Oligonucleotides Modified With Transplatin Derivatives: Fast and Efficient Metalloribozymes

When an oligonucleotide containing a 1,3-(G,G)-transplatin cross-link at a GNG site (N represents a C, T, A or U residue) is paired with its complementary strand, the intrastrand adduct rearranges into an interstrand cross-link, resulting in the covalent attachment of both strands. Here, we have studied the influence of the inert ligands of the platinum(II) complex and of the nucleotide residues in the vicinity of the adduct on the rearrangement reaction. Dramatic effects on the linkage isomerization rate could be 37℃. The results are analyzed in relation with the mechanism of rearrangement of the 1,3-intrastrand adducts into interstrand cross-links. The relevance of platinated oligonucleotides as potent and specific drugs is discussed

UVA-Photosensitivity of cis-Diamminedichloro-Platinum(II)-Modified DNA

cis-Diamminedichloroplatinum(II)-modified oligonucleotides contain-ing either a single intrastrand cross-link at the d(GpG) site or an interstrand cross-link at the d(GpC/GpC) site, were irradiated with 320 to 400-nm light. Upon irradiation, the adducts are photosensitive. Among the photo-induced reactions, the cleavage of the coordination bonds between platinum and the G residues in the interstrand cross-link is demonstrated

An analytical model for propeller aerodynamic efforts at high incidence

In the advent of electrical vertical take-off and landing aircraft development, a fast approach to predict variation of propeller axial and off-axis aerodynamic loads at large incidence angle has been desired. This paper presented an analytical approach obtained by a simplified blade element method considering local blade section conditions. The theory has been further validated against available experiments for propeller at high incidence conditions, and was found applicable to a wide range of geometries and operating conditions

Comparisons of Different Propeller Wake Models for a Propeller-Wing Combination

A detailed experimental study of propeller-wing interaction was presented. Five-hole probe was used to obtain velocity distribution at a survey plane behind trailing edge of a high-aspect-ratio wing with tractor propeller. Significant deformation of propeller slipstream was observed compared to a free propeller. The deformation was more prominent at low advance ratio, where transition flight of vertical take-off / landing aircraft were concerned. Comparison with two recent reduced-order slipstream models revealed large discrepancies between theoretical predictions and wake survey results. An analytical model of slipstream transverse deformation was proposed at the end that might be incorporated into improve such models

Analytic Model of Proprotor Forces and Moments at High Incidence

The paper presents an analytical model for estimation of proprotor aerodynamic loads at elevated incidence angles. Previous theories have concentrated on either small incidence angle for aircraft stability analysis, or edge-wise flow for helicopter forward flight. This development attempted an engineering method that covers full incidence angle range from $0$ to $\pi / 2$. Blade element theory was applied to known proprotor geometry, and off-axis loads including normal force and in-plane moment were obtained in closed form based on thrust and torque in axial condition. The model was found to be sufficiently accurate over a broader flight conditions compared to classical models, and computationally more efficient than numerical methods. Hence it could be easily used as a preliminary design and analysis tool for future convertible aircraft proprotors. The paper further discusses a dedicated wind tunnel campaign on proprotor off-axis load measurement. Experimental data from the test campaign was considered in model validation. The results suggested that the model was capable to accurately estimate proprotor performance in nominal flight regimes

Slipstream Deformation of a Propeller-Wing Combination Applied for Convertible UAVs in Hover Condition

Convertible unmanned aerial vehicle (UAV) promises a good balance between convenient autonomous launch/recovery and efficient long range cruise performance. Successful design of this new type of aircraft relies heavily on good understanding of powered lift generated through propeller-wing interactions, where the velocity distribution within propeller slipstream is critical to estimate aerodynamic forces during hover condition. Current study analysed a propeller-wing combination with a plain flap. A 5-hole probe measurement system was built to construct 3 dimensional velocity field at a survey plane after trailing edge. The study has found that significant deformation of propeller slipstream was present in the form of opposite transverse displacement on extrados and intrados. The deformation could be enhanced by flap deflections. Velocity differences caused by the slipstream deformation could imply local variation of lift distribution compared to predictions from conventional assumptions of cylindrical slipstream. The research underlined that the mutual aspect of propeller-wing interaction could be critical for low-speed aerodynamic design

Microfluidic device for monitoring catalytic events on armored bubbles

Abstract: A polydimethylsiloxane‐based microfluidic device allows monitoring local oxidation events in organic solvents at the level of an individual air bubble armored with surface‐active low‐surface energy catalytic particles. This new technique permits tunable design of microreactors for gas‐liquid‐solid reactions

Aerodynamic Modeling of Propeller Forces and Moments at High Angle of Incidence

A reduced-order model to estimate the aerodynamic forces and moments of a propeller at incidence angle from 0° to 90° was presented. The objective was to provide an inexpensive and effective approach to analyse propeller performance of a vertical/short take-off and landing aerial vehicle during transition flight. The model was based on blade element theory and was coupled with an extended momentum theory or Pitt & Peters inflow model to include the asymmetrical flow condition. The aerofoil aerodynamic data was provided by an empirical model that extended lift and drag polar to a broad angle-of-attack range suitable in transition flight. Furthermore a rotational stall delay model and a radial flow correction model have been incorporated to include primary 3-dimensional effects. The result has been presented and compared with past experiment and unsteady Reynolds-averaged Navier-Stokes solution under similar conditions

RNA topoisomerase is prevalent in all domains of life and associates with polyribosomes in animals

DNA Topoisomerases are essential to resolve topological problems during DNA metabolism in all species. However, the prevalence and function of RNA topoisomerases remain uncertain. Here, we show that RNA topoisomerase activity is prevalent in Type IA topoisomerases from bacteria, archaea, and eukarya. Moreover, this activity always requires the conserved Type IA core domains and the same catalytic residue used in DNA topoisomerase reaction; however, it does not absolutely require the non-conserved carboxyl-terminal domain (CTD), which is necessary for relaxation reactions of supercoiled DNA. The RNA topoisomerase activity of human Top3β differs from that of Escherichia coli topoisomerase I in that the former but not the latter requires the CTD, indicating that topoisomerases have developed distinct mechanisms during evolution to catalyze RNA topoisomerase reactions. Notably, Top3β proteins from several animals associate with polyribosomes, which are units of mRNA translation, whereas the Top3 homologs from E. coli and yeast lack the association. The Top3β-polyribosome association requires TDRD3, which directly interacts with Top3β and is present in animals but not bacteria or yeast. We propose that RNA topoisomerases arose in the early RNA world, and that they are retained through all domains of DNA-based life, where they mediate mRNA translation as part of polyribosomes in animals