The black hole in IC 1459 from HST observations of the ionized gas disk

The peculiar elliptical galaxy IC 1459 (M_V = -21.19, D = 16.5 Mpc) has a fast counterrotating stellar core, stellar shells and ripples, a blue nuclear point source and strong radio core emission. We present results of a detailed HST study of IC 1459, and in particular its central gas disk, aimed a constraining the central mass distribution. We obtained WFPC2 narrow-band imaging centered on the Halpha+[NII] emission lines to determine the flux distribution of the gas emission at small radii, and we obtained FOS spectra at six aperture positions along the major axis to sample the gas kinematics. We construct different dynamical models for the Halpha+[NII] and Hbeta kinematics that include a supermassive black hole, and in which the stellar mass distribution is constrained by the observed surface brightness distribution and ground-based stellar kinematics. All models are consistent with a black hole mass in the range Mbh=1-4 x 10^8 Msun, and models without a black hole are always ruled out at high confidence.Comment: 40 pages including 14 figures, Latex; submitted to A

STIS spectroscopy of the emission line gas in the nuclei of nearby FR-I galaxies

We present the results of the analysis of a set of medium resolution spectra, obtained by the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, of the emission line gas present in the nuclei of a complete sample of 21 nearby, early-type galaxies with radio jets (the UGC FR-I Sample). For each galaxy nucleus we present spectroscopic data in the region of H-alpha and the dervived kinematics. We find that in 67% of the nuclei the gas appears to be rotating and, with one exception, the cases where rotation is not seen are either face on or have complex central morphologies. We find that in 62% of the nuclei the fit to the central spectrum is improved by the inclusion of a broad component. The broad components have a mean velocity dispersion of 1349 +/- 345 km\s and are redshifted from the narrow line components (assuming an origin in H-alpha) by 486 +/- 443 km\s.Comment: 119 pages, 26 figures, ApJS Accepted, version with full figures available at http://www.astro.columbia.edu/~jake/pub/fr1datapaper.pd

Cyclic diguanylic acid behaves as a host molecule for planar intercalators

AbstractCyclic ribodiguanylic acid, c-(GpGp), is the endogenous effector regulator of cellulose synthase. Its three-dimensional structure from two different crystal forms (tetragonal and trigonal) has been determined by X-ray diffraction analysis at 1 Å resolution. In both crystal forms, two independent c-(GpGp) molecules associate with each other to form a self-intercalated dimer. A hydrated cobalt ion is found to coordinate to two N7 atoms of adjacent guanines, forcing these two guanines to destack with a large dihedral angle (32°), in the dimer of the tetragonal form. This metal coordination mechanism may be relevant to that of the anticancer drug cisplatin. Moreover, c-(GpGp) exhibits unusual spectral properties not seen in any other cyclic dinucleotide. It interacts with planar organic intercalator molecules in ways similar to double helical DNA. We propose a cage-like model consisting of a tetrameric c-(GpGp) aggregate in which a large cavity (‘host’) is generated to afford a binding site for certain planar intercalators (‘guests’)

Understanding the Nuclear Gas Dispersion in Early-Type Galaxies in the Context of Black Hole Demographics 1

The majority of nearby early-type galaxies contains detectable amounts of emissionline gas at their centers. The nuclear gas kinematics form a valuable diagnostic of the central black hole (BH) mass. Here we analyze and model HST/STIS observations of a sample of 27 galaxies; 16 Fanaroff & Riley Type I radio galaxies and 11 (more) normal early-type galaxies. We focus here on what can be learned from the nuclear velocity dispersion (line width) of the gas as a complement to the many studies dealing with gas rotation velocities. We find that the dispersion in a STIS aperture of ∼ 0.1 ′ ′ – 0.2 ′ ′ generally exceeds the large-scale stellar velocity dispersion of the galaxy. This is qualitatively consistent with the presence of central BHs, but raises the questions whether the excess gas dispersion is of gravitational or non-gravitational origin and whether the implied BH masses are consistent with our current understanding of BH demography (as predicted by the M − σ relation between BH mass and stellar velocity dispersion). To address this we construct purely gravitational axisymmetric dynamical models for the gas, both thin disk models and models with more general axis ratios an

Stereoselective Glycosylations-Additions to Oxocarbenium Ions

Tremendous progress has been made in the construction of oligosaccharides, and many impressive examples of large and complex oligosaccharide total syntheses have appeared over the years. The stability, lifetime, and reactivity of an oxocarbenium ion depend besides the nature of the counterion on the nature and orientation of the functional groups present on the carbohydrate ring. This chapter explores the role of oxocarbenium ions and contact or close ion pairs (CIPs) that features a glycosyl cation, in chemical glycosylation reactions. It deals with the stability, reactivity, and -conformational behavior of glycosyl oxocarbenium ions, and describes their intermediacy in the assembly of (complex) oligosaccharides. The chapter presents sophisticated and detailed DFT computational approaches to study glycosyl oxocarbenium ions. Where many anomeric triflates have been spectroscopically characterized, glycosyl oxocarbenium ions are too reactive to detect by straightforward NMR techniques. NMR spectroscopy has been used to characterize a multitude of covalent reactive intermediates such as anomeric triflates

The modified DNA base β-D-glucosylhydroxymethyluracil confers resistance to micrococcal nuclease and is incompletely recovered by 32P- postlabeling

The hypermodified DNA base β-D-glucosylhydroxy-methyluracil, also called J, is a naturally occurring DNA modification. J was initially detected by 32P-postlabeling in Trypanosoma brucei and was recently also found in several other eukaryotic parasites. To use 32P-postlabeling as a method to quantitate the absolute levels of J in DNA we have tested the postlabeling efficiency of J using various synthesized standard oligonucleotides containing J. It is known that modified nucleotides, especially bulky ones, are often partially recovered by postlabeling and they are poor substrates for some of the enzymes used. We found that on average only 50% of J is recovered, which shows that the amount of J in T. brucei DNA has been twofold underestimated. Experiments with a short oligomer and defined pyrimidine tracts showed that the incomplete recovery of J is caused at least in part by resistance of J-containing DNA to degradation by micrococcal nuclease

Fluorescent small-molecule agonists as follicle-stimulating hormone receptor imaging tools

Fluorescent cell surface receptor agonists allow visualization of processes that are set in motion by receptor activation. This study describes the synthesis of two fluorescent, low molecular weight ligands for the follicle-stimulating hormone receptor (FSHR), based on a dihydropyridine (DHP) agonist. We show that both BODIPY- and Cy5-conjugated DHP (m-DHP-BDP and m-DHP-Cy5) are potent FSHR agonists, able to activate receptor signalling with nanomolar potencies and to effect receptor internalisation at higher concentrations. FSHR-dependent uptake of m-DHP-Cy5 is in stark contrast to the cellular uptake of m-DHP-BDP which was efficiently internalised also in the absence of FSHR. Our results comprise a first-in-class fluorescent low molecular weight ligand for in situ FSHR imaging and pertain the potential means for targeted delivery of drugs into the endolysosomal pathway of FSHR-expressing cells