title: Differential sensitivity of Chironomus and human hemoglobin to gamma radiation.
abstract: Chironomus ramosus is known to tolerate high doses of gamma radiation exposure. Larvae of this insect possess more than 95% of hemoglobin (Hb) in its circulatory hemolymph. This is a comparative study to see effect of gamma radiation on Hb of Chironomus and humans, two evolutionarily diverse organisms one having extracellular and the other intracellular Hb respectively. Stability and integrity of Chironomus and human Hb to gamma radiation was compared using biophysical techniques like Dynamic Light Scattering (DLS), UV-visible spectroscopy, fluorescence spectrometry and CD spectroscopy after exposure of whole larvae, larval hemolymph, human peripheral blood, purified Chironomus and human Hb. Sequence- and structure-based bioinformatics methods were used to analyze the sequence and structural similarities or differences in the heme pockets of respective Hbs. Resistivity of Chironomus Hb to gamma radiation is remarkably higher than human Hb. Human Hb exhibited loss of heme iron at a relatively low dose of gamma radiation exposure as compared to Chironomus Hb. Unlike human Hb, the heme pocket of Chironomus Hb is rich in aromatic amino acids. Higher hydophobicity around heme pocket confers stability of Chironomus Hb compared to human Hb. Previously reported gamma radiation tolerance of Chironomus can be largely attributed to its evolutionarily ancient form of extracellular Hb as evident from the present study.
authors.affiliation: Stress Biology Research Laboratory, Department of Zoology, Savitribai Phule University, Pune, 411007, India; Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India.
authors.forename: Pallavi S
authors.initials: PS
authors.lastname: Gaikwad
authors.affiliation: Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India.
authors.forename: Lata
authors.initials: L
authors.lastname: Panicker
authors.affiliation: Bioinformatics Center, Savitribai Phule Pune University, Pune, 411007, India.
authors.forename: Madhura
authors.initials: M
authors.lastname: Mohole
authors.affiliation: Bioinformatics Center, Savitribai Phule Pune University, Pune, 411007, India.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Sawant
authors.affiliation: Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India.
authors.forename: Rita
authors.initials: R
authors.lastname: Mukhopadhyaya
authors.affiliation: Stress Biology Research Laboratory, Department of Zoology, Savitribai Phule University, Pune, 411007, India. Electronic address: bbnath@gmail.com.
authors.forename: Bimalendu B
authors.initials: BB
authors.lastname: Nath
mesh_terms: D000818:Animals; D001769:Blood / Q000528:radiation effects; D002683:Chironomidae / Q000528:radiation effects*; D002942:Circular Dichroism; D004307:Dose-Response Relationship, Radiation; D000067493:Dynamic Light Scattering; D005720:Gamma Rays; D006418:Heme; D006454:Hemoglobins / Q000737:chemistry* / Q000528:radiation effects*; D006458:Hemolymph / Q000528:radiation effects; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D019476:Insect Proteins / Q000737:chemistry / Q000528:radiation effects; D007814:Larva / Q000528:radiation effects; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D006454:Hemoglobins; D019476:Insect Proteins; D006418:Heme
keywords: Chironomus hemoglobin; Gamma radiation tolerance; Heme-binding pocket analysis; Human hemoglobin