Table 7. Experimental ¹³C Chemical Shifts and the Corresponding Calculated NMR Shieldings in ppm.

	carbon	δexpa	PBEb	TPSSb	B3LYPb	DLPNO-DSD-PBEP86b,c	DLPNO-MP2c
l-alanine	C-α	50.92	122.75	128.71	122.55	134.94	137.95
	COO	177.71	–3.28	4.56	–8.58	7.33	12.23
	C-β	20.36	154.14	160.50	154.46	165.91	169.45
α-glycine	COO	176.25	–1.78	5.92	–7.56	8.88	14.35
	C-α	43.58	132.05	137.97	131.45	142.82	145.77
l-serine	C-α	55.69	118.11	124.76	118.04	130.21	132.84
	C-β	62.86	107.61	115.51	109.22	121.68	124.33
	COO	175.05	0.13	7.86	–5.01	10.60	16.04
l-aspartic acid	COO	175.91	–1.05	6.80	–6.28	10.43	16.14
	C-α	53.78	116.04	122.71	116.32	129.40	133.00
	C-β	37.77	137.49	145.01	137.91	149.58	153.27
	COOH	174.66	3.73	11.35	–0.88	15.57	19.18
l-cysteine	C-β	28.09	143.55	149.91	144.50	157.26	160.78
	C-α	56.01	117.45	123.82	117.45	129.65	132.15
	COO	173.37	0.39	8.07	–5.52	10.50	15.74
l-threonine	COO	172.06	–0.02	7.70	–5.85	10.90	16.65
	C-α	61.25	111.19	118.34	111.34	123.75	126.31
	C-β	66.93	102.23	109.40	103.91	116.63	118.81
	C-γ	20.48	155.13	161.52	155.00	165.77	169.34

^aExperimental values from ref (18).

^bValues calculated using the scheme described in Section 2.2 with pcSseg-3 and pcSseg-2 basis sets for QM1 and QM2, respectively.

^cpcSseg-3 and def2-TZVP basis sets for QM1 and QM2, respectively, were used, and NormalPNO and LoosePNO settings using the fragment scheme presented in Section 2.2 were used.