Maximum possible hydrogen bonds are present in

Options

A. `3.6_(13)` Helix
B. Keratin
C. Silk fibroin
D. `beta-D-` fructose

Answer

To determine the maximum possible hydrogen bonds present in the given options, we need to analyze each structure and its ability to form hydrogen bonds. Let's go through the options step by step.

### Step 1: Analyze the 3.613 Helix
- The 3.613 helix is a type of alpha helix structure commonly found in proteins.
- In this structure, each turn of the helix contains approximately 3.6 amino acid residues.
- Each amino acid in the helix can form hydrogen bonds with another amino acid that is four residues away in the sequence.
- Therefore, the number of hydrogen bonds in a 3.613 helix is relatively high due to the close packing and regular structure.

**Hint:** Look for the number of residues and the pattern of hydrogen bonding in helical structures.

### Step 2: Analyze Keratin and Silk Fibroin
- Keratin and silk fibroin are examples of fibrous proteins.
- Fibrous proteins typically have a more extended structure and do not form as many hydrogen bonds as globular proteins.
- While they do have hydrogen bonds, the overall number is lower compared to the helical structures due to their arrangement and the nature of their amino acid sequences.

**Hint:** Consider the structural characteristics of fibrous proteins and their hydrogen bonding capacity.

### Step 3: Analyze Beta-Defensin
- Beta-defensins are small cationic peptides that also contain beta-sheet structures.
- While they can form hydrogen bonds, the number of hydrogen bonds is generally less than that found in the 3.613 helix.
- The beta-sheet structure does allow for hydrogen bonding between adjacent strands, but it is not as extensive as in the alpha helix.

**Hint:** Compare the hydrogen bonding in beta-sheet structures with that in helical structures.

### Conclusion
After analyzing all the options:
- The 3.613 helix has the highest potential for hydrogen bonding due to its structure and the number of residues involved.
- Keratin and silk fibroin have fewer hydrogen bonds due to their fibrous nature.
- Beta-defensins also have fewer hydrogen bonds compared to the alpha helix.

Thus, the maximum possible hydrogen bonds are present in **3.613 helix**.

### Final Answer
The maximum possible hydrogen bonds are present in **3.613 helix**.