Colleen Kelley

A selection system for identifying accessible sites in target RNAs.

Although ribozymes offer tremendous potential for posttranscriptionally controlling expression of targeted genes, their utility is often limited by the accessibility of the targeted regions within the RNA transcripts. Here we describe a method that identifies RNA regions that are accessible to oligonucleotides. Based on this selection protocol, we show that construction of hammerhead ribozymes targeted to the identified regions results in catalytic activities that are consistently and substantially greater than those of ribozymes designed on the basis of computer modeling. Identification of accessible sites should also be widely applicable to design of antisense oligonucleotides and DNAzymes.

Nucleophilic addition of chromium carbene anions to the coordinated olefin in [Cp(CO)2Fe(η2-olefin)]+ complexes and to the cyclohexadienyl ligand in [(η5-cyclohexadienyl)(CO)3Fe]+

Abstract The chromium carbene anion [(CO)5Cr  C(OMe)CH2]− (2) has been found to add to the coordinated olefin in the complexes [(Cp(CO)2Fe(η2-olefin)]+ (olefin  cis-2-butene, trans-2-butene, styrene) to form bimetallic chromium-iron complexes of the form (CO)5Cr  C(OMe)CH2  CHRCHR′Fe(CO)2Cp. Complex 2 also adds to the cyclohexadienyl ligand in [(η5-cyclohexadienyl)Fe(CO)3]+ to form a crystallographically characterized bimetallic complex which has a Fe(CO)3 unit coordinated to a [(CO)5Cr  C(OMe)CH2]− substituted cyclohexadiene ligand. A trimetallic Fe2Cr complex with two (η4-cyclohexadiene)Fe(CO)3 groups attached to the β-carbon of the earbene ligand of the (CO)5Cr  C(OMe)CH moiety has also been prepared, and two of the three possible stereoisomers of this complex have been crystallographically characterized.

The 1984 Campaign Rhetoric of Representative George Hansen: A Pentadic Analysis.

This essay employs Kenneth Burkes pentad to examine rhetorical choices made by former U.S. Congressman George Hansen of Idaho as he dramatized two situations: his felony conviction in April of 1984 and his subsequent reelection bid. Hansens rhetoric was designed to eliminate any personal responsibility for his conviction and to encourage voters to support his reelection on the basis of his past record as a defender of their rights and as their protector from harassment by the federal government. The essay concludes speculatively, suggesting that although Hansen did not win the November, 1984 election, his rhetoric was largely effective because it resulted in substantial identification with the voters of Idahos Second Congressional District.

The Public Rhetoric of Mikhail Gorbachev and the Promise of Peace.

This essay examines some of the rhetorical choices of General Secretary Mikhail Gorbachev which dramatize Soviet calls for nuclear weapons de‐escalation. Two Burkean dramas are identified. In the first, nuclear weapons must be disarmed so that the world may survive, and in the second, nuclear technology is presented as a roadblock to socialism. Another version of the second drama envisions imminent Soviet economic collapse due to the expense of the arms race. The essay concludes by speculating that Gorbachevs peace efforts are sincere, because they are motivated by twin crises of a failing economy and a threatened world community.

Republican campaign rhetoric: Reflections of a meaner, tougher America

This article examines some Republican communication behaviors that account, in part, for accusations that the use of negative strategies was unprecedented during the 1988 presidential campaign. It also explores some of the effects of those strategies on political communication behavior during the first year of the Bush administration. It is suggested that a kind of systemic demagoguery may have produced Campaign ‘88 and its legacy. Parts of that system include the process, the polls, the packagers, the press, and the public. The paper concludes with some suggestions for modifying the campaign system to discourage demagogic communication.

PREPARATION AND REACTIVITY OF CYCLOPENTADIENYL-DICARBONYLIRON-SILYL COMPLEXES

A series of compounds of the type FpSi(X)R2, [Fp = (r|-C5H5)Fe(CO)2], where R = Me, Ph; and X = H, OMe, OEt, Br, CI, and F have been prepared. Reaction of Fp anion with the readily available chlorosilanes, CI(H)SiMe2 and CI(H)SiPh2, yields compounds FpSiMe2(H) and FpSiPh2(H) respectively. Reactions of these two compounds with carbon tetrachloride, carbon tetrabromide, alcohols, and tetrafluoroborate salts lead to substitution at silicon. Introduction: There has been interest in transition metal silyl compounds recently due to reports of silylene, silaethylene, and disilene complexes and the intermediacy of these compounds in catalytic reactions. Transition metal silane complexes are usually synthesized by either salt elimination, mercurial routes, elimination of a covalent molecule, oxidative addition/ reductive elimination and more recently by silylene insertion. Many of these approaches eliminate the reactive site on silicon and are limited by the availability of starting silanes. We have prepared Fe-Si complexes that retain a reactive site. A comparison of the similarities and differences between the methylsilyl and phenylsilyl derivatives is given. Materials and Methods: All synthetic manipulations were performed under a nitrogen atmosphere by using standard Schlenk techniques for handling moderately air-sensitive compounds . Solvents were distilled from either sodium benzophenone (THF, diethyl ether, hexane) or lithium aluminum hydride (CH2CI2). Infrared spectra were recorded on a Nicolet 5DX spectrophotometer. H NMR spectra were recorded either on a Bruker WP-80 MHz or a Hitachi Perkin Elmer R-24A 60 MHz spectrometer. Chemical shifts were reported downfield from internal tetramethylsilane. Mass spectra were obtained using either a Finnigan MAT 4600 mass spectrometer or a HP gas chromatograph/mass spectrometer operating at 70 eV (for electron impact) or using methane as the reagent gas (chemical ionization). Elemental analyses were performed by either Galbraith Laboratories or Desert Analytics. Silanes were purchased from Petrarch (Huls) Chemical and used as received. An authentic sample of triphenylmethane was purchased from Aldrich. An authentic sample of FpBr was prepared by literature methods. All other reagents were bought from standard commercial sources (Aldrich, VWR) and were used as received. Preparation of FpSi(H)Me2 (1a). Dimethylchlorosilane (8.58 g, 91 mmol) was added via syringe to a solution of the sodium salt NaFe(CO) 2C5H5 (from cyclopentadienylirondicarbonyl dimer, 10.05 g, 28 mmol, and sodium amalgam, 1.6 g of sodium, 15.0 mL of mercury) in tetrahydrofuran (200 mL). The mixture was allowed to stir at room temperature for 12 h. The solvent was then removed in vacuo and the redbrown residue was extracted with ether (100 mL) and filtered through celite and sand. Ether was removed by rotary evaporation. Vacuum distillation (65°C/0.5 mm Hg) gave 8.31 g of a red oil (63%). Compound 1a was characterized by comparison of its H NMR and IR spectra with literature values, in addition to its mass spectral data (see Table I). Preparation of FpSi(H)Ph2 (1b). Diphenylchlorosilane (14.88 g, 68 mmol) was added via syringe to a solution of the sodium salt NaFe(CO) 2C5H5 (from cyclopentadienylirondicarbonyl dimer, 12.0 g, 34 mmol, and sodium amalgam, 1.6 g sodium, 15.0 mL of mercury) 6 a in tetrahydrofuran (100 mL). The mixture was allowed to stir at room temperature for 12 h. The solvent was then removed in vacuo and the red-

New Addition and Cycloaddition Reactions of the Cationic Carbyne Complexes [Cp(CO)(L)M≡CR]+ (M = Mn, Re; L = CO, PPh3; R = Me, Tolyl)

The electrophilic carbyne complex [Cp(CO)2≡Re≡CTol]+ reacts with azoarenes, epoxides, aziridines, and propylene sulfide to give a variety of new metallacycles and carbene complexes. Vinyl-substituted carbyne complexes of the form [Cp(CO)LMn≡C-CR=CR2]+ (L = CO, PPh3) have been prepared by three different routes, and they react with nucleophiles to give carbene and vinylidene derivatives, depending upon the size of the nucleophile. The ethylidyne complexes [Cp(CO)2M≡CCH3]+ (M = Mn, Re) can be deprotonated to yield the new vinylidene complexes Cp(CO)2M=C=CH2, and these complexes react with imines and benzalazine to give new metallacycles and with ButN=C=NBut to induce metathesis of the vinylidene C=C bond to form complexes possessing ButN≡C isocyanide ligands.