Preparation of ω-tetrahydropyran-2-ylsulfanylalkylmagnesium chlorides: Useful reagents for the synthesis of 1-(ω-mercaptoalkyl)-1,2-dihydrobuckminsterfullerenes (C60)

ω-Tetrahydropyran-2-ylsulfanylalkylmagnesium chlorides are prepared as Grignard reagents containing protected mercaptoalkyl chains, which are useful for the direct introduction of ω-mercaptoalkyl chains to electrophiles. In order to prove the usefulness of these reagents, they were reacted with buckminsterfullerene (C₆₀) to give 1-(ω-mercaptoalkyl)-1,2-dihydrobuck minsterfullerenes after the deprotection of THP group with TFA.     

从头计算方法比较TiSi_2的C54相和C49相

采用平面波超软赝势描述多电子体系,利用密度泛函理论和广义梯度近似,计算出C54相和C49相TiSi2的晶格常数、体弹性模量、形成能、电子态密度(DOS)和Mulliken电荷布居等性质.通过比较这两种物质的性质,发现尽管两者形成能很相近,但C49相结构对称性差、体弹性模量小、熔点低,Ti原子d轨道的反键强、离子性弱.这些性质上的差异和C49相TiSi2在固相反应中优先形成有关.     

分数导数结合傅里叶最小二乘拟合处理含噪音的重迭信号

提出了一种含噪音重迭信号的综合处理方法 :先用傅里叶最小二乘法拟合噪音数据 ,然后对拟合后的信号求 2 .5次导数 ,在对模拟数据研究的基础上 ,讨论了求导后峰位漂移及其影响因素 ,给出了一个用于矫正峰位值的经验公式。用该方法对模拟和实际的紫外含噪音重迭信号进行处理 ,结果良好     

Octasilsesquioxane Chemistry II. Hydrosilylation Reaction of Octa(hydrido)silsesquioxane with Unsaturated Substrates and Product Properties

The hydrosilylation reaction of octa(hydrido)silsesquioxane with ω‐halo‐1‐alkenes and other unsaturated substrates allows attachment of 8 long‐chain functionalized alkyls on the cubic Si₈O₁₂ skeleton. Pt/C and H₂PtCl₆ have been adopted as the catalysts, the yields being 74–98% for compounds 2–9 . For terminal alkenes, the hydrosilylation follows the anti‐Markonikov's rule. The morphological state of 2–9 ranges from viscous liquid to crystalline materials. The pyrolysis results indicate that 7 , a material of hard spherical core and soft flexible shell, may likely act as nanometer‐size ball bearings up to more than 400 °C. The X‐ray structure of 9 reveals that the molecule is required to possess a center of symmetry crystallographically. The linear arms on 9 , except for two of them, are virtually all‐trans in conformation, not counting the ω‐C‐Cl bond.     

Equivalence of functional-differential equations of neutral type and abstract Cauchy problems

Equivalence of functional-differential equations of neutral type to well-posed abstract Cauchy problems in the state spaces ⁿ }L ^p ,L ^p resp.C is investigated. The assumptions allow non-atomic difference operators.This work was supported by the Fonds zur Förderung der wissenschaftlichen Forschung (Austria) under Grant No. P4534.Work done by this author was done during a stay at the University of Graz from October 1981 till April 1984.     

Loniceroside C,an antiinflammatory saponin from Lonicera japonica

A new triterpenoid saponin, loniceroside C was isolated from the aerial parts of Lonicera japonica. Its structure was established to be 3-O-beta-D-glucopyranosyl hederagenin 28-O-alpha-L-rhamnopyranosyl (1-->2)-[beta-D-xylopyranosyl(1-->6)]-beta-D-glucopyranosyl ester by spectroscopic techniques and chemical transformations. Loniceroside C showed in vivo antiinflammatory activity against mouse ear edema provoked by croton oil.     

An azo dye for photodynamic therapy that is activated selectively by two-photon excitation

Two-photon photodynamic therapy (TP-PDT) is a promising approach for the treatment of cancer because of its better penetration depth and superior spatial selectivity. Here, we describe an azo group containing cyclized-cyanine derivatives (ACC1 and ACC2) as a two-photon activated, type I based photosensitizer (PS). These small-molecule and heavy atom-free organic dyes showed marked reactive oxygen species (ROS)-generating ability under physiological conditions, as well as fast loading ability into the cells and negligible dark toxicity. Live cell analyses with one- and two-photon microscopy revealed that these dyes showed higher ROS generation ability upon two-photon excitation than upon one-photon excitation via the type I process. The PSs have superior PDT properties compared to conventional Visudyne and 5-ALA under mild conditions. These characteristics allowed for precise PDT at the target region in mimic tumor spheroids, demonstrating that the developed TP PS could be useful in efficient PDT applications and in designing various PSs.

Azo containing dyes as a two-photon selective and type I based photosensitizers (PSs) were developed that exhibit excellent photodynamic therapy properties under mild condition.     

Intriguing self-assembly of large granules of F-actin facilitated by gelsolin and alpha-actinin

We report microscopic observations and a structural determination of actin granules self-assembled in concentrated solutions of actin filaments (F-actin). Optical microscopy shows reproducible formation of numerous and stable granules of densely packed F-actin of variable sizes on the order of 10 microm. These granules coexist with a uniform network of F-actin of a lower concentration. The microscopic segregation of F-actin into two distinct states is assisted by an actin cross-linking protein, alpha-actinin. The rapid on and off rates and temperature sensitivity of the alpha-actinin/F-actin interaction facilitate the formation of multi-micrometer-sized granules of well-defined shapes. Additional physical factors such as the excluded volume effect and the minimization of surface energy act in concert with the specific molecular interactions to define the intriguing granular formation. Both the biochemical specificity of alpha-actinin and the thermodynamics of phase transitions are required for understanding such large scale self-assembly.     

Highly sensitive and simple fluorescence staining of proteins in sodium dodecyl sulfate-polyacrylamide-based gels by using hydrophobic tail-mediated enhancement of fluorescein luminescence

Fluorescein has an extremely low luminescence intensity in acidic aqueous media. However, when it was bound to proteins, subsequent increase of luminescence intensity took place. Furthermore, when a hydrophobic tail, such as aliphatic hydrocarbons, was introduced to fluorescein, more dramatic increase of luminescence intensity was observed upon binding to proteins. In the present study, by utilizing this luminescence enhancement, three hydrophobic fluorescein dyes (5-dodecanoyl amino fluorescein, 5-hexadecanoyl amino fluorescein, and 5-octadecanoyl amino fluorescein) were examined as noncovalent fluorescent stains of protein bands in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Effective incorporation of the dyes to proteins in gels was accomplished either simply by adding dyes at the protein fixation step, or by treating gels with a staining solution after the fixation. The sensitivity of this staining method using the fluorescein derivatives was approximately 1 ng/band for most proteins. For some cases, protein bands containing as low as 0.1 ng were successfully visualized. In addition, the detection sensitivity showed much less protein-to-protein variation than silver staining. This new staining method was also successfully applied to two-dimensional electrophoresis of rat brain proteins. Its overall sensitivity was comparable to that of silver staining.     

Kinetics of thermal depolymerization of trimethylsiloxy end-blocked polydimethylsiloxane and polydimethylsiloxane-N-phenylsilazane copolymer

The thermal degradation of Me₃SiO end-blocked polydimethylsiloxane (eb-PDMS) and polydimethylsiloxane-N-phenylsilazane (eb-PDMS–NPhSz) copolymer was studied. For both polymers relative degree of polymerization (DP /DP ₀) as a function of conversion (1 – W/W₀) data were obtained. For eb-PDMS the results were consistent with a mechanism involving a rate determining random siloxane bond cleavage initiation step followed by a rapid and complete depropagation of the active fragments evolving volatile cyclic oligomers. Rate constants (k) for initiation were obtained at four temperatures from plots of DP ^?1 vs. time. An Arrhenius activation energy of approximately 80 kcal/mol was determined and is consistent with a SiOSi scission transition state. The degradation of eb-PDMS–NPhSz appears to follow the same depolymerization process evolving cyclic oligomers. Although DP /DP ₀ vs. C data suggest a random cleavage–complete depolymerization mechanism, an Arrhenius plot suggests a more complex degradation mechanism. The role of impurities as degradation catalysts is discussed.