201 research outputs found

    Less than Bargained for: The Use of Force and the Declining Relevance of the United Nations

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    This essay criticizes the United Nations Charter\u27s standard for the use of force, and outlines a different but still constructive role for the UN in some critical domains. In Part II, we point to serious flaws inherent in the structure of the United Nations Charter rules, particularly the ex ante requirements that nations must satisfy prior to engaging in the use of force. Parts III and IV suggest more modest types of roles that the United Nations could occupy, and how the organization can help promote international security without endangering the security interests of its respective members

    A THERMODYNAMIC DESCRIPTION OF CATION-RNA INTERACTIONS WITH DIFFERING ION ATMOSPHERE COMPOSITION

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    The charged nature of nucleic acids imposes a strong relationship between cations and RNA structure. As a result, RNA folding efficiency is highly dependent on the quantity and types of cations in solution. In vivo, there are a multitude of cations available to interact with RNA. The principal monovalent cation, K+, serves to neutralize most of the negative charges derived from nucleic acids. In addition, there are cations of higher valence that perform a number of important functions. Many studies have confirmed the ability of Mg2+ to promote native RNA structure. In addition to K+ and Mg2+, organic cations (polyamines) such as putrescine2+, spermidine3+, and spermine4+ are believed to be important for the process of RNA folding. All of these cations, both organic and inorganic, differ dramatically in both structural and physical properties. The purpose of the current work is to i) determine if organic and inorganic divalent cations stabilize the same folded state, ii) determine how different divalent ions interact with RNA to promote folding, and iii) develop an understanding of how the ion atmosphere is organized in the presence of three distinct types of cations (K+, Mg2+ and putrescine2+). To pursue these goals, a set of RNAs, all characterized at atomic resolution, were selected to represent a range of selectivity for inorganic ions. This structural information, combined with thermodynamic analyses looking at Mg2+ excess, thermal stability, ligand binding, and folding efficiency provide a comprehensive look at how ions stabilize the native state of RNA. We find that RNAs with Mg2+ chelation sites require either Mg2+ or Ca2+ to properly fold, while putrescine2+ can stabilize the native state of non-chelators, albeit to a lesser degree than Mg2+. Measurement of Mg2+ excess with the native and intermediate states shows that Mg2+ is more effective at stabilizing native structure due to a closer approach to the RNA surface. Therefore, organization of the ion atmosphere is dependent on the types of ions in solution as well as the conformation of the RNA

    Co-crystal structure of the Fusobacterium ulcerans ZTP riboswitch using an X-ray free-electron laser.

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    Riboswitches are conformationally dynamic RNAs that regulate gene expression by binding specific small molecules. ZTP riboswitches bind the purine-biosynthetic intermediate 5-aminoimidazole-4-carboxamide riboside 5\u27-monophosphate (ZMP) and its triphosphorylated form (ZTP). Ligand binding to this riboswitch ultimately upregulates genes involved in folate and purine metabolism. Using an X-ray free-electron laser (XFEL), the room-temperature structure of the Fusobacterium ulcerans ZTP riboswitch bound to ZMP has now been determined at 4.1 Å resolution. This model, which was refined against a data set from ∼750 diffraction images (each from a single crystal), was found to be consistent with that previously obtained from data collected at 100 K using conventional synchrotron X-radiation. These experiments demonstrate the feasibility of time-resolved XFEL experiments to understand how the ZTP riboswitch accommodates cognate ligand binding

    Book Reviews

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    Minimum Standards of Judicial Administration Edited by Arthur T. Vanderbilt Published by The Law Center of New York University for The National Conference of Judicial Councils, 1949. Pp. xxxii,752. 7.50reviewer:WilliamJ.Bowa=================================AvailabilityforWorkByRalphAltmanCambridge:HarvardUniversityPress,1950.Pp.350.7.50 reviewer: William J. Bowa ================================= Availability for Work By Ralph Altman Cambridge: Harvard University Press, 1950. Pp. 350. 4.50 reviewer: Emmett Conner, Charles K. Cosner ================================== Forrester\u27s Edition of Dobie and Ladd\u27s Cases and Materials on Federal Jurisdiction and Procedure By Ray Forrester St. Paul: West Publishing Co., 1950, Pp. vii, 990. 8.50reviewer:CharlesE.Clark======================================LifeInsuranceandEstateTaxPlanningByWilliamJ.BoweNashville:VanderbiltUniversityPress,1950.Pp.90.8.50 reviewer: Charles E. Clark ====================================== Life Insurance and Estate Tax Planning By William J. Bowe Nashville: Vanderbilt University Press, 1950. Pp. 90. 2.10 reviewer: Joseph Trachma
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