Changes In Secondary Structure Research Articles

Effects of specific disease mutations in non-muscle myosin 2A on its structure and function

Non-muscle myosin 2A (NM2A), a widely expressed class 2 myosin, is important for organizing actin filaments in cells. It cycles between a compact inactive 10S state, in which its regulatory light chain (RLC) is dephosphorylated, and a filamentous state in which the myosin heads interact with actin, and the RLC is phosphorylated. Over 170 missense mutations in MYH9, the gene that encodes the NM2A heavy chain have been described. These cause MYH9 disease, an autosomal-dominant disorder that leads to bleeding disorders, kidney disease, cataracts and deafness. Approximately two thirds of these mutations occur in the coiled-coil tail. These mutations could destabilise the 10S state and/or disrupt filament formation, or both. To test this, we determined the effects of six specific mutations using multiple approaches, including circular dichroism to detect changes in secondary structure, negative stain electron microscopy to analyse 10S and filament formation in vitro, and imaging of GFP-NM2A in fixed and live cells to determine filament assembly and dynamics. Two mutations in D1424 (D1424G and D1424N) and V1516M strongly decrease 10S stability and have limited effects on filament formation in vitro. In contrast, mutations in D1447 and E1841K, decrease 10S stability less strongly but increase filament lengths in vitro. The dynamic behaviour of all mutants was altered in cells. Thus, the positions of mutated residues and their roles in filament formation and 10S stabilisation are key to understanding their contributions to NM2A in disease.

Spidroins under the Influence of Alcohol: Effect of Ethanol on Secondary Structure and Molecular Level Solvation of Silk-Like Proteins.

Future sustainable materials based on designer biomolecules require control of the solution assembly, but also interfacial interactions. Alcohol treatments of protein materials are an accessible means to this, making understanding of the process at the molecular level of seminal importance. We focus here on the influence of ethanol on spidroins, the main proteins of silk. By large-scale atomistically detailed molecular dynamics (MD) simulations and interconnected experiments, we characterize the protein aggregation, secondary structure changes, molecular level origins of them, and solvation environment changes for the proteins, as induced by ethanol as a solvation additive. The MD and circular dichoroism (CD) findings jointly show that ethanol promotes ordered structure in the protein molecules, leading to an increase of helix content and turns but also increased aggregation, as revealed by dynamic light scattering (DLS) and light microscopy. The structural changes correlate at the molecular level with increased intramolecular hydrogen bonding. The simulations reveal that polar amino acids, such as glutamine and serine, are most influenced by ethanol, whereas glycine residues are most prone to be involved in the ethanol-induced secondary structure changes. Furthermore, ethanol engages in interactions with the hydrophobic alanine-rich regions of the spidroin, significantly decreasing the hydrophobic interactions of the protein with itself and its surroundings. The protein solutes also change the microstructure of water/ethanol mixtures, essentially decreasing the level of larger local clustering. Overall, the work presents a systematic characterization of ethanol effects on a widely used, common protein type, spidroins, and generalizes the findings to other intrinsically disordered proteins by pinpointing the general features of the response. The results can aid in designing effective alcohol treatments for proteins, but also enable design and tuning of protein material properties by a relatively controllable solvation handle, the addition of ethanol.

Biotransformation approaches using solid-state fermentation and germination with high-intensity ultrasound to produce added-value hemp protein nanoaggregates

Hemp protein, with superior nutritional content and high digestibility, has attracted significant interest in recent years. However, like other plant protein sources, hemp protein has still suffered from underutilization in industrial applications due to its poor solubility attributes. To overcome this limitation, this study aimed to use biotechnological approaches such as germination (1, 3, 5 days) and solid-state fermentation using Lactobacillusplantarum and Bacillus subtilis to enhance the physicochemical, functional, and bioactive properties of hemp protein. The high-intensity ultrasound combined with these treatments for further modifications. The protein recovery in the defatted flour increased by 42% in germinated isolates compared to the untreated isolate. The primary structure changes were proven by degrading high molecular weight proteins to lower weights in SDS-PAGE. The secondary and tertiary structure changes of isolates were observed in FTIR, CD spectra, DSC, and free SH groups. While the particle sizes of isolates were reduced by 83%, solubility increased by 133% in fermented and ultrasonicated isolates. Water, oil absorption capacities and emulsion activities were increased by 103%, 194%, and 300%, respectively, in modified isolates compared to the untreated isolate. Total phenolic and antioxidant activities of isolates improved in germinated and fermented isolates. Fermentation, germination, and ultrasonication are promising, green, safe, alternative biomodification techniques that may effectively improve protein functionality. These clean-labeled proteins can also be used as bioactive agents in the food industry.

Synthesis of hydroxyethyl starch 200/0.5-loaded albumin nanoparticles: biocompatibility and interaction mechanism.

We aimed to synthesize hydroxyethyl starch (HES) 200/0.5-loaded bovine serum albumin nanoparticles (HBNs) and investigate the compatibility and binding mechanism in simulated physiological environments. Here, to elucidate the morphology, biocompatibility, and formation mechanism of HBNs, techniques such as scanning electron microscopy, haemolysis test, fluorescence, and circular dichroism spectroscopy were applied. The thermodynamic parameters at body temperature (ΔS° = -26.7J·mol-1 ·K-1 , ΔH° = -3.20 × 104 J·mol-1 , and ΔG = -2.35 × 104 J·mol-1 ) showed a 1:1 binding stoichiometry, which was formed by hydrogen bonds and van der Waals interactions. In addition, the conformational analysis showed that the microenvironment of fluorophores was altered with the adaptational protein secondary structural changes. Energy transfer occurred from the fluorophores to HES with a high possibility. All these results provided accurate and complete primary data for demonstrating the interaction mechanisms of HES with BSA, which helps to understand its pharmaceutical effects in blood.

Insight into Organization of Gliadin and Glutenin Extracted from Gluten Modified by Phenolic Acids

The changes in the secondary structure of individual gluten protein fractions (gliadin and glutenin) caused by the supplementation of model dough with eight phenolic acids were analysed. Gliadins and glutenins were extracted from gluten samples obtained from overmixed dough. The changes in the gliadin secondary structure depended on the amount of phenolic acid added to the dough. Higher acid concentrations (0.1% and 0.2%) led to a significant reduction in the amount of α-helices and to the formation of aggregates, non-ordered secondary structures, and antiparallel β-sheets. After the addition of acids at a lower concentration (0.05%), the disaggregation of pseudo-β-sheet structures and the formation of β-turns, hydrogen-bonded β-turns, and antiparallel β-sheets were detected. In the case of glutenin, most of the phenolic acids induced the formation of intermolecular hydrogen bonds between the polypeptide chains, leading to glutenin aggregation. When phenolic acids were added at a concentration of 0.05%, the process of protein folding and regular secondary structure formation was also observed. In this system, antiparallel β-sheets and β-turns were created at the expense of pseudo-β-sheets.

Unraveling Extremely Damaging IRAK4 Variants and Their Potential Implications for IRAK4 Inhibitor Efficacy.

Interleukin-1-receptor-associated kinase 4 (IRAK4) possesses a crucial function in the toll-like receptor (TLR) signaling pathway, and the dysfunction of this molecule could lead to various infectious and immune-related diseases in addition to cancers. IRAK4 genetic variants have been linked to various types of diseases. Therefore, we conducted a comprehensive analysis to recognize the missense variants with the most damaging impacts on IRAK4 with the employment of diverse bioinformatics tools to study single-nucleotide polymorphisms' effects on function, stability, secondary structures, and 3D structure. The residues' location on the protein domain and their conservation status were investigated as well. Moreover, docking tools along with structural biology were engaged in analyzing the SNPs' effects on one of the developed IRAK4 inhibitors. By analyzing IRAK4 gene SNPs, the analysis distinguished ten variants as the most detrimental missense variants. All variants were situated in highly conserved positions on an important protein domain. L318S and L318F mutations were linked to changes in IRAK4 secondary structures. Eight SNPs were revealed to have a decreasing effect on the stability of IRAK4 via both I-Mutant 2.0 and Mu-Pro tools, while Mu-Pro tool identified a decreasing effect for the G198E SNP. In addition, detrimental effects on the 3D structure of IRAK4 were also discovered for the selected variants. Molecular modeling studies highlighted the detrimental impact of these identified SNP mutant residues on the druggability of the IRAK4 ATP-binding site towards the known target inhibitor, HG-12-6, as compared to the native protein. The loss of important ligand residue-wise contacts, altered protein global flexibility, increased steric clashes, and even electronic penalties at the ligand-binding site interfaces were all suggested to be associated with SNP models for hampering the HG-12-6 affinity towards IRAK4 target protein. This given model lays the foundation for the better prediction of various disorders relevant to IRAK4 malfunction and sheds light on the impact of deleterious IRAK4 variants on IRAK4 inhibitor efficacy.

Molecular mechanisms of nano-sized polystyrene plastics induced cytotoxicity and immunotoxicity in Eisenia fetida

Nanoplastics (NPs) are currently everywhere and environmental pollution by NPs is a pressing global problem. Nevertheless, until now, few studies have concentrated on the mechanisms and pathways of cytotoxic effects and immune dysfunction of NPs on soil organisms employing a multidimensional strategy. Hence, earthworm immune cells and immunity protein lysozyme (LZM) were selected as specific receptors to uncover the underlying mechanisms of cytotoxicity, genotoxicity, and immunotoxicity resulting from exposure to polystyrene nanoplastics (PS-NPs), and the binding mechanisms of PS-NPs-LZM interaction. Results on cells indicated that when earthworm immune cells were exposed to high-dose PS-NPs, it caused a notable rise in the release of reactive oxygen species (ROS), resulting in oxidative stress. PS-NPs exposure significantly decreased the cell viability of earthworm immune cells, inducing cytotoxicity through ROS-mediated oxidative stress pathway, and oxidative injury effects, including reduced antioxidant defenses, lipid peroxidation, DNA damage, and protein oxidation. Moreover, PS-NPs stress inhibited the intracellular LZM activity in immune cells, resulting in impaired immune function and immunotoxicity by activating the oxidative stress pathway mediated by ROS. The results from molecular studies revealed that PS-NPs binding destroyed the LZM structure and conformation, including secondary structure changes, protein skeleton unfolding/loosening, fluorescence sensitization, microenvironment changes, and particle size changes. Molecular docking suggested that PS-NPs combined with active center of LZM easier and inhibited the protein function more, and formed a hydrophobic interaction with TRP 62, a crucial amino acid residue closely associated with the function and conformation of LZM. This is also responsible for LZM conformational changes and functional inhibition /inactivation. These results of this research offer a fresh outlook on evaluating the detriment of NPs to the immune function of soil organisms using cellular and molecular strategies.

Sulfonamides stimulate ROS formation upon glycation of human carbonic anhydrase II

Advanced glycation end products are the most important species of glycation pathway, and cause disorders such as oxidative stress and diabetes. Sulfonamide compounds, which are generally known as widespread inhibitors, are potential agents used in different drug products, which can readily enter biological matrices. In the present work, the structure and activity of human carbonic anhydrase II studied in the presence of glucose as well as four sulfonamide agents from different views. These included enzyme kinetics, free lysine content, fluorescence spectroscopy, circular dichroism, and ROS measurement. Our results indicated that upon glycation, the structure of HCA II collapses and 8 to 13 lysine residues will be more available based on ligand incubation. Secondary and tertiary structural changes were also observed in the presence and absence of sulfonamide agents using fluorescence and circular dichroism methods, respectively. These spectroscopic data also showed a remarkable increase in hydrophobicity and decrease in α-helix contents during glycation, especially after 35 days of incubation. ROS assay was studied in the presence of glucose and sulfonamide compounds, that demonstrated the role of sulfonamide compounds in ROS formation in the presence of glucose in a synergistic manner. Overall, our data indicated that sulfonamides act as a stimulant factor upon prolonged interaction with HCA II and may intensify the complications of some disorders, such as diabetes and other conformational diseases.

The effect of papain hydrolysis on tropomyosin levels in shrimp

Shrimp allergy is a serious public health problem. Epidemiological studies indicated the main cause of food allergy is the ingestion of shrimp and crab. Consequently, reducing the risk of shrimp and crab allergy is a major research focus. Few studies have demonstrated the effect of enzyme hydrolysis on reduction of shrimp allergens in food. In this study, we used papain, a commonly used enzyme in the food industry, as an ingredient to decrease levels of allergen tropomyosin in shrimp. 0–50U of papain was used to treat the shrimp meat, and then heated to measure the levels of tropomyosin, and determined the change of the protein secondary structure. The results showed that 20U of papain decrease the tropomyosin levels up to 80 %, which was further enhanced when combined with 3 min of heating. Furthermore, the result of Fourier-transform infrared spectroscopy (FTIR) showed alteration of secondary protein structure after the processing. The processing developed in this study may be an effective method used to change the levels and structure of tropomyosin.

Hexametaphosphate, a Common Food Additive, Aggregated the Hen Egg White Lysozyme.

Polyphosphate polymers are chains of phosphate monomers chemically bonded together via phosphoanhydride bonds. They are found in all prokaryotic and eukaryotic organisms and are among the earliest, most anionic, and most mysterious molecules known. They are everywhere, from small cellular components to additives in our food. There is a strong association between hyperphosphatemia and mortality. That is why it is crucial to assess how polyphosphates, as food additives, affect the quality of edible proteins. This study investigated the effect of inexpensive and widely used food additives (hexametaphosphate labeled as E452) on bakery items, meat products, fish, and soft drinks. Using various spectroscopic and microscopic techniques, we examined how hexametaphosphate affected the aggregation propensity, structure, and stability of a commonly used food protein: hen egg white lysozyme (HEWL). The solubility of HEWL is affected in a bimodal fashion by the concentration of hexametaphosphate. The bimodal concentration-dependent effect was also observed in the tertiary and secondary structural changes. Hexametaphosphate-induced HEWL aggregates were amorphous, as evidenced by ThT fluorescence, far-UV CD, and TEM imaging. This study showed that the food additive (hexametaphosphate) may denature and aggregate proteins and may lead to undesirable health issues.

Application and evaluation of short-wave infrared radiation for peanut oil production

Abstract Short-wave infrared radiation (SIR) was used to improve the quality of peanut oil (PO) and peanut meal protein (PMI) in this study. The results showed that SIR roasting was beneficial to increase the yield and improve the quality and flavor of PO. The oxidative stability index (OSI) was improved, the contents of tocopherols and polyphenols increased and the contents of benzo (a) pyrene and polar substances decreased. Besides, the characteristic flavor substances were detected but not for the burnt smell. The effects of SIR on the structural and functional properties of PMI were investigated. It was found that SIR roasting could induce partial denaturation of PMI, thus improving its functional properties such as solubility, emulsifying and foaming, but did not involve the change of secondary structure. It was confirmed that SIR is a potential and available pre-roasting method to improve the comprehensive utilization of peanut resources.

Endotoxin accelerates insulin amyloid formation and inactivates insulin signal transduction

Aims and objectivesThe aim of this study is to discuss the influence of endotoxin on insulin amyloid formation, to provide guidance for therapeutic insulin preparation and storage. Materials and methodsThe ThT and ANS binding assays were applied to characterize the dynamics curve of insulin amyloid formation with the presence or absence of endotoxin. The morphological structures of intermediate and mature insulin fibrils were observed with SEM and TEM. Secondary structural changes of insulin during fibriliation were examined with CD, FTIR and Raman spectral analysis. The cytotoxic effects of oligomeric and amyloidogenic insulin aggregates were detected using a cck-8 cell viability assay kit. The influence of endotoxin on insulin efficacy was analyzed by monitoring the activation of insulin signal transduction. Key findingsThT analysis showed that endotoxin, regardless of species, accelerated insulin fibrils formation in a dose-dependent manner, as observed with a shorter lag phase. ANS binding assay demonstrated endotoxin provoked the exposure of insulin hydrophobic patches. The results of SEM and TEM data displayed that endotoxin drove insulin to cluster into dense and viscous form, with thicker and stronger filaments. Based on CD, FTIR and Raman spectra, endotoxin promoted the transition of α-helix to random coil and β-strand secondary structures during insulin aggregation. Insulins in both oligomeric and amyloidogenic forms were cytotoxic to HepG2 cells, with the former being more severe. Finally, the efficacy of endotoxin treated insulin obviously decreased. SignificanceOur studies revealed that endotoxin disrupts the structural integrity of insulin and promotes its amyloidosis. These findings offered theoretical guidance for insulin storage and safe utilization, as well as pointing up a new direction for insulin resistance research.

Steady-state and 3D fluorescence study reveals the binding of a dicoumarol analogue in subdomain IIA of human serum albumin with structural variation

Drugs exhibit pharmacological properties through their binding interactions with the target receptors. Coumarins and dicoumarols are known to exhibit diverse pharmacological potential. 3,3′-Carbonylbis (7-diethylamino coumarin) (CDC) is a bis-coumarin derivative with antioxidant activity. The interaction of CDC to human serum albumin (HSA) has been reported here. The fluorescence quenching of HSA by CDC at 303, 308, and 313 K revealed a dynamic quenching with a quenching constant of 104 M−1 order. The binding constant from spectroscopic methods was found to be 103 M−1 order. Thermodynamic parameters (∆S0, ∆H0, and ∆G0) were calculated from temperature studies using the Van't Hoff equation. A negative ∆G0 value showed the spontaneity of the interaction. A positive ∆S0 value and negative ∆H0 value indicated the major role of an electrostatic force. Further the binding was found to be an entropy-driven process. Site-specific marker displacement studies with 1-Anilino-8-naphthalene sulfonate (ANS), warfarin, and ibuprofen revealed CDC binding at site-1 in subdomain IIA. HSA conformational changes were verified using synchronous and 3D fluorescence studies. Secondary structural changes in HSA were visible from circular dichroism results. Molecular docking results corroborated the experimental finding showing CDC binding at site-1 in HSA.

Unveiling the Modification of Esterase-like Activity of Serum Albumin by Nanoplastics and Their Cocontaminants.

Nanoplastics and other cocontaminants have raised concerns due to their widespread presence in the environment and their potential to enter the food chain. The harmful effects of these particles depend on various factors, such as nanoparticle size, shape, surface charge, and the nature of the cocontaminants involved. On entering the human body, human serum albumin (HSA) molecules bind and transport these particles in the blood system. The esterase-like activity of HSA, which plays a role in metabolizing drug/toxic compounds, was taken as a representative to portray the effects of these particles on HSA. Polystyrene nanoplastics (PSNPs) with different surface functionalization (plain (PS), amine (PS-NH2), and carboxy (PS-COOH)), different sizes (100 and 500 nm), and PS with cocontaminant metformin hydrochloride (Met-HCl), a widely used antidiabetic drug, were investigated in this study. Fluorescence emission spectra of HSA revealed that PS-NH2 exhibits a greater effect on protein conformation, smaller NPs have a greater influence on protein structure than larger NPs, and Met-HCl lowers PSNPs' affinity for HSA by coating the surface of the NPs, which may result in direct NP distribution to the drug's target organs and toxicity. Circular dichroism spectra also supported these results in terms of secondary structural changes. Esterase activity of HSA was inhibited by all the particles (except Met-HCl) by competitive inhibition as concluded from constant Vmax and increasing Km. Greater reduction in enzyme activity was observed for PS-NH2 among functionalizations and for 100 nm PS among sizes. Furthermore, Met-HCl lowers the inhibitory impact of PSNPs on HSA since the drug binds weakly to HSA, and so they can serve as a vector delivering PSNPs to their target organs, resulting in serious implications.

Impact of pH and NaCl on the molecular conformation of myosin and myosin microgel and underlying mechanism: A comprehensive study using spectroscopy and molecular dynamics simulation

The conformation of myosin in its natural and denatured state can be changed by adjusting the pH and NaCl concentration. Raman spectroscopy, endogenous fluorescence, scanning electron microscopy, and molecular dynamics (MD) were used to observe the molecular conformational changes of tilapia myosin and myosin microgel (MM). When the NaCl concentration was 0.6 mol/L and the pH was 7.0, myosin and MM were in a fibrillated state, contained a high α-helix content, exhibited the highest intensity of endogenous fluorescence, and showed a loose conformation (Rgmyosin: 3.32 ± 0.06 nm, RgMM: 3.11 ± 0. 01 nm), and high solvent-accessibility surface area (SASA) (SASAmyosin: 406 ± 4 nm2; SASAMM: 378 ± 3 nm2) with high secondary structure stability. The pH and NaCl affected the SASA, hydrogen bonding number, and charge of myosin and MM, leading to secondary structure and conformational changes. Compared to NaCl, the pH exhibited a greater effect on the conformation of myosin and MM, and MM improved the stability of the protein. In conclusion, this study clarified the above mentioned conformational changes in proteins at the molecular level, which may facilitate the development of myosin in food processing.

Adsorption and Molecular Display of a Redox-Active Protein on Gold Nanoparticle Surfaces.

Engineered gold nanoparticles (AuNPs) have great potential in many applications due to their tunable optical properties, facile synthesis, and surface functionalization via thiol chemistry. When exposed to a biological environment, NPs are coated with a protein corona that can alter the NPs' biological identity but can also affect the proteins' structures and functions. Protein disulfide isomerase (PDI) is an abundant protein responsible for the disulfide formation and isomerization that contribute to overall cell redox homeostasis and signaling. Given that AuNPs are widely employed in nanomedicine and PDI plays a functional role in various diseases, the interactions between oxidized (oPDI) and reduced (rPDI) with 50 nm citrate-coated AuNPs (AuNPs) are examined in this study using various techniques. Upon incubation, PDI adsorbs to the AuNP surface, which leads to a reduction in its enzymatic activity despite limited changes in secondary structures. Partial enzymatic digestion followed by mass spectrometry analysis shows that orientation of PDI on the NP surface is dependent on both its oxidation state and the PDI:AuNP incubation ratios.

Tracking the binding site of anticancer drug fluxoridin with Fe-related proteins to achieve intelligent drug delivery

In cancer cells that need a lot of iron for growth and metastasis, halo-transferrin (TF-containing iron) enters the cell with the help of the transferrin receptor 1 (TFR1) protein. If the anticancer drug can bind to the iron site by interacting with apo-transferrin (iron-free FT), it can enter the cancer cell by the same mechanism. Two iron-related proteins, Bovine liver catalase (BLC) and apo-Transferrin (TF), that are important in cancer patients were selected and their interaction with the anti-cancer drug Floxuridine (FUDR) was investigated. Here, the protective role of FUDR was evaluated by several variables such as drug concentration, interaction time, and temperature-induced degradation of enzyme function. The results showed that the protective effect of the FUDR is greater in high concentrations (in 5 × 10-5 M:1.78 % and 2.59 % after 24 and 48 h). The interaction of the FUDR with both proteins can reduce the intensity of the fluorescence emission by a static mechanism. The binding strength of the FUDR with both proteins was almost similar and with the order of 104 M−1 (Kb = 3.90 ± 0.41 × 104 M−1 for BLC-FUDR and 5.01 ± 0.36 × 104 M−1 for TF-FUDR at 310 K). The thermodynamic calculations (in agreement with the docking results) indicated that FUDR-protein complex formation was exothermic and the main binding forces in the binding process were van der Waals interactions and hydrogen bonds. Both fluorophores tryptophan (Trp) and tyrosine (Tyr) of both proteins had significant roles in fluorescence quenching and the interaction process, the polarity of their microenvironment changed. CD results showed that the secondary structure changes of TF are slightly more than BLC. Molecular docking showed that the binding of the FUDR to TF is very close to the Fe-specific site and is placed in the cavity among the wrapping domain, N-Terminal arm, and β-barrel in BLC.

Changes in physicochemical and conformational properties of myofibrillar proteins isolated from mandarin fish (Siniperca chuatsi) treated by atmospheric pressure plasma jet

ABSTRACT The effects of atmospheric pressure plasma jet (APPJ) treatment on the physicochemical and conformational properties of myofibrillar protein (MP) isolated from mandarin fish. The findings revealed that after exposing MP to APPJ for 0–12 s, there was a significant (P < .05) decline in the solubility and total sulfhydryl concentration. Turbidity and surface hydrophobicity increased significantly, while pH value decreased significantly at first but then stabilized. Gel electrophoresis confirmed that the extracted protein was unaffected. FTIR spectroscopy indicated that the APPJ treatment caused slight changes in secondary structure. However, the UV absorption spectral and intrinsic tryptophan fluorescence demonstrated that the tertiary structure of MP was altered following APPJ treatment. According to the rheological characteristics, APPJ treatment could improve protein cross-linking, raise storage modulus, and promote the development of protein gel network structure. These findings demonstrated that APPJ treatment might improve the functional characteristics of MP isolated from mandarin fish.

Effect of ultrasonic frequency on the structural and functional properties of pea protein isolation.

Pea protein, as a by-product of peas (Pisum sativum L.), is rich in a variety of essential amino acids that can meet the body's protein needs and is a valuable source of protein. Since the function of pea protein is closely related to its structure, pea protein has been subjected to different modifications in recent years to improve its application in food and to develop new products. The effects of sonication frequency (primary and secondary time) on pea protein isolate's (PPI's) structural and functional properties were investigated. Sodium dodecyl sulfate polyacrylamide gel electrophoresis demonstrated that different sonication frequencies at the same power (600 W) treatment had no effect on PPI's molecular weight. Fourier-transform infrared spectroscopy revealed that treatment at different sonication frequencies caused secondary structural changes in PPI. The particle size distribution, foaming, stability, surface hydrophobicity, emulsification, and oxidation resistance of PPI were improved after primary and secondary sonication, but secondary sonication was not more effective than primary sonication for an extended period of time. Overall, ultrasound is able to improve the structural and functional properties of pea proteins within a suitable range. It provides a theoretical basis for elucidating the modification of the structure and function of plant proteins by ultrasound and lays the foundation for the development of plant proteins in food applications as well as development. © 2023 Society of Chemical Industry.

Changes in Dental Biofilm Proteins' Secondary Structure in Groups of People with Different Cariogenic Situations in the Oral Cavity and Using Medications by Means of Synchrotron FTIR-Microspectroscopy.

This work unveils the idea that the cariogenic status of the oral cavity (the presence of active caries lesions) can be predicted via a lineshape analysis of the infrared spectral signatures of the secondary structure of proteins in dental biofilms. These spectral signatures that work as natural markers also show strong sensitivity to the application in patients of a so-called modulator-a medicinal agent (a pelleted mineral complex with calcium glycerophosphate). For the first time, according to our knowledge, in terms of deconvolution of the complete spectral profile of the amide I and amide II bands, significant intra- and intergroup differences were determined in the secondary structure of proteins in the dental biofilm of patients with a healthy oral cavity and with a carious pathology. This allowed to conduct a mathematical assessment of the spectral shifts in proteins' secondary structure in connection with the cariogenic situation in the oral cavity and with an external modulation. It was shown that only for the component parallel β-strands in the amide profile of the biofilm, a statistically significant (p < 0.05) change in its percentage weight (composition) was registered in a cariogenic situation (presence of active caries lesions). Note that no significant differences were detected in a normal situation (control) and in the presence of a carious pathology before and after the application of the modulator. The change in the frequency and percentage weight of parallel β-strands in the spectra of dental biofilms proved to be the result of the presence of cariogenic mutans streptococci in the film as well as of the products of their metabolism-glucan polymers. We foresee that the results presented here can inherently provide the basis for the infrared spectral diagnosis of changes (shifts) in the oral microbiome driven by the development of the carious process in the oral cavity as well as for the choice of optimal therapeutic treatments of caries based on microbiome-directed prevention measures.