Relative abundance of the human mitochondrial transcription system and distinct roles for h-mtTFB1 and h-mtTFB2 in mitochondrial biogenesis and gene expression

Human mitochondrial transcription requires the bacteriophage-related RNA polymerase, POLRMT, the mtDNA-binding protein, h-mtTFA/TFAM, and two transcription factors/rRNA methyltransferases, h-mtTFB1 and h-mtTFB2. Here, we determined the steady-state levels of these core transcription components and examined the consequences of purposeful elevation of h-mtTFB1 or h-mtTFB2 in HeLa cells. On a per molecule basis, we find an ∼6-fold excess of POLRMT to mtDNA and ∼3-fold more h-mtTFB2 than h-mtTFB1. We also estimate h-mtTFA at ∼50 molecules/mtDNA, a ratio predicted to support robust transcription, but not to coat mtDNA. Consistent with a role for h-mtTFB2 in transcription and transcription-primed replication, increased mitochondrial DNA and transcripts result from its over-expression. This is accompanied by increased translation rates of most, but not all mtDNA-encoded proteins. Over-expression of h-mtTFB1 did not significantly influence these parameters, but did result in increased mitochondrial biogenesis. Furthermore, h-mtTFB1 mRNA and protein are elevated in response to h-mtTFB2 over-expression, suggesting the existence of a retrograde signal to the nucleus to coordinately regulate expression of these related factors. Altogether, our results provide a framework for understanding the regulation of human mitochondrial transcription in vivo and define distinct roles for h-mtTFB1 and h-mtTFB2 in mitochondrial biogenesis and gene expression that together likely fine-tune mitochondrial function

Worm-like micelles of triblock copolymer of ethylene oxide and styrene oxide characterised using light scattering and Taylor dispersion analysis

A triblock ESE copolymer (E16S8E16, S = styrene oxide and E = ethylene oxide) was synthesised by sequential oxyanionic copolymerisation of styrene oxide followed by ethylene oxide. Light scattering studies demonstrated a shape transition from spherical micelles to worm-like micelles above a critical temperature of approximately 18oC. Taylor dispersion analysis (TDA) also indicated a size growth when the temperature increased from 25 to 40 oC due to the formation of worm-like micelles. The hydrodynamic radii and diffusion coefficients obtained by these two techniques were in good agreement. The solubility of a hydrophobic drug, terfenadine, in dilute micellar solutions of the copolymer was increased at least 20-fold under the conditions. The transition to worm-like micelles at raised temperatures led to enhanced solubilisation capacities due to a larger hydrophobic core volume. The behaviour of the novel ESE copolymer shows the utility of TDA to follow conformational changes using nanolitre quantities and explore critical quality attributes for this type of drug delivery system

Observation of exclusive DVCS in polarized electron beam asymmetry measurements

We report the first results of the beam spin asymmetry measured in the reaction e + p -> e + p + gamma at a beam energy of 4.25 GeV. A large asymmetry with a sin(phi) modulation is observed, as predicted for the interference term of Deeply Virtual Compton Scattering and the Bethe-Heitler process. The amplitude of this modulation is alpha = 0.202 +/- 0.028. In leading-order and leading-twist pQCD, the alpha is directly proportional to the imaginary part of the DVCS amplitude.Comment: 6 pages, 5 figure

Observation of an Exotic S=+1S=+1 Baryon in Exclusive Photoproduction from the Deuteron

In an exclusive measurement of the reaction $\gamma d \to K^+ K^- p n$, a narrow peak that can be attributed to an exotic baryon with strangeness $S=+1$ is seen in the $K^+n$ invariant mass spectrum. The peak is at $1.542\pm 0.005$ GeV/c$^2$ with a measured width of 0.021 GeV/c$^2$ FWHM, which is largely determined by experimental mass resolution. The statistical significance of the peak is $5.2 \pm 0.6 \sigma$. The mass and width of the observed peak are consistent with recent reports of a narrow $S=+1$ baryon by other experimental groups.Comment: 5 pages, 5 figure

Photoproduction of phi(1020) mesons on the proton at large momentum transfer

The cross section for $\phi$ meson photoproduction on the proton has been measured for the first time up to a four-momentum transfer -t = 4 GeV^2, using the CLAS detector at the Thomas Jefferson National Accelerator Facility. At low four-momentum transfer, the differential cross section is well described by Pomeron exchange. At large four-momentum transfer, above -t = 1.8 GeV^2, the data support a model where the Pomeron is resolved into its simplest component, two gluons, which may couple to any quark in the proton and in the $\phi$.Comment: 5 pages; 7 figure

Measurement of Beam-Spin Asymmetries for Deep Inelastic π+\pi^+ Electroproduction

We report the first evidence for a non-zero beam-spin azimuthal asymmetry in the electroproduction of positive pions in the deep-inelastic region. Data have been obtained using a polarized electron beam of 4.3 GeV with the CLAS detector at the Thomas Jefferson National Accelerator Facility (JLab). The amplitude of the $\sin\phi$ modulation increases with the momentum of the pion relative to the virtual photon, $z$, with an average amplitude of $0.038 \pm 0.005 \pm 0.003$ for $0.5 < z < 0.8$ range.Comment: 5 pages, RevTEX4, 3 figures, 2 table

Measurement of the Polarized Structure Function σLT′\sigma_{LT^\prime} for p(e⃗,e′p)πop(\vec{e},e'p)\pi^o in the Δ(1232)\Delta(1232) Resonance Region

The polarized longitudinal-transverse structure function $\sigma_{LT^\prime}$ has been measured in the $\Delta(1232)$ resonance region at $Q^2=0.40$ and 0.65 GeV$^2$. Data for the $p(\vec e,e'p)\pi^o$ reaction were taken at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) using longitudinally polarized electrons at an energy of 1.515 GeV. For the first time a complete angular distribution was measured, permitting the separation of different non-resonant amplitudes using a partial wave analysis. Comparison with previous beam asymmetry measurements at MAMI indicate a deviation from the predicted $Q^2$ dependence of $\sigma_{LT^{\prime}}$ using recent phenomenological models.Comment: 5 pages, LaTex, 4 eps figures: to be published in PRC/Rapid Communications. Version 2 has revised Q^2 analysi

Two-Nucleon Momentum Distributions Measured in 3He(e,e'pp)n

We have measured the 3He(e,e'pp)n reaction at 2.2 GeV over a wide kinematic range. The kinetic energy distribution for `fast' nucleons (p > 250 MeV/c) peaks where two nucleons each have 20% or less, and the third nucleon has most of the transferred energy. These fast pp and pn pairs are back-to-back with little momentum along the three-momentum transfer, indicating that they are spectators. Experimental and theoretical evidence indicates that we have measured distorted two-nucleon momentum distributions by striking the third nucleon and detecting the spectator correlated pair.Comment: 6 pages, 5 figures, submitted to PR

The e p -> e' p eta reaction at and above the S11(1535) baryon resonance

New cross sections for the reaction e p -> ep eta are reported for total center of mass energy W = 1.5--1.86 GeV and invariant momentum transfer Q^2 = 0.25--1.5 GeV^2. This large kinematic range allows extraction of important new information about response functions, photocouplings, and eta N coupling strengths of baryon resonances. Expanded W coverage shows sharp structure at W \~ 1.7 GeV; this is shown to come from interference between S and P waves and can be interpreted in terms of known resonances. Improved values are derived for the photon coupling amplitude for the S11(1535) resonance.Comment: 11 pages, RevTeX, 5 figures, submitted to Phys. Rev. Let

Measurement of Inclusive Spin Structure Functions of the Deuteron

We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer ($Q^2$ = 0.27 -- 1.3 (GeV/c)$^2$) and final hadronic state mass in the nucleon resonance region ($W$ = 1.08 -- 2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target ($^{15}$ND$_3$) and detected the scattered electrons with the CEBAF Large Acceptance Spectrometer (CLAS). From our data, we extract the longitudinal double spin asymmetry $A_{||}$ and the spin structure function $g_1^d$. Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function $g_1^d$ and study its approach to both the deep inelastic limit at large $Q^2$ and to the Gerasimov-Drell-Hearn sum rule at the real photon limit ($Q^2 \to 0$). We find that the first moment varies rapidly in the $Q^2$ range of our experiment and crosses zero at $Q^2$ between 0.5 and 0.8 (GeV/c)$^2$, indicating the importance of the $\Delta$ resonance at these momentum transfers.Comment: 13 pages, 8 figures, ReVTeX 4, final version as accepted by Phys. Rev.