Isabel Usón

Institut de Biologia Molecular de Barcelona

Life & Medical Sciences

Isabel Usón Finkenzeller completed a Chemistry degree (1987) and Ph. D. (1992) in synthetic organometallic chemistry at the U. of Zaragoza. In November 1992, she joined Procter & Gamble as Product Research Scientist in Brussels, gaining insight into the science and management of industrial chemistry. She moved as HCM postdoc to the U. of Göttingen in 1994. She has developed methods for crystallography for 23 years, first within the group of Prof. Sheldrick FRS, author of SHELX, during her postdoctoral research and Habilitation (1994-2001) and as of July 2001 leading an emergent group. September 2003, she moved to Barcelona as ICREA Research Professor. Her work on structural chemistry and biology has led to over 150 publications. The software ARCIMBOLDO and SHELX are the central output of her work. She is one of the 7 members of the Maria de Maeztu Excellence Unit of Structural Biology at IBMB-CSIC.

Research interests

Macromolecular crystallography provides conclusive structural info. down to atomic detail and has been inextricable from major advances in the life sciences. Nevertheless, this structural model cannot be directly calculated from the experimental data, as we cannot measure the phases of the diffracted X-ray beams. Our group develops methods to exploit the stereochemical knowledge present in small, accurate units such as secondary structure fragments and their association into local folds. Their use to solve the central phase problem of crystallography is implemented in our software ARCIMBOLDO. This has required devising our own particular toolbox for fragments. We are extending this detailed view to map interpretation within the program SHELXE (Sheldrick) and general structure interpretation within our program BORGES_MATRIX. Also, we are extending our work into electron diffraction. As illustrated in paintings by G. Arcimboldo, the information content derived from a correct combination of fragments goes beyond their simple addition.

Selected publications

- Gordo V, Aparicio D, Perez-Luque R, Benito A, Vilanova M, Usón I, Fita I* & Ribó M* 2018, 'Structural insights into subunits assembly and the oxyester splicing mechanism of Neq pol split intein', Cell Chem. Biol., 25, P871-879.E2

- Usón I & George M 2018, 'SheldrickAn introduction to experimental phasing of macromolecules illustrated by SHELX; new autotracing features', Acta Cryst D74, 106-116

- Caballero I, Sammito M, Millán C, Lebedev A, Soler N & Usón I* 2018, 'ARCIMBOLDO on Coiled Coils', Acta Cryst D. 74194-204

- Oeffner RD,Afonine PV, Millan C, Sammito M, Uson I, Read RJ & McCoy AJ 2018, 'On the application of the expected log-likelihood gain to decision making in molecular replacement', Acta Cryst. D74, 245-255

- Lee M, Batuecas MT, Tomoshige S, Domínguez-Gil T, Mahasenan KV, Dik DA, Hesek D, Millán C, Usón I, Lastochkin E, Hermoso JA & Mobashery S 2018, 'Exolytic and endolytic turnover of peptidoglycan by lytic transglycosylase Slt of Pseudomonas aeruginosa', Proceedings of the National Academi of Sciences, 115:4393-4398.

- McCoy AJ, Oeffner RD, Millan C, Sammito M, Uson I & Read RJ  2018, 'Gyre and gimble: a maximum-likelihood replacement for Patterson correlation refinement', Acta Crystallographica Section D-structural Biology, 74, 4, 279 - 289.

- Dunce JM, Dunne OM, Ratcliff M, Millán C, Madgwick S, Usόn I & Davies OR 2018, 'Structural basis of meiotic chromosome synapsis through SYCP1 self-assembly',  Nature Structural & Molecular Biology 25, pages557–569.

Selected research activities

Organisation of the session "New approaches to structure solution by Crystallography and CryoEM: Computational features and new algorithms" at the European Crystallographic Meeting Congress XXXI.

Invited lecture “All is fair in phasing: the combined artillery in ARCIMBOLDO“ in “Combining methods in macromolecular structure determination, including special conditions” 22-27 August 2018, Oviedo (Spain).

Research Stay July-August at CIMR, University of Cambridge.