[ RadSafe ] 'Pinball protons' created by ultraviolet rays and other causes can lead to DNA damage

[John Jacobus]

Roy,
Thanks for posting this.  I assume that the
"explusion" of the proton from the Guanine-Cytosine
(G-C) base pair is due to the deposited energy of the
UV radiation.  It provides insight into mutation
beyond the creation of thymine dimers by UV radiation.
 
http://www.emunix.emich.edu/~rwinning/genetics/mutat3.htm


--- ROY HERREN <royherren2005 at yahoo.com> wrote:

>  Public release date: 17-May-2006
> 
> Contact: Kim Carlyle
> kcarlyle at uga.edu
> 706-542-8083
> University of Georgia 
>   'Pinball protons' created by ultraviolet rays and
> other causes can lead to DNA damage  Researchers
> have known for years that damaged DNA can lead to
> human diseases such as cancer, but how damage
> occurs--and what causes it--has remained less clear.
>   Now, computational chemists at the University of
> Georgia have discovered for the first time that when
> a proton is knocked off one of the pairs of bases
> that make up DNA, a chain of damage begins that
> causes "lesions" in the DNA. These lesions, when
> replicated in the copying mechanisms of DNA, can
> lead to serious disorders such as cancer.   The
> research, just published in the Proceedings of the
> National Academy of Sciences (PNAS), was led by
> doctoral student Maria Lind and Henry F. Schaefer
> III, Graham-Perdue Professor of Chemistry. Other
> authors on the paper are doctoral student Partha
> Bera, postdoctoral associate Nancy Richardson and
> recent doctoral graduate Steven Wheeler.   Call it a
> "pinball proton." While chemists have
>  shown other causes of DNA damage, the report in
> PNAS is the first to report how protons, knocked
> away by such mechanisms as radiation or chemical
> exposure, can cause lesions in DNA. The work was
> done entirely on computers in the Center for
> Computational Chemistry, part of the Franklin
> College of Arts and Sciences at UGA.   "This kind of
> damage in DNA subunits is about as basic as you can
> get," said Schaefer. "This is the simplest kind of
> lesion possible for such a system."   The
> double-helix structure of DNA has been known for
> more than half a century. This basic building block
> of life can "unzip" itself to create copies, a
> process at the heart of cell replication and growth.
> DNA is made of four "bases," Adenine, Guanine,
> Thymine and Cytosine, and each one pairs with its
> opposite to form bonds where the "information" of
> life is stored. Thus, Guanine pairs with Cytosine,
> and Thymine with Adenine.   The team at the
> University of Georgia studied how the removal of a
> proton
>  from the Guanine-Cytosine (G-C) base pair is
> involved in creating lesions that can lead to
> replication errors. This pair has 10 protons,
> meaning there are numerous targets for processes
> that knock the protons off.   The lesions are breaks
> in the hydrogen bonds, of which there are two in the
> G-C base pair. (The Adenine-Thymine pair has three
> hydrogen bonds.)   "Our real goal is to examine all
> possible lesions in DNA subunits," said Lind.   The
> team discovered that the base pair minus its
> knocked-off proton can either break entirely or
> change its bonding angle--something that also causes
> improper replication.   "The C-G subunit is usually
> totally planar [flat]," said Lind. "If it twists, it
> could simply pull apart."   Though it has already
> been suspected that lesions in DNA caused by both
> high- and low-energy electrons result in cancer cell
> formation, the new study is the first evidence that
> protons do the same thing.   The study in PNAS also
> has other implications.
>  Researchers are beginning to understand how DNA can
> be used as "molecular wire" in constructing
> electrical circuits. Such a breakthrough would allow
> small electronic devices to shrink even further, but
> how the electrical properties of DNA would work in
> such a context is not yet understood. The UGA
> research adds important knowledge about how
> so-called "deprotonated" DNA base pairs work and
> could be important in creating "DNA wire."     ###
>   The research was supported by a grant from the
> National Science Foundation. 
> 
> 
> Roy Herren
> 			
> ---------------------------------
> Sneak preview the  all-new Yahoo.com. It's not
> radically different. Just radically better. 
> _______________________________________________
> You are currently subscribed to the RadSafe mailing
> list
> 
> Before posting a message to RadSafe be sure to have
> read and understood the RadSafe rules. These can be
> found at: http://radlab.nl/radsafe/radsaferules.html
> 
> For information on how to subscribe or unsubscribe
> and other settings visit: http://radlab.nl/radsafe/
> 


+++++++++++++++++++
"People will be shocked to see how safe it is to live in New York City."
ANDREW KARMEN, a sociology professor at John Jay College of Criminal Justice, on murder trends in the city.

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com