Difference in direct charge-parity violation between charged and neutral B meson decays

Equal amounts of matter and antimatter are predicted to have been produced in the Big Bang, but our observable Universe is clearly matter-dominated. One of the prerequisites for understanding this elimination of antimatter is the nonconservation of charge-parity (CP) symmetry. So far, two types of CP violation have been observed in the neutral K meson (K(0)) and B meson (B(0)) systems: CP violation involving the mixing between K(0) and its antiparticle (and likewise for B(0) and ), and direct CP violation in the decay of each meson. The observed effects for both types of CP violation are substantially larger for the B(0) meson system. However, they are still consistent with the standard model of particle physics, which has a unique source of CP violation that is known to be too small to account for the matter-dominated Universe. Here we report that the direct CP violation in charged B(+/-)-->K(+/-)pi(0) decay is different from that in the neutral B(0) counterpart. The direct CP-violating decay rate asymmetry, (that is, the difference between the number of observed B(-)-->K(-)pi(0) event versus B(+)-->K(+) pi(0) events, normalized to the sum of these events) is measured to be about +7%, with an uncertainty that is reduced by a factor of 1.7 from a previous measurement. However, the asymmetry for versus B(0)-->K(+)pi(-) is at the -10% level. Although it is susceptible to strong interaction effects that need further clarification, this large deviation in direct CP violation between charged and neutral B meson decays could be an indication of new sources of CP violation-which would help to explain the dominance of matter in the Universe.     

Subsurface scattering in point-based rendering

The Department of Computer Engineering, Sejong University in Korea and ETH Zurich in Switzerland have recently introduced a novel and simple framework for rendering subsurface scattering on surfaces represented by points. This is useful for realistically rendering a cloud of points representing translucent materials such as the human skin. This significant study is reported in Vol. 53, No. 5 of SCIENCE CHINA Information Sciences.
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Genetics of early mammalian folliculogenesis

Early ovarian folliculogenesis begins with the breakdown of germ cell clusters and formation of primordial follicles. Primordial follicles are the smallest ovarian follicle units continuously recruited to grow into primary and more advanced ovarian follicles. Genes expressed in the germ cells such as Figla, Nobox, Kit and Ntrk2, as well as genes expressed in the surrounding somatic cells such as Foxl2, Kitl and Ngf, play critical functions during early folliculogenesis. Transgenic mice continue to provide important insights into the genetic pathways that regulate early mammalian folliculogenesis. Genes critical in early folliculogenesis are important determinants of reproductive life span and represent candidate genes for human ovarian failure. Received 25 August 2005; received after revision 18 October 2005; accepted 21 November 2005     

A new algorithm for building the GSA-form

Gated Single Assignment (GSA) form is used to transform an imperative program into a form suitable for dataflow interpretation. We describe a GSA-formed Control Flow Graph (CFG) that contains gating functions and the information of switches. We also present an algorithm to transform an imperative program into a GSA-formed CFG. Transformation of an imperative program into a GSA-formed CFG provides the basis for generating dataflow graphs(DFG). By using GSA-formed CFG, we can transform an imperative program into a DFG more simply comparing with previous methods, and show an expectation of use with demand- and control-driven model. As we create an intermediate form which has essential information for translation, it will be used to do transformations for various kinds of dataflow models.     

The action of the cholecystokinin-A receptor antagonist,devazepide, on the digestive system of the chicken

The influence of the cholecystokinin (CCK)-A receptor antagonist, devazepide (DVZ), on the chicken digestive tract was investigated. The passage of food from the crops of birds treated with DVZ was not significantly different from that of the control. DVZ treatment did not inhibit the biliary flow stimulated by the CCK analogue, caerulein. Dispersed chicken pancreatic acini stimulated with CCK were treated with various concentrations of DVZ. At 10^–5 M, DVZ completely inhibited amylase release; this concentration was much higher than those reported to have similar effects in mammals. The results suggest that the action DVZ as a CCK antagonist in the chicken is very weak.     

Structure and function of an irreversible agonist-β(2) adrenoceptor complex

G-protein-coupled receptors (GPCRs) are eukaryotic integral membrane proteins that modulate biological function by initiating cellular signalling in response to chemically diverse agonists. Despite recent progress in the structural biology of GPCRs, the molecular basis for agonist binding and allosteric modulation of these proteins is poorly understood. Structural knowledge of agonist-bound states is essential for deciphering the mechanism of receptor activation, and for structure-guided design and optimization of ligands. However, the crystallization of agonist-bound GPCRs has been hampered by modest affinities and rapid off-rates of available agonists. Using the inactive structure of the human β(2) adrenergic receptor (β(2)AR) as a guide, we designed a β(2)AR agonist that can be covalently tethered to a specific site on the receptor through a disulphide bond. The covalent β(2)AR-agonist complex forms efficiently, and is capable of activating a heterotrimeric G protein. We crystallized a covalent agonist-bound β(2)AR-T4L fusion protein in lipid bilayers through the use of the lipidic mesophase method, and determined its structure at 3.5?? resolution. A comparison to the inactive structure and an antibody-stabilized active structure (companion paper) shows how binding events at both the extracellular and intracellular surfaces are required to stabilize an active conformation of the receptor. The structures are in agreement with long-timescale (up to 30?μs) molecular dynamics simulations showing that an agonist-bound active conformation spontaneously relaxes to an inactive-like conformation in the absence of a G protein or stabilizing antibody.     

Enzyme-catalysed [4+2] cycloaddition is a key step in the biosynthesis of spinosyn A

The Diels-Alder reaction is a [4+2] cycloaddition reaction in which a cyclohexene ring is formed between a 1,3-diene and an electron-deficient alkene via a single pericyclic transition state. This reaction has been proposed as a key transformation in the biosynthesis of many cyclohexene-containing secondary metabolites. However, only four purified enzymes have thus far been implicated in biotransformations that are consistent with a Diels-Alder reaction, namely solanapyrone synthase, LovB, macrophomate synthase, and riboflavin synthase. Although the stereochemical outcomes of these reactions indicate that the product formation could be enzyme-guided in each case, these enzymes typically demonstrate more than one catalytic activity, leaving their specific influence on the cycloaddition step uncertain. In our studies of the biosynthesis of spinosyn A, a tetracyclic polyketide-derived insecticide from Saccharopolyspora spinosa, we identified a cyclase, SpnF, that catalyses a transannular [4+2] cycloaddition to form the cyclohexene ring in spinosyn A. Kinetic analysis demonstrates that SpnF specifically accelerates the ring formation reaction with an estimated 500-fold rate enhancement. A second enzyme, SpnL, was also identified as responsible for the final cross-bridging step that completes the tetracyclic core of spinosyn A in a manner consistent with a Rauhut-Currier reaction. This work is significant because SpnF represents the first example characterized in vitro of a stand-alone enzyme solely committed to the catalysis of a [4+2] cycloaddition reaction. In addition, the mode of formation of the complex perhydro-as-indacene moiety in spinosyn A is now fully established.