title: Fluorescence enhancement of glutaraldehyde functionalized polyaniline nanofibers in the presence of aromatic amino acids.
abstract: Polyaniline nanofibers (PNFs) synthesized by dilute polymerization method have been surface functionalized with glutaraldehyde at their N-terminals in Phosphate Buffered Saline (PBS) at P(H)=7.4 in order to achieve improved interaction of surface functionalized polyaniline nanofibers (SF-PNFs) with aromatic amino acids-Tyrosine, Tryptophan and Phenylalanine through incorporation of aldehyde (-CHO) and hydroxyl (-OH) functionalities. HRTEM reveals nanofibers of average diameter of 35.66 nm. FESEM depicts interconnected networks of nanofibers of polyaniline (PAni). UV-visible absorption and Fluorescence spectroscopy indicate that the PNFs and SF-PNFs are in emeraldine base (EB) form. FT-IR, (1)H NMR spectroscopy suggests covalent interactions of SF-PNFs with aromatic amino acids and possible reaction mechanisms have been proposed based on these results. Remarkable enhancement in fluorescence signals of SF-PNFs in the presence of aromatic amino acids has been observed and the apparent binding constant (KA) and the number of binding sites (n) have been calculated using fluorescence enhancement equation. The KA value is found to be highest for SF-PNFs+Tyrosine and n is two for all the polymer amino acid complexes, which are in agreement with the FT-IR and (1)H NMR results. Fluorescence resonance energy transfer (FRET) efficiency has been found to be highest for SF-PNFs+Tyrosine giving maximum fluorescence enhancement. The study of interaction mechanisms by means of an extremely sensitive technique like fluorescence using SF-PNFs as a substrate may provide a promising analytical tool for detection and monitoring any biochemical reactions involving these three aromatic amino acids.
authors.affiliation: Materials Research Laboratory, Department of Physics, Tezpur University, Tezpur 784028, India.
authors.forename: Rajiv
authors.initials: R
authors.lastname: Borah
authors.affiliation: Materials Research Laboratory, Department of Physics, Tezpur University, Tezpur 784028, India. Electronic address: ask@tezu.ernet.in.
authors.forename: Ashok
authors.initials: A
authors.lastname: Kumar
mesh_terms: D024322:Amino Acids, Aromatic / Q000737:chemistry; D000814:Aniline Compounds / Q000737:chemistry*; D031541:Fluorescence Resonance Energy Transfer; D005976:Glutaral / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D057139:Nanofibers / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D014443:Tyrosine / Q000737:chemistry
chemical_list: D024322:Amino Acids, Aromatic; D000814:Aniline Compounds; C416807:polyaniline; D014443:Tyrosine; D005976:Glutaral
keywords: Enhancement; FRET; Fluorescence; Interaction; SF-PNFs