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Singlet and triplet energy transfers in tetra-(meso-truxene)zinc(II)- and tetra-(meso-tritruxene)zinc(II) porphyrin and porphyrin-free base dendrimer…
2011
The synthesis, optical properties, and energy transfer features of four dendrimers composed of meso-tetrasubstituted zinc(II) porphyrin (ZnP) or a free base (P) central core, where the substituents are four truxene (Tru) or four tritruxene dendrons (TriTru), TruP, TriTruP, TruZnP, and TriTruZnP, are reported. Selective excitation of the truxene donors results in a photoinduced singlet energy transfer from the truxenes to the porphyrin acceptor. The rates for singlet energy transfer (k(ET)), evaluated from the change in the fluorescence lifetime of the donors (Tru and TriTru) in the presence and absence of the acceptor (P or ZnP) for TruP, TruZnP, TriTruP, and TriTruZnP, are 5.9, 1.2, 0.87, …
Selective derivatisation of resorcarenes: 1. The regioselective formation of tetra-benzoxazine derivatives
1997
Abstract Four 5,6-benzo-1,3-oxazine rings are formed by the condensation of resorcarenes with various aliphatic or aromatic primary amines and formaldehyde. From four possible regioisomers only the C4 symmetrical compound is isolated in yields of up to 90%. Semiempirical calculations confirm its relative stability, which is due to the possible formation of four intramolecular OH…O hydrogen bonds. The regioselectivity of the reaction is further established for two examples by single crystal X-ray analysis. A solvent molecule is included in the extended cavity.
Transmission Electron Microscopy of GroEL, GroES, and the Symmetrical GroEL/ES Complex
1994
Two new 2-D crystal forms of the Escherichia coli chaperone GroEL (cpn60) 2 x 7-mer have been produced using the negative staining-carbon film (NS-CF) technique. These 2-D crystals, which contain the cylindrical GroEL in side-on and end-on orientations, both possess p21 symmetry, with two molecules in the respective unit cells. The crystallographically averaged images correlate well with those obtained by other authors from single particle analysis of GroEL and our own previous crystallographic analysis. 2-D crystallization of the smaller chaperone GroES (cpn10) 7-mer has also been achieved using the NS-CF technique. Crystallographically averaged images of GroES single particle images indic…
Three New Medicagenic Acid Saponins from Polygala micranthaGuill. & Perr.
2011
Three new medicagenic acid saponins, micranthosides A–C (1–3), were isolated from the roots of Polygala micranthaGuill. & Perr., along with six known presenegenin saponins. Their structures were elucidated on the basis of extensive 1D- and 2D-NMR experiments (1H, 13C, DEPT, COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as 3-O-β-D-glucopyranosylmedicagenic acid 28-[O-β-D-galactopyranosyl-(14)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-β-D-fucopyranosyl] ester (1), 3-O-β-D-glucopyranosylmedicagenic acid 28-[O-6-O-acetyl-β-D-galactopyranosyl-(14)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-β-D-fucopyranosyl] ester (2), and 3-O-{O-β-D-glucopyranosyl-(13)-O-[β-D-gluc…
Structure of keyhole limpet hemocyanin type 1 (KLH1) at 15 Å resolution by electron cryomicroscopy and angular reconstitution † 1 †This article is de…
1997
Abstract A three-dimensional reconstruction of keyhole limpet hemocyanin type 1 (KLH1) has been obtained using electron cryomicroscopy at liquid helium temperatures and single particle image processing. The use of a high-contrast embedding medium, 1% (w/v) glucose and 2% (w/v) ammonium molybdate (pH 7.0), enables high-resolution electron micrographs to be recorded close to focus, i.e. with excellent transfer of high-resolution information, while maintaining enough image contrast to localise the individual macromolecules in the images. When low-pass filtered to ∼45 A resolution, the new 15 A resolution reconstruction is very similar to the earlier reconstructions of gastropodan hemocyanins o…
[33] Use of repair endonucleases to assess DNA damage by peroxynitrite
1999
Publisher Summary This chapter discusses the use of repair endonucleases to assess DNA damage by peroxynitrite. Repair endonucleases allow a convenient quantification of various types of oxidative modifications induced by peroxynitrite, both in cultured cells and in cell-free DNA. The high sensitivity of the assays allows highly ectotoxic exposure conditions to be avoided—as well as the generation of secondary DNA modifications—that often become a problem at high levels of damage because primary DNA oxidation products can be orders of magnitude more reactive than the original bases, as demonstrated for the reaction of 8-hydroxyguanine with singlet oxygen. The ratio of the various types of m…
<p><strong>Towards resolving a problem of the identity of the <em>Aethus</em> species (Hemiptera: Heteroptera: Cydnidae) occu…
2014
The genus Aethus in Cambodia is known only from a single species collected in the 1950s that was originally identified as A. indicus. However, what was regarded as A. indicus in the Oriental and Australian regions appeared to consist of three sibling species, recognizable only on the basis of male genital structures, i.e., A. philippinensis, A. pseudindicus, and true A. indicus. To date, the lack of males representing this genus from Cambodia made it impossible to verify which species actually occur in this country. The present study, based on eight males collected at the same locality in Cambodia where the specimens were originally identified as A. indicus more than 50 years ago (i.e., Sie…
Labeling of Single Cells in the Central Nervous System of <em>Drosophila melanogaster</em>
2013
In this article we describe how to individually label neurons in the embryonic CNS of Drosophila melanogaster by juxtacellular injection of the lipophilic fluorescent membrane marker DiI. This method allows the visualization of neuronal cell morphology in great detail. It is possible to label any cell in the CNS: cell bodies of target neurons are visualized under DIC optics or by expression of a fluorescent genetic marker such as GFP. After labeling, the DiI can be transformed into a permanent brown stain by photoconversion to allow visualization of cell morphology with transmitted light and DIC optics. Alternatively, the DiI-labeled cells can be observed directly with confocal microscopy, …
Globularia nudicaulis, a new host of Cucumber mosaic virus
2006
) is a perennial, foundnaturally on European mountains at altitudes between 900 and 2000 m.In June 2004, G. nudicaulis plants, with a yellow mosaic and/or variega-tion on malformed leaves, were noted among plant species cultivated in theBotanical Garden at Bologna University, Italy. No elongated virus-likeparticles were observed in affected-leaf extracts by transmission electronmicroscopy using a leaf dip method. By applying a protein A sandwichenzyme-linked immunosorbent assay (PAS-ELISA) technique ( Edwards Csystemic symptoms were observed in Nicotiana tabacum , N. benthamiana ,N. glutinosa, N. clevelandii and Capsicum annuum, and Cucumis sativusand C. melo. Reverse transcription-polymera…
Semisynthetic roxburghin tetramethyl ether
2008
The title molecule, (E)-2,3′,4,5-tetramethoxystilbene, C18H20O4, is virtually planar. The angle between the two benzene rings is 4.06 (6)°. The intermolecular interactions present in the structure are weak. There are C—H...O hydrogen bonds and C—H...π-electron ring interactions. The molecules are ordered into planes that are parallel to (overline{1}01). The distance between adjacent planes is about 3.3 Å and therefore π–π electron interactions between the aromatic planes are also plausible.