5E7W

X-ray Structure of Human Recombinant 2Zn insulin at 0.92 Angstrom

X-RAY DIFFRACTION

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Crystallization

Crystalization Experiments
ID	Method	pH	Temperature	Details
1	BATCH MODE	6.3	293	The crystals were prepared by a batch method similar to that of Baker et al, 1988 [1], modified as follows: 0.01g of insulin as a fine powder was placed in a clean test tube; 0.02M HCl was added to dissolve the protein; on addition of 0.15 mL of 0.15 M zinc acetate the solution became cloudy due to precipitation of the protein; 0.3 mL of acetone and then 0.5 mL of trisodium citrate together with 0.8 mL of water were added and the solution went clear; the pH was checked and increased with NaOH to a pH between 8 and 9 for different batches, thus ensuring complete dissolution. It was then adjusted to the required value of pH 6.3. If any slight turbidity occurred, it was removed by warming the solution. The solution was then filtered using a Millipore membrane/acetate cellulose acetate filter. This removes any nuclei which will encourage precipitation or formation of masses of small crystals. The solution was then warmed to 50 deg C by surrounding the test tube with preheated water in a Dewar. This allowed the solution to cool slowly to room temperature. The test tube was lightly sealed with cling film; crystals formed within a few days and were of suitable size for X-ray diffraction within two weeks; the test tube containing crystals was kept at 4 degC prior to data collection. The crystal used for data collection was about 0.2 mm3.

Crystal Properties
Matthews coefficient	Solvent content
1.89	35

Crystal Data

Unit Cell
Length ( Å )	Angle ( ˚ )
a = 81.82	α = 90
b = 81.82	β = 90
c = 33.85	γ = 120

Symmetry
Space Group	H 3

Diffraction

Diffraction Experiment
ID #	Crystal ID	Scattering Type	Data Collection Temperature	Detector	Detector Type	Details	Collection Date	Monochromator	Protocol
1	1	x-ray	100	PIXEL	DECTRIS PILATUS 6M	Data were collected at 16000keV (0.77 Angstrom) and 100 deg K with the Pilatus 6M detector as close to the sample as possible (179.5mm). The EDNA strategy was used to obtain a start angle and 180 deg of data were collected with 0.1 deg oscillation and 0.1s exposure. The resolution of useful diffraction data achieved and used for structure analysis was 0.92 Angstrom.	2012-09-27	M	SINGLE WAVELENGTH

Radiation Source
ID #	Source	Type	Wavelength List	Synchrotron Site	Beamline
1	SYNCHROTRON	DIAMOND BEAMLINE I02	0.77	Diamond	I02

Data Collection

Overall
ID #	Resolution (High)	Resolution (Low)	Percent Possible (Observed)	R Merge I (Observed)	Net I Over Average Sigma (I)	Redundancy	Number Reflections (All)	Number Reflections (Observed)	Observed Criterion Sigma (F)	Observed Criterion Sigma (I)	B (Isotropic) From Wilson Plot
1	0.92	40.91	100	0.034	20.2	5		58647

Highest Resolution Shell
ID #	Resolution (High)	Resolution (Low)	Percent Possible (All)	Percent Possible (Observed)	R Merge I (Observed)	Mean I Over Sigma (Observed)	Redundancy	Number Unique Reflections (All)
1	0.92	0.94	100		0.967	1.6	4.7

Refinement

Statistics
Diffraction ID	Structure Solution Method	Cross Validation method	Starting model	Resolution (High)	Resolution (Low)	Number Reflections (Observed)	Number Reflections (R-Free)	Percent Reflections (Observed)	R-Work	R-Free	R-Free Selection Details	Mean Isotropic B
X-RAY DIFFRACTION	MOLECULAR REPLACEMENT	FREE R-VALUE	3W7Y	0.9519	10	50178	2692	94.9	0.1111	0.1444	thin shells	18.45

Temperature Factor Modeling
Anisotropic B[1][1]	Anisotropic B[1][2]	Anisotropic B[1][3]	Anisotropic B[2][2]	Anisotropic B[2][3]	Anisotropic B[3][3]

Non-Hydrogen Atoms Used in Refinement
Non-Hydrogen Atoms	Number
Protein Atoms	810
Nucleic Acid Atoms
Solvent Atoms	220
Heterogen Atoms	10

Software

Software
Software Name	Purpose
SHELXL	refinement
XDS	data reduction
Aimless	data scaling
PHASER	phasing