Kinetic Mechanism of Thioflavin T Binding onto the Amyloid Fibril of Hen Egg White Lysozyme

Binding Interaction of Coumarin Derivative Daphnetin with Ovalbumin: Molecular Insights into the Complexation Process and Effects of Metal Ions and pH in the Binding and Antifibrillation Studies

This study investigates the interaction between daphnetin and ovalbumin (OVA) as well as its potential to inhibit OVA fibrillation using both spectroscopic and computational analysis. A moderate binding affinity of 1 × 104 M-1 was observed between OVA and daphnetin, with a static quenched mechanism identified during the fluorescence quenching processes. Metal ions' (Cu2+ and Zn2+) presence led to an increase in the binding affinities of daphnetin toward OVA, mirroring a similar trend observed with the pH variation. Synchronous and 3D fluorescence studies indicated an increase in the polarity of the microenvironment surrounding the Trp residues during binding. Interestingly, circular dichroism and Fourier transform infrared studies showed a significant change in the secondary structure of OVA upon binding with daphnetin. The efficacy of daphnetin in inhibiting protein fibrillation was confirmed through thioflavin T and Congo Red binding assays along with fluorescence microscopic imaging analysis. The thermodynamic assessment showed positive ΔH° [+(29.34 ± 1.526) kJ mol-1] and ΔS° [+(181.726 ± 5.465) J mol-1] values, indicating the presence of the hydrophobic forces, while negative ΔG° signifies spontaneous binding interactions. These experimental findings were further correlated with computational analysis, revealing daphnetin dynamics within the binding site of OVA.

Rapid aggregation of amyloid-like protein enhanced by mTGase to prepare functional wool fabrics for efficient and sustainable remove heavy metals from wastewater

To counteract the increasing severity of water pollution and purify water sources, wastewater treatment materials are essential. In particular, it is necessary to improve the bonding strength between the adsorption material and the substrate in a long-term humid environment, and resist the invasion of microorganisms to prolong the service life. In this study, an amyloid-like aggregation method of lysozyme catalyzed by microbial transglutaminase (mTGase). Lysozyme self-assembles into an amyloid-like phase-transited lysozyme (PTL) in the presence of a reducing agent. Simultaneously, mTGase catalyzes acyl transfer reactions within lysozyme molecules or between lysozyme and keratin molecules, and driving PTL assembly on the wool fiber (TG-PTL@wool). This process enhances the grafting amount and fastness of PTL on the wool. Moreover, the tensile strength of wool fabric increased to 523 N. TG-PTL@wool achieves a 97.32 % removal rate of heavy metals, maintaining a removal rate of over 95 % after 5 cycles. TG-PTL@wool has excellent antibacterial property (99 %), and it remains above 90 % after 50 times of circulating washing. This study proved that mTGase can enhance the amyloid aggregation of lysozyme and enhance the bonding strength between PTL coating and substrate. Moreover, TG-PTL@wool provides a sustainable, efficient and cleaner solution for removing heavy metals from water.

Protonation-State Dependent Modulation of Hen Egg-White Lysozyme Fibrillation under the Influence of a Short Synthetic Peptide

Under the influence of various conditions, misfolding of soluble proteins occurs, leading to the formation of toxic insoluble amyloids. The formation and deposition of such amyloids within the body are associated with detrimental biological consequences such as the onset of several amyloid-related diseases. Previously, we established a strategy for the rational design of peptide inhibitors against amyloid formation based on the amyloidogenic-prone region of the protein. In the current study, we have designed and identified an Asp-containing rationally designed hexapeptide (SqP4) as an excellent inhibitor of hen egg-white lysozyme (HEWL) amyloid progression in vitro. First, SqP4 showed strong affinity toward the native monomeric HEWL leading to the stabilization of the native form and restriction in the unfolding process of monomeric HEWL. Second, SqP4 was found to arrest the amyloidogenic misfolded structure of HEWL in a nonfibrillar monomer-like stage. We also observed the differential effect of the protonation state of the charged amino acid (Asp) within the peptide inhibitor on the amyloid formation of HEWL and explored the reason behind the observations. The findings of this study can be implemented in future strategies for the development of potent therapeutics against other amyloid-related diseases.

Thioflavin T─a Reporter of Microviscosity in Protein Aggregation Process: The Study Case of α-Synuclein

Thioflavin T (ThT) informed microviscosity changes can be used to monitor protein aggregation. Steady-state, time-resolved and lasing spectroscopy were used to detect transient states in α-synuclein - a protein associated with Parkinson's disease. The major focus was on the nucleation phase, where conventional ThT fluorescence assay lacks appropriate sensitivity to detect early stage oligomers. Instead, lasing spectroscopy and lasing threshold parameters, in particular, were sensitive to detecting protein oligomers. Through lasing spectroscopy, a change in microviscosity correlating with the stages of protein aggregation was observed at two wavelengths 405 and 440 nm. The two wavelengths are associated with free dye molecules and β-sheet bound ThT molecules. This provides a perspective on elucidating the early formed protein aggregation, a critical aspect in understanding the pathogenesis of neurodegenerative diseases. The insights from the presented study shows the potential of using lasing spectroscopy as a sensitive tool in studying protein aggregation dynamics.

Deciphering amyloid fibril molecular maturation through FLIM-phasor analysis of thioflavin T

The investigation of amyloid fibril formation is paramount for advancing our understanding of neurodegenerative diseases and for exploring potential correlated therapeutic strategies. Moreover, the self-assembling properties of amyloid fibrils show promise for the development of advanced protein-based biomaterials. Among the methods employed to monitor protein aggregation processes, fluorescence has emerged as a powerful tool. Its exceptional sensitivity enables the detection of early-stage aggregation events that are otherwise challenging to observe. This research underscores the pivotal role of fluorescence analysis, particularly in investigating the aggregation processes of hen egg white lysozyme, a model protein extensively studied for insights into amyloid fibril formation. By combining classical spectroscopies with fluorescence microscopy and by exploiting the fluorescence properties (intensity and lifetime) of the thioflavin T, we were able to noninvasively monitor key and complex molecular aspects of the process. Intriguingly, the fluorescence lifetime imaging-phasor analysis of thioflavin T fluorescence lifetime on structures at different stages of aggregation allowed to decipher the complex fluorescence decay behavior, highlighting that their changes rise from the combination of specific binding to amyloid typical cross-β structures and of the rigidity of the molecular environment.

Frequency dependence of ultrasonic effects on the kinetics of hen egg white lysozyme fibrillation

Our study aimed to investigate the effects of ultrasound on the fibrillation kinetics of HEWL (hen egg white lysozyme) and its physicochemical properties. Ultrasound, a mechanical wave, can induce conformational changes in proteins. To achieve this, we developed an ultrasound exposure system and used various biophysical techniques, including ThT fluorescence spectroscopy, ATR-FTIR, Far-UV CD spectrophotometry, Fluorescence microscopy, UV-spectroscopy, and seeding experiments. Our results revealed that higher frequencies significantly accelerated the fibrillation of lysozyme by unfolding the native protein and promoting the fibrillation process, thereby reducing the lag time. We observed a change in the secondary structure of the sonicated protein change to the β-structure, but there was no difference in the Tm of native and sonicated proteins. Furthermore, we found that higher ultrasound frequencies had a greater seeding effect. We propose that the effect of frequency can be explained by the impact of the Reynolds number, and for the Megahertz frequency range, we are almost at the transition regime of turbulence. Our results suggest that laminar flows may not induce any significant change in the fibrillation kinetics, while turbulent flows may affect the process.

Formation of hen egg white lysozyme derived amyloid-based hydrogels using different gelation agents: A potential tool for drug delivery

Amyloids are highly stable protein fibrillar aggregates that get deposited in various parts of our body and cause detrimental diseases. But in nature, the presence of functional amyloids is also noted in bacteria that help them by forming hyphae, biofilm, protein reservoirs, signalling messengers, etc. Keeping this perspective in mind, the idea behind this research was to develop functional amyloids in the form of hydrogel and analyse its potential in the biomedical sector as a drug-delivery tool. The synthesis and characterisation of three types of amyloid-based hydrogels have been reported in this work. Hen Egg-White Lysozyme (HEWL) protein was chosen as the principal ingredient as it is extensively used as a standard protein for studying amyloidogenesis and has inherent antibacterial properties. Comparative studies of different hydrogel properties exhibited variations in the hydrogels based on compositional differences in them. Finally, a drug release assay was done on the synthesized hydrogels to explore their potential as drug delivery tools.

Nuclei-induced formation of amyloid fibrils in whey protein: Effects of enzyme hydrolysis on the ability of nuclei to induce fibril formation

Homogeneous and secondary nuclei (HN and SN) are aggregates formed at different stages of whey protein isolate (WPI) self-assembly. More fibrils can form when HN/SN are added as nuclei than when WPI self-assembles. We evaluated the effect of hydrolysis treatment on fibril-induction ability of nuclei derived from WPI, and investigated the relationship between induction ability and nuclear structure. Hydrolyzed SN-induced 9.47% more WPI fibrils than unhydrolyzed SN-induced. Infrared spectroscopy, X-ray diffraction analysis, and atomic force microscopy were used to examine the structural changes in hydrolyzed nuclei and the fibrils induced using these nuclei. We concluded that hydrolysis treatment led to a looser inter-β-sheet packaging in nuclei by increasing the inter-β-sheet distance. The inter-β-sheet distance of cross-β structure was a key determinant of fibril-induction ability of nuclei, which could be enhanced when inter-β-sheet structure was moderately loose. This research may provide a theoretical basis for the mechanism of nuclei-induced WPI fibrillation.

Manganese Ion-Induced Amyloid Fibrillation Kinetics of Hen Egg White-Lysozyme in Thermal and Acidic Conditions

As manganese ions (Mn²⁺) are identified as an environmental risk factor for neurodegenerative diseases, uncovering their action mechanism on protein amyloid fibril formation is crucial for related disease treatments. Herein, we performed a combined study of Raman spectroscopy, atomic force microscopy (AFM), thioflavin T (ThT) fluorescence, and UV-vis absorption spectroscopy assays, in which the distinctive effect of Mn²⁺ on the amyloid fibrillation kinetics of hen egg white-lysozyme (HEWL) was clarified at the molecular level. With thermal and acid treatments, the unfolding of protein tertiary structures is efficiently accelerated by Mn²⁺ to form oligomers, as indicated by two Raman markers for the Trp residues on protein side chains: the FWHM at 759 cm^-1 and the I₁₃₄₀/I₁₃₆₀ ratio. Meanwhile, the inconsistent evolutionary kinetics of the two indicators, as well as AFM images and UV-vis absorption spectroscopy assays, validate the tendency of Mn²⁺ toward the formation of amorphous aggregates instead of amyloid fibrils. Moreover, Mn²⁺ plays an accelerator role in the secondary structure transition from α-helix to organized β-sheet structures, as indicated by the N-C_α-C intensity at 933 cm^-1 and the amide I position of Raman spectroscopy and ThT fluorescence assays. Notably, the more significant promotion effect of Mn²⁺ on the formation of amorphous aggregates provides credible clues to understand the fact that excess exposure to manganese is associated with neurological diseases^.

Mechanistic Insight into the Amyloid Fibrillation Inhibition of Hen Egg White Lysozyme by Three Different Bile Acids

Amyloid aggregation of protein is linked to many neurodegenerative diseases. Identification of small molecules capable of targeting amyloidogenic proteins has gained significant importance. Introduction of hydrophobic and hydrogen bonding interactions through site-specific binding of small molecular ligand to protein can effectively modulate the protein aggregation pathway. Here, we investigate the possible roles of three different bile acids, cholic acid (CA), taurocholic acid (TCA), and lithocholic acid (LCA) with varying hydrophobic and hydrogen bonding properties in inhibiting protein fibrillation. Bile acids are an important class of steroid compounds that are synthesized in the liver from cholesterol. Increasing evidence suggests that altered taurine transport, cholesterol metabolism, and bile acid synthesis have strong implications in Alzheimer's disease. We find that the hydrophilic bile acids, CA and TCA (taurine conjugated form of CA), are substantially more efficient inhibitors of lysozyme fibrillation than the most hydrophobic secondary bile acid LCA. Although LCA binds more strongly with the protein and masks the Trp residues more prominently through hydrophobic interactions, the lesser extent of hydrogen bonding interactions at the active site has made LCA a relatively weaker inhibitor of HEWL aggregation than CA and TCA. The introduction of a greater number of hydrogen bonding channels by CA and TCA with several key amino acid residues which are prone to form oligomers and fibrils has weakened the protein's internal hydrogen bonding capabilities for undergoing amyloid aggregation.

Short Peptoid Evolved from the Key Hydrophobic Stretch of Amyloid-β42 Peptide Serves as a Potent Therapeutic Lead of Alzheimer's Disease

Amyloid-β 42(Aβ42), an enzymatically cleaved (1-42 amino acid long) toxic peptide remnant, has long been reported to play the key role in Alzheimer's disease (AD). Aβ42 also plays the key role in the onset of other AD-related factors including hyperphosphorylation of tau protein that forms intracellular neurofibrillary tangles, imbalances in the function of the neurotransmitter acetylcholine, and even generation of reactive oxygen species (ROS), disrupting the cytoskeleton and homeostasis of the cell. To address these issues, researchers have tried to construct several strategies to target multiple aspects of the disease but failed to produce any clinically successful therapeutic molecules. In this article, we report a new peptoid called RA-1 that was designed and constructed from the hydrophobic stretch of the Aβ42 peptide, ¹⁶KLVFFA²¹. This hydrophobic stretch is primarily responsible for the Aβ42 peptide aggregation. Experimental study showed that the RA-1 peptoid is stable under proteolytic conditions, can stabilize the microtubule, and can inhibit the formation of toxic Aβ42 aggregates by attenuating hydrophobic interactions between Aβ42 monomers. Furthermore, results from various intracellular assays showed that RA-1 inhibits Aβ42 fibril formation caused by the imbalance in AchE activity, reduces the production of cytotoxic reactive oxygen species (ROS), and promotes neurite outgrowth even in the toxic environment. Remarkably, we have also demonstrated that our peptoid has significant ability to improve the cognitive ability and memory impairment in in vivo rats exposed to AlCl₃ and d-galactose (d-gal) dementia model. These findings are also validated with histological studies. Overall, our newly developed peptoid emerges as a multimodal potent therapeutic lead molecule against AD.

The Role of Buffers in Wild-Type HEWL Amyloid Fibril Formation Mechanism: A Methodological Approach

The amyloidophilic dyes thioflavin T and Congo red are small, yet powerful, molecules that allow the in vitro and in vivo detection of amyloid fibrils in protein solutions. Even though Congo red and thioflavin T binding assays are widespread techniques for unveiling amyloid fibers and are gradually replacing the more demanding X-ray diffraction method, handling samples containing amyloid fibrils is still challenging and can lead to false-positive/negative results. Here we describe a relatively straightforward procedure of preparing hen egg-white lysozyme amyloid fibrils in different buffer solutions and their detection with thioflavin T and Congo red, supported by an indispensable method for determining the secondary structure of proteins - circular dichroism.

Molecular Insights into the Inhibition of Dialysis-Related β2m Amyloidosis Orchestrated by a Bispidine Peptidomimetic Analogue

Dialysis-related amyloidosis (DRA) is considered an inescapable consequence of renal failure. Upon prolonged hemodialysis, it involves accumulation of toxic β2-microglobulin (β2m) amyloids in bones and joints. Current treatment methods are plagued with high cost, low specificity, and low capacity. Through our in vitro and in cellulo studies, we introduce a peptidomimetic-based approach to help develop future therapeutics against DRA. Our study reports the ability of a nontoxic, core-modified, bispidine peptidomimetic analogue "B(LVI)₂" to inhibit acid-induced amyloid fibrillation of β2m (Hβ2m). Using thioflavin-T, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and transmission electron microscopy analysis, we demonstrate that B(LVI)₂ delays aggregation lag time of Hβ2m amyloid fibrillation and reduces the yield of Hβ2m amyloid fibrils in a dose-dependent manner. Our findings suggest a B(LVI)₂-orchestrated alteration in the route of Hβ2m amyloid fibrillation resulting in the formation of noncytotoxic, morphologically distinct amyloid-like species. Circular dichroism data show gradual sequestration of Hβ2m species in a soluble nonamyloidogenic noncytotoxic conformation in the presence of B(LVI)₂. Dynamic light scattering measurements indicate incompetence of Hβ2m species in the presence of B(LVI)₂ to undergo amyloid-competent intermolecular associations. Overall, our study reports the antifibrillation property of a novel peptidomimetic with the potential to bring a paradigm shift in therapeutic approaches against DRA.

Lysozyme Amyloid Fibril-Integrated PEG Injectable Hydrogel Adhesive with Improved Antiswelling and Antibacterial Capabilities

Hydrogels with inherent antibacterial activities have been attracting increasing attention, particularly for biomedical applications. Biology provides a range of materials and mechanisms to meet diverse requirements for bacterial combating. Lysozyme after fibrillation (LZMF) has a much superior antibacterial ability than globular native lysozyme due to its decreased positive charges and increased hydrophobic β-sheet component. Here, we propose to design a poly(ethylene glycol) (PEG) cross-linked LZMF composite antibacterial hydrogel by utilizing the nucleophilic substitution reaction between LZMF and N-hydroxysuccinimide end groups on four-arm PEG-NHS. The generated PEG-LZMF hydrogel is bacteria-resistant both in vitro and in vivo as expected and has good biocompatibility. Moreover, the volume expansion of PEG can be significantly inhibited due to the presence of hydrophobic lysozyme amyloid fibrils. In addition, the relatively fast cross-linking reaction can make PEG-LZMF both injectable and shape-compatible. The simultaneous reaction with tissue-exposed -NH₂ or -SH also confers a tissue-adhesive ability. We envision that this hydrophobic lysozyme amyloid fibril-integrated PEG composite hydrogel can effectively adhere/protect open wounds and internal incisions and suppress pathogen infection through a biomimetic antibacterial mechanism. Considering the simple fabrication process, this multifunctional PEG-LZMF antibacterial hydrogel is promising for clinical transformation.

Self-assembled di- and tripeptide gels for the passive entrapment and pH-responsive, sustained release of an antidiabetic drug, glimepiride

Diabetes is a global epidemic that poses a severe challenge to public health. The characteristic features of this disease are hyperglycemia and deterioration of the function of pancreatic β-cells, which...

Comparative study of the hydrophobic interaction effect of pH and ionic strength on aggregation/emulsification of Congo red and amyloid fibrillation of insulin

Amyloid fibrillation is provoked by the conformational rearrangement of its source. In our previous study, we claimed that the conformational rearrangement of hen egg white lysozyme requires intermolecular aggregation/packing induced. Our proposed causality of the aggregation and amyloid formation was demonstrated by the quantitative dependence of amyloid fibrillation on pH difference from its isoelectric point (pI) and on the square root of ionic strength in order to reduce the intermolecular repulsion due to the shielding effect of electrolytes (DLVO effect). When Congo red has dianionic form at the pH higher than its pKa, it forms ribbon-like micelle colloids under lower ionic strength, while it loses electrostatic repulsion and aggregates to be emulsified in the octanolic phase under the higher ionic strength. These behaviors of Congo red were resembling to molecular assembly of surfactants. In contrast, the amyloid formation of insulin was proportional to the square root of ionic strength at the pH lower than its isoelectric point. Therefore, the trigger for conformational rearrangement of amyloid fibrillation is predominantly gripped by hydrophobic hydration and an electrostatic shielding effect. We concluded that the both behaviors of Congo red and insulin were derived from a driving force related to the hydrophobic hydration.

Chemical Properties Determine Solubility and Stability in βγ-Crystallins of the Eye Lens

βγ-Crystallins are the primary structural and refractive proteins found in the vertebrate eye lens. Because crystallins are not replaced after early eye development, their solubility and stability must be maintained for a lifetime, which is even more remarkable given the high protein concentration in the lens. Aggregation of crystallins caused by mutations or post-translational modifications can reduce crystallin protein stability and alter intermolecular interactions. Common post-translational modifications that can cause age-related cataracts include deamidation, oxidation, and tryptophan derivatization. Metal ion binding can also trigger reduced crystallin solubility through a variety of mechanisms. Interprotein interactions are critical to maintaining lens transparency: crystallins can undergo domain swapping, disulfide bonding, and liquid-liquid phase separation, all of which can cause opacity depending on the context. Important experimental techniques for assessing crystallin conformation in the absence of a high-resolution structure include dye-binding assays, circular dichroism, fluorescence, light scattering, and transition metal FRET.

Using amyloid autofluorescence as a biomarker for lysozyme aggregation inhibition

The assembly of proteins into amyloidogenic aggregates underlies the onset and symptoms of several pathologies, including Alzheimer's disease, Parkinson's disease and type II diabetes. Among the efforts for fighting these diseases, there is a great demand for developing novel, fast and reliable methods for in vitro screening of new drugs that may suppress or reverse amyloidogenesis. Recent studies unravelled a progressive increase in a blue autofluorescence upon amyloid formation originated from many different proteins, including the peptide amyloid-β, lysozyme or insulin. Herein, we propose a drug screening method using this property, avoiding the use of external probe dyes. We demonstrate that the inhibition of lysozyme amyloid formation by means of two known inhibitors, tartrazine and amaranth, can be monitored based on the autofluorescence of lysozyme amyloid aggregates. Our results show that amyloid luminescence is an intrinsic property that can be potentially applied in a screening assay, allowing the ranking of drug efficiency. The assays demonstrated here are fast to perform and suitable for scaling using microplate assays, configuring a new sensitive and economically feasible method.

Molecular recognition of human islet amyloid polypeptide assembly by selective oligomerization of thioflavin T

Selective oligomerization is a common phenomenon existing widely in the formation of intricate biological structures in nature. The precise design of drug molecules with an oligomerization state that specifically recognizes its receptor, however, remains substantially challenging. Here, we used scanning tunneling microscopy (STM) to identify the oligomerization states of an amyloid probe thioflavin T (ThT) on hIAPP_8-37 assembly to be exclusively even numbers. We demonstrate that both adhesive interactions between ThT and the protein substrate and cohesive interactions among ThT molecules govern the oligomerization state of the bounded ThT. Specifically, the work of the cohesive interaction between two head/tail ThTs is determined to be 6.4 k _B T, around 50% larger than that of the cohesive interaction between two side-by-side ThTs (4.2 k _B T). Overall, our STM imaging and theoretical understanding at the single-molecule level provide valuable insights into the design of drug compounds using the selective oligomerization of molecular probes to recognize protein self-assembly.

Damage of proteins at the air/water interface: Surface tension characterizes globulin interface stability

In the present study, we aimed to see what circumstances may cause protein damage at air/water interface and reveal the correlation between the surface properties of protein solution and the interface stability. The surface hydrophobicity and β-sheet of protein were determined by exogenous fluorescent probes, and the changes in the spatial structure of proteins were characterized by steady-state fluorescence spectroscopy. The surface tension was determined by the plate method, and such value was used to establish the correlation with the hydrophobicity and structure of the protein. Moreover, degree of aggregation in the presence or absence of Hofmeister salt in protein solution was investigated. There was a significant correlation between the surface tension and hydrophobicity of the protein solution (P < 0.05). The surface tension and structure of the protein also showed a significant correlation under the induction of pH (P < 0.05). Furthermore, when the protein was induced by the air/water interface, the surface tension, hydrophobicity, and structure of proteins were correlated, and protein aggregation was increased. When the additive induced a decrease in the surface tension of the protein solution, the protein aggregation was promoted. These findings provided valuable insights into the relationship between surface tension of the protein solution and interfacial stability and paved the way for future pre-formulation studies of therapeutic proteins.

Additional Thioflavin-T Binding Mode in Insulin Fibril Inner Core Region

Amyloidogenic protein aggregation into fibrils is linked to several neurodegenerative disorders, such as Alzheimer's or Parkinson's disease. An amyloid specific fluorescent dye thioflavin-T (ThT) is often used to track the formation of these fibrils in vitro. Despite its wide application, it is still unknown how many types of ThT binding modes to amyloids exist, with multiple studies indicating varying numbers. In this work, we examine the binding of ThT to insulin fibrils generated at pH 2.4 and reveal a possible inner core binding mode which is not accessible to the dye molecule after aggregation occurs.

Amyloid-Based Injectable Hydrogel Derived from Hydrolyzed Hen Egg White Lysozyme

Injectable hydrogels based on synthetic peptides have shown great promise in many biomedical applications. Yet, the high cost generally associated with synthetic peptides hinders the practical use of such peptide-based injectable hydrogel. To overcome this drawback, here, we propose to use the peptides from hydrolyzed low-cost natural protein as an economical and convenient peptide source to prepare an injectable hydrogel. We demonstrate the effectiveness of this alternative strategy using hen egg white lysozyme (HEWL) as an example. We used the peptide fragments from hydrolyzed HEWL as the gelator, and the magnesium ion as the performance enhancer to prepare the injectable hydrogel. We showed that the hydrogel is an amyloid gel as it was formed by a dense network of amyloid fibrils. We also showed that the hydrogel possesses a thixotropic property and displays a low cytotoxicity. The hydrolysis extent of HEWL was found to be a critical factor that influences the performance of the hydrogel. A fluorescence assay based on 8-anilinonaphthalene-1-sulfonic acid was proposed as a mean to precisely and conveniently control the hydrolysis extent of HEWL to enable the best injectability performance. At last, using doxorubicin as a model compound, we explored the potential of this amyloid-based hydrogel as an injectable drug carrier.

Comparative experiments of fibril formation from whey protein concentrate with homogeneous and secondary nuclei

Two types of special structures, homogeneous and secondary nuclei, form during fibril formation. The structural and functional properties of amyloid fibrils in whey protein concentrate (WPC) with different ratios of added homogeneous nuclei to secondary nuclei were investigated. Thioflavin T fluorescence analysis and kinetic equations indicated that two types of nuclei could accelerate WPC fibrillation compared with WPC self-assembling into amyloid fibrils, thereby reducing the lag time and increasing the number of fibrils. However, there were considerable differences in the nucleation-inducing capability of WPC fibrillation between homogeneous and secondary nuclei. The number of fibrils formed by adding homogeneous nuclei was higher than that obtained with secondary nuclei, the increase in the Th T fluorescence intensity induced by homogeneous nuclei was 1.83-fold much than secondary nuclei. Meanwhile, secondary nuclei yielded a 2.71-fold faster aggregation rate of WPC than homogeneous nuclei, particularly during the first hour of thermal treatment (protein mass ratio of nuclei to WPC 1:1). The gelation time of WPC after secondary nuclei addition was shorter, from 10 h (WPC (2.0/6.5)) to 4 h (WPC + HN) to 2 h (WPC + SN); however, the gel microstructure of WPC after the addition of homogeneous nuclei was denser, yielding a preferred water holding capacity.

Capreomycin inhibits the initiation of amyloid fibrillation and suppresses amyloid induced cell toxicity

Protein aggregation and amyloid fibrillation are responsible for several serious pathological conditions (like type II diabetes, Alzheimer's and Parkinson's diseases etc.) and protein drugs ineffectiveness. Therefore, a molecule that can inhibit the amyloid fibrillation and potentially clear amyloid fibrils is of great therapeutic value. In this manuscript, we investigated the antiamyloidogenic, fibril disaggregating, as well as cell protective effect of an anti-tuberculosis drug, Capreomycin (CN). Aggregation kinetics data, as monitored by ThT fluorescence, inferred that CN retards the insulin amyloid fibrillation by primarily targeting the fibril elongation step with little effect on lag time. Increasing the dose of CN boosted its inhibitory potency. Strikingly, CN arrested the growth of fibrils when added during the elongation phase, and disaggregated mature insulin fibrils. Our Circular Dichroism (CD) results showed that, although CN is not able to maintain the alpha helical structure of protein during fibrillation, reduces the formation of beta sheet rich structure. Furthermore, Dynamic Light Scattering (DLS) and Transmission Electronic Microscopy (TEM) analysis confirmed that CN treated samples exhibited different size distribution and morphology, respectively. In addition, molecular docking results revealed that CN interacts with insulin through hydrophobic interactions as well as hydrogen bonding, and the Hemolytic assay confirmed the non-hemolytic activity of CN on human RBCs. For future research, this study may assist in the rational designing of molecules against amyloid formation.