[Arg3]-Amyloid β-Protein (1–40), also described as E3R Aβ40, is an engineered human amyloid-β 1–40 analog in which the native glutamate at position 3 is replaced by arginine.

This substitution introduces a substantial charge change near the N-terminus while preserving the hydrophobic C-terminal region of Aβ40. E3R Aβ40 is particularly useful for investigating the relationship between primary sequence, early-stage aggregation, prefibrillar assemblies and amyloid-associated biological effects.

Unlike disease-associated variants such as E22G Arctic or E22Q Dutch Aβ, E3R is best considered a mechanistic research analog rather than a naturally occurring familial Alzheimer’s disease mutation.

Product Information

The calculated molecular formula and molecular weight are consistent with independently cataloged [Arg3]-Aβ1–40 reference material.

What Does the E3R Substitution Change?

Native human Aβ40 begins:

DAEFR...

The E3R analog begins:

DARFR...

Replacing the negatively charged glutamate at residue 3 with positively charged arginine changes local electrostatics without altering peptide length or the strongly hydrophobic C-terminal segment.

This makes E3R Aβ40 useful for studying how a relatively small sequence change can redirect an amyloid assembly pathway without necessarily producing a major change in the overall rate of mature fibril formation.

Prefibrillar Aggregation Rather Than Simply Faster Fibrillation

The original characterization of E3R Aβ40 provides an important distinction.

Under the reported in vitro conditions, wild-type Aβ40 and E3R Aβ40 showed similar overall aggregation-rate constants:

Wild-type Aβ40: 0.034 ± 0.01 min⁻¹

E3R Aβ40: 0.037 ± 0.01 min⁻¹

However, wild-type Aβ40 showed a clear lag phase, whereas E3R Aβ40 did not. Electron microscopy also revealed a greater population of prefibrillar and disordered species in the E3R samples before mature fibrils became dominant.

This is why We think E3R Aβ40 is more useful as a model of aggregation-pathway redistribution than as a simple “high-aggregation Aβ40” peptide.

Relationship Between Prefibrillar Species and Biological Effects

In the same study, expression of E3R Aβ40 in Drosophila melanogaster neurons reduced median survival by approximately 30% relative to wild-type Aβ40-expressing flies.

The authors found that the E3R variant generated more oligomeric and disordered prefibrillar assemblies relative to well-defined mature fibrils. These observations supported a relationship between the population of early aggregation intermediates and the observed biological phenotype in that experimental model.

The result should not be generalized to every biological system, but it makes E3R Aβ40 a useful sequence-defined tool for studying the distinction between fibril formation and prefibrillar aggregate formation.

Research Applications

[Arg3]-Aβ40 can support studies of amyloid aggregation kinetics, oligomer and prefibrillar assembly, fibril morphology, sequence-dependent toxicity, peptide–membrane interaction and Aβ structure–activity relationships.

It is particularly useful when paired with wild-type human Aβ40 to investigate whether changes in biological behavior are associated with altered aggregate populations rather than simply increased mature fibril formation.

The peptide can also complement studies using disease-associated Aβ variants such as E22G Arctic and E22Q Dutch peptides, although these variants represent different biological questions.

Selecting the Correct Comparator

For an E3R-focused experiment, wild-type human Aβ40 is the most appropriate primary comparator.

Both materials should ideally use matched purity, terminal chemistry, concentration, reconstitution method and incubation conditions.

Using Aβ42 as the only control introduces the additional Ile41-Ala42 C-terminal extension, while using E22G or E22Q introduces a second mutation-dependent variable.

We recommend keeping the comparison as chemically controlled as possible when the purpose of the experiment is to isolate the effect of residue 3.

Sample Preparation and Aggregation State

As with other Aβ peptides, the experimental behavior of E3R Aβ40 can depend strongly on sample history.

Reconstitution solvent, initial monomerization, peptide concentration, pH, ionic strength, temperature and incubation time can influence the distribution of monomeric, prefibrillar and fibrillar species.

For aggregation studies, We recommend documenting these conditions alongside peptide identity and purity.

Batch-specific HPLC and MS information can support molecular identity and purity assessment through Peptide Quality Control.

Researchers requiring additional Aβ point mutations, labeled variants or matched wild-type/mutant sets can use Custom Peptide Synthesis.

Frequently Asked Questions

What is [Arg3]-Amyloid β-Protein (1–40)?

It is an engineered Aβ40 analog containing an E3R substitution, where the native glutamate at residue 3 is replaced by arginine.

What is the sequence of E3R Aβ40?

DARFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVV

The peptide contains 40 amino acids.

Is E3R Aβ40 a familial Alzheimer’s disease mutation?

No. E3R Aβ40 is primarily an engineered mechanistic research analog. It should be distinguished from disease-associated Aβ mutations such as E22G Arctic and E22Q Dutch.

Why is E3R Aβ40 studied?

It is useful for investigating how sequence-dependent changes influence the balance between prefibrillar aggregates and mature fibrils. Published experiments showed increased prefibrillar populations despite an overall fibril-growth rate similar to wild-type Aβ40.

Research Use Only.