Structure of 5-Bromo-2',3'-O-isopropylideneuridine, C12H15BrN206

Mr= 363.17, orthorhombic, P21212 ~, a= 5.251(4), b=14.962(5), c=19.112(5)A, U= 1501.41/k 3, Z=4, Dx=1.61Mgm -3, /t(CuKa)= 3.02 mm -1, 2(Cu Ka)= 1.5418/~, final R = 7.0% for 1091 reflections with Fo> 2e(Fo). The glycosidic torsion angle ZCN is 13"1 (12) °. The ribose has a C (3')-exo,C (4)-endo twist geometry. The dioxolane ring assumes an envelope conformation with 0(3') displaced by 0.453 (10)/k from the plane of the other four atoms. The conformation about the C(4')-C(5') bond is gauche-gauche. The structure is stabilized by two hydrogen bonds between screw-axis-related molecules. The crystal packing and the conformation of the molecule are very similar to those found in the structure of 2',3'-O-isopropylideneuridine which lacks the Br atom at the 5-position.

First hyperpolarizability of bacteriorhodopsin, retinal and related molecules revisited

The previously reported beta values of BR and retinal based chromophores were very high but subsequent measurements found them to be much less. We have found that the beta values of these compounds do not vary so much with experimental conditions as with the method of analysis. Hyper-Rayleigh scattering measurements at 1543 and 1907 nm produce more realistic beta values close to the intrinsic (static) hyperpolarizability, beta(0) which for BR is still very high (275 x 10 (30) esu). The optical nonlinearity of BR arises entirely due to the protonated retinal Schiff Base (PRSB) which in its isolated form has the same intrinsic hyperpolarizability as that of the rotein.

Seasonal resource availability and use by an endangered tropical mycophagous marsupial

This study highlights the importance of considering how seasonality of rainfall affects availability of resources and consequently species distributions within tropical ecosystems. The endangered northern bettong, Bettongia tropica Wakefield is thought to be restricted to habitats where seasonal availability of hypogeous fungi, their principal food resource, remains high. To test this hypothesis fungal abundance was quantified in the early wet, late wet, early dry and late dry seasons within known bettong habitat. A relationship was found between precipitation and fungal availability, with the abundance of hypogeous fungi being significantly lower in the late dry season. Fungal availability correlated strongly with the seasonal rainfall pattern determined from 74-year monthly means. This contrasts with a previous study where mycophagy, measured by faecal analysis, remained high across seasons presumably because of aseasonal rainfall during that study period. Alloteropsis semialata R.Br. (cockatoo grass) use by bettongs increased significantly during the period of low fungal availability. This suggests that the importance of cockatoo grass as an alternative food resource during annual and extended dry periods has previously been underestimated. With the frequency and intensity of drought expected to increase with global climate change, these findings have significant implications for bettong management. The important and possibly equivalent dependence of B. tropica on both hypogeous fungi and A. semialata helps to explain their habitat preference and identifies this species as a true ecotonal specialist.

Reactivities of tetrahalosilanes and silane with sulphur trioxide

Reactions of tetrahalosilanes [SiX4 (X= F, Cl or Br)] and silane (SiH4) with sulphur trioxide (SO3) have been studied under different experimental conditions. Each of the silanes behaves differently in accordance with the bond energy of the Si—X bond. While SiF4 remains unreactive even at 600°C, SiCl4 reacts with SO3 at 500°C giving rise to hexachlorodisiloxane [(SiCl3)2O] as the major product. In contrast SiBr4 and SiH4 react with SO3 at room temperature and below room temperature, respectively, yielding silica as one of the products of reaction. In all cases the SO3 is reduced to sulphur dioxide.

Effect of microwave radiation on seed mortality of rubber vine (Cryptostegia grandiflora R.Br.), parthenium (Parthenium hysterophorous L.) and bellyache bush (Jatropha gossypiifolia L.)

A trial was undertaken to evaluate the effect of microwaves on seed mortality of three weed species. Seeds of rubber vine (Cryptostegia grandiflora R.Br.), parthenium (Parthenium hysterophorous L.) and bellyache bush (Jatropha gossypiifolia L.) were buried at six depths (0, 2.5, 5, 10, 20 and 40 cm) in coarse sand maintained at one of two moisture levels, oven dry or wet (field capacity), and then subjected to one of five microwave radiation durations of (0, 2, 4, 8 and 16 min). Significant interactions between soil moisture level, microwave radiation duration, seed burial depth and species were detected for mortality of seeds of all three species. Maximum seed mortality of rubber vine (88%), parthenium (67%) and bellyache bush (94%) occurred in wet soil irradiated for 16 min. Maximum seed mortality of rubber vine and bellyache bush seeds occurred in seeds buried at 2.5 cm depth whereas that of parthenium occurred in seeds buried at 10 cm depth. Maximum soil temperatures of 114.1 and 87.5°C in dry and wet soil respectively occurred at 2.5 cm depth following 16 min irradiation. Irrespective of the greater soil temperatures recorded in dry soil, irradiating seeds in wet soil generally increased seed mortality 2.9-fold compared with dry soil. Moisture content of wet soil averaged 5.7% compared with 0.1% for dry soil. Results suggest that microwave radiation has the potential to kill seeds located in the soil seed bank. However, many factors, including weed species susceptibility, determine the effectiveness of microwave radiation on buried seeds. Microwave radiation may be an alternative to conventional methods at rapidly depleting soil seed banks in the field, particularly in relatively wet soils that contain long lived weed seeds.

New microsatellite loci for Carcharhinid sharks (Carcharhinus tilstoni and C. sorrah) and their cross-amplification in other shark species

Twelve microsatellite DNA markers were isolated in the spot-tail shark (Carcharhinus sorrah) and nine were isolated in Australian black-tip shark (Carcharhinus tilstoni). These loci plus 18 others developed for sharks from the genera Negaprion, Ginglymostoma, Carcharodon and Isurus were tested for amplification success on four species of Carcharhinus (including C. sorrah and C. tilstoni) and four other species representing three diverse families. Cross-amplification was most common within families. Five loci were subsequently tested for polymorphism on 50 C. sorrah and 60 C. tilstoni. The number of alleles per locus was two to 24 and the average heterozygosity was 0.54 (range 0.16-0.87) for C. sorrah and 0.64 (range 0.44-0.78) for C. tilstoni. These loci may be useful tools for genetic analyses of the Carcharhinidae.

The introduction and release of Chiasmia inconspicua and C. assimilis (Lepidoptera: Geometridae) for the biological control of Acacia nilotica in Australia

Two geometrid moths Chiasmia inconspicua and Chiasmia assimilis, identified as potential biological control agents for prickly acacia Acacia nilotica subsp. indica, were collected in Kenya and imported into quarantine facilities in Australia where laboratory cultures were established. Aspects of the biologies of both insects were studied and CLIMEX® models indicating the climatically favourable areas of Australia were developed. Host range tests were conducted using an approved test list of 74 plant species and no-choice tests of neonate larvae placed on both cut foliage and potted plants. C. inconspicua developed through to adult on prickly acacia and, in small numbers, Acacia pulchella. C. assimilis developed through to adult on prickly acacia and also in very small numbers on A. pulchella, A. deanei, A. decurrens, and A. mearnsii. In all experiments, the response on prickly acacia could be clearly differentiated from the responses on the non-target species. Both insects were approved for release in Australia. Over a three-year period releases were made at multiple sites in north Queensland, almost all in inland areas. There was no evidence of either insect's establishment and both colonies were terminated. A new colony of C. assimilis was subsequently established from insects collected in South Africa and releases of C. assimilis from this new colony were made into coastal and inland infestations of prickly acacia. Establishment was rapid at one coastal site and the insect quickly spread to other infestations. Establishment at one inland area was also confirmed in early 2006. The establishment in coastal areas supported a CLIMEX model that indicated that the climate of coastal areas was more suitable than inland areas.

Performance of seven hardwood species underplanted to Pinus elliottii in south-east Queensland

Seven hardwood species were tested as underplants under Pinus elliottii plantations on the coastal lowlands of south-east Queensland. The species tested were: Flindersia brayleyana (F. Muell) (Queensland maple), F. australis (R. Br.), (crow's ash), Swietenia macrophylla (King) (American mahogany), Grevillea robusta (A. cunn) (southern silky oak), Elaeocarpus grandis (F. Muell) (silver quandong), F. ifflaiana (F. Meull) (Cairns hickory) and Ceratopetalum apetalum (D. Don) (coachwood). Most species (except E. grandis) established successfully but slowly. Underplants suffered 9-16% mortality during thinning of the overstorey. By 2004 when aged c. 38 years, four underplanted species; F. brayleyana, S. macrophylla, F. ifflaiana and E. grandis, had attained predominant heights of 20 m and mean diameter at breast height of 25 cm or better. The presence of underplants increased total site productivity by up to 23% and did not have any detrimental effect on the development of the overwood.This experiment has demonstrated that some rainforest species will survive and grow healthily as underplants in exotic pine plantations plus produce small merchantable logs within a 38 year rotation. The results also indicated the importance of correct species selection if an underplanting option is to be pursued as some species have been a complete failure (notably G. robusta).

Retrogressed eclogite (20 kbar, 1020 °C) from the Neoproterozoic Palghat–Cauvery suture zone, southern India

The Palghat–Cauvery suture zone in southern India separates Archaean crustal blocks to the north and the Proterozoic Madurai block to the south. Here we present the first detailed study of a partially retrogressed eclogite (from within the Sittampundi anorthositic complex in the suture zone) that occurs as a 20-cm wide layer in a garnet gabbro layer in anorthosite. The eclogite largely consists of an assemblage of coexisting porphyroblasts of almandine–pyrope garnet and augitic clinopyroxene. However, a few garnets contain inclusions of omphacite. Rims and symplectites composed of Na–Ca amphibole and plagioclase form a retrograde assemblage. Petrographic analysis and calculated phase equilibria indicate that garnet–omphacite–rutile–melt was the peak metamorphic assemblage and that it formed at ca. 20 kbar and above 1000 °C. The eclogite was exhumed on a very tight hairpin-type, anticlockwise P–T path, which we relate to subduction and exhumation in the Palghat–Cauvery suture zone. The REE composition of the minerals suggests a basaltic oceanic crustal protolith metamorphosed in a subduction regime. Geological–structural relations combined with geophysical data from the Palghat–Cauvery suture zone suggest that the eclogite facies metamorphism was related to formation of the suture zone. Closure of the Mozambique Ocean led to development of the suture zone and to its western extension in the Betsimisaraka suture of Madagascar.

Biosynthesis of cytoplasmic subunits of cytochrome C oxidase in rat liver

The biosynthesis of the cytoplasmic subunits of cytochrome oxidase from rat liver has been studied in vitro by translating liver poly (A)-containing RNA in the wheat germ cell-free system and immunoprecipitating the products with anti-cytochrome oxidase antibody. Analysis of the labelled immunoprecipitate on SDS-gels does not reveal the presence of a polyprotein precursor. On the other hand discrete products which are either slightly bigger or closely similar to the mature subunits present in purified cytochrome oxidase have been detected.

Central America: Labor Reports and Child Labor Reports Pursuant to the Trade Act of 2002, Section 2102(c)(8)-(9)

[Excerpt] These comments are in response to the “Request for Information Concerning Labor Rights in Costa Rica, El Salvador, Guatemala, Honduras and Nicaragua and their Laws Governing Exploitative Child Labor” published at 68 Fed. Reg. 19580 (April 21, 2003). This Request for Information was issued pursuant to Section 2102(c)(8) and (9) of the Trade Act of 2002, Pub. L. 107-210, which requires the President, with respect to any proposed trade agreement, to submit to Congress a “meaningful labor rights report” and a “report describing the extent to which the country or countries that are parties to the agreement have in effect laws governing exploitative child labor.”

The structures of the ammonium halides

A comparison with the alkali halides suggests that all the ammonium halides should occur in the NaCl centre-of-mass structure. Experimentally, at room temperature and atmospheric pressure, only NH,1 crystallizes in this structure, while NH,F is found in the ZnO structure, and NH&I and NH,Br occur in the CsCl structure. We show that a distributed charge on the NH,+ ion can explain these structures. Taking charges of + 0.2e on each of the five atoms in NH,+, as suggested by other studies, we have recomputed the Madelung energy in the cases of interest. A full ionic theory including electrostatic, van der Waals and repulsive interactions then explains the centre-of-mass structures of all the four ammonium halides. The thermal and pressure transitions are also explained reasonably well. The calculated phase diagram of NH,F compares well with experiment. Barring the poorly understood NH,F(II) phase, which is beyond the scope of this work, the other features are in qualitative agreement. In particular, the theory correctly predicts a pressure transition at room temperature from the ZnO structure directly to the CsCl structure without an intermediate NaCl phase. A feature of our approach is that we do not need to invoke hydrogen bonding in NH,F.

Sequence-dependent conformation of an A-DNA double helix: The crystal structure of the octamer d(G-G-T-A-T-A-C-C)

The crystal structures of the synthetic self-complementary octamer d(G-G-T-A-T-A-C-C) and its 5-bromouracil-containing analogue have been refined to R values of 20% and 14% at resolutions of 1·8 and 2·25 Å, respectively. The molecules adopt an A-DNA type double-helical conformation, which is minimally affected by crystal forces. A detailed analysis of the structure shows a considerable influence of the nucleotide sequence on the base-pair stacking patterns. In particular, the electrostatic stacking interactions between adjacent guanine and thymine bases produce symmetric bending of the double helix and a major-groove widening. The sugar-phosphate backbone appears to be only slightly affected by the base sequence. The local variations in the base-pair orientation are brought about by correlated adjustments in the backbone torsion angles and the glycosidic orientation. Sequence-dependent conformational variations of the type observed here may contribute to the specificity of certain protein-DNA interactions.