Spectroscopic Investigations of Pentobarbital Interaction with Transthyretin

Abstract

Transthyretin (TTR) aggregation has been characterized to be responsible for several amyloid diseases. Fourier transform infrared (FTIR) spectroscopy, �uorescence, and atomic force microscopy (AFM) are used to investigate secondary structure changes in transthyretin, induced upon thermal denaturation and interaction with pentobarbital. Spectral analysis revealed a strong static quenching of the intrinsic �uorescence of TTR by pentobarbital with a binding constant (�) estimated at 2.092 × 10 3 M −1 . Fourier self-deconvolution (FSD) technique is used to evaluates intensity changes in the spectra of the component bands in the amide I and amide II regions due to the changes in pentobarbital concentration in the protein complex. e increases of the relative intensities of the peaks at 1614 cm −1 and 1507 cm −1 are due to the increase of pentobarbital concentrations which is linked to the formation of oligomers in the protein.

Milk oligopeptide inhibition of (α)-tocopherol fortified linoleic acid oxidation

“…[42] Fourier Transform Infrared Spectroscopy (FTIR): FTIR is a common approach to study the conformational changes of secondary structure of proteins and peptides through unveiling the driving forces of inter-and intra-molecular interactions. [43] In the present study, the FTIR spectra of these milk oligopeptides exhibited typical amide I and II at 1600-1700 cm −1 and 1500-1600 cm −1 , respectively. The amide I and amide II were two dominant vibrational bands of peptide backbone.…”

“…A linear curve was generated between the ratio of each milk oligopeptide fluorescent quenching over the concentration of (α)-tocopherol and the Stern-Volmer constant (K sv ) and quenching rate constant (K q ) are listed in Table 1. τ 0 represents the average life span of fluorescent molecule without addition of (α)-tocopherol and is general 10 −8 s. [43] IPIQY interacted with (α)-tocopherol obtained the significant high K sv and K q values compared to other milk oligopeptides (p < .05). Also, K sv and K q values of PYYAK and IAKYI were higher than those of NQFLPYPYYAK and IPIQYV interacted to (α)-tocopherol (p < .05).…”

“…It was reported that the peak at 1646-1664 cm −1 , 1610-1640 cm −1 and 1682-1700 cm −1 , 1664-1681 cm −1 , and 1637-1645 cm −1 represented the structure of α-helix, β-sheet, β-turn and random coil in the amide I, respectively. [30,43,46,47] The FTIR spectra in Figure 7 revealed the spatial conformation alteration of milk oligopeptides before and after the interaction to (α)-tocopherol . The calculated percentages of each secondary structure in the milk oligopeptides with and without the addition of (α)-tocopherol were listed in Table 2 and were attempted to characterize the interaction behavior between milk oligopeptides and (α)-tocopherol.…”

Spectroscopic Investigations of &lt;i&gt;β&lt;/i&gt;-Amyloid Interactions with Propofol and L-Arginine

“…The quenching rate constants for Aβ-propofol and Aβ-arginine were then calculated and found to be 1.1 × 10 12 L•Mol −1 •s −1 and 1.35 × 10 12 L•Mol −1 •s −1 respectively. The obtained values of the quenching rate constants for propofol and L-arginine are larger than the maximum dynamic quenching constants for various quenchers with biopolymers (2 × 10 10 L•Mol −1 •s −1 ) which confirms that static quenching is dominant in these complexes [28] [29]. When the static quenching equation is used [30].…”

“…The analysis of the secondary structure of Aβ in the amide I which occurs between 1600 cm −1 and 1700 cm −1 yields several bands. The peaks of these bands correspond to the C=O stretching vibrations of the amide group, coupled to the C-N stretching and C-C-N deformation mode [28]. The peaks in the amide II (1600 -1480) cm −1 region are due to the coupling of the N-H in-plane bending and C-N stretching modes [33].…”