Description

Technical Parameters

Introduction

peptides

product-1400-1400

Products Description

#### **1. Overview of Follistatin 344 peptide**

Follistatin 344 (FS344) is a glycoprotein composed of 344 amino acids and belongs to the follistatin family. Its core function is to regulate cell proliferation, differentiation and muscle growth by binding and inhibiting members of the transforming growth factor-β (TGF-β) superfamily (such as activin and myostatin). FS344 has attracted much attention in the biomedical field, especially in the treatment of muscle diseases, metabolic regulation and regenerative medicine.

#### **2. Structural classification of Follistatin 344**

Based on the modification method, functional domain differences and formulation form, FS344 can be divided into the following categories:

##### **1. Natural unmodified Follistatin 344**

- **Structural characteristics**:

It consists of 344 amino acids and contains 3 functional domains:

- **N-terminal domain** (1-63): involved in activin binding.

- **Central domain** (64-215): rich in cysteine, stabilizing the three-dimensional structure.

- **C-terminal domain** (216-344): enhances the interaction with cell surface proteoglycans.

- **Advantages**:

- High affinity binding to activin and myostatin.

- The natural conformation retains complete biological activity.

- **Physical and chemical properties**:

- Molecular weight: about 38-40 kDa (including glycosylation modification).

- Isoelectric point (pI): 5.2-5.8.

- Solubility: easily soluble in neutral buffer (such as PBS).

- Color and morphology: lyophilized powder is white loose solid, and the solution is colorless transparent liquid.

##### **2. Acetylated Follistatin 344**

- **Structural modification**:

N-terminal or specific lysine residues are acetylated to enhance resistance to enzymatic hydrolysis.

- **Advantages**:

- Prolong half-life in vivo (from several hours to 12-24 hours).

- Reduce immunogenicity.

- **Physicochemical properties**:

- Molecular weight increases by about 42 Da/acetylation site.

- Solubility: needs to be dissolved in a buffer containing a small amount of organic solvent (such as 5% DMSO).

- Color: Lyophilized powder is white to off-white powder.

##### **3. PEGylated Follistatin 344**

- **Structural modification**:

Polyethylene glycol (PEG) molecules (usually 20-40 kDa) are attached by covalent bonds.

- **Advantages**:

- Significantly prolong half-life (up to more than 72 hours).

- Enhance drug delivery efficiency and reduce renal clearance.

- **Physical and chemical properties**:

- Molecular weight: 60-80 kDa (depending on the length of the PEG chain).

- Solubility: Highly water-soluble, but may form a colloidal solution.

- Color: The solution is slightly opalescent, and the lyophilized powder is a white flocculent solid.

##### **4. Truncated Follistatin 344 (FS288/FS315)**

- **Structural features**:

Some amino acids at the C-terminus are missing (such as FS288 contains only 288 amino acids).

- **Advantages**:

- Smaller molecular weight (about 32 kDa), improved tissue permeability.

- Retains activin binding ability, but may reduce stability.

- **Physicochemical properties**:

- Isoelectric point is close to native FS344 (pI 5.0-5.5).

- Solubility: Avoid high salt concentration to prevent aggregation.

#### **3. Detailed analysis of physicochemical properties**

##### **1. Thermal stability**

- Unmodified FS344 is stable at 4℃ for 1-2 weeks and can be stored at -20℃ for more than 6 months.

- PEGylated FS344 is more heat-resistant due to PEG protection and can withstand short-term room temperature exposure.

##### **2. Acid-base stability**

- Optimum pH range: 6.5-7.5.

- Extreme pH (<4 or >9) leads to irreversible denaturation, forming turbidity or precipitation.

##### **3. Spectral characteristics**

- UV absorption peak: 280 nm (tryptophan/tyrosine).

- Fluorescence characteristics: excitation wavelength 280 nm, emission wavelength 340 nm (for endogenous fluorescence detection).

#### **4. Application advantages of different types of Follistatin 344**

| **Category** | **Core advantages** | **Application areas** |

|-------------------------|---------------------------------------|-----------------------------|

| Natural unmodified type | High biological activity, low immunogenicity | Basic research, in vitro cell experiments |

| Acetylated type | Extended half-life, reduced costs | Animal models, chronic disease treatment research |

| PEGylated type | Long-term sustained release, enhanced pharmacokinetics | Clinical trials, muscular dystrophy treatment |

| Truncated type | High tissue permeability | Local administration (such as intramuscular injection) |

#### **5. Relationship between color and formulation form**

1. **Lyophilized powder**: White to off-white, depending on purity and modification type (PEGylation may be flocculent).

2. **Solution state**:

- Unmodified type: Colorless and transparent.

- PEGylated type: Slightly opalescent (colloidal properties).

3. **Denatured state**: turbid or yellow (indicating degradation or oxidation).

#### **6. Safety and toxicity**

- **Immunogenicity**: Unmodified type may induce low-level antibodies, which is further reduced after PEGylation.

- **Acute toxicity**: LD50 >100 mg/kg in animal experiments (intravenous injection in mice).

- **Long-term toxicity**: High doses may interfere with the TGF-β signaling pathway, and liver and kidney function need to be monitored.

#### **7. Future research directions**

1. **New modification technology**: Such as fatty acid chain modification (Palmitoylation) to enhance membrane penetration.

2. **Targeted delivery system**: Nanoparticles encapsulate FS344 to enhance muscle tissue specificity.

3. **Clinical transformation**: Phase III trial for Duchenne muscular dystrophy (DMD) and age-related muscle loss.

#### **8. Summary**

The multi-category differentiation of Follistatin 344 meets the different needs from basic research to clinical treatment. The fine regulation of its physical and chemical properties (such as PEGylation and acetylation) significantly improves its drugability, while the standardization of color and morphology provides an intuitive indicator for quality control. In the future, with the innovation of modification technology, FS344 is expected to achieve breakthroughs in the fields of regenerative medicine and anti-aging.