Secondary Structure Transformation Research Articles

Concentration effect of zinc ions on amyloid fibrillation of hen egg-white lysozyme with thermal treatment revealed by Raman spectroscopy

Accumulation of Zn2+ ions in protein aggregates has been suggested to be a key factor in Alzheimer’s disease etiology. However, the specific influence of Zn2+ ions on the formation of amyloid fibrils or amorphous aggregates is still much debated. Herein, we conducted a combined study of Raman spectroscopy, UV–vis absorption spectroscopy and ThT fluorescence assay on the concentration effects of Zn2+ ions on amyloid fibrillation of hen egg-white lysozyme with thermal treatment. The addition of Zn2+ ions showed a negligible effect on unfolding of the protein tertiary structures and nucleation pathways on amyloid fibrillation. In contrast, a distinct concentration-dependence was observed for the influence of Zn2+ ions on the transformation of lysozyme secondary structures. At low concentration, the metal ions do not affect the populations of major secondary structures in the final state after incubation, while they at high concentration exhibit a promotion effect on the transformation from α-helix to β-sheet-like structures. These findings provide insights into the multifaceted impact of Zn2+ ions on protein aggregation, shedding light on potential therapeutic strategies for neurodegenerative diseases.

Differential response of catalase to As (III) and As (V): Potential molecular mechanism under valence effect

Arsenic (As) is the most prolific contaminant in food, triggering arseniasis primarily via contaminated rice and drinking contaminated water. However, toxicological data for arsenite (As (III)) and arsenate (As (V)) on antioxidant enzyme catalase (CAT) at molecular level is shortage. The interaction mechanism of As (III) and As (V) with CAT was investigated using enzyme activity detection, multi–spectroscopic techniques, isothermal titration calorimetry and computational simulations. Results indicated As (III) and As (V) induced protein skeleton relaxation, secondary structure transformation, fluorescence sensitization and particle alteration of CAT, particularly As (III). Moreover, As (III)/As (V) bound to CAT through hydrogen bonding and hydrophobic. As (III) and As (V) contacted with core residues His 74, Asn 147 and His A74, Trp A357, respectively, thereby inhibiting CAT activity. Overall, As (III) is more aggressive against the structure and physiological function of CAT than As (V). Our findings enhance the understanding of health risk related to dietary As exposure.

Insight into the mechanism of high hydrostatic pressure effect on inhibitory efficiency of three natural inhibitors on polyphenol oxidase

The development of natural inhibitors of polyphenol oxidase (PPO) is crucial in the prevention of enzymatic browning in fresh foods. However, few studies have focused on the effect of subsequent sterilization on their inhibition efficiency. This study investigated the influence and mechanism of high hydrostatic pressure (HHP) on the inhibition of PPO by epigallocatechin gallate (EGCG), cyanidin-3-O-glucoside (C3G), and ferulic acid. Results showed that under the conditions of 550 MPa/30 min, the activity of EGCG-PPO decreased to 55.92%, C3G-PPO decreased to 81.80%, whereas the activity of FA-PPO remained stable. Spectroscopic experiments displayed that HHP intensified the secondary structure transformation and fluorescence quenching of PPO. Molecular dynamics simulations revealed that at 550 MPa, the surface interaction between PPO with EGCG or C3G increased, potentially leading to a reduction in their activity. In contrast, FA-PPO demonstrated conformational stability. This study can provide a reference for the future industrial application of natural inhibitors.

Transglutaminase-crosslinked cold-set pea protein isolate gels modified by pH shifting: Properties, structure and formation mechanisms

The poor gelation properties of pea protein isolate (PPI) limit their use in food industries. In the present study, PPI was modified by pH-shifting combined with heat treatment, followed by cold-set gelation of PPI gels induced by transglutaminase. Both pH 2–3 and pH 10–12 promoted the unfolding of PPI molecules and the transformation of secondary structures from ordered to disordered. In particular, PPI molecules with pH 12-shifting tended to expand and unfold, which resulted in the exposure of internal active groups and improvement in surface hydrophobicity. Accordingly, after the addition of 50 U/g transglutaminase, PPI gels with pH 12-shifting and heating treatment exhibited homogeneous and dense gel network with high cross-linking degree (88.12 ± 1.80%) and water holding capacity (92.13 ± 2.40%), since pH 12-shifting and heating treatment promoted the conversion of random coils and β-turns to β-folds and α-helices in PPI gels. However, with pH 10 and 11-shifting, the PPI molecules was partially unfolded and the PPI gels had a high non-network protein content, resulting in low-strength gel networks of PPI gels with rough and loose microstructures and a low WHC. These results showed that TGase-crosslinked cold-set PPI gels after pH 12-shifting and heat treatment could promote the formation of homogeneous and dense gel network structure, so that improved the PPI gelation properties, which had great potential to be used as gelling agents or nutraceutical delivery systems for thermal sensitive bioactive compounds in food and non-food fields.

The pH effects on thermal amyloid fibrillation kinetics of hen egg‐white lysozyme using new normalization factor for Raman spectroscopy

AbstractAmyloid fibrillation kinetics of proteins associated with neurodegenerative diseases has been extensively studied using Raman spectroscopy. The normalization factor for the spectra is crucial for obtaining correct kinetics of Raman indicators, especially vibrational band intensities. Here, we compared the concentration dependences between the absorption at 280 nm in UV–vis spectroscopy and the phenylalanine (Phe) Raman band intensity at 1003 cm−1 in amyloid fibrillation kinetics of lysozyme. The former exhibits better performance as normalization factor. Using this new normalization factor, the effect of pH value on the transformation of hen egg‐white lysozyme (HEWL) tertiary and secondary structures was studied subsequently. With increasing acidity, the unfolding of tertiary structures and the transformation of secondary structures are significantly accelerated. Notably, the populations of various secondary structures in the final state remain in the pH < 2.0 solutions, indicating that the branching ratios of “on‐pathway” to amyloid fibrils and “off‐pathway” to gel‐like aggregates are independent on the pH value in the range of 1.1–1.9.

Conformational analysis of lipid membrane mimetics modified with Aβ42 peptide by Raman spectroscopy and computer simulations

Peptide-lipid interactions play an important role in maintaining the integrity and function of the cell membrane. Even slight changes in these interactions can induce the development of various diseases. Specifically, peptide misfolding and aggregation in the membrane is considered to be one of the triggers of Alzheimer’s disease (AD), however its exact mechanism is still unclear. To this end, an increase of amyloid-beta (Aβ) peptide concentration in the human brain is widely accepted to gradually produce cytotoxic Aβ aggregates (plaques). These plaques initiate a sequence of pathogenic events ending up in observable symptoms of dementia. Understanding the mechanism of the Aβ interaction with cells is crucial for early detection and prevention of Alzheimer’s disease. Hence, in this work, a comprehensive Raman analysis of the Aβ42 conformational dynamics in water and in liposomes and lipodiscs that mimic the membrane system is presented. The obtained results show that the secondary structure of Aβ42 in liposomes is dominated by the α–helix conformation, which remains stable over time. However, it comes as a surprise to reveal that the lipodisc environment induces the transformation of the Aβ42 secondary structure to a β-turn/random coil. Our Raman spectroscopy findings are supported with molecular dynamics (MD) and density functional theory (DFT) simulations, showing their good agreement. Communicated by Ramaswamy H. Sarma

Deciphering the binding mechanism of gingerol molecules with plasma proteins: implications for drug delivery and therapeutic potential

Ginger is a highly valued herb, renowned globally for its rich content of phenolic compounds. It has been traditionally used to treat various health conditions such as cardiovascular diseases, digestive issues, migraines, Alzheimer’s disease, tumor reduction and chronic inflammation. Despite its potential medicinal applications, the therapeutic effectiveness of ginger is hindered by its limited availability and low plasma concentration levels. In this study, we explored the interaction of ginger’s primary phenolic compounds, specifically 6-gingerol (6 G), 8-gingerol (8 G) and 10-gingerol (10 G), with plasma proteins which are human serum albumin (HSA) and α-1-acid glycoprotein (AGP). These two plasma proteins significantly influence drug distribution and disposition as they are key binding sites for most drugs. Fluorescence emission spectra indicated strong binding of 6, 8 and 10 G with HSA, with binding constants of 2.03 ± 0.01 × 104 M−1, 4.20 ± 0.01 × 104 M−1 and 6.03 ± 0.01 × 106 M−1, respectively. However, the binding of gingerols with AGP was found to be negligible. Molecular displacement by site-specific probes and molecular docking analyses revealed that gingerols bind at the IIA domain, with stability provided by hydrogen bonds, van der Waals forces, conventional hydrogen bonds, carbon-hydrogen bonds, alkyl and Pi–alkyl interactions. Further, the partial unfolding of the protein was observed upon binding the gingerol compound with HSA. In addition, molecular dynamic simulations demonstrated that gingerols remained stable in the subdomain IIA over 100 ns. This stability, coupled with Molecular Mechanics Generalized Born Surface Area indicating free energies of −43.765, −57.504 and −66.69 kcal/mol for 6, 8 and 10 G, respectively, reinforces the robust binding potential of these compounds. Circular dichroism studies suggested that the interaction of gingerols leads to the minimal transformation of HSA secondary structure, with the pattern being 10 G > 8 G > 6 G, a finding further substantiated by root mean square deviation and root mean square fluctuation fluctuations. These results propose that HSA has a stronger affinity to gingerols than AGP, which could have significant implications on the therapeutic circulating levels of gingerols. Communicated by Ramaswamy H. Sarma

Effect of starch-based emulsion with different amylose content on the gel properties of Nemipterus virgatus surimi

The emulsion was prepared with peanut oil and corn starch with different amylose content using high-speed homogenization assisted high-pressure homogenization, and the effect of starch-based emulsion on the gel properties, whiteness, microstructure, protein secondary structure, chemical forces, texture and sensory properties of Nemipterus virgatus surimi was investigated. The results showed that high amylose corn starch was more beneficial to the stability of emulsion than normal and waxy starch. The gel strength, water holding capacity and texture properties of surimi were significantly improved by adding 10 % waxy corn starch-based emulsion or 15 % high amylose or normal corn starch-based emulsion. Moreover, the whiteness of surimi gel containing starch-based emulsion was higher, and the microstructure was more compact and delicate than that of surimi without emulsion. The addition of starch-based emulsion could increase the hydrophobic interaction and disulfide bond content, and promote the transformation of protein secondary structure to irregular direction. The sensory properties such as color, texture, taste and overall acceptability could be improved to varying degrees. Therefore, starch-based emulsion could be used to enhance the gel properties and nutritional value of surimi products.

HAMLET in human milk is resistant to digestion and carries essential free long chain polyunsaturated fatty acids and oleic acid.

The oleic acid/alpha-lactalbumin complex HAMLET (human alpha-lactalbumin made lethal to tumors) is cytotoxic to various cancerous cell lines and is assembled from alpha-lactalbumin (ALA) and free oleic acid (OA). HAMLET is also cytotoxic to normal immature intestinal cells. It remains unclear if HAMLET, experimentally assembled with OA and heat, can spontaneously assemble in frozen human milk over time. To approach this issue, we used a set of timed proteolytic experiments to evaluate the digestibility of HAMLET and native ALA. The purity of HAMLET in human milk was confirmed by ultra high performance liquid chromatography coupled to tandem mass spectrometry and western blot to resolve the ALA and OA components. Timed proteolytic experiments were used to identify HAMLET in whole milk samples. Structural characterization of HAMLET was performed by Fournier transformed infrared spectroscopy and indicated a transformation of secondary structure with increased alpha-helical character of ALA upon binding to OA.

Effect of sodium starch octenyl succinate-based Pickering emulsion on the physicochemical properties of hairtail myofibrillar protein gel subjected to multiple freeze-thaw cycles

A Pickering emulsion based on sodium starch octenyl succinate (SSOS) was prepared and its effects on the physicochemical properties of hairtail myofibrillar protein gels (MPGs) subjected to multiple freeze-thaw (F-T) cycles were investigated. The whiteness, water-holding capacity, storage modulus (G′) and texture properties of the MPGs were significantly improved by adding 1 %–2 % Pickering emulsion (P < 0.05). Meanwhile, Raman spectral analysis demonstrated that Pickering emulsion promoted the transformation of secondary structure, enhanced hydrogen bonds and hydrophobic interactions, and promoted the transition of disulfide bond conformation from g-g-g to g-g-t and t-g-t. At an emulsion concentration of 2 %, the α-helix content decreased by 10.37 %, while the β-sheet content increased by 7.94 %, compared to the control. After F-T cycles, the structure of the MPGs was destroyed, with an increase in hardness and a decrease in whiteness and water-holding capacity, however, the quality degradation of MPGs was reduced with 1 %–2 % Pickering emulsion. These findings demonstrated that SSOS-Pickering emulsions, as potential fat substitutes, can enhance the gel properties and the F-T stability of MPGs.

Study on the effect and mechanism of chicken breast on the gel properties of silver carp (Hypophthalmichtys molitrix) surimi.

Adding appropriate exogenous substances is an effective means to improve the quality of freshwater fish surimi. This study investigated the effects of chicken breast on the gel properties of mixed minced meat products. With the increase in the proportion of chicken breast, the breaking force of mixed gels gradually increased. When the addition ratio was 30/70, the gel strength of mixed gels had the highest strength of 759.00 g·cm and also the highest water holding capacity of 87.36%. Compared with surimi gels (0/100), the hardness, adhesiveness, and chewiness of mixed gels were significantly improved. The increase in the proportion of chicken breast increased the thermal stability of the mixed sol and improved the rheological properties of the mixed sol. When the proportion was 40/60, the area of immobile water (A22 ) in the mixed gel increased significantly, and the highest A22 was 3463.24. The hydrophobic interactions and disulfide bonds in the mixed gel were significantly increased due to the addition of chicken breast. The results of microstructure, electrophoresis, and Raman spectroscopy indicated that the addition of chicken breast promoted the cross-linking of the proteins in mixed gels, which facilitated the transformation of the protein secondary structure from α-helical to β-folded structure, thus forming a more uniform and orderly network structure. These results suggest that improving the gel properties of silver carp surimi by using chicken breast has practical implications for the development of new blended products for surimi processing. This article is protected by copyright. All rights reserved.

MXene: An efficient hemoperfusion sorbent for the removal of uremic toxins

MXene, a family of two-dimensional (2D) transition metal carbides and nitrides have attracted extensive interests for many biochemical applications, including tumour elimination, biosensors, and magnetic resonance imaging (MRI). In this article, we firstly discovered that Ti3C2Tx MXene exhibited a highly efficient adsorption capability as hemoperfusion absorbent towards middle-molecular mass and protein bound uremic toxins in the end stage of renal disease (ESRD) treatment. Molecular scale investigations reveal that the high efficiency of MXene for the removal of uremic toxins could be attributed to synergistic effects of physical/chemical adsorption, electrostatic interaction surface of 2D MXene, and transformation of protein secondary structure. 2D MXene materials could be used as a new hemoperfusion sorbent with ultrahigh efficiency for removing uremic toxins during the treatment of kidney disease.

Enzyme/pH dual stimuli-responsive nanoplatform co-deliver disulfiram and doxorubicin for effective treatment of breast cancer lung metastasis

ABSTRACT Objectives Metastasis is still one of the main obstacles in the treatment of breast cancer. This study aimed to develop disulfiram (DSF) and doxorubicin (DOX) co-loaded nanoparticles (DSF-DOX NPs) with enzyme/pH dual stimuli-responsive characteristics to inhibit breast cancer metastasis. Methods DSF-DOX NPs were prepared using the amphiphilic poly(ε-caprolactone)-b-poly(L-glutamic acid)-g-methoxy poly(ethylene glycol) (PCL-b-PGlu-g-mPEG) copolymer by a classical dialysis method. In vitro release tests, in vitro cytotoxicity assay, and anti-metastasis studies were conducted to evaluate pH/enzyme sensitivity and therapeutic effect of DSF-DOX NPs. Results The specific pH and enzyme stimuli-responsiveness of DSF-DO NPs can be attributed to the transformation of secondary structure and the degradation of amide bonds in the PGlu segment, respectively. This accelerated drug release significantly increased the cytotoxicity to 4T1 cells. Compared with the control group, the DSF-DOX NPs showed a strong inhibition of in vitro metastasis with a wound healing rate of 36.50% and a migration rate of 18.39%. Impressively, in vivo anti-metastasis results indicated that the metastasis of 4T1 cells was almost completely suppressed by DSF-DOX NPs. Conclusion DSF-DOX NPs with controllable tumor site delivery of DOX and DSF were a prospectively potential strategy for metastatic breast cancer treatment.

Broad-spectrum hybrid antimicrobial peptides derived from PMAP-23 with potential LPS binding ability

Antimicrobial peptides, as an integral part of the innate immune system, kill bacteria through a special mechanism of action, making them less susceptible to drug resistance. However, Lipopolysaccharide (LPS) as the permeation barrier on the bacterial membrane, inhibits the antibacterial activity of antimicrobial peptides and triggers the inflammatory response. GWKRKRFG is an LPS binding sequence with a β-boomerang motif that can be linked to antimicrobial peptides to enhance their LPS affinity and reduce the possibility of LPS-induced inflammatory responses. In this study, a series of hybrid peptides were designed by conjugating the reported LPS binding sequence to the C-/N-terminal sequences of the natural porcine antimicrobial peptide PMAP-23 to increase the LPS affinity of peptides. Among all the designed hybrid peptides, 4R-PP-G8 showed the best antibacterial activity, nonhemolytic activity, and excellent cell selectivity. The presence of LPS not only induced the secondary structure transformation of 4R-PP-G8 from a random structure to an α-helical structure but also reduced the antibacterial activity of 4R-PP-G8 in a dose-dependent manner, indicating the excellent binding ability of 4R-PP-G8 to LPS. The LPS/LTA binding assay further verified the interaction between the peptide and LPS. The membrane permeability test verified that 4R-PP-G8 possessed a strong capability to penetrate the bacterial membrane after interacting with LPS. More direct membrane disruption was observed under FE-SEM and TEM. In conclusion, we provided a simple and efficient method to improve the LPS binding ability of antimicrobial peptides and enhance their antimicrobial activity, resulting in the peptide 4R-PP-G8 with clinical application potential.

Inhibition of the Fibrillation of Amyloid Aβ1-40 by Hybrid-Lipid-Polymer Vesicles.

The transformation of functional proteins into amyloidic plaques is responsible for the impairment of neurological functions in patients fallen victim to debilitating neurological conditions like Alzheimer's, Parkinson's, and Huntington's diseases. The nucleating role of amyloid beta (Aβ1-40 ) peptide into amyloids is well established. Herein, lipid hybrid-vesicles are generated with glycerol/cholesterol-bearing polymers aiming to alter the nucleation process and modulate the early phases of Aβ1-40 fibrillation. Hybrid-vesicles (±100nm) are prepared by incorporating variable amounts of cholesterol-/glycerol-conjugated poly(di(ethylene glycol)m acrylates)n polymers into 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) membranes. The in vitro fibrillation kinetics coupled to transmission electron microscopy (TEM) is employed to investigate the role of hybrid-vesicles on Aβ1-40 fibrillation without destroying the vesicular membrane. Both polymers, when embedded in hybrid-vesicles (up to 20%) significantly prolonged the fibrillation lag phase (tlag ) compared to a small acceleration in the presence of DOPC vesicles, irrespective of the amount of polymers inside the hybrid-vesicles. Along with this notable retardation effect, a morphological transformation of the amyloid's secondary structures to amorphous aggregates or the absence of fibrillar structures when interacting with the hybrid-vesicles is confirmed by TEM and circular dichroism (CD) spectroscopy.

Partial substitution of whey protein concentrate by zein in high-protein nutrition bars: An effective method to reduce hardening during storage.

Whey protein concentrate-based high-protein nutrition bars (WPC-based HPN bars) are prone to hardening during storage, which limits their shelf life. In this study, zein was introduced to partially substitute WPC in the WPC-based HPN bars. The result of storage experiment revealed that the hardening of WPC-based HPN bars was significantly reduced with increasing zein content from 0% to 20% (mass ratio, zein:WPC-based HPN bar). Subsequently, the possible anti-hardening mechanism of zein substitution was studied in detail by determining the change in microstructure, patterns, free sulfhydryl group, color, free amino group, and Fourier transform infrared spectra of WPC-based HPN bars during storage. The results showed that zein substitution significantly blocked protein aggregation by inhibiting cross-linking, the Maillard reaction, and protein secondary structure transformation from α-helix to β-sheet, which reduced the hardening of WPC-based HPN bars. This work provides insight into the potential utilization of zein substitution to improve the quality and shelf life of WPC-based HPN bars. PRACTICAL APPLICATION: In the preparation of whey protein concentrate-based high-protein nutrition bars, the introduction of zein to partially replace WPC can effectively reduce the hardening of WPC-based HPN bars during storage by preventing protein aggregation between WPC macromolecules. Therefore, zein could act as an agent to reduce the hardening of WPC-based HPN bars.

Concentration-dependent effect of Nickel ions on amyloid fibril formation kinetics of hen egg white lysozyme: A Raman spectroscopy study

Nickel, an important transition metal element, is one of the trace elements for human body and has a crucial impact on life and health. Some evidences show the excess exposure to metal ions might be associated with neurological diseases. Herein, we applied Raman spectroscopy to study the Ni(II) ion effect on kinetics of amyloid fibrillation of hen egg white lysozyme (HEWL) in thermal and acidic conditions. Using the well-known Raman indicators for protein tertiary and secondary structures, we monitored and analyzed the concentration effect of Ni(II) ions on the unfolding of tertiary structures and the transformation of secondary structures. The experimental evidence validates the accelerator role of the metal ion in the kinetics. Notably, the additional analysis of the amide I band profile, combined with thioflavin-T fluorescence assays, clearly indicates the inhibitory effect of Ni(II) ions on the formation of amyloid fibrils with organized β-sheets structures. Instead, a more significant promotion influence is affirmed on the assembly into other aggregates with disordered structures. The present results provide rich information about the specific metal-mediated protein fibrillation.

Structure relationship of non-covalent interactions between lotus seedpod oligomeric procyanidins and glycated casein hydrolysate during digestion.

Procyanidin-amino acid interactions during transmembrane transport cause changes in the structural and physical properties of peptides, which limits further absorption of oligopeptide-advanced glycation end products (AGEs). In this study, glycated casein hydrolysates (GCSHs) were employed to investigate the structure and interaction mechanism of GCSH with lotus seedpod oligomeric procyanidin (LSOPC) complexes in an intestinal environment. LSOPC can interact with GCSH under certain conditions to form hydrogen bonds and hydrophobic interactions to form GCSH-LSOPC complexes. Results showed that procyanidin further leads to the transformation of a GCSH secondary structure and the increase of surface hydrophobicity (H0). The strongest non-covalent interaction between GCSH and (-)-epigallocatechin gallate (EGCG) was due to the polyhydroxy structure of EGCG. Binding site analysis showed that EGCG binds to the internal cavity of P1 to maintain the relative stability of the binding conformation. The antioxidant capacity of GCSH was remarkably elevated by GCSH-LSOPC. This study will provide a new reference for the accurate control of oligopeptide-AGEs absorption by LSOPC in vivo.

The role of feruloylation of wheat bran arabinoxylan in regulating the heat-evoked polymerization behavior of gluten

To further reveal the role of feruloylation of arabinoxylan (AX) in regulating the heat-evoked polymerization behavior of gluten, AX was extracted from wheat bran and in situ modified with lime to obtain AX with controlled ferulic acid (FA) content. The effects of AX with varied FA level on the heat-evoked polymerization of gluten were comparatively studied. The results suggested that AX postponed the disulfide bond mediated polymerization behavior of glutenins and enhanced polymerization degree of glutenin-glutenin and glutenin-gliadin crosslinks upon thermal treatment, while FA moiety suppressed the facilitated polymerization behavior compared with AX free of FA. iTARQ analysis demonstrated that FA moiety of AX mainly suppressed the polymerization of low molecular weight glutenin subunits and α/γ-gliadins in glutenin-gliadin crosslinks. The complete polymerization of glutenin and gliadin elevated the intermolecular β-sheet and ordered α-helix structures at the expense of other structures, while AX stabilized the transformation of secondary structures and was irrelevant with FA level. FA moiety of AX contributed to stabilizing the microenvironment of tryptophan, and evoked the disulfide bond conformation with reduced gauche-gauche-gauche conformation upon formation of glutenin-gliadin crosslinks. AX with the highest FA level exhibited the optimum elevation effect on the viscoelasticity of gluten, which might be attributed to the moderate polymerization of glutenin-gliadin and potential covalent linkage formed between the FA moiety of AX and gluten. This study could contribute to depicting the interacting mechanism of AX and gluten proteins, and further provide basis for exploiting nutritious high-fiber wheat-based products with superior organoleptic quality. • Arabinoxylan (AX) was in situ modified to control the ferulic acid (FA) content. • FA of AX contributed to suppressing the heat-evoked polymerization of gluten proteins. • Suppressed polymerized subunits of gluten upon heating by FA were identified. • FA moiety of AX contributed to stabilizing the microenvironment of tryptophan. • AX with high FA level exhibit optimum elevation effect on viscoelasticity of gluten.

Interactions of heat-induced myosin with hsian-tsao polysaccharide to affect the fishy odor adsorption capacity

The interaction mechanism of hsian-tsao polysaccharide (HTP) with unique gel-promoting and biological activity for improving the gel properties of surimi was not clarified. This study investigated the effects of HTP on heat-induced structural changes and the adsorption capacity of myosin to fishy odor compounds (hexanal, heptanal, nonanal, and 1-octen-3-ol). HTP concentration and heating ways greatly affected the physicochemical properties of myosin. Adding hydrophilic HTP covering the myosin surface aided in unfolding the structure of myosin and further disturbed the myosin aggregation with surface hydrophobicity decreased and total sulfhydryl contents increased. The main physical forces arising from hydrogen bonding and electrostatic interactions contributed to forming HTP-myosin complexes under setting (40 °C, 30 min), whereas cross-links occurred by enhanced hydrophobic interactions forming insoluble HTP-myosin complexes under two-step heating (40 °C, 30 min; 90 °C, 20 min), indicative of decreased solubility and increased turbidity, as evidenced by zeta potential, FTIR, fluorescence and UV–vis spectra, and fluorescence microstructure. This resulted in the transformation of secondary structure of myosin from α-helix to β-sheet with the increase of HTP. Furthermore, HTP interacting with myosin reduced the fishy odor binding capacity of myosin thus promoting the release during processing, as demonstrated by HS-SPME-GC. The findings provided new insight into the mechanism of regulating the fishy odor binding ability of myosin by application of HTP.