Andrés Felipe Vinasco Mondragón

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The three-dimensional structure of the 67K amino-terminal fragment of Escherichia coli DNA topoisomerase I has been determined to 2.2 A resolution. The polypeptide folds in an unusual way to give four distinct domains enclosing a hole large enough to accommodate a double-stranded DNA. The active-site tyrosyl residue, which is involved in the transient(More)
The crystal structure of the amino-terminal domain of phage 434 repressor has been solved using molecular replacement methods and refined to an R-factor of 19.3% against data to 2.0 A resolution. The protein comprises five short alpha-helices. Two of these form a helix-turn-helix motif, very similar to those found in related proteins. The protein is(More)
A variety of cellular processes, including DNA replication, transcription, and chromosome condensation, require enzymes that can regulate the ensuing topological changes occurring in DNA. Such enzymes-DNA topoisomerases-alter DNA topology by catalysing the cleavage of single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA), the passage of DNA through the(More)
We derive closed analytical expressions for the complex Berry phase of an open quantum system in a state which is a superposition of resonant states and evolves irreversibly due to the spontaneous decay of the metastable states. The codimension of an accidental degeneracy of resonances and the geometry of the energy hypersurfaces close to a crossing of(More)
Assuming that the lepton, quark and Higgs fields belong to the three-dimensional reducible representation of the permutation group S 3 , we suggest a minimal S 3 invariant extension of the standard model. We find that in the leptonic sector the exact S 3 ×Z 2 symmetry, which allows 6 real independent parameters, is consistent with experimental data and(More)
We study the complex geometric phase acquired by the resonant states of an open quantum system which evolves irreversibly in a slowly time dependent environment. In analogy with the case of bound states, the Berry phase factors of resonant states are holonomy group elements of a complex line bundle with structure group C *. In sharp contrast with bound(More)
We solved numerically the implicit, trascendental equation that defines the eigenenergy surface of a degenerating isolated doublet of unbound states in the simple but illustrative case of the scattering of a beam of particles by a double barrier potential. Unfolding the degeneracy point with the help of a contact equivalent approximant, crossings and(More)
Different ansätze for the breaking of the flavour permutational symmetry according to S L (3) ⊗ S R (3) ⊃ S L (2) ⊗ S R (2) give different Hermitian mass matrices of the same modified Fritzsch type, which differ in the symmetry breaking pattern. In this work we obtain a clear and precise indication on the preferred symmetry breaking scheme from a fit of the(More)
Of the 116 Neriidae species known to date, 113 species have not been studied in their immature stages. Here, we examine the development of the immature stages of Glyphidops (Oncopsia) flavifrons (Bigot, 1886), which has one of the broadest distributions of Neriidae in southern North America, Central America, and South America; offering excellent(More)
The mass matrices of the charged leptons and neutrinos, previously derived in a minimal S3-invariant extension of the Standard Model, were reparametrized in terms of their eigenvalues. We obtained explicit, analytical expressions for all entries in the neutrino mixing matrix, VP M NS , the neutrino mixing angles and the Majorana phases as functions of the(More)