When a proton the bare nucleus of a hydrogen atom transfers from one molecule to another, or moves within a molecule, the result is a hydrogen bond, in which the proton and another atom like nitrogen or oxygen share electrons. Conventional wisdom has it that proton transfers can only happen using hydrogen bonds as conduits, "proton wires" of hydrogen-bonded networks that can connect and reconnect to alter molecular properties.
Hydrogen bonds are found everywhere in chemistry and biology and are critical in DNA and RNA, where they bond the base pairs that encode genes and map protein structures. Recently a team of researchers using the Advanced Light Source (ALS) at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) discovered to their surprise that in special cases protons can find ways to transfer even when hydrogen bonds are blocked. The team's results appear in Nature Chemistry.
Stacking the odd molecules
A group led by Musahid Ahmed, a senior scientists in Berkeley Lab's Chemical Sciences Division (CSD), has long collaborated with a theoretical research group at the University of Southern California (USC) headed by Anna Krylov. In recent work to understand how bases are bonded in staircase-like molecules like DNA and RNA, Krylov's group made computer models of paired, ring-shaped uracil molecules, and investigated what might happen to these doubled forms (dimers) when they were subjected to ionization the removal of one or more electrons with resulting net positive charge.
Uracil is one of the four nucleobases of RNA, whose structure is similar to DNA except that, while both use the bases adenine, cytosine, and guanine, in DNA the fourth base is thymine and in RNA it's uracil. The USC group used a uracil dimer labeled 1,3-dimethyluracil "a strange creature that doesn't necessarily exist in nature," says CSD's Amir Golan, who led the Berkeley Lab team at th
|Contact: Paul Preuss|
DOE/Lawrence Berkeley National Laboratory