title: Bioconjugation of 32-macrocyclic polyammonium cations-functionalized gold nanoparticles with BSA.
abstract: Water-dispersed, spherical, underivatized Au-NPs with particle size less than 5 nm were synthesized from an aqueous solution of 32-macrocyclic polyammonium chloride, [32]ane-(NH(2)(+))(8).8Cl(-) (32-MCPAC) using sodium borohydride (NaBH(4)) as the reducing agent. The bioconjugation of the synthesized Au-NPs at different pHs (3.6-5.6) with bovine serum albumin (BSA) protein was studied using UV-Vis, fluorescence, and Raman spectroscopy. These studies support that the Au-NPs were incorporated into the protein moiety and bound to it chemically. The binding constants (K(b)) and stoichiometries (n) (i.e., the number of Au-NPs bound by the proteins) of BSA protein to the Au-NPs at different pHs were determined by measuring the quenching of the fluorescence intensity of the tryptophan residues of the protein molecules after conjugation. The values for K(b) (n) were found to be 1.05 x 10(10) M(-1) (1.66), 2.09 x 10(10) M(-1) (2.30), and 1.86 x 10(10) M(-1) (1.75) at pH 3.60, 4.60, and 5.60 for BSA-Au-NPs conjugations, respectively. The results show that BSA binds to the Au-NPs strongly at pH 4.60, which is equivalent to its isoelectric point (pI 4.6).
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Tarun Kumar
authors.initials: TK
authors.lastname: Misra
authors.forename: Kuan-Pin
authors.initials: KP
authors.lastname: Huang
authors.forename: Chuen-Ying
authors.initials: CY
authors.lastname: Liu
mesh_terms: D000818:Animals; D002412:Cations; D002417:Cattle; D006046:Gold / Q000737:chemistry*; D047028:Macrocyclic Compounds / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D013059:Spectrum Analysis, Raman
chemical_list: D002412:Cations; D047028:Macrocyclic Compounds; D000644:Quaternary Ammonium Compounds; D012710:Serum Albumin, Bovine; D006046:Gold