Electrochemical DNA biosensor for the detection of interaction between di[azino-di(5,6-azafluorene)-κ-NN′]dichlormanganous and DNA

A new Mn(II) complex of MnL₂Cl₂ (L = azino-di(5,6-azafluorene)-κ²-NN′) was synthesized and utilized as an electrochemical indicator for the determination of hepatitis B virus (HBV) based on its interaction with MnL₂Cl₂. The electrochemical behavior of interaction of MnL₂Cl₂ with salmon sperm DNA was investigated on glassy carbon electrode (GCE). In the presence of salmon sperm DNA, the peak current of [MnL₂]²⁺ was decreased and the peak potential was shifted positively without appearance of new peaks. The binding ratio between [MnL₂]²⁺ and salmon sperm DNA was calculated to be 2:1 and the binding constant was 3.72 × 10⁸ mol² L⁻². The extent of hybridization was evaluated on the basis of the difference between signals of [MnL₂]²⁺ with probe DNA before and after hybridization with complementary sequence. Control experiments performed with non-complementary and mismatch sequence demonstrated the good selectivity of the biosensor. With this approach, a sequence of the HBV could be quantified over the range from 1.76 × 10⁻⁸ to 1.07 × 10⁻⁶ mol L⁻¹, with a linear correlation of r = 0.9904 and a detection limit of 6.80 × 10⁻⁹ mol L⁻¹. Additionally, the binding mechanism was preliminarily discussed. The mode of interaction between MnL₂Cl₂ and DNA was found to be primary intercalation binding.     

Effects of carbon chain on hole-transport properties in naphtho[2,1-b:6,5-b′]difuran derivatives: Remarkable anisotropic mobilities

Theoretical investigations of hole-transport properties in two naphtho[2,1-b:6,5-b′]difuran derivatives as novel p-type organic semiconductor based on the Marcus–Hush theory combining quantum mechanics are carried out. This work focuses on the effects of carbon chain on molecular orbitals, partial charge difference, ionization potential, internal energy relaxation, and hole-transport behaviors. Through computational modeling, we are shedding light on the favorable function of C8-DPNDF single crystal as p-type organic material. With the introduction of octyl group, C8-DPNDF single crystal possesses high hole-transfer mobilites (1.589 cm² V⁻¹ s⁻¹) and remarkable anisotropic behavior. The simulated anisotropic mobility curve of C8-DPNDF demonstrates the maximum value of the mobility appears when the measuring conducting channel is along the b-axis of the single crystal. The adiabatic ionization potential (AIP) and vertical ionization potential (VIP) of C8-DPNDF are about 6.312 and 6.399 eV, that is, slightly smaller than those of DPNDF. The relatively small IP values can ensure effective hole injection from the source electrode. The data obtained from the present work can be used to prove that C8-DPNDF molecule has the potential to develop into high-efficient p-type organic semiconductor materials, whose hole-transport mobility can be further improved when the measuring transistor channel is controlled carefully.     

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 π-π 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.     

基于铜(Ⅱ)4,5-二氮芴-9-酮连氮配合物为指示剂的DNA电化学生物传感器的研究

运用电化学方法研究了铜(Ⅱ)4,5-二氮芴-9-酮连氮配合物[CuL·(H2O)2]·(NO3)2CHCl3(L=4,5-二氮芴-9-酮连氮)与DNA的相互作用,并提出了以其为电化学探针测定DNA的方法.在最佳条件下,峰电流的减小值与DNA浓度呈线性关系,由此建立了一种测定DNA的电化学分析方法,该方法的线性范围为1.69×10-6～2.34×10-7 g·L-1,线性回归方程为△Ip=0.077 4cDNA-0.886 3(n=11,γ=0.9886),检测限为1.23×10-8 g·L-1.     

BODIPY derivatives as n-type organic semiconductors: Isomer effect on carrier mobility

In the present work, two dipyrro-boradiazaindacenes (BODIPY) derivatives functioning as novel high-performance organic semiconductors are investigated by theoretical method. These two isomeric complexes are demonstrated to have large electron-transfer mobility, which means they are favor to be n-type organic semiconductors. The highest electron-transfer mobility appears at the same packing style in two crystals. The intermolecular distances of the packing style are nearly same, 4.994 Å in crystal 1 and 5.283 Å in crystal 2. However, their electron-transfer mobility changes significantly. The mobility of crystal 2 with better planar molecular structure is 0.291 cm² V⁻¹ s⁻¹, which is 13 times larger than that of crystal 1 as 0.022 cm² V⁻¹ s⁻¹. The significant difference of carrier mobility is ascribed to the little structural difference of these two isomers. It has been demonstrated that both crystal 1 and 2 show remarkable anisotropic behavior. This study will undoubtedly provide a new understanding of isomerization on designing novel organic semiconductors.     

Hydrogen bonding in the electronic excited state

Because of its fundamental importance in many branches of science, hydrogen bonding is a subject of intense contemporary research interest. The physical and chemical properties of hydrogen bonds in the ground state have been widely studied both experimentally and theoretically by chemists, physicists, and biologists. However, hydrogen bonding in the electronic excited state, which plays an important role in many photophysical processes and photochemical reactions, has scarcely been investigated. Upon electronic excitation of hydrogen-bonded systems by light, the hydrogen donor and acceptor molecules must reorganize in the electronic excited state because of the significant charge distribution difference between the different electronic states. The electronic excited-state hydrogen-bonding dynamics, which are predominantly determined by the vibrational motions of the hydrogen donor and acceptor groups, generally occur on ultrafast time scales of hundreds of femtoseconds. As a result, state-of-the-art femtosecond time-resolved vibrational spectroscopy is used to directly monitor the ultrafast dynamical behavior of hydrogen bonds in the electronic excited state. It is important to note that the excited-state hydrogen-bonding dynamics are coupled to the electronic excitation. Fortunately, the combination of femtosecond time-resolved spectroscopy and accurate quantum chemistry calculations of excited states resolves this issue in laser experiments. Through a comparison of the hydrogen-bonded complex to the separated hydrogen donor or acceptor in ground and electronic excited states, the excited-state hydrogen-bonding structure and dynamics have been obtained. Moreover, we have also demonstrated the importance of hydrogen bonding in many photophysical processes and photochemical reactions. In this Account, we review our recent advances in electronic excited-state hydrogen-bonding dynamics and the significant role of electronic excited-state hydrogen bonding on internal conversion (IC), electronic spectral shifts (ESS), photoinduced electron transfer (PET), fluorescence quenching (FQ), intramolecular charge transfer (ICT), and metal-to-ligand charge transfer (MLCT). The combination of various spectroscopic experiments with theoretical calculations has led to tremendous progress in excited-state hydrogen-bonding research. We first demonstrated that the intermolecular hydrogen bond in the electronic excited state is greatly strengthened for coumarin chromophores and weakened for thiocarbonyl chromophores. We have also clarified that the intermolecular hydrogen-bond strengthening and weakening correspond to red-shifts and blue-shifts, respectively, in the electronic spectra. Moreover, radiationless deactivations (via IC, PET, ICT, MLCT, and so on) can be dramatically influenced through the regulation of electronic states by hydrogen-bonding interactions. Consequently, the fluorescence of chromophores in hydrogen-bonded surroundings is quenched or enhanced by hydrogen bonds. Our research expands our understanding of the nature of hydrogen bonding by delineating the interaction between hydrogen bonds and photons, thereby providing a basis for excited-state hydrogen bonding studies in photophysics, photochemistry, and photobiology.