Crystallographic characterization of two novel crystal forms of human insulin induced by chaotropic agents and a shift in pH

Table 2 Properties of crystal packing contact surfaces of insulin hexamers in seven different space groups.

Protein	C2urea	C2scn	C2221urea	C2221scn	1EVR [11]	1EV3 [11]	1MSO [9]	1TRZ [17]	nph-ins^c
Space group	C2	C2	C222 ₁	C222 ₁	P2 ₁	R3	R3	R3	P4 ₃ 2 ₁ 2
B-chain configuration	R₆	R₆	R₆	R₆	R₆	R₆	T₆	T₃R₃^f	R₆
pH	7.0	7.0	6.5	6.5	6.7	8.5	6.3	6.4	7.3
Solvent content. (%)	50	50	64	64	49	40	36		48
Avg B-factor
protein atoms (Å²)	25.5	19.5	32.1	33.5	41.1	30.2	12.0	32.8	34.8
exposed atoms (Å²)	27.9	21.5	34.0	35.9	42.5	34	12.3	34.7	36.5
contact atoms (Å²)	25.0	17.6	26.4	29.1	41.9	35.8	14.1	37.2	34.3
Tot SASA (Å²)^a	14546	14478	40059	41532	15245	13573	13689	13904	15067
A_cont(Å²)^b	2117	2226	4269	4060	2113	2006	3313	2438	2279
fract of tot SASA (%)	14.6	15.4	10.6	9.8	13.9	14.8	24.2	17.5	15.1
Atom type specific area as a fraction of A _cont
C area (%)	55	56	53	53	41	45	46	50	48
O area (%)	25	24	31	32	33	35	37	32	38
N area (%)	21	20	16	15	27	20	18	16	14
S area (%)	0	0	0	0	0	0	0	2	0
C aromatic (%)	31	36	35	35	25	32	14	29	30
C aliphatic (%)	23	20	18	18	16	13	32	21	18
Pos charged Area (%)	5	3	3	3	5	0	16	16	2
Neg charged Area (%)	7	6	13	13	4	5	9	4	9

^aSASA = Solvent accessible surface area.
^bA_cont = contact area between reference molecule and a symmetry related molecule.
^cIn house structure of human insulin co-crystallized with protamine.

ISSN: 1472-6807