General deoxyribozyme-catalyzed synthesis of native 3'-5' RNA linkages

An elusive goal for nucleic acid enzymology has been deoxyribozymes that ligate RNA rapidly, sequence-generally, with formation of native 3'-5' linkages, and in preparatively useful yield. Using in vitro selection, we have identified Mg2+- and Zn2+-dependent deoxyribozymes that simultaneously fulfill all four of these criteria. The new deoxyribozymes operate under practical incubation conditions and have modest RNA substrate sequence requirements, specifically D downward arrowRA for 9DB1 and A downward arrowR for 7DE5 (D = A, G, or U; R = A or G). These requirements are comparable to those of deoxyribozymes such as 10-23 and 8-17, which are already widely used as biochemical tools for RNA cleavage. We anticipate that the 9DB1 and 7DE5 deoxyribozymes will find immediate practical application for RNA ligation.     

In situ Raman studies on lithiated single-wall carbon nanotubes in liquid ammonia

The charge transfer induced lithiation of single-wall carbon nanotubes (SWNTs) was investigated by in situ monitoring by Raman spectroscopy as lithium was added incrementally to a dispersion of SWNTs in liquid ammonia. Charge transfer from liquid ammonia solvated lithium to the SWNTs led to intercalation of lithium into the SWNT ropes, as well as to the semi-covalent lithiation of the SWNTs. Raman spectra of the SWNTs recorded as lithium was added showed a 30 wavenumber downshift of the G band (1594 cm⁻¹) with the concomitant appearance of a new peak at 1350 cm⁻¹ that was assigned as the signature of the lithiated SWNTs. Addition of 1-iodododecane to the lithiated SWNTs resulted in the covalent attachment of dodecyl groups. The intercalation of lithium throughout the SWNT ropes led to complete dodecylation of all individual SWNTs.     

Alkaline hydrolysis of 2-(trifluoromethyl)imidazo[4,5-f] and -[4,5-h]quinolines

2-(Trifluoromethyl)imidazo[4,5-$\text{f}$] and -[4,5-$\text{h}$]quinoline have been prepared from 5(6),acetamido-2-(trifluoromethyl)benzimidazole and 7,8-diaminoquinoline respectively. These (trifluoromethyl)- quinolines like 2-(trifluoromethyl)imidazoles but unlike 2-(trifluoromethyl) benzimidazoles, undergo hydrolysis in dilute sodium hydroxide to give ultimately the corresponding imidazo[4,5-$\text{f}$] and -[4,5-$\text{h}$]- quinoline, respectively.     

Synthesis of crystalline skutterudite superlattices using the modulated elemental reactant method

A series of samples ((AB)(x)(CD)(y))(z) were prepared containing both short repeat units (AB and CD) and long repeat units ((AB)(x)(CD)(y)), where the short repeat units were designed to have the composition appropriate to form square M(4)Sb(12) skutterudites (M = Fe, Co, or Ir; square = vacancy, La, or Y). X-ray diffraction and reflectivity were used to follow the evolution of the films from amorphous, layered materials to crystalline skutterudite superlattices as a function of annealing temperature and time. In all cases, the short repeat units interdiffused and crystallized the expected skutterudite, while the long repeat period persisted after annealing. The skutterudites crystallize with random crystallographic orientation with respect to the substrate. The observed splitting of the peaks in the high-angle diffraction data from the IrSb(3)/CoSb(3) sample indicates the formation of a novel superlattice structure with each grain having a random crystallographic orientation of the skutterudite lattice with respect to the superlattice direction.     

Regioselective synthesis of 3,3‐diethyl‐4‐(methylene)‐1‐quinol‐2‐ones by an intramolecular microwave assisted heck reaction

A protocol for the intramolecular Heck cyclization to afford 3,3‐diethyl‐4‐(methylene)‐1‐quinol‐2‐ones is described. We observed that the use of microwave irradiation increased the efficiency of the reaction. Several examples are presented which show the versatility of the reaction.     

Thermionic emission from giant fullerenes

The kinetics of cluster formation in supersonic jets is examined by numerical integration of the master equation system. Some general characteristics of cluster kinetics could be formulated. Excellent agreement between experimental curves of p-cresol (H₂O)_{0, 1, 2, 3} formation as function of H₂O pressure and the corresponding calculated curves were obtained assuming successive cluster formation. From the kinetic curves, an unambiguous assignment of cluster size was possible which agreed with mass-resolved REMPI measurements. The fit of the rate coefficients shows the formation of p-cresol (H₂O)₁ to be faster than p-cresol (H₂O)₂ and p-cresol (H₂O)₃.     

Prediction of standard interfacial electron-transfer rate constants for the Ru(NH3)6(3+/2+) couple through omega-hydroxyalkanethiol self-assembled monolayers on gold electrodes

Two relatively simple approaches are developed and used to calculate (predict) the standard interfacial electron-transfer (ET) rate constants (k degrees) of the Ru(NH3)6(3+/2+) couple dissolved in aqueous electrolyte solutions in contact with Au electrodes coated with self-assembled monolayers (SAMs) composed of HS(CH2)nOH as functions of both n and temperature. These approaches are suggested by the conclusion reached by Smalley et al. (J. Electroanal. Chem. 2006, 589, 1-6) that the interfacial ET rate of a solution-dissolved redox couple in contact with a SAM is, within 1 order of magnitude, the same as the (normalized) interfacial ET rate of a similar attached (as a constituent of a similar SAM) couple. The calculations, therefore, employ the measured electronic coupling of the attached (to Au electrodes through alkanethiolate bridges) -PyRu(NH3)5(3+/2+) couple. The two approaches also both include dynamic solvent effects on the ET kinetics and the influence of electronic coupling on the activation barrier for the ET reaction. At T=298 K and n=3, 11, and 14, the predicted rate constants are in very good agreement with the existing measurements of k degrees. However, for n<3 at 298 K, the predicted rate constants are extremely large (i.e., >4.5 cm s(-1)) and do not tend toward a limiting value. Additionally, even if the electronic coupling between a Au electrode and a Ru(NH3)6(3+/2+) moiety located at the surface of the SAM is >0.1 eV, the calculated standard rate constant is not directly proportional to the inverse of the longitudinal dielectric time of the solvent. A primary reason for both the absence of a limiting value for the predicted k degrees's at 298 K and the attenuated influence of dynamic solvent effects is the activation energy barrier suppression caused by large values of the electronic coupling.     

Three-dimensional blow-up solutions of the Navier-Stokes equations

In this paper we extend the plane blow-up results of Grundy& McLaughlin (1997) to the three-dimensional Navier-Stokes equations.Using a solution structure originally due to Lin we first providenumerical evidence for the existence of blow-up solutions on- < x, z < , 0 y 1 with boundary conditions on y = 0and y = 1 involving derivatives of the velocity components.The formulation enables us to consider plane and radial flowas special cases. Various features of the computations are isolatedand are used to construct a formal asymptotic solution closeto blow-up. We show that the numerical and asymptotic analysesprovide a mutually consistent global picture which supportsthe conclusion that, for the family of problems we considerhere, blow-up in fact can take place in three dimensions butat an inverse linear rate rather than the faster inverse squareof the plane case.