1,3-双(1-苯基-1H-四唑-5-巯基)-乙酰苯腙钳形受体对卤素阴离子的识别机理

采用密度泛函B3LYP(Becke, three-parameter, Lee-Yang-Parr)和HF(Hatree-Fock)方法, 从理论上探讨了1,3-双(1-苯基-1H-四唑-5-巯基)-乙酰苯腙(DAPHZ)钳形受体对卤素阴离子的识别机理,结果发现DAPHZ受体以其钳形结构中的-N-H基团与卤素阴离子间形成双侧红移氢键进行识别. 经BSSE校正后DAPHZ•••F-, DAPHZ•••Cl-和DAPHZ•••Br-体系的分子识别相互作用能ΔECP分别为-327.5,-163.5和-148.3 kJmol-1, 说明钳形DAPHZ受体对F-具有最好的识别能力. 此外, 采用自然键轨道(NBO)计算, 相关H原子化学位移计算及分子中原子(AIM)等理论分析了识别体系中红移氢键的电子结构和性质, 结果表明APHZ受体对卤素阴离子的识别能力的相对顺序为DAPHZ•••F- >> DAPHZ•••Cl- ≈ DAPHZ•••Br-.     

Raman and mid-infrared spectroscopic study of geometrically frustrated hydroxyl cobalt halides at room temperature

Mid-infrared absorption and Raman spectra of the geometrically frustrated material series,hydroxyl cobalt halides β-Co 2 (OH) 3 Cl and β-Co 2 (OH) 3 Br,are first,to the best of our knowledge,measured at room temperature,to study the corresponding relationship between their vibrational spectral properties and crystal microstructures.Through the comparative analysis of the four spectra we have categorically assigned the OH-related vibration modes of hydroxyl groups in the trimeric hydrogen bond environment (Co 3 ≡OH) 3… Cl/Br,and tentatively suggested vibration modes of O-Co-O,Co-O and Cl/Br-Co-Cl/Br units.These results can also become the basis for analysing their low-temperature spectral properties,which can help to understand the underlying physics of their exotic geometric frustration phenomena around phase transition temperatures.     

Complex formation between a nanoparticle and a weak polyelectrolyte chain: Monte Carlo simulations

Understanding the complexation processes between nanoparticles and polyelectrolytes is an essential aspect in many branches of nanotechnology, nanoscience, chemistry, and biology to describe processes such as nanoparticle stabilization/destabilization and dispersion, water treatment, microencapsulation, complexation with biomolecules for example, and evolution of the interface of many natural and synthetic systems. In view of the complexity of such processes, applications are often based on empirical or semiempirical observations rather than on predictions based on theoretical or analytical models. In this study, the complex formation between an isolated weak polyelectrolyte and an oppositely charged nanoparticle is investigated using Monte Carlo simulations with screened Coulomb potentials in the grand canonical ensemble. The roles of the nanoparticle surface charge density , solution pH and ionic concentration C_i are systematically investigated. The phase diagrams of complex conformations are also presented. It is shown that the polyelectrolyte conformation at the surface of the nanoparticle is controlled by the attractive interactions with the nanoparticle but also by the repulsive interactions between the monomers. To bridge the gap with experiments titration curves are calculated. We clearly demonstrate that an oppositely charged nanoparticle can significantly modify the acid/base properties of a weak polyelectrolyte.     

Inflation,large scale structure and particle physics

We review experimental and theoretical developments in inflation and its application to structure formation, including the curvaton idea. We then discuss a particle physics model of supersymmetric hybrid inflation at the intermediate scale in which the Higgs scalar field is responsible for large scale structure, show how such a theory is completely natural in the framework extra dimensions with an intermediate string scale.     

Profiling of generic anti-phosphopeptide antibodies and kinases with peptide microarrays using radioactive and fluorescence-based assays

Kinases represent one of the largest enzyme families and key regulatory proteins in the cell. Only a small subset of these enzymes has been characterised so far. We have prepared different types of phosphopeptide and peptide microarrays displaying peptides deduced from annotated human phosphorylation sites and cytoplasmic domains of all annotated human membrane proteins. This approach was enabled by fully-automated high throughput micro-scale synthesis of peptides by the SPOT technology combined with chemo-selective immobilisation on modified glass slides. The phosphopeptide microarrays displaying 2923 peptides in total have been used for the characterisation of commercially available generic anti-phosphopeptide antibodies. This enabled us to detect Abl kinase activity on a microarray with anti-phosphotyrosine antibodies yielding results comparable to those obtained from a radioactive assay. More than 13 000 peptides deposited on six glass slides were used to profile casein kinase 2 (CK2) using a radioactive assay, since no generic antibody for the reliable detection of serine or threonine phosphorylation could be identified. All previously identified substrates were detected in the microarray experiment. In order to confirm whether substrates on the microarray are substrates in solution phase assays, more than 700 peptides were synthesised and tested with CK2 in a solution phase assay. All substrates identified in the solution phase assay were also detected on the microarray.     

External noise and its interaction with spatial degrees of freedom in nonlinear dissipative systems

A brief introduction to the field is given together with an overview of the lectures given at the workshop on External Noise and its Interaction with Spatial Degrees of Freedom in Nonlinear Dissipative Systems organized by the Center for Nonlinear Studies at Los Alamos, March 28–31, 1988. It is hoped that the publication of papers presented at the workshop in a single issue of theJournal of Statistical Physics will help draw attention to the recent developments in this rapidly area of nonequilibrium phenomena.     

Polarization of line radiation in the presence of external electric quadrupole and uniform magnetic fields: II. Arbitrary orientation of magnetic field

In continuation of our earlier investigation (referred to hereafter as part I) where we considered the mathematically simple case of magnetic field orientation along the Z-axis of the principal axes frame (PAF) of the electric quadrupole field, we take up here the general problem of arbitrary orientation of the magnetic field with respect to the PAF, and investigate the nature of polarized line spectra of an atom making a transition from an upper level with spin J_u to a lower level with spin J_l. Explicit formulae for the emitted Stokes parameters are obtained and we discuss their physical significance by computing numerically the cases of transitions J_u=1→J_l=0 and . Specific features or signatures of the polarized line spectra are discussed as functions of the relevant physical parameters. The Stokes parameters are also analyzed in terms of the Zeeman term contributions and the cross-term contributions (which arise due to quantum interference).     

Nonlinear competition between asters and stripes in filament-motor systems

A model for polar filaments interacting via molecular motor complexes is investigated which exhibits bifurcations to spatial patterns. It is shown that the homogeneous distribution of filaments, such as actin or microtubules, may become either unstable with respect to an orientational instability of a finite wave number or with respect to modulations of the filament density, where long-wavelength modes are amplified as well. Above threshold nonlinear interactions select either stripe patterns or periodic asters. The existence and stability ranges of each pattern close to threshold are predicted in terms of a weakly nonlinear perturbation analysis, which is confirmed by numerical simulations of the basic model equations. The two relevant parameters determining the bifurcation scenario of the model can be related to the concentrations of the active molecular motors and of the filaments, respectively, which both could be easily regulated by the cell.     

Search for Higgs Boson in UHE Cosmic Rays

Considering the SM Higgs boson mass in the range of (95–235) GeV, we present here a mechanism for indirect searches of this scalar in UHE cosmic rays interactions. The mechanism is the decay of Higgs bosons which are produced through bubble formation due to vacuum excitation in an UHE cosmic rays interactions with air nuclei. We develop a model of hadronic interaction based on algorithms of the GENCL code of the UA5 experiment of CERN and some physics of CORSIKA code (Karlsruhe report), incorporating a fraction of energy transfer to bubble formation through vacuum excitation and subsequent multiparticle production via conversion of Higgs boson to heavy fermion pairs. Such events are expected to have high multiplicity and excess muons. This mechanism has significant effect starting from E _P 10¹⁸eV. It is found that the average muon number decreases gradually upto 175 GeV Higgs boson mass and remain practically constant thereafter for all primary energies (E _P) above 10¹⁸ eV and for all fractions of energy transfer (f _e 0.01–0.5). The fluctuation of muon multiplicity decreases with E _P and increases very slowly with Higgs mass upto 175 GeV, remaining practically invariant thereafter.     

Peptide mimotopes of phomopsins: Identification, characterization and application in an immunoassay

Peptide mimotopes of plant-associated toxins offer the potential for improving analytical and diagnostic methodologies as well as providing candidates for potential protective vaccines against plant poisoning diseases. Monoclonal antibody (mAb) C₃C₁₁, which recognizes the antimicrotubule phomopsin mycotoxins, was used to isolate peptide mimics of phomopsin A from a random 15-mer phage display peptide library. A total of 46 clones were isolated that showed specific reactivity with the mAb. Amino acid sequence analysis revealed four different types of mimotope sequences, all of which contained a common motif V-A-L/V-C. Of the 46 clones isolated, 44 contained the motif V-A-L-C while 2 contained the V-A-V-C motif. All four types of phage clones inhibited the reactivity of the mAb with phomopsin A in a competition ELISA. The clone with the mimotope sequence CT VALCNMYFGAKLD demonstrated the strongest binding. It was further shown that synthetic peptides containing these mimotope amino acid sequences were able to inhibit the mAb-phomopsin A interaction, indicating that the peptide mimotopes were responsible for the specific binding, independent of the phage framework. The results also suggest that the mimotope peptides bind to mAb C₃C₁₁ at the same site as phomopsin A. The application of recombinant phage particles carrying phomopsin mimotopes in immunoassay was evaluated and the results demonstrated approximately 100-fold increase in sensitivity in comparison with a conventional immunoassay using a chemically linked phomopsin-horseradish peroxidase conjugate.