法可用于降血糖功能食品中双胍类药物的测定和确证。     

Magnesium boride sintered as high-energy fuel

Boron was chosen as fuel owing to its excellent thermodynamic values for combustion. The difficulty of the boron in combustion is the formation of a surface oxide layer, which postpones the combustion process, reducing the performance of the rocket engine. In this paper, magnesium boride was sintered as high-energy fuel as a substitute for boron. The combustion heat and efficiency of magnesium boride and boron were determined using oxygen bomb calorimeter. The combustion characteristics of magnesium boride were investigated by thermal analysis, chemical analysis, XRD, and EDS. Results show that the combustion performance of magnesium boride are better than that of amorphous boron in oxygenated environments. The evaporation of magnesium in magnesium boride combustion process prevent the formation of a closed oxide layer, leading to higher combustion efficiency.     

直接进样电喷雾离子阱质谱法对含硫三联吡啶衍生物的研究

采用电喷雾电离质谱通过直接进样方式对合成的3个含硫的三联吡啶配体及2个钌配合物进行分析,详细研究了其在电喷雾条件下的质谱行为。结果表明,含有芳硫基和苄硫基的三联吡啶配体在电喷雾过程中采取了不同的断裂方式,前者首先从与芳硫键相连的碳硫键断裂失去不含硫的部分碎片离子,而后者则从苄基碳硫键断裂失去含硫的部分碎片离子。两类配体与钌形成的配合物均具有较稳定的结构,不易发生多级质谱断裂。通过对配合物分子离子峰和同位素峰的分析讨论,确定了含硫的三联吡啶合钌配合物的结构。这一研究结果表明电喷雾多级串联质谱适合于含硫三联吡啶类配体及其钌配合物的结构研究,方法简便高效、准确可靠,为该类化合物的结构研究提供了参考。     

基于4-二苯基乙酸及1,3-二(4-吡啶基)丙烷的两个银配合物的结构和荧光

以同物质的量比例的4-二苯基乙酸(Hbpa)、1,3-二(4-吡啶基)丙烷(bpp)和[Ag(NH₃)](OH),在不同反应条件下制备了2个基于柔性配体的类三明治配合物[Ag₂(bpa)₂(bpp)₂]·2H₂O_n(1)和[Ag(bpa)(bpp)]·2H₂O_n(2),对其进行了单晶结构、元素分析、红外光谱、荧光光谱和粉末衍射表征。结构表明1是由T型配位的银离子和Ag…Ag超分子作用组装而成的二维配合物;配合物2则是由四面体构型银离子和π…π堆积作用组装的二维配位超分子。此外,1和2还可在可见光区的不同位置发射较强荧光。     

Dynamic Changes in Xylanases and β-1,4-Endoglucanases Secreted by Aspergillus niger An-76 in Response to Hydrolysates of Lignocellulose Polysaccharide

Aspergillus niger is an effective secretor of glycoside hydrolases that facilitate the saprophytic lifestyle of the fungus by degrading plant cell wall polysaccharides. In the present study, a series of dynamic zymography assays were applied to quantify the secreted glycoside hydrolases of A. niger cultured in media containing different carbon sources. Differences in the diversity and concentrations of polysaccharide hydrolysates dynamically regulated the secretion of glycoside hydrolases. The secretion of β-1,4-endoglucanase isozymes was observed to lag at least 24 h behind, rather than coincide with, the secretion of xylanase isozymes. Low concentrations of xylose could induce many endoxylanases (such as Xyn1/XynA, Xyn2, and Xyn3/XynB). High concentrations of xylose could sustain the induction of Xyn2 and Xyn3/XynB but repress Xyn1/XynA (GH10 endoxylanase), which has a broad substrate specificity, and also triggers the low-level secretion of Egl3/EglA, which also has a broad substrate specificity. Mixed polysaccharide hydrolysates sustained the induction of Egl1, whereas the other β-1,4-endoglucanases were sustainably induced by the specific polysaccharide hydrolysates released during the hydrolysis process (such as Egl2 and Egl4). These results indicate that the secretion of glycoside hydrolases may be specifically regulated by the production of polysaccharide hydrolysates released during the process of biomass degradation.     

A comparative study of thermal properties of sinocalamus affinis and moso bamboo

Moso bamboo (Phyllostachys pubescens) and sinocalamus affinis (Phyllostachys heterocycla) were used in the research. Thermogravimetry (TG), a combination of TG and Fourier transform infrared spectrometer (TG–FTIR), X-ray diffraction (XRD), and differential thermal analysis (DTA) were used to investigate thermal decomposition of bamboo. The calorific value and smoke release process of both bamboos were also tested, respectively. The results from TG indicated that degradation process of sinocalamus affinis and moso bamboo was similar, but their degradation temperatures were different. The main decomposition occurred in the second step and about 68.70 and 64.63% masses degraded for sinocalamus affinis and moso bamboo, whose temperature of maximum mass loss was 319 and 339 °C, respectively. DTA curve showed that the thermal decomposition of both bamboos was an absorbance heat process. TG–FTIR analysis showed that the main pyrolysis products of both bamboos were similar, including absorbed water (H₂O), methane gas (CH₄), carbon dioxide (CO₂), acids and aldehydes, ammonia gas (NH₃). The calorific value of moso bamboo (19,291 J g^?1 K^?1) was higher than that of sinocalamus affinis (18,082 J g^?1 K^?1). The initial time of smoke release process of moso bamboo was later, and its maximum smoke density was higher than that of sinocalamus affinis. The difference was probably attributed to different compositions and structure of sinocalamus affinis and moso bamboo. The results from this research are very helpful to better design manufacturing process of bio-energy, made from bamboo, by gasification and pyrolysis methods.     

A pH-Sensitive Zwitterionic Iron Complex Probe with High Biocompatibility for Tumor-Specific Magnetic Resonance Imaging

Accurate diagnosis of tumor characteristics, including its location and boundary, is of immense value to subsequent therapy. Activatable magnetic resonance imaging (MRI) contrast agents that respond to tumor-specific microenvironments, such as the redox state, pH, and enzyme activity, enable better mapping of tumor tissue. However, the practical application of most reported activatable agents is hampered by problems including potential toxicity, inefficient elimination, and slow activation. In this study, we developed a zwitterionic iron complex (Fe-ZDS) as a positive MRI contrast agent for tumor-specific imaging. Fe-ZDS could dissociate in weakly acidic solution rapidly, accompanied by clear longitudinal relaxivity (r₁) enhancement, which enabled the complex to act as a pH-sensitive contrast agent for tumor-specific MR imaging. In vivo experiments showed that Fe-ZDS rapidly enhanced the tumor-to-normal contrast ratio by >40 %, which assisted in distinguishing the tumor boundary. Furthermore, Fe-ZDS circulated freely in the bloodstream and was excreted relatively safely via kidneys owing to its zwitterionic nature. Therefore, Fe-ZDS is an ideal candidate for a tumor-specific MRI contrast agent and holds considerable potential for clinical translation.     

蒙脱土表面键合配位体固相萃取填料的制备及其对重金属离子的吸附性能

通过酸洗、硅烷偶联剂表面活化、键合苯甲酰异硫氰酸酯对蒙脱土进行改性,制得新型固相萃取(SPE)材料。 采用红外光谱、扫描电子显微镜、X射线光电子能谱表征了改性蒙脱土的结构和形貌。 考察了制备的SPE填料对水中As³⁺、Bi³⁺、Cu²⁺、Sb³⁺、Sn²⁺和Pb²⁺的吸附性能,确定了最佳固相萃取条件,对6种金属离子吸附容量分别为10.83、11.92、12.67、10.43、10.01及10.54 mg/g。 通过SPE与电感耦合等离子体质谱联用测定了样品中As³⁺、Bi³⁺、Cu²⁺、Sb³⁺、Sn²⁺和Pb²⁺ 6种重金属离子的含量,检出限分别为0.024、0.013、0.075、0.037、0.011和0.064 μg/L。     

Hydralazine derivative of aldehyde: A new type of [M − H]+ ion formed in electrospray ionization mass spectrometry

Hydralazine has been widely employed in the development of drugs, derivatization reagents, and ligands. In the present work, we reported a new type of dehydrogenated ion [M ? H]⁺ that was produced from the hydralazine derivative of hexanal in electrospray ionization mass spectrometry (ESI‐MS). The formation of [M ? H]⁺ ions in the ESI‐MS was found to be independent on the mobile phase composition of the liquid chromatography and ESI source parameters. A series of hydralazine derivatives of aldehyde were investigated to confirm this phenomenon. The results showed that hydralazine derivatives of aldehydes that contained an sp³ hybridization carbon with a hydrogen at the α‐position of aldehydes could form the unexpected [M ? H]⁺ ions, whereas hydralazine derivative of acetone could only generate [M + H]⁺ ion in the ESI‐MS. We proposed the possible formation mechanism of [M ? H]⁺ ion for the hydralazine derivatives of aldehydes: the [M ? H]⁺ ion was possibly formed by the loss a hydrogen molecule (H₂) from the protonated ion [M + H]⁺. The results obtained from density functional theory (DFT) calculations supported this proposed formation mechanism of [M ? H]⁺ ion.     

Metabolite identification of tanshinol borneol ester in rats by high‐performance liquid chromatography combined with electrospray ionization quadrupole time‐of‐flight mass spectrometry

Tanshinol borneol ester (DBZ) is a potential drug candidate composed of danshensu and borneol. It shows anti‐ischemic and anti‐atherosclerosis activity. However, little is known about its metabolism in vivo. This research aimed to elucidate the metabolic profile of DBZ through analyzing its metabolites using high‐performance liquid chromatography combined with electrospray ionization quadrupole time‐of‐flight mass spectrometry. Chromatographic separation was performed on an Agilent TC‐C₁₈ column (150 × 4.6 mm, 5.0 μm) with gradient elution using methanol and water containing 0.2% (v/v) formic acid as the mobile phase. Metabolite identification involved analyzing the retention behaviors, changes in molecular weights and MS/MS fragment patterns of DBZ and its metabolites. As a result, 20 potential metabolites were detected and tentatively identified in rat plasma, urine and feces after administration of DBZ. DBZ could be metabolized to O‐methylated DBZ, DBZ‐O‐glucuronide, O‐methylated DBZ‐O‐glucuronide, hydroxylated DBZ and danshensu. Danshensu, a hydrolysis product of DBZ, could further be transformed into 12 metabolites. The proposed method was confirmed to be a reliable and sensitive alternative for characterizing metabolic pathways of DBZ and providing valuable information on its druggability.