Which of the following amino acids have very high isoelectric pH value, higher than 9 ?

Options

A. Cysteine
B. Aspartic Acid
C. Tyrosine
D. Arginine

Explanation

To determine which of the given amino acids has a very high isoelectric pH value (higher than 9), we will analyze each of the options provided: 16, aspartic acid, tyrosine, and arginine.

### Step-by-Step Solution:

1. **Understanding Isoelectric Point (pI)**:
- The isoelectric point (pI) is the pH at which an amino acid or protein has no net charge. This means that the positive and negative charges balance each other out.
- Basic amino acids typically have higher pI values, while acidic amino acids have lower pI values.

2. **Analyzing Each Amino Acid**:
- **Option 1: 16 (Cysteine)**:
- Cysteine is a neutral amino acid and has a pI value of approximately 5.0.
- Since 5.0 is less than 9, this option does not meet the criteria.

- **Option 2: Aspartic Acid**:
- Aspartic acid is an acidic amino acid with a pI value of around 3.0.
- This value is also below 9, so it does not qualify.

- **Option 3: Tyrosine**:
- Tyrosine is another neutral amino acid with a pI value of about 5.0.
- Similar to the previous options, this is less than 9, so it is not the answer.

- **Option 4: Arginine**:
- Arginine is a basic amino acid and has a pI value of approximately 10.8.
- Since 10.8 is greater than 9, this option meets the criteria.

3. **Conclusion**:
- Among the given amino acids, only arginine has a very high isoelectric pH value, higher than 9.

### Final Answer:
- The amino acid with a very high isoelectric pH value (higher than 9) is **arginine**.