Sensitive single-layered oxygen-sensing systems: polypyridyl ruthenium(II) complexes covalently attached or deposited as langmuir-blodgett monolayer on glass surfaces

Oxygen-sensing elements containing single-layered structures of luminescent indicators of ruthenium(II) bipyridyl complexes on glass surfaces prepared by covalent attachment and LB deposition are described. They are capable of detecting gaseous oxygen concentration by luminescence quenching of the indicator with reproducible and large quenching efficiencies that are comparable to the best quenching efficiencies obtained by other ruthenium(II) polypyridine based complexes immobilized in matrixes. The large quenching efficiencies for both films imply that the probe complexes are effectively quenched by oxygen, which is probably due to the thin single-layered structures with large surface-to-area ratio and short distance between the probe complexes and oxygen.     

Non-zwitterionic structures of aliphatic-only peptides mediated the formation and dissociation of gas phase radical cations

We have investigated how the non-zwitterionic and zwitterionic structures of aliphatic-only tripeptides affect the formation and dissociation of peptide radical cations in the gas phase. The non-zwitterionic forms of the aliphatic-only peptides in their metal complexes play an important role in determining whether the electron transfer pathway predominates. We extended this study by synthesizing permanent non-zwitterionic and zwitterionic forms of aliphatic-only peptide radical cations and exploring their reactivities in the gas phase. Collision-induced dissociation spectra demonstrated the feasibility of generating both non-zwitterionic and zwitterionic forms. Radical cations in zwitterionic forms may indeed mediate the beta and gamma carbon-carbon bond cleavages of leucine and isoleucine side chains from the GlyGlyXle radical peptides; this feature allows leucine and isoleucine residues to be distinguished unambiguously.     

Influence of electric field intensity, ionic strength, and migration distance on the mobility and diffusion in DNA surface electrophoresis

In order to increase the separation rate of surface electrophoresis while preserving the resolution for large DNA chains, e.g., genomic DNA, the mobility and diffusion of Lambda DNA chains adsorbed on flat silicon substrate under an applied electric field, as a function of migration distance, ionic strength, and field intensity, were studied using laser fluorescence microscope. The mobility was found to follow a power law with the field intensity beyond a certain threshold. The detected DNA peak width was shown to be constant with migration distance, slightly smaller with stronger field intensity, but significantly decreased with higher ionic strength. The molecular dynamics simulation demonstrated that the peak width was strongly related with the conformation of DNA chains adsorbed onto surface. The results also implied that there was no diffusion of DNA during migration on surface. Therefore, the Nernst-Einstein relation is not valid in the surface electrophoresis and the separation rate could be improved without losing resolution by decreasing separation distance, increasing buffer concentration, and field intensity. The results indicate the fast separation of genomic DNA chains by surface electrophoresis is possible.     

A sheath-flow nanoelectrospray interface of microchip electrophoresis MS for glycoprotein and glycopeptide analysis

Microchip was coupled with MS through a stable, sensitive, and controllable sheath-flow nanoelectrospray (nES) interface for glycoprotein and glycopeptide analysis. The nano-ESI (nESI) was made with a delivery capillary, a commercial nES capillary, and a stainless steel (SS) tube which were connected together through a tee unit. High voltage for nES was applied on the SS tube and the commercial nES capillary was used as nES emitter. The delivery capillary was attached to the microchannel for delivering liquid from microchip to the nESI source. The flow rate of sheath liquid was optimized to be 100-200 nL/min which largely reduced the sample dilution. The detection limit of peptides on this microchip/MS platform was at femtomole level. Glycoprotein and glycopeptides were also successfully analyzed on the platform. All the glycoforms and glycopeptides of ribonuclease B (RNase B) were identified with this method. Some structures of the glycopeptides from RNase B were further characterized with MS/MS on the microchip, coupled with a quadrupole IT-MS.     

A disk-pivot structure micro piezoelectric actuator using vibration mode B11

Micro piezoelectric actuator using vibration mode B(11) (B(mn), where m is the number of nodal circles, n is the nodal diameters) is designed. Different from conventional wobble-type ultrasonic motor using piezoelectric rod or cylinder, piezoelectric disc is used to excite wobble modes and metal cylinder stator is used to amplify the transverse displacement, metal rod rotor is actuated to rotate. The outer diameter of the actuator is 14mm. There are features such as low drive voltage, micromation, and convenient control of wobble state by modifying the structure of stator, etc. Finite element analysis (FEA) of the stator has been made. It is found that the resonant frequency of vibration mode B(11) is 49.03kHz, which is measured at 45.7kHz by the laser vibrometer and impedance analyzer. The rotation speed has been measured, which could be as high as 10,071rpm under an alternating current 100V. Such piezoelectric actuator can be optimized and adjusted to fit practical conditions. It can be applied in the fields of precise instrument, bioengineering and other micro actuator system.     

The geometric pattern of a pillared substrate influences the cell-process distribution and shapes of fibroblasts

Fibroblasts alter their shape, direction of movement, cytoskeleton arrangement, and focal contact when placed upon square array pillars. We prepared pillars of 1 μm diameter, separated by 3 μm, and having 1, 5, and 10 μm heights using substrates displaying identical surface chemistry. When cells seeded initially onto the tops of the pillars, fibroblasts subsequently were immobilized in situ by several pillars that visibly protruded through, but did not pierce, the cell bodies. The cytoplasma then migrated outward with long straight lamella along the interval of the pillars and formed several discrete attachment zones at their side walls – the value of their form index (FI) was as high as 35 – which altered the cellular shape entirely. Most of the cells interacted with the pillar substrate by spreading preferentially in a particular direction, but some of them had the ability to undergo coincident two-direction (x and y) migration; right-angle turn orientations led to the growth of dramatic cellular morphologies. Interestingly, this fibroblast's behavior variation was gradually in proportion to the pillar height of substrate. Our results confirm that cellular migration and cellular shape are both strongly affected by the geometry of the growth microenvironment.     

Adhesion model of side contact for an extensible elastic fiber

For accurately predicted adhesion laws of fibrillar structures contribute to the rational design of high-performance biomimetic adhesives, an adhesion model is proposed to study the directional adhesion behavior of an extensible elastic fiber that contacts a rigid smooth surface with its side surface under the coupling effect of normal and shear forces, based on the extensible Euler Bernoulli beam theory and the surface energy concept. The deformed configuration of the fiber is obtained analytically, and on the basis of this result, the detachment mode and the normal pull-off force of the fiber for a given shear force are predicted directly. It is also found that, due to the extensibility of the fiber, there exists a maximum normal pull-off force (MNPF) when an optimal shear force is applied. The MNPF will be enhanced by increasing the axial stiffness, and reduced by increasing the bending stiffness. In addition, generating an optimal pre-tension in the adhered part of the fiber will maximize the MNPF. The derived adhesion law is expected to contribute to the optimal design and applications of single-level fibrillar adhesives.     

Investigation on Non-covalent Complexes of Cyclodextrins with Li+ in Gas Phase by Mass Spectrometry

To investigate the non-covalent interaction between cyclodextrins (CD) and lithium ion, a stoichiometry of α-CD, β-CD, heptakis(2,6-di-O-methyl)-β-CD (DM-β-CD), or heptakis(2,3,6-tri-O-methyl)-β-CD (TM-β-CD) was mixed with lithium salt, respectively, and then incubated at room temperature for 10 min to reach the equilibrium. In posi-tive mode, the electrospray ionization mass spectrometry (ESI-MS) results demonstrated that lithium ion can conjugate to α-, β-, DM-β- or TM-β-CD and form 1:1 stoichiometric non-covalent complexes. The binding of the complexes was further confirmed by collision-induced dissociation. The dissociation constants K_d1 of four complexes (Li+α-CD, Li+β-CD, Li+DM-β-CD, and Li+TM-β-CD) were determined by mass spectrometric titration. The results showed K_d1 were 18.7, 26.7, 33.6, 30.5 μmol/L for the complexes of Li+ with α-CD, β-CD, DM-β-CD, and TM-β-CD, respectively. K_d1 for the Li⁺ complexes of β-CD is smaller than that of DM-β-CD due to its steric effect of the partial substituted -CH₃. The Kd1 for the Li⁺ complexes of DM-β-CD is nearly in agreement with that of TM-β-CD, indicating Li⁺ is more likely to locate in the small rim of DM-β-CD's hydrophobic cavity. The DFT results showed through electrostatic interaction, one Li+ can strongly conjugate to four neighboring oxygen atoms. For the (α-CD+Li)⁺ complex, one Li⁺ may also situate the small rim of α-CD's hydrophobic cavity to form a non-specific host-guest complex.     

气相自由基反应动力学的光电离质谱研究

气相自由基能与各种气体发生快速反应,在大气化学、燃烧化学和星际化学等重要的化学过程中起着关键性的催化作用。许多实验方法(例如荧光法和吸收法)已经用于研究气相自由基反应动力学过程,并取得许多重要的成果,但这些技术局限于探测小分子自由基反应。流动管反应器和闪光光解结合光电离质谱的实验技术以其通用性、多重探测性、选择性和灵敏性等多种优势,成为研究气相自由基反应的主要实验方法。本文介绍利用高通量、高分辨、连续可调的同步辐射光电离质谱开展多种自由基反应研究所取得的一些独创性的成果。另外,该技术具有独有的时间分辨、能量分辨和异构体分辨的能力,能够广泛用于大气化学、燃烧化学和星际化学中一些重要的气相自由基(如烷氧自由基、烃类自由基等)反应宏观动力学过程的研究。     

Multi-element analysis by ArF laser excited atomic fluorescence of laser ablated plumes: Mechanism and applications

A new multi-element analysis technique based on laser-excited atomic fluorescence was reviewed. However, the one-wavelength-one-transition constraint was overcome. Numerous elements were induced to fluoresce at a single excitation wavelength of 193 nm. This was possible provided that the analytes were imbedded in dense plumes, such as those produced by pulsed laser ablation. The underlying mechanism of the technique was explained and corroborated. Analytical applications to metals, plastics, ceramics and their composites were discribed. Detection limits in the ng/g range and mass limits of atto moles were demonstrated. Several real-world problems, including the analysis of paint coating for trace lead, the non-destructive analysis of potteries and ink, the chemical profiling of electrode-plastic interfaces, and the analysis of ingestible lead colloids were discussed.