Dipole Bound Clusters

  Adva Ben Yaacov  ,  Lihi Musbat  ,  Maria Nihamkin  ,  Dr. Yoni Toker  
Department of Physics and Institute of Nanotechnology, Bar-Ilan University, Ramat-Gan 5290002, Israel

Researchers have postulated about a link between the process of creating life by molecular assembly and clustering of amino acids. Therefore, extensive studies have been done in determining what the source of stability for amino acids clusters is. Clusters of amino acids often exhibit 'magic numbers'. Magic number is the number of molecules within a cluster for which there is high preference and due to the cluster having remarkable stability. For example, the Serine amino acids form preferentially clusters containing exactly eight molecules, and the structure of this magic octamer is under intense investigation. It is unknown whether amino acids in the gas phase are in the zwitterionic or neutral form. I therefore study clusters of a molecule N,N,N trimethylglycine, betaine, for which only the zwitterionic form exists. This molecule has an extraordinarily large constant dipole moment (11.9 Debye) which enables strong electrostatic interactions with neighboring molecules and formation of stable clusters in the gas phase. Through mass spectrometry measurements, I found that betaine clusters have a prominent magic number at size 4 regardless the ionic core attached to them. This is a unique finding as in most cases the structure and stability of charged cluster critically depends on the identity of the ionic core.