Table 1.

Assignments, secondary structural environment inferred (where possible) from δCα−δCβ, and amino acid composition, of murine fur in descending order of abundance (excluding cysteine/cystine, and tryptophan)

Amino acid	Assignments									2′ary Struct.	Mole %a
	C=O	Cα	Cβ	δCα−δCβ	Cγ	Cγ’	Cδ	Cϵ	Cζ
E/Qb											13.58
G	172	43		43							12.95
S		59	67	−8						S	10.45
P		60	30	30	25		48			S	8.35
L	175	55	40	15	24		24			H	7.45
R		55b	25b	30	25b		40b		156	H	7.32
D/Nb											6.33
Y	174	54	36	18	130		130	116	156	C	5.67
T	175	63	65	-2	20					H	5.58
V		63	30	33	19	19				H	5.41
A	173	51	24e	27						S	5.14
K		55b	32b	23	25b		25b	40b		S	3.68
F	174	54	36	18	140 c		130	130	137	C	2.95
I	173	63	36	27	26	14	12			S	2.93
Hd											1.18
Md											1.02

Bold = High degree of certainty of assignment

H Helix, S Sheet, C Coil

^a Mean of 3 measurements, of which no standard deviation was greater than 0.4 % for any amino acid

^b No signals from these spin systems are uniquely resolved

^c High frequency shoulder on prominent signal at ca. 130 ppm

^d Not observed with confidence on account of low abundance

^e The Ala β-CH₃ has been previously assigned at ca. 15 ppm on the basis of chemical shift and model peptide examples (Kricheldorf and Muller 1984; Yoshimizu and Ando 1990), and at ca. 18 ppm in solubilized SCMKB and denatured SMCKA (Nishikawa et al. 1998b). We do not observe the Cβ−Cα cross peak in the DQF spectrum which would occur at (F2, F1) co-ordinates of ca. (15–18, 65–70) if this assignment were correct. Accordingly we make the tentative assignment shown on the basis of the PDSD—see slice 1537 in Fig. S6. We have noticed (but not quantified) that isotope labelling of non-essential amino acids tends to be lower than of essential amino acids, probably due to de novo biosynthesis from unlabelled carbohydrates. This and the comparatively low abundance of Ala (5 %) may explain our failure to observe the expected Ala spin system with confidence