ATR FTIR Study of the Interaction of TiO₂ Nanoparticle Films with β-Lactoglobulin and Bile Salts

Abstract

The technique of in situ particle film attenuated total reflection Fourier transform infrared spectroscopy (ATR FTIR) has been used to probe the adsorption and coadsorption (sequential) of a common food protein (β-lactoglobulin, BLG) and two representative bile salts (taurocholic acid and glycocholic acid, abbreviated as TCA and GCA) onto the surface of titanium dioxide (TiO2) nanoparticles. Evaluating of binding interactions between commonly used (historically now, in some countries) food additives and food components, as well as the body’s own digestion chemicals, is a critical step in understanding the role of colloidal phenomena in digestion and bioavailability. TCA is found to adsorb onto TiO2 but without any significant ability to be retained when it is not present in the aqueous phase. GCA is also found to adsorb via two distinct binding mechanisms, with one type of adsorbed species being resistant to removal. BLG adsorbs, is irreversibly bound, and has altered conformation when adsorbed at pH 2 (stomach conditions) to the conformation when adsorbed at pH 6.5 (small intestine conditions). This altered conformation is not interface-dependent and is mirrored in the solution spectra of BLG. Sequential coadsorption studies indicate that TCA and GCA adsorb onto TiO2 nanoparticle surfaces and display similar degrees of reversibility and binding in the presence or absence of preadsorbed BLG.

Interfacial Electrostatic Self‐Assembly of Amyloid Fibrils into Multifunctional Protein Films

“…The peak of BLG fibrils at 1700–1600 cm −1 , reflects the stretching vibration of the moieties CO in the amide I band, and can provide the information of protein secondary structure. [ 33 ] After compounding with phytic acid, the characteristic peak in the amide I band does not change significantly (Figures S6 and S7, Supporting Information), indicating that phytic acid has negligible on the conformation of BLG fibrils. The characteristic peak of BLG fibrils in the amide II band region (1500–1600 cm −1 ) attributed to the bending vibration of the NH bond and the stretching vibration of the CN bond shifts to a high wavenumber (Figure S6, Supporting Information).…”

In Situ ATR Spectroscopy Study of the Interaction of Acacia senegal Gum with Gold Nanoparticles Films at the Solid–Liquid Interface

“…Nevertheless, the separation difference (Δν) between the asymmetric carboxylate and symmetric carboxylate stretching vibration can still be estimated (Δν ads = ν as – ν s = 210 or 195 cm –1 ) and compare to the separation difference in solution (Δν sol = 179 cm –1 ). It would correspond to a monodentate binding in both situations (i.e., Δν ads > Δν sol ). , Although Δν was previously used to evaluate bacteria ,, or protein binding onto metal substrate, this approach was developed for simple organic acids, and therefore, must be used only to suggest potential binding mechanisms. The amide II band presents a maximum around 1534 cm –1 with a shoulder at 1518 cm –1 corresponding to the C–C ring vibration of the tyrosine .…”

“…It would correspond to a monodentate binding in both situations (i.e., Δν ads > Δν sol ). 67,71 Although Δν was previously used to evaluate bacteria 67,72,73 or protein 28 binding onto metal substrate, this approach was developed for simple organic acids, and therefore, must be used only to suggest potential binding mechanisms. The amide II band presents a maximum around 1534 cm −1 with a shoulder at 1518 cm −1 corresponding to the C−C ring vibration of the tyrosine.…”

“…This technique probes chemical and structural changes in molecules due to adsorption or environmental changes, such as pH, ionic strength, concentration, and temperature. Numerous studies have focused on the adsorption of proteins and the study of their secondary structure, − while others dealt with polysaccharide or polyelectrolyte adsorption − on various solid substrates, including gold nanoparticles, with the aim of ATR–FTIR. To the best of our knowledge, no study focused on the adsorption of such highly complex AGP macromolecules on solid surfaces by in situ ATR–FTIR.…”

Formation of a Stable Co-Amorphous System for a Brick Dust Molecule by Utilizing Sodium Taurocholate with High Glass Transition Temperature

“…Since the intermolecular interaction between AntiY 5 R and NaTC was suggested even in the amorphous state ( Figure 5 ), possible interactions were investigated in detail using FT-IR analysis ( Figure 7 ). The FT-IR spectra of NaTC showed broad peaks that were assigned to the C=O of the amide I band at 1653 cm −1 and the S=O of sulfonate stretching at 1194–1169 cm −1 [ 53 ]. AntiY 5 R showed the peaks of the C=N of oxazolopyridine symmetric stretching at 1651 cm −1 , N-H 2 in the plane band at 1580 cm −1 , CH 3 of tertiary butyl group symmetric deformations at 1396 cm −1 , S=O of sulfonamide asymmetric stretching at 1358 cm −1 , C-O-C of oxazolopyridine stretching at 1298 cm −1 , C-F stretching at 1205 cm −1 , and C-H of oxazolopyridine bending at 1146 and 1121 cm −1 .…”