Broadened Far-Infrared Absorption Spectra for Hydrated and Dehydrated Myoglobin

Abstract

The far-infrared absorption spectra of myoglobin powder at hydration levels between 3.6 and 42 wt % were measured with terahertz time-domain spectroscopy and Fourier transform infrared spectroscopy. Absorption is dominated by the water content, but even the driest specimens have a nearly continuous spectrum without identifiable sharp features. Inhomogeneous broadening plus the intrinsically high spectral density of vibrational modes in the region below 2.0 THz apparently combine to obscure the lowest frequency vibrational modes expected for protein molecules of this size. A continuous absorption spectrum for hydrated protein powders suggests that the absorption mechanisms are similar to those in liquid water, and hinders the spectroscopic identification of biomolecules in this frequency range.

Current advances in precious metal core–shell catalyst design

“…However, given the expensiveness of Rh, Rh–Pt fails to attract much interest as a research topic. Recent reports suggest the Pd–Pt bimetallic catalyst, especially the Pd–Pt core–shell catalyst, as a promising replacement for the Pt catalyst because of its unique characteristics, which are not merely combined from the properties of the two constituent metals [40–49]. Table 1 shows that the methanol electron – oxidation reaction (MOR) activity on Pd–Pt can be greatly improved.…”

“…This method includes the general electrochemical method [106] and the Galvanic displacement method [23, 49, 107, 108]. Electrochemical synthesis requires conductive substrates and an electrochemical cell, and its process is more complicated than that of the wet chemical method.…”

Analytical Terahertz Spectroscopy

“…23 Since the THz frequency matches the low-frequency vibration and the vibration modes of weak interactions, such as hydrogen bonds, THz-TDS constitutes a unique tool for studying various molecules and materials whose molecular and/or crystal structures are stabilized by these weak interactions. The steric structures of many biological molecules are stabilized by hydrogen bonds, and THz-TDS studies have been undertaken on proteins, 26 polypeptides, 7,27,28 and DNA. 29,30 Figure 3(a) shows the absorption spectra of myoglobin powder obtained with THz (solid line) and Fourier-transform infrared spectroscopy (dotted line).…”

“…Since this means an average of two modes within 15 GHz spectrometer resolution, most modes would not be individually resolvable. 26 Figure 3(b) shows the THz spectra of polypeptide powder of glycine, (Gly)n (n = 1 -4). As the chain length increases, distinct and new absorption features were produced.…”

Terahertz Dielectric Response Sensitivity to Protein Oxidation State

“…Previously we and others have used terahertz dielectric response to determine the sensitivity to protein dynamics. [1][2][3][4][5][6][7][8][9] An important characterization of protein dynamics is the protein flexibility, often defined through the B factor from X-ray crystallography measurements. This flexibility has also been characterized by average atomic mean squared displacement measurements, <x 2 >, using neutron scattering or Mossbauer measurements for Fe containing proteins.…”