Final answer:
The student appears to have confused concepts: syn periplanar refers to a conformation in organic chemistry, while β-pleated sheets describe protein secondary structures involving alignment of polypeptide chains and interchain hydrogen bonding.
Step-by-step explanation:
The student's question about 'syn periplanar conformation' actually seems to be an error or typo because it mixes terminology from conformational isomerism frequently used in organic chemistry with descriptions of protein secondary structure. In organic chemistry, syn periplanar refers to a conformation where substituents on adjacent atoms are on the same side and in the same plane, this can be important in the context of reaction mechanisms. However, in the context of protein biochemistry and structure, the reference materials provided discuss β-pleated sheet conformations, which are key components of protein secondary structures. These β-pleated sheets involve multiple polypeptide chains or separate regions of the same chain that align side by side in either parallel or antiparallel fashion and are connected through interchain hydrogen bonding.
For clarity, β-pleated sheets are very important in structural proteins such as silk fibroin and found in many enzymes, providing stability and rigidity to the protein structure. However, this does not describe syn periplanar in organic chemistry, suggesting an error in the original question or a mix-up in concepts.