Quantum dynamics of rovibrational transitions in H2-H2 collisions: internal energy and rotational angular momentum conservation effects.

We present a full dimensional quantum mechanical treatment of collisions between two H(2) molecules over a wide range of energies. Elastic and state-to-state inelastic cross sections for ortho-H(2) + para-H(2) and ortho-H(2) + ortho-H(2) collisions have been computed for different initial rovibrational levels of the molecules. For rovibrationally excited molecules, it has been found that state-to-state transitions are highly specific. Inelastic collisions that conserve the total rotational angular momentum of the diatoms and that involve small changes in the internal energy are found to be highly efficient. The effectiveness of these quasiresonant processes increases with decreasing collision energy and they become highly state-selective at ultracold temperatures. They are found to be more dominant for rotational energy exchange than for vibrational transitions. For non-reactive collisions between ortho- and para-H(2) molecules for which rotational energy exchange is forbidden, the quasiresonant mechanism involves a purely vibrational energy transfer albeit with less efficiency. When inelastic collisions are dominated by a quasiresonant transition calculations using a reduced basis set involving only the quasiresonant channels yield nearly identical results as the full basis set calculation leading to dramatic savings in computational cost.

Full-dimensional quantum dynamics calculations of H(2)-H(2) collisions.

We report quantum dynamics calculations of rotational and vibrational energy transfer in collisions between two para-H(2) molecules over collision energies spanning from the ultracold limit to thermal energies. Results obtained using a recent full-dimensional H(2)-H(2) potential energy surface (PES) developed by Hinde [J. Chem. Phys. 128, 154308 (2008)] are compared with those derived from the Boothroyd, Martin, Keogh, and Peterson (BMKP) PES [J. Chem. Phys. 116, 666 (2002)]. For vibrational relaxation of H(2)(v=1,j=0) by collisions with H(2)(v=0,j=0) as well as rotational excitations in collisions between ground state H(2) molecules, the PES of Hinde is found to yield results in better agreement with available experimental data. A highly efficient near-resonant energy transfer mechanism that conserves internal rotational angular momentum and was identified in our previous study of the H(2)-H(2) system [Phys. Rev. A 77, 030704(R) (2008)] using the BMKP PES is also found to be reproduced by the Hinde PES, demonstrating that the process is largely insensitive to the details of the PES. In the absence of the near-resonance mechanism, vibrational relaxation is driven by the anisotropy of the potential energy surface. Based on a comparison of results obtained using the Hinde and BMKP PESs with available experimental data, it appears that the Hinde PES provides a more accurate description of rotational and vibrational transitions in H(2)-H(2) collisions, at least for vibrational quantum numbers v ≤ 1.

Atomic spectral-product representations of molecular electronic structure: metric matrices and atomic-product composition of molecular eigenfunctions.

Recent progress is reported in development of ab initio computational methods for the electronic structures of molecules employing the many-electron eigenstates of constituent atoms in spectral-product forms. The approach provides a universal atomic-product description of the electronic structure of matter as an alternative to more commonly employed valence-bond- or molecular-orbital-based representations. The Hamiltonian matrix in this representation is seen to comprise a sum over atomic energies and a pairwise sum over Coulombic interaction terms that depend only on the separations of the individual atomic pairs. Overall electron antisymmetry can be enforced by unitary transformation when appropriate, rather than as a possibly encumbering or unnecessary global constraint. The matrix representative of the antisymmetrizer in the spectral-product basis, which is equivalent to the metric matrix of the corresponding explicitly antisymmetric basis, provides the required transformation to antisymmetric or linearly independent states after Hamiltonian evaluation. Particular attention is focused in the present report on properties of the metric matrix and on the atomic-product compositions of molecular eigenstates as described in the spectral-product representations. Illustrative calculations are reported for simple but prototypically important diatomic (H(2), CH) and triatomic (H(3), CH(2)) molecules employing algorithms and computer codes devised recently for this purpose. This particular implementation of the approach combines Slater-orbital-based one- and two-electron integral evaluations, valence-bond constructions of standard tableau functions and matrices, and transformations to atomic eigenstate-product representations. The calculated metric matrices and corresponding potential energy surfaces obtained in this way elucidate a number of aspects of the spectral-product development, including the nature of closure in the representation, the general redundancy or linear dependence of its explicitly antisymmetrized form, the convergence of the apparently disparate atomic-product and explicitly antisymmetrized atomic-product forms to a common invariant subspace, and the nature of a chemical bonding descriptor provided by the atomic-product compositions of molecular eigenstates. Concluding remarks indicate additional studies in progress and the prognosis for performing atomic spectral-product calculations more generally and efficiently.

Direct observation of H2 binding to a metal oxide surface.

Inelastic neutron scattering is used to probe the dynamical response of H2 films adsorbed on MgO(100) as a function of film thickness. Concomitant diffraction measurements and a reduced-dimensionality quantum dynamical model provide insight into the molecule-surface interaction potential. At monolayer thickness, the rotational motion is strongly influenced by the surface, so that the molecules behave like quasiplanar rotors. These findings have a direct impact on understanding how molecular hydrogen binds to the surface of materials used in catalytic and storage applications.

Separation of two cell signalling molecules from a symbiotic sponge that modify algal carbon metabolism.

Two distinct cell signals have been isolated from the sponge host of the tropical sponge/macroalga symbiotic association Haliclona cymiformis/Ceratodictyon spongiosum. These water soluble cell signals (M(r) between 500 and 1000) modify separate steps in the carbon metabolism in both C. spongiosum and the microalga, Symbiodinium from the coral Plesiastrea versipora. The first signal, host release factor (HRF), stimulates the release of compounds derived from algal photosynthesis; the second signal, photosynthesis inhibiting factor (PIF), partially inhibits photosynthesis. Both HRF from the sponge H. cymiformis and HRF from the coral P. versipora stimulated the release of glycerol from Symbiodinium suggesting that they act at a similar step in the metabolism of this alga. This is the first time that such cell signals have been isolated from a sponge. We suggest that they belong to a family of similar cell signals from symbiotic invertebrates that modify algal carbon metabolism.

A cell signal from the coral Plesiastrea versipora reduces starch synthesis in its symbiotic alga, Symbiodinium sp.

We have previously shown that the coral cell signal, host release factor (HRF) from the scleractinian coral Plesiastrea versipora (Lamarck) stimulates the release of glycerol from its symbiotic dinoflagellate, Symbiodinium sp. Glycerol is a precursor for algal triacylglycerol (TG) and starch, and we have previously observed that HRF reduces the amount of newly synthesized TG in Symbiodinium sp. We have now examined the effect of P. versipora HRF on starch synthesis in isolated Symbiodinium. HRF had no effect on starch synthesis after 2 h photosynthesis (16.3+/-3.0 microg starch per 10(6) algae) compared with algae in seawater (13.9+/-1.2 microg starch per 10(6) algae). However, after 4 h incubation in HRF, there was a reduction (0-76%), in the amount of newly synthesized starch which was correlated with the amount of HRF (10-76 microg/ml). Reducing algal synthesis of both TG and starch in parallel with stimulating glycerol release may provide a mechanism to regulate the population density of intracellular symbiotic algae while still ensuring the transfer of photosynthetically fixed carbon to the animal host in the form of glycerol.

Atomic spectral methods for molecular electronic structure calculations.

Theoretical methods are reported for ab initio calculations of the adiabatic (Born-Oppenheimer) electronic wave functions and potential energy surfaces of molecules and other atomic aggregates. An outer product of complete sets of atomic eigenstates familiar from perturbation-theoretical treatments of long-range interactions is employed as a representational basis without prior enforcement of aggregate wave function antisymmetry. The nature and attributes of this atomic spectral-product basis are indicated, completeness proofs for representation of antisymmetric states provided, convergence of Schrodinger eigenstates in the basis established, and strategies for computational implemention of the theory described. A diabaticlike Hamiltonian matrix representative is obtained, which is additive in atomic-energy and pairwise-atomic interaction-energy matrices, providing a basis for molecular calculations in terms of the (Coulombic) interactions of the atomic constituents. The spectral-product basis is shown to contain the totally antisymmetric irreducible representation of the symmetric group of aggregate electron coordinate permutations once and only once, but to also span other (non-Pauli) symmetric group representations known to contain unphysical discrete states and associated continua in which the physically significant Schrodinger eigenstates are generally embedded. These unphysical representations are avoided by isolating the physical block of the Hamiltonian matrix with a unitary transformation obtained from the metric matrix of the explicitly antisymmetrized spectral-product basis. A formal proof of convergence is given in the limit of spectral closure to wave functions and energy surfaces obtained employing conventional prior antisymmetrization, but determined without repeated calculations of Hamiltonian matrix elements as integrals over explicitly antisymmetric aggregate basis states. Computational implementations of the theory employ efficient recursive methods which avoid explicit construction the metric matrix and do not require storage of the full Hamiltonian matrix to isolate the antisymmetric subspace of the spectral-product representation. Calculations of the lowest-lying singlet and triplet electronic states of the covalent electron pair bond (H(2)) illustrate the various theorems devised and demonstrate the degree of convergence achieved to values obtained employing conventional prior antisymmetrization. Concluding remarks place the atomic spectral-product development in the context of currently employed approaches for ab initio construction of adiabatic electronic eigenfunctions and potential energy surfaces, provide comparisons with earlier related approaches, and indicate prospects for more general applications of the method.

Aposymbiotic Plesiastrea versipora continues to produce cell-signalling molecules that regulate the carbon metabolism of symbiotic algae.

The scleractinian coral Plesiastrea versipora produces cell signals that regulate the carbon metabolism of its symbiotic algae. Host release factor (HRF) stimulates the release of photosynthate, and photosynthesis inhibiting factor (PIF) partially inhibits carbon fixation in freshly isolated symbiotic algae. Naturally occurring aposymbiotic specimens of P. versipora are rare in Port Jackson, Australia, but one that was collected contained HRF and PIF. Artificially produced aposymbiotic corals of P. versipora that had been kept in the dark for up to 23 months continued to produce both HRF and PIF in the absence of photosynthetically active algae. Aposymbiotic P. versipora from which most of the tissue had been removed, regenerated when they were kept in the dark and fed; the regenerated tissue also contained HRF and PIF. These results suggest that the presence of symbiotic algae is not required for the production of HRF and PIF in P. versipora. We suggest that these cell signals may have evolved in response to symbiosis with Symbiodinium sp. but are now always expressed in the coral P. versipora.

A symbiosome membrane is not required for the actions of two host signalling compounds regulating photosynthesis in symbiotic algae isolated from cnidarians.

In many cnidarians, symbiotic algae live within host-derived symbiosomes. We determined whether a symbiosome membrane alters the response of isolated symbiotic algae to two signalling compounds that regulate algal carbon metabolism. Host release factor (HRF), which stimulates photosynthate release, and photosynthesis inhibiting factor (PIF), which inhibits photosynthetic carbon fixation, are found in homogenised tissue of the scleractinian coral Plesiastrea versipora. Compared with seawater controls, photosynthate release from isolated algae incubated in P. versipora homogenate for 2 h in the light was: 6 to 19-fold higher from its own algae (free of symbiosomes); 19 to 32-fold higher from Zoanthid robustus algae (within symbiosomes) and 3 to 24-fold higher from Z. robustus algae (free of symbiosomes); and from cultured algae (free of symbiosomes) was seven-fold higher from Montipora verrucosa and four-fold higher from Cassiopeia xamachana. Incubation of algae in P. versipora homogenate inhibited photosynthesis by: 33-49% in P. versipora algae; 29-47% in Z. robustus algae (regardless of whether or not the symbiosome was present); and 25% in M. verrucosa algae. In C. xamachana algae, photosynthesis increased. We conclude that the symbiosome is not essential for, yet does not block, the effects of HRF and PIF.

Structure of the tomato Adh2 gene and Adh2 pseudogenes, and a study of Adh2 gene expression in fruit.

A cDNA library was constructed from RNA from the pericarp of ripe tomato fruit and four cDNAs encoding ADH2 were isolated and characterized. The cDNAs encode a peptide 379 amino acids in length. They hybridized strongly with a 1.8 kb RNA species well represented in RNA from ripe, but not from mature, unripe fruit, and strongly to a similar RNA species present in hypoxic, but not in aerobic roots. Northern analysis showed that the mRNA for ADH2 in fruit increased in abundance through ripening, particularly during late ripening. In pericarp tissue of fruit, the Adh2 mRNA level increased to a maximum within 8-16 h of exposure to atmospheres with 3% (v/v) oxygen, and returned to the basal level within 16 h of a return to air. The mRNA level was sensitive to the oxygen level in the atmosphere, increasing 20-fold in 12% (v/v) oxygen and 100-fold in 3% oxygen. The homologous tomato Adh2 gene was isolated from a genomic library. The gene has an overall length of 2334 bp from transcription start site to poly(A) addition site and includes eight introns. Southern blot analysis of tomato genomic DNA identified multiple Adh2-related sequences. Two of these, PSA1 and PSA2, were cloned and found to have 94% similarity with each other and 77% similarity with the tomato Adh2 gene over a 1000 bp region. The homologous regions include introns and exons but the equivalent exons contain frame shifts, deletions and stop codons. The two regions are therefore presumptive pseudogenes.

When is an evolutionary approach useful?

Evidence that human behavior is or has been adaptive comes from the likelihood that it would have been useful in our environment of evolutionary adaptedness, that it forms a coherent whole with other characteristics, and that variants contribute or would be likely to contribute to reproductive success. Belsky et al. use the second and third of these, though on the third their evidence is somewhat tenuous. However, their thesis does integrate diverse facts about parenting and development. In general an evolutionary approach is useful if it integrates diverse facts, if it aids clinical practice, and if it helps us toward a full understanding of human nature.

The binding of substituted cis-Pt(II)-diammines to duplex DNA.

The results of a study of the binding to DNA of substituted cis-Pt(II) diammines, (cis-DP) are presented. Computer modeling of a series of cis-Pt(NH2R)2(+2)--where R = H, CH3, cyclopropyl, cyclobutyl, and cyclopentyl--to N7(G) atoms of two adjacent intrastrand guanine bases in a square planar complex in a pentamer duplex of DNA were performed. The stability of the complexes is studied by calculating the relative conformational energy of the cis-DP-DNA complexes with molecular mechanics (MM) and the intrinsic binding energy, which is the relative binding energy for ligand replacement in the presence of the substituents R with quantum mechanics. In the model, the receptor site geometry and the conformation of the DNA is changed little in the accommodation of the series of monosubstituted diammines. These diammines bind to one family of DNA conformations, denoted as IC in a previous study, and this suggests that a common conformational feature in the DNA may exist to explain the smooth trend in activity. The slight increase in van der Waals energy resulting from an increasing number of atoms in the substituents is countered by a larger decrease in the ligand replacement energy as the substituent increases in size. This overall decrease in relative energy is consistent with the slight decrease in activity as the substituent size increases.

Theoretical studies of cis-Pt(II)-diammine binding to duplex DNA.

The binding of cis-Pt(II) diammine (cis-DP) to double-stranded DNA was studied with several kinked conformations that can accommodate the formation of a square planar complex. Molecular mechanics (MM) calculations were performed to optimize the molecular fit. These results were combined with quantum mechanical (QM) calculations to ascertain the relative energetics of ligand binding through water vs direct binding of the phosphate to the ammine and platinum, and to guide the selection of DNA conformations to model complex formation. Based on QM and MM calculations, models are proposed that may be characterized by several general features. A structure involving hydrogen bonding between each ammine and distinct adjacent phosphate groups, referred to as closed conformation (CC), has already been reported. This is also found in the crystal structure of small dimers. We report alternative conformations that may be important in platination of duplex DNA. They are characterized by an intermediate conformation (IC), involving hydrogen bonding between one ammine and phosphate group, and an open conformation (OC), without ammine phosphate hydrogen bonding. The IC and OC can be stabilized by water bridges in the space between the ammine and the phosphate groups. Sugar puckers alternate from the type C(2')-endo or C(1')-exo (S), to the type C(3')-endo or C(2')-exo (N), with intermediate types near O(1')-endo (O). In general, the sugar puckers alternate from S to N to S through the platinated region (3'-TpG*pG*p-5'), with the complexed strand exhibiting, (3')-S*-N*-S-(5') alternation, while the complementary strand shows either (3')-S*-N*-S-(5') or (3')-S*-N*-O-(5') alternation. In both the OC and IC, a hydrogen bond is found between the ammine and O4(T) on thymine (T) at the (3') end, adjacent to the complex site. There is a continuous range of backbone conformations through the platinated region which relate the OC to the IC. The models presented suggest that the dynamics of the binding of the cis-Pt(II)-diammines to adjacent N7(G) in double-stranded DNA may encompass several conformational possibilities, and that water bridges may play a roll in supporting open and intermediate conformations. Proton-proton distances are reported to assist in the experimental determination of conformations.

Relations between levels of complexity in the behavioral sciences.

Some obstacles to progress in the behavioral sciences are discussed. An understanding of human behavior demands a firm descriptive base. This requires the recognition of successive levels of social complexity and of the dialectical relations between them: some difficulties in achieving adequate description are noted. Some principles governing the development of behavior are discussed: the importance of constraints on and predispositions for learning, the role of interpersonal relationships, the question of continuities of development, and the need to come to terms with the relations between successive levels of social complexity. The contribution of the biological concept of adaptation is emphasized. Finally, the development of snake phobias and of gender differences are used to exemplify the issues discussed.

Towards integrating the behavioural sciences to meet the threats of violence and war.

This paper provides a framework for integrating issues in the behavioural and social sciences concerned with the relations between individual aggression and war, and the steps that must be taken to reduce them. It is emphasized that violence is not an inevitable consequence of man's nature, that collective violence involves principles additional to those involved in individual acts of aggression, and that war is an institution involving diverse roles each with its attendant rights and duties. Psychological and other behavioural sciences can make considerable contributions to ameliorating the threat of war.

Roundtable: what is temperament? Four approaches.

4 current approaches to understanding temperament are discussed in the roundtable. In an introductory overview, Goldsmith outlines some of the major convergences and divergences in the understanding of this concept. Theorists representing 4 positions--Goldsmith, Buss and Plomin, Rothbart, and Thomas and Chess--outline their views by responding to each of 6 questions: How do you define temperament and explain the boundaries of the concept? What are the elements of temperatment? How does the construct of temperament permit you to approach issues or organize data in ways that are possible only if this construct is invoked? How does temperament develop? To what extent do you consider temperament to be a personological versus a relational or an interactional construct? and How does your approach deal with issues of temperamental "difficulty"? In 2 commentaries on the theorists' answers, Hinde highlights differences among their positions and indicates issues that current theories of temperament must take into consideration, and McCall draws on common aspects to propose a synthesizing definition that draws on all 4 approaches.

N-acetyl-L-glutamate synthase of Neurospora crassa. Characteristics, localization, regulation, and genetic control.

N-Acetylglutamate synthase, an early enzyme of the arginine pathway, provides acetylglutamate for ornithine synthesis in the so-called "acetylglutamate cycle." Because acetylglutamate is regenerated as ornithine is formed, the enzyme has only a catalytic or anaplerotic role in the pathway, maintaining "bound" acetyl groups during growth. We have detected this enzyme in crude extracts of Neurospora crassa and have localized it to the mitochondria along with other ornithine biosynthetic enzymes. The enzyme is bound to the mitochondrial membrane. The enzyme has a pH optimum of 9.0 and Km values for glutamate and CoASAc of 6.3 and 1.6 mM, respectively. It is feedback-inhibited by L-arginine (I0.5 = 0.16 mM), and its specific activity is augmented 2-3-fold by arginine starvation of the mycelium. Mutants of the newly recognized arg-14 locus lack activity for the enzyme. Because these mutants are complete auxotrophs, we conclude that N-acetylglutamate synthase is an indispensible enzyme of arginine biosynthesis in N. crassa. This work completes the assignment of enzymes of the arginine pathway of N. crassa to corresponding genetic loci. The membrane localization of the enzyme suggests a novel mechanism by which feedback inhibition might occur across a semipermeable membrane.