TABLE I: Chandra et al Assignment peak (cm − $^{1}$) Reference S-S 505 [8, 22] Phe 620 [25] Tyr 644 [25] Trp - indole breathing (W18) 763 [26] Trp- N 1 H site vibration (W17) 877 [26] Phe - ring breathing 1004 [8] Trp - ring breathing 1015 [8] Trp- indole ring (C-H deformation) 1338 [26] Trp- W7 wagging 1356 [26] δ (CH 2 ) 1442 [25] Glu- δ (CH 2 ) 1449 [27] Trp -indole ring stretching 1540 [26] Trp -W2 mode 1568 [26] Phe/Tyr 1598 [8] Amide - I 1644 [8] 20