1 SCIENTIFIC REPORTS | 7: 2726 | DOI:10.1038/s41598-017-02609-z www.nature.com/scientificreports Modulation of Peptide Based Nano-Assemblies with Electric and Magnetic Fields Gaurav Pandey 1 , Jahnu Saikia 1 , Sajitha Sasidharan 1 , Deep C. Joshi 2 , Subhash Thota 2 , Harshal B. Nemade 3 , Nitin Chaudhary 1 & Vibin Ramakrishnan 1 Peptide based nano-assemblies with their self-organizing ability has shown lot of promise due to their high degree of thermal and chemical stability, for biomaterial fabrication. Developing an effective way to control the organization of these structures is important for fabricating application-oriented materials at the molecular level. The present study reports the impact of electric and magnetic field- mediated perturbation of the self-assembly phenomenon, upon the chemical and structural properties of diphenylalanine assembly. Our studies show that, electric field effectively arrests aggregation and self-assembly formation, while the molecule is allowed to anneal in the presence of applied electric fields of varying magnitudes, both AC and DC. The electric field exposure also modulated the morphology of the self-assembled structures without affecting the overall chemical constitution of the material. Our results on the modulatory effect of the electric field are in good agreement with theoretical studies based on molecular dynamics reported earlier on amyloid forming molecular systems. Furthermore, we demonstrate that the self-assemblies formed post electric-field exposure, showed difference in their crystal habit. Modulation of nano-level architecture of peptide based model systems with external stimulus, points to a potentially rewarding strategy to re-work proven nano- materials to expand their application spectrum. Ability to design, control morphology, and tune up physical and chemical properties at nanoscale characterize the heart of nanotechnology. Generation of nano-level architecture should ideally have a design phase at molecular scale. Morphology of such systems can be better controlled, if they assemble further-on to micro dimensions. Nanotechnology research mostly focuses on the latter half by way of their imminent utility while fabricating materials at larger dimensions. Application of physical agents for tailoring the nanostructure morphology can be very useful for nanostructure fabrication. In last decade, there has been an increased focus on organic and bio-organic nano-assemblies. Peptide nano- tubes, their physical properties, and assembly morphologies are extensively studied due to their excellent bio- compatibility as well as functional and structural diversity. Many ordered supramolecular structures have been constructed using peptides as the building blocks. e most extensively utilized peptide-based building block is diphenylalanine (Phe-Phe or FF), which is the shortest bio-molecule known to self-assemble into ordered nano- structures. FF incidentally is also the core recognition motif of the β-amyloid polypeptide, a peptide associated with Alzheimer’s disease 1 . It can self-assemble into a variety of structures like microtubes, nanotubes 2 , microcrys- tals, nanofibers 3 , nanorods 4, 5 and nanowires 6 . e potential of these supramolecular structures have been utilized in diverse fields including nanofabrication, drug delivery vehicles 7 , bio-sensing 8 , energy storage devices, and hydrogels for tissue engineering 9, 10 . e crystal structure of FF exhibits a non-centrosymmetric hexagonal space group (P6 1 ) 1, 11 , which allows it to possess prop- erties like piezoelectricity 12, 13 , optical activity 14, 15 and ferroelectricity 16 . Due to its low dimensional highly ordered structure it also exhibits quantum confinement 17 , forming quantum dots 18 . Self-assembled structures formed by analogues of FF such as Ac-Phe-Phe-NH 2 , NH 2- Phe-Phe- NH 2 , NH 2 -(p-nitro-Phe)-(p-nitro-Phe)-COOH, NH 2 (4-phenyl-Phe)-(4-phenyl-Phe)-COOH, PEGylated tetra-phenylalanine (L6-F4), β-AspFF etc. have also resulted in tubular, fibrillar and squared plate structures respectively 10, 19, 20 . 1 Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, India. 2 Department of Physics, Indian Institute of Technology Guwahati, Guwahati, 781039, India. 3 Department of Electronics and Electrical Engineering, Indian Institute of Technology Guwahati, Guwahati, 781039, India. Correspondence and requests for materials should be addressed to V.R. (email: vibin@iitg.ernet.in) Received: 23 January 2017 Accepted: 12 April 2017 Published: xx xx xxxx OPEN