手性Schiff－Base在手性PTC条件下的双不对称诱导烷基化

本文报道了以苯甲醛甘氨酸酯〔乙酯,（—）—簿荷醇酯〕西佛碱作为反应底物,烯丙基溴,溴苄,对硝基溴作为烷基化试剂,在以（—）—Ｎ—基氯化辛可宁丁,（＋）－Ｎ基氯化辛可宁作为催化剂的固液相转移条件下的双不对称诱导烷基化反应,进而水解得到α—光学活性氨基酸。光学产率为２．５７—２２．４％,实验中观察到了双不对称诱导效应。     

Self-assembly of rationally designed peptides under two-dimensional confinement

The rational design of interfacially confined biomolecules offers a unique opportunity to explore the cooperative relationship among self-assembly, nucleation, and growth processes. This article highlights the role of electrostatics in the self-assembly of β-sheet-forming peptides at the air-water interface. We characterize the phase behavior of a periodically sequenced sheet-forming peptide by using Langmuir techniques, Brewster angle microscopy, attenuated total reflection Fourier transform infrared spectroscopy, and circular dichroism spectroscopy. We find that peptides with an alternating binary sequence transition at high pressures from discrete circular domains to fibrous domains. The qualitative behavior is independent of surface pressure but dependent on molecular areas. In addition, thermodynamic models are employed to specifically quantify differences in electrostatics by obtaining parameters for the critical aggregation area, the limiting molecular area, and the dimensionless ratio of line tension/dipole density. Using these parameters, we are able to relate localized charge distribution to phase transitions, which will allow us to apply these molecules to examine how the dynamics of self-assembly can be directly coupled to the formation of composite nanostructures in biology.     

Dissipative particle dynamics simulation on the meso-scale structure of diblock copolymer under cylindrical confinement

The meso-scale structure of symmetric diblock copolymer under cylindrical confinement is studied by dissipative particle dynamics (DPD). The simulation results show that coiled cylindrical geometry is favored in the presence of larger cylinder radius (R/L ₀>～1.5), and the number of rings depends on the cylinder radius. Because of the cylinder wall's selectivity, each block can form the central core, but only the preferential block forms the outmost layer. An approximately linear relationship exists between structure transition point, which is approximately in proportion to the 3/5 exponential of chain length of copolymer and number of layers. As the cylinder radius is decreased, a helical morphology is found. Lamellae parallel to the underside of the cylinder appear when the cylinder radius is made smaller (R/L ₀ < ～1.1).     

Improvement of plasma energy confinement in tokamak under radiative cooling of the edge plasma

Improvement of plasma energy confinement in the T-10 tokamak by injection of impurity gases was studied experimentally. Injection of Ne and He in the ohmic and ECR heating regimes allows one to separate the dependences of energy confinement on the plasma density and on the edge plasma cooling rate. It is shown that the well-known dependence of the energy confinement time on the plasma density is, in fact, the dependence on the radiative loss power. This phenomenon can be explained by plasma self-organization. The experiments are described by a thermodynamic model for self-organized plasma in which the transport coefficient depends on the difference between the actual and self-consistent pressure profiles. The reduction in the heat flux at the plasma edge due to radiative cooling leads to a decrease in the transport coefficient in this region and, accordingly, improves energy confinement. Results of approximate model calculations for experiments with Ne injection are presented.     

Searching target sites on DNA by proteins: Role of DNA dynamics under confinement

DNA-binding proteins (DBPs) rapidly search and specifically bind to their target sites on genomic DNA in order to trigger many cellular regulatory processes. It has been suggested that the facilitation of search dynamics is achieved by combining 3D diffusion with one-dimensional sliding and hopping dynamics of interacting proteins. Although, recent studies have advanced the knowledge of molecular determinants that affect one-dimensional search efficiency, the role of DNA molecule is poorly understood. In this study, by using coarse-grained simulations, we propose that dynamics of DNA molecule and its degree of confinement due to cellular crowding concertedly regulate its groove geometry and modulate the inter-communication with DBPs. Under weak confinement, DNA dynamics promotes many short, rotation-decoupled sliding events interspersed by hopping dynamics. While this results in faster 1D diffusion, associated probability of missing targets by jumping over them increases. In contrast, strong confinement favours rotation-coupled sliding to locate targets but lacks structural flexibility to achieve desired specificity. By testing under physiological crowding, our study provides a plausible mechanism on how DNA molecule may help in maintaining an optimal balance between fast hopping and rotation-coupled sliding dynamics, to locate target sites rapidly and form specific complexes precisely.     

Stability of a quasi-flute mode under the Bernstein-Kadomtsev condition in a toroidal confinement system

It is shown that the growth rate of the MHD instability in toroidal configurations is slower in a situation in which the Bernstein-Kadomtsev condition is satisfied while the Mercier stability criterion is not. Under the Bernstein-Kadomtsev condition, Alfvénic Mercier modes are not excited, but quasi-flute acoustic Mercier modes develop instead. In confinement systems with closed magnetic field lines, the Bernstein-Kadomtsev condition ensures MHD stability; however, a small rotational transform produced by magnetic perturbations can give rise to a quasi-flute acoustic instability whose growth rate is proportional to the perturbation amplitude, in which case the fastest growing oscillations are those with the shortest wavelengths.     

Asymmetric perception of twilight affecting diapause induction by the fall webworm Hyphantria cunea

In order to assess the natural photophase effective for controlling the pupal diapause of Hyphantria cunea, larvae were exposed in the long-day season to natural conditions of light (through a window) for a period of 14 hr, 50 min. This photophase included different portions of either the dawn or dusk twilight period. Since the critical photophase was found to be 14 hr 35 min under natural daylight as well as under conditions of artificial light, 50% diapause was expected when the twilight intensity reached the threshold level 15 min after the onset (dawn) or before the end (dusk) of the exposure. The threshold intensities of twilight thus determined showed a significant asymmetry, being about 1 and 10 lux at dawn and dusk, respectively. From this, it was inferred that the photophase under natural conditions would begin about 40 min before sunrise and end about 20 min after sunset. This asymmetry in sensitivity seems to be caused by the conditions (light or dark) to which the larval photo-receptive system has been exposed. The larvae that had been kept under artificial light of 180–200 lux for 14 hr were sensitive to a subsequent 1 hr exposure to 0.5 lux or greater and averted diapause, whereas those held under 9,000 lux failed to avert diapause even when the photophase was supplemented by light of 7.5 lux for 1 hr

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Résumé De facon à évaluer la photophase naturelle efficace pour maîtriser la diapause nymphale de Hyphantria cunea, les chenilles ont été exposées pendant la saison aux jours longs aux conditions naturelles d'éclairement (à travers une fenêtre) pendant une période de 14 h 50 min. Puisqu'il a été établi que la photophase critique est de 14 h 35 min sous éclairement naturel aussi bien qu'artificiel, 50% de diapause était prévu quand l'intensité crépusculaire atteignait le seuil 15 min après le début (aube) ou avant la fin (crépuscule) de l'exposition. Les intensités-seuil crépusculaires ainsi déterminées ont présenté une asymétrie significative, étant respectivement de 1 à 10 lux à l'aube et au crépuscule. Il a été déduit de ces observations que la photophase en conditions naturelles commencerait environ 40 min avant le lever du soleil et se terminerait environ 20 min après son coucher. L'asymétrie de cette sensibilité semble être due aux conditions (lumière ou obscurité) auxquelles le système photo-récepteur des chenilles a été exposé. Les chenilles qui ont été maintenues pendant 14 h sous éclairage artificiel de 180–200 lux sont sensibles à une exposition ultérieure de 0,5 lux ou plus et évitent la diapause, tandis que celles maintenues à 9000 lux ou plus n'évitent pas la diapause quand la photophase est prolongée par un éclairement de 7,5 lux pendant une heure.

     

Engineering productive enzyme confinement

Natural enzymes were selected to function inside the cell, not in the test tube; therefore, their performance is optimized for the crowded conditions encountered in vivo. Most man-made matrices for enzyme confinement lead to suboptimal catalytic activity. Ackerman and colleagues showed that an entrapping environment consisting of functionalized mesoporous silica actually enhances enzyme activity beyond the test-tube levels of free enzymes in solution. These findings provide an approach for dissecting the effect of various contributors to enzyme activity and thereby provide a means for fine-tuning the entrapping matrices to optimize enzyme performance in a rational way.     

Heat confinement in spheromaks

Calculations are presented showing the temperatures expected in a spheromak sustained by continuous injection of helicity, based on a model previously shown to agree with temperatures achieved in spheromak experiments carried out in the 1980's. New experiments with Thomson scattering measurements of electron temperature will provide an experimental test.     

Human immunity system under conditions of 105-day isolation and confinement in an artificial environment

The study of the adaptive immunity system of six test subjects volunteered for a 105-day isolation and confinement in an artificial environment showed activation of the immune system and overstrain and depletion of its functional reserve. Significant differences in the adaptability of the immune system of the test subjects indicate individual susceptibility to disorders in immunological reactivity.     

Critical polyelectrolyte adsorption under confinement: planar slit, cylindrical pore, and spherical cavity

We explore the properties of adsorption of flexible polyelectrolyte chains in confined spaces between the oppositely charged surfaces in three basic geometries. A method of approximate uniformly valid solutions for the Green function equation for the eigenfunctions of polymer density distributions is developed to rationalize the critical adsorption conditions. The same approach was implemented in our recent study for the "inverse" problem of polyelectrolyte adsorption onto a planar surface, and on the outer surface of rod-like and spherical obstacles. For the three adsorption geometries investigated, the theory yields simple scaling relations for the minimal surface charge density that triggers the chain adsorption, as a function of the Debye screening length and surface curvature. The encapsulation of polyelectrolytes is governed by interplay of the electrostatic attraction energy toward the adsorbing surface and entropic repulsion of the chain squeezed into a thin slit or small cavities. Under the conditions of surface-mediated confinement, substantially larger polymer linear charge densities are required to adsorb a polyelectrolyte inside a charged spherical cavity, relative to a cylindrical pore and to a planar slit (at the same interfacial surface charge density). Possible biological implications are discussed briefly in the end.     

Neural Responses to Truth Telling and Risk Propensity under Asymmetric Information

Trust is multi-dimensional because it can be characterized by subjective trust, trust antecedent, and behavioral trust. Previous research has investigated functional brain responses to subjective trust (e.g., a judgment of trustworthiness) or behavioral trust (e.g., decisions to trust) in perfect information, where all relevant information is available to all participants. In contrast, we conducted a novel examination of the patterns of functional brain activity to a trust antecedent, specifically truth telling, in asymmetric information, where one individual has more information than others, with the effect of varying risk propensity. We used functional magnetic resonance imaging (fMRI) and recruited 13 adults, who played the Communication Game, where they served as the “Sender” and chose either truth telling (true advice) or lie telling (false advice) regarding the best payment allocation for their partner. Our behavioral results revealed that subjects with recreational high risk tended to choose true advice. Moreover, fMRI results yielded that the choices of true advice were associated with increased cortical activation in the anterior rostral medial and frontopolar prefrontal cortices, middle frontal cortex, temporoparietal junction, and precuneus. Furthermore, when we specifically evaluated a role of the bilateral amygdala as the region of interest (ROI), decreased amygdala response was associated with high risk propensity, regardless of truth telling or lying. In conclusion, our results have implications for how differential functions of the cortical areas may contribute to the neural processing of truth telling.     

Asymmetric expression of a poplar ACC oxidase controls ethylene production during gravitational induction of tension wood

Ethylene is produced in wood-forming tissues, and when applied exogenously, it has been shown to cause profound effects on the pattern and rate of wood development. However, the molecular regulation of ethylene biosynthesis during wood formation is poorly understood. We have characterised an abundant 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene (PttACO1) in the wood-forming tissues of Populus tremula (L.) x P. tremuloides (Michx). PttACO1 is primarily expressed in developing secondary xylem, and is specifically upregulated during secondary wall formation. Nevertheless, according to GC-MS analysis combined with tangential cryosectioning, the distribution of ACC was found to be fairly uniform across the cambial-region tissues. Gravitational stimulation, which causes tension wood to form on the upper side of the stem, resulted in a strong induction of PttACO1 expression and ACC oxidase activity in the tension wood-forming tissues. The ACC levels increased in parallel to the PttACO1 expression. However, the increase on the upper (tension wood) side was only minor, whereas large amounts of both ACC and its hydrolysable conjugates accumulated on the lower (opposite) side of the stem. This suggests that the relatively low level of ACC on the tension wood side is a result of its conversion to ethylene by the highly upregulated PttACO1, and the concurrent accumulation of ACC on the opposite side of the wood is because of the low PttACO1 levels. We conclude that PttACO1 and ACC oxidase activity, but not ACC availability, are important in the control of the asymmetric ethylene production within the poplar stem when tension wood is induced by gravitational stimulation.     

Callus induction and regeneration in sugarcane under drought stress

Tissue culture methods are useful in assessing the tolerance of various stresses due to the ease of controlling stress under in vitro conditions. This study aimed to investigate the response of sugarcane genotyps to drought stress using calli as a model system. For inducing sugarcane callus, the medium of Murashige and Skoog (MS) was used with different mannitol concentrations (100, 200, and 300 mM) to measure their effects on callus frequency, the day of callus initiation, embryogenic potential, relative growth rate (RGR), water and proline contents, K⁺ and Na⁺ contents, as well as the formation of shoot and roots for three sugarcane genotypes (e.g., GT 54-9, G 84-47, and pH 8013). The RAPD-PCR analysis was carried out using five oligonucleotide primers to identify the genetic variation among sugarcane genotypes. The results indicated that the degree of callus proliferation varied from 70 − 86%. The highest value of callus proliferation, PGR, shoot formation was recorded for the genotype GT 54-9 compared to the other two genotypes (G 84-47 and pH 8013). Calli treated with 100 mM mannitol showed the highest RGR, proline and waer contents for the genotype GT 54-9, while, those treated with 300 mM recorded the lowest values of these parameters for the genotype pH 8013. The genotype G 84-47 collected highest Na⁺ content, while the genotype pH 8013 collected highest K⁺ content. The results of this study recommend preference for GT 54-9 genotype, which is considered the most promising genotype, showing more tolerance to drought stress based on all studied traits.