Biomaterial Database

Metal cation binding to gas-phase pentaalanine: divalent ions restructure the complex. 2013

Robert C Dunbar, and Jeffrey D Steill, and Nicolas C Polfer, and Jos Oomens

Chemistry Department, Case Western Reserve University, Cleveland, Ohio 44106, USA. rcd@po.cwru.edu

Ion-neutral complexes of pentaalalanine with several singly- and doubly charged metal ions are examined using conformation analysis by infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) computations. The infrared spectroscopy in the 1500-1800 cm(-1) region is found to be conformationally informative; in particular, the frequency of the C═O stretching mode of the terminal carboxyl group is diagnostic for hydrogen bonding of the terminal hydroxyl. The doubly charged alkaline earth metal ions (Ca(2+) and Ba(2+)) enforce a highly structured chelation shell around the metal ion, with six strongly bound Lewis-basic chelation sites, and no hydroxyl hydrogen bonding. With the more weakly binding alkali metal ions (Na(+), K(+), and Cs(+)), structures with intramolecular hydrogen bonds are more favorable, leading to dominance of conformations with lower degrees of metal ion chelation. The favored coordination mode correlates with ionic charge and binding strength but is not related to the ionic radius of the metal ion.

UI	MeSH Term	Description	Entries
D007477	Ions	An atom or group of atoms that have a positive or negative electric charge due to a gain (negative charge) or loss (positive charge) of one or more electrons. Atoms with a positive charge are known as CATIONS; those with a negative charge are ANIONS.
D008672	Metals, Alkali	Metals that constitute group 1(formerly group IA) of the periodic table. They are the most strongly electropositive of the metals. Note that HYDROGEN is not considered an alkali metal even though it falls under the group 1 heading in the periodic table.	Alkali Metal,Alkali Metals,Group 1 Element,Group 1 Elements,1 Element, Group,Element, Group 1,Elements, Group 1,Metal, Alkali
D008673	Metals, Alkaline Earth	Metals that constitute the group 2 (formerly group IIA) of the periodic table.	Alkaline Earth Metal,Alkaline Earth Metals,Group 2 Element,Group 2 Elements,2 Element, Group,Earth Metal, Alkaline,Earth Metals, Alkaline,Element, Group 2,Elements, Group 2,Metal, Alkaline Earth
D008958	Models, Molecular	Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.	Molecular Models,Model, Molecular,Molecular Model
D011789	Quantum Theory	The theory that the radiation and absorption of energy take place in definite quantities called quanta (E) which vary in size and are defined by the equation E	Quantum Theories,Theories, Quantum,Theory, Quantum
D002412	Cations	Positively charged atoms, radicals or groups of atoms which travel to the cathode or negative pole during electrolysis.	Cation
D005740	Gases	The vapor state of matter; nonelastic fluids in which the molecules are in free movement and their mean positions far apart. Gases tend to expand indefinitely, to diffuse and mix readily with other gases, to have definite relations of volume, temperature, and pressure, and to condense or liquefy at low temperatures or under sufficient pressure. (Grant & Hackh's Chemical Dictionary, 5th ed)
D006860	Hydrogen Bonding	A low-energy attractive force between hydrogen and another element. It plays a major role in determining the properties of water, proteins, and other compounds.	Hydrogen Bonds,Bond, Hydrogen,Hydrogen Bond
D000409	Alanine	A non-essential amino acid that occurs in high levels in its free state in plasma. It is produced from pyruvate by transamination. It is involved in sugar and acid metabolism, increases IMMUNITY, and provides energy for muscle tissue, BRAIN, and the CENTRAL NERVOUS SYSTEM.	Abufène,Alanine, L-Isomer,L-Alanine,Alanine, L Isomer,L Alanine,L-Isomer Alanine
D001665	Binding Sites	The parts of a macromolecule that directly participate in its specific combination with another molecule.	Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining