DABCO-triggered mild cascade reaction of electron-deficient cyclopentadienone: facile and efficient synthesis of condensed carbocycles

2,5-Bis(methoxycarbonyl)-3,4-diphenylcyclopentadienone (1) reacts with 4-phenylbut-3-yn-2-one (2b) in the presence of DABCO to give the bicyclic carbocycles (6b) and the tetracyclic carbocycle (7b) under extremely mild reaction conditions.     

Relaxation in systems with hierarchical organization: Analytical derivation of the relaxation and dispersion functions

We report a successful attempt to derive a closed-form expression for the relaxation function of a complex system by solving a set of coupled kinetic equations connecting the excitation/de-excitation rates to the number of particles (such as electrical charges, dipoles, etc.) in excited states. Our approach, originating from developments in dielectric and mechanical relaxation studies, allows the use of a unified treatment for a wide array of natural processes which often pose challenges to theoretical modeling. We use the notions that (i) a dipole represents any pair formed by a particle in an excited state (such as an energy level in optically excited molecules, or an electrode in dielectric spectroscopy) and its image in the ground state (or reference electrode), that (ii) coupling between such dipoles may be described as particle transfer from one excited state to another with lower energy, and that (iii) the relaxation function for such a system of dipoles is mathematically equivalent to the cumulative distribution function of particles, i.e., the total number of particles that are still in an excited state at a time t following excitation. Taken together, these ideas naturally lead to the identification of two types of relaxation – parallel and serial relaxation – and allow one to tackle systems with either geometrical or physical self-similarity within a unified mathematical scheme.     

A method for approximations to the pdf'S and cdf'S of GLSE's and its application to the seemingly unrelated regression model

This paper first develops a valid method for approximations to the pdf's and cdf's of GLSE in linear models and, applying this method to the Zellner estimator with an unrestricted sample covariance in the seemingly unrelated regression model, obtains an approximate pdf with a bound of ordern ⁻² and an approximate covariance matrix with a bound of ordern ⁻³ This research was done at the London School of Economics while the authors were British Council scholars. Kariya is grateful to Professor J. Durbin for a general discussion on asymptotic expansions. Further the authors deeply appreciate Professor Y. Kataoka and anonymous referee for their invaluable comments and suggestions.     

Transformations preserving normality and Wishart-ness

Let R^n×p, (n), Gl(p) and ₊(p) denote respectively the set of n×p matrices, the set of n×n orthogonal matrices, the set of p×p nonsingular matrices and the set of p × p positive definite matrices. In this paper, it is first shown that a bijective and bimeasurable transformation (BBT) g on R^p≡R^p×1 preserving the multivariate normality of N_p(μ, Σ) for fixed μ=μ₁, μ₂ (μ₁≠μ₂) and for all Σ ₊(p) is of the form g(x)=Ax+b a.e. for some (A, b)Gl(p)×R^p. Second, a BBT g on R^n×p preserving the form for certain 's and all Σ ₊(p) is shown to be of the form g(x)=QxA+E a.e. for some (Q, A, E) (n)×Gl(p)×R^n×p. Third, a BBT h on ₊(p) preserving the Wishart-ness of W_p(Σ, m) (m≥p) for all Σ ₊(p) is shown to be of the form h(w)=A′wA a.e. for some AGl(p). Fourth, a BBT k(x, w)=(k₁(x, w), k₂(x, w)) on R^n×p× ₊(p) which preserves the form of for certain 's and all Σ ₊(p) is shown to be of the form k(x, w)=(QxA+E, A′wA) a.e. for some (Q, A, E) (n)×Gl(p)×R^n×p.     

ON THE TWO FORMS OF INTERMEDIATE M OF BACTERIORHODOPSIN

Abstract— The decay time course of intermediate M of bacteriorhodopsin was investigated by flash spectrophotometry. The decay was composed of two exponentials showing the existence of two forms of intermediate absorbing around 410 nm. The two were very different in kinetic character whereas the absorption spectra were almost the same. The relative yield of the two components was a function of the intensity of the exciting flash and the slower component disappeared when the flash intensity was made very small. A model based on the trimeric cluster structure of bacteriorhodopsin is proposed.     

Chitin- and Streptavidin-Mediated Affinity Purification Systems: A Screening Platform for Enzyme Discovery

Affinity purification of recombinant proteins is an essential technique in biotechnology. However, current affinity purification methods are very cost-intensive, and this imposes limits on versatile use of affinity purification for obtaining purified proteins for a variety of applications. To overcome this problem, we developed a new affinity purification system which we call CSAP (chitin- and streptavidin-mediated affinity purification) for low-cost purification of Strep-tag II fusion proteins. The CSAP system is designed to utilize commercially available chitin powder as a chromatography matrix, thereby significantly improving the cost-efficiency of protein affinity purification. We investigated the CSAP system for protein screening in 96-well format as a demonstration. Through the screening of 96 types of purified hemoproteins, several proteins capable of the catalytic diastereodivergent synthesis of cyclopropanes were identified as candidates for an abiotic carbene transfer reaction.     

Reaction mechanism of direct episulfidation of caryophyllene and humulene

Direct episulfidations of caryophyllene or humulene with elemental sulfur were examined by means of gas chromatography. Caryophyllene-6,7-episulfide was formed at an early stage in a reaction of the caryophyllene and elemental sulfur at 120 degrees C. Caryophyllene-3,6-sulfide and polymer compounds were formed after the episulfidation. Formations of the these compounds were related to the disappearance of the caryophyllene-6,7-episulfide. Isomerization from the caryophyllene to isocaryophyllene was also observed during the reaction. In the reaction of humulene with elemental sulfur, humulene-6,7-episulfide was initially produced and then converted to humulene-9,10-episulfide. It was assumed that the polymer compound in the reaction of humulene with sulfur was related to the disappearance of the both humulene episulfides.     

Determination of aluminum in large volume parenteral drug products used in total parenteral nutrition therapy by ICP-MS with a dynamic reaction cell

The proposed method was developed for the determination of aluminum (Al) in large volume parenteral (LVP) drug products used in total parenteral nutrition (TPN) therapy. The determination of Al in LVP drug products was performed by an inductively coupled plasma mass spectrometer equipped with a dynamic reaction cell (DRC-ICP-MS). DRC-ICP-MS conditions for the analysis of Al were studied to obtain the best signal to background (S/N) ratios. The interfering polyatomic ions at mass 27 (Al) were reduced by using NH(3) as a reaction gas. The detection limit of Al in a 1% (v/v) HNO(3) aqueous solution was 2 ng/l. The Al contents in LVP drug products obtained by this method were in the range of 1.16-4.33 microg/l and were less than 25 microg/l, that is, the regulation value of Food and Drug Administration (FDA). In order to trace the origin of Al in LVP drug products, each part of the LVP drug product, which is composed of three chambers, was investigated. However, a clear difference of the Al contents in each chamber was not observed. Furthermore, the Al contents in injection bags were quantified. Although the Al contents in injection bags were relatively high (in the range of 27.5-33.6 microg/g), dissolution of Al from the injection bags was not observed in the stability testing. From all of these results, it was concluded that the Al contents in the LVP drug products investigated originated in the amount of the Al in each raw material.     

In situ observation of thermal relaxation of interstitial-vacancy pair defects in a graphite gap

Direct observation of individual defects during formation and annihilation in the interlayer gap of double-wall carbon nanotubes (DWNT) is demonstrated by high-resolution transmission electron microscopy. The interlayer defects that bridge two adjacent graphen layers in DWNT are stable for a macroscopic time at the temperature below 450 K. These defects are assigned to a cluster of one or two interstitial-vacancy pairs (I-V pairs) and often disappear just after their formation at higher temperatures due to an instantaneous recombination of the interstitial atom with vacancy. Systematic observations performed at the elevated temperatures find a threshold for the defect annihilation at 450-500 K, which, indeed, corresponds to the known temperature for the Wigner energy release.     

A condition for null robustness

Sufficient conditions are given that certain statistics have a common distribution under a wide class of underlying distributions. Invariance methods are the primary technical tool in establishing the theoretical results. These results are applied to MANOVA problems, problems involving canonical correlations, and certain statistics associated with the complex normal distribution.