FT-IR Spectroscopy for the Identification of Binding Sites and Measurements of the Binding Interactions of Important Metal Ions with Bovine Serum Albumin

Abstract

Proteins play crucial roles in the transportation and distribution of therapeutic substances, including metal ions in living systems. Some metal ions can strongly associate, while others show low affinity towards proteins. Consequently, in the present work, the binding behaviors of Ca2+, Ba2+, Ag+, Ru3+, Cu2+ and Co2+ with bovine serum albumin (BSA) were screened. BSA and the metal ions were allowed to interact at physiological pH and their binding interactions were screened by using FT-IR spectroscopy. Spectra were collected by using hydrated films over a range of 4000–400 cm−1. The interaction was demonstrated by a significant reduction in the spectral intensities of the amide I (C=O stretching) and amide II bands (C–N stretching coupled to NH bending) of the protein after complexation with metal ions. The binding interaction was further revealed by spectral shifting of the amide I band from 1651 cm−1 (free BSA) to 1653, 1654, 1649, 1655, 1655, and 1654 cm−1 for BSA–Ca2+, BSA–Ba2+, BSA–Ag+, BSA–Ru3+, BSA–Cu2+ and BSA–Co2+ complexes, respectively. The shifting of the amide I band was due to the interactions of metal ions with the O and N atoms of the ligand protein. Estimation of the secondary protein structure showed alteration in the protein conformation, characterized by a marked decrease (12.9–40.3%) in the α-helix accompanied by increased β-sheet and β-turn after interaction with the metal ions. The interaction results of this study were comparable with those reported in our previous investigation of metal ion–BSA interactions using affinity capillary electrophoresis (ACE), which has proven the accuracy of the FT-IR technique in the measurement of interactions between proteins and metal ions.

Calcium-Induced Activity and Folding of a Repeat in Toxin Lipase from Antarctic Pseudomonas fluorescens Strain AMS8

“…Interestingly, FTIR spectroscopy can also be used to analyze the calcium binding of protein [27]. Interaction of the protein with metal ions resulted in significant vibration and spectroscopy signals which was detected at wavelengths corresponding to three groups, namely, Amide A at 3500 cm −1 (NH), Amide I at 1700-1600 cm −1 (C=O) and Amide II at 1550 cm −1 (C-N and N-H) [28]. Based on the FTIR analysis, two peaks were detected at the Amide 1 and Amide A wavelength.…”

Flame-Made Calcium Phosphate Nanoparticles with High Drug Loading for Delivery of Biologics

“…Amide III bonds result from CH 2 scissoring motion [44]. Moreover, as shown in Figure 4a, when the spectra of loaded particles (red, blue and green lines) are compared to the spectrum of pure CaP S nanoparticles (black line), there is a decrease of the intensity of the PO 4 peak along with slight shifting of the peaks of pure BSA to higher wavenumbers for the loaded CaP S (green, red and blue lines in comparison to magenta line in Figure 4b) indicate that there is some interaction at these sites between the CaP and the macromolecules [47,48].…”

“…the spectrum of pure CaPS nanoparticles (black line), there is a decrease of the intensity of the PO4 bands and the disappearance of CO3 2− band. Even though the CO3 2− from the amorphous CaPS might dissolve in aqueous solutions resulting in the disappearance of that band, the reduction of the PO4 3− peak along with slight shifting of the peaks of pure BSA to higher wavenumbers for the loaded CaPS (green, red and blue lines in comparison to magenta line in Figure 4b) indicate that there is some interaction at these sites between the CaP and the macromolecules [47,48]. The hydrodynamic size measured by dynamic light scattering (DLS) in PBS (particle concentration 100 μg/mL) before and after macromolecule loading on the CaPS nanoparticles is shown in Figure 5a (number distribution, please see Figure S2 in Supplementary Materials the intensity distribution).…”

Bovine Serum Albumin Protein-Based Liquid Crystal Biosensors for Optical Detection of Toxic Heavy Metals in Water

“…Interaction of BSA with heavy metals strongly affects both selectivity and limit of detection. Some metal ions can strongly associate, while others show low affinity towards BSA [26]. Upon addition of heavy metal ions at high concentration to BSA, bright granular textures are obtained which in turn reveal their significant interaction with BSA, whereas sodium and ammonium ions are unable to give such textures even at very high concentration.…”