Β-pleated Sheet Research Articles

Modern Approaches To Cardiovascular Amyloidosis Treatment

Cardiovascular (cardiac) amyloidosis (CA) is a clinical pathology, usually of a geneticallymediated nature, initiated by the precipitation process of the insoluble fibrous protein with β-pleated sheet secondary structure. Such anomalous changes lead to the formation of amyloid fibrils, which may give rise to various forms of amyloidosis. Amyloid formation can be found in various organs and systems, such as cardiovascular system, central and peripheral nervous systems, liver, urinary tract, etc. CA is a rare degenerative disease resulting in congestive cardiac failure and heart arrhythmia with subsequent untimely death. Unfortunately, up to date, the choice of medications for treating amyloidosis is very limited. In this paper, we review clinically used pharmaceutical drugs for CA treatment, along with some delivery systems for such compounds.

Post-translational modification of amyloid a protein in patients with AA amyloidosis

AA amyloidosis is a disease caused by extracellular deposition of insoluble β-pleated sheet fibrils composed of amyloid A (AA) protein, an amino (N)-terminal fragment of serum amyloid A (SAA). The deposits disrupt tissue structure and compromise organ function. Although the disease is systemic, deposition in kidney glomeruli is the most common manifestation. The leading cause of AA amyloidosis is sustained or recurrent inflammation accompanied by elevated levels of SAA. Factors determining the conversion of SAA to AA amyloid fibrils have yet to be fully resolved. Herein, we present liquid chromatography tandem-mass spectrometry (LC-MS/MS) analysis of AA proteins purified from eight patients with AA amyloidosis. For the first time, post-translational modifications (PTM), including carbamylation, acetylation and oxidation, were identified on AA peptides; all eight samples showed some degree of PTM. The amyloid in 6 samples comprised peptides derived from SAA1 with few or none from SAA2, while the other two samples contained both SAA1- and SAA2-derived peptides. N-terminal AA peptides beginning with Arg1 as well as AA peptides starting with Ser2 were present in five of the eight samples, while all or nearly all of the N-terminal peptides in the other three samples lacked Arg1. These data demonstrate that multiple species of AA amyloid proteins can comprise the subunits in amyloid fibrils and raise the possibility that PTM may play a role in fibrillogenesis.

Cloning, Characterization, Expression Analysis, and Agglutination Studies of Novel Gene Encoding β-d-Galactose, N-Acetyl-d-Glucosamine and Lactose-Binding Lectin from Rice Bean (Vigna umbellata)

Lectins are glycoproteins and known for their peculiar carbohydrate-binding activity and their insect-pest-resistant properties. Earlier we have published our research finding on novel gene encoding Bowman-Birk type protease inhibitor with insecticidal properties from rice bean. This paper presents first report on cloning, sequencing, and expression of RbL ORF of 843bp encoding 280 amino acids long lectin precursor from rice bean (Vigna umbellata) seeds. Blast analysis revealed more than 90% similarity of RbL protein with Vigna aconitifolia and Vigna angularis lectins. Phylogenetic analysis also revealed a close relationship between RbL and other legume lectins. Sequence analysis of genomic DNA revealed intronless nature of RbL gene (GenBank accession No. MT043160). The isolated RbL ORF was expressed in E. coli BL-21(DE3) cells and maximum expression was recorded with 0.5mM IPTG after 4h incubation at 37°C. Western blotting confirmed RbL protein expression in E. coli. Recombinant protein (His6-RbL) of ~ 35kDam.wt was purified using Ni-NTA affinity chromatography to the extent of 0.26mg/ml. In silico analysis characterized RbL protein as acidic, stable, hydrophobic, and secretary protein with one signal peptide cleavage site (A26-A27) and four N-glycosylation sites. Template-based 3D model of RbL was structured using MODELLER tool and validated as good quality model. Structural analysis revealed dominance of β-pleated sheets and β-turns in RbL protein structure. β-D-galactose, N-acetyl-D-glucosamine, and lactose were predicted as putative ligands for RbL protein. Hydrogen bonding and hydrophobic forces were the major interactions between the predicted ligands and RbL protein. Agglutination and agglutination inhibition assays confirmed the binding specificity of RbL protein with the trypsinized rabbit erythrocytes and with the predicted ligands, respectively. Gene ontology analysis functionally annotated RbL protein as a plant defense protein. The novel information generated in the study is not mere pre-experimental findings but could also lay foundation for future research on exploring RbL gene and encoding protein for different biomedical and biotechnological applications.

Effect of ultrasonic treatment on the structure and functional properties of mantle proteins from scallops (Patinopecten yessoensis)

In this study, scallop mantle protein was treated by ultrasound at different powers, and then analyzed by ANS fluorescent probes, circular dichroism spectroscopy, endogenous fluorescence spectrum, DNTB colorimetry and in-vitro digestion model to elucidate the structure–function relationship. The results indicated that ultrasound can significantly affect the secondary structure of scallop mantle protein like enhancing hydrophobicity, lowering the particle size, increasing the relative contents of α-helix and decreasing contents of β-pleated sheet, β-turn and random coil, as well as altering intrinsic fluorescence intensity with blue shift of maximum fluorescence peak. But ultrasound had no effect on its primary structure. Moreover, the functions of scallop mantle protein were regulated by modifying its structures by ultrasound. Specifically, the protein had the highest performance in foaming property and in-vitro digestibility under ultrasonic power of 100 W, oil binding capacity under 100 W, water binding capacity under 300 W, solubility and emulsification capacity under 400 W, and emulsion stability under 600 W. These results prove ultrasonic treatment has the potential to effectively improve functional properties and quality of scallop mantle protein, benefiting in comprehensive utilization of scallop mantles.

Abstracts and Case Studies for the College of American Pathologists 2021 (CAP21) Annual Meeting

Abstracts and Case Studies for the College of American Pathologists 2021 (CAP21) Annual Meeting

Structural dynamics of Rhipicephalus microplus serpin-3

ABSTRACT Cattle ticks, Rhipicephalus (Boophilus) microplus, have a serious impact on livestock worldwide. For tick control, host vaccination is more sustainable than chemical. Salivary serpin (serine protease inhibitor) from R. microplus (RmS-3) is a potential anti-tick vaccine candidate antigen. Like other serpins, RmS-3 has a suicide inhibition mechanism, where the reactive centre loop (RCL) is cleaved and then inserted into the main β-pleated sheet. This causes the breakdown of serpin into two regions (core domain and cleaved polypeptide). A small sequence variation of RmS-3 was observed among specimens in Thailand included three extra amino acids (T147, K180, N193). Molecular Dynamics simulations of the previously reported (Micro) and the novel Thai RmS-3 (Thai) were conducted in comparison. Overall, Micro is more rigid than Thai. Having additional T147 and K180 enhance the structural flexibility in Thai. Both residues are located close to areas that perform a distinct conformational change, so T147 and K180 may impact inhibitory activity of Thai RmS-3. In contrast, N193 seems to have a minor effect. A presence of T147 and K180 in Thai seems to cause significant differences in structural dynamics which may lead to different degrees of inhibition activity. Further experimental studies are required.

PH-dependent disintegration of insulin amyloid fibrils monitored with atomic force microscopy and surface-enhanced Raman spectroscopy

Aggregation of insulin into amyloid fibrils is characterized by the conversion of the native secondary structure of the peptide into an enriched ß-sheet conformation. In vitro, the growth or disintegration of amyloid fibrils can be influenced by various external factors such as pH, temperature etc. While current studies mainly focus on the influence of environmental conditions on the growth process of insulin fibrils, the present study investigates the effect of pH changes on the morphology and secondary structure of mature fibrils. In the experiments, insulin is fibrillated at pH 2.5 and the grown mature fibrils are suspended in pH 4–7 solutions. The obtained structures are analyzed by atomic force microscopy (AFM) and surface-enhanced Raman spectroscopy (SERS). Initially grown mature fibrils from pH 2.5 solutions show a long and intertwined morphology. Increasing the solution pH initiates the gradual disintegration of the filamentous morphology into unordered aggregates. These observations are supported by SERS experiments, where the spectra of the mature fibrils show mainly a β-pleated sheet conformation, while the amide I band region of the amorphous aggregates indicate exclusively α-helix/unordered structures.The results demonstrate that no complex reagent is required for the disintegration of insulin fibrils. Simply regulating the pH of the environment induces local changes in the protonation state within the peptide chains. This effectively disrupts the well-ordered β-sheet structure network based on hydrogen bonds.

Creation of a peptide database of corneous beta-proteins of marine turtles for the identification of tortoiseshell: archaeological combs as case study.

Tortoiseshell is a proteinaceous material derived from the scutes of marine turtles, and was shaped into an abundance of objects, especially luxurious items, at its peak in the seventeenth and eighteenth century. It has continued to be used even after the advent of plastics and remains one of the main causes of illegal poaching of marine turtles, in particular the hawksbill turtle Eretmochelys imbricata. Tortoiseshell is made of structural proteins, of which the most abundant are known as β-keratins, or ‘corneous beta-proteins' (CBPs), a family of short proteins containing a central structure in β-sheets. There are, however, few CBP sequences of marine turtles in protein databases. The scutes of the five main species of marine turtles (Chelonia mydas, Caretta caretta, Eretmochelys imbricata, Lepidochelys olivacea and Lepidochelys kempii) were analysed by proteomics, using nano-liquid chromatography-Orbitrap-mass spectrometry to generate peptidic markers for species identification. A total of 187 marker sequences were identified, the large majority of them obtained from automated de novo sequencing. The sequences were classified into peptides A to F: A to D at the N-terminus and central region that forms the β-pleated sheets, E1–4 for a variable region of glycine-repeats region and F at the C-terminus. The markers were tested against a set of combs discovered in various archaeological sites of modern period in France, successfully identifying hawksbill turtle and highlighting patterns of degradation in archaeological tortoiseshell.

Mechanics and hierarchical structure transformation mechanism of wool fibers

Various natural protein materials have hierarchical microscale and nanoscale structures that protect animals from suffering cold weather or external threats. Herein, we contribute an effective strategy for exploring the hierarchical structure transformation mechanism by stretching a single fiber and bundle fibers. Taking advantage of controllable stretching, the disulfide bonds and peptide chains were taken apart or reconstructed by the new crosslinking bonds inside the wool fiber. If the temperature, solution concentration and stretching velocity were appropriate, the strain was more than 230% and the microstructure transformation of a single fiber underwent α→ β transition, disulfide bond breakage and macromolecule slippage occurred during the tensile process. The transformation mechanism was modeled and experimentally tested in wool bundle fibers after setting, suggesting that the stretching led to the transformation from α helix to β-pleated sheet, the breakage of disulfide bonds and the slippage of microfibrils. The availability of wool fibers provides many opportunities for bio-friendly cellular substrates and biosensor devices.

Protein Conformational Changes in Breast Cancer Sera Using Infrared Spectroscopic Analysis.

Protein structural alterations, including misfolding and aggregation, are a hallmark of several diseases, including cancer. However, the possible clinical application of protein conformational analysis using infrared spectroscopy to detect cancer-associated structural changes in proteins has not been established yet. The present study investigates the applicability of Fourier transform infrared spectroscopy in distinguishing the sera of healthy individuals and breast cancer patients. The cancer-associated alterations in the protein structure were analyzed by fitting the amide I (1600–1700 cm−1) band of experimental curves, as well as by comparing the ratio of the absorbance values at the amide II and amide III bands, assigning those as the infrared spectral signatures. The snapshot of the breast cancer-associated alteration in circulating DNA and RNA was also evaluated by extending the spectral fitting protocol to the complex region of carbohydrates and nucleic acids, 1140–1000 cm−1. The sensitivity and specificity of these signatures, representing the ratio of the α-helix and β-pleated sheet in proteins, were both 90%. Likewise, the ratio of amides II and amide III (I1556/I1295) had a sensitivity and specificity of 100% and 80%, respectively. Thus, infrared spectroscopy can serve as a powerful tool to understand the protein structural alterations besides distinguishing breast cancer and healthy serum samples.

Amyloids: Regulators of Metal Homeostasis in the Synapse.

Conformational changes in amyloidogenic proteins, such as β-amyloid protein, prion proteins, and α-synuclein, play a critical role in the pathogenesis of numerous neurodegenerative diseases, including Alzheimer’s disease, prion disease, and Lewy body disease. The disease-associated proteins possess several common characteristics, including the ability to form amyloid oligomers with β-pleated sheet structure, as well as cytotoxicity, although they differ in amino acid sequence. Interestingly, these amyloidogenic proteins all possess the ability to bind trace metals, can regulate metal homeostasis, and are co-localized at the synapse, where metals are abundantly present. In this review, we discuss the physiological roles of these amyloidogenic proteins in metal homeostasis, and we propose hypothetical models of their pathogenetic role in the neurodegenerative process as the loss of normal metal regulatory functions of amyloidogenic proteins. Notably, these amyloidogenic proteins have the capacity to form Ca2+-permeable pores in membranes, suggestive of a toxic gain of function. Therefore, we focus on their potential role in the disruption of Ca2+ homeostasis in amyloid-associated neurodegenerative diseases.

Functional studies of Plasmodium falciparum putative SURF1 in Saccharomyces cerevisiae.

The mitochondrial electron transport chain (mtETC) of Plasmodium falciparum is an important drug target. Identification and functional validation of putative mitochondrial proteins of the mtETC is critical for drug development. Many of the regulatory subunits and assembly factors of cytochrome c oxidase readily identifiable in humans and yeast are missing in P. falciparum. Here, we describe our efforts to identify and validate the function of putative Pfsurf1, a key assembly factor of complex IV of the mtETC. Multiple sequence alignment of SURF 1/Shy 1 was carried out in Clustal X 2.1. Phylogenetic tree was constructed using "Draw tree" option in Clustal X, and was analyzed using interactive Tree of Life software. To identify the conserved sequences, domain search was done using Jalview version 2.8.2 (BLOSUM 62 scoring). The haploid Saccharomyces cerevisiae strain (BY4741) containing the null allele shy1 (Orf: YGR112w) (shy1::Kan) was complemented with putative Pfsurf1 to study its ability to rescue the growth defect. Similarity searches of PfSURF1-like protein in the Pfam shows statistically significant E = 4.7e-10 match to SURF1 family. Sequence alignment of PfSURF1 with other SURF1-like proteins reveals the conservation of transmembrane domains, α-helices and β-pleated sheets. Phylogenetic analysis clusters putative PfSURF1 with apicomplexan SURF1-like proteins. Yeast complementation studies show that Pfsurf1 can partially rescue the yeast shy1 mutant, YGR112w. Bioinformatics and complementation studies in yeast show that P. falciparum's SURF1 is the functional ortholog of human SURF1 and yeast Shy1.

Fast Screening and Primary Diagnosis of COVID-19 by ATR FT-IR

Background: The outbreak of coronavirus disease 2019 (COVID-19) has led to substantial infections and mortality around the world. Fast screening and diagnosis are thus crucial to quick isolation and clinical intervention. Methods: Patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A/B, and respiratory syncytial virus (RSV), as well as healthy controls, were included in this study. All viral infections were confirmed by reverse transcriptase PCR (RT-PCR). The serum samples were measured by attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR). Multivariate and statistical analysis was performed to differentiate between or among groups. Findings: We found that the most discriminatory bands for COVID-19 vs. control classification were amide I, amide II, and νs(PO2−) in original spectra and centered at 1632, 1545, 1400, 1079, and 1037 cm-1 in the second derivative infrared (SD-IR) spectra. Normal controls, non-severe, and severe COVID-19 patients were well separated by unsupervised methods. ATR FT-IR coupled with partial least square discriminant analysis (PLS-DA) was effective to differentiate COVID-19 from normal controls and other respiratory viral infections with the area under the receiver operating characteristic curve (AUROC) of 0·9866 (95%CI 0·9721-0·9939). Interpretation: The band centered at 1633 cm-1 in the SD-IR spectra is mainly attributed to the β-pleated sheet structure from immunoglobulins. Increases in antibody levels and dysregulation of phospholipids can be derived from the measured spectra. The serum FT-IR spectra exhibited “chemical fingerprints” towards different viral infections.Funding Statement: This work was funded by the National Natural Science Foundation of China (52041701).Declaration of Interests: The authors declare no competing interests.Ethics Approval Statement: This study was approved by the Ethics Committees from TsinghuaUniversity and Peking Union Medical College Hospital.

Civetta to target propeller proteins

The health-care investment firm Deerfield Management has launched a biotech start-up called Civetta Therapeutics with $53 million in series A financing. Civetta will develop small molecules that target β propeller proteins, which get their name from β-pleated amino acid sheets arranged in a circle like a propeller or pinwheel. The Cambridge, Massachusetts–based firm says β propeller proteins are important for protein-protein interactions and are implicated in cancer, metabolic diseases, and neurodegeneration.

Spectroscopy goes viral: Diagnosis of hepatitis B and C virus infection from human sera using ATR-FTIR spectroscopy

The development of a new fast, portable and reagent-free diagnostic technique for hepatitis B (HBV) and hepatitis C (HCV) viruses would be an enormous benefit to society. Here, we evalulate the ability of Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy combined with multivariate data analysis to classify human serum samples based on the presence of HBV and HCV infection. Sera samples were prepared using three different methodologies: i) Sera depsoited onto glass cover slips, airdried and placed onto the ATR crystal. ii) Whole serum dried directly onto the ATR crystal. iii) Serum separated into high and low molecular weight compounds using a filtration approach and the high molecular weight fraction placed directly onto the ATR-FTIR diamond window and dried. For methodology i) the Partial Least Squares Discriminate Analysis (PLS-DA) calibration set included 313 (70 %) samples and the validation set 93 (30 %) samples. For HBV vs control the sensitivity and specificity was found to be 69.4 % and 73.7 % (10 latent variables (LV)), respectively. For HCV vs control the sensitivity and specificity was 51.3 % and 90.9 % (LV 11), respectively. In the second set of experiments the serum samples were dried directly onto the ATR diamond. PLS-DA models were constructed using 144 (70 %) samples for the calibration set and tested using an independent test set containing 62 (30 %) samples. For HBV versus control the sensitivity and the specificity was 84.4 % and 93.1 %, respectively (LV 8). For HCV versus control the sensitivity and specificity was 80.0 % and 97.2 %, respectively (LV 9). For HBV versus HCV the sensitivity and the specificity was 77.4 % and 83.3 %, respectively (LV 5). To increase the sensitivity and specificity serum sample was fractionated into high and low molecular weight components. In PLS-DA cross validated model (LV 8) the sensitivity and specificity was 87.5 % and 94.9 %, respectively for HBV vs control (high molecular concentrate). The PLS-DA cross-validated model (LV 8) for HCV vs control high molecular fraction produced a sensitivity and specificity of 81.6 % and 89.6 %, respectively. No linear correlation was observed for sera samples spiked with known viral loads using Partial Least Squares Regression (PLS-R) modelling.Spectra of positive serum (HBV and HCV) showed a strong band observed at 1631 cm−1, which was absent in the spectra of controls and assigned to the β-pleated sheet protein marker of immunoglobulin (Ig). A band at 1093 cm−1, observed in spectra of HBV infected sera, was assigned to CC and COmodes of polysaccharide N-glycan from hepatitis B surface antigen (HBsAg). The assignment was confirmed by atomic force microsocpy infrared (AFM-IR) spectroscopy of the isolated protein. This band represents a unique marker for HBV infection. In summary, ATR-FTIR spectroscopy is a powerful tool to study blood composition and identify potential disease markers but care must be taken to ensure that the modelling is not biased by inflammation markers, which may confound diagnosis.

Biodegradation of polyhydroxybutyrate by Pseudomonas sp. DSDY0501 and purification and characterization of polyhydroxybutyrate depolymerase.

Strain DSDY0501 with polyhydroxybutyrate (PHB)-degrading ability was isolated from activated sludge. The morphological, physiological, and biochemical properties of the strain and phylogenetic analysis indicated that the strain belongs to Pseudomonas sp. The strain used PHB as the sole carbon source and degraded PHB films completely in 21h in liquid culture. An extracellular PHB depolymerase was purified from the supernatant of the culture by ultrafiltration and Sephacryl S-200 gel filtration. The specific activity of the purified enzyme increased 24.2-fold, and the recovery yield was 16.61%. Extracellular PHB depolymerase, a monomeric enzyme with a molecular weight of approximately 57.9kDa, showed optimum activity at 60°C and pH 9.0, and was stable in the temperature range of 10-60°C and a pH range of 6.0-10.0. The secondary structure of the enzyme contained approximately 60% α-helix and 40% β-pleated sheet according to the circular dichroism spectrum. Mass spectrum analysis showed that the main degradation product of the enzyme was PHB monomer, indicating the exo-type action of this PHB depolymerase.

Effect of extrusion on the structure and antigenicity of soybean β-conglycinin

Abstract β-Conglycinin, the main component of 7S globulin in soybean protein, is also a key soybean antigen protein that causes allergic reactions. Extrusion technologies have received considerable attention as a method for modifying soybean protein allergens. This study investigated the changes in β-conglycinin structure and antigenicity upon extrusion. Isoelectric precipitation, ammonium sulfate precipitation, and sepharose CL-6B gel filtration were used to isolate and purify β-conglycinin from soybean powder, and single-factor and orthogonal tests were used to study the effects of water content, extrusion temperature, screw rotation speed, and feeding speed on the antigenicity of β-conglycinin after extrusion. Fourier transform infrared spectrometry (FTIR) was then employed to analyze the structure of β-conglycinin after extrusion under the optimal conditions determined by the orthogonal test. The results showed that extrusion significantly reduced the antigenicity of β-conglycinin (P feeding speed > screw rotation speed > water content. The optimal conditions were temperature at 130 °C, screw rotation speed at 140 r/min, and feeding speed at 35 g/min. Under these conditions, the contents of α-helix, β-pleated sheet, and β-turn structures in β-conglycinin were significantly reduced (P

FTIR microspectroscopy reveals fatty acid-induced biochemical changes in C. elegans

Fourier transform infrared microspectroscopy (FTIR) is a promising method for the analysis of biological samples. Recent studies reported that FTIR imaging allows determination of the distribution of several biomolecules in a sample with no staining or extraction. In this study, FTIR was used to monitor biochemical changes in C. elegans nematodes cultured in nematode maintenance media (CeMM) without supplementation and with supplementation with either a long chain polyunsatured omega 3 fatty acid, eicosapentaenoic acid (EPA) or a saturated fatty acid, palmitic acid (PA) at 100 μM. EPA is an omega 3 fatty acid with documented health benefits while PA is generally consumed in diets. Worms were placed on BaF2 slides, and FTIR spectra were collected from single worms in transmission mode using a focal plane array detector. Principal component analysis grouped the FTIR spectra into three clusters corresponding to spectra of worms cultured with no supplementation, worms cultured with supplementation with EPA, and worms cultured with supplementation with PA. The major differences between the FTIR spectra reside in the vibrations corresponding to unsaturated fatty acids (3008 cm−1), lipids (2928, 2848, and 1744 cm−1), and proteins (1680, 1648, and 1515 cm−1). This indicates that supplementation with EPA or PA leads to biochemical alterations related to unsaturated fatty acids, lipids, and proteins. Furthermore, supplementing mutant strains (tub-1 and fat-3) CeMM with PA resulted in the appearance of the vibration 3008 cm−1, an increase in the intensity of the vibration 1744 cm−1, and a new vibration at 1632 cm−1, which is assigned to the amide I of β-pleated sheet component of proteins, in the spectra of tub-1 and fat-3 mutant strains. The results illustrated the potential use of FTIR alongside other techniques such as gas chromatography and staining techniques to investigate lipid metabolism and fat accumulation as well as induced changes in protein structures.

Biomechanical properties of fishing lines of the glowworm Arachnocampa luminosa (Diptera; Keroplatidae)

Animals use adhesive secretions in highly diverse ways, such as for settlement, egg anchorage, mating, active or passive defence, etc. One of the most interesting functions is the use of bioadhesives to capture prey, as the bonding has to be performed within milliseconds and often under unfavourable conditions. While much is understood about the adhesive and biomechanical properties of the threads of other hunters such as spiders, barely anything is documented about those of the New Zealand glowworm Arachnocampa luminosa. We analysed tensile properties of the fishing lines of the New Zealand glowworm Arachnocampa luminosa under natural and dry conditions and measured their adhesion energy to different surfaces. The capture system of A. luminosa is highly adapted to the prevailing conditions (13–15 °C, relative humidity of 98%) whereby the wet fishing lines only show a bonding ability at high relative humidity (>80%) with a mean adhesive energy from 20–45 N/m and a stronger adhesion to polar surfaces. Wet threads show a slightly higher breaking strain value than dried threads, whereas the tensile strength of wet threads was much lower. The analyses show that breaking stress and strain values in Arachnocampa luminosa were very low in comparison to related Arachnocampa species and spider silk threads but exhibit much higher adhesion energy values. While the mechanical differences between the threads of various Arachnocampa species might be consequence of the different sampling and handling of the threads prior to the tests, differences to spiders could be explained by habitat differences and differences in the material ultrastructure. Orb web spiders produce viscid silk consisting of β-pleated sheets, whereas Arachnocampa has cross-β–sheet crystallites within its silk. As a functional explanation, the low tear strength for A. luminosa comprises a safety mechanism and ensures the entire nest is not pulled down by prey which is too heavy.

HDAC2 dysregulation in the nucleus basalis of Meynert during the progression of Alzheimer's disease.

Alzheimer's disease (AD) is characterized by degeneration of cholinergic basal forebrain (CBF) neurons in the nucleus basalis of Meynert (nbM), which provides the major cholinergic input to the cortical mantle and is related to cognitive decline in patients with AD. Cortical histone deacetylase (HDAC) dysregulation has been associated with neuronal degeneration during AD progression. However, whether HDAC alterations play a role in CBF degeneration during AD onset is unknown. We investigated global HDAC protein levels and nuclear HDAC2 immunoreactivity in tissue containing the nbM, changes and their association with neurofibrillary tangles (NFTs) during the progression of AD. We used semi-quantitative western blotting and immunohistochemistry to evaluate HDAC and sirtuin (SIRT) levels in individuals that died with a premortem clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment (MCI), mild/moderate AD (mAD) or severe AD (sAD). Quantitative immunohistochemistry was used to identify HDAC2 protein levels in individual cholinergic nbM nuclei and their colocalization with the early phosphorylated tau marker AT8, the late-stage apoptotic tau marker TauC3 and Thioflavin-S, amarker of β-pleated sheet structures in NFTs. In AD patients, HDAC2 protein levels were dysregulated in the basal forebrain region containing cholinergic neurons of the nbM. HDAC2 nuclear immunoreactivity was reduced in individual cholinergic nbM neurons across disease stages. HDAC2 nuclear reactivity correlated with multiple cognitive domains and with NFT formation. These findings suggest that HDAC2 dysregulation contributes to cholinergic nbM neuronal dysfunction, NFT pathology, and cognitive decline during clinical progression of AD.