Differential sensitivity of Chironomus and human hemoglobin to gamma radiation.

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.

Vibrational spectroscopic detection of radiation-induced structural changes in Chironomus hemoglobin.

Purpose: Chironomus hemoglobin is known to exhibit higher gamma radiation resistance compared to human hemoglobin. In the present study, we have introduced a sensitive method to analyze radiation-induced alterations in Chironomus hemoglobin using Vibrational spectroscopy and further highlighting its potential for monitoring radiotoxicity in aquatic environments. Materials and methods: Vibrational spectroscopic methods such as Raman and FT-IR spectroscopy were used to capture the distinctive chemical signature of Chironomus hemoglobin (ChHb) under both in vitro and in vivo conditions. Any radiation dose-dependent shifts could be analyzed Human hemoglobin (HuHb) as standard reference. Results: Distinctive Raman peak detected at 930 cm-1 in (ChHb) was attributed to C-N stretching in the heterocyclic ring surrounding the iron atom, preventing heme degradation even after exposure to 2400 Gy dose. In contrast, for (HuHb), the transition from deoxy-hemoglobin to met-hemoglobin at 1210 cm-1 indicated a disruption in oxygen binding after exposure to 1200 Gy dose. Furthermore, while ChHb exhibited a consistent peak at 1652 cm-1 in FT-IR analysis, HuHb on the other hand, suffered damage after gamma irradiation. Conclusion: The findings suggest that vibrational spectroscopic methods hold significant potential as a sensitive tool for detecting radiation-induced molecular alterations and damages. Chironomus hemoglobin, with its robust interaction of the pyrrole ring with Fe, serves as a reliable bioindicator molecule to detect radiation damage using vibrational spectroscopic method.

Unfolding and inactivation of proteins by counterions in protein-nanoparticles interaction.

In this work, the structure and activity of proteins; such as, hen egg lysozyme (HEWL) and calf intestine alkaline phosphatase (CIAP); have been investigated after incubation with surface coated iron oxide nanoparticles (IONPs) in water. IONPs were coated with counterions bound charge-ligands and were named as the charge-ligand counterions iron oxide nanoparticles (CLC-IONPs). The coating was done with tri-lithium citrate (TLC) and tri-potassium citrate (TKC) to have negative surface charge of CLC-IONPs and Li(+) and K(+), respectively, as counterions. To have positive surface charge, IONPs were coated with cetylpyridinium chloride (CPC) and cetylpyridinium iodide (CPI) having Cl(-) and I(-), respectively, as counterions. The secondary structure of proteins was measured using far ultraviolet circular dichroism (CD) spectroscopy which showed that both proteins were irreversibly unfolded after incubation with CLC-IONPs. The unfolded proteins were seen to be functionally inactive, as confirmed through their activity assays, i.e., HEWL with Escherichia coli (E. coli) and CIAP with para-nitrophenyl phosphate (pNPP). Additionally, we have observed that monomeric hemoglobin (Hb) from radio-resistant insect Chironomus ramosus (ChHb) was also partially unfolded upon interaction with CLC-IONPs. This work clearly shows the role of counterions in protein inactivation via protein-nanoparticles interaction and, therefore, CLC-IONPs could be used for therapeutic purpose.

Chironomus ramosus larvae exhibit DNA damage control in response to gamma radiation.

PURPOSE: Chironomus ramosus is one of the recently reported radiotolerant insects. Salivary gland cells of fourth instar larvae respond to ionizing radiations with increases in the levels of antioxidant enzymes and chaperone proteins. Here we made an attempt to study the state of nuclear DNA after exposure of larvae to a lethal dose for 20% of the population (LD(20)) of gamma radiation (2200 Gy, at a dose rate 5.5 Gy/min). MATERIALS AND METHODS: Genomic DNA preparations were subjected to competitive ELISA (Enzyme linked immunosorbent assay) for detection of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and dynamic light scattering (DLS) to monitor any radiation-induced damage. Single salivary gland cells were subjected to alkaline single cell gel electrophoresis (ASCGE), comet assay and pulsed field gel electrophoresis (PFGE) to check for DNA double-strand breaks. RESULTS: Results from all four experimental procedures confirmed damage of nucleobases and fragmentation of nuclear DNA immediately after radiation. Some 48 h after radiation exposure, modified 8-oxodG residues returned to basal level, homodispersity of genomic DNA reappeared, the length of comet tail regressed significantly (ASCGE) and PFGE pattern matched with that of high molecular weight unirradiated DNA. CONCLUSION: Chironomus ramosus larvae showed control of DNA damage as observed over 48 h in post irradiation recovery which could be attributed to their ability to tolerate gamma radiation stress.