ANALYSIS OF STABILITY ON ELASTIC PLATES WITH INITIAL IMPERFECTIONS

ＡＮＡＬＹＳＩＳＯＦＳＴＡＢＩＬＩＴＹＯＮＥＬＡＳＴＩＣＰＬＡＴＥＳＷＩＴＨＩＮＩＴＩＡＬＩＭＰＥＲＦＥＣＴＩＯＮＳＸｕＫａｉｙｕ（徐凯宇）（ＲｅｃｅｉｔｅｄＯｃｔ．５，１９９４．ＣｏｍｍｕｎｉｃａｔｅｄＰａｉＬｉｚｈｏｕ）ＡＮＡＬＹＳＩＳＯＦＳＴＡ...     

蛋白质多态解折叠行为与稳定性Ⅱ:酶的多态解折叠行为

基于结构基元模型,进一步假设,由n个结构基元组成的蛋白酶,其活性中心由na(na?n)个结构基元组成,酶活性仅与组成活性中心的结构基元相关.由此,推导出适合于蛋白酶解折叠研究的变性曲线、解折叠结构基元平均自由能、物种分布等表达式.本文以盐酸胍诱导的卵清溶菌酶解折叠为例,通过荧光方法测定的溶菌酶解折叠曲线,得出卵清溶菌酶由2个结构基元组成,结构基元平均自由能?G0element(H2O)为48.47 kJ/mol.物种分布表明,酶活性随盐酸胍浓度的变化仅仅反映的是结构基元1(?-片结构域)的解折叠,而结构基元2(?-螺旋结构域)的解折叠反映在3.8~5.0 mol/L盐酸胍浓度范围内.结构基元模型既可描述蛋白酶多态解折叠的谱学行为,又可解释蛋白酶活性的两态性质.     

Equivariant multiparameter bifurcation via singularity theory

The theoretical machinery from singularity theory introduced by Golubitsky, Stewart, and Schaeffer, to study equivariant bifurcation problems, is completed and expanded while generalized to the multiple parameter context. In this setting the finite determinacy theorems or normal forms, the stability of equivariant bifurcation problems, and the structural stability of the universal unfolding are discussed.     

Bifurcation analysis of an arch structure with parametric and forced excitation

The subharmonic bifurcation and universal unfolding problems are discussed for an arch structure with parametric and forced excitation in this paper. The amplitude–frequency curve and some dynamical behavior have been shown for this class of problems by Liu et al. Here, by means of singularity theory, in the case of strict 1:2 internal resonance, the bifurcation behavior of the amplitude with respect to a parameter (which is related to the amplitude of the live load imposed on the arch structures) is studied. The results indicate that it is a high codimensional bifurcation problem with codimension 5, and the universal unfolding is given. From the mechanical background, 20 forms of two parameter unfoldings with some constraints are studied. The transition sets in the parameter plane and the bifurcation diagrams are plotted. The results obtained in this paper present some new dynamic buckling patterns and abundant bifurcation phenomena.     

The Denaturant- and Mutation-Induced Disassembly of Pseudomonas aeruginosa Hexameric Hfq Y55W Mutant

Although oligomeric proteins are predominant in cells, their folding is poorly studied at present. This work is focused on the denaturant- and mutation-induced disassembly of the hexameric mutant Y55W of the Qβ host factor (Hfq) from mesophilic Pseudomonas aeruginosa (Pae). Using intrinsic tryptophan fluorescence, dynamic light scattering (DLS), and high-performance liquid chromatography (HPLC), we show that the dissociation of Hfq Y55W occurs either under the effect of GuHCl or during the pre-denaturing transition, when the protein concentration is decreased, with both events proceeding through the accumulation of stable intermediate states. With an extremely low pH of 1.4, a low ionic strength, and decreasing protein concentration, the accumulated trimers and dimers turn into monomers. Also, we report on the structural features of monomeric Hfq resulting from a triple mutation (D9A/V43R/Y55W) within the inter-subunit surface of the protein. This globular and rigidly packed monomer displays a high thermostability and an oligomer-like content of the secondary structure, although its urea resistance is much lower.     

Assessing the Functional and Structural Stability of the Met80Ala Mutant of Cytochrome c in Dimethylsulfoxide

The Met80Ala variant of yeast cytochrome c is known to possess electrocatalytic properties that are absent in the wild type form and that make it a promising candidate for biocatalysis and biosensing. The versatility of an enzyme is enhanced by the stability in mixed aqueous/organic solvents that would allow poorly water-soluble substrates to be targeted. In this work, we have evaluated the effect of dimethylsulfoxide (DMSO) on the functionality of the Met80Ala cytochrome c mutant, by investigating the thermodynamics and kinetics of electron transfer in mixed water/DMSO solutions up to 50% DMSO v/v. In parallel, we have monitored spectroscopically the retention of the main structural features in the same medium, focusing on both the overall protein structure and the heme center. We found that the organic solvent exerts only minor effects on the redox and structural properties of the mutant mostly as a result of the modification of the dielectric constant of the solvent. This would warrant proper functionality of this variant also under these potentially hostile experimental conditions, that differ from the physiological milieu of cytochrome c.     

Sur les notions de quasi-homogénéité de feuilletages holomorphes endimension deux

In this note, we recall the different notions of quasi-homogeneity for singular germs of holomorphic foliations in the plane presented in [6]. The classical notion of quasi-homogenity allude to those functions which belong to its own jacobian ideal. Given a foliation in the plane, asking that the equation of the separatrix set is a classical quasi-homogeneous function we obtain a natural generalization in the context of foliations. On the other hand, topological quasi-homogeneity is characterized by the fact that every topologically trivial deformation whose sepatrix family is analytically trivial is an analytically trivial deformation. We give an explicit example of a topological quasi-homogeneous foliation which is not quasi-homogeneous in the sense given above.

     

Normal linear stability of quasi-periodic tori

We consider families of dynamical systems having invariant tori that carry quasi-periodic motions. Our interest is the persistence of such tori under small, nearly-integrable perturbations. This persistence problem is studied in the dissipative, the Hamiltonian and the reversible setting, as part of a more general kam theory for classes of structure preserving dynamical systems. This concerns the parametrized kam theory as initiated by Moser [J.K. Moser, On the theory of quasiperiodic motions, SIAM Rev. 8 (2) (1966)145-172; J.K. Moser, Convergent series expansions for quasi-periodic motions, Math. Ann. 169 (1967) 136-176] and further developed in [G.B. Huitema, Unfoldings of quasi-periodic tori, PhD thesis, University of Groningen, 1988; H.W. Broer, G.B. Huitema, F. Takens, Unfoldings of quasi-periodic tori, Mem. Amer. Math. Soc. 83 (421) (1990) 1-82; H.W. Broer, G.B. Huitema, Unfoldings of quasi-periodic tori in reversible systems, J. Dynam. Differential Equations 7 (1) (1995) 191-212]. The corresponding nondegeneracy condition involves certain (trans-)versality conditions on the normal linear, leading, part at the invariant tori. We show that as a consequence, a Cantor family of Diophantine tori with positive Hausdorff measure is persistent under nearly-integrable perturbations. This result extends the above references since presently the case of multiple Floquet exponents is included. Our leading example is the normal resonance, which occurs a lot in applications, both Hamiltonian and reversible. As an illustration of this we briefly describe the Lagrange top coupled to an oscillator.     

Interface water-induced hydrophobic carbon chain unfolding in water

The folding and unfolding of the carbon chain, which is the basic constitutional unit of polymers,are important to the performance of the material. However, it is difficult to regulate conformational transition of the carbon chain, especially in an aqueous environment. In this paper, we propose a strategy to regulate the conformational transition of the carbon chain in water based on the all-atom molecular dynamics simulations. It is shown that the unfolded carbon chain will spontaneously collapse into the folded state, while the folded carbon chain will unfold with an external electric field. The regulation ability of the electric field is attributed to the electric field-induced redistribution of interface water molecules near the carbon chain. The demonstrated method of regulating conformational transition of the carbon chain in water in this study provides an insight into regulating hydrophobic molecules in water, and has great potential in drug molecule design and new polymer material development.     

A Novel Method for Screening G‐quadruplex Stabilizers to Human Telomeres

We present a simple method based on the Cu²⁺ induced unfolding of G‐quadruplex (G4) of human telomere sequence d[AG₃(T₂AG₃)₃] to screen a number of 3,6‐bis(1‐methyl‐4‐vinylpyridinium)carbazole diiodide (BMVC) analogues for better G4 stabilizers. Using circular dichroism (CD), the screening results suggest that the tri‐cations of 9‐substituted BMVC derivatives are better G4 stabilizers than the bi‐cations of BMVC. In addition, 3,6‐bis(1‐methyl‐4‐vinylpyrazinium)carbazole diiodide (BMVC4) is likely a better core molecule than BMVC for G4 stabilizers.