Vertical stratification of figs and fig-eaters in a Bornean lowland rain forest: how is the canopy different?

Fig trees (Ficus spp; Moraceae) are a common constituent of many tropical forests, where they produce figs that are eaten by a wide range of bird and mammal species. In our Bornean field site six Ficus seed dispersal guilds can be recognised, differentially attracting subsets of the frugivore community. Guild membership appears to be determined by figs' size, colour, crop size and height above ground, and frugivores' size, sensory and locomotory physiology and foraging height. Vertical stratification therefore appears to be an important determinant of fig and frugivore partitioning. The guild structure observed is discussed with respect to implications for seed dispersal and the differences between the canopy and understorey. Regarding figs eaten primarily by birds, larger fruit and crops can be found in the canopy where they are exposed to larger assemblages of potential frugivores than those presented in the understorey.     

Effects of external phosphorus supply on internal phosphorus concentration and the initiation,growth and exudation of cluster roots in Hakea prostrata R.Br.

The response of internal phosphorus concentration, cluster-root initiation, and growth and carboxylate exudation to different external P supplies was investigated in Hakea prostrata R.Br. using a split-root design. After removal of most of the taproot, equal amounts of laterals were allowed to grow in two separate pots fastened together at the top, so that the separate root halves could be exposed to different conditions. Plants were grown for 10 weeks in this system; one root half was supplied with 1 M P while the other halves were supplied with 0, 1, 25 or 75 M P. Higher concentrations of P supplied to one root half significantly increased the P concentration of those roots and in the shoots. The P concentrations in root halves supplied with 1 M P were invariably low, regardless of the P concentration supplied to the other root half. Cluster root initiation was completely suppressed on root halves supplied with 25 or 75 M P, whereas it continued on the other halves supplied with 1 M P indicating that cluster-root initiation was regulated by local root P concentration. Cluster-root growth (dry mass increment) on root halves supplied with 1 M P was significantly reduced when the other half was either deprived of P or supplied with 25 or 75 M P. Cluster-root growth was favoured by a low shoot P status at a root P supply that was adequate for increased growth of roots and shoots without increased tissue P concentrations. The differences in cluster-root growth on root halves with the same P supply suggest that decreased cluster-root growth was systemically regulated. Carboxylate-exudation rates from cluster roots on root halves supplied with 1 M P were the same, whether the other root half was supplied with 1, 25 or 75 M P, but were approximately 30 times faster when the other half was deprived of P. Estimates of root P-uptake rates suggest a rather limited capacity for down-regulating P uptake when phosphate was readily available.     

Evaluation of environmental conditions for production of bacteriocin-like substance by <Emphasis Type="Italic">Bacillus</Emphasis> sp. strain P34

The influence of temperature, pH and media on bacteriocin production by Bacillus sp. P34 was investigated. The effect of temperature and initial pH was evaluated by factorial design and response surface methodology (RSM). Statistical analysis of results showed that, in the range studied, the two variables have a significant effect on bacteriocin production. Response-surface data showed maximum antimicrobial activity production at initial pH values between 6.0 and 8.0 and temperatures between 25 and 37 °C. No relationship between bacterial growth and bacteriocin production was observed. RSM proved to be a powerful tool in optimizing the production of antimicrobial activity by Bacillus sp. P34. When different media were tested, maximum bacteriocin production was observed in soybean protein-based medium, but antimicrobial activity was not achieved by cultivation on fish meal, feather meal, whey and grape waste.     

Structural signatures of enzyme binding pockets from order-independent surface alignment: a study of metalloendopeptidase and NAD binding proteins

Detecting similarities between local binding surfaces can facilitate identification of enzyme binding sites and prediction of enzyme functions, and aid in our understanding of enzyme mechanisms. Constructing a template of local surface characteristics for a specific enzyme function or binding activity is a challenging task, as the size and shape of the binding surfaces of a biochemical function often vary. Here we introduce the concept of signature binding pockets, which captures information on preserved and varied atomic positions at multiresolution levels. For proteins with complex enzyme binding and activity, multiple signatures arise naturally in our model, forming a signature basis set that characterizes this class of proteins. Both signatures and signature basis sets can be automatically constructed by a method called SOLAR (Signature Of Local Active Regions). This method is based on a sequence-order-independent alignment of computed binding surface pockets. SOLAR also provides a structure-based multiple sequence fragment alignment to facilitate the interpretation of computed signatures. By studying a family of evolutionarily related proteins, we show that for metzincin metalloendopeptidase, which has a broad spectrum of substrate binding, signature and basis set pockets can be used to discriminate metzincins from other enzymes, to predict the subclass of metzincins functions, and to identify specific binding surfaces. Studying unrelated proteins that have evolved to bind to the same NAD cofactor, we constructed signatures of NAD binding pockets and used them to predict NAD binding proteins and to locate NAD binding pockets. By measuring preservation ratio and location variation, our method can identify residues and atoms that are important for binding affinity and specificity. In both cases, we show that signatures and signature basis set reveal significant biological insight.     

The Role of Voluntary Industry Standards in Environmental Supply-Chain Management

Our article uses a new institutional economics (NIE) framework to explore the role of voluntary industry standards in the development and implementation of environmental supplier-management programs in the computer industry. We examine two different voluntary standards, one for the management of design for environment (DfE) in the semiconductor fabrication equipment sector and the other for assessing the implementation and use of environmental management systems throughout the computer industry supply chain. We compare and contrast the two standards to explain why the former was widely adopted and has helped integrate DfE into buyer-supplier relations among adopters, whereas the latter failed to gain acceptance. In line with NIE logic, both standards aimed to lower transaction and customization costs by setting "rules of the game" for interfirm transactions that would help simplify and routinize novel environmental supply-chain programs and activities. Their differential success can be elucidated in terms of how well each met the NIE criteria for remediableness and legitimacy. We conclude that voluntary standards have the potential to play an important role in promoting DfE in industrial supply chains. We further conclude that NIE provides a conceptual framework of great value to industrial ecologists who analyze how industry standards and other institutions help firms move toward more sustainable supply-chain management practices.     

Long-distance magnetic coupling in dinuclear copper(II) complexes with oligo-para-phenylenediamine bridging ligands

Two novel dinuclear copper(II) complexes of formulae [Cu₂(tren)₂(bpda)](ClO₄)₄ (2) and [Cu₂(tren)₂(tpda)](ClO₄)₄ (3) containing the tripodal tris(2-aminoethyl)amine (tren) terminal ligand and the 4,4′-biphenylenediamine (bpda) and 4,4″-p-terphenylenediamine (tpda) bridging ligands have been synthesized and structurally, spectroscopically, and magnetically characterized. Their experimentally available electronic spectroscopic and magnetic properties have been reasonably reproduced by DFT and TDDFT calculations. Single crystal X-ray diffraction analysis of 2 shows the presence of dicopper(II) cations where the bpda bridging ligand adopts a bismonodentate coordination mode toward two [Cu(tren)]²⁺ units with an overall non-planar, orthogonal anti configuration of the N-Cu-N threefold axis of the trigonal bipyramidal Cu^II ions and the biphenylene group. The electronic absorption spectra of 2 and 3 in acetonitrile reveal the presence of four moderately weak d-d transitions characteristic of a slightly distorted trigonal bipyramid stereochemistry of the Cu^II ions. TDDFT calculations on 2 identify these transitions as those taking place between the four lower-lying, doubly occupied a₂ (d_yz)², b₂ (d_xz)², b₁ (d_xy)², and a₁ (d_x²-y²)² orbitals and the upper, singly occupied a₁ (d_z²)¹ orbital of each trigonal bipyramidal Cu^II ion. Variable-temperature magnetic susceptibility measurements of 2 and 3 show the occurrence of moderate (J = −8.5 cm⁻¹) to weak intramolecular antiferromagnetic couplings (J = −2.0 cm^-1) [H = −JS₁·S₂ with S₁ = S₂ = S_Cu = ½] inspite of the relatively large copper-copper separation across the para-substituted biphenylene- (r = 12.3 Å) and terphenylenediamine (r = 16.4 Å) bridges, respectively. DFT calculations on 2 and 3 support the occurrence of a spin polarization mechanism for the propagation of the exchange interaction between the two unpaired electrons occupying the d_z² orbital of each trigonal bipyramidal Cu^II ion through the predominantly π-type orbital pathway of the oligo-p-phenylenediamine bridges, as reported earlier for the parent compound [Cu₂(tren)₂(ppda)](ClO₄)₄·2H₂O (1) with the 1,4-phenylenediamine (ppda) bridging ligand. Finally, a rather slow exponential decay of the antiferromagnetic coupling (-J) with the number of phenylene repeat units, -(C₆H₄)_n- (n = 1-3), has been found both experimentally and theoretically along this series of oligo-p-phenylenediamine-bridged dicopper(II) complexes. These results further support the ability of linear π-conjugated oligo-p-phenylene spacers to transmit the exchange interaction between the unpaired electrons of the two Cu^II centers with intermetallic distances in the range of 7.5-16.4 Å.