Applications of ultrasound in analysis, processing and quality control of food: A review

Even an ordinary globular protein can assume a rogue guise if conditions are right.

Amyloid fibrils from muscle myoglobin

Publisher Summary Generalized two-dimensional (2D) correlation spectroscopy is described to show how this technique can be applied to a very broad range of spectral analysis problems. In this spectroscopy, the underlying similarity or dissimilarity among systematic variations in spectroscopic signal intensities is examined. It develops parallel to multiple pulse-based 2D spectroscopy techniques and employs a somewhat different approach to constructing 2D spectra. The signal variations are induced by an external perturbation or physical stimulus applied to the sample, and the pattern of the intensity variation is systematically analyzed by a simple cross-correlation technique. The correlation intensities thus obtained are displayed in the form of a 2D map defined by two independent spectral axes for further analysis. Such a 2D map is referred to as a 2D correlation spectrum, even though many of today's 2D correlation studies include applications in the field outside of spectroscopy, such as chromatography and microscopy. An illustrative example is given for the analysis of attenuated total reflection (ATR) IR spectra collected during the crystallization of biodegradable polymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) to demonstrate the merits of this technique, such as the enhancement of spectral resolution, detection of coordinated changes among spectral signals, and determination of relative directions and sequential order of intensity variations.

https://journals.sagepub.com/doi/pdf/10.1366/0003702001950454

Generalized Two-Dimensional Correlation Spectroscopy

Many biochemists would regard pressure as a physical parameter mainly of theoretical interest and of rather limited value in experimental biochemistry. The goal of this overview is to show that pressure is a powerful tool for the study of proteins and modulation of enzymatic activity.

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High Pressure Effects on Protein Structure and Function

A variety of techniques, including high-pressure unfolding monitored by Fourier transform infrared spectroscopy, fluorescence, circular dichroism, and surface plasmon resonance spectroscopy, have been used to investigate the equilibrium folding properties of six single-domain antigen binders derived from camelid heavy-chain antibodies with specificities for lysozymes, β-lactamases, and a dye (RR6). Various denaturing conditions (guanidinium chloride, urea, temperature, and pressure) provided complementary and independent methods for characterizing the stability and unfolding properties of the antibody fragments. With all binders, complete recovery of the biological activity after renaturation demonstrates that chemical-induced unfolding is fully reversible. Furthermore, denaturation experiments followed by optical spectroscopic methods and affinity measurements indicate that the antibody fragments are unfolded cooperatively in a single transition. Thus, unfolding/refolding equilibrium proceeds via a simple two-state mechanism (N⇋U), where only the native and the denatured states are significantly populated. Thermally-induced denaturation, however, is not completely reversible, and the partial loss of binding capacity might be due, at least in part, to incorrect refolding of the long loops (CDRs), which are responsible for antigen recognition. Most interestingly, all the fragments are rather resistant to heat-induced denaturation (apparent Tm = 60–80°C), and display high conformational stabilities (ΔG(H2O) = 30–60 kJ mole−1). Such high thermodynamic stability has never been reported for any functional conventional antibody fragment, even when engineered antigen binders are considered. Hence, the reduced size, improved solubility, and higher stability of the camelid heavy-chain antibody fragments are of special interest for biotechnological and medical applications.

/pdf/single-domain-antibody-fragments-with-high-conformational-4vwshglh6f.pdf

Single-domain antibody fragments with high conformational stability

https://ucanr.edu/datastoreFiles/608-487.pdf

Protein structure and dynamics at high pressure.

Pressure-temperature phase diagrams of biomolecules.

https://www.cell.com/biophysj/pdf/S0006-3495(02)75605-1.pdf

Comparative Fourier Transform Infrared Spectroscopy Study of Cold-, Pressure-, and Heat-Induced Unfolding and Aggregation of Myoglobin

This work demonstrates that pressure-induced partially unfolded states play a very important role in the aggregation of proteins. The high-pressure unfolding of horse heart metmyoglobin results in an intermediate form that shows a strong tendency to aggregate after pressure release. These aggregates are similar to those that are usually observed upon temperature denaturation. Infrared spectra in the amide I region indicate the formation of an intermolecular antiparallel beta-sheet stabilized by hydrogen bonding. The formation of the aggregates is temperature-dependent. Below 30 degrees C, no aggregation is taking place as seen from the infrared spectra. At 45 and 60 degrees C, two types of aggregates are formed: one that can be dissociated by moderate pressures and one that is pressure-insensitive. When precompressed at 5 degrees C, temperature-induced aggregation takes place at lower temperature (38 degrees C) than without pressure pretreatment (74 degrees C).

László Smeller

Papers

Protein structure and dynamics at high pressure.

Pressure-temperature phase diagrams of biomolecules.

Comparative Fourier Transform Infrared Spectroscopy Study of Cold-, Pressure-, and Heat-Induced Unfolding and Aggregation of Myoglobin

Pressure effect on the temperature-induced unfolding and tendency to aggregate of myoglobin.

Protein stability and dynamics in the pressure–temperature plane