Determination of the secondary structure of proteins in different environments by FTIR‐ATR spectroscopy and PLS regression

Abstract

The secondary structures of proteins (alpha-helical, beta-sheet, beta-turn, and random coil) in the solid state and when bound to polymer beads, containing immobilized phenyl and butyl ligands such as those as commonly employed in hydrophobic interaction chromatography, have been investigated using FTIR-ATR spectroscopy and partial least squares (PLS) methods. Proteins with known structural features were used as models, including 12 proteins in the solid state and 7 proteins adsorbed onto the hydrophobic surfaces. A strong PLS correlation was achieved between predictions derived from the experimental data for 4 proteins adsorbed onto the phenyl-modified beads and reference data obtained from the X-ray crystallographic structures with r(2) values of 0.9974, 0.9864, 0.9924, and 0.9743 for alpha-helical, beta-sheet, beta-turn, and random coiled structures, respectively. On the other hand, proteins adsorbed onto the butyl sorbent underwent greater secondary structural changes compared to the phenyl sorbent as evidenced from the poorer PLS r(2) values (r(2) are 0.9658, 0.9106, 0.9571, and 0.9340). The results thus indicate that the secondary structures for these proteins were more affected by the butyl sorbent, whereas the secondary structure remains relatively unchanged for the proteins adsorbed onto the phenyl sorbent. This study has important ramifications for understanding the nature of protein secondary structural changes following adsorption onto hydrophobic sorbent surfaces. This knowledge could also enable the development of useful protocols for enhancing the chromatographic purification of proteins in their native bioactive states.

High‐strength functionalized pectin/fibroin hydrogel with tunable properties: A structure–property relationship study

“…In neat fibroin and blended hydrogels, amide I band can be deconvoluted to render α helix, β sheet, β turn, and random coil contributions . Herein, amide I related band was deconvoluted using Origin Pro 2016 software.…”

Heteropoly acids triggered self-assembly of cationic peptides into photo- and electro-chromic gels

“…71,72 Generally, the absorption bands located at 1645-1660 cm À1 are attributed to random coil and helical conformation, and the bands at 1620-1630 cm À1 are characteristic of b-sheets. The amide-I frequencies are sensitive indicators of secondary structures of peptides and proteins.…”

Synchrotron Radiation Spectroscopic Techniques as Tools for the Medicinal Chemist: Microprobe X-Ray Fluorescence Imaging, X-Ray Absorption Spectroscopy, and Infrared Microspectroscopy

“…For instance, specific secondary structural assignments include: -helices (1645-1662 cm 1 ), -sheets (1613-1637 cm 1 ), turns (1662-1682 cm 1 ) and random coils (1637-1645 cm 1 ). [99,113,[115][116][117] A recently emerging medicinal chemistry application of SR-FTIR microspectroscopy is the analysis of fixed and live cancer cells to detect biomolecular changes that occur following drug treatment. The interest in the use of this technique stems from an urgent demand for the development of accurate and cost-saving analytical techniques that can be applied to the screening of new drug candidates.…”