Russian Journal of Bioorganic Chemistry, Vol. 31, No. 3, 2005, pp. 297–299. Translated from Bioorganicheskaya Khimiya, Vol. 31, No. 3, 2005, pp. 331–334.
Original Russian Text Copyright © 2005 by Boldyrev, Molotkovsky.
LETTERS
TO THE EDITOR
A Synthesis of New Rigid Fluorescent Bichromophoric Probes
for Studying Mechanisms of Donor–Donor Energy Migration
1
I. A. Boldyrev and Jul. G. Molotkovsky
Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences,
ul. Miklukho-Maklaya 16/10, Moscow, 117997 Russia
Received December 29, 2004; in final form, January 13, 2005
Abstract—Three new fluorescent probes were synthesized for improving the method of studying donor–donor
energy migration (DDEM). Each probe has two identical fluorescent 7-diethylaminocoumarin-3-carbonyl
groups attached to a rigid bisteroid dodecacyclic spacer through additional inserts. In two probes, the inserts
are β-Ala and L-Ser residues, which provide for a different nearest environment of the fluorophores. The third
probe has identical β-Ala inserts.
Key words: DDEM, fluorescent bichromophoric probes, fluorescence spectra, synthesis
1
We had previously reported [1, 2] the synthesis of a Ser residue [in probe (VIII)]; in turn, they are situated
series of fluorescent bichromophoric probes intended at two opposite sides of the rigid decacyclic system (the
for studying the migration of excitation energy between so-called bisteroid [7]). Therefore, equal fluorophores
2
fluorophores in model systems (for a review, see [3]).
have the different nearest surroundings represented by
an additional acetoxy (VII) or a hydroxyl group (VIII).
In addition, probe (V) was obtained as a comparison
standard; the two fluorophores attached to β-Ala spac-
ers are there in equal environment. Strictly speaking,
some differences also are here, since the bisteroid mol-
ecule is asymmetric in its central part; however, these
differences are so insignificant that show no influence
on the photophysical properties of fluorophores [1].
The development of the DDEM method required a
consideration of conditions at which energy migrates
between the fluorophores placed in different environ-
ment. It is these situations that take place in the major-
ity of biological and model systems. The energy migra-
tion is partially reversible in such asymmetric (from the
photophysical point of view) systems. The PDDEM
model has been suggested for its description [4]. The
use of this model and the probes synthesized [1, 2]
helped measure some membrane parameters, in partic-
ular, the thickness of liposomal bilayer in which the
same (rhodaminyl or fluoresceinyl) fluorophores were
at its different sides [5, 6].
Sophisticated bifluorophoric probes, in which the
same fluorophore is primarily present at two different
surroundings, i.e., in the neighborhood of grouping
with different polarity, are necessary for a further
improvement of the PDDEM method. The study of
PDDEM in such probes embedded in various media
permit the establishment of regularities of the phenom-
enon under study.
The choice of DEAC residue as a fluorophore was
dictated by the fact that DEAC easily acylates amino
groups and the resulting derivatives retain good quan-
tum yields [8]. The fluorescence parameters of DEAC
group are very sensitive to the polarity of environment,
as in the case of the majority of other polar fluoro-
phores. Moreover, the position of the excitation maxi-
mum of DEAC derivatives (420–425 nm) allows the
use of DEAC group for the acception of excitation
energy of protein fluorophores, which broadens the
potentialities of DEAC probes in studying lipid–protein
interactions. A number of laboratories are studying the
modification of DEAC with the purpose of design of
new fluorophores and probes on their basis (see [9] and
references therein).
We describe here the synthesis of such probes (see
the scheme). Each of compounds (VII) and (VIII) has
two equal fluorophores, DEAC residues, attached to
amino groups of different spacers: β-Ala residues (in
both probes), and a O-acetylserine [in probe (VII)] or a
The distance between fluorophores directly bound
to the bisteroid is approximately 20 Å [7]. Additional
spacers, the β-Ala and Ser residues, increases this dis-
tance to ~30 Å (in the extended conformation of probe).
This value is close to an average thickness of membrane
bilayer. Therefore, both fluorophores of the probe
would be located in the region of polar head groups on
the opposite sides of membrane, when bifluorophoric
probes (V), (VII), and (VIII) were normally oriented to
1
Corresponding author; phone/fax: +7 (095) 330-6601; e-mail:
2
Abbreviations:
BOP,
(benzotriazol-1-yloxy)-tris(dimethyl-
amine)phosphonium; and DDEM, donor–donor energy migra-
tion; DEAC, 7-diethylaminocoumarin-3-carboxylic acid;
PDDEM, partial donor–donor energy migration.
1068-1620/05/3103-0297 © 2005 Pleiades Publishing, Inc.