International Journal of Basic and Applied Biology p-ISSN: 2394-5820, e-ISSN: 2349-2539, Volume 3, Issue 4; October-December, 2016, pp. 242-246 © Krishi Sanskriti Publications http://www.krishisanskriti.org/Publication.html Computational Study and Characterization of Green Synthesis of Silver Nanoparticles Shreya Anand 1 , Priyam Raut 2 , Rashmi Gupta 3 , Raghu Raja Pandiyan K 4 and Padmini Padmanabhan 5 1,2,3,5 Department of Bio- Engineering BIT Mesra, Ranchi, INDIA 4 Department of Chemical Engineering BIT Mesra, Ranchi, INDIA E-mail: 1 shreyaanand.30@gmail.com, 2 priyam.raut@gmail.com, 3 rashmi171990@gmail.com, 4 raghuchemraj@gmail.com, 5 padmini@bitmesra.ac.in Abstract—Nanotechnology has been heralded as a revolutionary field of research which leads to an alternative pathway for exploration and evolution of biological entities. Plants are the natural chemical factories which are economical and require minimal maintenance. They are non-toxic, environment friendly and compatible for pharmaceutical as well as biomedical application. The major mechanism of synthesis is plant-assisted reduction due to the presence of phytochemicals (phenols, alkaloids, flavonoids, steroids) which are directly involved in the reduction of the silver ions and the formation of silver nanoparticles. The objective of this research is to biosynthesize silver nanoparticles using leaf extract of Alternanthera sp. and the synthesized nanoparticles were characterized by UV-VIS spectroscopy, DLS, SEM. Using a host of computational biology tools such as ScanProsite, ASA view, CONSURF etc. we study the interaction of 4,5-dioxygenase like protein (betacyanin) with silver nitrate, analyze the structure, exposed amino acid residue and their solvent accessibility. 1. INTRODUCTION The biological approach of metal nanoparticles synthesis is a focus of interest because of its enormous potential in the field of Nanotechnology. Biosynthetic process involves the use of plant extract for the synthesis of silver nanoparticles [1]. The advancement of Green synthesis over other method provides easy scale up for large scale production of nanoparticles. The plant Alternanthera ficoidea is a species of Amaranthaceae family and is commonly used as ornamental edging plant. It is considered as environmental weed and shows anti-microbial activity. It has been suggested that the biomolecules present in the plants play important role in catalysing the synthesis [2]. The combination of phytochemicals – phenols, alkaloids, steroids in this plant helps in reduction of Ag (I) to Ag (0) ions. Proteins contain various amino acids that act as a reducing agent. The protein-nanoparticle interaction either occurs through free amine group or cysteine residues in proteins and via the electrostatic attraction of negatively charged carboxylate groups [3]. The present study promoted us to investigate enzymes present in the Alternanthera sp. for the synthesis of metal-biomolecules hybrid. The protein, 4,5- dioxygenase like protein (betacyanin) is the protein which includes betalain pigment, a class of red and yellow indole- derived pigments found in plants of the Caryophyllales order [4]. Computational studies are used to understand the possible amino acid involved in the biosynthetic process [5]. This Green synthetic approach to silver nanoparticles will give insight to understand the chemistry of amino acids of the enzyme and its interaction with the metal ion. 2. EXPERIMENTAL 2.1 Materials and Methods Alternanthera ficoidea leaves were collected from BIT, Mesra campus. Silver nitrate was procured from Merck, India. Phosphate buffer was prepared in laboratory at pH 8.5. All other chemicals and solvents used were of analytical grade. 2.2 Preparation of Extract Extract was prepared by weighing 10gm of leaves and were thoroughly washed thrice in distilled water, surface sterilized using methanol, cut into fine pieces. Crushed using mortar pestle in phosphate buffer, centrifuged thrice and were properly filtered. 2.3 Synthesis of Silver nanoparticles The biosynthesis of silver nanoparticles were carried out by incubating 50ml of leaf extract in 500µl (1M) silver nitrate. Solution was kept at 37 ◦ C and was monitored using UV- visible spectroscopy as well as Dynamic light scattering. 2.3 Characterization of silver nanoparticles Dynamic light scattering (DLS) measurement was carried out by using Malvern instruments, UK, Nano ZS at 25 ◦ C for 12 cycles. Sample for Scanning electron microscopy were prepared by drop coating purified silver nanoparticle on