Project ongoing · Synthetic biology
BioBrick
We design a protein that latches onto amyloid beta, the molecule that builds up in the brain of people with Alzheimer’s.
- the weight of the protein we are building
- 21.2 kDa
- the amino acids in each of the two halves
- 98
- the possible paths: an experiment makes the choice
- 2
- teams competing at iGEM, in 2025
- 412
For people who come from biology, biotechnology, bioinformatics, chemistry, medicine
The problem
In Alzheimer’s, a protein called amyloid beta builds up in the brain and sticks to itself: first small clumps, then plaques.
The approved drugs are antibodies that attach to the amyloid and get it cleared away. They work, and the benefit is real, but they come at two costs.
| How much | What it means | |
|---|---|---|
| Barely any arrives | under 1% | the share of the drug that reaches the brain from the blood, estimated across several studies |
| ARIA | 12.6% vs. 1.7% | swelling and microhemorrhages in the lecanemab study, compared with those who received placebo |
How we phrase it. ARIA does not depend only on the part of the antibody that calls in the immune defenses: the state of the brain’s blood vessels and the genetic profile of the person receiving the drug matter too. Removing that part reduces a share of the risk, it does not eliminate it. We write “with reduced immune activation”, never “non-inflammatory”.
The idea
There is a different way to get rid of a molecule: a LYTAC. It is a molecule with two ends. One grabs the target outside the cell, the other latches onto a receptor on the surface. The cell pulls everything inside and sends it to the lysosome, where it gets broken down. The method comes from Carolyn Bertozzi’s group.
The LYTACs published so far use two receptors: one that sorts proteins inside the cell, and one from the liver. To grab the target, they use an antibody.
We change both pieces. In place of the receptor, we use LRP1, which sits on the cells of the brain’s blood vessels. In place of the antibody, we use a Z domain: a small protein, without the part that calls in the immune defenses.
No published LYTAC uses LRP1. That is where the project’s case is won or lost.
What we build
A single protein, made of pieces in a row, produced by a bacterium. The gene that encodes it is a transcription unit like any other: a promoter that decides when to switch it on, the gene, a terminator that stops the reading.
PelB Z(Aβ3) C28 (GGGGS)×3 Angiopep-2 6×His
chain → ────────────────────────────────────────────→
│
S─S the bridge between the two cysteines 28
│
chain → ────────────────────────────────────────────→
PelB Z(Aβ3) C28 (GGGGS)×3 Angiopep-2 6×His| Module | Amino acids | What it does |
|---|---|---|
| PelB | 22 | carries the protein into the periplasm, the space between the bacterium’s two membranes |
| Z(Aβ3) | 58 | binds amyloid beta and holds it folded into a hairpin |
| (GGGGS)×3 | 15 | keeps the two pieces apart, so they do not get in each other’s way |
| Angiopep-2 | 19 | latches onto LRP1 |
| 6×His | 6 | used to purify the protein and identify it |
The bacterium that produces it is Escherichia coli BL21(DE3), a non-pathogenic laboratory strain. It is on iGEM’s white list, and the work is done at the first level of biosafety, the lowest one.
The cysteine that decides everything
The Z domain alone binds nothing. The form that works is a pair: two identical copies, joined by a bridge between two sulfur atoms, at position 28 of both.
The bridge does not just hold them together. Without it, the pocket where the amyloid ends up does not exist: the two copies each form half of it.
The bridge forms by itself, and that is the advantage of the design. The PelB signal carries the protein into the periplasm, which is an oxidizing environment, and there two of the bacterium’s enzymes weld the sulfur together during the passage. No extra step in purification.
There is a consequence. If the protein is a pair, it carries two copies of Angiopep-2 instead of one: it latches onto LRP1 with two hands. No one has measured a grip like this, on a protein of this size. So we do not take it for granted.
One amino acid, one season. In an earlier version of ours, position 28 had a threonine instead of a cysteine. One single letter, and the protein would not have bound anything. Before ordering the DNA, the sequence is checked letter by letter against the deposited structure and the original paper.
The experiment that decides
LRP1 is not an incinerator. It pulls in whatever it binds, and only afterward decides: it sends it to the lysosome, recycles it, or carries it to the other side of the cell. What decides is how tight the grip is.
The first experiment measures exactly that. We put the protein on cells from human brain blood vessels and compare it with an identical version but without Angiopep-2. Then we watch, hour by hour, how much of it ends up in the lysosomes.
It is the only measurement in the project that tests something no one has published. And it is the experiment that chooses the path.
- 01
Strategy A
If little of it ends up in the lysosomes, the result is compatible with crossing the barrier. It does not demonstrate that: the proof is the in vitro barrier model, and that is the next step.
- 02
Strategy B
If a lot of it ends up there, the result is compatible with the lysosome path. Then the protein can work in the blood, where it latches onto the amyloid outside the brain without crossing anything.
In both cases, the work on the binding domain does not change: cloning, expression, purification and the thioflavin T assay are identical. That is why it is possible to start without having chosen, and the choice becomes a result of the project instead of a premise.
What we demonstrate and what we do not
This distinction applies to everything we say about the project, here and elsewhere.
| It is produced | that the protein is made in E. coli and purified in its paired form | |
|---|---|---|
| It binds | that it latches onto amyloid beta and slows its aggregation, in proportion to the dose | |
| It protects cells | that it reduces the toxicity of the amyloid on cells in culture | |
| The two pieces coexist | that Angiopep-2 does not stop the Z domain from binding |
| It is not a cure | no efficacy against Alzheimer’s in a person | |
|---|---|---|
| It does not cross | no crossing of the brain barrier in a living organism | |
| It does not destroy | no degradation of the amyloid by the protein itself | |
| It is not a drug | no profile usable in humans |
There is also a limit that we are the first to state. The protein weighs 21.2 kDa. The kidney filters out anything under 60 to 70 kDa, and here the part that in antibodies extends the time spent in the blood is also missing. In the blood, it would last minutes.
For iGEM this is not a problem: the project demonstrates a mechanism, it does not propose a drug, and how long it lasts in the blood does not enter into any of the planned assays. But it is worth stating, for two reasons. Anyone who knows the field asks about it first, and having it addressed in advance is worth more than answering on the spot. And it is the natural way forward: attaching a piece that binds albumin, or putting several copies together.
Six phases, and the controls that make them readable
An assay without controls does not give a weak result: it gives a result that cannot be used. For each phase there is the control without which the result cannot be read, and it is the first thing the judges ask about.
- 1Cloning and expression. The sample before and after switching on the gene, on the same gel.
- 2Extraction and purification. A desalting step before the nickel column: the substance used to break open the bacterium strips away the nickel, and the column has to be thrown out.
- 3Thioflavin T assay. Six controls, including the unmodified Z domain. Then the confirmations under the microscope and the toxicity test on the cells.
- 4Uptake, the pivotal experiment. The comparison with the version without Angiopep-2, competition with another molecule, incubation at 4 degrees.
- 5In vitro barrier model. The measurement of tightness and a tracer: without them, “it got through” and “the barrier was leaking” are the same data point.
- 6Dry lab. Models that start from the structure already deposited. AlphaFold’s metrics say how reliable the model is, not how well the protein binds.
A flat curve is not enough. If the fluorescence does not rise in the thioflavin T assay, there are four possible explanations and three of them are measurement errors: the amyloid aggregated in a way the dye cannot see, the protein quenches the signal, or the amyloid stuck to the plastic of the well. The samples need to be checked under the microscope, and the toxicity on the cells needs to be tested.
iGEM
iGEM is the international synthetic biology competition. It began as a course at MIT in 2003; the first competition, in 2004, had five teams. Since 2022 the final, the Grand Jamboree, has been held in Paris.
The numbers in the chart
| Year | Teams |
|---|---|
| 2023 (44 countries) | 393 teams |
| 2024 (41 countries) | 397 teams |
| 2025 (44 countries) | 412 teams |
Since 2026, gold is no longer voted on directly: it is earned through three special awards that the team chooses at the start. The judges score those, and gold follows as a result. The choice has to be made in March, because it decides what gets measured for the whole season.
A season costs money. Below is the team’s budget, with registration paid early: waiting costs an extra €2,200, almost exactly as much as the cell assays.
The numbers in the chart
| Item | Cost |
|---|---|
| Registration and tickets (iGEM fees) | €12,950 |
| Travel to Paris (10 people, 5 days) | €6,650 |
| Laboratory (reagents and materials) | €3,920 |
| Cell assays | €3,000 |
| Contingency (15%) | €2,290 |
| Confirmations and shipping | €1,250 |
| Bench supplies | €450 |
Where we are
- April 2026We presented the project at Palazzo della Borsa, in front of universities, companies and institutions.
- August 2026We chose what to work on for iGEM 2027 and wrote the plan: the protein to build, the six laboratory phases with their controls, and the budget.
- TodayWe check the sequence against the published structures. The DNA is only ordered afterward.
- 2027We are aiming at iGEM, the international synthetic biology competition: the final, held in Paris since 2022.
Support BioBrick
€750 towards €7,700
Stage 1 of 4: the iGEM registration
The fundraiser is split into stages, and each stage is one specific thing to buy. When we reach one, we publish a video of what we bought.
Opens on 15 February
The box comes from Produzioni dal Basso and only loads if you open it.
Photos
People on the project
Sources
- Grönwall and colleagues, Journal of Biotechnology, 2007: the Z domain that binds amyloid beta.
- Hoyer and colleagues, PNAS, 2008, and the PDB 2OTK structure: the hairpin and the pocket between the two copies.
- Hoyer and Härd, Journal of Molecular Biology, 2008: the bridge between cysteines 28 and the sequence.
- Banik and colleagues, Nature, 2020; Ahn and colleagues, Nature Chemical Biology, 2021: the first LYTACs.
- Tian and colleagues, Science Advances, 2020: how the grip decides the path inside the cell.
- Demeule and colleagues, Journal of Pharmacology and Experimental Therapeutics, 2008: Angiopep-2.
- Storck and colleagues, Journal of Clinical Investigation, 2016: LRP1 and the amyloid.
- van Dyck and colleagues, New England Journal of Medicine, 2023: the CLARITY AD study.
- iGEM: rules, medals, fees and deadlines, competition.igem.org.
- Project document and the team’s technical and financial document, version 5, August 2026.
Do you want to work on it?
You do not need experience and you do not need a CV. Write to us: we invite you to the next meeting, where you meet the team.