Long-range water accessibility study by ESE.

<p>The theoretical fits (red lines) to the ESE experimental data (blue lines) using a stretched exponential function (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068264#pone-0068264-t001" target="_blank">Table 1</a>) as previously described. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068264#pone.0068264-Huang1" target="_blank">[11]</a> The results for the n3β-s and PPm3-s are shown in (a) and (b), respectively. The decay signals acquired by the ESE experiments were fitted over the maxima of the deuterium modulation as described in Zecevic et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068264#pone.0068264-Zecevic1" target="_blank">[32]</a> to minimize the influence from destructive interference of nuclear modulations. The obtained values of the T_M (in ns) and stretching exponent x are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068264#pone-0068264-t001" target="_blank">Table 1</a>. The T_M values can be directly used to yield the surrounding proton density (<i>C_ex</i>; cf. Eq. 2) within the range of ∼2 nm from a nitroxide spin.</p

Determination of the n3β-d structure.

<p>(a) The time-domain DEER data for the n3β-d (0.5 mM) in the studied conditions, including the vitrified bulk solvent (sol(s)/H₂O) and the nanochannels (SBA15a and SBA15b). The gray lines represent the exponential baselines that best fit the DEER data. There are two insets. One displays a ribbon model for the n3β-d showing the spin-label side-chains at the 3rd and 9th sites of the peptide. The model was derived from a NMR study (PDB code: 1G04). The other inset shows the baseline-corrected DEER traces for the sol(s)/H₂O and the SBA15a, and also the simulated DEER traces (in green color) using the obtained P(r)s. There are some distinct differences in the two traces. (b) The (normalized) interspin distance distributions of the n3β-d peptides in the conditions studied. The average distances of the three measurements are approximately the same, indicating the n3β structure remains roughly unchanged. A much-broadened P(r) for the bulk solution study is obtained due to the solvent heterogeneity. The inset shows the Pake doublets converted from the DEER data. (c) Cw-ESR spectra of the n3β-d at 50 K. The clustering, caused by the solvent heterogeneity at 50 K, is evidently observed in the cw-ESR spectra of the bulk solution study, but not in the nanochannel studies.</p

Water accessibility study of the PPm3-s by ESEEM.

<p>(a) Three-pulse ESEEM time-domain data (solid lines) after the removal of the exponential decaying function in the raw data. The modulation depth is directly correlated to the peak intensity of the FT-ESEEM and can be quantitatively characterized by the best-fit parameter <i>k_D</i> (cf. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068264#pone-0068264-t001" target="_blank">Table 1</a>). The dashed lines represent the theoretical fits to the experimental data using the equation described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068264#pone-0068264-g003" target="_blank">Figure 3</a>. (b) The FT-ESEEM data for the PPm3-s in various deuterated conditions. The peaks correspond to the Larmor frequency of nucleus ²H, indicating the PPm3-s is surrounded by D₂O. The inset shows a ribbon model of a PPm3 variant carrying three spin labels.</p

Parameters obtained in the analyses of the ESE and ESEEM data.^§

§<p>Estimated errors: 5%(T_M), 10%(x), 13% (<i>C_ex</i>), 5% (<i>k_D</i>), 10% (Π). Abbreviations: <b>n3-s-a</b> (the n3-s is within SBA15a containing pure water); <b>n3-s-b</b> (the n3-s is within SBA15b containing pure water); <b>n3-s-sol(s)</b> (the n3-s is in a vitrified bulk solvent containing 40 wt% sucrose, (s), in D₂O or H₂O); <b>PPm3-s-sol(g)</b> (PPm3-s is in a vitrified bulk solvent containing 40v/v% glycerol in H₂O; deuterated glycerol is used if the solvent is D₂O, a condition of which is represented by sol(dg)/D₂O in main text); <b>PPm3-s-sol(s)</b> (PPm3-s is in a vitrified bulk solvent containing 40 wt% sucrose in D₂O or H₂O). In all of the experiments, the surface group of the nanochannels is modified to –SiOD in advance if D₂O is used. See Method for details.</p>#<p>The values of T_M and x are obtained in the analysis of the pulsed ESE measurements using a stretched exponential function, , where τ is the time between the two pulses, x the exponent, and Y(0) is the echo intensity at τ  = 0. The obtained values are used to yield <i>C_ex</i> using Eq. (2). The <i>C_ex</i> represents ESE-based water accessibility within the range of ∼2 nm from the nitroxide spin.</p>¶<p>The <i>k_D</i> values are obtained in the theoretical analysis of the ESEEM measurements as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068264#pone-0068264-g003" target="_blank">Figure 3</a>. The best-fit values for the damping constant (<i>τ₀</i>) and phase (φ) are very close together (2.9∼3.0). The Π represents ESEEM-based water accessibility within the range of ∼0.35 nm from the nitroxide spin.</p

Determination of the n3α-d structure.

<p>(a) The time-domain DEER signals of the studied conditions. The gray lines represent the exponential baselines that best fit the data. Inset shows a ribbon model of the n3α-d derived from NMR data (PDB code: 1M25). (b) The P(r) distributions extracted from the time-domain DEER data by the Tikhonov regularization analysis. The average distances (∼2.0 nm) are consistent with the expectation. (c) The cw-ESR spectra of the n3α-d. The spectra of the bulk solution studies are characterized by a broader linewidth and the spectral heterogeneity (indicated by arrows) as compared to the spectra of the nanochannel studies.</p

Intrinsic Optical Properties and Divergent Doping Effects of Manganese(II) on Luminescence for Tin(II) Phosphite Grown from a Deep-Eutectic Solvent

This is the first study on the ionothermal synthesis, intrinsic photoluminescence (PL), and dopant effects for tin­(II) phosphite, a stereochemically active 5s² lone-pair-electron-containing compound, the fundamental properties of which have rarely been explored before. In a new deep-eutectic solvent, single-phased products of SnHPO₃ (<b>1</b>) and Sn_1–<i>x</i>Mn_<i>x</i>HPO₃ (<b>2</b>) have been achieved in high yield. The crystalline powder of <b>1</b> is nonenantiomorphic, with an intense second-harmonic generation comparable to that of potassium dihydrogen phosphate. Under UV excitation, it unexpectedly emits white PL, an important intrinsic property never discovered in tin­(II) oxysalts. Electron paramagnetic resonance hyperfine splitting characteristic of manganese has been detected on <b>2</b> and a three-pulse electron-spin-echo envelope modulation technique implemented to locate its corresponding location in the inorganic host. On the basis of temperature-dependent PL and lifetime measurements, the incorporated Mn²⁺ uncommonly acts as a sensitizer in enhancing white emission until extremely low temperatures, in which it would resume its normal role as an activator to give out characteristic orange light

A Structurally Characterized Nonheme Cobalt–Hydroperoxo Complex Derived from Its Superoxo Intermediate via Hydrogen Atom Abstraction

Bubbling O₂ into a THF solution of Co^II(BDPP) (<b>1</b>) at −90 °C generates an O₂ adduct, Co­(BDPP)­(O₂) (<b>3</b>). The resonance Raman and EPR investigations reveal that <b>3</b> contains a low spin cobalt­(III) ion bound to a superoxo ligand. Significantly, at −90 °C, <b>3</b> can react with 2,2,6,6-tetramethyl-1-hydroxypiperidine (TEMPOH) to form a structurally characterized cobalt­(III)-hydroperoxo complex, Co^III(BDPP)­(OOH) (<b>4</b>) and TEMPO^•. Our findings show that cobalt­(III)-superoxo species are capable of performing hydrogen atom abstraction processes. Such a stepwise O₂-activating process helps to rationalize cobalt-catalyzed aerobic oxidations and sheds light on the possible mechanism of action for Co-bleomycin