Insoluble Peptides Research Articles

Melatonin Supplementation Alleviates Impaired Spatial Memory by Influencing Aβ1-42 Metabolism via γ-Secretase in the icvAβ1-42 Rat Model with Pinealectomy

In the search for Alzheimer’s disease (AD) therapies, most animal models focus on familial AD, which accounts for a small fraction of cases. The majority of AD cases arise from stress factors, such as oxidative stress, leading to neurological changes (sporadic AD). Early in AD progression, dysfunction in γ-secretase causes the formation of insoluble Aβ1-42 peptides, which aggregate into senile plaques, triggering neurodegeneration, cognitive decline, and circadian rhythm disturbances. To better model sporadic AD, we used a new AD rat model induced by intracerebroventricular administration of Aβ1-42 oligomers (icvAβ1-42) combined with melatonin deficiency via pinealectomy (pin). We validated this model by assessing spatial memory using the radial arm maze test and measuring Aβ1-42 and γ-secretase levels in the frontal cortex and hippocampus with ELISA. The icvAβ1-42 + pin model experienced impaired spatial memory and increased Aβ1-42 and γ-secretase levels in the frontal cortex and hippocampus, effects not seen with either icvAβ1-42 or the pin alone. Chronic melatonin treatment reversed memory deficits and reduced Aβ1-42 and γ-secretase levels in both structures. Our findings suggest that our icvAβ1-42 + pin model is extremely valuable for future AD research.

Influence of Soy Protein Hydrolysates on Thermo-Mechanical Properties of Gluten-Free Flour and Muffin Quality

The influence of protease-assisted hydrolysis on the impact exerted by the soy protein isolate on the thermo-mechanical behavior and baking performance of the gluten-free composite flour, consisting of a mixture of rice and quinoa flours, was investigated. The mPAGE analysis revealed that soluble fractions of the hydrolysates, obtained with bromelain, Neutrase or trypsin, concentrated the peptides with a molecular weight lower than 20 kDa, whereas the insoluble ones retained higher molecular weight fragments. The influence of the separate and cumulative addition of the soluble and insoluble soy peptide fractions on the thermo-mechanical properties of dough was tested by means of a Mixolab device. Regardless of the enzyme used for hydrolysis, the addition of the soluble peptide fraction to the gluten-free composite flour resulted in delayed starch gelatinization, whereas the insoluble one caused a considerable increase in the dough consistency. The most important improvements in the dough behavior were observed when supplementing the gluten-free flour with 10% soy protein hydrolysates obtained with bromelain and trypsin. The gluten-free muffins enriched in soy protein hydrolysate exhibited important differences in terms of moisture, height and specific volume, compared to the control. Moreover, the ABTS- and DPPH-based methods indicated that protein hydrolysate addition caused a significant improvement in the antioxidant activity (by at least 38% and 23%, respectively) compared to the control. In conclusion, soy protein hydrolysate might be successfully used for increasing both the protein content and the antioxidant activity of the muffin samples.

7,8-Dihydroxy Efavirenz Is Not as Effective in CYP46A1 Activation In Vivo as Efavirenz or Its 8,14-Dihydroxy Metabolite.

High dose (S)-efavirenz (EFV) inhibits the HIV reverse transcriptase enzyme and is used to lower HIV load. Low-dose EFV allosterically activates CYP46A1, the key enzyme for cholesterol elimination from the brain, and is investigated as a potential treatment for Alzheimer's disease. Simultaneously, we evaluate EFV dihydroxymetabolites for in vivo brain effects to compare with those of (S)-EFV. We have already tested (rac)-8,14dihydroxy EFV on 5XFAD mice, a model of Alzheimer's disease. Herein, we treated 5XFAD mice with (rac)-7,8dihydroxy EFV. In both sexes, the treatment modestly activated CYP46A1 in the brain and increased brain content of acetyl-CoA and acetylcholine. Male mice also showed a decrease in the brain levels of insoluble amyloid β40 peptides. However, the treatment had no effect on animal performance in different memory tasks. Thus, the overall brain effects of (rac)-7,8dihydroxy EFV were weaker than those of EFV and (rac)-8,14dihydroxy EFV and did not lead to cognitive improvements as were seen in treatments with EFV and (rac)-8,14dihydroxy EFV. An in vitro study assessing CYP46A1 activation in co-incubations with EFV and (rac)-7,8dihydroxy EFV or (rac)-8,14dihydroxy EFV was carried out and provided insight into the compound doses and ratios that could be used for in vivo co-treatments with EFV and its dihydroxymetabolite.

Properties of Heat-Assisted pH Shifting and Compounded Chitosan from Insoluble Rice Peptide Precipitate and Its Application in the Curcumin-Loaded Pickering Emulsions.

Curcumin exhibits antioxidant and antitumor properties, but its poor chemical stability limits its application. Insoluble peptide precipitates formed by proteolysis of rice glutelin are usually discarded, resulting in resource waste. The coupled treatment of heat-assisted pH shifting and compounded chitosan (CS) was used to fabricate rice peptide aggregate-chitosan complexes (RPA-CS). The structure, interfacial behavior, emulsion properties, and digestibility of curcumin-loaded RPA-CS Pickering emulsions were investigated. Increasing the CS concentration led to lower interfacial tension but larger particle size, and the three-phase contact angle of the RPA-CS complexes approached 90°. Quartz crystal microbalance with dissipation (QCM-D) indicated that RPA-CS complexes with 6 g·kg-1 of CS (RPA-CS6) had the highest K1 (0.592 × 106 Hz-1) and K4 (0.487 × 106 Hz-1), suggesting that the softest interfacial layers were formed. The solid-liquid balance of RPA-RPA-CS emulsions was lower than 0.5, declaring that they had more elastic behavior than that of RPA emulsions. RPA-RPA-CS4-and RPA-CS6 emulsions had better storage stability, lower FFA release (79.8% and 76.3%, respectively), and higher curcumin bioaccessibility (65.2% and 68.2%, respectively) than RPA emulsions. This study showed that a low-value insoluble rice peptide precipitate could be used as a valuable emulsifier in foods, which may increase the economics and sustainability of the food supply.

PeptideBERT: A Language Model Based on Transformers for Peptide Property Prediction.

Recent advances in language models have enabled the protein modeling community with a powerful tool that uses transformers to represent protein sequences as text. This breakthrough enables a sequence-to-property prediction for peptides without relying on explicit structural data. Inspired by the recent progress in the field of large language models, we present PeptideBERT, a protein language model specifically tailored for predicting essential peptide properties such as hemolysis, solubility, and nonfouling. The PeptideBERT utilizes the ProtBERT pretrained transformer model with 12 attention heads and 12 hidden layers. Through fine-tuning the pretrained model for the three downstream tasks, our model is state of the art (SOTA) in predicting hemolysis, which is crucial for determining a peptide's potential to induce red blood cells as well as nonfouling properties. Leveraging primarily shorter sequences and a data set with negative samples predominantly associated with insoluble peptides, our model showcases remarkable performance.

Determining the Sequence Dependency of Self-Assembly of Elastin-Like Peptides Using Short Peptide Analogues with Shuffled Repetitive Sequences.

Synthetic elastin-like peptides (ELPs) that possess characteristic tropoelastin-derived hydrophobic repetitive sequences, such as (VPGVG)n, exhibit thermoresponsive reversible self-assembly. Although their thermoresponsive properties have been well-studied, the sequence-dependent and structural requirements for self-assembly remain ambiguous. In particular, it is still unclear whether the amino acid sequences derived from tropoelastin are necessary for self-assembly. In this study, 11 sequence-shuffled ELP analogues based on (FPGVG)5, which is a previously developed short ELP (sELP), were designed to elucidate the sequence-dependent and structural requirements for their self-assembly. Among them, eight shuffled peptides exhibited self-assembling properties, whereas the other three peptides were difficult to dissolve in water. Structural analyses revealed that the structural characteristics of the three insoluble peptides were different from those of their thermoresponsive analogues. Furthermore, the secondary structures of the peptide analogues possessing the self-assembly abilities were different from each other. These results suggest that the potential for self-assembly and water solubility of sELPs depend on the primary structure in each repeated unit. Moreover, several shuffled analogues exhibited more potent self-assembling properties than the original (FPGVG)5, indicating that shorter ELPs can be obtained using their novel motifs as repetitive units. We also observed that the presence of Pro-Gly sequence in the repeating units was advantageous in terms of peptide solubility. Although further analysis will be necessary to elucidate the molecular mechanism underlying the self-assembly of these sELPs, this study provides insights into the relationship between the amino acid sequence and the self-assembling ability of the peptides for developing new sELPs for various applications.

Size exclusion chromatography to evaluate in vitro proteolysis: A case study on the impact of microstructure in pulse powders.

Cellular pulse ingredients are increasingly being studied but little knowledge on their proteolysis patterns upon digestion is available. This study investigated a size exclusion chromatography (SEC) approach to study in vitro protein digestion in chickpea and lentil powders, providing novel insights into proteolysis kinetics and the evolution of molecular weight distributions in the (solubilized) supernatant and (non-solubilized) pellet fractions. For the quantification of proteolysis, SEC-based analysis was compared to the commonly used OPA (o-phthaldialdehyde) approach and nitrogen solubilized upon digestion, leading to highly correlated proteolysis kinetics. Generally, all approaches confirmed that microstructure dictated proteolysis kinetics. However, SEC analysis delivered an additional level of molecular insight. For the first time, SEC revealed that while bioaccessible fractions reached a plateau in the small intestinal phase (around 45-60min), proteolysis continued in the pellet, forming smaller but mostly insoluble peptides. SEC elutograms showed pulse-specific proteolysis patterns, unidentified using other current state-of-the-art methods.

The human RAP1 and GFAPɛ proteins increase γ-secretase activity in a yeast model system.

Alzheimer's disease (AD) is an age-related disorder that results in progressive cognitive impairment and memory loss. Deposition of amyloid β (Aβ) peptides in senile plaques is a hallmark of AD. γ-secretase produces Aβ peptides, mostly as the soluble Aβ40 with fewer insoluble Aβ42 peptides. Rare, early-onset AD (EOAD) occurs in individuals under 60 years of age. Most EOAD cases are due to unknown genetic causes, but a subset is due to mutations in the genes encoding the amyloid precursor protein that is processed into Aβ peptides or the presenilins (PS1 and PS2) that process APP. PS1 interacts with the epsilon isoform of glial fibrillary acidic protein (GFAPɛ), a protein found in the subventricular zone of the brain. We have found that GFAPɛ interacts with the telomere protection factor RAP1 (TERF2IP). RAP1 can also interact with PS1 alone or with GFAPɛ in vitro. Our data show that the nuclear protein RAP1 has an extratelomeric role in the cytoplasm through its interactions with GFAPɛ and PS1. GFAPɛ coprecipitated with RAP1 from human cell extracts. RAP1, GFAPɛ, and PS1 all colocalized in human SH-SY5Y cells. Using a genetic model of the γ-secretase complex in Saccharomyces cerevisiae, RAP1 increased γ-secretase activity, and this was potentiated by GFAPɛ. Our studies are the first to connect RAP1 with an age-related disorder.

Towards absolute quantification of protein genetic variants in Pisum sativum extracts

In recent years, several studies have used proteomics approaches to characterize genetic variant profiles of agricultural raw materials. In such studies, the challenge is the quantification of the individual protein variants. In this study a novel UPLC-PDA-MS method with absolute and label-free UV-based peptide quantification was applied to quantify the genetic variants of legumin, vicilin and albumins in pea extracts. The aim was to investigate the applicability of this method and to identify challenges in determining protein concentration from the measured peptide concentrations. Analysis of the protein mass balance showed significant losses of proteins in extraction (37%) and of peptides in further sample preparation (69%). The challenge in calculating the extractable individual protein concentrations was how to deal with these insoluble peptides. The quantification approach using average amino acid concentrations in each position of the sequence showed most reproducible results and allowed comparison of the genetic protein composition of 8 different cultivars. The extractable protein composition (μM/μM) was remarkably similar for all cultivar extracts and consisted of legumins A1 (12.8 ± 1.2%), A2 (1.1 ± 0.4%), B (9.9 ± 1.6%), J (7.5 ± 1.0%) and K (10.3 ± 2.1%), vicilin (15.2 ± 1.7%), provicilin (15.7 ± 2.5%), convicilin (9.8 ± 0.8%), albumin A1 (7.4 ± 2.0%), albumin 2 (10.0 ± 1.5%) and protease inhibitor (0.4 ± 0.4%).

Phytochemical Compounds and Nanoparticles as Phytochemical Delivery Systems for Alzheimer's Disease Management.

Alzheimer's disease remains one of the most widespread neurodegenerative reasons for dementia worldwide and is associated with considerable mortality and morbidity. Therefore, it has been considered a priority for research. Indeed, several risk factors are involved in the complexity of the therapeutic ways of this pathology, including age, traumatic brain injury, genetics, exposure to aluminum, infections, diabetes, vascular diseases, hypertension, dyslipidemia, and obesity. The pathophysiology of Alzheimer's disease is mostly associated with hyperphosphorylated protein in the neuronal cytoplasm and extracellular plaques of the insoluble β-amyloid peptide. Therefore, the management of this pathology needs the screening of drugs targeting different pathological levels, such as acetylcholinesterase (AchE), amyloid β formation, and lipoxygenase inhibitors. Among the pharmacological strategies used for the management of Alzheimer's disease, natural drugs are considered a promising therapeutic strategy. Indeed, bioactive compounds isolated from different natural sources exhibit important anti-Alzheimer effects by their effectiveness in promoting neuroplasticity and protecting against neurodegeneration as well as neuroinflammation and oxidative stress in the brain. These effects involve different sub-cellular, cellular, and/or molecular mechanisms, such as the inhibition of acetylcholinesterase (AchE), the modulation of signaling pathways, and the inhibition of oxidative stress. Moreover, some nanoparticles were recently used as phytochemical delivery systems to improve the effects of phytochemical compounds against Alzheimer's disease. Therefore, the present work aims to provide a comprehensive overview of the key advances concerning nano-drug delivery applications of phytochemicals for Alzheimer's disease management.

Genetic Analysis of K-Casein Gene in Milk Protein of Bos Indicus Cattle

Purpose: Κ-casein, or kappa casein, is a mammalian milk protein involved in several important physiological processes. Chymosin splits K-casein into an insoluble peptide (para kappa-casein) and a water-soluble glycomacropeptide (GMP). GMP is responsible for increased efficiency of digestion, prevention of neonate hypersensitivity to ingested proteins, and inhibition of gastric pathogens. The gene underlying the production of kappa-casein in cow's Milk shows polymorphisms which affect the amount of protein produced. Higher levels of kappa-casein are associated with increased milk protein and casein content and better cheese yield. Method: The current study aimed to identify the genetic mutations among three indigenous cattle breeds of Sindh, Pakistan. A particular set of primers amplified the targeted area of the K-CASEIN gene after genomic DNA extraction from blood samples of the three cattle breeds, namely Cholistani cattle breed, Tharri, and Sahiwal. Findings: The amplified PCR products were sequenced using the ABI Genetic Analyzer 3500; a BioEdit version 7.2 was used to examine the sequencing data. Using the ensemble gene browser, blast analysis was also performed. Practical Implication: Results revealed 18 mutations in all 03 cattle breeds, including 07 mutations in the Cholistani cattle breed; the Tharri cattle breeds had 06 mutations, and the Sahiwal cattle breeds had 05 mutations. Results of this study of the K-CASEIN gene suggested that Cholistani cattle breeds are more genetically varied than the Sahiwal cattle breeds. Conclusion: Furthermore, the Sahiwal cattle breed is more diverse than the Thari cattle breed for the said gene. Keywords: K-Casein gene, Sahiwal cattle breed, Thari cattle breed, Cholistani cattle breed, Polymorphism

Formation, texture, and stability of yolk-free mayonnaise: Effect of soy peptide aggregates concentration

A kind of yolk-free mayonnaise (YFM) with preferable quality was prepared by insoluble soy peptide aggregates (ISPA) in present work. The basic properties, rheology, texture, sensory quality, and stability for YFM with different concentration of ISPA were explored. As ISPA concentration increased from 1.50 wt% to 3.00 wt%, the droplet size of YFM decreased by 5.35 μm, while the storage and loss modulus increased 2.02 and 1.99 times, moreover, the thixotropic recovery percentage, hardness and gumminess of YFM increased to 95.84 %, 13.29 g and 10.05, respectively. Meanwhile, the ISPA concentration had positive effect on the oxidation stability and thermal stability for YFM. Noticeably, YFM with 2.75 wt% ISPA had good textural properties and sensory quality, which were close to those of commercial mayonnaise. In conclusion, YFM prepared by ISPA had low cholesterol level, which provided a new strategy for solving the health problems of traditional mayonnaise.

From clinical phenotype to proteinopathy: molecular neuroimaging in neurodegenerative dementias.

Neurodegenerative dementias are characterized by the abnormal accumulation of misfolded proteins. However, its diagnostic criteria are still based on the clinical phenotype. The development of biomarkers allowed in vivo detection of pathophysiological processes. This article aims to make a non-systematic review of the use of molecular neuroimaging as a biomarker. Molecular neuroimaging is based on the use of radiotracers for image acquisition. The radiotracer most used in PET is 18F-fluorodeoxyglucose (FDG), with which it is possible to study the regional brain glucose metabolism. The pattern of regional hypometabolism provides neuroanatomical information on the neurodegenerative process, which, in turn, has a good specificity for each type of proteinopathy. FDG is very useful in the differential diagnosis of neurodegenerative dementias through the regional pattern of involvement, including dementia with Lewy bodies and the spectrum of frontotemporal dementia. More recently, radiotracers with specific ligands to some of the pathological proteins have been developed. Pittsburgh compound B (PIB) labeled with 11C and the ligands that use 18F (florbetapir, florbetaben and flutemetamol) are the most used radiotracers for the detection of insoluble β-amyloid peptide in Alzheimer's disease (AD). A first generation of ligands for tau protein has been developed, but it has some affinity for other non-tau protein aggregates. A second generation has the advantage of having a higher affinity for hyperphosphorylated tau protein, including in primary tauopathies.

Formation and stability of Pickering emulsion gels by insoluble soy peptide aggregates through hydrophobic modification

In this work, a highly stable food-grade Pickering emulsion gels was successfully prepared by hydrophobically modified insoluble soybean peptide aggregates. The relationships between the surface properties of insoluble soybean peptide aggregates and Pickering emulsion gels characteristics were clarified. After modification, the insoluble soybean peptide aggregates with high surface hydrophobicity had small particle size (377 nm), near-neutral wettability (θo/w = 92°) and strong interfacial adsorption capability. These allowed the modified insoluble soybean peptide aggregates to stabilize the oil-water interface and form continuous network surrounding oil droplets, leading to the formation of stable Pickering emulsion gels. Besides, Pickering emulsion gels prepared by insoluble soybean peptide aggregates with higher surface hydrophobicity had smaller droplet size and higher gel strength, and remained stable even after 60 days of storage. The findings suggest a preferable plant protein particle for the preparation of stable Pickering emulsion gels in food industry.

A Potential Notion on Alzheimer’s Disease: Nanotechnology as an Alternative Solution

Alzheimer’s disease is an eventually destroying disease of the overaged people featured by the dynamic and gradual brain erosion because of construction of extracellular plaques in the hippocampus. It is an undertreated and underrecognized disease that is becoming a major public health concern. From the study, it is known that production of plaques takes place twenty years back, before the commencement of clinical syndromes. As per report, in 2019, above 50 million people got into Alzheimer’s disease. Recent developments include improved clinical diagnostic guidelines and improved treatment of both cognitive disturbance and behavioral problems. Treatment majorly focus on cholinergic therapy has been clinically evaluated by different studies including randomized, double‐blind, placebo‐controlled, parallel‐group studies measuring performance‐based tests of cognitive function, activities of daily living, and behavior. The presence of extracellular plaques of insoluble β‐amyloid peptide (Aβ) and neurofibrillary tangles (NFT) containing hyperphosphorylated tau protein (P‐tau) in the neuronal cytoplasm is a remarkable pathophysiological cause in patients’ brains. The graph of increasing patients, suffering from Alzheimer’s disease, is being ascended. The outcome of this turn into fatal, deadly situation. So, there is a possibility of breaking down world economics and human strength. There is a different kind of organic as well as inorganic nanocomponent group, those have been pursued with satisfaction. By studying and researching over pathogenesis specifically, diagnosis of this AD as per its symptoms is possibly done. Treatment of this neurodisease is under processing. The experts are playing an extremely appreciable role for displacing this disease completely. The present review summarizes the pathophysiology and role of the nanoparticle in the diagnosis and treatment of AD.

PH-shifting formation of goat milk casein nanoparticles from insoluble peptide aggregates and encapsulation of curcumin for enhanced dispersibility and bioactivity

The insoluble peptide aggregates formed by proteolysis are usually discarded by food industries, which results in significant wastage of resources and burden on the related industries. In the present study, insoluble peptide aggregates formed during enzymatic hydrolysis of goat milk casein protein (GCA) were used to prepare goat milk casein nanoparticles (GCP) using a controlled pH-shifting treatment. Next, hydrophobic curcumin (Cur) was embedded in the GCP core, and nano-scale stable hydrophilic particles (GCP-Cur) were successfully prepared. The XRD and FT-TR spectroscopy results showed that the Cur was successfully encapsulated in GCP nanoparticles in an amorphous form, and Cur loading does not cause conformational changes. The morphological results also verified the successful design of the GCP-Cur nanoparticles. Furthermore, the GCP-Cur nanoparticles significantly improved the water solubility, storage stability, in vitro bioaccessibility, and antioxidant activity of Cur. Moreover, the anti-gastric digestion properties of GCP-Cur nanoparticles could control the effective release of Cur from the composite particles into the intestine, and can thus be used as a potential delivery carrier for biologically activity. This research provides theoretical and technical guidance for the development and high-value application of these low-value peptide byproducts.

At the origin of Aβ with ADAM10

Alzheimer's Disease Intracellular accumulation of insoluble amyloid β peptide (Aβ) oligomers is a major pathogenic event in Alzheimer's disease (AD). Cleavage of amyloid precursor protein (APP) by β- and γ-secretases generates insoluble Aβ peptides. On the contrary, α-secretase cleaves APP to form sAPPα, a soluble, neuroprotective fragment. ADAM10, a major α-secretase, is thought to play a role in AD; however, the mechanisms mediating ADAM10 modulation are unclear. Nakamura et al. now show that an ADAM10 inhibitor called RECK is increased in human AD brain samples. The authors found that RECK is controlled by glycerophosphodiester phosphodiesterase 2, and ablation of this enzyme or RECK elevation in mice promotes insoluble Aβ oligomer formation and accelerates AD pathology. Targeting this pathway might reduce Aβ pathology in AD. Sci. Transl. Med. 13 , eabe6178 (2021).

PH-Driven formation of soy peptide nanoparticles from insoluble peptide aggregates and their application for hydrophobic active cargo delivery

The insoluble soy peptide aggregates formed upon proteolysis are generally considered as “ready to be discarded”, which placed additional burden on related industries. In this study, with the aim of promoting sustainable utilization of these large aggregates, novel soy peptide-based nanoparticles (SPN) were successfully fabricated from these aggregates via a controlled pH-shifting method, and the obtained SPN exhibited good storage stability and antioxidant activity. Furthermore, the pH-shifting process also provided a driven force for loading and delivering curcumin, which significantly improved its water solubility (up to 105 folds), storage and simulated gastric-intestinal digestive stability, as well as in vitro bioavailability and antioxidant activity. These results indicated that controlled pH-shifting could be an effective and facile method to trigger the assembly of insoluble aggregates into functional peptide nanoparticles for the delivery of bioactive cargoes, which provided a new strategy for the sustainable and high-value application of these low-value peptide byproducts.

Unexpected Trends in Copper Removal from Aβ Peptide: When Less Ligand Is Better and Zn Helps.

Cu, Zn, and amyloid-β (Aβ) peptides play an important role in the etiology of Alzheimer's disease (AD). Their interaction indeed modifies the self-assembly propensity of the peptide that is at the origin of the deposition of insoluble peptide aggregates in the amyloid plaque, a hallmark found in AD brains. Another even more important fallout of the Cu binding to Aβ peptide is the formation of reactive oxygen species (ROS) that contributes to the overall oxidative stress detected in the disease and is due to the redox ability of the Cu ions. Many therapeutic approaches are currently developed to aid fighting against AD, one of them targeting the redox-active Cu ions. Along this research line, we report in the present article the use of a phenanthroline-based peptide-like ligand (L), which is able to withdraw Cu from Aβ and redox-silence it in a very stable 4N Cu(II) binding site even in the presence of Zn(II). In addition and in contrast to what is usually observed, the presence of excess of L lessens the searched effect of ROS production prevention, but it is counterbalanced by the co-presence of Zn(II). To explain such unprecedented trends, we proposed a mechanism that involves the redox reaction between Cu(II)L and Cu(I)L2. We thus illustrated (i) how speciation and redox chemistry can weaken the effect of a ligand that would have appeared perfectly suitable if only tested in a 1:1 ratio and on CuAβ and (ii) how Zn overcomes the undesired lessening of ROS arrest due to excess of ligand. In brief, we have shown how working in biologically relevant conditions is important for the understanding of all of the reactions at play and this must be taken into consideration for the further rational design of ligands aiming to become drug candidates.

Characterization of monomeric and soluble aggregated Aβ in Down’s syndrome and Alzheimer’s disease brains

AbstractBackgroundAlzheimer’s disease (AD) is the most common form of dementia and is characterized by the two hallmarks, amyloid plaques and neurofibrillary tangles in the brain. The plaques consist of aggregated beta amyloid (Aβ) peptides, formed by proteolytic cleavages of amyloid precursor protein (APP). Down’s syndrome (DS) is a genetic disease with an extra copy of chromosome 21, harbouring the APP gene. DS individuals are at increased risk to develop amyloid pathology. Most DS have substantial amyloid pathology at their 40s, with clinical signs of deterioration before the age of 60. Our aim was to compare the Aβ peptide pattern in DS and AD brains, to better understand the difference between them.MethodsImmunoprecipitation (IP) in combination with mass spectrometry was used to identify both soluble and insoluble Aβ peptides, as well as to characterise the composition of Aβ oligomers/protofibrils. Two different antibody combinations were used; 6E10+4G8 to identify total Aβ peptide contents and the Aβ protofibril selective antibody mAb158 to identify the Aβ peptides present in oligomers/protofibrils. Before IP, cortical tissue from patients with DS (with amyloid pathology), sporadic AD and controls were homogenized and fractionated into TBS (TBS soluble) and formic acid (insoluble) fractions.ResultsFrom IP with 6E10+4G8 several truncated Aβ peptides were identified in all groups, including: 1‐X, 2‐X, 3‐X, 4‐X, 5‐X, 11‐X and –X to 15 as well as post‐translationally modified peptides with oxidation and pyroglutamation. Similarities were observed when comparing the Aβ peptide processing in AD and DS, with the exception of –X to 15 Aβ peptides for which the pattern is different. By using mAb158, Aβ1‐40, Aβ1‐42 and Aβ4‐42 were identified. Higher relative AβX‐42 signals were obtained compared to samples IP’d with 6E10+4G8, indicating that the protofibrils/oligomers were enriched with peptides ending at aa42.ConclusionAll Aβ peptides found in AD are also present in DS (with amyloid pathology) indicating a generally similar pathway of Aβ peptide production, apart from –X to 15. Likewise, the Aβ peptides forming protofibrils/oligomers in both AD and DS were similar, implying the possibility to exploit the potential utility of a treatment with clinical benefit in sporadic AD for subjects with DS.