Flexible Orientation Research Articles

RNA Recognition Mechanism of the Minimal Active Domain of the Human Immunodeficiency Virus Type-2 Nucleocapsid Protein

NCp8 of HIV-2 contains two CCHC-type zinc fingers connected by a linker, and is involved in many critical steps of the virus life cycle. It was previously shown that the first zinc finger flanked by the linker is the minimal active domain for specific binding to viral RNA. In our previous study, we determined the three-dimensional structure of NCp8-f1, including the minimal active domain, and found that a hydrogen bond between Asn(11) N(delta)H and Arg(27) O stabilized the conformation of the linker in the vicinity of the zinc finger [Kodera et al. (1998) Biochemistry 37, 17704-17713]. In this study, RNA binding activities of NCp8-f1 and three types of its mutant peptides were analysed by native PAGE assay. The activity and three-dimensional structure of NCp8-f1/N11A, in which alanine is substituted for Asn(11) thereby affecting the conformation of the linker, was analyzed and compared with those of NCp8-f1. We demonstrated that the existence of Arg(4) and/or Lys(5) and Arg(26) and/or Arg(27) were necessary for binding RNA. Furthermore, the linker's flexible orientation, which is controlled by the hydrogen bond between Asn(11) N(delta)H and Arg(27) O, appears to be a structural basis for NCp8 existing as a multi-functional protein.

What is required for growth?

PurposeThis article is concerned with growth processes, growth dimensions and conditions for growth. In it, the author espouses the importance of a strong management mentality capable of providing an appropriate organizational arrangement and supporting competitive growth.Design/methodology/approachOriginal and other research.FindingsOrganizations that are integrated into industries with intensive technologies are more likely to strongly emphasize innovation efforts, flexibility, and growth orientation than firms in industries with long‐linked technologies.Practical implicationsManagement's challenge is to continually try to focalize on organizations' growth, adapting technological capabilities to be in dynamic alignment with the chosen growth dimensions and to take into account business vision and environmental opportunities.Originality/valueSuccessful organizations will be differentiated by their ability to visualize the logic growth dimensions and to leverage technological advances to create an appropriate organizational arrangement to support a competitive growth. The future of technological innovation and advanced manufacturing processes depends on continued investment in cutting‐edge research and development, finding new market segments, and a highly qualified workforce.

Path selection in cockroaches

In gregarious insects, the exploration and the use of the home range can involve both individual navigational abilities and/or chemical trails. Trail formation can result from an active laying of pheromones but can also derive from the incidental deposition of chemical cues. In this study, we investigated whether scent trails can influence path selection in the cockroach Blattella germanica (L.). Experiments were designed to separate the role of prior experience based on the orientation of the path and the presence of trails. In a first phase, cockroaches were able to access freely one or two branches of a platform during a 48 h period. In a second phase, cockroaches were offered a binary choice between one marked and one clean branch, or between two clean branches. In the absence of trails, cockroaches prefer the novel orientation but in the presence of a trail previously laid by the same group of individuals, they prefer the path with the trail, irrespective of orientation. However, cockroaches tended to avoid trails laid by a different group of cockroaches. Overall, our results indicate that both scent cues and response to novelty influence, weakly but significantly, path selection in cockroaches. The plausible nature of scent marks used by cockroaches is discussed. Our study suggests that the influence of incident trailing cues can be modulated by learning to support a flexible orientation strategy depending on individual experience.

Mechanism of fibre assembly through the chaperone–usher pathway

The chaperone-usher pathway directs the formation of adhesive surface fibres in numerous pathogenic Gram-negative bacteria. The fibres or pili consist exclusively of protein subunits that, before assembly, form transient complexes with a chaperone in the periplasm. In these chaperone:subunit complexes, the chaperone donates one beta-strand to complete the imperfect immunoglobulin-like fold of the subunit. During pilus assembly, the chaperone is replaced by a polypeptide extension of another subunit in a process termed 'donor strand exchange' (DSE). Here we show that DSE occurs in a concerted reaction in which a chaperone-bound acceptor subunit is attacked by another chaperone-bound donor subunit. We provide evidence that efficient DSE requires interactions between the reacting subunits in addition to those involving the attacking donor strand. Our results indicate that the pilus assembly platforms in the outer membrane, referred to as ushers, catalyse fibre formation by increasing the effective concentrations of donor and acceptor subunits.

Photosystem I: a search for green plant trimers.

Recent blue-native gel electrophoresis studies gave evidence for the existence of dimeric and trimeric PSI complexes in green plants. We used single particle electron microscopy to investigate all the larger particles from the thylakoid membrane of pea (Pisum sativum var. Charmette). Peak fractions with monomeric, dimeric and trimeric Photosystem I were obtained after solubilization with digitonin and size-exclusion chromatography. The analysis showed that only a few percent of dimers and trimers were present. In the best resolved trimers some of the monomers were oriented upside down. Many classes were fuzzy, indicating a non-specific or flexible orientation. From these results we conclude that the green plant PSI is monomeric within the green plant membrane.

Thermolysis of vic-dihydroxybacteriochlorins: effect of the nature of substrates in directing the formation of chlorin-chlorin dimers with fixed and flexible orientations and their preliminary in vitro photosensitizing efficacy.

The thermolysis products obtained by refluxing a series of vic-dihydroxychlorins in o-dichlorobenzene are characterized. Depending on the nature of substrates, this methodology provides an access for novel carbon-carbon linked chlorin-chlorin dimers and chlorin-porphyrin dimers with fixed and flexible orientations. The configuration of the linkers in the symmetrical and unsymmetrical dimers was confirmed by extensive NMR (COSY, ROESY) and molecular modeling studies. The molecular modeling studies of the energy-optimized dimers with flexible orientation confirmed that one of the chlorin units of the dimeric structure is tilted toward the opposite ring as evident by the shielding effect in the resonances of some of the protons in the (1)H NMR spectroscopy. Among the dimers with fixed orientation, compared to the free-base analogues, the related mono- and di-Zn(II) complexes produced a decreased fluorescence intensity, suggesting a possibility of the faster energy transfer via intersystem crossing (ISC) in the metalated derivatives than the corresponding free-base analogues to produce the corresponding excited triplet states. The photosensitizing efficacy of the monomers and the related dimers was also compared in radiation-induced fibrosarcoma (RIF) tumor cells at variable drug/light doses. In preliminary screening, compared to monomers, the corresponding carbon-carbon linked dimers produced enhanced photosensitizing efficacy.

Nonpeptide GPIIB/IIIA receptor antagonists. Part 21: C-6 flexibility and amide bond orientation are important factors in determining the affinity of compounds for activated or resting platelet receptors

Compound affinity for activated and resting GPIIb/IIIa receptors may differ, and comparison of those differences determines selectivity. Structural features that influence selectivity are discussed.

Egocentric frames of reference used for the retrieval of survey knowledge learned by map and navigation

Two experiments are reported that use a ``point-to-unseen-targets'' task to study the role of egocentric reference frames in the retrieval of survey knowledge learned from either studying a map or navigating an environment. In Experiment 1, performance was generally consistent with the hypothesis that map knowledge is retrieved using a frame of reference centered on the eye, characterized by (a) a fixed orientation in a ``frontal representational plane'' and (b) equal access to spatial relations both in front of, or above, and behind, or below, a right-left retrieval axis. The results of Experiment 2 were consistent with the hypothesis that environment knowledge is retrieved within a frame of reference centered on the body, characterized by (a) flexible orientation within a ``transverse representational plane'' and (b) privileged access to spatial relations located in front of the right-left retrieval axis in representational space. Both types of knowledge function as if they preserve information about the Euclidean angles connecting elements in physical space.

Flexible Leaf Orientations ofArisaema heterophyllumMaximize Light Capture in a Forest Understorey and Avoid Excess Irradiance at a Deforested Site

Abstract Effects of flexible leaflet orientations on light capture and photosynthesis were investigated for Arisaema heterophyllum Blume, a perennial herb with a single palmately compound leaf, in two contrasting light environments: a riparian forest understorey and an adjacent deforested open site. Leaf orientations are determined by inclination of leaflet midvein and folding of leaflet blade. Leaves were flatter and had smaller angles of inclination at the forest site than at the deforested site. Directions (angular altitude and azimuth) of leaf surfaces of the forest site plants were close to those predicted to maximize diffuse light capture at each microsite, as determined by the analysis of a hemispherical canopy photograph. Mean light capture efficiency (the ratio of actual diffuse light capture by a leaf to maximal receivable light) reached 98%. In contrast, marked leaflet folding occurred only at the deforested site. The degree of folding varied diurnally with the maximum around noon. Computer simulations showed that PPFDs (photosynthetically active photon flux density) over the photosynthetic saturation level of A. heterophyllum can be effectively reduced by increasing the slope of leaflet surfaces. The importance of decreasing excess irradiance to avoid photoinhibition and to maintain high rates of photosynthesis was confirmed by artificially constraining leaves horizontally.

Managing Reference Services in the Electronic Age

Summary Managing reference services is challenged by the influx of electronic resources in libraries. Traditional approaches to reference management lack a conceptual framework of effectiveness and emphasize mostly internal processes, downplaying the turbulent environments libraries face. The competing values approach to effectiveness is presented as a broad-based integration of four existing models of organizational effectiveness, encompassing the contradictory values of an internal and an external focus, a control and a flexibility orientation, and means and ends. Implications of the approach for reference management are discussed, and the movement toward diversified team structures examined as a possible solution to the problems of managing reference in the electronic age. The focus is on academic libraries but may apply to other types of libraries as well.

Performance of a polarized deuterium internal target in a medium-energy electron storage ring

A polarized deuterium target internal to a medium-energy electron storage ring is described in the context of spin-dependent (e,e′d) and (e,e′p) experiments. Tensor polarized deuterium was produced in an atomic beam source and injected into a storage cell target. A Breit-Rabi polarimeter was used to monitor the injected atomic beam polarization. An electrostatic ion-extraction system and a Wien filter were utilized to measure on-line the atomic fraction of the target gas (71 ± 2%) in the storage cell. A target thickness t ⋍ 2 × 10 13 2 H/cm 2 was achieved. The target tensor polarization was varied from P zz + = 0.49(3) to P zz − = −0.89(6) while keeping the vector polarization P z at zero. The luminosity was ∼ 2 × 10 31 e − · 2H · cm −2s −1 at a beam current of 120 mA. The performance was stable over a fiv running period. A large acceptance non-magnetic detector system was used for the electron-proton (deuteron) coincidence measurement. It is demonstrated that these techniques result in low backgrounds due to scattering from species other than the polarized target gas and allow for fast and flexible orientation of the target spin. Specific issues such as interfacing the experiment to the storage ring and monitoring the performance of the target system are discussed in detail.

The flexible migratory orientation system of the savannah sparrow (Passerculus sandwichensis)

The orientation system of the Savannah sparrow (Passerculus sandwichensis) is typical of nocturnal migrant passerine birds. It is based on a system of interacting compass senses: magnetic, star, polarized light and, perhaps, sun compasses. The magnetic compass capability develops in birds that have never seen the sky, but the preferred direction of magnetic orientation may be calibrated by celestial rotation (stars at night and polarized skylight patterns during the day). This ability to recalibrate magnetic orientation persists throughout life and enables the bird to compensate for variability in magnetic declination that may be encountered as it migrates. The polarized light compass may be manipulated by exposing young birds to altered patterns of skylight polarization. There is some evidence that the magnetic field may be involved in calibration of the polarized light compass. In short-term orientation decision-making during migration, visual information at sunset overrides both stars and magnetic cues, and polarized skylight is the relevant stimulus in dusk orientation. The star pattern compass seems to be of little importance. This extremely flexible orientation system enables the birds to respond to spatial and temporal variability in the quality and availability of orientation information.

The Orient Express

The changing health care environment makes customer satisfaction a primary concern for all areas of food service. Well-trained, enthusiastic employees are a food service's most valuable asset in achieving superior customer satisfaction. New employee orientation sets the stage for developing a dynamic team committed to customer service. Recognizing this fact, Nutrition and Food Service formed a Process Action Team (PAT) including employees from all levels of the service to design a comprehensive orientation program for new employees. The PAT's goal was to develop a flexible orientation packet that could be used at all levels of the service. The team initially used flowcharts and variance matrix charts to evaluate the existing orientation program, identifying its strengths and weaknesses. PAT members also sought input from employees throughout the service as well as from neighboring institutions of similar complexity regarding the ideal orientation program. From this information, the PAT developed an orientation checklist, and each PAT member expanded upon particular sections of the checklist. The checklist served as a starting point for developing informational sheets that described the service: for example, vignettes of management positions, do's and don’ts for requesting leave, safety tips, important telephone numbers. The sheets were tailored to the type of employee. For example, the clinical staff and the food service workers have somewhat different dress codes, thus distinct sheets were developed. The orientation packet also included an evaluation component, and the feedback from this instrument suggests that the PAT accomplished its goal of developing a flexible, comprehensive orientation packet that meets the needs of new employees at all levels of the service.

Interactions in the flexible orientation system of a migratory bird

MIGRATING birds rely on interacting compass senses: magnetic, star, polarized light and perhaps Sun compasses1,2. During the development of orientation mechanisms, celestial rotation of stars at night3 and of polarized skylight patterns during the day time4 provide information about true compass directions that calibrates the direction of migration selected using the magnetic compass3–11. It might often be advantageous to adjust the magnetic preference by a geographic reference, especially at high northern latitudes where magnetic declination is large. Paradoxically, a magnetic preference so calibrated will be reliable only within a region of similar declination unless magnetic orientation remains open to calibration in older birds, something that earlier studies suggested was not the case1,2. We report here that in the Savannah sparrow (Passerculus sandwichensis) the same sort of calibration of magnetic orientation found in very young birds also occurs in older individuals exposed during the migration period to clear day and night skies within a shifted magnetic field.

Electron scattering from a tensor polarized2H internal target

An experiment (NIKHEF 91-12) is described which measures the spin dependence of the (e,e) and (e,e′p) reactions for polarized deuterium and unpolarized electrons, using the Internal Target Hall facility at the Amsterdam Pulse Stretcher Ring at NIKHEF. Tensor polarized deuterium is produced in an atomic beam source and injected into a storage cell target. Polarimeters are used to monitor the target polarization. A large acceptance non-magnetic detector system is used for the electron-proton (deuteron) coincidence measurement. It is demonstrated that these techniques result in low backgrounds due to scattering from species other than the polarized target gas and allow for fast and flexible orientation of the target spin. Specific issues such as interfacing the experiment to the storage ring and monitoring the performance of the target system are discussed in detail.

The actin monomers in the ternary gelsolin: 2 actin complex are in an antiparallel orientation.

Gelsolin forms ternary complexes with two actin monomers in the presence of Ca2+, which nucleate actin polymerization and cap the barbed ends of filaments. It has therefore been assumed that the two actins are oriented in a similar manner to the terminal subunits in the genetic helix of F-actin. We have tested this using chemical cross-linking with N,N'-1,4-phenylenedimaleimide. For all conditions tested, we identified as the only cross-linked dimeric species an actin dimer indistinguishable from the lower actin dimer of 86 kDa. This lower dimer was previously identified in the initial phase of actin polymerization and also when actin paracrystals are chemically cross-linked [Millonig, R., Salvo, H. & Aebi, U. (1988) J. Cell Biol. 106, 785-796]. It probably defines a contact between adjacent monomers oriented in an antiparallel orientation. In contrast, when F-actin is cross-linked by the same reagent, an upper dimer of apparent molecular mass 115 kDa is formed, which corresponds to adjacent monomers in the genetic helix. The formation of this upper dimer was specifically inhibited by addition of gelsolin to F-actin. Evidence is presented for a Cys374-Cys374 cross-link in the lower dimer. Isolated lower dimer binds to gelsolin in a 1:1 stoichiometry, but it inhibits nucleation of polymerization by gelsolin. Other gelsolin constructs that bind two actin subunits (e.g. the N-terminal half of the molecule, which has severing and capping but no nucleating activity) also form only lower dimer when cross-linked with N,N'-1,4-phenylenedimaleimide. Only segment 2-6 (gelsolin fragment devoid of the N-terminal segment 1) induces an upper dimer orientation of the two actins under nucleating conditions. Our evidence suggests that the two actins associated with gelsolin are not fixed in the orientation of adjacent subunits in F-actin; instead they have a flexible orientation with respect to each other, which permits cross-linking into a stable antiparallel form that does not correspond to the presumed nucleating conformation.

AN IMPROVED STRUCTURAL APPROACH FOR AUTOMATED RECOGNITION OF HANDPRINTED CHARACTERS

This paper examines several line-drawing pattern recognition methods for handwritten character recognition. They are the picture descriptive language (PDL), Berthod and Maroy (BM), extended Freeman's chain code (EFC), error transformation (ET), tree grammar (TG), and array grammar (AG) methods. A new character recognition scheme that uses improved extended octal codes as primitives is introduced. This scheme offers the advantages of handling flexible sizes, orientations, and variations, the need for fewer learning samples, and lower degree of ambiguity. Finally, the simulation of off-line character recognition by the real-time on-line counterpart is investigated.

A vertical alveolar panel (VAP) for outdoor mass cultivation of microalgae and cyanobacteria

A vertical alveolar panel (VAP) for microalgal mass cultivation has been devised and developed. VAP reactors with a surface area of 0·5−2·2 m 2 were constructed from Plexiglas alveolar sheets 1·6 cm in thickness and used from May 1989 to February 1990 to grow Anabaena azollae and Spirulina platensis in the climatic conditions of Central Italy. The VAP has proven to be well suited to the outdoor mass cultivation of cyanobacteria, allowing operation at high cell concentrations (4–7 g liter −1) and achieving high biomass productivity even in winter. The high surface-to-volume ratio (80m −1), its flexible orientation with respect to the sun's rays, effective mixing and O 2 removal through air bubbling and a good control of environmental and nutritional conditions seem to be the major advantages of the system.

Development of Androgyny: Parental Influences

While many researchers have documented the existence of pressures toward traditional sex-typing in the family, schools, and media, little consideration has been given to the effectiveness of these sources in fostering more flexible orientations to sex-typing. The present paper focuses on the extent to which parents are able to influence their children toward the development of nonstereotyped behaviors, conceptualized here in terms of androgyny. This issue is examined through an exploration of several theories of sex-role development and empirical” research on sex-role development. Additional consideration of theories and research on life-span development and resistance among children in the current culture to nonstereotyped behavior lead to a distinction between short-term and long-term effects of nonsexist parental behavior. Although androgynous parents may not produce androgynous children, their children often do grow up to be androgynous adults.

Equality and Functional Imperatives: Another Examination of Distributive Justice in the Israeli Kibbutz

Equality remains a popular ideal but its feasibility in a modern and affluent social framework is often doubted. The Israeli kibbutz is a case of particular interest in this coIltext since it underwent, during the last generation, processes of rapid industrialization, occupational diversification and growing affluence. To what extent was an egalitarian distribution of scarce resources preserved under these circumstances? This issue is discussed in the light of findings from a survey of 650 people in 21 Israeli kibbutzim. When levels of equality in the allocation of four resources (consumption, occupational prestige, self fulfilment and influence) were compared, it became evident that prestige and power are more differentiated than self-fulfilment and consumption. The overall extent of equality in a society is determined by the 'clustering' of various resources and rewards at the disposal of designated groups (strata or classes). No such crystalization of strata could be found within the kibbutz community. It was concluded that while some minimal differentiation in the allocation of some resources or rewards may be a functional imperative, structural equality (i.e. with no emergence of a class system) seems to be feasible not just in the framework of self-imposed poverty, but also in a free and affluent community. EQUALITY AND AFFLUENCE: THE PROBLEM Equality among members of the same community remains one of the major foci of ideological polemic as well as sociological reasoning. Many of those who subscribe to equality as an abstract ideal doubt its feasibility in the real world. More specifically it has often been argued that it will be necessary to pay for equality in terms of other human desiderata, such as liberty, efficiency or cultural advancement. Wrong (1959: 775) for instance claimed that Thc British Journal of Sociology Volumc XXXVII Number 3 This content downloaded from 157.55.39.103 on Mon, 25 Apr 2016 05:03:33 UTC All use subject to http://about.jstor.org/terms 336 Shimon Shur and Yochanan Peres those who intended the abolition of any unequal reward system altogether (notably sectarian Christian communes and Israeli kibbutzim) have been willing to pay the price set by Davis and Moore: foregoing the advantages of an elaborate division of labor, and permanent commitment to an agrarian way of life. The demographic, occupational and cultural realities of Israeli kibbutz life have changed drastically since Wrong's statement was made. The bulk of these developments can be summarized under three headings: (a) Demographic Transition The typical Israeli kibbutz is no longer composed mainly of individuals who chose to join a commune. Rather, a large proportion of the currently active members are kibbutz-born or persons who joined through marriage to a kibbutz-born member. This population was not self selected for egalitarian idealism and/or relative indifference to material rewards, to the same degree as were the first generation. Moreover, it has been indicated that kibbutzborn members tend to adopt a more pragmatic and flexible value orientation than their founding parents (Cohen and Rosner, 1970). If functional imperatives are expected to bring about a transformation towards a more 'conventional' system of stratification in the long run, then, it should be noted that the kibbutz has already passed the 'short run.' (b) Industrialization The economist Yehuda Don (1983: 372) described the growing importance of industry in the kibbutz This process of industrialization took place in less than twenty years. Industrial labor force increased . . . by 260 per cent . . . virtually the total increment to the kibbutz labor force has been assigned to industry. Output (in constant 1958 prices) . . . increased by 2500 per cent. Naturally industrialization was accompanied by an elaborate and specialized division of labour (which diffused to the agrarian sector as well), a diversification of consumption, and a higher standard of