A Fragmentation Study on Four Unusual Secoiridoid Trimers,Swerilactones H–K,by Electrospray Tandem Mass Spectrometry

Swerilactones H–K(1–4)as four unprecedented secoiridoid trimers represent a new type of natural product,which has attracted much interest of natural chemists due to their novel skeletons and promising bioactivity.In order to well understand their MS fragmentation behaviors,they were investigated by electrospray ionization ion-trap time-of-flight multistage product ion mass spectrometry(ESI-IT-TOF-MSn)for the first time.The protonated molecules([M?H]?)of swerilactones J and K,and deprotonated molecules([M-H]-)of swerilactones H,J and K were readily observed in the conventional single-stage mass spectra(MS);however only the[M?Cl]-ion for swerilactone I was obtained in negative mode.Based on the MSn study,the fragmentation pathways of swerilactones H and I in negative mode,and swerilactones J and K in both positive and negative modes were proposed.The neutral losses of H_(2)O,CO,CO_(2)and C_(2)H_(4)O moieties are the particular elimination from the precursor ions due to the presence of hydroxyl,d-lactone and 1-O-ethyl moieties in their structures,of which the retro-Diels–Alder cleavage was the most particular dissociation.The fragment ions at m/z 341 and 291 in negative mode can be considered as the diagnostic ions for secoiridoid trimers.This investigation will provide valuable information for their fast characterization from complicated natural mixtures and extensive understanding their structural architectures.

Theoretical Study on the Optical Properties for 2,7- and 3,6-Linked Carbazole Trimers by Time-dependent Density Functional Theory

Electronic properties, such as HOMO and LUMO energies, band gaps, ionization potential （IP） and electron affinity （EA） of 2,7- and 3,6-1inked carbazole trimers, two conjugated oligomcrs with different linkages of carbazole, were studicd by the density functional theory with Becke-Lee-Young-Parr composite exchange correlation functional （B3LYP）. The absorption spectra of these compounds were also investigated by time-dependent density functional theory （TD-DFT） with 6-3 IG＊ basis set. The calculated results indicated that the HOMO and LUMO of the 2,7- and 3,6-1inked carbazole trimers are both slightly destabilized on going from methyl substitution to sec-butyl substitution. Both IP and EA exhibit their good hole-transporting but poor electronaccepting ability. The presence of alkyl groups on the nitrogen atoms does not affect the intra-chain electronic delocalization along the molecular frame. Thus no significant effect on the band gap and absorption spectra of compounds has been found.

Insight into Medicinal Chemistry Behind Traditional Chinese Medicines: p-Hydroxybenzyl Alcohol-Derived Dimers and Trimers from Gastrodia elata

From an aqueous extract of“tian ma”(the steamed and dried rhizomes of Gastrodia elata),ten new compounds gastrodiben-zins A−D(1−4)and gastrotribenzins A−F(5−10),along with known analogues(11−20),having structure features coupling between two and three p-hydroxybenzyl-derived units via carbon-and/or ether-bonds,were isolated and characterized by spectroscopic data analysis.Meanwhile,the new compounds 5a,6a,8a,22,and 23,as well as the known derivatives 13a,14a,15,17−21,24,25,and p-hydroxybenzyl aldehyde were isolated and identified from a refluxed aqueous solution of p-hydroxybenzyl alcohol.Methylation of 5a and 6a in methanol and ethylation of 6a,8a,13a,and 14a in ethanol produced 5 and 6 and 7,8,13,and 14,respectively.using ultra-performance liquid chromatography high-resolution electrospray ioniza-tion mass spectrometry(UPLC-HRESIMS)analysis of the refluxed solutions of p-hydroxybenzyl alcohol and the refluxed extracts of the fresh G.elata rhizome and“tian ma”extracts indicated consistent production and variation of the dimeric and trimeric derivatives of p-hydroxybenzyl alcohol upon extracting solvents and refluxing time.In various assays,the dimeric and trimeric derivatives showed more potent activities than p-hydroxybenzyl alcohol itself and gastrodin,which are the main known active constituents of“tian ma”.These results revealed for the first time that the more effective dimers and trimers can be produced through condensation of the co-occurring p-hydroxybenzyl alcohol during processing and decocting of the G.elata rhizomes,demonstrating insights into medicinal chemistry behind application protocols of traditional Chinese medicines.

Artemsieverolactones A—H,Eight Guaiane-Type Sesquiterpenoid Trimers from Artemisia sieversiana

Eight new guaiane-type sesquiterpenoid trimers,artemsieverolactones A—H,possessing unprecedented scaffolds via biocatalyzed[4+2]Diels−Alder cycloaddition reactions were identified from Artemisia sieversiana.Their structures were determined by comprehensive spectroscopic data,single-crystal X-ray diffraction analyses,and ECD calculations.In terms of structure,artemsieverolactones A—H are first examples of sesquiterpenoid trimers from guaiane-type sesquiterpenoid through four different[4+2]Diels−Alder cycloaddition models.Antihepatic fibrosis assay suggested that five compounds exhibited activity against HSC-LX2 with IC_(50)values ranging from 37.8 to 117.1μmol/L.The most active artemsieverolactone B(2)displayed significant inhibitory activity against HSC-LX2 with IC_(50)value of 37.8μmol/L,which was 3 times more active than the positive drug silybin(IC_(50),139.7μmol/L).Preliminary mechanism study revealed that artemsieverolactone B could inhibit the deposition of human collagen typeⅠ(ColⅠ),human hyaluronic acid(HA),and human laminin(HL)with IC_(50)values of 40.4μmol/L(Col I),55.1μmol/L(HL),47.3μmol/L(HA),which was 2 to 3-fold more potent than silybin.

Novel phenanthrene/bibenzyl trimers from the tubers of Bletilla striata attenuate neuroinflammation via inhibition of NF-κB signaling pathway

Five novel(9,10-dihydro)phenanthrene and bibenzyl trimers,as well as two previously identified biphenanthrenes and bibenzyls,were isolated from the tubers of Bletilla striata.Their structures were elucidated through comprehensive analyses of NMR and HRESIMS spectroscopic data.The absolute configurations of these compounds were determined by calculating rotational energy barriers and comparison of experimental and calculated ECD curves.Compounds 5b and 6 exhibited inhibitory effects on LPS-induced NO production in BV-2 cells,with IC_(50) values of 12.59±0.40 and 15.59±0.83μmol·L^(-1),respectively.A mechanistic study suggested that these compounds may attenuate neuroinflammation by reducing the activation of the AKT/IκB/NF-κB signaling pathway.Additionally,compounds 3a,6,and 7 demonstrated significant PTP1B inhibitory activities,with IC_(50) values of 1.52±0.34,1.39±0.11,and 1.78±0.01μmol·L^(-1),respectively.Further investigation revealed that compound 3a might inhibit LPS-induced PTP1B overexpression and NF-κB activation,thereby mitigating the neuroinflammatory response in BV-2 cells.

Asponchimides A−E: new enantiomeric N-acetyldopamine trimers from Aspongopus chinensis

Five new racemic N-acetyldopamine (NADA) trimers, asponchimides A−E ( 1 − 5 ), were isolated from Aspongopus chinensis, a prominent traditional Chinese medicinal insect employed for alleviating pain, treating indigestion, and addressing kidney ailments. Compounds 1 − 5 were successfully resolved by chiral high-performance liquid chromatography (HPLC), yielding five pairs of enantiomers: (+)- and (−)-asponchimides A−E ( 1a / 1b − 5a / 5b ). Their structural identities were discerned by extensive spectroscopic analyses, including high-resolution mass spectrometry (HRMS), ultraviolet-visible (UV-Vis) spectroscopy, infrared (IR) spectroscopy, and nuclear magnetic resonance (NMR), and their absolute configurations were determined by electronic circular dichroism (ECD) calculations. Compounds 1 − 5 are pioneering instances of NADA trimers featuring a Δ7 double bond. When subjected to a series of bioassays, a majority of the compounds exhibited weak inhibitory activity against nitric oxide (NO) production in LPS-induced RAW 264.7 cells.

Environment-assisted excitation energy transfer in LH1-RC-type and LH2-type trimers

In this work,we study environment-assisted excitation energy transfer(EET) through calculating energy transfer efficiency(ETE) in LH1-RC-type and LH2-type trimers,which can be used to mimic energy transfer behaviors in the basic unit cells of LH1-RC and LH2 light-harvesting complexes.Quantum state evolution of the trimers is described by a non-Hermitian quantum master equation.ETE in these trimer systems is investigated by the use of numerical solutions at finite temperatures for the non-Hermitian master equation.We theoretically reveal the temperature-assisted ETE enhancement.It is found that highly efficient EET with nearly unit efficiency may occur in the nearby regime of the critical point of quantum phase transition.

Synthesis of disk-rod-disk liquid crystal trimers by using click chemistry

A series of disk-rod-disk liquid crystal trimers were synthesized.CuI-NEt3 catalyzed alkyne azide cycloaddition in toluene at room temperature connected two triphenylene discogens to a biphenyl rod-shaped mesogen.The trimers were characterized by using 1H NMR,IR,and high resolution mass spectrometry.The mesomorphic properties were investigated using polarized optical microscopy(POM) ,differential scanning calorimetry(DSC) ,and wide-angle X-ray diffraction.The results showed that the trimers exhibited rectangular columnar mesophase(Colr) .The length of the flexible spacer connecting the three segments has prominent influence on the phase transition temperatures of the trimers.

Nitrogen-bridged Ni(Ⅱ)porphyrinoid trimers with a central quinodiimine unit

Buchwald-Hartwig amination of 5,15-dibromo and 5,10-dibromo Ni(Ⅱ)porphyrins with 5-amino Ni(Ⅱ)porphyrin gave linear and bent trimers 4Ni and 5Ni with a central quinodiimine-type Ni(Ⅱ)porphyrinoid.The structures of 4Ni and 5Ni have been confirmed by X-ray diffraction analysis in both cases.The formation of unusual products 4Ni and 5Ni has been ascribed to facile oxidation of 5,15-and 5,10-amino Ni(Ⅱ)porphyrin unit.Reduction of 4Ni and 5Ni under proper conditions gave NH-bridged Ni(Ⅱ)porphyrin trimers 4Ni-2H and 5Ni-2H in high yields.Trimers 4Ni and 5Ni exhibit the lowest energy band as compared with 4Ni-2H and 5Ni-2H.Especially the bent trimer 5Ni exhibits a broad absorption tail beyond 1400 nm.

Ce^(3+)掺杂对NaYF_(4)∶Yb^(3+),Tm^(3+)纳米粒子上转换发光性能的影响及其荧光温度特性应用

采用溶剂热法制备了一系列不同Ce^(3+)含量的Yb^(3+)/Tm^(3+)/Ce^(3+)共掺NaYF_(4)纳米粒子。样品在980 nm激光激发下,可以观察到强烈的上转换蓝色荧光。探究了不同Ce^(3+)含量对发光强度的影响,发现在Ce^(3+)含量从0%增加到0.5%的过程中,紫外到可见的上转换发光随着Ce^(3+)浓度的增加先增强后减弱,在0.2%时荧光达到最强,比不掺Ce^(3+)时荧光增强高达5倍左右,其中475 nm的蓝光更是增强了6倍。此外,对其机理进行了深入细致的探究,一方面,掺杂Ce^(3+)后,Tm^(3+)中的(^(3)F_(3),^(3)H_(4))与Ce^(3+)中的(^(2)F_(7/2),^(2)F_(5/2))发生交叉弛豫,有效地防止了电子跃迁回到基态,以致整体荧光明显增强;另一方面,当掺入Ce^(3+)后,形成的(Yb^(3+)-Yb^(3+)-Ce^(3+))Trimers把能量传递给^(1)G_(4)能级,发出475 nm的蓝光,导致蓝光很强。将其应用于荧光强度比测温,绝对灵敏度高达0.0350 K^(-1)。

钢-铝固液相复合中浸镀助焊剂的应用研究

采用浸镀助焊剂的方法研究了助焊剂对钢─铝固液相复合质量的影响．结果表明，浸镀助焊剂方法可以解决钢─铝固液相复合过程中接触界面氧化问题，以卤化物为主的助焊剂1号可大幅度提高钢─铝固液相复合界面的结合强度.

Antioxidant Nature Adds Further Therapeutic Value: An Updated Review on Natural Xanthones and Their Glycosides

Plants have so much to offer as far as the discovery of new bioactive molecules is concerned.Among the several classes of phytochemicals,xanthones offer greater structural diversity and pharmacological value.They are variable but definitely antioxidant in nature.Thus they are attractive targets for natural product and medicinal chemists.Xanthones and their glycosides possess broad spectrum interesting biological activities,such as cytotoxic,anti-inflammatory,antioxidant,anti-bacterial,neuroprotective,anti-HIV,enzyme inhibition,and hypoglycemic.The radical scavenging ability of these molecules accounts for most of their added therapeutic values.This paper intended to serve as a guide for future endeavors in quest for these molecules.Structure-Activity Relationship(SAR)and mechanism of action is given for better understanding of their role as pharmacological agents.The most recent advances in the isolation of bioactive xanthones and their glycosides were presented here.This paper will assist in directed approaches towards the discovery of analogues of xanthones.

名校长工作室TRIMER研修模式助力乡村区域教育质量提升——以保定市贫困县(脱贫县)系列名校长工作室为例

如何以名校长工作室方式助推乡村教育质量提升,河北省保定市贫困县(脱贫县)系列名校长工作室项目组形成的TRIMER(三聚体)研修模式进行了很好的探索。TRIMER模式在研修功能定位上强调校长成长、学校提质与区域教育优化三位一体;在研修方式上,培训、改进、辐射等三线交织;在研修原则上,培训与改进、个人研修与团队研修、素养提升与辐射带动有机结合;在培养主体上,保定市本土优秀校长的示范、北京市双导师的引领与京保教育行政的保驾护航相得益彰;在运行力量上,行政力量、学术力量、校长自我发展力量密切配合。

大开眼界

世界因人类变得丰富多彩，电脑也因人数变得千奇百怪。因此，我们特别开辟“大开眼界”栏目，除了展示一些“养眼”的产品以外，还想启发大家的思维，将那些束缚我们思想的定式远远抛开。

Ultrafast Energy Transfer in Artificial Antenna Molecule Measured by Transient Fluorescence Spectroscopy

We have reported previously the ultrafast energy transfer process with a time constant of 0.8 ps from a monomeric to a dimeric subunit within a perylenetetracarboxylic diimide trimer, which was derived indirectly from a model fitting into the transient absorption experimental data. Here we present a direct ultrafast fluorescence quenching measurement by employing fs time-resolved transient fluorescence spectroscopy based on noncollinear optical parametric amplification technique. The rapid decay of the monomer＇s emission due to energy transfer was observed directly with a time constant of about 0.82 ps, in good agreement with the previous result.

One New A-type Proanthocyanidin Trimer from Lindera aggregata(Sims) Kosterm.

One new A - type proanthocyanidin trimer, lindetannin trimer, was isolated from the stems of Lindera aggregata (Sims) Kosterm.. Its structure was elucidated by spectral and chemical methods.

Synthesis, Crystal Structure and Gas Adsorption of a Trimeric Nickel-based Coordination Polymer

A trimeric porous coordination framework [Ni_3(TPTC)(IN)_2(μ_2-H_2O)_2(CH_3OH)_2)]n· x(solvents)(1, TPTC = terphenyl-3,3?,5,5??-tetracarboxylic acid, IN = isonicotinic acid) was synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, single-crystal and powder X-ray diffraction. It crystallizes in monoclinic space group C2/c with a = 33739(12), b = 14.820(5), c = 13.568(5) ?, β = 97.388(6)o, V = 6728(4) ?3, Z = 4, Mr = 965.35, Dc = 0.953 g·cm^(-3), F(000) = 1955.5, μ = 0.881 mm^(–1), GOOF = 1.072, the final R = 0.0859 and w R = 0.2424 for 5284 observed reflections with I > 2σ(I). The structure of 1 is constructed from the linkage of trinuclear {Ni_3} second building units through TPTC and IN spacers, forming a 4,8-connected network of Schl?fli symbol {32.42.52}{34.46.58.68.72}. The CO2 uptake values for 1 are 97.9 m^2·g^(-1) at 273 K and 66.2 m^2·g^(-1) at 298 K, while its N_2 adsorption values are 8.5 m^2·g^(-1) at 273 K and 4.9 m^2·g^(-1) at 298 K, respectively. These results show that 1 has high CO_2/N_2 adsorption selectivity at ambient conditions.

Synthesis,liquid crystalline and luminescent properties of trimeric phenylenevinylene with end-groups of(R)-(+)-2-methylbutyric acid ester

The trimeric phenylenevinylene with the symmetrical chiral end-groups （ChTPV） was synthesized. The liquid crystalline and luminescent properties of the ChTPV have been studied by differential scanning calorimetry （DSC）, polarized optical microscopy （POM）, absorption and photoluminescence spectra. The results indicated that the ChTPV exhibits mesophase over a wide temperature range and a typical optical texture of smectic phase. In contrast with the spectra of the solution, that of the film showed blue-shift in maximal absorption and red-shift in maximal emission due to H-type aggregation with parallel alignment of the TPV transition dipole moment.

Toughening Modification of Unsaturated Polyester Resin Using HDI Trimer

HDI trimer was firstly used to improve the mechanical properties of hydroxyl-terminated unsaturated polyester （UP）. Mechanical properties measurements performed on the cured materials demonstrate a distinct improvement in intensity and toughness in the presence of HDI trimer and shows the change trends of increase and then decrease. The morphological analysis of the fracture surfaces shows that the micro-phase separated structures appear in modified UPR systems and changed from dendritric, dimple and to cystiform structures with the increase of HDI trimer content. The presence of the cystiform structures made the modified UPR systems present the best properties.

Synthesis and Crystal Structure of a New μ-Oxamide Trimeric Hetero-tetranuclear Complex

A novel oxamide-bridged trimeric tetranuclear complex 1 incorporating a macro- cyclic oxamide of formula {[(CuL)3Mn](ClO4)2}3 (macrocyclic oxamide L = 2,3-dioxo-5,6,14,15- dibenzo-1,4,8,12-tetraazacyclopentadeca-7,12-diene) was prepared and structurally characterized. The compound [(CuL)3Mn](ClO4)2 crystallizes in the trigonal system, space group P 3 with a = 22.434(17), b = 22.434(17), c = 18.82(2) ?, α = β = 90, γ = 120o, V = 8203(13) ?3, Z = 6, Dc = 1.751g/cm3, μ(MoKα) = 1.557, F(000) = 4392, the final R = 0.083 and wR = 0.1727 for 9604 obser- ved reflections with I > 2σ(I). The single-crystal X-ray analysis shows that 1 is a trimeric complex. There are three similar constitutes, dissimilar conformations and asymmetrically independent ‘building-block’ [(CuL)3Mn] in one crystal cell of the title complex 1.