TY - JOUR
T1 - Physico-chemical evaluation of rationally designed melanins as novel nature-inspired radioprotectors
AU - Schweitzer, Andrew D.
AU - Howell, Robertha C.
AU - Jiang, Zewei
AU - Bryan, Ruth A.
AU - Gerfen, Gary
AU - Chen, Chin Cheng
AU - Mah, Dennis
AU - Cahill, Sean
AU - Casadevall, Arturo
AU - Dadachova, Ekaterina
PY - 2009/9/30
Y1 - 2009/9/30
N2 - Background: Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melanized microorganisms against high doses of ionizing radiation. However, the physics of melanin interaction with ionizing radiation is unknown. Methodology/Principal Findings: We rationally designed melanins from either 5-S-cysteinyl-DOPA, L-cysteine/L-DOPA, or LDOPA with diverse structures as shown by elemental analysis and HPLC. Sulfur-containing melanins had higher predicted attenuation coefficients than non-sulfur-containing melanins. All synthetic melanins displayed strong electron paramagnetic resonance (2.14.1018, 7.09.1018, and 9.05.1017 spins/g, respectively), with sulfur-containing melanins demonstrating more complex spectra and higher numbers of stable free radicals. There was no change in the quality or quantity of the stable free radicals after high-dose (30,000 cGy), high-energy (137Cs, 661.6 keV) irradiation, indicating a high degree of radical stability as well as a robust resistance to the ionizing effects of gamma irradiation. The rationally designed melanins protected mammalian cells against ionizing radiation of different energies. Conclusions/Significance: We propose that due to melanin's numerous aromatic oligomers containing multiple p-electron system, a generated Compton recoil electron gradually loses energy while passing through the pigment, until its energy is sufficiently low that it can be trapped by stable free radicals present in the pigment. Controlled dissipation of high-energy recoil electrons by melanin prevents secondary ionizations and the generation of damaging free radical species.
AB - Background: Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melanized microorganisms against high doses of ionizing radiation. However, the physics of melanin interaction with ionizing radiation is unknown. Methodology/Principal Findings: We rationally designed melanins from either 5-S-cysteinyl-DOPA, L-cysteine/L-DOPA, or LDOPA with diverse structures as shown by elemental analysis and HPLC. Sulfur-containing melanins had higher predicted attenuation coefficients than non-sulfur-containing melanins. All synthetic melanins displayed strong electron paramagnetic resonance (2.14.1018, 7.09.1018, and 9.05.1017 spins/g, respectively), with sulfur-containing melanins demonstrating more complex spectra and higher numbers of stable free radicals. There was no change in the quality or quantity of the stable free radicals after high-dose (30,000 cGy), high-energy (137Cs, 661.6 keV) irradiation, indicating a high degree of radical stability as well as a robust resistance to the ionizing effects of gamma irradiation. The rationally designed melanins protected mammalian cells against ionizing radiation of different energies. Conclusions/Significance: We propose that due to melanin's numerous aromatic oligomers containing multiple p-electron system, a generated Compton recoil electron gradually loses energy while passing through the pigment, until its energy is sufficiently low that it can be trapped by stable free radicals present in the pigment. Controlled dissipation of high-energy recoil electrons by melanin prevents secondary ionizations and the generation of damaging free radical species.
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U2 - 10.1371/journal.pone.0007229
DO - 10.1371/journal.pone.0007229
M3 - Article
C2 - 19789711
AN - SCOPUS:70349649776
SN - 1932-6203
VL - 4
JO - PloS one
JF - PloS one
IS - 9
M1 - e7229
ER -