Schematic view of the operation principle of the MEMS magnetic field sensor.

<p>Schematic view of the operation principle of the MEMS magnetic field sensor.</p

SNR calculations from 5 experiments in which we applied several increasing input noises (See Figure 7).

<p>SNR calculations from 5 experiments in which we applied several increasing input noises (See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109534#pone-0109534-g007" target="_blank">Figure 7</a>).</p

Block diagram of the signal conditioning system of the MEMS magnetic field sensor.

<p>Block diagram of the signal conditioning system of the MEMS magnetic field sensor.</p

MEMS magnetic flux density measured to calculate the detection threshold of the MEMS sensor (See figure 5A).

<p>MEMS magnetic flux density measured to calculate the detection threshold of the MEMS sensor (See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109534#pone-0109534-g005" target="_blank">figure 5A</a>).</p

Experimental setup for the detection of magnetic signals by a MEMS sensor using stochastic resonance.

<p>Experimental setup for the detection of magnetic signals by a MEMS sensor using stochastic resonance.</p

Recordings of continuous MEMS magnetic flux density and their corresponding power spectrum density.

<p><b>A</b>, applied subthreshold magnetic stimulus (input). <b>B, D and F</b>, recordings of the detected MEMS magnetic flux density at three noise levels: zero, optimal, and high noise. Note that the probability to detect a signal is increased when an optimal level of magnetic noise was added. <b>C, E and G</b>, corresponding power spectrum densities (PSD) for the MEMS recordings illustrated in the left panel. The power spectra of the MEMS show a peak at the input frequency (1 Hz) for optimal noise but not for zero or high noise. The gray rectangle in the PSD illustrates the frequency of the detected periodic magnetic signal in which there is a peak for the optimal noise level.</p

SEM image of the resonant structure of the MEMS magnetic field sensor.

<p>SEM image of the resonant structure of the MEMS magnetic field sensor.</p

Design, Preparation, and Characterization of Zn and Cu Metallopeptides Based On Tetradentate Aminopyridine Ligands Showing Enhanced DNA Cleavage Activity

The conjugation of redox-active complexes that can function as chemical nucleases to cationic tetrapeptides is pursued in this work in order to explore the expected synergistic effect between these two elements in DNA oxidative cleavage. Coordination complexes of biologically relevant first row metal ions, such as Zn­(II) or Cu­(II), containing the tetradentate ligands 1,4-dimethyl-7-(2-pyridylmethyl)-1,4,7-triazacyclononane (^Me2PyTACN) and (2<i>S</i>,2<i>S</i>′)-1,1′-bis­(pyrid-2-ylmethyl)-2,2′-bipyrrolidine ((<i>S,S</i>′)-BPBP) have been linked to a cationic LKKL tetrapeptide sequence. Solid-phase synthesis of the peptide-tetradentate ligand conjugates has been developed, and the preparation and characterization of the corresponding metallotetrapeptides is described. The DNA cleavage activity of Cu and Zn metallopeptides has been evaluated and compared to their metal binding conjugates as well as to the parent complexes and ligands. Very interestingly, the oxidative Cu metallopeptides <b>1</b>_<b>Cu</b> and <b>2</b>_<b>Cu</b> show an enhanced activity compared to the parent complexes, [Cu­(PyTACN)]²⁺ and [Cu­(BPBP)]²⁺, respectively. Under optimized conditions, <b>1</b>_<b>Cu</b> displays an apparent pseudo first-order rate constant (<i>k</i>_obs) of ∼0.16 min^–1 with a supercoiled DNA half-life time (<i>t</i>_1/2) of ∼4.3 min. On the other hand, <i>k</i>_obs for <b>2</b>_<b>Cu</b> has been found to be ∼0.11 min^–1 with <i>t</i>_1/2 ≈ 6.4 min. Hence, these results point out that the DNA cleavage activities promoted by the metallopeptides <b>1</b>_<b>Cu</b> and <b>2</b>_<b>Cu</b> render ∼4-fold and ∼23 rate accelerations in comparison with their parent Cu complexes. Additional binding assays and mechanistic studies demonstrate that the enhanced cleavage activities are explained by the presence of the cationic LKKL tetrapeptide sequence, which induces an improved binding affinity to the DNA, thus bringing the metal ion, which is responsible for cleavage, in close proximity