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<DIV style="FONT-FAMILY: 'Arial'; COLOR: #000000; FONT-SIZE: 10pt">Seminarios
DQIAQF - INQUIMAE, Lunes 08 de abril - 13 hs.<BR><BR>Aula de Seminarios INQUIMAE
- DQIAQF<BR>Facultad de Ciencias Exactas y Naturales<BR>Ciudad Universitaria -
Pab. 2 - Piso 3<BR><BR>
<P style="MARGIN: 6pt 0in 0pt; VERTICAL-ALIGN: baseline"><SPAN
lang=PT-BR>Understanding Catalysis by Heme Enzymes Starts with Their Active Site
Coordination Structure: Application of Magnetic Circular Dichroism Spectroscopy
to the Study of Novel Heme Proteins</SPAN></P>
<P style="MARGIN: 6pt 0in 0pt; VERTICAL-ALIGN: baseline"><SPAN lang=PT-BR>John
Dawson, University of South Carolina</SPAN></P>
<P style="MARGIN: 6pt 0in 0pt; VERTICAL-ALIGN: baseline"><SPAN
lang=PT-BR></SPAN> </P><SPAN style="FONT-FAMILY: ">Magnetic circular
dichroism spectroscopy provides diagnostic spectral data sensitive to the
identity of the axial ligands and to the spin and oxidation states of heme iron
centers in proteins.<SPAN> </SPAN>In this effort, we have found the
proximal ligand His93Gly myoglobin cavity mutant to be a remarkably versatile
scaffold for preparation of model heme complexes of defined
ligation.<SPAN> </SPAN>In particular, the difference in accessibility of
the two sides of the heme iron center offers the advantage of forming
ambient-temperature mixed-ligand heme model complexes, which are very difficult
to prepare with model systems in organic solvents.<SPAN> </SPAN>Moreover,
in the H93G Mb system, the protective environment provided by the protein allows
for the formation of relatively stable oxyferrous and ferryl [Fe(IV)=O]
complexes with variable ligands <I>trans</I> to the normally reactive dioxygen
and oxo substituents.<SPAN> </SPAN>Ferrous, ferric and ferryl His93Gly Mb
derivatives with various exogenous ligands have been prepared as models for
native heme iron active sites ligated by proximal Lys (amines), Asp or Glu
(carboxylates), Tyr (phenols), seleno-Cys (selenols), Cys (thiols) and Met
(thioethers).<SPAN> </SPAN>Building upon this foundation, we
have focused our attention on the use of the H93G Mb cavity mutant system to aid
our investigation of the coordination structure of novel heme binding and
transport proteins and heme-containing oxidative enzymes.<SPAN>
</SPAN>(Funding NIH GM 26730)</SPAN><BR><BR>****** <BR><BR>Professor
<SPAN>Dawson</SPAN> is Carolina Distinguished Professor and Chair of the
Department of Chemistry and Biochemistry at the University of South Carolina
with a joint appointment at the School of Medicine.<SPAN> </SPAN>Educated
at Columbia (A.B.) and Stanford (Ph.D.), he was an NIH postdoctoral fellow at
CalTech prior to his current appointment.<SPAN> </SPAN>An award-winning
researcher in bioinorganic chemistry, he has been author of over 210 research
publications and has given over 320 invited lectures at conferences and
universities worldwide.<SPAN> </SPAN>He is Editor of the <I>Journal of
Inorganic Biochemistry</I>, the oldest journal focused exclusively on
bioinorganic chemistry<I>.</I>
<P class=MsoNormal align=justify>He is best known for his investigations into
the active site structures and mechanisms of action of cytochrome P450 and of
novel halogenating and dehalogenating peroxidases.<SPAN> </SPAN>His
research has also demonstrated the importance of magnetic circular dichroism
spectroscopy in establishing the coordination structures of heme centers in
proteins.<SPAN> </SPAN></P><BR></DIV></DIV></BODY></HTML>