β-Amyloid (1-42), human

β-Amyloid (1-42) (Amyloid β-peptide (1-42)), human, a 42-amino acid peptide that has not been treated with HFIP, is a brain-penetrant amyloid protein fragment, which can be used in research on Alzheimer's disease and Down’s syndrome. β-Amyloid (1-42), human remaining as a monomer exhibits antioxidant and neuroprotective effects. β-Amyloid (1-42), human, after being monomericized by HFIP and dissolved in DMSO to form the stock solution, on the one hand, can form soluble oligomers (AβOs) when incubated at 4 ℃, which have synaptic toxicity and neurotoxicity; on the other hand, it can be incubated at 37 ℃ to form insoluble fibrils, with lower neurotoxicity, and participating in the oxidative damage process. Aβ42 oligomers bind to various neuronal surface receptors (such as PrPc, mGluR5, NMDA receptors, etc.), triggering oxidative stress, calcium homeostasis imbalance, and synaptic toxicity via activating downstream signaling pathways, leading to neuronal dysfunction and death^{[1][1][2][3][4][5][6][7]}. In Vitro:β-Amyloid Aggregation Guidelines (Following is our recommended protocol. This protocol only provides a guideline, and should be modified according to your specific needs of your downstream experimental schemes).
Monomerization (HFIP-treated):
1. Solid Aβ peptide is dissolved in cold hexafluoro-2-propanol (HFIP). The peptide is incubated at room temperature for at least 1 h to establish monomerization and randomization of structure.
2. Conduct vacuum drying to remove all of HFIP, and the resulting peptide is stored as a film at -20°C or -80°C.
Oligomer preparation
3. The resulting film is dissolved in anhydrous DMSO/0.1M NaOH/1% ammonia solution at 5 mM. Then, dilute it with sterile double-distilled water to a certain concentration (eg: 200 μM) and ensure complete dissolution.
4. Next, the solution is age 24-48 h at 4-8°C. The sample is then centrifuged at 14000g for 10 min at 4-8°C; the soluble oligomers are in the supernatant. The supernatant is diluted 10-200-fold for experiments.
Fiber preparation:
3. The resulting film is dissolved in anhydrous DMSO at 5 mM and then dilutes into the appropriate concentration and buffer (10 mM HCl) with vortexing.
4. Next, the solution is age 24-48 h at 37°C to obtain Aβ42 fibrils.
Note:
1) When performing step 1, if there is a small amount of insoluble matter, the HFIP treatment time can be extended (such as overnight incubation), vortexing, or short-term ultrasound can be used; if there is still a small amount of insoluble matter, it is recommended to remove it by centrifugation or filtration.
2) When performing step 2, if vacuum drying conditions are not available, nitrogen blowing can be attempted. Freeze-drying or natural evaporation in a fume hood is not recommended.
3) If using PBS for dilution, it may cause the precipitation of the polypeptide.
4) The aggregation form is unstable in the solution, it is recommended to prepare and use it immediately. If storage is required, it is recommended to store the peptides in a film form at -20°C or -80°C.

β-Amyloid (1-42), human TFA is prepared into oligomers, exhibiting neurotoxicity:
β-amyloid (1–42) peptide (60-180 μM, 48 h) could form oligomers significantly faster than Aβ40 and Aβ43 and Aβ42 oligomers (1-1000 μg/mL, 48 h) showed the greatest level of neurotoxicity in both SH-SY5Y and PC12 cells^[10].
Aβ42 oligomers (20 μM, 0-48 h) induces both apoptosis and autophagy in SH-SY5Y cells but only autophagy in U87 cells^[11].
Aβ42 oligomers (0.5 μM, 1 h) induces intracellular Ca²⁺ influx, mitochondrial reactive oxygen species (ROS) production and increases cell death in mouse neuroblastoma N2a cells^[12].
In Vivo:Note:
Please do not refer to only one article to determine the experimental conditions. It is recommended to determine the optimal experimental conditions (animal strain, age, dosage, frequency and cycle, detection time and indicators, etc.) through preliminary experiments before the formal experiment.

β-Amyloid (1-42), human TFA can be used in animal modeling to construct Alzheimer's disease models.