300 research outputs found

    Structural information on the light-harvesting complex II of green plants that can be depichered from polarized absorption characteristics.

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    The atomic model of light-harvesting complex II of green plants (LHCII) reveals a densely packed arrangement of 12 chlorophylls and two carotenoids. At the current resolution of 3.4 Angstrom chlorophylls can only be modeled as ''naked'' tetrapyrrole rings. Consequently, definitive assignments of the identities of the chlorophylls (chlorophyll a or chlorophyll b) and the directions of the transition dipole moments are obstructed. These uncertainties lead to a large number of possible configurations, and a detailed understanding of the structure-function relationship is obscured. It is demonstrated that a large reduction in the number of possible configurations and a considerable amount of additional structural information can be obtained by deciphering global features of the polarized absorption spectra within the context of exciton calculations. It is shown that only a limited number of configurations are able to explain the global features of the linear and circular dichroism spectra of LHCII. Assuming that the preliminary assignment of the identities of the 12 chlorophylls by Kuhlbrandt and co-workers is correct, it is possible to deduce the most likely orientations for most of the chlorophylls. The information presented in this study on the most likely orientations will be important for a detailed understanding of the relation between the structure and spectroscopy

    Genetic diversity among some blackberry cultivars and their relationship with Boysenberry assessed by AFLP Markers

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    Blackberry cultivation has increased its popularity in Turkey due to the use of more blackberries in Turkish cuisine. To provide farmers with well adapted blackberry cultivars, some blackberry cultivars including a Boysenberry genotype from North America has been planted to various geographical regions in Turkey. In this study, genetic diversity among these blackberry cultivars and their genetic relationship with Boysenberry and raspberry were analyzed using AFLP markers. Our results indicated that Blackberry cultivars from North America had narrow genetic background which can pose a problem for future breeding programs. Blackberry genotypes selected from Bursa province of Turkey shared all AFLP markers with the cultivar Chester, which suggests that they were not unique genotypes. Although genetic similarity between Boysenberry and blackberry was low, Boysenberry wasgenetically related to common blackberry cultivars. On the other hand, AFLP analysis was unable to detect any genetic relationship between Boysenberry and common raspberry cultivars from North America in this study

    Does policy uncertainty increase relational risks? Evidence from strategic alliances

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    Prior studies on capital investments, including mergers and acquisitions, point to investment irreversibility as the primary factor behind diminished investments during periods of increased policy uncertainty. We show that increased relational risk, due to the potential for counterparty misbehavior or shirking and higher contracting costs, appears to be the primary driver behind the diminished propensity to undertake strategic alliances during enhanced policy uncertainty regimes. Alliances are even less likely during such times when they (a) involve more than two firms, (b) are in industries with greater counterparty risk, and (c) involve partners that require intense contracts

    Use of polyethylene glycol coatings for optical fibre humidity sensing

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    Humidity induced change in the refractive index and thickness of the polyethylene glycol (PEG) coatings are in situ investigated for a range from 10 to 95%, using an optical waveguide spectroscopic technique. It is experimentally demonstrated that, upon humidity change, the optical and swelling characteristics of the PEG coatings can be employed to build a plastic fibre optic humidity sensor. The sensing mechanism is based on the humidity induced change in the refractive index of the PEG film, which is directly coated onto a polished segment of a plastic optical fibre with dip-coating method. It is observed that PEG, which is a highly hydrophilic material, shows no monotonic linear response to humidity but gives different characteristics for various ranges of humidity levels both in index of refraction and in thickness. It undergoes a physical phase change from a semi-crystal line structure to a gel one at around 80% relative humidity. At this phase change point, a drastic decrease occurs in the index of refraction as well as a drastic increase in the swelling of the PEG film. In addition, PEG coatings are hydrogenated in a vacuum chamber. It is observed that the hydrogen has a preventing effect on the humidity induced phase change in PEG coatings. Finally, the possibility of using PEG coatings in construction of a real plastic fibre optic humidity sensor is discussed. (C) 2008 The Optical Society of Japan

    Refined treatment response criteria for indolent systemic mastocytosis proposed by the ECNM-AIM consortium

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    Indolent systemic mastocytosis (ISM) has a favorable prognosis and normal life expectancy. However, many patients suffer from mast cell (MC) mediator-related symptoms, which significantly affect quality of life (QoL). Cutaneous, gastrointestinal, and neurological complaints, musculoskeletal pain, and the presence of skin lesions, anaphylaxis, and osteoporosis are the main symptoms and signs in ISM and must be assessed in all patients before and during treatment. Validated mastocytosis-specific patient-reported outcome measures (PROMs) should be used for this purpose. Serum tryptase and KIT D816V allele burden are recommended as secondary outcome parameters, noting that they do not reflect the severity of signs, symptoms, and related QoL impairment, but indirectly express MC burden. Changes from baseline of 90%, 60%, and 30% indicate complete response >90%, major response 60% to 90%, partial response 30% to 60%, and no response <30% to treatment. To conclude, we recommend the use of PROMs as primary outcome parameters to define treatment response in patients with ISM in clinical trials and in everyday clinical practice.M. C. Carter, J. J. Lyons, and D. D. Metcalfe were supported by the Division of Intramural Research, National Institutes of Allergic and Infectious Diseases, and National Institutes of Health. M. Niedoszytko was supported by the Medical University of Gdansk grant 02-0141/07/231. P. Valent was supported by the Austrian Science Fund (FWF) grant # P32470-B
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