The vibrational structure of the X 1A1 - A 1B1 and A 1B1 - B 1A1 band systems of GeH2/GeD2 based on global potential energy surfaces

Transition probabilities were evaluated for the X (1)A(1)-A (1)B(1) and A (1)B(1)-B (1)A(1) systems of GeH(2) and GeD(2) to analyze the X-->A-->B photoexcitation. Franck-Condon factors (FCFs) and Einstein's B coefficients were computed by quantum vibrational calculations using the three-dimensional potential energy surfaces (PESs) of the X (1)A(1), A (1)B(1), and B (1)A(1) electronic states and the transition dipole moments for the X-A and A-B systems. The global PESs were determined by the multireference configuration interaction calculations with the Davidson correction and the interpolant moving least squares method combined with the Shepard [Proceedings of the 1968 23rd ACM National Conference (ACM, New York, 1968)] interpolation. The barriers to linearity correcting the spin-orbit interaction are evaluated to be 22,000 cm(-1) for the X state, 6300 cm(-1) for the A state, and 560 cm(-1) for the B state. The obtained FCFs for the X-A and A-B systems indicate that the bending mode is strongly enhanced in the excitation since the equilibrium bond angle greatly varies within the three states. The photoexcitation and fluorescence spectra calculated for the X-A system agree well with the observed spectra. The theoretical lifetimes for lower vibrational levels of the A and B states were calculated from the fluorescence decay rates for the A-X, B-A, and B-X emissions, and the lifetimes for the A state are in good agreement with the observed values except those affected by predissociation.     

Vibrational energies for the X1A1, A1B1, and B1A1 states of SiH2/SiD2 and related transition probabilities based on global potential energy surfaces

Transition probabilities were evaluated for the X(1)A(1)-A(1)B(1) and A(1)B(1)-B(1)A(1) systems of SiH(2) and SiD(2) to analyze the X-->A-->B photoexcitation. The Franck-Condon factors (FCFs) and Einstein's B coefficients were computed by quantum vibrational calculations using the three-dimensional potential energy surfaces (PESs) of the SiH(2)(X(1)A(1),A(1)B(1),B(1)A(1)) electronic states and the electronic transition moments for the X-A, X-B, and A-B system. The global PESs were determined by the multireference configuration interaction calculations with the Davidson correction and the interpolant moving least-squares method combined with the Shepard interpolation. The obtained FCFs for the X-A and A-B systems exhibit that the bending mode is strongly enhanced in the excitation since the equilibrium bond angle greatly varies with the three states; the barrier to linearity is evaluated to be 21,900 cm(-1) for the X state, 6400 cm(-1) for the A state, and 230-240 cm(-1) for the B state. The theoretical lifetimes for the pure bending levels of the A and B states were calculated from the fluorescence decay rates for the A-X, B-A, and B-X emissions.     

Immunological evaluation of SW-HSA conjugate on goats

Locoweeds cause significant livestock poisoning and economic loss all over the world. The purpose of this study was to investigate the immune effects of locoweed toxin, swainsonine (SW) and human serum albumin (HSA) conjugate (SW-HSA), on goats. Twenty-four Sannon goats were randomly separated into immune control group (eight goats), immune poisoning group I (six goats), immune poisoning group II (six goats) and poisoning control group (four goats). Immune control group, immune poisoning groups I and II were first vaccinated with SW-HSA conjugate. The poisoning control group, immune poisoning groups I and II were then fed with 10.0 g/kg BW/day dry powder of Oxytropis kansuensis Bunge everyday morning. The immune control group was supplied with an alfalfa-based diet. Blood samples of these experimental animals were collected at different time interval. Immunoassay was performed using indirect ELISA and E-rosette technique. The results show that, after second booster immunization: (1) anti-SW antibody level in some goats increased to 2(8), which proves that SW-HSA conjugate can induce experimental animals to produce high-level anti-SW antibody in their bodies; (2) the high-level antibody in their bodies could maintain 30 days, and decreased gradually after poisoning experiment (in our experiment, there was a return of the antibody level on day 21 after poisoning experiment); (3) the decreasing of the E-rosette rate of the immune poisoning group was delayed 14 days, which suggests that SW-HSA could low down the loss of the immunity of the goats; (4) swainsonine concentration in the blood was significantly lower (p<0.01) in the immune poisoning groups than that in the poisoning control group, and there was no significant difference (p>0.01) between the two immune poisoning groups within the poisoning experiment.     

Ab initio calculations on low-lying electronic states of TeO2 and Franck-Condon simulation of the (1)1B2 <-- X1A1 TeO2 absorption spectrum including anharmonicity

Ab initio calculations have been carried out on low-lying singlet and triplet states of TeO2 at different levels of theory with basis sets of up to the augmented-polarized valence-quintuple-zeta quality. Equilibrium geometrical parameters, harmonic vibrational frequencies, and relative electronic energies of the X1A1, 1B1, 1B2, 1A2, 3A1, 3B1, 3B2, and 3A2 states of TeO2 have been calculated. Potential energy functions (PEFs) of the X1A1 and the (1)1B2 states were computed at the complete-active-space self-consistent-field multireference configuration interaction level, with a basis set of augmented-polarized valence-quadruple-zeta quality. Franck-Condon factors (FCFs) for the electronic transition between the X1A1 and (1)1B2 states of TeO2 were calculated with the above-mentioned ab initio PEFs. The (1)1B2 <-- X1A1 absorption spectrum of TeO2 was simulated employing the computed FCFs, which include Duschinsky rotation and anharmonicity, and compared with the recently published laser-induced fluorescence (LIF) spectrum of Hullah and Brown [J. Mol. Spectrosc. 200, 261 (2000)]. The ab initio results and spectral simulation reported here confirm the upper electronic state involved in the LIF spectrum to be the (1)1B2 state of TeO2 and also confirm the vibrational assignments of Hullah and Brown. However, our simulated spectrum suggests that the reported LIF spectrum from 345 to 406 nm represents only a portion of the full (1)1B2 <-- X1A1 absorption spectrum of TeO2, which extends from ca. 406 to 300 nm. Another dye other than the two used by Hullah and Brown is required to cover the 345-300 nm region of the LIF band. Ab initio calculations show strong configuration mixing of the (1)1B2 electronic surface with higher 1B2 states in a region of large TeO bond length (> or = 2.0 A) and OTeO bond angle (> or = 135.0 degrees).     

电子激发态SO2(A^1A2, B^1B1)分子的碰撞猝灭动力学研究

用四倍频YAG激光(266nm)把SO2分子从电子基态X^1A1激励到电子激发态A^1A2和B^1B1的高振动耦合区, 通过检测自发辐射SO2(B^1B1→X^1A1)的时间分辨信号, 测定了室温(290K)下SO2(A^1A2, B^1B1)被He, 氯代甲烷分子和某些烷烃分子猝灭的速率常数。此外, 还从碰撞配合物模型出发, 对SO2(A^1A2, B^1B1)的猝灭机制进行了讨论。     

The 1 (2)A(1), 1 (2)B(2), and 1 (2)A(2) states of the SO(2) (+) ion studied using multiconfiguration second-order perturbation theory

The 1 (2)A(1), 1 (2)B(2), and 1 (2)A(2) electronic states of the SO(2) (+) ion have been studied using multiconfiguration second-order perturbation theory (CASPT2) and two contracted atomic natural orbital basis sets, S[6s4p3d1f]/O[5s3p2d1f] (ANO-L) and S[4s3p2d]/O[3s2p1d] (ANO-S), and the three states were considered to correspond to the observed X, B, and A states, respectively, in the previous experimental and theoretical studies. Based on the CASPT2/ANO-L adiabatic excitation energy calculations, the X, A, and B states of SO(2) (+) are assigned to 1 (2)A(1), 1 (2)B(2), and 1 (2)A(2), respectively, and our assignments of the A and B states are contrary to the previous assignments (A to (2)A(2) and B to (2)B(2)). The CASPT2/ANO-L energetic calculations also indicate that the 1 (2)A(1), 1 (2)B(2), and 1 (2)A(2) states are, respectively, the ground, first excited, and second excited states at the ground-state (1 (2)A(1)) geometry of the ion and at the geometry of the ground-state SO(2) molecule. Based on the CASPT2/ANO-L results for the geometries, we realize that the experimental geometries (determined by assuming the bond lengths to be the same as the neutral ground state of SO(2)) were not accurate. The CASPT2/ANO-S calculations for the potential energy curves as functions of the OSO angle confirm that the 1 (2)B(2) and 1 (2)A(2) states are the results of the Renner-Teller effect in the degenerate (2)Pi(g) state at the linear geometry, and it is clearly shown that the 1 (2)B(2) curve, as the lower component of the Renner splitting, lies below the 1 (2)A(2) curve. The UB3LYP/cc-pVTZ adiabatic excitation energy calculations support the assignments (A to (2)B(2) and B to (2)A(2)) based on the CASPT2/ANO-L calculations.     

CCl2(A1B1和a3B1)被酮类分子猝灭速率常数的测定

对CCl4/Ar混合气体脉冲直流高压放电产生CCl2自由基,经过约110μs后,再用541.52mm激光将电子基态CC2激励到激发态A1B1(0,4,0)振动态K=0能级上,通过检测激发态CCl2(A)时间分辨荧光信号,测得室温下CC2(A1B1和a3B1)被酮类分子猝灭的实验结果,用所提出的三能级模型分析处理实验数据,获得态分辨速率常数KA和Ka值.     

CCl_2(A~1B_1,a~3B_1)自由基被烷烃类分子猝灭动力学

用放电- LIF实验装置 ,对 CCl4/Ar混合气体放电产生 CCl_2自由基 ,再用 541.52 nm激光将电子基态 CCl_2激励到激发态 A~B_1(0,4,0)振动能级上 ,通过检测激发态 CCl_2时间分辨荧光信号 ,测得室温下 CCl_2(A~B_1)被烷烃类分子猝灭的实验结果 ,用我们提出的三能级模型分析处理实验数据 ,获得 CCl_2(A~1B_1)态和 CCl_2(a~3B_1)态的碰撞猝灭速率常数 k_A和 k_a值 .     

不同基质中s1p1组态的能级

研究了s1p1组态能级位置及能级劈裂同基质的关系. 结果表明, Sn2+的A、B、C带能级和In+、Tl+的A、B带能级位置同基质的环境因子he呈线性关系, 能级能量随he的增大而减小, 给出了相应的经验公式, 并计算了In+和Tl+自由离子的A、B带能级能量. 计算结果同实验数据十分吻合, 最大的偏差来自Tl+的B带, 偏差率仅为-7.34%. 随基质he的增大, 高能级能量比低能级下降得更快, A、B和C带间的能级间距相应变小. 通过对比发现: Sn2+、In+、Tl+的A、B带能级对基质的敏感性存在较大差异, Sn2+能级能量受基质变化影响最大, In+的能级能量随基质变化最小. 更为重要的是, 发现随着he的增大, Sn2+、In+和Tl+的A、B和C带能级劈裂相应变小, 甚至不再劈裂, 很好地解释了光谱现象.     

Role of hypaphorine in the toxicity of Astragalus lusitanicus

Hypaphorine, an alpha-N,N,N-trimethyltryptophan betaine, was isolated, for the first time, from Astragalus lusitanicus Lam. (Fabaceae), a plant highly toxic for lambs and goats. This alkaloid was characterized by NMR and MS analysis. Hypaphorine was previously reported to be a convulsive poison. To confirm the toxicity, it was synthesized and tested in goats. Hypaphorine was shown to be non-toxic for goats even at a high dose of 2 g kg(-1) by oral administration.     

Total synthesis of everninomicin 13,384-1--Part 1: retrosynthetic analysis and synthesis of the A1B(A)C fragment

In this first of a series of four articles we introduce everninomicin 13,384-1 (1), a powerful antibiotic effective against drug resistant bacteria, as a target for total synthesis and discuss its retrosynthetic analysis. From the three defined fragments required for the synthesis (2: A1B(A)C fragment; 4: DE fragment; 5: FGHA2 fragment), we describe herein two approaches to the A1B(A)C block. The first strategy relied on an olefin metathesis reaction to construct a common intermediate for rings B and C, but was faced with final protecting group problems. The second, and successful approach, involved a 1,2-phenylsulfeno migration and a sulfur directed glycosidation procedure to link rings B and C, as well as an acyl fluoride intermediate to install the sterically hindered aryl ester moiety (ring A1). The final stages of the synthesis of the required 2-phenylseleno glycosyl fluoride 2 required introduction of a phenylseleno group at C-1 of ring C followed by a novel, DAST-promoted 1,2-migration to produce the desired 2-beta-phenylseleno glycosyl fluoride moiety.     

Studies on tellurium-containing heterocycles. Part 20. Reactions of 2-benzoselenopyrylium salts and 2-benzotelluropyrylium salts with nucleophiles: formation of 1-functionalized 1H-isoselenochromenes and 1H-isotellurochromenes

The reactions of the 2-benzoselenopyrylium (1A) and 2-benzotelluropyrylium cations (1B) with a variety of nucleophiles have been investigated. LiAlH(4), sodium alkoxide (NaOMe, NaOi-Pr and NaOt-Bu), diethylamine, n-butylamine and acetone reacted with 1 to give the 1H-isochromenes (2) and the corresponding 1-substituted products (4-9) under mild conditions in almost good to high yields. The 1-alkyl(phenyl)isoselenochromenes (10-13) and 1-benzylisochromenes (18A, 18B), which were produced by the reaction of the salts 1 with Grignard reagents, were converted to the corresponding 1,3-disubstituted 2-benzopyrylium salts (14-17, 19) by treatment with triphenylcarbenium tetrafluoroborate (Ph(3)C(+) BF(4)(-)), respectively. The 1-benzylselenopyrylium salts (19A) and 1-benzyltelluropyrylium salts (19B) exist in the solvent as an equilibrium mixture of the salts (19) and the corresponding (Z)-benzylidene compounds (20).     

CCl_2自由基被无机小分子猝灭的速率常数

对ＣＣｌ４／Ａｒ混合气体脉冲直流高压放电产生 ＣＣｌ２自由基,用 ５４１．５２ ｎｍ激光将电子基态 ＣＣｌ２激励到Ａ１Ｂ１（０,４,０）振动能级上．通过检测激发态 ＣＣｌ２时间分辨荧光信号,测得室温下 ＣＣｌ２（Ａ１Ｂ１和 ａ３Ｂ１）被 Ｏ２、Ｎ２、ＮＯ、ＣＯ２、ＣＳ２、Ｈ２Ｏ、ＳＯ２,和ＳＦ６分子猝灭的实验结果．用我们提出的三能级模型分析处理实验数据,获得了ＣＣｌ２（Ａ１Ｂ１）态和 ＣＣｌ２（ａ３Ｂ１）态的碰撞猝灭速率常数 ｋＡ和 ｋａ值．     

Unraveling the A(1)B1 <-- X(1)A1 spectrum of CCl2: The Renner-Teller effect, barrier to linearity, and vibrational analysis using an effective polyad Hamiltonian

We report studies aimed at unraveling the complicated structure of the CCl 2 A (1)B 1 <-- X (1)A 1 system. We have remeasured the fluorescence excitation spectrum from approximately 17,500 to 24,000 cm (-1) and report the term energies and A rotational constants of many new bands for both major isotopologues (C (35)Cl 2, C (35)Cl (37)Cl). We fit the observed term energies to a polyad effective Hamiltonian model and demonstrate that a single resonance term accounts for much of the observed mixing, which begins approximately 1300 cm (-1) above the vibrationless level of the A (1)B 1 state. The derived A (1)B 1 vibrational parameters are in excellent agreement with ab initio predictions, and the mixing coefficients deduced from the polyad model fit are in close agreement with those derived from direct fits of single vibronic level (SVL) emission intensities. The approach to linearity and thus the Renner-Teller (RT) intersection is probed through the energy dependence of the A rotational constant and fluorescence lifetime measurements, which indicate a barrier height above the vibrationless level of the X (1)A 1 state of approximately 23,000-23,500 cm (-1), in excellent agreement with ab initio theory.     

The Improved Milk Quality and Enhanced Anti-Inflammatory Effect in Acetylserotonin-O-methyltransferase (ASMT) Overexpressed Goats: An Association with the Elevated Endogenous Melatonin Production

Background: Transgenic animal production is an important means of livestock breeding and can be used to model pharmaceutical applications. Methods: In this study, to explore the biological activity of endogenously produced melatonin, Acetylserotonin-O-methyltransferase (ASMT)-overexpressed melatonin-enriched dairy goats were successfully generated through the use of pBC1-ASMT expression vector construction and prokaryotic embryo microinjection. Results: These transgenic goats have the same normal phenotype as the wild-type goats (WT). However, the melatonin levels in their blood and milk were significantly increased (p < 0.05). In addition, the quality of their milk was also improved, showing elevated protein content and a reduced somatic cell number compared to the WT goats. No significant changes were detected in the intestinal microbiota patterns between groups. When the animals were challenged by the intravenous injection of E. coli, the ASMT-overexpressed goats had a lower level of pro-inflammatory cytokines and higher anti-inflammatory cytokines compared to the WT goats. Metabolic analysis uncovered a unique arachidonic acid metabolism pattern in transgenic goats. Conclusions: The increased melatonin production due to ASMT overexpression in the transgenic goats may have contributed to their improved milk quality and enhanced the anti-inflammatory ability compared to the WT goats.     

Enlarged Stable Phase Region of Hybrid Lamella-sphere Phase Enabled by A1B1A2(B2)m Branched Tetrablock Copolymer

Hybrid nanostructures possess a great potential for application in advanced nanotechnologies due to the anisotropic properties from different nanophases. Our previous work demonstrated that a linear A₁B₁A₂B₂ tetrablock copolymer of symmetric overall volume fraction can self-assemble into a hybrid lamella-sphere(LS) structure by tuning the relative length of the two A-blocks through self-consistent field theory(SCFT), where the spherical and the lamella...     

Computational study of carbon atom (3P and 1D) reaction with CH2O. Theoretical evaluation of 1B1 methylene production by C (1D)

Singlet and triplet free energy surfaces for the reactions of C atom ((3)P and (1)D) with CH(2)O are studied computationally to evaluate the excited singlet ((1)B(1)) methylene formation from deoxygenation of CH(2)O by C ((1)D) atom as suggested by Shevlin et al. Carbon atoms can react by addition to the oxygen lone pair or to the C=O double bond on both the triplet and singlet surfaces. Triplet C ((3)P) atoms will deoxygenate to give CO plus CH(2) ((3)B(1)) as the major products, while singlet C ((1)D) reactions will form ketene and CO plus CH(2) ((1)A(1)). No definitive evidence of the formation of excited singlet ((1)B(1)) methylene was found on the singlet free energy surface. A conical intersection between the (1)A' and (1)A' ' surfaces located near an exit channel may play a role in product formation. The suggested (1)B(1) state of methylene may form via the (1)A' ' surface only if dynamic effects are important. In an effort to interpret experimental observation of products trapped by (Z)-2-butene, formation of cis- and trans-1,2-dimethylcyclopropane is studied computationally. The results suggests that "hot" ketene may react with (Z)-2-butene nonstereospecifically.     

CCl2(A^1B1)自由基不同振动态的猝灭动力学

对CCl4/Ar混合气体直流脉冲放电产生CCl2自由基，再分别用波长为550.56nm,541.52nm,532.25nm,524.31nm,523.82nm和523.27nm的激光将电子基态CCl2激励到激发态A^1B1的(0,3,0),(0,4,0),(1,3,0),(0,6,0),(1,4,0),(2,2,0)振动态，激发态CCl2(A^1B1)的不同振动态的时间分辨荧光信号显示该信号呈双指数衰减，测得室温下CCl2(A^1B1)不同振动态被NH3,H2O,CH2Br2,NH(CH3)2,NH(C2H5)2,N(C2H5)3,n-C6H14等分子猝灭的实验结果，用三能级模型分析处理实验数据，获得态分辨速率常数kA和ka值，并对实验结果进行了讨论。