Abstract
BackgroundElucidation of molecular mechanism of silver nanoparticles (SNPs) biosynthesis is important to control its size, shape and monodispersity. The evaluation of molecular mechanism of biosynthesis of SNPs is of prime importance for the commercialization and methodology development for controlling the shape and size (uniform distribution) of SNPs. The unicellular algae Chlamydomonas reinhardtii was exploited as a model system to elucidate the role of cellular proteins in SNPs biosynthesis.ResultsThe C. reinhardtii cell free extract (in vitro) and in vivo cells mediated synthesis of silver nanoparticles reveals SNPs of size range 5 ± 1 to 15 ± 2 nm and 5 ± 1 to 35 ± 5 nm respectively. In vivo biosynthesized SNPs were localized in the peripheral cytoplasm and at one side of flagella root, the site of pathway of ATP transport and its synthesis related enzymes. This provides an evidence for the involvement of oxidoreductive proteins in biosynthesis and stabilization of SNPs. Alteration in size distribution and decrease of synthesis rate of SNPs in protein-depleted fractions confirmed the involvement of cellular proteins in SNPs biosynthesis. Spectroscopic and SDS-PAGE analysis indicate the association of various proteins on C. reinhardtii mediated in vivo and in vitro biosynthesized SNPs. We have identified various cellular proteins associated with biosynthesized (in vivo and in vitro) SNPs by using MALDI-MS-MS, like ATP synthase, superoxide dismutase, carbonic anhydrase, ferredoxin-NADP+ reductase, histone etc. However, these proteins were not associated on the incubation of pre-synthesized silver nanoparticles in vitro.ConclusionPresent study provides the indication of involvement of molecular machinery and various cellular proteins in the biosynthesis of silver nanoparticles. In this report, the study is mainly focused towards understanding the role of diverse cellular protein in the synthesis and capping of silver nanoparticles using C. reinhardtii as a model system.
Highlights
Elucidation of molecular mechanism of silver nanoparticles (SNPs) biosynthesis is important to control its size, shape and monodispersity
It was found that the amount of SNPs has an upper limit, which depends on the reducing capacity of the biological extracts, AgNO3 concentration and incubation time for the ease of reduction of the metal (Figure 1)
Identification of SNPs bound proteins Proteins associated on the in vitro and in vivo synthesized SNPs were resolved on SDS-PAGE and the protein bands were processed for MALDI-MS and MALDI-MSMS analysis (Figure 6a and 6b)
Summary
Elucidation of molecular mechanism of silver nanoparticles (SNPs) biosynthesis is important to control its size, shape and monodispersity. Silver nanoparticles (SNPs) have extensive applications in civil, therapeutic and industrial areas as catalyst, cryogenic superconductor, biosensor, microelectronic and bacteriostatic materials [1,2,3], etc These SNPs have been synthesized by various physical, chemical and biological methods. Enzymes present in the cells are responsible for the reduction of silver ions. These investigators had not delineated the molecular machinery and involvement of biomolecules for SNPs biosynthesis. The presence of hydrogenase in the F. oxysporum broth was assumed to be responsible for the biosynthesis of SNPs [15,16,17] This extra cellular enzyme shows excellent redox properties and it can act as an electron shuttle in metal reduction [15,18]. The identification of macromolecules responsible for the SNPs biosynthesis would delineate the possible mechanism of SNPs production in biological model systems
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