Many-body quantum chaos: Recent developments and applications to nuclei

In the last decade, there has been an increasing interest in the analysis of energy level spectra and wave functions of nuclei, particles, atoms and other quantum many-body systems by means of statistical methods and random matrix ensembles. The concept of quantum chaos plays a central role for understanding the universal properties of the energy spectrum of quantum systems. Since these properties concern the whole spectrum, statistical methods become an essential tool. Besides random matrix theory, new theoretical developments making use of information theory, time series analysis, and the merging of thermodynamics and the semiclassical approximation are emphasized. Applications of these methods to quantum systems, especially to atomic nuclei, are reviewed. We focus on recent developments like the study of >imperfect spectra> to estimate the degree of symmetry breaking or the fraction of missing levels, the existence of chaos remnants in nuclear masses, the onset of chaos in nuclei, and advances in the comprehension of the Hamiltonian structure in many-body systems. Finally, some applications of statistical spectroscopy methods generated by many-body chaos and two-body random matrix ensembles are described, with emphasis on Gamow-Teller strength sums and beta decay rates for stellar evolution and supernovae. © 2010 Elsevier B.V.This work is supported in part by the project ‘Frontiers of Theoretical Physics’ of Saha Institute of Nuclear Physics and by Spanish Government grants for the research projects FIS2006-12783-C03-02, FIS2009-11621-C02-01, CSPD-2007-00042-Ingenio2010, and by the Universidad Complutense de Madrid grant UCM-910059. One of us, A.R., is supported by the Spanish program CPAN Consolider-Ingenio2010.Peer Reviewe

Perspectives on 1/f noise in quantum chaos

6 pags., 2 figs. -- XXXIII Symposium on Nuclear Physics 5–8 January 2010, Hacienda Cocoyoc, Morelos, MexicoThe power spectrum of the 5 statistic of quantum spectra presents 1/f(alpha) noise. For chaotic systems alpha = 1 while for regular systems alpha = 2. Although the transition from regularity to chaos is non universal, for a wide variety of systems with a mixed phase space the value of a is intermediate between 1 and 2 and can be related to the fraction of regular or chaotic orbits in the total phase space. This statistic can be a very useful tool for the analysis of experimental spectra, specially in the case of missing levels or spectral sequences with mixed symmetries.This research has been supported in part by Spanish Government grant No. FIS2009- 07277 and No. FIS2006-12783-C03-02, CSPD-2007-00042-Ingenio2010, and by the Universidad Complutense de Madrid grant UCM-910059. A.R. is supported by the CPAN-Consolider program

Crystal structures of CbpF complexed with atropine and ipratropium reveal clues for the design of novel antimicrobials against Streptococcus pneumoniae

Background Streptococcus pneumoniae is a major pathogen responsible of important diseases worldwide such as pneumonia and meningitis. An increasing resistance level hampers the use of currently available antibiotics to treat pneumococcal diseases. Consequently, it is desirable to find new targets for the development of novel antimicrobial drugs to treat pneumococcal infections. Surface choline-binding proteins (CBPs) are essential in bacterial physiology and infectivity. In this sense, esters of bicyclic amines (EBAs) such as atropine and ipratropium have been previously described to act as choline analogs and effectively compete with teichoic acids on binding to CBPs, consequently preventing in vitro pneumococcal growth, altering cell morphology and reducing cell viability. Methods With the aim of gaining a deeper insight into the structural determinants of the strong interaction between CBPs and EBAs, the three-dimensional structures of choline-binding protein F (CbpF), one of the most abundant proteins in the pneumococcal cell wall, complexed with atropine and ipratropium, have been obtained. Results The choline analogs bound both to the carboxy-terminal module, involved in cell wall binding, and, unexpectedly, also to the amino-terminal module, that possesses a regulatory role in pneumococcal autolysis. Conclusions Analysis of the complexes confirmed the importance of the tropic acid moiety of the EBAs on the strength of the binding, through π-π interactions with aromatic residues in the binding site. General significance These results represent the first example describing the molecular basis of the inhibition of CBPs by EBA molecules and pave the way for the development of new generations of antipneumococcal drugs. © 2013 Elsevier B.V.Peer Reviewe

Aromatic esters of bicyclic amines as antimicrobials against Streptococcus pneumoniae

Acknowledgements This work was supported by grants BFU2010-17824 and BIO2013-47684-R (Spanish Ministry of Education and Science), and EU-CP223111 (CAREPNEUMO, European Union). We thank M. Gutiérrez and J. Casanova for excellent technical assistance.A double approach was followed in the search of novel inhibitors of the surface choline-binding proteins (CBPs) of Streptococcus pneumoniae (pneumococcus) with antimicrobial properties. First, a library of 49 rationally-designed esters of alkyl amines was screened for their specific binding to CBPs. The best binders, being esters of bicyclic amines (EBAs), were then tested for their in vitro effect on pneumococcal growth and morphology. Second, the efficiency of EBA-induced CBP inhibition was enhanced about 45 000-fold by multivalency effects upon synthesizing a poly(propylene imine) dendrimer containing eight copies of an atropine derivative. Both approaches led to compounds that arrest bacterial growth, dramatically decrease cell viability, and exhibit a protection effect in animal disease models, demonstrating that the pneumococcal CBPs are adequate targets for the discovery of novel antimicrobials that overcome the currently increasing antimicrobial resistance issues.Depto. de Bioquímica y Biología MolecularFac. de Ciencias BiológicasTRUEpu