Β-sheet Secondary Structure Research Articles

Engineering regenerated nanosilk to efficiently stabilize pickering emulsions

A simple and efficient method of preparing regenerated nanosilk (RNS) has been developed based on fast dissolution of silk fibroin in 85 wt% aqueous phosphoric acid (PA) followed by coagulation in acetone. Compared with the previously reported methods to prepare RNS, this method used the non-toxic, non-volitle and cost-effective PA as the solvent and by-passed the time-consuming dialysis process typically required. Self-assembly of silk fibroin molecular chains during the regeneration process led to dominance of the folded β-sheet secondary structure, which avoided the unstable structure transitions of RNS as emulsifiers during actual use. The as prepared RNS was further employed to stabilize the Pickering emulsions. Smaller RNS, higher RNS loading, and lower oil/water (O/W) ratio favored the formation of more stable emulsions. The prepared emulsions were stable for more than one month and were insensitive to environmental stresses such as heating and high ionic strength, but responsive to pH changes. Overall, a simple and efficient method was proposed to prepare RNS with tunable properties and great potential for application in food and cosmetic formula.

Insights into the mechanism on Glucono-delta-lactone induced gelation of soybean protein at subunit level

To elucidate the gelation process and gel properties of coagulation in soybean protein at subunit level, the dispersions of subunits (αα′- and β-subunit) of β-conglycinin and polypeptides (acidic and basic polypeptides) of glycinin were coagulated by Glucono-delta-lactone (GDL), and the gelation processes were monitored with a dynamic rheometer. The rheological properties, microstructure, water distribution, and secondary structure of the gels were determined as well. The results showed that the β-subunit and basic polypeptide coagulated faster, while αα′-subunit and acidic polypeptide developed firmer and finer gels, who had stronger ability of water holding and contained higher content of β-sheet structure. The GDL-induced subunits/polypeptides gel network were dominated by hydrophobic interactions and disulfide bonds. It is proposed that the mechanism on gelation of soybean protein at subunit level as: with acidification of GDL, the basic polypeptide and β-subunit initially aggregate and form a proto-gel matrix. Subsequently, with the developing of gelation, α- and α′-subunits, especially acidic polypeptide, who is the last one to coagulate, complements to form finer and firmer network, and finally grows together to a mature gel. Besides the gelation rate, the higher content of β-sheet secondary structure and better water holding ability of acidic polypeptide and αα′-subunits would also contribute to the firmness of gel. The elucidation of the gelation mechanism at subunit level would support innovation of gelling technique and benefit the soybean industry.

Ultrasonic-assisted preparation of α-Tocopherol/casein nanoparticles and application in grape seed oil emulsion

In this work casein (CN) was used as a carrier system for the hydrophobic agent α-tocopherol (α-TOC), and an amphiphilic self-assembling micellar nanostructure was formed with ultrasound treatment. The interaction mechanism was detected with UV–Vis spectroscopy, fluorescence spectroscopy, proton spectra, and Fourier transform infrared spectroscopy (FTIR). The stability of the nanoparticles was investigated by using typical processing and storage conditions (thermal, photo, 20 ± 2 °C and 4 ± 2 °C). Oil-in-water emulsions containing the self-assembled nanoparticles and grape seed oil were prepared, and the effect of emulsion oxidation stability was studied using the accelerated Rancimat method. The results indicated that the UV–Vis spectra of α-TOC/CN nanoparticles complexes were different for ultrasonic treatments performed with different combinations of power (100, 200, 300 W) and time (5, 10, and 15 min). The results of UV–Vis fluorescence spectrum data indicated that the secondary structure of casein changed in the presence of α-TOC. The nanoparticles exhibited the chemical shifts of conjugated double bonds. Interactions between α-TOC and casein at different molar concentrations resulted in a quenching of the intrinsic fluorescence at 280 nm and 295 nm. Moreover, by performing FTIR deconvolution analysis and multicomponent peak modeling, the relative quantitative amounts of α-helix and β-sheet protein secondary structures were determined. The self-assembled nanoparticles can improve the stability of α-TOC by protecting them against degradation caused by light and oxygen. The antioxidant activity of the nanoparticles was stronger than those of the two free samples. Lipid hydroperoxides remained at a low level throughout the course of the study in emulsions containing 200 mg α-TOC/kg oil with the nanoparticles. The presence of 100 and 200 mg α-TOC/kg oil led to a 78.54 and 63.54 μmol/L inhibition of TBARS formation with the nanoparticles, respectively, vs the free samples containing control after 180 mins.

Optically transparent silk fibroin nanofiber paper maintaining native β-sheet secondary structure obtained by cyclic mechanical nanofibrillation process

Optically transparent fibroin nanofiber (FNF) paper was obtained without using binders by passing a fibroin suspension through a mechanical nanofibrillation process using a water-jet. The optical transmittance of the nanofiber paper increased with the number of passes through the water-jet and reached 79.3% and 80.3% of light at 600 nm after 15 and 30 passes, respectively. The fibroin of the transparent nanopaper remained fibrous with a native β-sheet secondary structure. Therefore, the transparent nanopaper showed a high elastic modulus, high thermal durability, and low thermal expansion. This novel protein material, which can be fabricated without toxic chemicals or organic solvents, is bio-friendly and shows promise for new applications in biocompatible photonic devices.

SDS modulates amyloid fibril formation and conformational change in succinyl-ConA at low pH

The anionic surfactant sodium dodecyl sulfate (SDS) is homologous to the cellular membrane lipids, and is known to stimulate amyloid fibrillation in several proteins. However, the mechanism by which SDS influences aggregation and structural changes in succinylated protein has not been determined. In this study, we observed the effects of variable SDS concentrations on succinyl-ConA aggregation at pH 3.5 and proposed a possible mechanism of SDS-induced succinyl-ConA aggregation. We used several biophysical techniques to identify the changes caused by SDS. Our results suggest that SDS stimulates succinyl-ConA aggregation in a concentration-dependent manner. From turbidity measurements, it was evident that a very low concentration (<0.1 mM) of SDS did not induce succinyl-ConA aggregation and proteins remained soluble. However, aggregations were observed at 0.1–2.5 mM SDS, which then dissipated at SDS concentrations above 2.5 mM. Far-UV CD results suggest that the β-sheet secondary structure of succinyl-ConA transformed into the cross-β-sheet structure in the presence of aggregating SDS concentrations. Notably, at SDS concentrations above 2.5 mM, the succinyl-ConA β-sheet transformed into an α-helical structure. The SDS-induced succinyl-ConA amyloid-like aggregates were confirmed by transmission electron microscopy (TEM). We propose that SDS modulates amyloid fibrillation in succinyl-ConA due to electrostatic and hydrophobic interactions and succinylation affects SDS-induced succinyl-ConA aggregation.

Development of disulfide bond crosslinked antimicrobial peptide hydrogel

In the past decades, antimicrobial peptides have emerged as potential candidates as antimicrobial agents, and antimicrobial peptide-based hydrogels have been extensively studied as wound dressings or fillers. In this work, a PAF26 peptide derivative with a cysteine amino acid on the C-terminal was designed to develop covalently crosslinked antimicrobial hydrogel. The hydrogel could be formed in neutral solution and thiol in the cysteine residue could be oxidised to disulfide bond in the hydrogel. It was confirmed that the formed hydrogel had strongly crosslinked networks with β-sheet and unordered coil secondary structures. In addition, antimicrobial experiments demonstrated that the formed hydrogel had excellent antimicrobial abilities via Candida albicans and could inhibit the growth of Staphylococcus aureus and Escherichia coli , gives the possibility of being used for fungi and bacteria-induced infection.

Surface analysis of novel fibroin films based on well-preserved crystalline structures

We recently reported that a highly homogeneous aqueous suspension of fibroin nanofiber (FNF) can be simply obtained by mechanical water-grinding a heterogeneous aqueous fibroin slurry and that the FNF in the suspension preserves the native β-sheet secondary structure during this mechanical treatment. The current study reports the surface properties of well-preserved crystalline structure novel FNF film from water-grinding preparation as compared with those of typical, conventionally prepared regenerated fibroin (RF) film. RF film was not treated with alcoholic solutions and was verified to be amorphous from a WAXD diffraction diagram. The air-side surfaces of the FNF semi-crystalline and RF amorphous films were studied to clarify differences using scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), static water contact angle, and X-ray photoelectron spectroscopy (XPS). The well-preserved crystalline in the FNF film was found to exist near a slightly deep surface region and to act as a physically cross-linking domain, governing the molecular motions of the amorphous polypeptide chains at the very shallow surface region.

Influence of pH and temperature on the physicochemical and functional properties of Bambara bean protein isolate

Bambara bean is a rich low-cost protein source and a functional ingredient in the food industry. We investigated the effects of temperature and different pH on the physicochemical and functional properties of Bambara bean protein isolate. Vicilin was the major protein of Bambara bean as revealed by SDS PAGE analysis. The emulsifying capacity of protein isolate was highest at 80 °C, pH 9 while emulsion stability was highest at pH 4. Generally, increase in temperature decreased protein solubility at pH 4 and 7, while increase was observed at pH 9 and 100 °C. The hydrophobicity of isolate was highest at pH 4 and lowest at pH 9, regardless of temperature. Protein isolate possessed highly compact β-sheet and α-helix secondary structures in proportions greater than 75% (at pH 9 and 50 °C). Increase in temperature generally promoted protein rearrangement and partial unfolding. Protein secondary structure and surface hydrophobicity can predict food functionality, directly affecting protein behavior during formulation and long-term storage. This study clearly demonstrated the potential of exploiting pulse protein isolates as nutritional and functional ingredients through temperature and pH control.

Gelation of a Pentapeptide in Alcohols.

Properties of solvents such as polarity and H-bond-forming ability are critical for the formation of an organogel and have a significant impact on the gel behavior, as solvents are the majority of organogel systems. However, so far, there is still a lack of systematic studies regarding the effects of molecular structures of solvents on the characteristics of organogels. Motivated by revealing such a relationship, in this paper, we studied the morphologies of assemblies, gelation behaviors, and secondary structures of a pentapeptide termed EAF-5 in a wide variety of alcohols. The side chains and lengths of carbon chains of the solvent molecules were found to play a critical role in the self-assembly and gelation of EAF-5. EAF-5 was capable of self-assembling into fibers and entangling into a network in alcohols including ethanol, propanol, butanol, n-pentanol, and n-hexanol, which further immobilized the corresponding alcohols to form gels. In these organogels, increasing β-sheet secondary structures of the peptides were formed by introducing side chains and extending the length of primary alcohol molecules. We hypothesized that alcohol molecules with extended lengths and side chains reduced the gelator-solvent interactions and promoted the gelator-gelator interactions, resulting in the self-assembly of EAF-5 into fibril structures and development of gels. These findings provide a new sight into the interactions between gelators and solvents and are helpful for designing peptide-based organogelators.

Injectable and pH-Sensitive Hyaluronic Acid-Based Hydrogels with On-Demand Release of Antimicrobial Peptides for Infected Wound Healing.

Antibiotics' abuse in bacteria-infected wounds has threatened patients' lives and burdened medical systems. Hence, antibiotic-free hydrogel-based biomaterials, which exhibit biostability, on-demand release of antibacterial agents, and long-lasting antimicrobial activity, are highly desired for the treatment of chronic bacteria-infected wounds. Herein, we developed a hyaluronic acid (HA)-based composite hydrogel, with an antimicrobial peptide [AMP, KK(SLKL)3KK] as a cross-linking agent through Schiff's base formation, which exhibited an acidity-triggered release of AMP (pathological environment in bacteria-infected wounds, pH ∼ 5.5-5.6). During the self-assembly process, AMP adopted an antiparallel β-sheet secondary structure due to the alternate arrangement of hydrophobic and hydrophilic residues of amino acids. Owing to Schiff's base formation between the primary amines derived from lysine residues and the aldehydes in oxidized HA, the AMP-HA composite hydrogel exhibited injectability, high biostability, and enhanced mechanical strength. Importantly, both AMP and the AMP-HA composite showed excellent broad-spectrum antibacterial activity in vitro and in vivo. Specifically, the AMP-HA composite hydrogel exhibited on-demand full thickness wound healing in an infected mice model. Therefore, this work provides an efficient strategy to fabricate antibiotic-free hydrogel-based biomaterials for the management of chronic bacteria-infected wounds.

Tunable inhibition of β-amyloid peptides by fast green molecules* *Project supported by the National Natural Science Foundation of China (Grand No. 11804174), Qian Xuesen Collaborative Research Center of Astrochemistry and Space Life Sciences, and K. C. Wong Magna Fund in Ningbo University.

The aggregation of β-amyloid (Aβ) protein into toxic intermediates and mature fibrils is considered to be one of the main causes of Alzheimer’s disease (AD). Small molecules as one of blockers are expected to be the potential drug treatment for the disease. However, the nucleation process in molecular assembly is less informative in the literatures. In this work, the formation of Aβ(16-22) peptides was investigated with the presence of small molecule of fast green (FG) at the initial aggregation stage. The results exhibited the tunable inhibitory ability of FG molecules on Aβ(16-22) peptides. Atomic force microscopy (AFM) demonstrated that the inhibitory effect would be dependent on the dose of FG molecules, which could delay the lag time (nucleation) and form single layer conjugates. Spectral measurements further showed that the β-sheet secondary structure of Aβ(16-22) reduced dramatically after the presence of FG molecules. Instead, non-β-sheet nanosheets were formed when the FG/Aβ(16-22) ratio reached 1:1. In addition, the cytotoxicity of aggregates reduced greatly with the presence of FG molecules compared with the Aβ(16-22) fibrils. Overall, this study provided a method for suppressing the toxic amyloid aggregates by FG molecules efficiently, and also showed a strategy for fabrication of two-dimensional materials by small molecules.

P132 Uncovering blood biomarkers of Inflammatory Bowel Diseases by Raman spectroscopy and FAP dosage: toward a noninvasive triage of patients in first care diagnostic

Abstract Background Currently, a major point of concern in the management of Inflammatory Bowel Diseases (IBD) is the absence of accurate and specific circulating biomarkers able to drive diagnosis in a timely and noninvasive manner. Aim of the present study was to explore blood biomarkers of IBD by coupling the targeted detection of circulating fibroblast activation protein (FAP), a recognized valuable marker of bowel lesion in IBD, and Raman spectroscopy (RS), a quick and label-free metabolomic technique that provides a real-time biochemical characterization of plasma samples without any previously known target. Methods Blood samples were collected from over 140 patients with IBD and 170 control subjects matched for gender and age. Isolated plasma was analysed by enzyme-linked immunosorbent assay for quantitative detection of circulating form of FAP. RS was performed on dry droplets of plasma, with the aim to decipher specific fingerprint of IBD in peripheral blood. A predictive model was built on FAP and Raman data separately, to determine specificity, sensitivity and accuracy of the two approaches in patients classification. Supervised multivariate model was applied on a subset of 203 patients to discriminate IBD and control subjects based on combined datasets. Results FAP levels were reduced in patients with IBD as compared to controls (p&amp;lt;0.0001). The sensitivity and specificity of FAP were 70% and 84% based on the optimal cutoff (57.6 ng mL-1, AUC=0.78). Raman spectra of IBD plasma revealed significant differences in peaks corresponding to carotenoids, proteins with β-sheet secondary structure, lipids and aromatic amino-acids. A machine learning model was applied on a subset of patients reaching an accuracy of 85% in classifying IBD and control subjects. No statistically significant differences were observed so far between the discriminative performance of the sole RS or the combination of RS and FAP. Conclusion RS and FAP dosage enable new discoveries in the biological fingerprint of IBD plasma and provide novel candidate biomarkers of IBD. Our preliminary results strongly suggest that novel blood-based approaches could represent a fast noninvasive way to triage patents with suspected IBD in first care diagnostic, to be applied prior to further specific evaluation.

Zika virus capsid anchor forms cytotoxic amyloid-like fibrils

Capsid-anchor (CA) of Zika virus (ZIKV) is a small, single-pass transmembrane sequence that separates the capsid (C) protein from downstream pre-membrane (PrM) protein. During polyprotein processing, CA is cleaved-off from C and PrM and left as a membrane-embedded peptide. CA plays an essential role in the assembly and maturation of the virus. However, its independent folding behavior is still unknown. Therefore, in this study, we investigated the amyloid-forming propensity of CA at physiological conditions. We observed the aggregation behavior of CA peptide using dye-binding assays and ThT kinetics. The morphological analysis of CA aggregates explored by high-resolution microscopy (TEM, AFM) and Far-UV CD spectroscopy revealed characteristic amyloid-like fibrils rich in β-sheet secondary structure. Further, the effect on mammalian cells exhibited the cytotoxic nature of the CA amyloid-fibrils. Our findings collectively shed light on the amyloidogenic phenomenon of flaviviral protein, which may contribute to their infection.

In situ Sub-Cellular Identification of Functional Amyloids in Bacteria and Archaea by Infrared Nanospectroscopy.

Formation of amyloid structures is originally linked to human disease. However, amyloid materials are found extensively in the animal and bacterial world where they stabilize intra- and extra-cellular environments like biofilms or cell envelopes. To date, functional amyloids have largely been studied using optical microscopy techniques in vivo, or after removal from their biological context for higher-resolution studies in vitro. Furthermore, conventional microscopies only indirectly identify amyloids based on morphology or unspecific amyloid dyes. Here, the high chemical and spatial (≈20 nm) resolution of Infrared Nanospectroscopy (AFM-IR) to investigate functional amyloid from Escherichia coli (curli), Pseudomonas (Fap), and the Archaea Methanosaeta (MspA) in situ is exploited. It is demonstrated that AFM-IR identifies amyloid protein within single intact cells through their cross β-sheet secondary structure, which has a unique spectroscopic signature in the amide I band of protein. Using this approach, nanoscale-resolved chemical images and spectra of purified curli and Methanosaeta cell wall sheaths are provided. The results highlight significant differences in secondary structure between E. coli cells with and without curli. Taken together, these results suggest that AFM-IR is a new and powerful label-free tool for in situ investigations of the biophysical state of functional amyloid and biomolecules in general.

Assessment of Amyloid Forming Tendency of Peptide Sequences from Amyloid Beta and Tau Proteins Using Force-Field, Semi-Empirical, and Density Functional Theory Calculations.

A wide variety of neurodegenerative diseases are characterized by the accumulation of protein aggregates in intraneuronal or extraneuronal brain regions. In Alzheimer’s disease (AD), the extracellular aggregates originate from amyloid-β proteins, while the intracellular aggregates are formed from microtubule-binding tau proteins. The amyloid forming peptide sequences in the amyloid-β peptides and tau proteins are responsible for aggregate formation. Experimental studies have until the date reported many of such amyloid forming peptide sequences in different proteins, however, there is still limited molecular level understanding about their tendency to form aggregates. In this study, we employed umbrella sampling simulations and subsequent electronic structure theory calculations in order to estimate the energy profiles for interconversion of the helix to β-sheet like secondary structures of sequences from amyloid-β protein (KLVFFA) and tau protein (QVEVKSEKLD and VQIVYKPVD). The study also included a poly-alanine sequence as a reference system. The calculated force-field based free energy profiles predicted a flat minimum for monomers of sequences from amyloid and tau proteins corresponding to an α-helix like secondary structure. For the parallel and anti-parallel dimer of KLVFFA, double well potentials were obtained with the minima corresponding to α-helix and β-sheet like secondary structures. A similar double well-like potential has been found for dimeric forms for the sequences from tau fibril. Complementary semi-empirical and density functional theory calculations displayed similar trends, validating the force-field based free energy profiles obtained for these systems.

Membrane-bound Δ12 fatty acid desaturase (FAD12); From Brassica napus to E. coli expression system

Fatty acid desaturase catalyzes the desaturation reactions by insertion of double bonds into the fatty acyl chain, producing unsaturated fatty acids. Though soluble fatty acid desaturases have been studied widely in advanced organisms, there are very limited studies of membrane fatty acid desaturases due to the difficulty of generating recombinant desaturase. Brassica napus is a rapeseed, which possesses a range of different membrane-bound desaturases capable of producing fatty acids including Δ3, Δ4, Δ8, Δ9, Δ12, and Δ15 fatty acids. The 1155 bp open reading frame of Δ12 fatty acid desaturase (FAD12) from Brassica napus codes for 383 amino acid residues with a molecular weight of 44 kDa. It was expressed in Escherichia coli at 37 °C in soluble and insoluble forms when induced with 0.5 mM IPTG. Soluble FAD12 has been purified using Ni2+-Sepharose affinity chromatography with a total protein yield of 0.728 mg/mL. Gas chromatography–mass spectrometry (GC–MS) analysis revealed that desaturase activity of FAD12 could produce linoleic acid from oleic acid at a retention time of 17.6 with a conversion rate of 47%. Characterization of purified FAD12 revealed the optimal temperature of FAD12 was 50 °C with 2 mM preferred substrate concentration of oleic acid. Analysis of circular dichroism (CD) showed FAD12 was made up of 47.3% and 0.9% of alpha-helix and β-sheet secondary structures. The predicted Tm value was 50.2 °C.

Nanostructure, Self-Assembly, Mechanical Properties, and Antioxidant Activity of a Lupin-Derived Peptide Hydrogel.

Naturally occurring food peptides are frequently used in the life sciences due to their beneficial effects through their impact on specific biochemical pathways. Furthermore, they are often leveraged for applications in areas as diverse as bioengineering, medicine, agriculture, and even fashion. However, progress toward understanding their self-assembling properties as functional materials are often hindered by their long aromatic and charged residue-enriched sequences encrypted in the parent protein sequence. In this study, we elucidate the nanostructure and the hierarchical self-assembly propensity of a lupin-derived peptide which belongs to the α-conglutin (11S globulin, legumin-like protein), with a straightforward N-terminal biotinylated oligoglycine tag-based methodology for controlling the nanostructures, biomechanics, and biological features. Extensive characterization was performed via Circular Dichroism (CD) spectroscopy, Fourier Transform Infrared spectroscopy (FT-IR), rheological measurements, and Atomic Force Microscopy (AFM) analyses. By using the biotin tag, we obtained a thixotropic lupin-derived peptide hydrogel (named BT13) with tunable mechanical properties (from 2 to 11 kPa), without impairing its spontaneous formation of β-sheet secondary structures. Lastly, we demonstrated that this hydrogel has antioxidant activity. Altogether, our findings address multiple challenges associated with the development of naturally occurring food peptide-based hydrogels, offering a new tool to both fine tune the mechanical properties and tailor the antioxidant activities, providing new research directions across food chemistry, biochemistry, and bioengineering.

Quality Attributes of Plasma Derived Human Fibrinogen (Fibrogen-I®)

BACKGROUND Fibrinogen is an important component of hemostasis and clot formation. Replacement therapy with a human Fibrinogen concentrate is the preferred therapeutic option for patients with congenital or acquired Fibrinogen insufficiency. To make the Fibrinogen available for treatment of such patients, Fibrogen-I®, a lyophilized product purified from pooled human plasma was developed and extensively characterized. The product quality attributes were assessed by different biochemical, functional and structural analytical methods. MATERIAL AND METHODS Functional activity of Fibrinogen in the Fibrogen-I® was demonstrated by determination of its clottable protein activity. Purity profiling of Fibrogen-I® was evaluated by SE-HPLC method. Activation and fibrinolysis markers like D-dimer, plasminogen was determined by automated coagulometer and fibrinopeptide A activity by ELISA. Far UV CD analysis was also performed by CD Spectrometer. RESULTS The product exhibited high purity 89.7% by SE-HPLC. Activation and Fibrinolysis marker proteins in the drug product were negligible. The high purity and integrity of Fibrogen-I® is underlined by the ratio of Fibrinogen activity by Clauss/clottable protein with mean calculated value of 0.9 which is in close proximity with theoretical value 1 indicating fully native Fibrinogen. The results of far-UV CD spectroscopy revealed that Fibrogen-I® exists mostly as a β-sheet secondary structure, which is in accordance with the three-dimensional structure of human Fibrinogen. Downscaling experiments for the two dedicated orthogonal pathogen inactivation steps, ie solvent detergent treatment and dry heat treatment, exhibited pathogen safety. DISCUSSION Fibrogen-I® exhibited specific functional activity, desirable quality attributes, pathogen safety and the ability to be made available to patients requiring fast and effective Fibrinogen replacement.

Embryonic cuticle from artemia cyst shell displays amyloid-like characteristics and nontoxicity after oral consumption

Artemia cysts are the essential food product for industrial larviculture of fishes. The cyst shell protects the artemia embryo from mechanical damage, ultraviolet light, excessive water loss, thermal variation and anoxia condition. However, the underlying mechanism of such environmental protection is largely unclear. The embryonic cuticle of cyst shell mainly constitutes chitin and proteins. Absence of cyst shell proteins compromises embryo survival. In literature, there are few examples of functional amyloids where proteins adapt amyloid-like structures and act as protective covering. We hypothesized that the proteins from the embryonic cuticle of artemia cyst shell may have amyloid-like properties. Using FTIR and CD analysis, we found that proteins in embryonic cuticle have high β-sheet secondary structures. Embryonic cuticles displayed high Congo red binding affinity and stained samples showed apple-green birefringence under polarized light, confirming the presence of amyloid-like structures. Amyloid structures have a tendency to propagate and cause amyloidosis. However, feeding of amyloid rich embryonic cuticles to zebrafish did not show any signs of discomfort or morbidity and amyloid deposition. Taken together, the study reveals that amyloid-like structures are present in embryonic cuticle of artemia cyst and their consumption does not induce amyloidosis in zebrafish.

Tip-enhanced Raman spectroscopy of Aβ(1-42) fibrils

Using tip-enhanced Raman spectroscopy (TERS) imaging with a lateral optical resolution of ~16 nm, the heterogeneity of Aβ(1-42) fibrils implicated in Alzheimer’s disease is investigated. The amount and spatial distribution of TERS bands assigned to aromatic amino acid residues (histidine, tyrosine and phenylalanine) and to parallel β-sheet and random coil secondary structures suggest that both the surface and core of Aβ(1-42) fibrils are probed, confirm the twisted nature of the fibrils and reveal the presence of several β-sheet and disordered fibril regions with different hydrophilicity. This study completes and bears out literature TERS data on Aβ(1-42) amyloid fibrils.