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A molecular dynamics study of lunasin

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      Abstract

      Lunasin, a 43 amino acid peptide, suppresses chemically induced transformations in mammalian cells and skin carcinogenesis in mice. This peptide has also been reported to exhibit very good bioavailability after its oral administration. However, despite its biological and medicinal significance, the exact three-dimensional (3D) structure of lunasinis thus far not yet fully characterized. Thus this work is aimed at exploring the conformational profile of lunasin,using classical molecular dynamics (MD) simulations at the time scale of 300 ns. The results obtained from the MD trajectory reveal that lunasin has a strong propensity to exhibit three characteristic a helical bundles in its structure supported by residues His5-Cys10, Cys22-Ile30 and Asp35-Asp41. The reported cell adhesion motif (Arg-Gly-Asp) of lunasin responsible for its binding to cell chromatin, on other hand, did not exhibit any characteristic secondary feature. The structural information obtained from the current study could be useful to better understand the bioactive conformation of lunasin.

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      Most cited references 31

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      Dependence of paclitaxel sensitivity on a functional spindle assembly checkpoint.

      Paclitaxel stabilizes microtubules, causing mitotic arrest and activating the spindle assembly checkpoint. We determined whether suppression of the checkpoint genes Mad2 and BubR1 affects paclitaxel resistance and whether overexpression of Mad2 protein in checkpoint-defective cells enhances paclitaxel sensitivity. Suppression of Mad2 and BubR1 in paclitaxel-treated cancer cells abolished checkpoint function, resulting in paclitaxel resistance that correlated with suppression of cyclin-dependent kinase-1 activity. In contrast, overexpression of Mad2 in cells with a checkpoint defect attributable to low Mad2 expression restored checkpoint function, resulting in enhanced paclitaxel sensitivity that correlated with enhanced cyclin-dependent kinase-1 activity. However, overexpression of Mad2 failed to enhance paclitaxel sensitivity via checkpoint activation in Mad2-independent checkpoint-defective and -intact cells. Thus, checkpoint function is required for paclitaxel sensitivity. These findings show that any molecules that could interfere with the spindle assembly checkpoint could generate paclitaxel resistance in any patient.
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        Extracellular ATP in plants. Visualization, localization, and analysis of physiological significance in growth and signaling.

        Extracellular ATP (eATP) in animals is well documented and known to play an important role in cellular signaling (e.g. at the nerve synapse). The existence of eATP has been postulated in plants; however, there is no definitive experimental evidence for its presence or an explanation as to how such a polar molecule could exit the plant cell and what physiological role it may play in plant growth and development. The presence of eATP in plants (Medicago truncatula) was detected by constructing a novel reporter; i.e. fusing a cellulose-binding domain peptide to the ATP-requiring enzyme luciferase. Application of this reporter to plant roots allowed visualization of eATP in the presence of the substrate luciferin. Luciferase activity could be detected in the interstitial spaces between plant epidermal cells and predominantly at the regions of actively growing cells. The levels of eATP were closely correlated with regions of active growth and cell expansion. Pharmacological compounds known to alter cytoplasmic calcium levels revealed that ATP release is a calcium-dependent process and may occur through vesicular fusion, an important step in the polar growth of actively growing root hairs. Reactive oxygen species (ROS) activity at the root hair tip is not only essential for root hair growth, but also dependent on the cytoplasmic calcium levels. Whereas application of exogenous ATP and a chitin mixture increased ROS activity in root hairs, no changes were observed in response to adenosine, AMP, ADP, and nonhydrolyzable ATP (betagammameATP). However, application of exogenous potato (Solanum tuberosum) apyrase (ATPase) decreased ROS activity, suggesting that cytoplasmic calcium gradients and ROS activity are closely associated with eATP release.
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          Nonfluorescent chlorophyll catabolites in loquat fruits (Eriobotrya japonica Lindl.).

          Nonfluorescent chlorophyll catabolites (NCCs) and nonfluorescent dioxobilane chlorophyll catabolites (NDCCs) are the terminal compounds of the chlorophyll degradation pathway that may display beneficial properties to human health related to their antioxidant properties, which were recently shown. A profile of NCCs/NDCC of the loquat fruit Eriobotrya japonica Lindl. is described. From the 13 known different NCC structures described to date, three have been identified in loquats. Two new structures not defined so far were characterized in loquat fruits: Ej-NCC2, which corresponds to the methyl ester at C13(2) of Bn-NCC1 and in very low amount Ej-NDCC1, the only NDCC found in loquats. Keto-enol tautomerism at the C13(1) position in NCCs is described for the first time as a regular process in chlorophyll catabolism, probably through a nonspecific mechanism since almost all the chlorophyll catabolites structures detected in fruits of loquat present keto and enol tautomers. The results obtained have been possible through a high-performance liquid chromatography coupled with electrospray ionization ion trap and quadropole time-of-flight mass spectrometry fitted with a powerful postprocessing software.
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            Author and article information

            Affiliations
            [1 ] Durban University of Technology South Africa
            Contributors
            Role: ND
            Role: ND
            Journal
            sajc
            South African Journal of Chemistry
            S.Afr.j.chem. (Online)
            The South African Chemical Institute (Durban )
            1996-840X
            2012
            : 65
            : 0
            : 115-124
            S0379-43502012000100020

            http://creativecommons.org/licenses/by/4.0/

            Product
            Product Information: SciELO South Africa
            Categories
            Chemistry, Analytical
            Chemistry, Applied
            Chemistry, Inorganic & Nuclear
            Chemistry, Medicinal
            Chemistry, Multidisciplinary
            Chemistry, Organic
            Chemistry, Physical
            Electrochemistry

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