The elastic theory of a single DNA molecule

We study the elastic responses of double-(ds) and single-stranded (ss) DNA at external force fields. A double-strand-polymer elastic model is constructed and solved by path integral methods and Monte Carlo simulations to understand the entropic elasticity, cooperative extensibility, and supercoiling property of dsDNA. The good agreement with experiments indicates that short-ranged base-pair stacking interaction is crucial for the stability and the high deformability of dsDNA. Hairpin-coil transition in ssDNA is studied with generating function method. A threshold force is needed to pull the ssDNA hairpin patterns, stabilized by base pairing and base-pair stacking, into random coils. This phase transition is predicted to be of first order for stacking potential higher than some critical level, in accordance with experimental observations.     

Smaller Output Beam Divergence in the Slowly Opened Q-Switch Operation

The mechanism of the slowly opened Q-switch operation was investigated thoroughly. Maximum energy extraction from the resonator could be optimized, and the smallest output beam divergence could be achieved. In this article, we present a detailed analysis that has numerically verified the mode-selection mechanism in the slowly opened Q-switch operation, and the degree of the smaller output laser beam divergence that has been achieved. The mechanism of the slowly opened Q-switch operation is the inherent advantage of the passive saturable absorber in this operation. We can use the maximum energy extraction and the smallest output beam divergence results of the slowly opened Q-switch operation to design and optimize various passive saturable absorbers: plastic dye sheets, LiF:F₂⁻ color center crystals, Cr4⁺: YAG crystals, RG1000 color glass filters, and the single crystal semiconductor saturable absorber wafers that are in developed in our microchip laser systems.     

Synthesis and biological evaluation of novel 1, 2, 3-benzotriazin-4-one derivatives as leukotriene A4 hydrolase aminopeptidase inhibitors

A series of novel 1,2,3-benzotriazin-4-one derivatives were designed,synthesized and their inhibitory activities against leulcotriene A_4 hydrolase aminopeptidase in vitro were evaluated.Many compounds showed moderate to good activities at the concentration of 10 μmol/L.Among them,compound Ⅳ-16 exhibited the highest inhibitory activity up to 80.6% with an IC_(50) of 1.30 ± 0.20 μmol/L The compound Ⅳ-16 was also tested the proliferation inhibitory activities in THP1 human AML cell line and its binding model with LTA_4H enzyme by molecular docking was studied.It indicated that 1,2,3-benzotriazin-4-one was a promising scaffold for further study.The relationship between structure and inhibitory activity was also preliminarily discussed.     

A new family of supramolecular multiferrocenyl rhomboids:Synthesis,characterization,and their electrochemical behavior

Two novel,supramolecular,multiferrocenyl rhomboids 5 and 6 have been successfully constructed from newly designed 60 ferrocenyl donor precursor 1 via coordination-driven self-assembly.The structures of all multiferrocenyl rhomboids were characterized by multinuclear NMR(¹H and ³¹P),CSI-TOF-MS, and PM6 semi-empirical molecular simulation,and their electrochemical behaviors have been investigated.     

A New Probe for Mechanical Testing of Nanostructures in Soft Materials

We report a new application of the optical tweezers, where a harmonically driven oscillating tweezer is combined with the forward light scattering and lock-in amplification techniques, for probing the mechanics of nanostructures in soft materials in a broad frequency range. Model independent dynamic moduli G and G of the material at a localized, sub-micron area can be measured directly from the displacement and the phase shift of the particle in the oscillating trap. The probe particles can be as small as 200nm and the displacement of the particle was in the range of a few nanometers. To illustrate the new methodology, we show the microscopic viscoelastic properties of a transient polymer network in the vicinity of a silica bead.     

Structural and optical properties of ZnS/niobate composites synthesized by exfoliation/self-assembly processing

A new ZnS/niobate composite was first synthesized through two processes: (1) self-assembly of [Ca₂Nb₃O₁₀]_nⁿ⁻ nanosheets in Zn(NH₃)₄²⁺ solution; (2) formation of ZnS/niobate composite by adding Na₂S to the former reacting system. X-ray diffraction (XRD) result shows that the as-prepared ZnS/niobate composite can be indexed to tetrahedral symmetry with a=5.450(2) and c=16.904(7) Å. The uniform distributions of Zn, Ca, Nb, S and O element in the particles were demonstrated by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The optical property of the composite was characterized by photoluminescence spectra and UV-vis absorption spectra.     

Probing the Binding of Rifampicin to Bovine Serum Albumin in Aqueous Solution

The binding of rifampicin (RFP), an anti-tuberculosis agent, to bovine serum albumin (BSA) was studied at physiological conditions (pH=7.40) by a spectroscopic approach. In the discussion of the quenching mechanism, it was proved that the fluorescence quenching of BSA by RFP is a result of the formation of a RFP–BSA complex. Binding parameters were determined using the modified Stern-Volmer equation and Scatchard’s equation to provide a measure of the binding affinity between RFP and BSA. The resulting thermodynamic parameters ΔG, ΔH, and ΔS at different temperatures indicate that electrostatic interactions play a major role in RFP–BSA association. Site marker competitive displacement experiments demonstrate that RFP binds with high affinity to the site I (subdomain IIA) of BSA. Furthermore, the effect of metal ions on the RFP–BSA system was studied, and the specific binding distance r (3.38 nm) between donor and acceptor (RFP) was obtained according to the fluorescence resonance energy transfer (FRET).     

On frequency waves

A new type of wave existing in the frequency domain is deduced and named a frequency wave. For a homogeneous medium, we have obtained the approximate and rigorous solutions of a frequency shift equation for plane radiation under some special, one-sided or two-sided frequency shift conditions.     

Direct measurements of colloidal hydrodynamics near flat boundaries using oscillating optical tweezers

We studied the hydrodynamic interaction between a colloidal particle close to flat rigid boundaries and the surrounding fluid using oscillating optical tweezers. A colloidal particle located near walls provides a model system to study the behavior of more complex systems whose boundaries can be modeled as effective walls, such as a blood tube, cell membrane, and capillary tube in bio-MEMS. In this study, we measure the hydrodynamic interaction directly without using the Stokes–Einstein relation. Two different cases are studied: a colloidal sphere near a single flat wall and a colloidal sphere located at the midplane between two flat walls. The colloidal hydrodynamics is measured as a function of the distance between the particle and the walls, and is compared with the theoretical results from well-defined hydrodynamics approximations.     

Shapes of lipid monolayer domains: Solutions using elliptic functions

Solid lipid monolayer domains surrounded by a fluid phase at an air-water interface exhibit complex shapes. These intriguing shapes can be understood in terms of a competition between line tension and long-range dipole-dipole interaction. The dipolar energy has recently been relevant to a negative line tension and a positive curvature energy at the boundary, and a corresponding shape equation was derived by the variation of the approximated domain energy (Phys. Rev. Lett. 93, 206101 (2004)). Here we further incorporate surface pressure into the shape equation and show that the equation can be analytically solved: the curvature of the domain boundary is exactly obtained as an elliptic function of arc-length. We find that a circular domain can grow into bean-and peach-like domains with pressure, i.e., dipping and cuspidal transitions of circle by compression. The comparison with the experimental observation shows nice agreement.