1 / 7

F. Scappini (2), M. Franchi (3), E. Gallori (3), C. Cecchi-Pestellini (4), M. Barbera (1),

The Role of Clays in Shielding DNA against X-Ray Radiation: Possible Implications on the origin of life Angela Ciaravella. F. Scappini (2), M. Franchi (3), E. Gallori (3), C. Cecchi-Pestellini (4), M. Barbera (1),

Download Presentation

F. Scappini (2), M. Franchi (3), E. Gallori (3), C. Cecchi-Pestellini (4), M. Barbera (1),

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The Role of Clays in Shielding DNA against X-Ray Radiation: Possible Implications on the origin of life AngelaCiaravella • F. Scappini (2), M. Franchi (3), E. Gallori (3), C. Cecchi-Pestellini (4), M. Barbera (1), • R. Candia (1), G. Micela (1) • INAF – Osservatorio Astronomico di Palermo , Italy • ISMN –CNR , Bologna, Italy • Dipartimento di Biologia Animale e Genetica, Univ. di Firenze, Italy • Dipartimento di Fisica, Univ di Lecce, Italy Firenze 28/02 – 1/03/05

  2. Conditions on the Early Earth How and under which conditions life was created? First evidence of life on the Earth 3.8 × 109 yr Earth Atmosphere : a big unknow, very little screening from Sun radiation Early X-ray Sun: more active, hard and bright 3 × 1026 (0.1 keV) < Lx >= 1027 erg/sec 5 × 1027 (0.2 keV) Yohkoh-SXT 3-40 Å band 1-10 keV band: the photon flux today is ~10-3 the flux at the age of Pleiades Sun @ max Sun @ min

  3. B A 34 Å per turn 27-28 Å per turn DNA Irradiation Why DNA? DNA is already life  An easy and well tested method to estimate damage We irradiate free and clay absorbed DNA from Bacillus Subtilis CLAYS: Montmorillonite Na0.2Ca0.1Al2Si4O10(OH)2(H2O)10 Kaolinite Al2Si2O5(OH)4 Free DNA type B Clay Adsorbed DNA type A

  4. DNA X-Ray Irradiation Line (keV) Flux (erg sec-1 cm -2 ) Al 1.49 0.15 Ti 4.51 0.17 Cu 8.04 0.20 10-5 minimum 3 × 10-3 maximum 10-1 large flares The Sun today (1.5 –12.4 keV): DNA Samples: Free 10μg DNA + 1400l of H2O Clay Adsorbed 10μg DNA + 2mg Clay + 1400l of H2O The XACT Facility: X-ray, UV, Vis 2 -104 eV (1- 7000 A). 17 m stainless-steel vacum beam line class 1000 clean_room (Barbera et al 1999). Vacuum tight container Irradiation Dose : 102-5.8 × 104 erg Exposure Time : 2m - 16h

  5. DNA Damage Evaluation Transformation frequence for non irradiated DNA The integrity of DNA molecules is estimated by transformation experiments : efficiency of irradiated DNA to transform competent cell in a bacterial culture The transformation frequence is: Typical errors onFtf are 20 % Comparing Ftf with Ftf0 the damage is evaluated

  6. Results and Conclusions I ⃟ ⃟ ⃟ ⅏ ⅏⅏ Clay Adsorbed DNA is resistent to the X-ray irradiation The more compact configuration (A) of clay adsorbed DNA binding to the substrate by electrostatic and/or hydrogen bonds can play protective role *** Free DNA is severely damaged by X-rays and the damage depends on the energy dose rather than the hardness of radiation Can clays shield DNA against X-rays? Diluted clay is much more transparent than H2O to X-rays

  7. Results and Conclusions II 2.5 mm Num X photons (Cu 5 × 104 erg) 4 × 1012 Num H2O molecules 5 × 1022 Num DNA molecules 4 × 1011 1 mm 0.2 mm 0.01 mm Are X-rays directly responsible for DNA damage? Secondary UV UV irradiation of free and clay adsorbed DNA give similar results(Scappini et al 2004) DNA adsorbed on clays do survive X-rays and UV photodegradation Are clays essential in protecting the basic building blocks of life as well ?

More Related