Biology Reference
In-Depth Information
GFP
−like chromophore
O
_
O
R
1
R
1
N
N
N
N
_
O
O
R
2
R
2
II
I
RFP−like chromophore
O
_
O
R
1
R
1
N
N
N
N
O
_
O
N
N
I
II
R
2
O
R
2
O
R
3
R
3
O
R
1
N
N
O
N
III
O
_
R
2
R
3
Fig. 6 Resonance forms of the anionic states of GFP chromophore (
top
) and DsRed chromophore
(
bottom
)
5.1 Proteins with GFP Chromophore
The electronic excitation mostly involves the chromophore region supporting the
electronic
-conjugated system. In the GFP-like chromophores, this encompasses
the phenolic ring and the imidazolinone, while the side chain of the first position in
the tripeptide is not included. Hence, it is justified to consider proteins with a
different residue at this position as having the “same” chromophore, as long as it
does not undergo additional maturation reactions (like, for instance, the acylimine
formation in RFP chromophore).
Starting from the anionic protonation state, Table
5
reports absorption and
emission peaks of the anionic form in different representative proteins all contain-
ing a GFP-like chromophore (GFPa), together with the nature of the residues
surrounding the chromophore at various positions. The proteins can be grouped
according to their absorption/emission features in cyan/teal, green, and yellow. In
order to specify equivalent positions in the sequences of these homologues, we will
use the
av
prefix, referring to the corresponding position in
av
GFP after sequence
p
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