Reversible Fixation of Ethylene on a SmII Calix-Pyrrole Complex

Reversible ethylene fixation in lanthanide chemistry is demonstrated by the Sm^II derivatives [R₈-calix-pyrrole)(Et₂O)Sm{Li(thf)₂}{Li(μ₃-OCH=CH₂)}] (R=Et, {−(CH₂)₅−}_0.5), which react with ethylene to afford the corresponding dinuclear complexes (see picture).     

Role of polyethyleneimine in the purification of recombinant human tumour necrosis factor beta

The chromatographic behaviour of recombinant human tumour necrosis factor beta (rhTNF-β) (pI9.0) during cation-exchange chromatography at pH 7.5 is investigated. Without prior treatment of the Escherichia coli cell extract with polyethyleneimine (PEI), very little rhTNF-β was bound to the column. However, upon addition of 5% PEI (100 μl ml⁻¹) to the cell lysate, rhTNF-β was shown to bind to cation-exchange columns normally. TNF-β was readily precipitated from the clarified cell extract by 20% ammonium sulphate, but only ca. 25% of this precipitate could be re-solubilized for further purification. However, when 5% PEI was included in the solubilization buffer, the balance of the rhTNF-β could be recovered. It is proposed that charge interaction between rhTNF-β and nucleic acids in the cell extract is responsible for both of these anomalous phenomena, and that PEI (a cationic polyelectrolyte) was able to disrupt this interaction by displacing rhTNF-β from the charge complex.     

Synthesis and Photophysics of Core‐Substituted Naphthalene Diimides: Fluorophores for Single Molecule Applications

The synthesis and photophysics of two new aminopropenyl naphthalene diimide (SANDI) dyes are reported. A general and convenient method for the synthesis of the precursor mono‐, di‐, and tetrabrominated 1,4,5,8‐naphthalene tetracarboxylic dianhydrides is described. The two core‐substituted SANDIs exhibit many of the photophysical properties required for fluorescence labeling applications including high photostability and high fluorescence quantum yields (>0.5) in the visible region of the spectrum. The emission wavelength is sensitive to the number of substituents on the NDI core, and the fluorescence decay times are in the range of ～8–12 ns for both compounds in the solvents investigated. Preliminary fluorescence emission data from single molecules of the compounds embedded in poly(methyl methacrylate) films are also reported and show that single molecules have very low yields of photobleaching, particularly the di‐substituted system. Furthermore, only a small proportion (<10 %) of the single molecules studied display fluorescence intermittencies or “blinks” in their photon trajectory. The compounds appear to be excellent candidates for applications at the single molecule level, for example, as FRET labels.     

Pharmaceutical metabolite profiling using quadrupole/ion mobility spectrometry/time‐of‐flight mass spectrometry

The use of hybrid quadrupole ion mobility spectrometry time‐of‐flight mass spectrometry (Q/IMS/TOFMS) in the metabolite profiling of leflunomide (LEF) and acetaminophen (APAP) is presented. The IMS drift times (T_d) of the drugs and their metabolites were determined in the IMS/TOFMS experiments and correlated with their exact monoisotopic masses and other in silico generated structural properties, such as connolly molecular area (CMA), connolly solvent‐excluded volume (CSEV), principal moments of inertia along the X, Y and Z Cartesian coordinates (MI‐X, MI‐Y and MI‐Z), inverse mobility and collision cross‐section (CCS). The correlation of T_d with these parameters is presented and discussed. IMS/TOF tandem mass spectrometry experiments (MS² and MS³) were successfully performed on the N‐acetyl‐p‐benzoquinoneimine glutathione (NAPQI‐GSH) adduct derived from the in vitro microsomal metabolism of APAP. As comparison, similar experiments were also performed using hybrid triple quadrupole linear ion trap mass spectrometry (QTRAPMS) and quadrupole time‐of‐flight mass spectrometry (QTOFMS). The abilities to resolve the product ions of the metabolite within the drift tube and fragment the ion mobility resolved product ions in the transfer travelling wave‐enabled stacked ring ion guide (TWIG) demonstrated the potential applicability of the Q/IMS/TOFMS technique in pharmaceutical metabolite profiling. Copyright © 2009 John Wiley & Sons, Ltd.     

Alleviation of photoinduced damage in GdxY1-xCa4O(BO3)3 at elevated crystal temperature for noncritically phase-matched 355-nm generation

We developed a Gd(x)Y(1-x)Ca(4)O(BO(3))(3) (GdYCOB) crystal for control of optical birefringence. GdYCOB crystals were successfully used to generate noncritical phase-matched (NCPM) second and third harmonics of 1064-nm lights. However, we observed degradation of third-harmonic-generation (THG) output power and distortion of the beam pattern as a result of photoinduced damage and thermal dephasing. The photoinduced damage was classified into two types. One was gray-track and the other was photorefractive damage. It seems that these types of damage were similar to the types of damage that occurred with KTiOPO(4) and LiNbO(3) crystals. We tried to circumvent this problem by crystal heating. Photoinduced damage of GdYCOB was overcome by elevation of the crystal temperature, and NCPM THG (355-nm) output power from heated GdYCOB increased to 9 mW (62.5 kHz).     

AnO(n logn) algorithm for the voronoi diagram of a set of simple curve segments

LetX be a given set ofn circular and straight line segments in the plane where two segments may interest only at their endpoints. We introduce a new technique that computes the Voronoi diagram ofX inO(n logn) time. This result improves on several previous algorithms for special cases of the problem. The new algorithm is relatively simple, an important factor for the numerous practical applications of the Voronoi diagram.This work was supported by NSF Grants No. DCR-84-01898 and No. DCR-84-01633.     

Maximal sum-free sets in finite Abelian groups,III

The main result of this paper is the complete characterization of maximal sum-free sets in Abelian groups of order 3^mn(m ≥ 1) where every prime divisor p of n (if n > 1) is congruent to 1 modulo 3. A few previous results of the author on addition theorems of group theory are also sharpened and/or improved.     

Cobalt tris(mercaptoimidazolyl)borate complexes: synthetic studies and the structure of the first cobaltaboratrane

The paramagnetic complexes (TmtBu)CoX (X = Cl, Br, I) have been readily prepared and structurally characterized and provide a convenient entry into cobalt(II) tris(mercaptoimidazolyl)borate chemistry. A number of derivatives, including mononuclear triphenylphosphine adducts [(TmtBu)Co(PPh3)]X and dinuclear compounds [Co2(TmtBu)2X]Y, have been prepared in order to ascertain whether cobalt is a reliable surrogate for zinc in biological systems, particularly in sulfur-rich coordination environments. The structure of the first cobaltaboratrane is also reported.     

Wavelet Foveation

A foveated image is a nonuniform resolution image whose resolution is highest at a point (fovea) but falls off away from the fovea. It can be obtained from a uniform image through a space-variant smoothing process, where the width of the smoothing function is small near the fovea and gradually expanding as the distance from the fovea increases. We treat this process as an integral operator and analyze its kernel. This kernel is dominated by its diagonal in the wavelet bases and thus permits a fast algorithm for foveating images. In addition, the transformed kernel takes a simple form which can be easily computed using a look-up table. This is useful, since in applications the fovea changes rapidly. We describe an application of our approximation algorithm in image visualization over the Internet.