发色团光化学的氢键效应

Intermolecular hydrogen bonding, as a site-specific interaction between hydrogen donor and acceptor molecules, is a very important type of solute-solvent interactions. It is central to the understanding of microscopic structure and function in many molecular systems, such as hydrogen-bonded water or alcohols networks, chromophores, proteins, and DNA building blocks of the life. Furthermore, it also plays an important role on the photochemistry of the hydrogen-bonded systems in their electronically excited states. In this talk, we have reviewed our recent investigations about the hydrogen bonding effects on the photochemistry of chromophores in solution. The electronically excited states of chromophores were theoretically studied using the time-dependent density functional theory (TDDFT) method. At the same time, the infrared spectra in the ground state and electronically excited state of chromophores were also simulated. By monitoring the spectral shifts of some characterized vibrational modes involved in the formation of hydrogen bonds in different electronic states, it has been demonstrated for the first time that the intermolecular hydrogen bonds between chromophores and hydrogen donating solvents are significantly strengthened in the electronically excited state. This hydrogen bonding dynamics of photoexcited chromophores occurs on ultrafast timescales mainly set by vibrational motions of the hydrogen donor and acceptor groups, and it controls the excited-state dynamics of hydrogen-bonded complexes in a significant way. We have demonstrated that the radiationless deactivation via internal conversion (IC) from the fluorescent state to the ground state can be enhanced by the hydrogen bond strengthening in the excited state. The solute-solvent intermolecular photoinduced electron transfer (ET) reaction, which is facilitated by the hydrogen bond strengthening, has been proposed to account for the drastic fluorescence quenching behaviors of chromophores in alcoholic solvents. Moreover, the site-specific solvation dynamics can also be induced by the hydrogen bond strengthening in the electronically excited state

Steered molecular dynamics simulation study on dynamic self-assembly of single-stranded DNA with double-walled carbon nanotube and graphene

In the present work, we explored the diameter selectivity of dynamic self-assembly for the single-strand DNA (ssDNA) encapsulation in double-walled nanotubes (DWNTs) via molecular dynamics simulation method. Moreover, the pulling out process was carried out by steered molecular dynamics simulations. Considering pi-pi stacking and solvent accessibility together, base-CNT binding should be strongest on a graphene sheet and weakest on the inner CNT surface. When pulling the ssDNA out of the single-walled carbon nanotube (SWNT), the force exhibits characteristic fluctuations around a plateau about 300 pN. Each fluctuation force pulse to pull ssDNA corresponds to the exit of one base. In addition, the solvents used for the system are also of significant interest. Water does play an important role in encapsulation process but doesn't in the pulling out process

Molecular dynamics simulation exploration of unfolding and refolding of a ten-amino acid miniprotein

Steered molecular dynamics simulations are performed to explore the unfolding and refolding processes of CLN025, a 10-residue beta-hairpin. In unfolding process, when CLN025 is pulled along the termini, the force-extension curve goes back and forth between negative and positive values not long after the beginning of simulation. That is so different from what happens in other peptides, where force is positive most of the time. The abnormal phenomenon indicates that electrostatic interaction between the charged termini plays an important role in the stability of the beta-hairpin. In the refolding process, the collapse to beta-hairpin-like conformations is very fast, within only 3.6 ns, which is driven by hydrophobic interactions at the termini, as the hydrophobic cluster involves aromatic rings of Tyr1, Tyr2, Trp9, and Tyr10. Our simulations improve the understanding on the structure and function of this type of miniprotein and will be helpful to further investigate the unfolding and refolding of more complex proteins

Control continuum bandwidth and attosecond pulse generation by infrared laser parametric source

Control continuum bandwidth and attosecond pulse generation by infrared laser parametric sourceWe present quantum and classical investigation on high order harmonic generation from two-color scheme by employing different infrared (ir) laser parametric source as control pulse with locked carrier envelope phase. We found harmonic continuum bandwidth is in the function of the negative square of the ir-control pulse's wavelength from ir parametric source control field. Moreover, harmonic continuum bandwidth shows a linear dependence on the relative strength ratio k and achieves its extreme value when relative phase shift is around zero. A broad continuum with spectral width of 264 eV is observed from a combination field by 6 fs, 800 nm, 6x10(14) W/cm(2) few-cycle fundamental pulse and half-harmonic control pulse with k = 0.5. By further applying a second 10-um ir control pulse, a continuum beyond 353 eV is obtained which supports the generation of an isolated 12 attosecond (as) pulse

石斑鱼生殖调控和性别分化相关基因的克隆与鉴定

石斑鱼是重要的海水养殖鱼类,同时也是人工繁殖与育苗技术难度最大的海产鱼类之一。制约其人工规模化养殖的一个关键因素是雄性亲鱼的培育。石斑鱼个体发育中普遍存在“先雌后雄”的性转变过程,雄亲鱼均高龄化。具有天然性反转现象的石斑鱼无疑是研究鱼类生殖调控和性别分化的一个理想系统。因此,本研究围绕生殖内分泌调控轴,在构建石斑鱼性腺、下丘脑和垂体的相应文库,筛选和克隆到一批参与生殖和性腺分化的重要功能基因的基础上,采