Protein Thermal Stability Research Articles

Investigation of Cellular Response to the HSP90 Inhibition in Human Cells Through Thermal Proteome Profiling

Heat shock proteins are chaperones, and they are responsible for protein folding in cells. Heat shock protein 90 (HSP90) is one of the most important chaperones in human cells, and its inhibition is promising for cancer therapy. However, despite the development of multiple HSP90 inhibitors, none of them has been approved for disease treatment due to unexpected cellular toxicity and side effects. Hence, a more comprehensive investigation of cellular response to HSP90 inhibitors can aid in a better understanding of the molecular mechanisms of the cytotoxicity and side effects of these inhibitors. The thermal stability shifts of proteins, which represent protein structure and interaction alterations, can provide valuable information complementary to the results obtained from commonly used abundance-based proteomics analysis. Here, we systematically investigated cell response to different HSP90 inhibitors through global quantification of protein thermal stability changes using thermal proteome profiling, together with the measurement of protein abundance changes. Besides the targets and potential off-targets of the drugs, proteins with significant thermal stability changes under the HSP90 inhibition are found to be involved in cell stress responses and the translation process. Moreover, proteins with thermal stability shifts under the inhibition are upstream of those with altered expression. These findings indicate that the HSP90 inhibition perturbs cell transcription and translation processes. The current study provides a different perspective for achieving a better understanding of cellular response to chaperone inhibition.

DeepSTABp: A Deep Learning Approach for the Prediction of Thermal Protein Stability.

Proteins are essential macromolecules that carry out a plethora of biological functions. The thermal stability of proteins is an important property that affects their function and determines their suitability for various applications. However, current experimental approaches, primarily thermal proteome profiling, are expensive, labor-intensive, and have limited proteome and species coverage. To close the gap between available experimental data and sequence information, a novel protein thermal stability predictor called DeepSTABp has been developed. DeepSTABp uses a transformer-based protein language model for sequence embedding and state-of-the-art feature extraction in combination with other deep learning techniques for end-to-end protein melting temperature prediction. DeepSTABp can predict the thermal stability of a wide range of proteins, making it a powerful and efficient tool for large-scale prediction. The model captures the structural and biological properties that impact protein stability, and it allows for the identification of the structural features that contribute to protein stability. DeepSTABp is available to the public via a user-friendly web interface, making it accessible to researchers in various fields.

Potential of dissimilarity measure-based computation of protein thermal stability data for determining protein interactions

Determining the interacting proteins in multiprotein complexes can be technically challenging. An emerging biochemical approach to this end is based on the 'thermal proximity co-aggregation' (TPCA) phenomenon. Accordingly, when two or more proteins interact to form a complex, they tend to co-aggregate when subjected to heat-induced denaturation and thus exhibit similar melting curves. Here, we explore the potential of leveraging TPCA for determining protein interactions. We demonstrate that dissimilarity measure-based information retrieval applied to melting curves tends to rank a protein-of-interest's interactors higher than its non-interactors, as shown in the context of pull-down assay results. Consequently, such rankings can reduce the number of confirmatory biochemical experiments needed to find bona fide protein-protein interactions. In general, rankings based on dissimilarity measures generated through metric learning further reduce the required number of experiments compared to those based on standard dissimilarity measures such as Euclidean distance. When a protein mixture's melting curves are obtained in two conditions, we propose a scoring function that uses melting curve data to inform how likely a protein pair is to interact in one condition but not another. We show that ranking protein pairs by their scores is an effective approach for determining condition-specific protein-protein interactions. By contrast, clustering melting curve data generally does not inform about the interacting proteins in multiprotein complexes. In conclusion, we report improved methods for dissimilarity measure-based computation of melting curves data that can greatly enhance the determination of interacting proteins in multiprotein complexes.

Structures of Ric-8B in complex with Gα protein folding clients reveal isoform specificity mechanisms

Mammalian Ric-8 proteins act as chaperones to regulate the cellular abundance of heterotrimeric G protein α subunits. The Ric-8A isoform chaperones Gαi/o, Gα12/13, and Gαq/11 subunits, while Ric-8B acts on Gαs/olf subunits. Here, we determined cryoelectron microscopy (cryo-EM) structures of Ric-8B in complex with Gαs and Gαolf, revealing isoform differences in the relative positioning and contacts between the C-terminal α5 helix of Gα within the concave pocket formed by Ric-8 α-helical repeat elements. Despite the overall architectural similarity with our earlier structures of Ric-8A complexed to Gαq and Gαi1, Ric-8B distinctly accommodates an extended loop found only in Gαs/olf proteins. The structures, along with results from Ric-8 protein thermal stability assays and cell-based Gαolf folding assays, support a requirement for the Gα C-terminal region for binding specificity, and highlight that multiple structural elements impart specificity for Ric-8/G protein binding.

Population-based heteropolymer design to mimic protein mixtures

Biological fluids, the most complex blends, have compositions that constantly vary and cannot be molecularly defined1. Despite these uncertainties, proteins fluctuate, fold, function and evolve as programmed2–4. We propose that in addition to the known monomeric sequence requirements, protein sequences encode multi-pair interactions at the segmental level to navigate random encounters5,6; synthetic heteropolymers capable of emulating such interactions can replicate how proteins behave in biological fluids individually and collectively. Here, we extracted the chemical characteristics and sequential arrangement along a protein chain at the segmental level from natural protein libraries and used the information to design heteropolymer ensembles as mixtures of disordered, partially folded and folded proteins. For each heteropolymer ensemble, the level of segmental similarity to that of natural proteins determines its ability to replicate many functions of biological fluids including assisting protein folding during translation, preserving the viability of fetal bovine serum without refrigeration, enhancing the thermal stability of proteins and behaving like synthetic cytosol under biologically relevant conditions. Molecular studies further translated protein sequence information at the segmental level into intermolecular interactions with a defined range, degree of diversity and temporal and spatial availability. This framework provides valuable guiding principles to synthetically realize protein properties, engineer bio/abiotic hybrid materials and, ultimately, realize matter-to-life transformations.

Nonionic Surfactants can Modify the Thermal Stability of Globular and Membrane Proteins Interfering with the Thermal Proteome Profiling Principles to Identify Protein Targets.

The membrane proteins are essential targets for understanding cellular function. The unbiased identification of membrane protein targets is still the bottleneck for a system-level understanding of cellular response to stimuli or perturbations. It has been suggested to enrich the soluble proteome with membrane proteins by introducing nonionic surfactants in the solubilization solution. This strategy aimed to simultaneously identify the globular and membrane protein targets by thermal proteome profiling principles. However, the thermal shift assay would surpass the cloud point temperature from the nonionic surfactants frequently utilized for membrane protein solubilization. It is expected that around the cloud point temperature, the surfactant micelles would suffer structural modifications altering protein solubility. Here, we show that the presence of nonionic surfactants can alter protein thermal stability from a mixed, globular, and membrane proteome. In the presence of surfactant micelles, the changes in protein solubility analyzed after the thermal shift assay was affected by the thermally dependent modification of the micellar size and its interaction with proteins. We demonstrate that the introduction of nonionic surfactants for the solubilization of membrane proteins is not compatible with the principles of target identification by thermal proteome profiling methodologies. Our results lead to exploring thermally independent strategies for membrane protein solubilization to assure confident membrane protein target identification. The proteome-wide thermal shift methods have already shown their capability to elucidate mechanisms of action from pharma, biomedicine, analytical chemistry, or toxicology, and finding strategies, free from surfactants, to identify membrane protein targets would be the next challenge.

Thermal Stability of Contractile Proteins in Bat Wing Muscles Explains Differences in Temperature Dependence of Whole-Muscle Shortening Velocity.

AbstractMuscle contractile properties are dependent on temperature: cooler temperatures generally slow contractile rates. Contraction and relaxation are driven by underlying biochemical systems, which are inherently sensitive to temperature. Carollia perspicillata, a small Neotropical bat, experiences large temperature differentials among body regions, resulting in a steep gradient in temperature along the wing. Although the bats maintain high core body temperatures during flight, the wing muscles may operate at more than 10°C below body temperature. Partially compensating for these colder operating temperatures, distal wing muscles have lower temperature sensitivities in their contractile properties, including shortening velocity, relative to the proximal pectoralis. Shortening velocity is correlated with the activity of myosin ATPase, an enzyme that drives the cross-bridge cycle. We hypothesized that the thermal properties of myofibrillar ATPase from the pectoralis and forearm muscles of the bat wing would correlate with the temperature sensitivity of those muscles. Using myofibrillar ATPases from the proximal and distal muscles, we measured enzyme activity across a range of temperatures and enzyme thermal stability after heat incubation across a range of time points. We found that forearm muscle myofibrillar ATPase was significantly less thermally stable than pectoralis myofibrillar ATPase but that there was no significant difference in the acute temperature dependence of enzyme activity between the two muscles.

DeepTM: A deep learning algorithm for prediction of melting temperature of thermophilic proteins directly from sequences

Thermally stable proteins find extensive applications in industrial production, pharmaceutical development, and serve as a highly evolved starting point in protein engineering. The thermal stability of proteins is commonly characterized by their melting temperature (Tm). However, due to the limited availability of experimentally determined Tm data and the insufficient accuracy of existing computational methods in predicting Tm, there is an urgent need for a computational approach to accurately forecast the Tm values of thermophilic proteins. Here, we present a deep learning-based model, called DeepTM, which exclusively utilizes protein sequences as input and accurately predicts the Tm values of target thermophilic proteins on a dataset consisting of 7790 thermophilic protein entries. On a test set of 1550 samples, DeepTM demonstrates excellent performance with a coefficient of determination (R2) of 0.75, Pearson correlation coefficient (P) of 0.87, and root mean square error (RMSE) of 6.24 ℃. We further analyzed the sequence features that determine the thermal stability of thermophilic proteins and found that dipeptide frequency, optimal growth temperature (OGT) of the host organisms, and the evolutionary information of the protein significantly affect its melting temperature. We compared the performance of DeepTM with recently reported methods, ProTstab2 and DeepSTABp, in predicting the Tm values on two blind test datasets. One dataset comprised 22 PET plastic-degrading enzymes, while the other included 29 thermally stable proteins of broader classification. In the PET plastic-degrading enzyme dataset, DeepTM achieved RMSE of 8.25 ℃. Compared to ProTstab2 (20.05 ℃) and DeepSTABp (20.97 ℃), DeepTM demonstrated a reduction in RMSE of 58.85% and 60.66%, respectively. In the dataset of thermally stable proteins, DeepTM (RMSE=7.66 ℃) demonstrated a 51.73% reduction in RMSE compared to ProTstab2 (RMSE=15.87 ℃). DeepTM, with the sole requirement of protein sequence information, accurately predicts the melting temperature and achieves a fully end-to-end prediction process, thus providing enhanced convenience and expediency for further protein engineering.

Effects of HMW-GS Dx2 absence on the protein aggregation characteristics and thermal stability of wheat flour during maturation

Abstract Background Wheat flour maturation affects the aggregation and structural stability of proteins. The number of high-molecular-weight glutenin subunits (HMW-GSs) differs in various wheat varieties. The effects of Dx2 absence on the protein aggregation characteristics and thermal stability of flour were investigated during 120 d of maturation using near-isogenic lines (NILs). Results The absence of Dx2 delayed and decreased the protein aggregation of flours during maturation, i.e. the maturation-induced increases were later and smaller for glutenin, glutenin macropolymer (GMP), glutenin/gliadin ratio, β-sheets, and β-sheet/α-helix ratio in HMW-D1a without Dx2 than in HMW-D1p with Dx2; these differences were ascribed to the weaker interactions between the sulfhydryl (-SH) groups, disulfide bonds (-S-S-), and hydrophobicity in the flours without Dx2. Flour maturation caused the dough microstructures to be more compact and denser, thereby increasing the flour thermal stability as observed by a higher denaturation peak temperature (Tp), enthalpy of thermal transition (ΔH), and degradation temperature (Td), These changes led to better dough properties such as dough development time, dough stability time, and protein weakening, but the optimal stage in HMW-D1a without Dx2 was reached later. Conclusion These findings deepen the understanding of how HMW-GS Dx2 modifies protein structures during flour maturation.

Thermal Proteome Profiling for Drug Target Identification and Probing of Protein States.

Proteins are central drivers of physiological and pathological processes in the cell. Methods evaluating protein functional states are therefore vital to fundamental research as well as drug discovery. Thermal proteome profiling (TPP) to this date constitutes the only approach that permits examining protein states in live cells, under native conditions and at a proteome-wide scale. TPP harnesses ligand/perturbation-induced changes in protein thermal stability, which are monitored by multiplexed quantitative mass spectrometry. In this chapter, we describe a modular experimental workflow for TPP experiments using live cells or crude cell extracts. We provide the tools to perform different TPP formats, i.e., temperature range experiments, TPP-TR; isothermal compound titrations, TPP-CCR; and a combination thereof, 2D-TPP.

Enhancement of pea protein solubility and thermal stability for acidic beverage applications via endogenous Maillard-induced glycation and chromatography purification

A clean-label process to endogenously glycate and purify pea protein was investigated. The production of maltodextrin from pea starch with a specific dextrose equivalent (DE) was optimized. The produced maltodextrin (14.6 DE) was used to initiate a limited and controlled Maillard-induced glycation of pea protein. The partially glycated pea protein (PG-PP) was subjected to hydrophobic interaction chromatography to remove unreacted carbohydrate, followed by characterization of the purified product. The extent of Maillard-induced glycation was monitored by assessing changes in color, free amino groups, and protein/glycoprotein profiles. The purified PG-PP was evaluated for thermal denaturation, surface properties, protein secondary structure, protein solubility, thermal stability, and digestibility. Maillard-induced glycation was limited to initial stages and resulted in a moderate blockage of amine groups (∼30%). The purified PG-PP had a relatively low surface hydrophobicity, a markedly enhanced protein solubility (∼90%) at pH 3.4, and a nonimpacted protein in vitro digestibility (∼100%). This work provided the impetus needed for future scale-up and process optimization for the production of value-added pea protein ingredient intended for high protein beverage applications.

Quantitative differentiation of benign and misfolded glaucoma-causing myocilin variants on the basis of protein thermal stability.

Accurate predictions of the pathogenicity of mutations associated with genetic diseases are key to the success of precision medicine. Inherited missense mutations in the myocilin (MYOC) gene, within its olfactomedin (OLF) domain, constitute the strongest genetic link to primary open-angle glaucoma via a toxic gain of function, and thus MYOC is an attractive precision-medicine target. However, not all mutations in MYOC cause glaucoma, and common variants are expected to be neutral polymorphisms. The Genome Aggregation Database (gnomAD) lists ∼100 missense variants documented within OLF, all of which are relatively rare (allele frequency <0.001%) and nearly all are of unknown pathogenicity. To distinguish disease-causing OLF variants from benign OLF variants, we first characterized the most prevalent population-based variants using a suite of cellular and biophysical assays, and identified two variants with features of aggregation-prone familial disease variants. Next, we considered all available biochemical and clinical data to demonstrate that pathogenic and benign variants can be differentiated statistically based on a single metric: the thermal stability of OLF. Our results motivate genotyping MYOC in patients for clinical monitoring of this widespread, painless and irreversible ocular disease.

Hyperthermostable recombinant human heteropolymer ferritin derived from a novel plasmid design.

Mammalian ferritins are predominantly heteropolymeric species consisting of 2 structurally similar, but functionally and genetically distinct subunit types, called H (Heavy) and L (Light). The two subunits co-assemble in different H and L ratios to form 24-mer shell-like protein nanocages where thousands of iron atoms can be mineralized inside a hollow cavity. Here, we use differential scanning calorimetry (DSC) to study ferritin stability and understand how various combinations of H and L subunits confer aspects of protein structure-function relationships. Using a recently engineered plasmid design that enables the synthesis of complex ferritin nanostructures with specific H to L subunit ratios, we show that homopolymer L and heteropolymer L-rich ferritins have a remarkable hyperthermostability (Tm=115 ± 1°C) compared to their H-ferritin homologues (Tm=93 ± 1°C). Our data reveal a significant linear correlation between protein thermal stability and the number of L subunits present on the ferritin shell. A strong and unexpected iron-induced protein thermal destabilization effect (ΔTm up to 20°C) is observed. To our knowledge, this is the first report of recombinant human homo- and hetero-polymer ferritins that exhibit surprisingly high dissociation temperatures, the highest among all known ferritin species, including many known hyperthermophilic proteins and enzymes. This extreme thermostability of our L and L-rich ferritins may have great potential for biotechnological applications.

Assessment of Thermal Stability of Mutant p53 Proteins via Differential Scanning Fluorimetry.

The p53 protein is a transcription factor that preserves the integrity of the genome. The TP53 gene has inactivating mutations in about 50% of all human cancers. Some missense mutations lead to decreased thermal stability in the p53 protein, its unfolding and aggregation under physiological conditions. A general understanding of the impact of point mutations on the stability and conformation of mutant p53 is essential for the design and development of small molecules that target specific p53 mutations. In this work, we determined the thermostability properties of some of the most common mutant forms of the p53 protein-p53(R273H), p53(R248Q), p53(R248W) and p53(Y220C)-that are often considered as attractive therapeutic targets. The results showed that these missense mutations lead to destabilization of the p53 protein and a decrease in its melting temperature.

Fabrication, characterization, and application of catechin-dextran-egg white protein conjugates: Novel antioxidant emulsifiers

The aim of this study was to fabricate dual-function antioxidant emulsifiers using natural ingredients. Catechin-dextran-egg white protein (EC-Dex-EWP) conjugates were prepared using a two-step method: (i) free radical grafting of dextran to EC; (ii) attachment of EC-Dex to EWP using the Maillard reaction. The total phenolic equivalent of the conjugates formed was 4.91 mg EC per gram of conjugate and the free amino content decreased by 19.2% compared to EWP. The formation of EC-Dex-EWP conjugates was confirmed by electrophoresis, infrared spectroscopy, and fluorescence spectroscopy. The interfacial tension of the conjugates was higher than for pure proteins, which was attributed to their larger molecular weight and lower hydrophobicity that EWP. The conjugation of EC-Dex to EWP did not affect the solubility of the protein but it did improve its emulsifying properties. The thermal stability of proteins was improved through Maillard reaction. Moreover, the conjugates also exhibited a stronger antioxidant activity, which was attributed to the presence of polyphenols. Our results suggest that the protein-polysaccharide-polyphenol conjugates developed in this study have potential as novel surface-active antioxidants for improving the physicochemical stability of emulsion-based foods.

Improvement of structural characteristics and in vitro digestion properties of zein by controlling postharvest ripening process of corn

The newly harvested corn was stored at constant temperature (15 and 25 °C) and relative humidity (55%). The structural characteristics and in vitro digestion properties of zein as well as their structure-function relationship during postharvest ripening of corn were analyzed. The free sulfhydryl content and surface hydrophobicity decreased and the disulfide bonds and absolute value of ζ-potential increased during postharvest ripening of corn for 56 days at two storage temperatures. The particle size and polydispersity index reached the minimum values when postharvest ripening for 28 days. The association of hydrogen bonds for zein was decreased and more β-sheets were transformed into random coils in the postharvest ripening period, leading to the reduction in thermal stability and enthalpy change of zein. In addition, the molecular weight of α-zein decreased when postharvest ripening at 15 °C for 28 days, and changed little during postharvest ripening at 25 °C. In vitro simulated digestion experiment proved that the maximum degree of hydrolysis of zein was appeared when postharvest ripening for 28 days at both two storage temperatures, which was higher at 15 °C than at 25 °C. This indicated that appropriate postharvest ripening behavior could improve the digestibility of zein. The reduction of protein aggregation extent and thermal stability as well as enhanced disordered secondary structure of zein might be important factors to improve its digestibility during the postharvest ripening. The results suggested that controlling the postharvest ripening process of corn could modify the structure of zein and improve its digestion properties. • Postharvest ripening of corn was performed at constant temperature and humidity. • Aggregation, thermal stability and ordered secondary structure of zein reduced. • Degree of hydrolysis for zein was highest by postharvest ripening for 28 days. • Improvement of zein digestibility was related to its structural modification. • Controlling postharvest ripening process of corn improved digestion property of zein.

Laser Heating Nanoelectrospray Emitters for Fast Protein Melting Measurements with Mass Spectrometry.

Temperature-controlled nanoelectrospray ionization has been used to measure heat-induced conformational changes of biomolecules by mass spectrometry, but long thermal equilibration times associated with heating or cooling an entire emitter limit how fast these data can be acquired. Here, the tip of a borosilicate electrospray emitter is heated using 10.6 μm light from an unfocused CO2 laser. At 1.2 W, the solution inside the emitter tip can be heated from room temperature to a steady-state temperature of 78.2 ± 2.5 °C in less than 0.5 s and cools from 82.6 ± 0.6 °C back to room temperature within 4 s. The time required to establish a steady-state temperature is more than 100-fold faster than that required for a resistively heated emitter due to the low thermal mass. Protein unfolding curves measured as a function of laser power can be acquired in ∼40 s compared to a resistively heated apparatus that required ∼21 min to acquire similar data. Laser power is calibrated to temperature by comparisons of the average charge state of the protein cytochrome c measured with laser heating and with resistive heating. This laser heating method is applied to a three-component protein mixture to demonstrate the ability to rapidly acquire melting temperatures of proteins in mixtures. The ability to rapidly assess the thermal stabilities of multiple proteins simultaneously shows significant promise for coupling temperature-controlled electrospray ionization (ESI) to separation techniques, providing a high-throughput method for determining the effects of solution composition, drug binding, or sequence mutations on protein thermal stability.

Characterization of proteases from Irpex lacteus grown on minimally denatured soybean meal.

Acid and thermal stabilities are important properties for the preparation of acidic protein beverage. It is an important method for enzymatic modification to improve the functional properties of protein. Irpex lacteus protease showed a selective hydrolysis to soy proteins. The purpose of this study was to investigate the mechanism of enzymatic hydrolysis and its effects on acid and thermal stabilities of soy proteins. The I.lacteus protease selectively hydrolyzed the α and α' subunits of the native soybean β-conglycinin (7S globulin) to produce products that presented as the 55 kDa band upon sodium dodecyl sulfate polyacrylamide gel electrophoresis. The amino acid sequences of 55 kDa polypeptides were analyzed in gel multi-enzyme digestion followed by liquid chromatography-mass spectrometry. By matching the multi-enzyme digestion peptides with the published polypeptide chain sequences of the α and α' subunits, it was confirmed that the 55 kDa polypeptides were formed by eliminating amino acid residues on both sides of the N- and C-terminals. From the published protein structure database (https://www.uniprot.org/), it is known that the cleaved peptide bonds were in extension regions. Non-selective enzyme hydrolysis of both β-conglycinin (7S globulin) and glycinin (11S globulin), with corresponding drastic increases in the degree of hydrolysis, was observed when the substrates were preheated to the denaturation degree of 40% and above. However, 55 kDa hydrolyzed products and B polypeptides showed some extent of resistance to the proteolysis by I.lacteus protease even if denaturation degree was 100%. Both selective and non-selective hydrolysis of soy proteins by I.lacteus protease improved the acid and heat stabilities under the same hydrolysis conditions (enzyme/substrate ratio, time, and temperature). Enzymatic hydrolysis of soybean proteins by the I.lacteus protease can effectively improve the acid and thermal stabilities of proteins. This discovery is significant to avoid aggregation during processing in the beverage industry. In the near future, the protease has potential application value for modification of other proteins. © 2022 Society of Chemical Industry.

Covalent interactions between rabbit myofibrillar proteins and quercetin: A promising approach to enhance protein antioxidant capacity and thermal stability

Meat-derived protein is suitable for converting into medical fluid food because of its high nutritional value, but industrial heat-treatment is easy to lead to fluid protein aggregation and sedimentation. The pH-shift method was utilized for production of rabbit myofibrillar proteins (MPs)-quercetin conjugates to enhance MPs thermal stability. The MPs-quercetin conjugates showed improved in water solubility compared to free quercetin (from 3.64 μg/mL to 54.83 μg/mL at 100 μmol/g protein), thus elevating the antioxidant capacity. The conjugates simultaneously imparted MPs to better thermal stability, as the quercetin concentration increased, the solubility of heat-treated MPs increased from 18.34% to 80.53% while high quercetin concentration (100 μmol/g protein) caused a decrease in solubility (68.33%, p < 0.05) due to excessive cross-linking of the myosin head and tail. Nano LC-ESI-MS/MS confirmed the amino acids conjugated with quercetin mainly included lysine and arginine, but less conjugated with sulfur-containing amino acids. Enhanced thermal stability was related to the steric hindrance provided by MPs-quercetin aggregates with different molecular weights. Quercetin could also mask the hydrophobic groups on the surface of MPs and enhance the hydrophilicity of protein, thus contribute critically to the dispersion stability after heating.

Effects of Ultrasound-Assisted Immersion Freezing on the Protein Structure, Physicochemical Properties and Muscle Quality of the Bay Scallop (Argopecten irradians) during Frozen Storage.

In this study, the comparison effects of ultrasound-assisted immersion freezing (UIF) at different ultrasonic power, immersion freezing (IF), and air freezing (AF) on the protein thermal stability, protein structure, and physicochemical properties of adductor muscle of scallop (Argopecten irradians) (AMS) during frozen storage were investigated. Principal component analysis and the Taylor diagram were used to comprehensively analyze all the indicators tested. The results showed that the UIF at 150 W (UIF-150) treatment was the most effective way to delay the quality deterioration of AMS during 90-day frozen storage. This was mainly because, compared to AF and IF treatments, UIF-150 treatment more effectively minimized the changes in the primary, secondary and tertiary structures of myofibrillar proteins, and it preserved the protein thermal stability of AMS by producing small and regular ice crystals in the AMS tissue during the freezing process. Moreover, the results of physicochemical properties indicated that UIF-150 treatment significantly inhibited the fat oxidation and microbiological activities of frozen AMS, and it finally maintained the microstructure and texture of AMS during frozen storage. Overall, UIF-150 has potential industrial application prospects in the rapid freezing and quality preservation of scallops.