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<jats:p>Certain paleobiogeographical reconstructions of ocean currents during the Cretaceous (about 144 to 65 million years ago) suggest that a circumglobal tropical current flowed westward through the continental configuration of that time. Although some numerical climate models failed in initial attempts to simulate this current, simulations with a coupled atmosphere-ocean model with relatively high spatial resolution and a late Cretaceous continental distribution show that a circumglobal current is a robust feature even though local surface currents in the Tethys Seaway reverse during the south Eurasian monsoon months.</jats:p>

<jats:p>Cationic liposomes complexed with DNA (CL-DNA) are promising synthetically based nonviral carriers of DNA vectors for gene therapy. The solution structure of CL-DNA complexes was probed on length scales from subnanometer to micrometer by synchrotron x-ray diffraction and optical microscopy. The addition of either linear λ-phage or plasmid DNA to CLs resulted in an unexpected topological transition from liposomes to optically birefringent liquid-crystalline condensed globules. X-ray diffraction of the globules revealed a novel multilamellar structure with alternating lipid bilayer and DNA monolayers. The λ-DNA chains form a one-dimensional lattice with distinct interhelical packing regimes. Remarkably, in the isoelectric point regime, the λ-DNA interaxial spacing expands between 24.5 and 57.1 angstroms upon lipid dilution and is indicative of a long-range electrostatic-induced repulsion that is possibly enhanced by chain undulations.</jats:p>

<jats:p>The average dipole moment of a water molecule in the condensed phase is enhanced by around 40 percent relative to that of an isolated monomer. This enhancement results from the large polarization caused by the electric field induced by surrounding monomers. A quantitative molecular description of this polarization is essential for modeling aqueous solvation phenomena. This combined theoretical and experimental study of dipole moments in small water clusters provides such a description and also gives insights into the structure of liquid water.</jats:p>

<jats:p> The relative influence of thermal and quantum fluctuations on the proton transfer properties of the charged water complexes H <jats:sub>5</jats:sub> O <jats:sub>2</jats:sub> <jats:sup>+</jats:sup> and H <jats:sub>3</jats:sub> O <jats:sub>2</jats:sub> <jats:sup>−</jats:sup> was investigated with the use of ab initio techniques. These small systems can be considered as prototypical representatives of strong and intermediate-strength hydrogen bonds. The shared proton in the strongly hydrogen bonded H <jats:sub>5</jats:sub> O <jats:sub>2</jats:sub> <jats:sup>+</jats:sup> behaved in an essentially classical manner, whereas in the H <jats:sub>3</jats:sub> O <jats:sub>2</jats:sub> <jats:sup>−</jats:sup> low-barrier hydrogen bond, quantum zero-point motion played a crucial role even at room temperature. This behavior can be traced back to a small difference in the oxygen-oxygen separation and hence to the strength of the hydrogen bond. </jats:p>

<jats:p>Many biological recognition interactions involve ligands and receptors that are tethered rather than rigidly bound on a cell surface. A surface forces apparatus was used to directly measure the force-distance interaction between a polymer-tethered ligand and its receptor. At separations near the fully extended tether length, the ligands rapidly lock onto their binding sites, pulling the ligand and receptor together. The measured interaction potential and its dynamics can be modeled with standard theories of polymer and colloidal interactions.</jats:p>

<jats:p>Recovery and purification difficulties can limit the yield and utility of otherwise successful organic synthesis strategies. A “fluorous synthesis” approach is outlined in which organic molecules are rendered soluble in fluorocarbon solvents by attachment of a suitable fluorocarbon group. Fluorocarbon solvents are usually immiscible in organic solutions, and fluorous molecules partition out of an organic phase and into a fluorous phase in a standard liquid-liquid extraction. Simple yet substantive separations of organic reaction mixtures are achieved without resorting to chromatography. Because fluorous synthesis combines in many respects the favorable purification features of solid-phase synthesis with the favorable reaction, identification, and analysis features of traditional organic synthesis, it should prove valuable in the automated synthesis of libraries of individual pure organic compounds.</jats:p>

<jats:p>Strontium isotope ratios measured from core to rim across plagioclase feldspar crystals can be used to monitor changes in the isotope composition of the magma from which they grew. In samples from three magma systems from convergent margin volcanoes, sudden changes in major element composition, petrographic features, and strontium isotope composition were found to correspond to discrete magmatic events, most likely repeated recharge of more mafic magma with lower ratios of strontium-87 to strontium-86 into a crustally contaminated magma.</jats:p>

<jats:p>Interaction between the TATA box-binding protein TBP and TFIIB is critical for transcription in vitro. An altered-specificity TBP-TFIIB interaction was rationally designed and linked in sequence to an altered-specificity TATA box-TBP interaction to study how TBP and TFIIB function together to support transcription in human cells. The activity of this altered-specificity TATA-TBP-TFIIB array demonstrated that many activators use the known TBP-TFIIB interaction to stimulate transcription. One activator, however, derived from a glutamine-rich activation domain of Sp1, activated transcription independently of this interaction. These results reveal that selectivity in activator function in vivo can be achieved through differential use of TBP and TFIIB.</jats:p>

<jats:p> The <jats:italic> Hs1 <jats:sup>pro-1</jats:sup> </jats:italic> locus confers resistance to the beet cyst nematode ( <jats:italic>Heterodera schachtii</jats:italic> Schmidt), a major pest in the cultivation of sugar beet ( <jats:italic>Beta vulgaris</jats:italic> L.). The <jats:italic> Hs1 <jats:sup>pro-1</jats:sup> </jats:italic> gene was cloned with the use of genome-specific satellite markers and chromosomal break-point analysis. Expression of the corresponding complementary DNA in a susceptible sugar beet conferred resistance to infection with the beet cyst nematode. The native <jats:italic> Hs1 <jats:sup>pro-1</jats:sup> </jats:italic> gene, expressed in roots, encodes a 282-amino acid protein with imperfect leucine-rich repeats and a putative membrane-spanning segment, features similar to those of disease resistance genes previously cloned from higher plants. </jats:p>

<jats:p>Attentional modulation of cortical activity was examined by varying the rate of visual stimuli in object categorization tasks according to single and conjoined features. Activation of dorsolateral frontal cortex was independent of the stimulus presentation rate and elicited by the participant's attention to conjoined compared with single features. Several cortical regions showed attentionally modulated activity. In inferior temporal cortex, modulation was due to an additional bias signal underlying normal rate-correlated activity. In two other regions (premotor cortex and cerebellum), attention modified the correlation of activity and the stimulus presentation rate. Attentional effects in the human cortex are expressed by at least two physiologically distinct mechanisms acting on spatially distributed areas.</jats:p>