Functional specialization of the yeast Rho1 GTP exchange factors

Rho GTPases are regulated in complex spatiotemporal patterns that may be dependent, in part at least, on the multiplicity of their GTP exchange factors (GEFs). Here, we examine the extent of and basis for functional specialization of the Rom2 and Tus1 GEFs that activate the yeast Rho1 GTPase, the ortholog of mammalian RhoA. First, we find that these GEFs selectively activate different Rho1-effector branches. Second, the synthetic genetic networks around ROM2 and TUS1 confirm very different global in vivo roles for these GEFs. Third, the GEFs are not functionally interchangeable: Tus1 cannot replace the essential role of Rom2, even when overexpressed. Fourth, we find that Rom2 and Tus1 localize differently: Rom2 to the growing bud surface and to the bud neck at cytokinesis; Tus1 only to the bud neck but in a distinct pattern. Finally, we find that these GEFs are dependent on different protein co-factors: Rom2 function and localization is largely dependent on Ack1, a SEL1 domain containing protein; Tus1 function and localization is largely dependent on the Tus1-interacting protein Ypl066w (which we name Rgl1). We have revealed a surprising level of diversity among the Rho1 GEFs that contributes another level of complexity to the spatiotemporal control of Rho1

Soil acidity on high rainfall pastures

Most soils of the high rainfall area of south-western Western Australia are naturally acis. The most acid group of soils, the peaty sands. have been routinely limed before subterranean clover pastures were established since research in the 1950s showed that poor Rhizobium nodulation could be overcome with the application of about 2 tonnes per hectare of coastal limesand

Soil acidity - high rainfall pastures

A. Lime on old land pastures. 80BU13, 80BU14, 80BU15, 80BU16, 80BU17, 80BY7, 80BY16, 81AL10, 81AL11, 8IAL12, 81AL13, 81AL14, 81AL15, 81AL16, 81BU18, 81BY15, 81BY16, 81BY17, 81BY18, 81BY19, 81BY24, 81BY25, 81BY16, 81MA12, 81W9, 81Wl0, 81Wll, 82AL2, 82AL3, 82AL4, 82ALS, 82AL6, 82ALSS, 82BU6, 82BU7, 82BU8, 82BY37, 82HA35, 82HA36, 82HA38, 82MA20, 82PE1, 83AL7, 83AL8, 83AL9, 83AL10, 83AL11, 83AL12, 83AL13, 83AL14, 83BU20, 83BU24, 83BU25, 83BU26, 83BY29, 83HA19, 83HA40, 83HA41. B. Lime on new land pastures 82AL7, 82AL8

Visualisation and optimisation of shielding gas coverage during gas metal arc welding

The density gradients and flow characteristics of the gas shield during gas metal arc welding (GMAW) of DH36, higher strength ‘construction steel’ were visualised using schlieren imaging. A systematic study was undertaken to determine the effect of shielding gas flow rate, as well as changes in the nozzle stand-off and angle, on the weld quality. The schlieren images were used to validate 2D and 3D magnetohydrodynamic (MHD) finite element models of the interaction between the Ar shielding gas, the arc and the ambient atmosphere. Weld porosity levels were determined through x-ray radiography. Sufficient shielding gas coverage was provided at a minimum of 9 l/min pure Ar, irrespective of relatively large increases in the nozzle stand-off and angle. Using 80% Ar/20% CO2 shielding gas, and 86% Ar/12% CO2/2% O2 shielding gas with flux cored arc welding (FCAW-G), achieved good quality welds down to 5 l/min. The introduction of 12 l/min in production welding has been implemented with no compromise in the weld quality and further reductions are feasible

Solid Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State H-1 Nuclear Spin Relaxation

Using solid state 1H nuclear magnetic resonance (NMR) spin-lattice relaxation experiments, we have investigated the effects of several solid-solid phase transitions on t-butyl group and methyl group rotation in solid 1,3,5-tri-t-butylbenzene. The goal is to relate the dynamics of the t-butyl groups and their constituent methyl groups to properties of the solid determined using single-crystal X-ray diffraction and differential scanning calorimetry (DSC). On cooling, the DSC experiments see a first-order, solid-solid phase transition at either 268 K or 155 K (but not both) depending on thermal history. The 155 K transition (on cooling) is identified by single-crystal X-ray diffraction to be one from a monoclinic phase (above 155 K) where the t-butyl groups are disordered (that is, with a rotational six-fold intermolecular potential dominating) to a triclinic phase (below 155 K) where the t-butyl groups are ordered (that is, with a rotational threefold intermolecular potential dominating). This transition shows very different DSC scans when both a 5 mg polycrystalline sample and a 19 mg powder sample are used. The 1H spin-lattice relaxation experiments with a much larger 0.7 g sample are very complicated and, depending on thermal history, can show hysteresis effects over many hours and over very large temperature ranges. In the high-temperature monoclinic phase, the t-butyl groups rotate with NMR activation energies (closely related to rotational barriers) in the 17-23 kJ mol-1 range and the constituent methyl groups rotate with NMR activation energies in the 7-12 kJ mol-1 range. In the lowtemperature triclinic phase, the rotations of the t-butyl groups and their methyl group in the aromatic plane are quenched (on the NMR time scale). The two out-of-plane methyl groups in the t-butyl groups are rotating with activation energies in the 5-11 kJ mol-1 range

Solid Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State H-1 Nuclear Spin Relaxation

Using solid state 1H nuclear magnetic resonance (NMR) spin-lattice relaxation experiments, we have investigated the effects of several solid-solid phase transitions on t-butyl group and methyl group rotation in solid 1,3,5-tri-t-butylbenzene. The goal is to relate the dynamics of the t-butyl groups and their constituent methyl groups to properties of the solid determined using single-crystal X-ray diffraction and differential scanning calorimetry (DSC). On cooling, the DSC experiments see a first-order, solid-solid phase transition at either 268 K or 155 K (but not both) depending on thermal history. The 155 K transition (on cooling) is identified by single-crystal X-ray diffraction to be one from a monoclinic phase (above 155 K) where the t-butyl groups are disordered (that is, with a rotational six-fold intermolecular potential dominating) to a triclinic phase (below 155 K) where the t-butyl groups are ordered (that is, with a rotational threefold intermolecular potential dominating). This transition shows very different DSC scans when both a 5 mg polycrystalline sample and a 19 mg powder sample are used. The 1H spin-lattice relaxation experiments with a much larger 0.7 g sample are very complicated and, depending on thermal history, can show hysteresis effects over many hours and over very large temperature ranges. In the high-temperature monoclinic phase, the t-butyl groups rotate with NMR activation energies (closely related to rotational barriers) in the 17-23 kJ mol-1 range and the constituent methyl groups rotate with NMR activation energies in the 7-12 kJ mol-1 range. In the lowtemperature triclinic phase, the rotations of the t-butyl groups and their methyl group in the aromatic plane are quenched (on the NMR time scale). The two out-of-plane methyl groups in the t-butyl groups are rotating with activation energies in the 5-11 kJ mol-1 range

Photogeneration of α‑Bimetalloid Radicals via Selective Activation of Multifunctional C1 Units

Light-driven strategies that enable the chemoselective activation of a specific bond in multifunctional systems are comparatively underexplored in comparison to transition-metal-based technologies, yet desirable when considering the controlled exploration of chemical space. With the current drive to discover next-generation therapeutics, reaction design that enables the strategic incorporation of an sp 3 carbon center, containing multiple synthetic handles for the subsequent exploration of chemical space would be highly enabling. Here, we describe the photoactivation of ambiphilic C1 units to generate α-bimetalloid radicals using only a Lewis base and light source to directly activate the C–I bond. Interception of these transient radicals with various SOMOphiles enables the rapid synthesis of organic scaffolds containing synthetic handles (B, Si, and Ge) for subsequent orthogonal activation. In-depth theoretical and mechanistic studies reveal the prominent role of 2,6-lutidine in forming a photoactive charge transfer complex and in stabilizing in situ generated iodine radicals, as well as the influential role of the boron p-orbital in the activation/weakening of the C–I bond. This simple and efficient methodology enabled expedient access to functionalized 3D frameworks that can be further derivatized using available technologies for C–B and C–Si bond activation

Deciphering interplay between Salmonella invasion effectors

Bacterial pathogens have evolved a specialized type III secretion system (T3SS) to translocate virulence effector proteins directly into eukaryotic target cells. Salmonellae deploy effectors that trigger localized actin reorganization to force their own entry into non-phagocytic host cells. Six effectors (SipC, SipA, SopE/2, SopB, SptP) can individually manipulate actin dynamics at the plasma membrane, which acts as a ‘signaling hub’ during Salmonella invasion. The extent of crosstalk between these spatially coincident effectors remains unknown. Here we describe trans and cis binary entry effector interplay (BENEFIT) screens that systematically examine functional associations between effectors following their delivery into the host cell. The results reveal extensive ordered synergistic and antagonistic relationships and their relative potency, and illuminate an unexpectedly sophisticated signaling network evolved through longstanding pathogen–host interaction

Solid state nuclear bromination with N-bromosuccinimide. Part 2. Experimental and theoretical studies of reactions with some substituted benzaldehydes

N-Bromosuccinimide reacts with aromatic aldehydes in the solid state to yield exclusively nuclear brominated products while a similar reaction in the solution phase produces a number of products under varied conditions. The reactivity and regioselectivity have been studied in terms of the energies of HOMO, HOMO–LUMO difference, reaction free energy, reaction conditions and crystal packing. Single crystal X-ray structural analysis of 3,4-dihydroxybenzaldehyde has been carried out. Crystal packing energies of some of the reactive and unreactive benzaldehydes indicate the importance of molecular bromine diffusion in the solid state

New Scores for the Assessment of Mitral Stenosis Using Real-Time Three-Dimensional Echocardiography

Nonsurgical management of patients with symptomatic mitral valve stenosis has been established as the therapeutic modality of choice for two decades. Catheter-based balloon dilation of the stenotic valvular area has been shown, at least, as effective as surgical interventions. Unfavorable results of catheter-based interventions are largely due to unfavorable morphology of the valve apparatus, particularly leaflets calcification and subvalvular apparatus involvement. A mitral valve score has been proposed in Boston, MA, about two decades ago, based on morphologic assessment of mitral valve apparatus by two-dimensional (2D) echocardiography to predict successful balloon dilation of the mitral valve. Several other scores have been developed in the following years in order to more successfully predict balloon dilatation outcome. However, all those scores were based on 2D echocardiography, which is limited by ability to distinguish calcification and subvalvular involvement. The introduction of new matrix-based ultrasound probe has allowed 3D echocardiography (3DE) to provide more detailed morphologic analysis of mitral valve apparatus including calcification and subvalvular involvement. Recently, a new 3DE scoring system has been proposed by our group, which represents an important leap into refinement of the use of echocardiography guiding mitral valve interventions