> For the complete documentation index, see [llms.txt](https://helixfinance.gitbook.io/helixfinance/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://helixfinance.gitbook.io/helixfinance/protocol/helix-mechanism.md).

# Helix Mechanism

**What is $BNA?**

$BNA are unique tokens that can be utilized to help stabilize $DNA price around peg (1 $DNA = 1 $USDC) by reducing circulating supply of $DNA if the time weighted average price (TWAP) goes below peg (1 $DNA = 1 $USDC).

**When can I buy $BNA?**

$BNA can be purchased only on contraction periods, when the TWAP of $DNA is below 1.

Every new epoch on contraction periods, $BNAs are issued in the amount of 3% of current $DNA circulating supply, with a max debt amount of 35%. This means that if bonds reach 35% of circulating supply of $DNA, no more bonds will be issued.

*Note:* $BNA TWAP is based on $DNA price TWAP from the previous epoch as it ends. This means that $DNA TWAP is real-time and $BNATWAP is not.

**Where can I buy $BNA?**

You can buy $BNAs if any are available under the bonds tab. Anyone can buy as many $BNA as they want as long as they have enough $DNA to pay for them.

There is a limit amount (3% of $DNA current circulating supply) of available $BNA per epoch while on contraction periods, and are sold as first come first serve.

**Why should I buy $BNA (bonds)?**

The first and most important reason is bonds help maintain the peg, but will not be the only measure use to keep the protocol on track. We also have a DAO fund which will step in and buy $DNA to get it back to peg.

$BNAsdon't have a expiration date, so you can view them as a investment on the protocol, because long-term you get benefits from holding bonds.

**Incentives for holding $BNA**

The idea is to reward $BNA buyers for helping the protocol, while also protecting the protocol from being manipulated from big players.


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