Heightened Cold-Denaturation of Proteins at the Ice–Water Interface

Short-clustered maltodextrin mediates stabilization of gluten proteins during frozen storage compared to trehalose and guar gum

To investigate impacts of short-clustered maltodextrin (SCMD), trehalose (TH), and guar gum (GUAR) on mediating stabilizations of gluten proteins against cold denaturation, we focused on conformational transformations of gluten protein during frozen storage and its molecular mechanism. Firstly, we found SCMD markedly improved hydration features and decreased the surface hydrophilicity of gluten proteins, with the integrity and continuity of gluten network improving after 8-week frozen storage, compared to TH and GUAR. Furthermore, SCMD and TH addition hindered the conversion of α-helix to disordered β-fold and β-turn, while GUAR did not. Similar outcomes were observed in results of amino acid microenvironment. Molecular mechanism mining indicated the SCMD could establish additional hydrogen bonds with water and protein molecules, suppressing cold denaturation of protein. Our findings found saccharide composition and size were important factors in mediating protein stabilization during frozen storage, which will offer novel insights into the mitigation of cold-induced protein denaturation.

A novel strategy for using ficin enzyme from fig leaves to extract collagen from tannery-trimming wastes

There is a growing interest in the utilization of animal by-products and wastes. Plant-derived enzymes could play a vital role in collagen extraction from tannery-trimming wastes. Here, the ficin enzyme from fig leaves was used for collagen extraction and compared with conventional acetic acid and pepsin extraction methods, aiming to assess the efficiency and purity of collagen extracted using this plant-based enzyme approach relative to the organic solvents and animal-derived enzymes. The extracted collagen was identified as type I collagen. Response surface methodology analysis revealed that the ficin enzyme-soluble collagen yielded 15.28 % at a hydrolysis time of 39.27 h, a ficin enzyme dose of 5.54 %, and a mixing ratio of 15.87, higher than the acetic acid-soluble collagen yield of 9.52 % and pepsin enzyme-soluble collagen yield of 14.56 %. Ficin enzyme-soluble collagen exhibited better integrity of the triple helical structure with fewer proteinaceous impurities, though it showed poorer thermal stability. Ultrasound treatment at 800 W for 30 min did not significantly disrupt the triple helical structure of collagen. The work aims to develop a green and sustainable method for extracting collagen from tannery-trimming wastes, offering a novel approach for the high-value conversion of animal by-products and agro-residues wastes.

Freezing-induced protein aggregation in a bispecific antibody: Characterization and mechanistic insights

Aggregation or formation of high molecular weight species (HMWS) was observed with a pharmaceutical bispecific antibody (BsAb) during freeze-thaw and storage at -20 °C, but not at -80 °C. Several freezing stresses that may drive the protein aggregation were evaluated, including temperature, freeze concentration, ice formation, cooling rate, and cold denaturation. Experiments designed to identify the main aggregation mechanism and the drivers revealed that protein dimerization is the main mechanism and protein interaction with ice is the main driver of the protein aggregation. Additionally, higher molecular mobility at -20 °C (compared to -80 °C) propagates the aggregation. Molecular structure modeling of the single-chain variable fragment (scFv) revealed the steric clashes between amino acid residues at the core of the interface between the variable heavy (VH) and variable light (VL) domains, could be an intrinsic driver of the protein aggregation. The study presents an interesting case of sequence-specific product quality liability for bispecifics and provides insights into strategies for prevention and mitigation of the liability.

Freeze-thaw of pharmaceutical solutions: counter-intuitive finding of an increase in mechanical stress between Tg" and Tg' in frozen sucrose/water mixtures

High-resolution synchrotron X-ray powder diffraction has been utilized to detect mechanical stresses in frozen solutions, via analysis of the profiles of the diffraction peaks of ice. Increase in the width of the peaks (peaks broadening) reflects disruption of the crystal lattice, with contributions including a decrease in the crystallite size and an increase in microstrain. Frozen sucrose solutions (5 and 10 % w/v) were frozen at 100 K and then heated and annealed at -45 °C (228 K) and -15 °C (258 K), i.e. between the two apparent glass transition events in the freeze-concentrated solutions (Tg" and Tg'), and above the Tg', respectively. A decrease in microstrain and an increase in ice crystallite size were observed during annealing at -15 °C (above the Tg'), which is consistent with Ostwald ripening of ice crystals. Unexpectedly, and for the first time, an opposite trend was observed during annealing at the lower temperature of -45 °C, between Tg" and Tg'. To the best of our knowledge, this is the first report of an increased strain in the crystalline ice domains and of simultaneous size reduction during annealing of frozen aqueous solutions. Considering that the interaction with ice crystals may result in protein destabilization, the size and microstrain of ice crystallites can serve as markers of the freeze/thaw stresses on biopharmaceuticals. A practical implication is that a prolonged hold between Tg" and Tg' may increase stress imposed on protein molecules, i.e. a lower temperature is not always better for preserving biopolymers when freezing their aqueous solutions.

Insights into myofibrillar protein denaturation during freezing: The impact of ice-water interface area

This study investigated the impact of the ice-water interface area on the denaturation of myofibrillar protein (MP) over 1, 3, and 5 freeze-thaw cycles. Experimental systems designed to generate ice-water interfaces with two distinct surface areas were established by employing rapid freezing at -80 °C and slow freezing at -25 °C, resulting in surface areas of 64.63 m2/100 mL and 54.05 m2/100 mL, respectively. Following three freeze-thaw cycles, the process of rapid freezing, characterized by formation of a larger ice-water interface area, was found to significantly influenced the functional properties of MP. The impact was evidenced by a reduction in solubility, total sulfhydryl content, and thermal denaturation temperature. Structural modifications in MP suggested that the larger ice-water interface led an accelerated rate of protein unfolding during freezing. Interfacial pressure and confocal laser scanning microscopy (CLSM) results demonstrated that the larger ice-water interface area could be more able to reduce protein interfacial adsorption and enhanced protein emulsion aggregation. The addition of 0.1 % surfactant Tween 80 prior to freezing markedly enhanced protein stability throughout both the freezing and subsequent freeze-thaw cycles. The findings suggested that to further inhibit MP frozen denaturation, it is important to consider limiting the expansion of ice-water interface area.

Water's Dual Role as a Chemical Catalyst and Physical Stabilizer in Deamidation of Lyophilized Proteins Studied via Molecular Dynamics Simulations

Water plays a critical role in chemical degradations, such as deamidation, in freeze-dried proteins. Two distinct patterns for deamidation in relation to water have been reported, that is a "hockey stick"-type behavior with a water-independent deamidation rate, followed by a sharp increase above a water content threshold, and an inverted bell-shaped profile. To understand the underlying mechanism, molecular dynamics simulations are employed to study the explicit water distributions around reactive sites for amorphous and crystalline insulin as well as amorphous IgG1. The simulated water distribution on the protein surface is first validated by successfully predicting water vapor sorption isotherms for both amorphous and crystalline insulin. The "hockey stick"-type behavior is explained by a water threshold level beyond which there are two (Asn-Gly sequence in IgG1) or three (Asn at the C-terminus in insulin) water molecules assisting the cyclization reactions. Regarding the inverted bell-shaped profile for amorphous IgG1, the initial decreases in deamidation rate with increasing water content at low water levels can be rationalized by a lower density and higher free volume of IgG1 at a lower water content. When the free volume exceeds a percolation threshold, the produced ammonia gas can easily diffuse away, lowering the back reaction rate and thus raising the overall reaction rate. The "free volume" mechanism can also be applied to the abnormal stability ranking orders of crystalline and amorphous insulin. The faster deamidation and dimerization rates in insulin crystals compared to amorphous insulin as reported by Pikal and Rigsbee are due to the lower density and higher free volume (above the percolation threshold) in crystalline insulin, assuming that dehydration of insulin crystals does not result in a major collapse of the crystal structure.

The graphene-based affinity cryo-EM grid for the endogenous protein structure determination

Following recent advancements in cryo-electron microscopy (cryo-EM) instrumentation and software algorithms, the next bottleneck in achieving high-resolution cryo-EM structures arises from sample preparation. To overcome this, we developed a graphene-based affinity cryo-EM grid, the Graffendor (GFD) grid, to target low-abundance endogenous protein complexes. To maintain grid quality and consistency within a single batch of 36 grids, we established a one-step crosslinking batch-production method using genetically modified ALFA nanobody as affinity probe (GFD-A grid). Using low concentrations of β-galactosidase-2xALFA, we demonstrated the GFD-A grid's efficiency in capturing tagged proteins and resolving its cryo-EM structure at 2.71 Å. To test its application for endogenous proteins, we engineered yeast cells with a C-terminal tandem affinity tag (3xALFA-Tev-3xFlag: ATF) at Pop6, a shared component of RNase MRP and RNase P. Cryo-EM structures of RNase MRP and RNase P were resolved at 3.3 Å and 3.0 Å from cell lysates, and 3.6 Å and 3.9 Å from anti-flag elution, respectively. Notably, additional densities were observed in the structures obtained from cell lysates, which were absent in those from the anti-FLAG eluate. These findings establish the GFD-A grid as a robust platform for investigating endogenous proteins, capable of capturing transient interactions and enhancing the resolution of challenging cryo-EM structures with greater efficiency.

Practical advice in the development of a lyophilized protein drug product

The development of lyophilized protein drug products is a critical and complex task in the pharmaceutical industry, requiring a comprehensive understanding of the myriad of factors affecting product quality, stability, and the efficiency and robustness of the lyophilization process. This review offers practical advice on the critical aspects of lyophilized protein drug product development. Practical considerations across both the early and late stages of development are discussed, underscoring the necessity of a strategic approach from initial development through to commercialization. The review then delves into formulation optimization strategies that are essential for enhancing protein stability and the efficiency of the lyophilization process. This section outlines stable formulation design and highlights the unique considerations required for high protein concentration lyophilized drug products. It further explores the formulation strategies to enhance the lyophilization process' efficiency. Moreover, the paper examines the critical elements in selecting primary containers and closures for lyophilized drug products, focusing on vials and dual chamber systems. The analysis encompasses the effects of the container/closure's material, size, geometry, and fill volume on product quality and process efficiency. Lastly, the review provides practical considerations in lyophilization cycle development, including the design and optimization of the freezing, primary drying, and secondary drying stages to achieve a robust, scalable, and efficient lyophilization process. By offering comprehensive insights into these key areas to enhance their understanding and implementation of best practices in the field, this paper serves as a useful resource for researchers, formulators, and process engineers involved in the development of lyophilized protein drug products.

The impacts of freeze-drying-induced stresses on the quality of meat and aquatic products: Mechanisms and potential solutions to acquire high-quality products

Freeze-drying is a preservation method known for its effectiveness in dehydrating food products while minimizing their deterioration. However, protein denaturation and oxidation during freezing and drying can degrade the quality of meat and aquatic products. Therefore, finding the strategies to ensure the dried products' sensory, functional, and nutritional attributes is crucial. This study aimed to summarize protein denaturation mechanisms and overall quality changes in meat and aquatic products during freezing and drying, while also exploring methods for quality control. Different freeze-drying conditions result in varying levels of oxidation and functionality in meat and aquatic products, leading to changes in quality, such as altered fatty and amino acid compositions, protein digestibility, and sensory attributes. To obtain high-quality dried products by freeze-drying, several parameters should be considered, including sample type, freezing and drying temperatures, moisture content, pulverization effects, and storage conditions.

Mitigating the Effects of Starch Derivatives on Cold Denaturation of Gluten Protein: Insights from Hydration Capacity and Conformation Behavior

Mitigating the cold denaturation of gluten protein during frozen storage is crucial for the quality improvement of frozen cereal products. Our previous study observed that starch derivatives, especially short-clustered maltodextrin (SCMD), could significantly improve frozen dough quality, alleviating the deterioration of gluten-network structure. To further reveal the cryoprotection mechanism of SCMD on gluten protein during frozen storage, the modulatory roles of SCMD in the hydration capacity and conformation behavior of gluten protein were explored, in comparison with DE2 maltodextrin (MD) and pregelatinized starch (PGS). Results demonstrated that SCMD significantly facilitated the reservation of bound water and decreased the surface hydrophobicity of gluten protein after 8 weeks of frozen storage. Remarkable effects of SCMD on stabilizing the secondary structure and microenvironment of aromatic amino acids of gluten protein were observed. Further mechanistic investigation showed that when the temperature dropped from 300 to 250 K, the short-clustered structure could stabilize the α-helixes more evidently than linear structures through hydrogen bonds with water and steric hindrance effect, rather than directly with protein. Our findings will provide novel insights into the cold denaturation of gluten protein and useful guidance in selecting the optimum structure to suppress this denaturation, improving the quality of frozen cereal products.

Reconsidering freeze-induced protein aggregation: Air bubbles as the root cause of ice-water interface stress

Freeze-induced stress causing aggregation of proteins has typically been primarily attributed to the ice-water interface. However, we hypothesize that the underlying observed and perceived detrimental effect of ice is, to some extent, attributed to air bubbles expelled from ice crystal lattices or to nanobubbles existing prior to freezing. The reduction of dissolved air was achieved via a deaeration process by placing samples in a reduced pressure chamber, while the reduction of nanobubbles was achieved by filtering samples via a syringe filter. The results showed that the reduction of both dissolved air molecules and stable colloidal nanobubbles in a bovine IgG solution prior to freezing led to a significant decrease in aggregation after thawing compared to untreated samples (∼6,000 vs. ∼ 40,000 particles/mL at a freezing rate of 100 K/s, respectively). The deaeration-filtration treatment works additively with cryoprotectants such as trehalose, further reducing the freeze-induced aggregation of IgG. The results also demonstrated that air-water interfacial aggregation of IgG in bulk liquid samples is a time-dependent process. The number of IgG subvisible particles increased with time and temperature, suggesting that random collisions of denatured molecules promoted the formation of aggregates with spherical morphology. In contrast, the IgG subvisible count after freeze-thawing had already reached its nominal value, suggesting a time-independent process where denatured protein molecules were compressed between ice crystals into filament-like aggregates. In summary, the findings shift the current paradigm from ice crystals being the main destabilizing factor during freezing to air bubbles, although the two are intertwined. From a translational aspect, this study underscores the value of deaeration-filtration as an essential supplemental process that can be applied in addition to formulation approaches such as the use of cryoprotectants to further reduce freezing stress on proteins and increase their stability.

Effect of water migration on changes of quality and volatile compounds in frozen Penaeus monodon

The purpose of this study was to clarify effects of water changes on the quality and volatile compounds of Penaeus monodon during frozen storage. The content of immobilized water decreased significantly while the bound water and free water increased significantly. Total sulfhydryl content, and Ca2+-ATPase activity decreased significantly to 68.31 μmol/g and 0.127 U/mg, meantime, carbonyl content and MFI value increased significantly to 2.04 μmol/g prot and 55.10. Total of 50 volatile compounds were identified. Nonanal (M & D), 2-nonanone and octanal were only detected in fresh samples, while 3-hydroxy-2-butanone and 1-hydroxy-2-propanone were only found in the samples after 20 days of storage. Correlation analysis revealed that 6 of the volatile compounds were associated with the change of free water. Total of 28 and 17 volatile compounds showed significant correlations with the immobilized water and bound water, respectively. Four volatile compounds have the potential to be used as the flavor marker.

Directional freezing and thawing of biologics in drug substance bottles

Biological drug substance (DS) is typically stored frozen to increase stability. However, freezing and thawing (F/T) of DS can impact product quality and therefore F/T processes need to be controlled. Because active F/T systems for DS bottles are lacking, freezing is often performed uncontrolled in conventional freezers, and thawing at ambient temperature or using water baths. In this study, we evaluated a novel device for F/T of DS in bottles, which can be operated in conventional freezers, generating a directed air stream around bottles. We characterized the F/T geometry and process performance in comparison to passive F/T using temperature mapping and analysis of concentration gradients. The device was able to better control the F/T process by inducing directional bottom-up F/T. As a result, it reduced cryo-concentration during freezing as well as ice mound formation. However, freezing with the device was dependent on freezer performance, i.e. prolonged process times in a highly loaded freezer were accompanied by increased cryo-concentrations. Thawing was faster compared to without the device, but had no impact on concentration gradients and was slower compared to thawing in a water bath. High-performance freezers might be required to fully exploit the potential of directional freezing with this device and allow F/T process harmonization and scaling across sites.

A comprehensive review on freeze-induced deterioration of frozen egg yolks: Freezing behaviors, gelation mechanisms, and control techniques

Over the years, the production of eggs has increased tremendously, with an estimated global egg production of 9.7 billion by 2050. Further processing of shell eggs to egg products has gained growing popularity. Liquid egg yolks, an innovative form of egg replacement, still suffer from short shelf-life issues, and freezing has been applied to maintain freshness. An undesirable phenomenon called "gelation" was found during the production of frozen egg yolks, which has attracted numerous scholars to study its mechanism and quality control methods. Therefore, we comprehensively reviewed the history of the studies on frozen egg yolks, including the production procedure, the fundamentals of freezing, the gelation mechanism, the factors affecting gelation behaviors, and the techniques to control the gelation behaviors of frozen egg yolks. Reporting the production procedure and freezing fundamentals of frozen egg yolks will give readers a better understanding of the science and technological aspects of frozen egg yolks. Furthermore, a comprehensive summary of the mechanism of egg yolk gel formation induced by freeze-thawing and relevant control techniques will provide insights to researchers and manufacturers in the field of frozen egg processing.

Probing the non-covalent forces key to the thermodynamics of β-hairpin unfolding

Although it is well understood that the graph of the free energy of unfolding (ΔG) of a globular protein with temperature approximates to a negative parabola, there is as yet no link between this global (G) ΔG G(T) function and the individual structural elements-residue type and the non-covalent forces between groups-contributing to it. As such, there is little understanding of how each structural element contributes to the globally assessed changes of enthalpy (ΔH G), entropy (ΔS G), and heat capacity (ΔC p(G)) of unfolding calculated from the ΔG G(T) function. To address this situation, we consider here an alternative approach to examining fold stability. Specifically, we examine the local (L) reporting of the thermodynamics of unfolding provided by each residue. By using 1H NMR spectroscopy to monitor the response of the individual mainchain amide N-H groups of β-hairpin peptides with temperature, we generate local ΔG L(T) functions, using these to calculate the local enthalpy (ΔH L), entropy (ΔS L), and heat capacity (ΔC p(L)) of unfolding. Mapping the thermodynamic changes in this way, for specific point-mutations, provides new information about how specific residues, non-covalent forces, and secondary structure type, contribute to folding. This type of information provides new details of the factors contributing to the typically measured global ΔG G(T) function.

Ice in the intertidal: patterns and processes of freeze tolerance in intertidal invertebrates

Many intertidal invertebrates are freeze tolerant, meaning that they can survive ice formation within their body cavity. Freeze tolerance is a fascinating trait, and understanding its mechanisms is important for predicting the survival of intertidal animals during extreme cold weather events. In this Review, we bring together current research on the ecology, biochemistry and physiology of this group of freeze-tolerant organisms. We first introduce the ecology of the intertidal zone, then highlight the strong geographic and taxonomic biases within the current body of literature on this topic. Next, we detail current knowledge on the mechanisms of freeze tolerance used by intertidal invertebrates. Although the mechanisms of freeze tolerance in terrestrial arthropods have been well-explored, marine invertebrate freeze tolerance is less well understood and does not appear to work similarly because of the osmotic differences that come with living in seawater. Freeze tolerance mechanisms thought to be utilized by intertidal invertebrates include: (1) low molecular weight cryoprotectants, such as compatible osmolytes and anaerobic by-products; (2) high molecular weight cryoprotectants, such as ice-binding proteins; as well as (3) other molecular mechanisms involving heat shock proteins and aquaporins. Lastly, we describe untested hypotheses, methods and approaches that researchers can use to fill current knowledge gaps. Understanding the mechanisms and consequences of freeze tolerance in the intertidal zone has many important ecological implications, but also provides an opportunity to broaden our understanding of the mechanisms of freeze tolerance more generally.

Insights into Thermal Interactions in Frozen Pharmaceutical Vials: Effects on Ice Nucleation Times and Inhibition

PURPOSE

This study investigates the thermal interactions between adjacent vials during freezing and assesses their impact on nucleation times.

METHODS

Various loading configurations were analyzed to understand their impact on nucleation times. Configurations involving direct contact between vials and freeze-dryer shelves were studied, along with setups using empty vials between filled ones. Additionally, non-conventional loading configurations and glycol-filled vials were tested. The analysis includes 2R and 20R vials, which are commonly utilized in the freezing and lyophilization of drug products, along with two different fill depths, 1 and 1.4 cm.

RESULTS

The investigation revealed that configurations with direct contact between vials and freeze-dryer shelves led to substantial thermal interactions, resulting in delayed nucleation in adjacent vials and affecting the temperature at which nucleation takes place in a complex way. In another setup, empty vials were placed between filled vials, significantly reducing thermal interactions. Further tests with non-conventional configurations and glycol-filled vials confirmed the presence of thermal interactions with a minimal inhibitory effect.

CONCLUSIONS

These findings carry significant implications for the pharmaceutical industry, highlighting the role of thermal interactions among vials during freezing and their impact on the temperature at which ice nucleation occurs.

Characterization of peptides released from frozen-then-aged beef after digestion in an in vitro infant gastrointestinal model

This study investigated whether the freezing-then-aging treatment of beef affects protein digestibility and release of potentially bioactive peptides using an in vitro infant digestion model. After 28 days of storage, aged-only (AO) and frozen-then-aged (FA) beef exhibited higher α-amino group contents in the 10% trichloroacetic acid-soluble fraction compared to day 0 (P < 0.05). Following in vitro digestion in the infant model, FA showed higher contents of α-amino groups and smaller proteins (<3 and 1 kDa) than day 0 and AO (P < 0.05). Relative contributions of myofibrillar, sarcoplasmic, and stromal proteins to the bioactive peptides released from AO and FA differed from those of day 0. In addition, FA exhibited a higher proportion of potential bioactive peptide sequences. Overall, freezing-then-aging treatment can enhance the potential health benefits of beef to be used as a protein source for complementary foods.

A green strategy for collagen extraction from tannery raw trimmings using papain enzyme: Process optimization by MW-TOPSIS for enhanced yield

The leather industry poses a significant environmental problem through the extensive discharge of trimming waste, primarily composed of skin matrix rich in proteins. Developing a green approach for utilizing this waste can contribute to the sustainable recovery of proteins, transforming them into valuable bioresources. This study introduces an environmentally friendly and economically viable approach to extract collagen from tannery raw trimming waste using papain enzyme-derived from papaya leaves. The research involved extensive assessments and trials to optimize the enzymatic hydrolysis process. The highest collagen recovery was achieved by hydrolyzing 5 % (w/v) delimed powder with 4 % (w/v) crude papain enzyme from papaya leaf powder, maintaining it at 60 °C for 6 h and at pH 5. Collagen extraction from raw trimming waste using acetic acid was also performed, with the optimized papain enzyme-based hydrolysis process resulting in approximately 91 % yield, while conventional acetic acid method yielded approximately 84 %. To evaluate the performance of the enzymatic hydrolysis process in comparison to acid hydrolysis and hydrothermal hydrolysis, an integrated MW-TOPSIS framework was proposed. This framework determined that enzymatic hydrolysis achieved the highest closeness coefficient value (Ri = 0.40), indicating its superiority as the preferred alternative among the tested methods.

Shear stress as a driver of degradation for protein-based therapeutics: More accomplice than culprit

Protein degradation is a major concern for protein-based therapeutics. It may alter the biological activity of the product and raise the potential for undesirable effects on the patients. Among the numerous drivers of protein degradation, shear stress has been the focus around which much work has revolved since the 1970s. In the pharmaceutical realm, the product is often processed through several unit operations, which include mixing, pumping, filtration, filling, and atomization. Nonetheless, the drug might be exposed to significant shear stresses, which might cooperatively contribute to product degradation, together with interfacial stress. This review presents fundamentals of shear stress about protein structure, followed by an overview of the drivers of product degradation. The impact of shear stress on protein stability in different unit operations is then presented, and recommendations for limiting the adverse effects on the biopharmaceutical formulations are outlined. Finally, several devices used to explore the effects of shear stress are discussed.

Poly(l-alanine-co-l-threonine succinate) as a Biomimetic Cryoprotectant

We synthesized a series of [(l-Ala)x-co-(l-Thr succinate)y] (PATs), which are analogous to natural antifreezing glycoprotein with the structure of [l-Ala-l-Ala-l-Thr disaccharide]n, by varying the composition and degree of succinylation while fixing their molecular weight (Mn) and Ala/Thr ratio at approximately 10-12 kDa and 2:1, respectively. We investigated their ice recrystallization inhibition (IRI), ice nucleation inhibition (INI), dynamic ice shaping (DIS), thermal hysteresis (TH), and protein cryopreservation activities. Both IRI and INI activities were greater for PATs with higher l-Ala content (PATs-3 and PATs-4) than those with lower l-Ala content (PATs-1 and PATs-2). DIS activity with faceted crystal growth was clearly observed in PATs-2 and PATs-4 with a high degree of succinylation. TH was small with <0.1 °C for all PATs and slightly greater for PATs with a high l-Ala content. Except for PATs-1, the protein (lactate dehydrogenase, LDH) stabilization activity was excellent for all PATs studied, maintaining LDH activity as high as that of fresh LDH even after 15 freeze-thaw cycles. To conclude, the cryo-active biomimetic PATs were synthesized by controlling the l-Ala content and degree of succinylation. Our results showed that PATs with an l-Ala content of 65-70% and degree of succinylation of 12-19% exhibited the cryo-activities of IRI, INI, and DIS, and particularly promising properties for the cryoprotection of LDH protein.

Uncovering the rheological properties basis for freeze drying treatment-induced improvement in the solubility of myofibrillar proteins

Myofibrillar proteins (MPs) are an important nutritional supplement and have great significance in sports training and rehabilitation therapy. Currently, MPs preservation is still disputed since they are vulnerable to degradation, polymerization, and denaturation. Freeze-drying is an emerging technology for protein preservation, its effects on the functionality of MPs from different sources have not yet been thoroughly studied. This study aims to evaluate the performance differences of freeze-drying in maintaining the functional characteristics of MPs from fish and mammalian sources, providing valuable insights for the processing and preservation of MPs, and providing nutritional support for nursing and rehabilitation. The results showed that freeze-drying was an efficient method for protein preservation, and the effects of freeze-drying on both fish and mammalian sources MPs were significant (p < 0.05) consistent. Specifically, whether before and after freeze-drying, the solubility of fish MPs (FMPs) was significant (p < 0.05) lower than that of mammalian MPs, while the foaming and emulsifying properties were significant (p < 0.05) higher than those of beef and sheep MPs (BMPs and SMPs, respectively). Furthermore, the most efficient protein concentration for freeze-drying was 10 mg/mL, and with this concentration, the gel strengths of BMPs and SMPs showed an insignificant difference (p > 0.05) after freeze-drying.

Application of Formulation Principles to Stability Issues Encountered During Processing, Manufacturing, and Storage of Drug Substance and Drug Product Protein Therapeutics

The field of formulation and stabilization of protein therapeutics has become rather extensive. However, most of the focus has been on stabilization of the final drug product. Yet, proteins experience stress and degradation through the manufacturing process, starting with fermentaition. This review describes how formulation principles can be applied to stabilize biopharmaceutical proteins during bioprocessing and manufacturing, considering each unit operation involved in prepration of the drug substance. In addition, the impact of the container on stabilty is discussed as well.

Capturing heterogeneous conformers of cobalamin riboswitch by cryo-EM

RNA conformational heterogeneity often hampers its high-resolution structure determination, especially for large and flexible RNAs devoid of stabilizing proteins or ligands. The adenosylcobalamin riboswitch exhibits heterogeneous conformations under 1 mM Mg2+ concentration and ligand binding reduces conformational flexibility. Among all conformers, we determined one apo (5.3 Å) and four holo cryo-electron microscopy structures (overall 3.0-3.5 Å, binding pocket 2.9-3.2 Å). The holo dimers exhibit global motions of helical twisting and bending around the dimer interface. A backbone comparison of the apo and holo states reveals a large structural difference in the P6 extension position. The central strand of the binding pocket, junction 6/3, changes from an 'S'- to a 'U'-shaped conformation to accommodate ligand. Furthermore, the binding pocket can partially form under 1 mM Mg2+ and fully form under 10 mM Mg2+ within the bound-like structure in the absence of ligand. Our results not only demonstrate the stabilizing ligand-induced conformational changes in and around the binding pocket but may also provide further insight into the role of the P6 extension in ligand binding and selectivity.

Nanocrystallites Modulate Intermolecular Interactions in Cryoprotected Protein Solutions

Studying protein interactions at low temperatures has important implications for optimizing cryostorage processes of biological tissue, food, and protein-based drugs. One of the major issues is related to the formation of ice nanocrystals, which can occur even in the presence of cryoprotectants and can lead to protein denaturation. The presence of ice nanocrystals in protein solutions poses several challenges since, contrary to microscopic ice crystals, they can be difficult to resolve and can complicate the interpretation of experimental data. Here, using a combination of small- and wide-angle X-ray scattering (SAXS and WAXS), we investigate the structural evolution of concentrated lysozyme solutions in a cryoprotected glycerol-water mixture from room temperature (T = 300 K) down to cryogenic temperatures (T = 195 K). Upon cooling, we observe a transition near the melting temperature of the solution (T ≈ 245 K), which manifests both in the temperature dependence of the scattering intensity peak position reflecting protein-protein length scales (SAXS) and the interatomic distances within the solvent (WAXS). Upon thermal cycling, a hysteresis is observed in the scattering intensity, which is attributed to the formation of nanocrystallites in the order of 10 nm. The experimental data are well described by the two-Yukawa model, which indicates temperature-dependent changes in the short-range attraction of the protein-protein interaction potential. Our results demonstrate that the nanocrystal growth yields effectively stronger protein-protein attraction and influences the protein pair distribution function beyond the first coordination shell.

Combining Molecular Dynamics Simulations and Biophysical Characterization to Investigate Protein-Specific Excipient Effects on Reteplase during Freeze Drying

We performed molecular dynamics simulations of Reteplase in the presence of different excipients to study the stabilizing mechanisms and to identify the role of excipients during freeze drying. To simulate the freeze-drying process, we divided the process into five distinct steps: (i) protein-excipient formulations at room temperature, (ii) the ice-growth process, (iii)-(iv) the partially solvated and fully dried formulations, and (v) the reconstitution. Furthermore, coarse-grained (CG) simulations were employed to explore the protein-aggregation process in the presence of arginine. By using a coarse-grained representation, we could observe the collective behavior and interactions between protein molecules during the aggregation process. The CG simulations revealed that the presence of arginine prevented intermolecular interactions of the catalytic domain of Reteplase, thus reducing the aggregation propensity. This suggests that arginine played a stabilizing role by interacting with protein-specific regions. From the freeze-drying simulations, we could identify several protein-specific events: (i) collapse of the domain structure, (ii) recovery of the drying-induced damages during reconstitution, and (iii) stabilization of the local aggregation-prone region via direct interactions with excipients. Complementary to the simulations, we employed nanoDSF, size-exclusion chromatography, and CD spectroscopy to investigate the effect of the freeze-drying process on the protein structure and stability.

Changes in beef protein digestibility in an in vitro infant digestion model with prefreezing temperatures and aging periods

The protein digestibility of beef at three prefreezing temperatures (freezing at -20 °C, F20; freezing at -50 °C, F50; and freezing at -70 °C, F70) and aging periods (4, 14, and 28 days) was investigated using an in vitro infant digestion model. The increased cathepsin B activity in the frozen-then-aged treatments (P < 0.05) resulted in a higher content of 10% trichloroacetic acid-soluble α-amino groups than in the aged-only group on days 14 and 28 (P < 0.05). F50 had the most α-amino groups in the digesta and digested proteins under 3 kDa on day 28 (P < 0.05), with the disappearance of actin band in the digesta electrophoretogram. The secondary and tertiary structures of myofibrillar proteins revealed that F50 underwent irreversible denaturation (P < 0.05), especially in the myosin fraction, while F20 and F70 showed protein renaturation during aging (P < 0.05). In general, prefreezing at -50 °C then aging can improve the in vitro protein digestibility of beef through freezing-induced structural changes.

Batch Production of High-Quality Graphene Grids for Cryo-EM: Cryo-EM Structure of Methylococcus capsulatus Soluble Methane Monooxygenase Hydroxylase

Cryogenic electron microscopy (cryo-EM) has become a widely used tool for determining the protein structure. Despite recent technical advances, sample preparation remains a major bottleneck for several reasons, including protein denaturation at the air-water interface, the presence of preferred orientations, nonuniform ice layers, etc. Graphene, a two-dimensional allotrope of carbon consisting of a single atomic layer, has recently gained attention as a near-ideal support film for cryo-EM that can overcome these challenges because of its superior properties, including mechanical strength and electrical conductivity. Here, we introduce a reliable, easily implemented, and reproducible method to produce 36 graphene-coated grids within 1.5 days. To demonstrate their practical application, we determined the cryo-EM structure of Methylococcus capsulatus soluble methane monooxygenase hydroxylase (sMMOH) at resolutions of 2.9 and 2.5 Å using Quantifoil and graphene-coated grids, respectively. We found that the graphene-coated grid has several advantages, including a smaller amount of protein required and avoiding protein denaturation at the air-water interface. By comparing the cryo-EM structure of sMMOH with its crystal structure, we identified subtle yet significant geometrical changes at the nonheme diiron center, which may better indicate the active site configuration of sMMOH in the resting/oxidized state.

Analysis of the Shear Stresses in a Filling Line of Parenteral Products: The Role of Tubing

Parenteral products appear to be sensitive to process conditions in bioprocessing steps, such as interfacial stress and shear stress. The combination of these elements is widely believed and proven to influence product stability, but the defined roles of these players in the product damage process have not yet been identified. The present work addresses a current industrial problem, by focusing on the analysis of shear stress on protein-based therapeutics flowing in tubing by means of Computational Fluid Dynamics simulations. The purpose of this article is not to pinpoint the mechanism triggering the damage of the product, but it represents the first step towards wider experimental investigations and introduces a new strategy to quantify the average shear stress. The field of scale-down approaches, used to scale the commercial process down to the laboratory level, is also explored. Since quality control is critical in the pharmaceutical realm, it is essential that the scale-down approach preserves the same stress exposure as the commercial scale, which in the present work is considered to be that resulting from shear effects. Therefore, a new approach for scaling down the commercial process is proposed, which has been compared with traditional approaches and shown to provide greater representativeness between the two scales.

Nanopore single-molecule biosensor in protein denaturation analysis

Unclear issues in protein studies include but not limited to the stability and denaturation mechanism in the presence of denaturants. Herein, we report a dynamic monitoring approach based on nanopore single-molecule biosensor, which can detect the protein's folding and unfolding transitions by recording a nanopore ionic current. When gradually increasing the concentration of denaturant guanidine hydrochloride (GdmCl), sensitive responses were observed with lysozyme unfolding. The emergence of the featured biphasic-pulse demonstrated the existence of a stable intermediate. It was the first time to experimentally confirm the dynamic equilibrium between the intermediate and the native states at single molecule level, therefore consolidating the standpoint of lysozyme denaturation process following the three-state model. Additionally, we got more insights into the conformation about the intermediate as globular-like structure, larger gyration radius, and enhanced positive charge density. We considered that the manner of denaturant toward lysozyme adopts the "direct" model based on stronger electrostatic and van der Waals forces. Nanopore biosensor exhibited excellent sensitivity with a low detection concentration of 280 pM and reproducibility in analysing the folding intermediate of lysozyme.

Freeze-Drying of Pharmaceuticals in Vials Nested in a Rack System-Part I: Freezing Behaviour

The distribution of biopharmaceuticals often requires either ultra-cold conditions or lyophilisation. In both cases, the drug product is frozen and, thus, exposed to similar stress conditions, which can be detrimental to its quality. However, these stresses can be inhibited or mitigated by a suitable formulation and/or an appropriate freezing design. This paper addresses how the key freezing parameters, i.e., ice nucleation temperature and cooling rate, impact the freezing behaviour of a sucrose-based formulation. The analysis included two loading configurations, vials directly resting on the shelf and nested in a rack system. The loading configuration affected the product freezing rate and the ice nucleation temperature distribution, resulting in larger ice crystals in the case of vials nested in a rack system. SEM micrographs and specific surface area measurements confirmed the different product morphology. Eventually, the different product morphology impacted the bioactivity recovery of lactate dehydrogenase.

Storage and Lyophilization of Pure Proteins

This chapter outlines empirical procedures for the storage of pure proteins with preservation of high levels of biological activity. It describes simple and workable means of preventing microbial contamination and proteolytic degradation and the use of various types of stabilizing additives. It sets out the principles of lyophilization (a complex process comprising freezing, primary drying, and secondary drying stages, otherwise known as freeze-drying). There follows a general procedure for the use of lyophilizer apparatus with emphasis on best practice and on pitfalls to avoid. The use of modulated differential scanning calorimetry to measure the glass transition temperature, a key parameter in the design and successful operation of lyophilization processes, is described. This chapter concludes with brief summaries of interesting recent work in the field.

The effect of mAb and excipient cryoconcentration on long-term frozen storage stability – Part 1: Higher molecular weight species and subvisible particle formation

Cryoconcentration upon large-scale freezing of monoclonal antibody (mAb) solutions leads to regions of different ratios of low molecular weight excipients, like buffer species or sugars, to protein. This study focused on the impact of the buffer species to mAb ratio on aggregate formation after frozen storage at −80 °C, −20 °C, and − 10 °C after 6 weeks, 6 months, and 12 months. An optimised sample preparation was established to measure T_g′ of samples with different mAb to histidine ratios via differential scanning calorimetry (DSC). After storage higher molecular weight species (HMWS) and subvisible particles (SVPs) were detected using size-exclusion chromatography (SEC) and FlowCam, respectively. For all samples, sigmoidal curves in DSC thermograms allowed to precisely determine T_g′ in formulations without glass forming sugars. Storage below T_g′ did not lead to mAb aggregation. Above T_g′, at −20 °C and − 10 °C, small changes in mAb and buffer concentration markedly impacted stability. Samples with lower mAb concentration showed increased formation of HMWS. In contrast, higher concentrated samples led to more SVPs. A shift in the mAb to histidine ratio towards mAb significantly increased overall stability. Cryoconcentration upon large-scale freezing affects mAb stability, although relative changes compared to the initial concentration are small. Storage below T_g′ completely prevents mAb aggregation and particle formation.

The effect of mAb and excipient cryoconcentration on long-term frozen storage stability – part 2: Aggregate formation and oxidation

We examined the impact of monoclonal antibody (mAb) and buffer concentration, mimicking the cryoconcentration found upon freezing in a 2 L bottle, on mAb stability during frozen storage. Upon cryoconcentration, larger protein molecules and small excipient molecules freeze-concentrate differently, resulting in different protein to stabiliser ratios within a container. Understanding the impact of these shifted ratios on protein stability is essential. For two mAbs a set of samples with constant mAb (5 mg/mL) or buffer concentration (medium histidine/adipic acid) was prepared and stored for 6 months at −10 °C. Stability was evaluated via size-exclusion chromatography, flow imaging microscopy, UV/Vis spectroscopy at 350 nm, and protein A chromatography. Dynamic light scattering was used to determine k_D values. Soluble aggregate levels were unaffected by mAb concentration, but increased with histidine concentration. No trend in optical density could be identified. In contrast, increasing mAb or buffer concentration facilitated the formation of subvisible particles. A trend towards attractive protein-protein interactions was seen with higher ionic strength. MAb oxidation levels were negatively affected by increasing histidine concentration, but became less with higher mAb concentration. Small changes in mAb and buffer composition had a significant impact on stability during six-month frozen storage. Thus, preventing cryoconcentration effects in larger freezing containers may improve long-term stability.

The Role of Cryoprotective Agents in Liposome Stabilization and Preservation

To improve liposomes’ usage as drug delivery vehicles, cryoprotectants can be utilized to prevent constituent leakage and liposome instability. Cryoprotective agents (CPAs) or cryoprotectants can protect liposomes from the mechanical stress of ice by vitrifying at a specific temperature, which forms a glassy matrix. The majority of studies on cryoprotectants demonstrate that as the concentration of the cryoprotectant is increased, the liposomal stability improves, resulting in decreased aggregation. The effectiveness of CPAs in maintaining liposome stability in the aqueous state essentially depends on a complex interaction between protectants and bilayer composition. Furthermore, different types of CPAs have distinct effective mechanisms of action; therefore, the combination of several cryoprotectants may be beneficial and novel attributed to the synergistic actions of the CPAs. In this review, we discuss the use of liposomes as drug delivery vehicles, phospholipid–CPA interactions, their thermotropic behavior during freezing, types of CPA and their mechanism for preventing leakage of drugs from liposomes.

Recent advances and persistent challenges in the design of freeze-drying process for monoclonal antibodies

Monoclonal antibodies constitute nowadays an important therapeutic class and the number of approved molecules for clinical uses continues to increase, achieving considerable part of the therapeutic market. Yet, the stability in solution of these biopharmaceuticals is often low. That's why freeze-drying has been and remains the method of choice to obtain monoclonal antibodies in the solid state and to improve their stability. The design of freeze-drying process and its optimization are still topical subjects of interest and the pharmaceutical industry is regularly challenged by the requirements of quality, safety and efficiency set by the regulatory authorities. These requirements imply a deep understanding of each step of the freeze-drying process, developing techniques to control the critical parameters and to monitor the quality of the intermediate and the final product. In addition to quality issues, the optimization of the freeze-drying process in order to reduce the cycle length is of great interest since freeze-drying is known to be an energy-expensive and time consuming process. In this review, we will present the recent literature dealing with the freeze-drying of monoclonal antibodies and focus on the process parameters and strategies used to improve the stability of these molecules and to optimize the FD process.

Effect of diffusion kinetics on the ice nucleation temperature distribution

The nucleation behavior of water is crucial in many fields, spanning meteorology, glaciology, biology, and astrophysics. We report observations suggesting an effect of diffusion kinetics in water on the heterogeneous immersion/contact mode nucleation temperature distribution of ice. We performed differential scanning calorimetry analyses of repeated freeze/thaw cycles and investigated the effect of several variables on the regularity of the nucleation temperature distributions obtained. We observed that the thawing temperature and residence time above 0 °C affect the width of the measured distributions. We explain the observed phenomena according to the diffusion behavior of an external nucleator. Specifically, conditions of enhanced diffusion of the nucleator translated into broader, more scattered distributions, while conditions of limited diffusion translated into narrower, more regular distributions. Lastly, based on our experimental findings, we propose a theoretical explanation centered on the temperature dependence of diffusion kinetics in water.

Freezing-induced denaturation of myofibrillar proteins in frozen meat

Freezing is commonly used to extend the shelf life of meat and meat products but may impact the overall quality of those products by inducing structural changes in myofibrillar proteins (MPs) through denaturation, chemical modification, and encouraging protein aggregation. This review covers the effect of freezing on the denaturation of MPs in terms of the effects of ice crystallization on solute concentrations, cold denaturation, and protein oxidation. Freezing-induced denaturation of MPs begins with ice crystallization in extracellular spaces and changes in solute concentrations in the unfrozen water fraction. At typical temperatures for freezing meat (lower than -18 °C), cold denaturation of proteins occurs, accompanied by an alteration in their secondary and tertiary structure. Moreover, the disruption of muscle cells triggers the release of cellular enzymes, accelerating protein degradation and oxidation. To minimize severe deterioration during the freezing and frozen storage of meat, there is a vital need to use an appropriate freezing temperature below the glass transition temperature and to avoid temperature fluctuations during storage to prevent recrystallization. Such an understanding of MP denaturation can be applied to determine the optimum freezing conditions for meat products with highly retained sensory, nutritional, and functional qualities.

In-vial printing and drying of biologics as a personalizable approach

This study addressed the need for a flexible (personalizable) production of biologics, allowing their stabilization in the solid state and processing of small batch volumes. Therefore, inkjet printing into vials followed by a gentle vacuum drying step at ambient temperature was investigated by screening different formulations with a 2²-full factorial design of experiments regarding printability. Human Serum Albumin (HSA) was used as a model protein in a wide range of concentrations (5 to 50 mg/ml), with (10 w/v%) and without the surfactant polysorbate 80 (PS80). PS80 was identified to positively affect the formulations by increasing the Ohnesorge number and stabilizing the printing process. The dispensed volumes with a target dose of 0.5 mg HSA were dried and analyzed concerning their residual moisture (RM) and protein aggregation. All investigated formulations showed an RM < 10 wt% and no significant induced protein aggregation as confirmed by Size Exclusion Chromatography (<2.5%) and Dynamic Light Scattering (Aggregation Index ≤ 2.5). Additionally, long-term printability and the available final dose after reconstitution were investigated for two optimized formulations. A promising formulation providing ∼93% of the targeted dose and a reconstitution time of 30 s was identified.

Exploration of high dimensional free energy landscapes by a combination of temperature-accelerated sliced sampling and parallel biasing

Temperature-accelerated sliced sampling (TASS) is an enhanced sampling method for achieving accelerated and controlled exploration of high-dimensional free energy landscapes in molecular dynamics simulations. With the aid of umbrella bias potentials, the TASS method realizes a controlled exploration and divide-and-conquer strategy for computing high-dimensional free energy surfaces. In TASS, diffusion of the system in the collective variable (CV) space is enhanced with the help of metadynamics bias and elevated-temperature of the auxiliary degrees of freedom (DOF) that are coupled to the CVs. Usually, a low-dimensional metadynamics bias is applied in TASS. In order to further improve the performance of TASS, we propose here to use a highdimensional metadynamics bias, in the same form as in a parallel bias metadynamics scheme. Here, a modified reweighting scheme, in combination with artificial neural network is used for computing unbiased probability distribution of CVs and projections of high-dimensional free energy surfaces. We first validate the accuracy and efficiency of our method in computing the four-dimensional free energy landscape for alanine tripeptide in vacuo. Subsequently, we employ the approach to calculate the eight-dimensional free energy landscape of alanine pentapeptide in vacuo. Finally, the method is applied to a more realistic problem wherein we compute the broad four-dimensional free energy surface corresponding to the deacylation of a drug molecule which is covalently complexed with a β-lactamase enzyme. We demonstrate that using parallel bias in TASS improves the efficiency of exploration of high-dimensional free energy landscapes.

Development of an atmospheric plasma jet device for versatile treatment of electron microscope sample grids

Atmospheric-pressure plasmas have been widely applied for surface modification and biomedical treatment because of their ability to generate highly reactive radicals and charged particles. In negative-stain electron microscopy (Neg-EM) and cryogenic electron microscopy (cryo-EM), plasmas have been used to generate hydrophilic surfaces and eliminate surface contaminants to embed specimens onto grids. In addition, plasma treatment is a prerequisite for negative-stain and Quantifoil grids, whose surfaces are coated with hydrophobic amorphous carbon. Although the conventional glow discharge system has been used successfully in this purpose, there has been no further effort to take an advantage from the recent progress in the plasma field. Here, we developed a nonthermal atmospheric plasma jet system as an alternative tool for treatment of surfaces. The low-temperature plasma is a nonequilibrium system that has been widely used in biomedical area. Unlike conventional glow discharge systems, the plasma jet system successfully cleans and introduces hydrophilicity on the grid surface in the ambient environment without a vacuum. Therefore, we anticipate that the plasma jet system will have numerous benefits, such as convenience and versatility, as well as having potential applications in surface modification for both negative-stain and cryo-EM grid treatment.

Impact of lyoprotectors on protein-protein separation in the solid state: Neutron- and X-ray-scattering investigation

BACKGROUND

Polyhydroxycompounds (PHC) are used as lyoprotectors to minimize aggregation of pharmaceutical proteins during freeze-drying and storage.

METHODS

Lysozyme/PHC mixtures with 1:1 and 1:3 (w/w) ratios are freeze-dried from either H₂O or D₂O solutions. Disaccharides (sucrose and trehalose), monosaccharide (glucose), and sugar alcohol (sorbitol) are used in the study. Small-angle neutron and X-ray scattering (SANS and SAXS) are applied to study protein-protein interaction in the freeze-dried samples.

RESULTS

Protein interaction peak in the freeze-dried mixtures has been detected by both SANS (D₂O-based samples only) and SAXS (both D₂O- and H₂O-based). In the 1:1 mixtures, protein separation distances are similar (center-of-mass distance of approx. 31 Å) between all lyoprotectors studied. Mixtures with a higher content of the disaccharides (1:3 ratio) have a higher separation distance of approx 40 Å. The higher separation could reduce protein-protein contacts and therefore be associated with less favourable aggregation conditions. In the 1:3 mixtures with glucose and sorbitol, complex SANS and SAXS/WAXS patterns are observed. The pattern for the glucose sample indicate two populations of lysozyme molecules, while the origin of multiple SAXS peaks in the lysozyme/sorbitol 1:3 mixture is uncertain.

CONCLUSIONS

Protein-protein separation distance is determined predominantly by the lyoprotector/protein weight ratio.

GENERAL SIGNIFICANCE

Use of SANS and SAXS improves understanding of mechanisms of protein stabilization by sugars in freeze-dried formulations, and provide a tool to verify hypothesis on relationship between protein/protein separation and aggregation propensity in the dried state.

Environmental factors modulating protein conformations and their role in protein aggregation diseases

The adverse physiological conditions have been long known to impact protein synthesis, folding and functionality. Major physiological factors such as the effect of pH, temperature, salt and pressure are extensively studied for their impact on protein structure and homeostasis. However, in the current scenario, the environmental risk factors (pollutants) have gained impetus in research because of their increasing concentrations in the environment and strong epidemiologic link with protein aggregation disorders. Here, we review the physiological and environmental risk factors for their impact on protein conformational changes, misfolding, aggregation, and associated pathological conditions, especially environmental risk factors associated pathologies.

Evaluation of Two Novel Scale-Down Devices for Testing Monoclonal Antibody Aggregation During Large-Scale Freezing

There is a need for representative small volume devices that reflect monoclonal antibody (mAb) aggregation during freezing and thawing (FT) in large containers. We characterised two novel devices that aim to mimic the stress in rectangular 2 L bottles. The first scale-down device (SDD) consists of a 125 mL bottle surrounded by a 3D printed cover that manipulates heat exchange. The second device, a micro scale-down device (mSDD), adapts cooling and heating of 10 mL vials to extend stress time. MAb aggregation upon repeated FT was evaluated considering formation of higher molecular weight species, subvisible particles, and the increase in hydrodynamic radius, polydispersity index, and optical density at 350 nm. Three different mAb solutions were processed. Both an unshielded 125 mL bottle and the SDD can be used to predict aggregation during FT in 2 L bottles. In specific cases the unshielded 125 mL bottle underestimates whereas the SDD slightly overestimates soluble aggregate formation. The mSDD increases aggregation compared to 10 mL vials but is less representative than the SDD. Ultimately, both SDDs enable characterisation of protein sensitivity to large-scale FT with two orders of magnitude less volume and are superior to simply using smaller bottles.

Processing Characteristics of Freeze-Dried Pork Powder for Meat Emulsion Gel

The processing characteristics of freeze-dried pork powder as raw meat for comminuted meat products were compared with those of freeze-thawed pork. The tertiary structural properties, oxidation, and solubility of proteins in the freeze-dried pork powder were investigated. In addition, the properties of the emulsion gels manufactured with freeze-dried pork powder (GFD) and freeze-thawed pork (GFT) at 1.5% and 2.0% NaCl were evaluated. The surface hydrophobicity and intrinsic tryptophan fluorescence intensity of myofibrillar proteins between the freeze-dried pork powder and freeze-thawed pork were similar. However, freeze-dried pork powder had higher carbonyl compounds and lower solubility of sarcoplasmic and myofibrillar proteins than freeze-thawed pork (p<0.05). GFD had higher cooking loss than GFT in 2.0% NaCl, and lower hardness and a* value of GFD were observed regardless of NaCl level (p<0.05). Moreover, GFD had higher malondialdehyde content than GFT at the two NaCl concentrations (p<0.05). Therefore, our study demonstrated that freeze-dried pork powder has lower functional properties than freeze-thawed pork as raw meat for comminuted meat products.