Single generator problem

Using the Stone-\v{C}ech compactification of integers, we introduce a free extension of an almost periodic flow. Together with some properties of outer functions, we see that, in a certain class of ergodic Hardy spaces , , the corresponding subspaces are all singly generated. This shows the existence of maximal weak- Dirichlet algebras, different from of the disc, for which the single generator problem is settled.

     

Method of kinetic analysis of photodegradation: nifedipine in solutions

A rate equation for photodegradation was derived from Lambert-Beer's law and Grotthus-Draper's law: -dc/dt=k1(1-exp(-(k2c+k3(c0-c))))k2c/(k2c+k3(c0-c)) where c is the concentration of reactant, c0 is the initial concentration of reactant, t is time, k1 is the rate constant, and k2 and k3 are the absorption coefficient of reactant and its photodegradation product, respectively. In a case where the photodegradation products have no photoabsorption, k3 assumes the value of zero in the above general equation. In a case where the photodegradation products have the same spectrum and molar absorptivity as that of the reactant, k3 assumes the value of k2, and hence the photodegradation is not a first-order reaction; however, the equation itself gives the pseudo-first-order reaction rate equation. In a case where the concentration of reactant is high enough, the equation approaches a zero-order reaction rate equation. The photodegradation rate of nifedipine in solutions under a germicidal lamp, near an ultraviolet fluorescent lamp and a fluorescent lamp was analyzed using the above equation. The photodegradation rate was directly proportional to the amount of light absorbed, and fitted well with the equation. The above theoretical equation was substantiated by the photodegradation of nifedipine, and hence is expected to apply to other photosensitive drugs.     

Analysis of the reactivity of materials having two different kinds of functional groups using the A″-McKay plot method

The hydrogen-isotope exchange reaction between HTO vapor (as a gaseous material) andp-aminophenol (or -alanine) (as a solid material) having two different kinds of functional groups, has been studied to reveal the reactivity of the compounds. The reaction has been analyzed by the A-McKay plot method and the rate constants (k) for each group have been obtained. Comparison ofk leads to the following: (1) the effect of the NH₂ group inp-aminophenol on the reactivity is greater than that in -alanine, and (2) the reactivity of compounds having two different kinds of functional groups can be analyzed by the A-McKay plot method only.     

Selective formation of AAB- and ABC-type heterotrimeric alpha-helical coiled coils

The alpha-helical coiled coils have a representative amino acid sequence of (abcdefg)(n) heptad repeats. We previously reported that two peptides named IZ-2A and IZ-2W formed an (IZ-2A)(2)/IZ-2W heterotrimer with an Ala-Ala-Trp interaction in the hydrophobic core. In this paper, we describe the selective formation of AAB- and ABC-type heterotrimers. To increase the selectivity of the AAB-type heterotrimeric formation, Lys residues at the f position were mutated to either an Ala or a Gln residue to form IZ-2A(fA) or IZ-2W(fQ). Separately, both IZ-2A(fA) and IZ-2W(fQ) have a random structure at pH 7 and 20 degrees C. However, together IZ-2A(fA) and IZ-2W(fQ) form a 2:1 complex with a thermal transition midpoint (Tm) of 48 degrees C. This procedure was applied to prepare the ABC-type heterotrimer, in which two sets of Ala-Ala-Trp interactions were designed in the hydrophobic core. Interhelical interaction between the e and g positions and the alpha-helical propensity of the amino acid at the f position were also considered in the design. The resultant three peptides selectively formed the ABC-type heterotrimer with a Tm of 51 degrees C. Other peptide combinations had random coil properties.     

囊泡表面分子间通讯交流体系的构建: 利用受体的分子识别行为调控酶的活性

在人工双层膜囊泡表面, 构建了一个通过人工受体的分子识别行为控制酶反应活性的超分子体系. 体系以生物体细胞信号转导系统为模拟原型, 由作为受体的烷基胺、被受体识别的信号分子吡哆醛衍生物、乳酸脱氢酶、受体和酶之间的媒介物Cu^2＋以及作为体系载体的合成肽脂囊泡五个成分构成．通过UV-vis光谱法及动态光散射测定对体系进行了评价, 结果表明: 随着受体疏水参数增大, 其对信号分子的识别能力增强, 二者呈良好的线性关系; 通过信号分子与囊泡表面静电相互作用的研究表明信号分子具有选择性; 媒介物与信号分子–受体可形成化学计量比为1∶2的配合物, 其形成能力比媒介物与酶的结合能力更强．作为结论, 体系中烷基胺受体对磷酸吡哆醛信号分子的识别有效控制了处于囊泡表面的乳酸脱氢酶的活性．     

Electronic and ionic transports for negative charge carriers in smectic liquid crystalline photoconductor

We have investigated negative charge carrier transport in the smectic mesophases of the 2-phenylnaphthalene derivative, 6-(4'-octylphenyl)-2-dodecyloxynaphthalene (8-PNP-O12), using the time-of-flight (TOF) method. We revealed that the negative charge carrier transport in its smectic mesophases had two different mechanisms, i.e., electronic and ionic conductions: we observed two transits of the carriers in both the smectic A (SmA) and smectic B (SmB) phases and demonstrated their origins by dilution experiments with a hydrocarbon (n-dodecane); the fast transit was attributed to the electronic transport of electrons and the slow one to the ionic transport of negative ions. Furthermore, it was clarified that the ionic transport was caused by small amounts of chemical impurities ionized by trapping photogenerated electrons in 8-PNP-O12 in addition to photoinduced autoionization of the impurities. Furthermore, we determined the trapping lifetimes for electrons to be 140 and 24 mus for the SmA and SmB phases, respectively. The experimental results suggest the coexistence of two distinctive transport channels for these charge carriers in the smectic mesophases.     

Aromaticity of planar boron clusters confirmed

Low-energy boron clusters are characterized by two-dimensional geometry. Aromaticity of these planar boron clusters was established in terms of topological resonance energy (TRE). All planar boron clusters were found to be highly aromatic with large positive TREs even if they have 4n pi-electrons. Aromaticity must therefore be the origin of unusual planar or quasi-planar geometry. Thus, the aromaticity concept is as useful in boron chemistry as it is in general organic chemistry. It is evident that the Hückel 4n + 2 rule of aromaticity should not be applied to such polycyclic pi-systems. Some of the boron clusters are in the triplet electronic state to attain higher aromaticity. Multivalency and electron deficiency of boron atoms are responsible for lowering the energies of low-lying pi molecular orbitals and then for enhancing aromaticity. For polycyclic pi-systems, paratropicity does not always indicate antiaromaticity.     

Radical addition to "cation pool". Reverse process of radical cation fragmentation

The reaction of an N-acyliminium ion with an alkyl iodide and hexabutyldistannane took place to give the alkylation product. A mechanism involving the addition of an alkyl radical to an N-acyliminium ion to produce the corresponding radical cation has been suggested.     

Specific oxidation of C-14 oxygenated 4(20),11-taxadienes by microbial transformation

Three C-14 oxygenated taxanes, 2α,5α,10β,14β-tetraacetoxytaxa-4(20),11-diene (1), 2α,5α,10β-triacetoxy-14β-(2-methylbutyryloxy)taxa-4(20),11-diene (2), and yunanaxane (3), major products of callus cultures of Taxus spp., were regio- and stereoselectively hydroxylated at the 7β position by a fungus, Absidia coerulea IFO 4011. Intriguingly, when 1 was co-administered with β-cyclodextrin and incubated with the fungus cell cultures, three other compounds 5α,9α,10β,13α-tetraacetoxytaxa-4(20),11-dien-14β-ol (7), 5α,9α,10β,13α-tetraacetoxytaxa-4(20),11-dien-1β-ol (8) and 5α,9α,10β,13α-tetraacetoxy-11(15→1) abeotaxa-4(20),11-dien-15-ol (9) were obtained.