Syn-Bimane based fluorescent molecular sensor
Inbal Lapidot[1,2], Amnon Albeck[2], and Shimon Shatzmiller [1]
[1] Ariel University, Ariel 40700, Israel
[2] Bar-Ilan University, Max ve-Anna Webb, Ramat-Gan, 52900, Israel
There is a great need for early diagnosis and follow-up of neurodegenerative brain disorders1. Examples
are the incurable fatal Alzheimer's, Creutzfeldt-Jakob and Parkinson's diseases. This, in the recent
attempts to approach the early diagnosis, is by shining light on fluorescent biomarkers that will indicate
the existence of the diseases initiators – the polypeptide misfolded aggregates (amyloid-beta [Aβ], αsynuclein and tau—proteins) for example. Those slowly accumulating around the nerve systems and
facilitate the apoptosis of the living neurons2.
The administration of the biomarker-agent into the blood stream is needed. Gazit and collaborators have
shown that an un-natural di-peptide [D-Trp-Aib] is able to cross the BBB and stain brain tissue3. The
presence of the 2-amino-2-methylpropanoic acid moiety [Aib] may enable such BBB crossing4.
However, in case of future application of such molecular structure to brain diagnosis, the Trp moiety
may become not applicable since its photo-physical properties, namely absorbing UV light and
florescence spectrum are undistinguishable from the aromatic units present already in the brain in the
natural polypeptides like Amyloid beta (Aβ)5. It seemed to us that a suitable laser dye based molecule
that could enter the brain by crossing the blood brain barrier (BBB) might be useful in developing of
future sensors for the early detection of brain neurodegenerative disorders that could be applied on the
basis of the syn- bimane system [2,3,5,6-tetramethylpyrazolo[1,2-a]pyrazole-1,7-dione].
We have designed the bimanyl analog which is a fluorescent marker and laser dye with absorption and
fluorescence properties that are unique and could be instrumental in an environment of the proteogenic
aromatic amino acids present in living tissues6. In order to apply the syn- bimane moiety, the presence of
the allylic S atom in the fluorescent moiety is needed to apply the bimane fluorescent unit which is
essentially non-fluorescent until conjugated7. This is needed for a strong fluorescent behaviour of the
agent 8. The molecule was injected to the tails of laboratory mice and could be detected in the inner brain
hippocampus gland of the animals showing green fluorescence applying fluorescent microscopy.
References
.1
Risacher, S. L.; Saykin, A. J., Neuroimaging and other biomarkers for Alzheimer's disease: the changing landscape of
early detection. Annual review of clinical psychology 2013, 9, 621-648.
.2
Soto, C., Unfolding the role of protein misfolding in neurodegenerative diseases. Nature Reviews Neuroscience 2003,
4 (1), 49-60.
.3
Frydman‐Marom, A.; Rechter, M.; Shefler, I.; Bram, Y.; Shalev, D. E.; Gazit, E., Cognitive‐Performance Recovery of
Alzheimer's Disease Model Mice by Modulation of Early Soluble Amyloidal Assemblies. Angewandte Chemie 2009, 121 (11),
2015-2020.
.4
(a) Shapiro, W. R.; Hiesiger, E. M.; Cooney, G. A.; Basler, G. A.; Lipschutz, L. E.; Posner, J. B., Temporal effects of
dexamethasone on blood-to-brain and blood-to-tumor transport of 14C-alpha-aminoisobutyric acid in rat C6 glioma. Journal of
neuro-oncology 1990, 8 (3), 197-204; (b) Blasberg, R. G.; Fenstermacher, J. D.; Patlak, C. S., Transport of α-aminoisobutyric acid
across brain capillary and cellular membranes. Journal of Cerebral Blood Flow & Metabolism 1983, 3 (1), 8-32; (c) Betz, A.;
Goldstein, G. W., Polarity of the blood-brain barrier: neutral amino acid transport into isolated brain capillaries. Science 1978, 202
(4364), 225-227.
.5
(a) Lakowicz, J. R., Principles of fluorescence spectroscopy. Springer: 2009; (b) Warburg, O.; Christian, W., Insulation
and Crystalisation of the Fermenting Process of Enolase. Biochem Z 1942, 310 (6), 384-421.
.6
Radkowsky, A. E.; Kosower, E. M., Bimanes. 17.(Haloalkyl)-1, 5-diazabicyclo [3.3. O] octadienediones (halo-9, 10dioxabimanes): reactivity toward the tripeptide thiol, glutathione. Journal of the American Chemical Society 1986, 108 (15), 45274531.
.7
(a) Kosower, N. S.; Kosower, E. M.; Newton, G. L.; Ranney, H. M., Bimane fluorescent labels: labeling of normal
human red cells under physiological conditions. Proceedings of the National Academy of Sciences 1979, 76 (7), 3382-3386; (b)
Graham, D. E.; Harich, K. C.; White, R. H., Reductive dehalogenation of monobromobimane by tris (2-carboxyethyl) phosphine.
Analytical biochemistry 2003, 318 (2), 325-328.
.8
Pavlopoulos, T. G.; Boyer, J. H.; Politzer, I. R.; Lau, C. M., Syn-dioxabimanes as laser dyes I. Optics communications
1987, 64 (4), 367-372.