d(CGGTGGT) forms an octameric parallel G-quadruplex via stacking of unusual G(:C):G(:C):G(:C):G(:C) octads

Among non-canonical DNA secondary structures, G-quadruplexes are currently widely studied because of their probable involvement in many pivotal biological roles, and for their potential use in nanotechnology. The overall quadruplex scaffold can exhibit several morphologies through intramolecular or intermolecular organization of G-rich oligodeoxyribonucleic acid strands. In particular, several G-rich strands can form higher order assemblies by multimerization between several G-quadruplex units. Here, we report on the identification of a novel dimerization pathway. Our Nuclear magnetic resonance, circular dichroism, UV, gel electrophoresis and mass spectrometry studies on the DNA sequence dCGGTGGT demonstrate that this sequence forms an octamer when annealed in presence of K+ or NH4+ ions, through the 5′-5′ stacking of two tetramolecular G-quadruplex subunits via unusual G(:C):G(:C):G(:C):G(:C) octads

Contributions of the two accessory subunits, RNASEH2B and RNASEH2C, to the activity and properties of the human RNase H2 complex

Eukaryotic RNase H2 is a heterotrimeric enzyme. Here, we show that the biochemical composition and stoichiometry of the human RNase H2 complex is consistent with the properties previously deduced from genetic studies. The catalytic subunit of eukaryotic RNase H2, RNASEH2A, is well conserved and similar to the monomeric prokaryotic RNase HII. In contrast, the RNASEH2B and RNASEH2C subunits from human and Saccharomyces cerevisiae share very little homology, although they both form soluble B/C complexes that may serve as a nucleation site for the addition of RNASEH2A to form an active RNase H2, or for interactions with other proteins to support different functions. The RNASEH2B subunit has a PIP-box and confers PCNA binding to human RNase H2. Unlike Escherichia coli RNase HII, eukaryotic RNase H2 acts processively and hydrolyzes a variety of RNA/DNA hybrids with similar efficiencies, suggesting multiple cellular substrates. Moreover, of five analyzed mutations in human RNASEH2B and RNASEH2C linked to Aicardi-Goutières Syndrome (AGS), only one, R69W in the RNASEH2C protein, exhibits a significant reduction in specific activity, revealing a role for the C subunit in enzymatic activity. Near-normal activity of four AGS-related mutant enzymes was unexpected in light of their predicted impairment causing the AGS phenotype

Applications of Isothermal Titration Calorimetry in Biophysical Studies of G-quadruplexes

G-quadruplexes are higher-order nucleic acids structures formed by G-rich sequences that are stabilized by tetrads of hydrogen-bonded guanine bases. Recently, there has been growing interest in the study of G-quadruplexes because of their possible involvement in many biological processes. Isothermal titration calorimetry (ITC) has been proven to be a useful tool to study the energetic aspects of G-quadruplex interactions. Particularly, ITC has been applied many times to determine the thermodynamic properties of drug-quadruplex interactions to screening among various drugs and to address drug design. In the present review, we will focus on the ITC studies of G-quadruplex structures and their interaction with proteins and drugs and the most significant results will be discussed

siRNA-Like Double-Stranded RNAs Are Specifically Protected Against Degradation in Human Cell Extract

RNA interference (RNAi) is a set of intracellular pathways in eukaryotes that controls both exogenous and endogenous gene expression. The power of RNAi to knock down (silence) any gene of interest by the introduction of synthetic small-interfering (si)RNAs has afforded powerful insight into biological function through reverse genetic approaches and has borne a new field of gene therapeutics. A number of questions are outstanding concerning the potency of siRNAs, necessitating an understanding of how short double-stranded RNAs are processed by the cell. Recent work suggests unmodified siRNAs are protected in the intracellular environment, although the mechanism of protection still remains unclear. We have developed a set of doubly-fluorophore labeled RNAs (more precisely, RNA/DNA chimeras) to probe in real-time the stability of siRNAs and related molecules by fluorescence resonance energy transfer (FRET). We find that these RNA probes are substrates for relevant cellular degradative processes, including the RNase H1 mediated degradation of an DNA/RNA hybrid and Dicer-mediated cleavage of a 24-nucleotide (per strand) double-stranded RNA. In addition, we find that 21- and 24-nucleotide double-stranded RNAs are relatively protected in human cytosolic cell extract, but less so in blood serum, whereas an 18-nucleotide double-stranded RNA is less protected in both fluids. These results suggest that RNAi effector RNAs are specifically protected in the cellular environment and may provide an explanation for recent results showing that unmodified siRNAs in cells persist intact for extended periods of time

1770

Reliure plein veau marbré d'époque, dos orné à cinq nerfs. Intérieur en bon état, le f. de titre légèrement sali

Cultures du pastel, de la gaude, et de la garance a l'usage des cultivateurs et des manufactures

Sign.: A8, B4, C8, D4, E9Error en sign. y p., pues incluye las p. 199-200, 197-198 de la otra obra con la que está encEnc. formando un vol. facticio junto con : "L'art de la teinture des fils et étoffes de coton, précédé d'une théorie nouvelle des véritables causes... .- A Paris : chez Moutard,..., 177

El cuerpo humano

Blanco Prieto es uno de los seud. utilizados por Amancio Peratoner (según Rogers y Lapuente

Herrn le Pileur d'Apligny, Richtige und vollständige Beschreibung aller Farbmaterialien : nebst einer deutlichen Anweisung wie solche zu dem Gebrauche zubereitet, und bei den dahin einschlagenden Künsten und Professionen gehörig angewendet werden sollen

aus dem Französischen übers. und mit des Herrn Loriots entdeckten Geheimniss die Pastelfarben zu fixiren vermehrt, wie auch mit sehr vielen andern Zusätzen vermehretOriginaltitel: Traité des couleurs matérielles et de la manière de colore

Essai sur les moyens de perfectionner l'art de la teinture et observations sur quelques matiéres qui y sont propres

Marca tip. en la portSign.: a12, A-G12Texto con apostillas marginalesCabecera con adorno xi