The reliability of the swimming ergometer in obtaining VO₂ max of male and female age-group swimmers

This study was designed to test the reliability of the swimming ergonometer in obtaining VO2 max of male and female age-group swimmers

Long-range electron transfer in structurally engineered pentaammineruthenium (histidine-62) cytochrome c

In many biological processes, long-range electron transfer (ET) plays a key role. When the three-dimensional structures of proteins are accurately known, use of modified proteins and protein-protein complexes provides an experimental approach to study ET rates between two metal centers. For Ru(His)- modified proteins, the introduction of histidine residues at any desired surface location by site-directed mutagenesis opens the way for systematic investigations of ET pathways

Spectroscopic and redox properties of amine-unctionalized K_2[Os-^(II)(bpy)(CN)_4] complexes

We report the first examples of amine-functionalized K_2[Os^(II)(bpy)(CN)_4] (bpy = 2,2'-bipyridine) complexes. The tetracyanoosmate complexes were prepared by UV irradiation (λ = 254 nm) of K_4[Os^(II)(CN)_6] and primary amine-functionalized bpy ligands in acidic aqueous media. The aqueous solution pH dependences of the spectroscopic and redox properties of 4,4'- and 5,5'-substituted complexes have been investigated. The pendant amine functional groups and coordinated cyanide ligands are basic sites that can be sequentially protonated, thereby allowing systematic tuning of electrochemical and optical spectroscopic properties

Automated Synthesis of 3‘-Metalated Oligonucleotides

We report the first synthesis of a metallonucleoside bound to a solid support and subsequent oligonucleotide synthesis with this precursor. Large-scale syntheses of metal-containing oligonucleotides are achieved using a solid support modified with [Ru(bpy)_2(impy‘)]^(2+) (bpy is 2,2‘-bipyridine; impy‘ is 2‘-iminomethylpyridyl-2‘-deoxyuridine). A duplex formed with the metal-containing oligonucleotide exhibits superior thermal stability when compared to the corresponding unmetalated duplex (Tm = 50 °C vs T_m = 48 °C). Electrochemical (E_(1/2) = 1.3 V vs NHE), absorption (λ_(max) = 480 nm), and emission (λ_(max) = 720 nm, τ = 44 ns, Φ = 0.11 × 10^(-3)) data for the ruthenium-modified oligonucleotides indicate that the presence of the oligonucleotide does not perturb the electronic properties of the ruthenium complex. The absence of any change in the emission properties upon duplex formation suggests that the [Ru(bpy)_2(impy)]^(2+) chromophore will be a valuable probe for DNA-mediated electron-transfer studies. Despite the relatively high Ru(III/II) reduction potential, oxidative quenching of photoexcited [Ru(bpy)_2(impy)]^(2+) does not lead to oxidative damage of guanine or other DNA bases

Measures for simulator evaluation of a helicopter obstacle avoidance system

The U.S. Army Aeroflightdynamics Directorate (AFDD) has developed a high-fidelity, full-mission simulation facility for the demonstration and evaluation of advanced helicopter mission equipment. The Crew Station Research and Development Facility (CSRDF) provides the capability to conduct one- or two-crew full-mission simulations in a state-of-the-art helicopter simulator. The CSRDF provides a realistic, full field-of-regard visual environment with simulation of state-of-the-art weapons, sensors, and flight control systems. We are using the CSRDF to evaluate the ability of an obstacle avoidance system (OASYS) to support low altitude flight in cluttered terrain using night vision goggles (NVG). The OASYS uses a laser radar to locate obstacles to safe flight in the aircraft's flight path. A major concern is the detection of wires, which can be difficult to see with NVG, but other obstacles--such as trees, poles or the ground--are also a concern. The OASYS symbology is presented to the pilot on a head-up display mounted on the NVG (NVG-HUD). The NVG-HUD presents head-stabilized symbology to the pilot while allowing him to view the image intensified, out-the-window scene through the HUD. Since interference with viewing through the display is a major concern, OASYS symbology must be designed to present usable obstacle clearance information with a minimum of clutter

A Steroid-Conjugated Contrast Agent for Magnetic Resonance Imaging of Cell Signaling

We have synthesized the first steroid hormone−MR contrast agent conjugate designed to track the cell signaling process upon binding to a gene switch system. The derivative has a high relaxivity and when tested in vitro is active as a progesterone antagonist (RU-486). By combining a transcriptional system and a noninvasive imaging technology, such as MRI, it would be a powerful tool to research the cell signaling pathway in vivo

Spectroscopy and Electrochemistry of Ruthenium-Modified Nucleic Acids: Design of a Novel Metal-Binding Nucleoside

Electron transfer (ET) reactions through DNA have been the subject of numerous investigations due to the implications for light-induced DNA damage and the quest for understanding long-range ET events in biological molecules. An important objective in this area continues to be the facile and site-specific incorporation of metal complexes into DNA. While recent work has focused on nucleobasic and nonnucleosidic sites for the attachment of high-potential complexes, our efforts have concentrated on the ribose ring (to minimize structural perturbations) as the incorporation site for both high- and low-potential metal complexes

Rational Design, Synthesis, and Biological Evaluation of Progesterone-Modified MRI Contrast Agents

SummaryA series of contrast agents for magnetic resonance imaging (MRI) aimed at noninvasively determining the hormone receptor status of cancer in vitro was developed. These MRI contrast agents were prepared by conjugating progesterone to clinically used Gd(III) chelates. These agents exhibited higher progesterone receptor binding affinities in the nanomolar range and intracellular accumulation. High logP values of the modified compounds suggested that the lipophilicity of the steroid conjugates may have contributed to membrane permeability. Synchrotron radiation X-ray fluorescence microscopy and magnetic resonance images revealed that the synthesized conjugates showed the greatest cellular accumulation and significant increase in relaxivity in vitro compared to the previously developed steroid-modified agent. Transcriptional assays using the progesterone response element linked to luciferase indicated that the contrast agents entered the cell, interacted with the biological target, and drove specific progesterone-mediated transcription

Spectroscopy and Electrochemistry of Cobalt(III) Schiff Base Complexes

The structural, spectroscopic, and electrochemical properties of cobalt(III) derivatives of acacen (H_2acacen = bis(acetylacetone) ethylenediimine) and related ligands have been investigated. Electronic structure calculations indicate that the absorption between 340 and 378 nm in Co^(III)(acacen) spectra is attributable to the lowest π−π* intraligand charge-transfer transition. Equatorial ligand substitutions affect reduction potentials less than axial ligand changes, consistent with an electronic structural model in which d_(z^2) is populated in forming cobalt(II). The crystal structure of [Co(3-Cl-acacen)(NH_3)_2]BPh_4 has been determined:  The compound crystallizes in the monoclinic space group (P2_1)/m (No. 11) with a = 9.720(2) Å, b = 18.142(4) Å, c = 10.046(2) Å, β = 100.11(3)°, D_c = 1.339 g cm^(-3), and Z = 2; the complex cation, [Co(3-Cl-acacen)(NH_3)_2]^+, exhibits a slightly distorted octahedral coordination geometry. The distances between the cobalt atom and the two axial nitrogen donor atoms differ only slightly (1.960(6) and 1.951(6) Å) and are similar to Co−N distances found in cobalt−ammine complexes as well as the axial Co−N distances in [Co(acacen)(4-MeIm)_2]Br·1.5H_2O; the latter compound crystallizes in the triclinic space group P1̄ (No. 2) with a = 18.466(9) Å, b = 14.936(7) Å, c = 10.111(5)Å, α = 96.27(5)°, β = 94.12(5)°, γ = 112.78(5)°, D_c = 1.447 g cm^(-3), and Z = 4