Table 1.
Calculated amide II′p frequencies and potential energy distributions for Acetyl-L-P-NH2 and its perdeuterated lecucine isotopomer; Acetyl-A-P-NH2 and its perdeuterated alanine isotopomer.
| Freq. (cm−1)* | Potential energy distributions (>5%) | |
|---|---|---|
| Acetyl-L-P-NH2 | 1444 | C-N s (28) -Cα-H inp b (22) -Cα-C s (10) -C=O inp b (7) |
| Acetyl-L(D)-P-NH2 | 1425 | C-N s (46) -Cα-C s (9) -C=O inp b (9) –C-N s (in Pro ring) (8) Pro ring def (6) |
| Acetyl-A-P-NH2 | 1445 | C-N s (31) -Cα-H inp b (18) –Cα-C s (11) -C=O inp b (7) - C=O inp b (6) |
| Acetyl-A(D)-P-NH2 | 1428 | C-N s (41) -Cα-C s (10) -C=O inp b (8) C-H inp b (Pro) (7) -C-N s (Pro ring) (7) Pro ring def (5) |
*
Our calculated AmII′p frequencies are about 15 cm−1 lower than the Fig. 1 measured values because we did not consider the effect of hydrogen bonding or the impact of the solvent dielectric constant; we previously showed that a 25 cm−1 upshift in the AmII′p frequency will occur due to hydrogen bonding.48