title: Soft magnetic memory of silk cocoon membrane.
abstract: Silk cocoon membrane (SCM), a solid matrix of protein fiber, responds to light, heat and moisture and converts these energies to electrical signals. Essentially it exhibits photo-electric and thermo-electric properties; making it a natural electro-magnetic sensor, which may influence the pupal development. This raises the question: 'is it only electricity?', or 'it also posses some kind of magnetic memory?' This work attempted to explore the magnetic memory of SCM and confirm its soft magnetism. Fe, Co, Ni, Mn, Gd were found in SCM, in traces, through energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometry (ICP-MS). Presence of iron was ascertained by electron paramagnetic resonance (EPR). In addition, EPR-spectra showed the presence of a stable pool of carbon-centric free radical in the cocoon structure. Carbon-centric free radicals behaves as a soft magnet inherently. Magnetic-Hysteresis (M-H) of SCM confirmed its soft magnetism. It can be concluded that the soft bio-magnetic feature of SCM is due to the entrapment of ferromagnetic elements in a stable pool of carbon centric radicals occurring on the super-coiled protein structure. Natural soft magnets like SCM provide us with models for developing eco-friendly, protein-based biological soft magnets.
authors.affiliation: Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, 208016, India.
authors.forename: Manas
authors.initials: M
authors.lastname: Roy
authors.affiliation: Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, 208016, India.
authors.forename: Amarish
authors.initials: A
authors.lastname: Dubey
authors.affiliation: Defense Research Development Organization, Delhi, 110054, India.
authors.forename: Sushil Kumar
authors.initials: SK
authors.lastname: Singh
authors.affiliation: Defense Research Development Organization, Delhi, 110054, India.
authors.forename: Kalpana
authors.initials: K
authors.lastname: Bhargava
authors.affiliation: Defense Research Development Organization, Delhi, 110054, India.
authors.forename: Niroj Kumar
authors.initials: NK
authors.lastname: Sethy
authors.affiliation: Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, 208016, India.
authors.forename: Deepu
authors.initials: D
authors.lastname: Philip
authors.affiliation: Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, 208016, India.
authors.forename: Sabyasachi
authors.initials: S
authors.lastname: Sarkar
authors.affiliation: Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, 208016, India.
authors.forename: Alok
authors.initials: A
authors.lastname: Bajpai
authors.affiliation: Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, 208016, India.
authors.forename: Mainak
authors.initials: M
authors.lastname: Das
mesh_terms: D000818:Animals; D012831:Bombyx / Q000502:physiology*; D060733:Electromagnetic Radiation; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry*; D008018:Life Cycle Stages; D059346:Magnets; D008566:Membranes / Q000737:chemistry*; D008670:Metals / Q000737:chemistry*; D009036:Moths / Q000502:physiology*; D047011:Silk / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D005609:Free Radicals; D008670:Metals; D047011:Silk