J. Biol. Chem., Vol. 259, Issue 2, 1105-1109, 01, 1984
Close range interactions between nucleotide bases and tryptophan residues in an Escherichia coli single-stranded DNA binding protein- mercurated poly(uridylic acid) complex. A study by optically detected magnetic resonance spectroscopy
TA Cha and AH Maki
Optically detected triplet state magnetic resonance spectra are reported
for the complex formed between mercurated poly(Urd) and Escherichia coli
single-stranded DNA binding protein. Upon forming a complex, the triplet
state properties of Trp residue(s) in the protein are perturbed by the
heavy mercury atom and are characterized by a shortened triplet state
lifetime and the appearance of a strong D + E slow passage optically
detected magnetic resonance signal. These features, which signal an
external heavy atom effect, provide direct evidence for a close range
interaction between mercurated nucleotide bases and Trp residues owing to
the requirement of a van der Waals contact between the perturbed molecule
and the heavy atom perturber. The amplitude-modulated phosphorescence
microwave double resonance technique selectively displays the
phosphorescence spectrum of the heavy atom-perturbed Trp triplet states. A
van der Waals contact manifested through a stacked structure of the
mercurated uridine base and the indole moiety of Trp is strongly suggested
as the most plausible mode of interaction from steric considerations, since
other approaches of the mercury atom are blocked by the covalent attachment
of 2-mercaptoethanol to mercury. The magnitude of the heavy atom
perturbation also is consistent with Hg approach to the pi-system from
above or below the indole aromatic plane, and is at least an order of
magnitude larger than effects expected from an edge-on approach.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
