Linked Life Data

18293344

Source:http://linkedlifedata.com/resource/pubmed/id/18293344

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
2008-3-12
pubmed:abstractText
Complexes of PheAla and AlaPhe with alkali metal ions Na(+) and K(+) are generated by electrospray ionization, isolated in the Fourier-transform ion cyclotron resonance (FT-ICR) ion trapping mass spectrometer, and investigated by infrared multiple-photon dissociation (IRMPD) using light from the FELIX free electron laser over the mid-infrared range from 500 to 1900 cm(-1). Insight into structural features of the complexes is gained by comparing the obtained spectra with predicted spectra and relative free energies obtained from DFT calculations for candidate conformers. Combining spectroscopic and energetic results establishes that the metal ion is always chelated by the amide carbonyl oxygen, whilst the C-terminal hydroxyl does not complex the metal ion and is in the endo conformation. It is also likely that the aromatic ring of Phe always chelates the metal ion in a cation-pi binding configuration. Along with the amide CO and ring chelation sites, a third Lewis-basic group almost certainly chelates the metal ion, giving a threefold chelation geometry. This third site may be either the C-terminal carbonyl oxygen, or the N-terminal amino nitrogen. From the spectroscopic and computational evidence, a slight preference is given to the carbonyl group, in an RO(a)O(t) chelation pattern, but coordination by the amino group is almost equally likely (particularly for K(+)PheAla) in an RO(a)N(t) chelation pattern, and either of these conformations, or a mixture of them, would be consistent with the present evidence. (R represents the pi ring site, O(a) the amide oxygen, O(t) the terminal carbonyl oxygen, and N(t) the terminal nitrogen.) The spectroscopic findings are in better agreement with the MPW1PW91 DFT functional calculations of the thermochemistry compared with the B3LYP functional, which seems to underestimate the importance of the cation-pi interaction.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
1439-7641
pubmed:author
pubmed:issnType
Electronic
pubmed:day
14
pubmed:volume
9
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
579-89
pubmed:meshHeading
pubmed:year
2008
pubmed:articleTitle
Alkali metal complexes of the dipeptides PheAla and AlaPhe: IRMPD spectroscopy.
pubmed:affiliation
Chemistry Department, University of Florida, Gainesville, FL 32611, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't