Using ultraviolet absorption spectroscopy to study nanoswitches based on non-canonical DNA structures

Non-canonical forms of DNA are attracting increasing interest for applications in nanotechnology. It is frequently convenient to characterize DNA molecules using a label-free approach such as ultraviolet absorption spectroscopy. In this paper we present the results of our investigation into the use of this technique to probe the folding of quadruplex and triplex nanoswitches. We confirmed that four G-quartets were necessary for folding at sub-mM concentrations of potassium and found that the wrong choice of sequence for the linker between G-tracts could dramatically disrupt folding, presumably due to the presence of kinetic traps in the folding landscape. In the case of the triplex nanoswitch we examined, we found that the UV spectrum showed a small change in absorbance when a triplex was formed. We anticipate that our results will be of interest to researchers seeking to design DNA nanoswitches based on quadruplexes and triplexes

Heart Failure in Humans Reduces Contractile Force in Myocardium from Both Ventricles

This study measured how heart failure affects the contractile properties of the human myocardium from the left and right ventricles. The data showed that maximum force and maximum power were reduced by approximately 30% in multicellular preparations from both ventricles, possibly because of ventricular remodeling (e.g., cellular disarray and/or excess fibrosis). Heart failure increased the calcium (Ca2+) sensitivity of contraction in both ventricles, but the effect was bigger in right ventricular samples. The changes in Ca2+ sensitivity were associated with ventricle-specific changes in the phosphorylation of troponin I, which indicated that adrenergic stimulation might induce different effects in the left and right ventricles

Empirical Verification of the Fe II Oscillator Strengths in the FUSE Bandpass

We report empirical determinations of atomic oscillator strengths, or f-values, for 11 ground-state transitions of Fe II in the wavelength range 1050 to 1150 Ang. We use ultraviolet absorption line observations of interstellar material towards stars in the Galaxy and the Magellanic Clouds taken with Copernicus, the Goddard High Resolution Spectrograph on-board the Hubble Space Telescope, and the Far Ultraviolet Spectroscopic Explorer. We derive absolute oscillator strengths by a combination of the apparent optical depth, component fitting, and curve-of-growth fitting techniques. Our derived oscillator strengths are generally in excellent agreement with recent theoretical calculations by Raassen & Uylings using the orthogonal operator technique. However, we identify three of the eleven transitions studied here whose f-values seem to be incompatible with these calculations, by as much as a factor of two. We suggest revisions to these f-values based upon our analysis.Comment: To appear in the Astrophysical Journal. 31 pages, including 8 embedded tables and 10 embedded figures. Also available at http://fuse.pha.jhu.edu/~howk/Papers

Patterns Of Intimate Partner Violence And Sexual Risk Behavior Among Young Heterosexually Active Men

Intimate partner violence (IPV) victimization is linked to sexual risk exposure among women. However, less is known about the intersection of IPV perpetration and sexual risk behavior among men. This study used data from a diverse, community sample of 334 heterosexually active young men, aged 18 to 25, across the United States to examine whether and how men with distinct IPV-related behavior patterns differed in sexual riskÃrelated behavior and attitudes. Participants were recruited and surveyed online, and grouped conceptually based on the types of IPV perpetration behavior(s) used in a current or recent romantic relationship. Groups were then compared on relevant sexual risk variables. Men reporting both physical abuse and sexual coercion against intimate partners reported significantly higher numbers of lifetime partners, higher rates of nonmonogamy, greater endorsement of nonmonogamy, and less frequent condom use relative to nonabusive men or those reporting controlling behavior only. This group also had higher sexually transmitted infection (STI) exposure compared to men who used controlling behavior only and men who used sexual coercion only. Findings suggest that interventions with men who use physical and sexual violence need to account for not only the physical and psychological harm of this behavior but also the sexual risk to which men may expose their partners