Question

Poly-L-lysine exists in purè a-helix, B-sheet and random coiled conformations depending upon the solvent conditions. The values of mean residue ellipticity at 220 nm ([@]220) are -35,700, -13,800 and +3,900 deg cm’dmol-l for Alpha-helix, B-sheet and random coil conformations of this polypeptide, respectively. The polypeptide exists in a- helix conformation at pH 10.8 and 25°C. Addition if urea leads to 2 state transition between alpha-helix and random coil conformation. It observed that ([@]222)of polypeptide is -14800deg cm'2 dmol-1 in presence of 6M urea. The percentage of polypeptide in alpha -helix conformation is
1.37
2.41
3.47
4.50​

Answer 1

Poly-L-lysine exists in purè a-helix, B-sheet and random coiled conformations depending

Answer 2

Answer: (3) 0.47



Explanation:At 220 nm,

Alpha helix= –35,700 deg cm² /dmol¹

Beta sheet= –13,800 deg cm² /dmol¹

Random coil= +3,900 deg cm² /dmol¹

At 222 nm,

Polypeptide exist in alpha helix and random coil conformation and total mixture is –14,800 deg cm² /dmol¹



Let,

Alpha helix (X)= –35,700

Random coil (1–X)= +3,900

Total mixture (1)= –14,800

So,

(35,700*X) +3,900(1–X) = –14,800

or, –35700X –3,900X = –14,800–3,900

or, –39,600X = –18,700

or, X = 187/ 396

or, X ≈ 0.472

That Is X= 47%