Persistence and stochasticity are key determinants of genetic diversity in plants associated with banded iron formation inselbergs

The high species endemism characteristic of many of the world's terrestrial island systems provides a model for studying evolutionary patterns and processes, yet there has been no synthesis of studies to provide a systematic evaluation of terrestrial island systems in this context. The banded iron formations (BIFs) of south‐western Australia are ancient terrestrial island formations occurring within a mosaic of alluvial clay soils, sandplains and occasional granite outcropping, across an old, gently undulating, highly weathered, plateau. Notably, these BIFs display exceptionally high beta plant diversity. Here, we address the determinants and consequences of genetic diversity for BIF‐associated plant species through a comprehensive review of all studies on species distribution modelling, phylogenetics, phylogeography, population genetics, life‐history traits and ecology. The taxa studied are predominantly narrowly endemic to individual or a few BIF ranges, but some have more regional distributions occurring both on and off BIFs. We compared genetic data for these BIF‐endemic species to other localised species globally to assess whether the unique history and ancestry of BIF landscapes has driven distinct genetic responses in plants restricted to this habitat. We also assessed the influence of life‐history parameters on patterns of genetic diversity. We found that BIF‐endemic species display similar patterns of genetic diversity and structure to other species with localised distributions. Despite often highly restricted distributions, large effective population size or clonal reproduction appears to provide these BIF‐endemic species with ecological and evolutionary resilience to environmental stochasticity. We conclude that persistence and stochasticity are key determinants of genetic diversity and its spatial structure within BIF‐associated plant species, and that these are key evolutionary processes that should be considered in understanding the biogeography of inselbergs worldwide.     

A modified method for whole exome resequencing from minimal amounts of starting DNA

Next generation DNA sequencing (NGS) technologies have revolutionized the pace at which whole genome and exome sequences can be generated. However, despite these advances, many of the methods for targeted resequencing, such as the generation of high-depth exome sequences, are somewhat limited by the relatively large amounts of starting DNA that are normally required. In the case of tumour analysis this is particularly pertinent as many tumour biopsies often return submicrogram quantities of DNA, especially when tumours are microdissected prior to analysis. Here, we present a method for exome capture and resequencing using as little as 50 ng of starting DNA. The sequencing libraries generated by this minimal starting amount (MSA-Cap) method generate datasets that are comparable to standard amount (SA) whole exome libraries that use three micrograms of starting DNA. This method, which can be performed in most laboratories using commonly available reagents, has the potential to enhance large scale profiling efforts such as the resequencing of tumour exomes.     

First- and second-row transition metal oxa-aza macrocyclic complexes: a DFT study of an octahedral conformation

A theoretical study of structures of the 1,7,1 l,17-tetraoxa-2,6,12,16-tetraaza-cycloeicosane ligand ([20]AneN(4)O(4)) coordinated to Fe(2+), Co(2+), Ni(2+), Ru(2+), Rh(2+), and Pd(2+) transition metals ions was carried out with the DFT/B3LYP method. Complexes were fully optimized in C(s) symmetry with the metal ions coordinated either to nitrogen (1a) or oxygen atoms (1b). For all the cases performed in this work, 1a was always more stable than 1b. Considering each row it is possible to see that the binding energy increases with the atomic number. The M(2+) cation binding energies increase in the following order: Fe(2+)相似文献   

Studies toward the structural optimization of new brazilizone-related trypanocidal 1,3,4-thiadiazole-2-arylhydrazone derivatives

Megazol is a highly active compound against Trypanosoma cruzi, and has become a core structure for the design of new trypanocidal agents. Recently, we have identified the new potent trypanocide agent Brazilizone A, which presents an IC(50) twofold more potent than the prototype megazol. This result has encouraged us to further explore structurally-related 1,3,4-thiadiazole-2-arylhydrazone derivatives, in order to get a better understanding of their structural and antiprotozoal activity relationships. Herein we report the synthesis and trypanocidal profile of thirteen new Brazilizone A analogues, which supported the construction of 3D-QSAR models used for its structural optimization.     

The use of PNAs and their derivatives in mitochondrial gene therapy

Human mitochondria contain their own genome, mtDNA. This small molecule encodes 24 RNA species and 13 polypeptides, which are essential components of the mitochondrial respiratory chain. The mitochondrial genome is present in hundreds or thousands of copies in each cell and is believed to turnover throughout the life of the cell. Defects of the mitochondrial genome (mtDNA) cause a variety of multisystemic disorders routinely affecting the muscle and nervous system. There is currently no effective treatment for patients with defects of the mitochondrial genome. In many patients, defective cells harbour two sub-populations of mtDNA (a situation termed heteroplasmy), one being normal, the other containing the pathogenic mutation. The mutated copy is often recessive, with biochemical and clinical defects only becoming apparent when the levels of mutated mtDNA outweigh the normal copies. It has therefore been postulated that by selectively preventing replication of the mutated mtDNA, the normal copy will propagate, restoring biochemical function. The search has therefore been on during recent years to identify an antigenomic molecule that will fulfil this criterion. Following evidence that peptide nucleic acids could selectively inhibit replication of templates carrying a known pathogenic mtDNA mutation in vitro,we report on the progress of this approach and the various modificationsthat are now being used to improve the efficacy of PNA-based antigenomic inhibition.     

Phylogeny and systematics of the bee genus Osmia (Hymenoptera: Megachilidae) with emphasis on North American Melanosmia: subgenera,synonymies and nesting biology revisited

The predominantly Holarctic bee genus Osmia Panzer is species‐rich and behaviourally diverse. A robust phylogeny of this genus is important for understanding the evolution of the immense variety of morphological and behavioural traits exhibited by this group. We infer a phylogeny of Osmia using DNA sequence data obtained from three nuclear genes (elongation factor 1‐α, LW‐rhodopsin and CAD) and the mitochondrial gene COI. Our taxon sampling places special attention on North American members of the subgenus Melanosmia Schmiedeknecht; we discuss the novel placement of a number of species traditionally assigned to O. (Melanosmia) and examine the relative support for alternative classifications of this species‐rich subgenus. We use this new phylogeny to guide a reassessment of morphological and behavioural characters within Osmia. Our results provide support for the recognition of Osmia (Hapsidosmia), subgen.n ., a monotypic subgenus containing Osmia iridis Cockerell & Titus. We synonymize Osmia (Mystacosmia) Snelling under O. (Melanosmia), syn.n . We synonymize Osmia (Acanthosmioides) Ashmead under O. (Melanosmia), syn.n ., propose ‘odontogaster species group’ as a replacement for the subgeneric name Acanthosmioides, and refine the morphological characters that serve to diagnose the species group. We additionally propose ‘nigrifrons species group’ for a clade within O. (Melanosmia) containing most species formerly placed in Osmia (Centrosmia) Robertson. We demonstrate more cohesive patterns of nest substrate use in the nigrifrons and odontogaster species groups than was previously believed to occur, reconsider character polarity of aspects of the female mandible, and show that a large number of morphological characters have evolved convergently within the genus. In order to facilitate discussion of relevant taxa, we propose the following 15 new synonymies: O. bakeri Sandhouse under O. melanopleura Cockerell; O. crenulaticornis Michener under O. pinorum Cockerell; O. claremontensis Michener under O. sedula Sandhouse; O. cockerelli Sandhouse under O. dakotensis Michener; O. francisconis White under O. enixa Sandhouse; O. hurdi White under O. austromaritima Michener; O. sladeni Sandhouse under O. nifoata Cockerell; O. titusi Cockerell under O. phenax Cockerell; O. subtrevoris Cockerell, O. physariae Cockerell, and O. erecta Michener under O. giliarum Cockerell; and O. universitatis Cockerell, O. integrella Cockerell, O. amala Cockerell, and O. metitia Cockerell under O. nigrifrons Cresson, syn.n . We remove O. wyomingensis Michener from synonymy with O. nifoata Cockerell, stat.n ., and O. pinorum Cockerell from synonymy with O. physariae Cockerell, stat.n . This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:A3E7D63B‐5C4C‐4ACF‐BF33‐48E5C5DD1B0D .     

Ashes to ashes: Intense fires extinguish populations of urban short‐range endemics

Native bushland fragmented by urbanization often experiences increased cover of flammable weeds, reduced biomass turnover and an absence of fuel management combined with increased ignitions. Depending on species’ mobility and dispersal traits, and the extent of burns within urban remnants, such fires may reduce individual survival rates or limit natural recolonization. We monitored the survival of mygalomorph spiders for a year following high‐intensity and low‐intensity fires in Banksia woodland remnants in urban Perth. Of the 257 burrows found, 115 spiders were confirmed to initially survive after intense wildfire, but none were confirmed alive after 12 months. In sharp contrast, only one spider from 103 observed burrows was confirmed dead after a low‐intensity prescribed fire. As there were instances of our monitored mygalomorphs relocating a short distance following only low intensity fires, we also tested whether predation rates were higher in burnt than unburnt areas. Higher rates of predation were found in burnt areas, but this was strongly influenced by both site and predator type. We recommend further consideration of low‐intensity prescribed fire as well as alternative fuel management approaches in urban remnants to better conserve mygalomorph spider populations and other taxa with limited dispersal and/or mobility capabilities.     

Endogenous chloride channels of insect sf9 cells. Evidence for coordinated activity of small elementary channel units

The endogenous Cl- conductance of Spodoptera frugiperda (Sf9) cells was studied 20-35 h after plating out of either uninfected cells or cells infected by a baculovirus vector carrying the cloned beta-galactosidase gene (beta-Gal cells). With the cation Tris+ in the pipette and Na+ in the bath, the reversal potential of whole-cell currents was governed by the prevailing Cl- equilibrium potential and could be fitted by the Goldman-Hodgkin-Katz equation with similar permeabilities for uninfected and beta-Gal cells. In the frequency range 0.12 < f < 300 Hz, the power density spectrum of whole-cell Cl- currents could be fitted by three Lorentzians. Independent of membrane potential, >50% of the total variance of whole-cell current fluctuations was accounted for by the low frequency Lorentzian (fc = 0.40 +/- 0.03 Hz, n = 6). Single-Cl- channels showed complex gating kinetics with long lasting (seconds) openings interrupted by similar long closures. In the open state, channels exhibited fast burst-like closures. Since the patches normally contained more than a single channel, it was not possible to measure open and closed dwell-time distributions for comparing single-Cl- channel activity with the kinetic features of whole-cell currents. However, the power density spectrum of Cl- currents of cell-attached and excised outside-out patches contained both high and low frequency Lorentzian components, with the corner frequency of the slow component (fc = 0.40 +/- 0.02 Hz, n = 4) similar to that of whole-cell current fluctuations. Chloride channels exhibited multiple conductance states with similar Goldman-Hodgkin-Katz-type rectification. Single-channel permeabilities covered the range from approximately 0.6.10(-14) cm5/s to approximately 6.10(-14) cm3/s, corresponding to a limiting conductance (gamma 150/150) of approximately 3.5 pS and approximately 35 pS, respectively. All states reversed near the same membrane potential, and they exhibited similar halide ion selectivity, P1 > PCl approximately PBr. Accordingly, Cl- current amplitudes larger than current flow through the smallest channel unit resolved seem to result from simultaneous open/shut events of two or more channel units.     

The probability of obtaining complex kinetic curves for enzyme mechanisms with cubic terms in the pseudo-steady state rate equations

A number of details required for the classification of 3 : 3 double reciprocal plots are provided. It is shown that the ν(S) plot for a 3 : 3 function can have at most four inflexions and at most two inflexions adjacent to a turning point. Using this information, a classification of 3 : 3 ν(S) plots into ten main varieties with several subclasses is reported. The problem of defining the probability with which a given mechanism can give rise to specific curve shape features is considered. Applying this technique, the probability with which four simple enzyme mechanisms can give rise to 3 : 3 curve shapes is computed. It is shown that a 3 : 3 saturation function can have no turning points, at most two inflexions and at most one inflexion in double reciprocal space. The probability with which the available 3 : 3 shapes can arise is also computed. It is concluded that, with realistic values for rate constants, chemically reasonable enzyme mechanisms leading to rate equations of degree n : n can generate most of the kinetic profiles available to a rational function of degree n : n with positive coefficients. The probability of obtaining specific curve shapes is not so characteristic of the particular mechanism for 3:3 rate equations as it is for 2:2 rate equations. The probability of obtaining highly complex curves with several turning points or inflexions is rather lower for the enzyme mechanisms than with general 3 : 3 rational functions. There is a high probability that 3 : 3 mechanisms will generate kinetic curves that are geometrically similar to those possible for degree 2 : 2 but this is not so for binding isotherms. Hence differentiating 3 : 3 from 2 : 2 rate equations from experimental kinetic data is more likely to be successful by non-linear regression to the whole data set than by demonstrating a specific 3 : 3 feature. Binding curves, on the other hand, for three or more sites should give Scatchard plots with inflexions, features not possible with second degree equations which are conic sections in this space.