光驱动单向分子转子的研究进展

分子转子是分子马达设计的要件,有关分子转子的讨论已经引起广泛的关注.主要介绍2003年以来单向转动型分子转子的研究状况,重点讨论其构效关系和应用方面的最新进展,展望了分子转子的发展前景并指出其面临的挑战.

红光发射分子转子的设计与合成

粘度对细胞微环境的维持非常重要。检测细胞内的粘度一般采用分子转子,而目前大多数的分子转子发射波长较短,不利于生物成像,为此我们设计了基于扭转分子内电荷转移(TICT)机理,通过共轭双键连接吸电子基和给电子基的红光发射的分子转子2-(2-(4-氨基苯乙烯基)-4-H-吡喃-4-亚基)-丙二腈(DCM-NH_2)。DCM-NH_2的最大发射波长为631 nm,属于远红光,能有效减少生物背景,提高成像信噪比。该探针对粘度有很好的响应,具有非常宽的线性响应范围(0.6~458.6 c P),同时也具有较高的灵敏度。

Research Advance on Molecular Mechanism of Abiotic and Biotic Stress Resistance in Sweet Potato

Sweet potato（Ipomoea batatas） is not only an important food crop, but also an important economic crop and energy crop. In recent years, as the develop- ment of molecular biology techniques, more and more abiotic and biotic stress-related genes were discovered in sweet potato. These genes can be divided into two categories： the regulatory genes and the functional genes, according to their different roles in stress pathways. This paper reviews the abiotic and biotic stress-related genes cloning, functional analysis and exogenous genes application in sweet potato, and makes expectation for stress resistance research of sweet potato in the future.

Advances in development and industrial applications of ethylbenzene processes

The benzene alkylation process for the production of ethylbenzene has undergone significant improvements during recent decades.Various environmentally benign zeolite-catalyzed ethylbenzene processes,including ZSM-5-zeolite-based vapor-phase ethylbenzene processes and Y-,β-,and MCM-22-zeolite-based liquid-phase processes,have been developed and commercialized.Pure ethylene,ethanol,and dilute ethylene have been used as ethylation agents.Here,the development and industrial application of alkylation catalysts and benzene ethylation techniques are summarized,and some other promising innovations are discussed.Recent advances in benzene alkylation over hierarchical zeolites with improved access to active sites and molecular transport are also covered.Zeolites with short diffusion lengths are promising candidates as better alkylation catalysts.The key point is how to obtain such materials easily and economically.The structure-activity relationships of commercial zeolites in these processes are discussed.Liquid-phase processes catalyzed by β and MCM-22 are more profitable than vapor-phase processes catalyzed by ZSM-5.

Separation of Ions from Volatile Organic Compounds Using High-Field Asymmetric Waveform Ion Mobility Spectrometry-Mass Spectrometer

A combination of high-field asymmetric waveform ion mobility spectrometry （FAIMS） with mass spectrometer （MS） was analyzed. FAIMS separates ions from the volatile organic compounds in the gas-phase as an ion-filter for MS. The sample ions were created at ambient pressure by ion source, which was equipped with a 10.6 eV UV discharge lamp （A=116.5 nm）. The drift tube of FAIMS is composed of two parallel planar electrodes and the dimension is 10 mm×8 mm×0.5 mm. FAIMS was investigated when driven by the high-filed rectangular asymmetric waveform with the peak-to-peak voltage of 1.36 kV at the frequency of 1 MHz and the duty cycle of 30%. The acetone, the butanone, and their mixture were adopted to characterize the FAIMS-MS. The mass spectra obtained from MS illustrate that there are ion-molecular reactions between the ions and the sample neutral molecular. And the proton transfer behavior in the mixture of the acetone and the butanone is also observed. With the compensation voltage tuned from -30 V to 10 V with a step size of 0.1 V, the ion pre-separation before MS is realized.

Cloning and Expression Analysis of PtFATB Gene Encoding the Acyl-acyl Carrier Protein Thioesterase in Populus tomentosa Carr

Acyl-ACP thioesterases （FATs） terminates the fatty acid synthesis and allow the transport of fatty acids out of the plastids, which are the important determinants of cellular metabolism. FATB is a member of FAT enzymes that has been described previously in most of the plants. In silico cloning is a new method that utilizes the bioinformatics on the complete genome and available EST database. In this study, a full-length cDNA clone of PtFATB gene was isolated from Populus tomentosa using this approach. It is 1,450 bp in length and the open reading frame encodes a peptide of 421 amino acids. The predicted amino acid sequence shows significant homology with those from other plant species, which contain typical domains owned by FATB proteins. The transcripts of PtFATB were abundant in leaves, and less in roots detected by using semiquantitative RT-PCR. When the shoots were subjected to the stress treatments （cold, dry, NaC1） and ABA （Abscisic acid）, the expression of PtFATB was only slightly reduced under the treatment of low temperature. This suggests that the expression of PtFATB is in a constitutive fashion. This study provides the basis not only for the identification and characterization of this gene but also for the improvement of cold tolerance by controlling the expression of the PtFATB gene in trees in near future.

Synthesis of Schiff Base Bearing Phenolic Hydroxy Group and Its Anion Recognition

A new anion receptor bearing phenolic hydroxy group based on 3,5- ditertbutylsalicylaldehyde-p-nitrophenylhydrazone （1） was designed and synthesized. Upon addition of AcO- and F-, the receptor exhibited visible color changes from deep yellow to purple. However, no obvious color changes were observed on addition of the other anions tested （H2PO4-, Cl-, Br-, I-）. The binding properties of the receptor with anions such as AcO and F- were investigated by UV-Vis and fluorescent titrations. The result indicated that the receptor 1 had a higher affinity to AcO- and F- and a 1：1 host-guest complex was formed through H-bond interactions between 1 and anions.

Derivatives of 4-dihydroquinolinone and their fluorescent property

A series of donor-π-acceptor （D-π-A） compounds involving varied donors and acceptors as well as a dihydroquinolinone moiety were synthesized. Tuned fluorescent colors from blue to orange were successfully realized in them. Spectroscopic analysis exhibits that the increased conjugated system, enhanced electrondonating ability of acceptor, and electron-withdrawing ability of donor result in red shift in both absorption and fluorescence for these compounds. Both the absorption and fluorescence show strong bathochromic shift effect with the increase in the polarity of solvents. It indicates that they are intramolecular charge transfer （ICT） fluorescent compounds and may have potential application as novel electroluminescent material.

Experimental and Theoretical Investigation on Excited State Intramolecular Proton Transfer Coupled Charge Transfer Reaction of Baicalein

The excited state intramolecular proton transfer （ESIPT） coupled charge transfer of baicalein has been investigated using steady-state spectroscopic experiment and quantum chemistry calculations. The absence of the absorption peak from S1 excited state both in the experi-mental and calculated absorption spectra indicates that S1 is a dark state. The dark excited state S1 results in the very weak fluorescence of solid baicalein in the experiment. The fron- tier molecular orbital and the charge difference densities of baicalein show clearly that the S1 state is a charge-transfer state whereas the S2 state is a locally excited state. The only one stationary point on the potential energy profile of excited state suggests that the ESIPT reaction of baicalein is a barrierless process.

Heme:a versatile signaling molecule controlling the activities of diverse regulators ranging from transcription factors to MAP kinases

Heme （iron protoporphyrin IX） is an essential molecule for numerous living organisms. Not only does it serve as a prosthetic group in enzymes, it also acts as a signaling molecule that controls diverse molecular and cellular processes ranging from signal transduction to protein complex assembly. Deficient heme synthesis or function impacts the hematopoietic, hepatic and nervous systems in humans. Recent studies have revealed a series ofheme-regulated transcription factors and signal transducers including Hap 1, a heme-activated transcription factor that mediates the effects of oxygen on gene transcription in the yeast Saccharomyces cerevisiae; Bachl, a transcriptional repressor that is negatively regulated by heme in mammalian cells; IRR, an iron regulatory protein that mediates the iron-dependant regulation of heme synthesis in the bacterium Bradyrhizobiumjaponicum; and heme-regulated inhibitor, an eucaryotic initiation factor 2α kinase that coordinates protein synthesis with heme availability in reticulocytes. In this review, we summarize the current knowledge about how heme controls the activity of these transcriptional regulators and signal transducers, and discuss diseases associated with defective heme synthesis, degradation and function.

Rotational Analysis of A^2∏u-X^2∏g System of 16O2^＋ Cation

The Doppler-limited absorption spectrum of 16O2^＋ cation was observed in the region of 11385-12100 cm^-1 by optical heterodyne velocity modulation absorption spectroscopy （OH-VMS）. The transitions were assigned to the （2, 19）, （3, 20）, and （5, 21） bands in the second negative system （A^2∏u-X^2∏g）. All the available lines measured using OH-VMS were global fitted in a nonlinear least-squares fitting procedure, and precise molecular constants （Bv, Av, Dv, pv, qv, γv） were obtained for the involved levels.

Computer Assisted Assignments of Rotationally Resolved Molecular Spectra

A graphically oriented interactive program for assignments of rotationally resolved molecular spectra has been devised. The program functions by grouping spectral lines in term of the second difference principle. and graphing spectral intensity versus frequency in a bar graph of the selected groups, distinguished by color and/or line-type. This allows for easy detection of regular patterns buried in the observed spectrum. Furthermore, it includes a Loomis-Wood view for assisting in spectral assignments. As an example, the program was applied in assigning the molecular spectrum of the production in the discharge of PCl3 buffered by helium gas, which may belong to several species. The results suggest that the program is highly efficient and quite useful in the assignment and the analysis of molecular spectra, especially those of symmetric top, slightly asymmetric top and linear molecules. The accuracy and efficiency of this program will likely ensure its wide application in the processing of molecular spectra.

Molecular mechanism of TNF signaling and beyond

Tumor necrosis factor (TNF) is a proinflammatory cytokine that plays a critical role in diverse cellular events, including cell proliferation, differentiation and apoptosis. TNF is also involved in many types of diseases. In recent years, the molecular mechanisms of TNF functions have been intensively investigated. Studies from many laboratories have demonstrated that the TNF-mediated diverse biological responses are achieved through activating multiple signal- ing pathways. Especially the activation of transcription factors NF-κB and AP-1 plays a critical role in mediating these cellular responses. Several proteins, including FADD, the death domain kinase RIP and the TNF receptor associated factor TRAF2 have been identified as the key effectors of TNF signaling. Recently, we found that the effector mol- ecules of TNF signaling, such as RIP and TRAF2, are also involved in other cellular responses. These finding suggests that RIP and TRAF2 serve a broader role than as just an effector of TNF signaling.

Rotational Analysis of A2Ⅱu-X2∑g＋ System of 14N2＋

The absorption spectrum of N2＋ has been studied using optical-heterodyne velocity mod- ulation spectroscopy in the near-infrared region. The observed spectral lines were assigned to the （3,1）, （4,2）, （5,3）, （8,5） bands of the A2Ⅱu-X2∑g＋ system and the line lists were pro- vided. The （5,3） band was studied for the first time. Fourteen rotational-resolved bands in literatures were fitted together with our observed bands and the molecular constants were obtained for VA=0-9 and vx=0-5.

Ultrafast Electron Transfer in All-Small-Molecule Photovoltaic Blends Promoted by Intermolecular Interactions in Cyanided Donors

Cyano substitution has been established as a viable approach to optimize the performance of all-small-molecule organic solar cells.However,the effect of cyano substitution on the dynamics of photo-charge generation remains largely unexplored.Here,we report an ultrafast spectroscopic study showing that electron transfer is markedly promoted by enhanced intermolecular charge-transfer interaction in all-small-molecule blends with cyanided donors.The delocalized excitations,arising from intermolecular interaction in the moiety of cyano-substituted donor,undergo ultrafast electron transfer with a lifetime of∼3 ps in the blend.In contrast,some locally excited states,surviving in the film of donor without cyano substitution,are not actively involved in the charge separation.These findings well explain the performance improvement of devices with cyanided donors,suggesting that manipulating intermolecular interaction is an efficient strategy for device optimization.

Theoretical Study of Electron Transferin Bimolecular System of NH_3 and H_2O

Mulliken, NPA, MK and CHelpG population analyses have been accomplished at the level of MP2/6-31G（d,p） for the title system. The variations of four kinds of charges on NH3 with intermolecular distance infer that electron transfers from NH3 to H2O. MK and CHelpG population analyses indicate more electron transfer than Mulliken and NPA ones. The atomic charges resulted from MK and CHelpG schemes infer that electron transfers from N in NH3 to H in H2O, which confirms that this bimolecular complex possesses linear structure as H3N…HOH.

Photo-Induced Intermolecular Electron Transfer-Effect of Acceptor Molecular Structures

Photo-induced electron transfer versus molecular structure of acceptors is investigated using ultrafast time-resolved transient grating spectroscopy. Typical laser dyes Rhodamine 101 (Rh101) and Rhodamine 6G (Rh6G) in electron donor solvent-aniline are adopted as the objects. The forward electron transfer time constant from aniline to the excited singlet state of two Rhodamine dyes and subsequent back electron transfer from two dyes to aniline are measured. The experimental results denote that Rh6G presents faster electron transfer rates with aniline in both forward electron transfer and back electron transfer processes. With chemical calculation and qualitative analysis, it is found that the flexible molecular geometry of Rh6G leads to stronger electron coupling with donor solvent and further gives rise to larger electron transfer rates.

Optical Properties and Response Mechanism Analysis of Multi-branched Fluorescent Probes Based on Intramolecular Charge Transfer

In this work, the optical properties of fluorescent probes used for detection of biothiol were studied by employing time-dependent density functional theory. By calculating the single photon absorption and emission properties of probe Mol.1, Mol.2 and Mol.3 before and after reaction with cysteine and homocysteine, we have investigated the effect of carboncarbon triple bond and benzene ring on the properties of fluorescent probes. It is found that the oscillator strength of probe molecules increases gradually with the improvement of the structure of the electron donor triphenylamine and the addition of carbon-carbon triple bonds, and better properties of fluorescence probes have also been demonstrated. At the same time, the effect of different number of side branches on the molecular properties of the probe was also studied. The results showed that compared with single-branched molecule Z1 and tribranched probe Mol.3, two side probe molecules Z2 had higher oscillator strength and better detection effect. In addition, the new single-branched probe Mol.4 with the addition of carbon-carbon triple bonds and benzene rings has better probe properties and simpler structure than the tribranched probe Mol.3.

Photoinduced Electron Transfer in Dumbbell-type Fullerene Dyad

1,3-Dipolar cycloaddition of DTE-azomethine ylides （DTE： dithienyl-ethene） to C60 in refluxed toluene was used to synthesize novel dumbbell-type fullerene dimer 1. For the sake of comparison, the monoadduct 2 were also synthesized. The molecular geometries of these two compounds were determined by theoretical calculations with HF-3/21G method. UV-Vis and fluorescence experiments were carried out in solvents with different polarity at the room temperature. All the results indicated the existence of a photoinduced intramolecular electron transfer process between the donor and acceptor moieties.

Regulation of Excited-State Intramolecular Proton Transfer Process and Photophysical Properties for Benzoxazole Isothiocyanate Fluorescent Dyes by Changing Atomic Electronegativity

Excited-state intramolecular proton transfer(ESIPT)is favored by researchers because of its unique optical properties.However,there are relatively few systematic studies on the effects of changing the electronegativity of atoms on the ESIPT process and photophysical properties.Therefore,we selected a series of benzoxazole isothiocyanate fluorescent dyes(2-HOB,2-HSB,and 2-HSe B)by theoretical methods,and systematically studied the ESIPT process and photophysical properties by changing the electronegativity of chalcogen atoms.The calculated bond angle,bond length,energy gap,and infrared spectrum analysis show that the order of the strength of intramolecular hydrogen bonding of the three molecules is 2-HOB<2-HSB<2-HSe B.Correspondingly,the magnitude of the energy barrier of the potential energy curve is 2-HOB>2-HSB>2-HSe B.In addition,the calculated electronic spectrum shows that as the atomic electronegativity decreases,the emission spectrum has a redshift.Therefore,this work will offer certain theoretical guidance for the synthesis and application of new dyes based on ESIPT properties.