title: Hemoglobin-silver interaction and bioconjugate formation: a spectroscopic study.
abstract: In this article, we report the results of the extent of interaction as well as the formation of a bioconjugate of human hemoglobin (Hb) with silver (Ag). The complexation process and conformational changes are characterized using different spectroscopic and microscopic techniques. The UV-vis study demonstrates the perturbation of the soret/heme band and generates conformational heterogeneity within the heme group in the presence of silver. A fluorescence study suggests that the Tryptophan (Trp) residues of Hb are in a more polar environment after conjugation. Initial fluorescence enhancement with addition of silver is due to metal-enhanced fluorescence. Moreover, the fluorescence quenching after the formation of the Hb-Ag bioconjugate follows the modified Stern-Volmer (S-V) plot. The S-V plot along with the time-resolved fluorescence study indicates the presence of both static and dynamic types of quenching. In addition, the reduction potential values of the entities (Hb-heme, Ag(+), and Trp) indicate the possible electron transfer. The secondary structure calculation from CD and FTIR spectra indicate alpha-helix to beta-sheet conversion, and unfolding of Hb is also responsible for the bioconjugate formation. In addition, FE-SEM, phase contrast inverted microscopy (PCIM) images demonstrate the formation of the silver-protein bioconjugate. The overall data show that there is a change in the secondary as well as the tertiary structure of Hb after conjugation with silver.
authors.affiliation: Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700 032, India.
authors.forename: Mrityunjoy
authors.initials: M
authors.lastname: Mahato
authors.forename: Prabir
authors.initials: P
authors.lastname: Pal
authors.forename: Tapanendu
authors.initials: T
authors.lastname: Kamilya
authors.forename: Ratan
authors.initials: R
authors.lastname: Sarkar
authors.forename: Avinanda
authors.initials: A
authors.lastname: Chaudhuri
authors.forename: G B
authors.initials: GB
authors.lastname: Talapatra
mesh_terms: D002942:Circular Dichroism; D005453:Fluorescence; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012834:Silver / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D014364:Tryptophan / Q000737:chemistry
chemical_list: D006454:Hemoglobins; D012834:Silver; D014364:Tryptophan