Document Detail


Protection of melanized Cryptococcus neoformans from lethal dose gamma irradiation involves changes in melanin's chemical structure and paramagnetism.
MedLine Citation:
PMID:  21966422     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Certain fungi thrive in highly radioactive environments including the defunct Chernobyl nuclear reactor. Cryptococcus neoformans (C. neoformans), which uses L-3,4-dihydroxyphenylalanine (L-DOPA) to produce melanin, was used here to investigate how gamma radiation under aqueous aerobic conditions affects the properties of melanin, with the aim of gaining insight into its radioprotective role. Exposure of melanized fungal cell in aqueous suspensions to doses of γ-radiation capable of killing 50 to 80% of the cells did not lead to a detectable loss of melanin integrity according to EPR spectra of melanin radicals. Moreover, upon UV-visible (Xe-lamp) illumination of melanized cells, the increase in radical population was unchanged after γ-irradiation. Gamma-irradiation of frozen cell suspensions and storage of samples for several days at 77 K however, produced melanin modification noted by a reduced radical population and reduced photoresponse. More direct evidence for structural modification of melanin came from the detection of soluble products with absorbance maxima near 260 nm in supernatants collected after γ-irradiation of cells and cell-free melanin. These products, which include thiobarbituric acid (TBA)-reactive aldehydes, were also generated by Fenton reagent treatment of cells and cell-free melanin. In an assay of melanin integrity based on the metal (Bi(+3)) binding capacity of cells, no detectable loss in binding was detected after γ-irradiation. Our results show that melanin in C. neoformans cells is susceptible to some damage by hydroxyl radical formed in lethal radioactive aqueous environments and serves a protective role in melanized fungi that involves sacrificial breakdown.
Authors:
Abdelahad Khajo; Ruth A Bryan; Matthew Friedman; Richard M Burger; Yan Levitsky; Arturo Casadevall; Richard S Magliozzo; Ekaterina Dadachova
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2011-09-22
Journal Detail:
Title:  PloS one     Volume:  6     ISSN:  1932-6203     ISO Abbreviation:  PLoS ONE     Publication Date:  2011  
Date Detail:
Created Date:  2011-10-03     Completed Date:  2012-02-10     Revised Date:  2013-06-27    
Medline Journal Info:
Nlm Unique ID:  101285081     Medline TA:  PLoS One     Country:  United States    
Other Details:
Languages:  eng     Pagination:  e25092     Citation Subset:  IM    
Affiliation:
Department of Chemistry, Brooklyn College of the City University of New York, Brooklyn, New York, United States of America.
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MeSH Terms
Descriptor/Qualifier:
Cryptococcus neoformans / metabolism*,  radiation effects*
Gamma Rays / adverse effects*
Hydroxyl Radical / metabolism
Melanins / chemistry*,  metabolism*
Grant Support
ID/Acronym/Agency:
AI52733/AI/NIAID NIH HHS
Chemical
Reg. No./Substance:
0/Melanins; 3352-57-6/Hydroxyl Radical
Comments/Corrections

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