Metal nanoparticles are being increasingly used in many sectors of the economy, there is growing interest in the biological and environmental safety of their production. The main methods for nanoparticle production are chemical and physical approaches that are often costly and potentially harmful to the environment. Natural plant biomoleculessuch as amino acids are involved in the bioreduction of metal salts during the nanoparticle synthesis. However, when these metal salts were replaced by tetrachloroauric and tetrachloroplatinic acids, nanoparticles were formed in the presence of sucrose, which is likely due to the acidic hydrolysis of sucrose into free glucose and fructose, which have an open chain-form structure. It is currently believed that the sugar aldehyde group is oxidized into a carboxyl group via the nucleophilic addition of OH-, which in turn leads to the reduction of metal ions and to the synthesis of nanoparticles. After amino acids are linked to the peptide chain, their individual ability to bind and reduce metal ions may change. For example, the formation of the peptide backbone changes the functionality of the R-carbon of carboxylic acids and amines of some amino acid residues since they move to a form inaccessible for interaction with metal ions. However, free side chains of amino acids can still participate in the binding and reduction of metal ions. The suitability of side chains for this interaction may change depending on the amino acid sequence, which could affect the accessibility of individual groups. The work by Tan et al. [43] explained in detail how the amino acid sequence may affect the protein’s ability to chelate and/or reduce metal ions. It was found that synthesized peptides, composed of amino acids capable of effective binding of metal ions, and of amino acids possessing high reducing activity, had lower reduction parameters than expected. It was suggested that the strong sequestration of metal ions to the peptide was inhibitory to their subsequent reduction by reducing amino acids. It was also found that peptides containing amino acids that weakly bind metal ions such as leucine, phenylalanine, and proline were ineffective in reducing tetrachloroauric acid anions, probably because of their inability to retain metal ions close to the reduction sites.

 Since proteins are constituted from amino acids, their activity in metal

nanoparticle synthesis must be related to the presence of certain amino acid residues in a peptide sequence.the formation of the peptide backbone changes the functionality of the R-carbon of carboxylic acids and amines of some amino acid residues since they move to a form inaccessible for interaction with metal ions. However, free side chains of amino acids can still participate in the binding and reduction of metal ions. The suitability of side chains for this type of interaction may change depending on the amino acid sequence, which could affect the accessibility of individual groups

The length of the proteins, its molecular weight and its sterochemistry would decide on the type of interaction with the metal and would effect the nano particle synthesis.

Dear Dr.Ravi Kant, Dr.Sridhar and Ms.Sri Vithya,

Thanks for your immediate response for my last question. I still working on the mechanism which is exactly matching with your answers.  Let us meet again with some other topic. regards,

M.Sivakumar.

See the following publications for detail.

H. K. Daima, PR. Selvakannan, A. E. Kandjani, R. Shukla, S. K. Bhargava, V. Bansal. Synergistic influence of polyoxometalate surface corona towards enhancing the antibacterial performance of tyrosine-capped Ag nanoparticles. Nanoscale 6 (2), 2014, pp. 758-765. Publisher: Royal Society of Chemistry,  DOI: 10.1039/C3NR03806H, ISSN: 2040-3372 (Front Inner Cover, IF-7.367).

H. K. Daima, PR. Selvakannan, R. Shukla, S. K. Bhargava, V. Bansal. Fine-tuning the antimicrobial profile of biocompatible gold nanoparticles by sequential surface functionalization using polyoxometalates and lysine. PLoSOne 8 (10), 2013, pp. 1-14. Publisher: Public Library of Science, DOI: 10.1371/journal.pone.0079676, ISSN: 1932-6203 (IF-2.806).

Dear Daima, Thanks for your contribution