Kinetics of Proton Transport into Influenza Virions by the Viral M2 Channel

M2 protein of influenza A viruses is a tetrameric transmembrane proton channel, which has essential functions both early and late in the virus infectious cycle. Previous studies of proton transport by M2 have been limited to measurements outside the context of the virus particle. We have developed an in vitro fluorescence-based assay to monitor internal acidification of individual virions triggered to undergo membrane fusion. We show that rimantadine, an inhibitor of M2 proton conductance, blocks the acidification-dependent dissipation of fluorescence from a pH-sensitive virus-content probe. Fusion-pore formation usually follows internal acidification but does not require it. The rate of internal virion acidification increases with external proton concentration and saturates with a pKm of ∼4.7. The rate of proton transport through a single, fully protonated M2 channel is approximately 100 to 400 protons per second. The saturating proton-concentration dependence and the low rate of internal virion acidification derived from authentic virions support a transporter model for the mechanism of proton transfer

Coupled substitution of H and minor elements in rutile and the implications of high OH contents in Nb- and Cr-rich rutile from the upper mantle

Infrared absorption spectra of rutile crystals from a variety of geological environments (carbonatite, hydrothermal vein, kyanite + rutile + lazulite association, xenoliths that are kimberlite hosted and dominated by Nb- and Cr-rich rutile) exhibit strong absorption in the 3300-cm^(-1) region due to interstitial protons bonded to structure O. In general the proton is located at sites slightly displaced from 1/21/20 of the unit cell, although some samples show evidence of additional protons at tetrahedral interstitial sites. H contents of rutile range up to 0.8 wt% H_2O, the highest concentrations occurring in mantle-derived Nb- and Cr-rich rutile of metasomatic origin. The role of H in rutile was examined, particularly with respect to its relations to other impurities. Protons are present in the rutile structure to compensate for trivalent substitutional cations (Cr Fe V AI) which are only partly compensated by pentavalent ions (Nb, Ta). The possibility of using the H content of rutile as a geohygrometer is illustrated for the case of coexisting hematite and rutile

Hydrogen speciation in synthetic quartz

The dominant hydrogen impurity in synthetic quartz is molecular H_2O. H-OH groups also occur, but there is no direct evidence for the hydrolysis of Si-O-Si bonds to yield Si-OH HO-Si groups. Molecular H_2O concentrations in the synthetic quartz crystals studied range from less than 10 to 3,300 ppm (H/Si), and decrease smoothly by up to an order of magnitude with distance away from the seed. OH− concentrations range from 96 to 715 ppm, and rise smoothly with distance away from the seed by up to a factor of three. The observed OH− is probably all associated with cationic impurities, as in natural quartz. Molecular H_2O is the dominant initial hydrogen impurity in weak quartz. The hydrolytic weakening of quartz may be caused by the transformation H_2O + Si-O-Si → 2SiOH, but this may be a transitory change with the SiOH groups recombining to form H_2O, and the average SiOH concentration remaining very low. Synthetic quartz is strengthened when the H_2O is accumulated into fluid inclusions and cannot react with the quartz framework

Ophirite, Ca_2Mg_4[Zn_2Mn_2^(3+)(H_2O)_2(Fe^(3+)W_9O_(34))_2]·46H_2O, a new mineral with a heteropolytungstate tri-lacunary Keggin anion

Ophirite, Ca_2Mg_4[Zn_2Mn_2^(3+)(H_2O)_2(Fe^(3+)W_9O_(34))_2]·46H_2O, is a new mineral species from the Ophir Hill Consolidated mine, Ophir district, Oquirrh Mountains, Tooele County, Utah, U.S.A. Crystals of ophirite are orange-brown tablets on {001} with irregular {100} and {110} bounding forms; individual crystals are up to about 1 mm in maximum dimension and possess a pale orange streak. The mineral is transparent, with a vitreous luster; it does not fluoresce in short- or long-wave ultraviolet radiation. Ophirite has a Mohs hardness of approximately 2 and brittle tenacity. No cleavage or parting was observed in the mineral. The fracture is irregular. The density calculated from the empirical formula using the single-crystal cell data is 4.060 g/cm^3. Ophirite is biaxial (+) with a 2V angle of 43(2)°. Indices of refraction for ophirite are α = 1.730(3), β = 1.735(3), γ = 1.770(3)°. The optic orientation (incompletely determined) is Y ∠ b ≈ 9° and one optic axis is approximately perpendicular to {001}. Dispersion r > v, strong; pleochroism is X = light orange brown, Y = light orange brown, Z = orange brown; X < Y << Z. Chemical analyses of ophirite were obtained by electron probe microanalysis; optimization of that analysis using the results of the crystal-structure analysis yielded the formula Formula (Ca_(1.46)Mg_(0.50)Zn_(0.04))_(Σ2.00)(Mg_(3.96)Mn^(3+)_(0.04))_(Σ4.00)[(Zn_(1.16)Fe^(3+)_(0.68)Ca_(0.14)Sb^(5+)_(0.02))_(Σ2.00)(Mn^(3+)_(1.42)Sb^(5+)_(0.32)Fe^(3+)_(0.24)W_(0.02))_(Σ2.00) {(H_2O)_2[(Fe^(3+)_(0.80)Sb^(5+)_(0.11)Ca_(0.07)Mg_(0.02))_Σ1.00)(W_(8.71)Mn^(3+)_(0.29))_(Σ1.00)]_2}]·46H_2O; the simplified formula of ophirite is Ca_2Mg_4[Zn_2Mn_2^(3+)(H_2O)_2(Fe^(3+)W_9O_(34))_2]·46H_2O. Ophirite is triclinic, P1macr;, with ɑ = 11.9860(2), b = 13.2073(2), c = 17.689(1) Å, α = 69.690(5), β = 85.364(6), γ = 64.875(5)°, V = 2370.35(18) Å3, and Z = 1. The strongest four lines in the diffraction pattern are [d in Å (I)(hkl)]: 10.169(100)(100,110), 11.33(91)(011,010), 2.992(75)(334,341,1̄ 1̄ 5), and 2.760(55)(412,006, 1̄ 3 5). The atomic arrangement of ophirite was solved and refined to R_1 = 0.0298 for 9230 independent reflections. The structural unit, ideally {^([6])Zn_2^([6])Mn_2^(3+)(H_2O)_2(^([4])Fe^(3+[6])W_9^(6+)O_(34))_2}^(12−), consists of a [Zn_2Mn_2^(3+)(H_2O)_2] octahedral layer sandwiched between opposing heteropolytungstate tri-lacunary (^([4])Fe^(3+[6])W_9^(6+)O_(34)) Keggin anions. Similar structures with an octahedral layer between two tri-lacunary Keggin anions are known in synthetic phases. Charge balance in the ophirite structure is maintained by the {[Mg(H_2O)_6]_4[Ca (H_2O)_6]_2·10H_2O}_(12+) interstitial unit. The interstitial unit in the structure of ophirite is formed of two distinct Mg(H_2O)_6 octahedra and a Ca(H_2O)_6O_1 polyhedron, as well as five isolated water molecules. The linkage between the structural unit and the interstitial unit results principally from hydrogen bonding between oxygen atoms of the structural unit with hydrogen atoms of the interstitial unit. Ophirite is the first known mineral to contain a lacunary defect derivative of the Keggin anion, a heteropolyanion that is well known in synthetic phases. The new mineral is named ophirite to recognize its discovery at the Ophir Hill Consolidated mine, Ophir District, Oquirrh Mountains, Tooele County, Utah, U.S.A

Oral Antioxidants Improve Leg Blood Flow during Exercise in Patients with Chronic Obstructive Pulmonary Disease

The consequence of elevated oxidative stress on exercising skeletal muscle blood flow as well as the transport and utilization of O2 in patients with chronic obstructive pulmonary disease (COPD) is not well understood. The present study examined the impact of an oral antioxidant cocktail (AOC) on leg blood flow (LBF) and O2 consumption during dynamic exercise in 16 patients with COPD and 16 healthy subjects. Subjects performed submaximal (3, 6, and 9 W) single-leg knee extensor exercise while LBF (Doppler ultrasound), mean arterial blood pressure, leg vascular conductance, arterial O2 saturation, leg arterial-venous O2 difference, and leg O2 consumption (direct Fick) were evaluated under control conditions and after AOC administration. AOC administration increased LBF (3 W: 1,604 ± 100 vs. 1,798 ± 128 ml/min, 6 W: 1,832 ± 109 vs. 1,992 ± 120 ml/min, and 9W: 2,035 ± 114 vs. 2,187 ± 136 ml/min, P \u3c 0.05, control vs. AOC, respectively), leg vascular conductance, and leg O2 consumption (3 W: 173 ± 12 vs. 210 ± 15 ml O2/min, 6 W: 217 ± 14 vs. 237 ± 15 ml O2/min, and 9 W: 244 ± 16 vs 260 ± 18 ml O2/min, P \u3c 0.05, control vs. AOC, respectively) during exercise in COPD, whereas no effect was observed in healthy subjects. In addition, the AOC afforded a small, but significant, improvement in arterial O2 saturation only in patients with COPD. Thus, these data demonstrate a novel beneficial role of AOC administration on exercising LBF, O2 consumption, and arterial O2 saturation in patients with COPD, implicating oxidative stress as a potential therapeutic target for impaired exercise capacity in this population