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. 2020 Sep 10;61(12):1645–1657. doi: 10.1194/jlr.RA120000951

TABLE 2.

NMR analysis of the Lipid 1256 class

Carbon Number Group Integration 1H δ (ppm) 13C δ (ppm) DQF COSY Correlations HMBC Correlations
1a CH2 2.21b 1.59 27.37 CH2-FA, 2 CH2-FA, 2, 3
2a CH2 2.03c 2.31 36.21 1 1, 3, CH2-FA
3 C = O NA NA 176.40 NA NA
4a CH2 2.21b 1.59 27.37 CH2-FA, 5 CH2-FA, 5, 6
5a CH2 2.30c 2.29 36.59 4 4, 6, CH2-FA
6 C = O NA NA 176.40 NA NA
7d CH2 2.18e 4.41 64.83 7/7′, 8 8, 3, 9
4.18
8 CH 1.00f 5.22 72.99 7, 7′, 9 6, 7*, 9*
9 CH2 2.69g 3.94 66.39 8 8, 7
10 C = O NA NA 173.41 NA NA
11 CH 1.00 4.63 55.74 12, 12′ 12, 10
12d CH2 2.10h 4.26 67.59 11, 12/12′ 11, 10
4.10
13 C = O NA NA 172.95 NA NA
14d CH2 2.69g 3.97 44.59 14/14′ 13, 15
3.89
15 C = O NA NA 174.64 NA NA
16d CH2 2.15 2.55 43.20 16/16′, 17 15, 17, 18
2.53
17 CH 1.00f 5.24 73.64 16, 16′, 18 16, 18*, 19
18 CH2 2.21b 1.62 36.50 17, 19 19, 17, 16*, CH2-FA
19 CH2 ?i 1.35 27.91 18, CH2-FA Overlapping
20 C = O NA NA 176.40 NA NA
21a CH2 2.3c 2.33 36.36 22 22, 20, CH2-FA
22a CH2 2.21b 1.61 27.37 CH2-FA, 21 21, CH2-FA, 20
23j CH2 2.06 1.16 41.53 CH2-FA, 24 CH2-FA, 24, 25
24j CH 0.99 1.51 30.41 23, 25 23, 25, CH2-FA
25j CH3 3.29 0.87 24.31 24 24, 25′, 23
CH2-FAk CH2 2.36 1.28 32.04 Overlapping Overlapping

Refer to Fig. 3A for carbon assignments. All integrals were normalized against the single proton peak for carbon 11. All expected correlations in the DQF COSY were observed, and all but four correlations in the HMBC were observed and are indicated with an asterisk. A 1D 31P NMR spectrum showed the presence of a single 31P peak at −0.98 ppm.

a

Proton peak groupings corresponding to carbons 1,2; 4,5; and 21,22 are very close in both 1H and 13C chemical shifts, and it is not possible to determine which of the three fatty acids the pairs belong to.

b

Proton peaks for carbons 1, 4, 18, and 22 overlap and integrate together to 8.84, and each was assigned an integral of 2.21.

c

Proton peaks for carbons 2, 5, and 21 overlap and integrate together to 6.9, and each was assigned an integral of 2.3.

d

Proton peaks for carbons 7, 12, 14, and 16 correspond to CH2 groups and have two distinct chemical shifts demonstrating restriction from free rotation. For DQF COSY and HMBC correlations, a ′ denotes a second proton peak for the given carbon.

e

The proton peak for carbon 7 at 4.41 ppm integrates to 1.09, while the peak at 4.18 ppm overlaps and cannot be integrated; thus, the integral was taken as 2(1.09) = 2.18.

f

Proton peaks for carbons 8 and 17 overlap and integrate together to 2.0 and each is assigned an integral of 1.00.

g

Proton peaks for carbons 9 and 14 overlap and integrate together to 5.37 and each was assigned an integral of 2.69. Overlapping contaminants cause the area to integrate higher than expected.

h

The proton peak for carbon 12 at 4.26 ppm integrates to 1.05, while the peak at 4.16 ppm overlaps and cannot be integrated; thus, the integral was taken as 2(1.05) = 2.10.

i

Cannot determine integral because the proton peak overlaps with the large signal composed of the CH2 groups of the four fatty acids.

j

Proton peaks corresponding to carbons 23, 24, and 25 for the four fatty acids show perfectly overlapping signals demonstrating that the branched methyls are identical in all four fatty acids. Integrals for peaks 23, 24, and 25 were divided by 4, 4, and 8, respectively.

k

The proton peak corresponding to the overlapping CH2 groups in the fatty acids correspond to 33 carbons and 66 protons. In addition, the proton peak for carbon 19 also overlaps. The integral was thus divided by 34.