The pellets which were stored at -80°C were resuspended in 20 mL buffer A and cracked with the micro fluidizer. The cell parts were spinned down at 20000 rpm for 20 min at 4°C. The supernatant was transferred to a new 50 mL falcon and stored on ice (!!!).
The following steps were performed:
- equilibration with Buffer A 10 min
- taking 40 µL supernatant (load)+ 10 µL SDS-Buffer - L-Sample
- 50 mL load on column
- taking 40 µL of flow through + 10 µL SDS-buffer - FT-Sample
- first washing with 25ml Buffer A (half the load)
- taking 40 µL of washing flow through + 10 µL SDS-Buffer - W-Sample
- equilibrate with Buffer B (output pipe off the column into glas, input into B)
- hanging pipe on column, 6x2ml Evolutions - E 1-6
- taking 40 µL of Elution 1-6 + 10 µL SDS-Buffer E-sample 1-6
regeneration of column:
- 10min water
- 10min EDTA
- 10min water
- 10min NiSO4
- 10min water
Meanwhile the Elutions 1-6 were pooled (combined 12 mL) in a 50 mL falcon and transferred in a concentrator column which was centrifuged until the volume in the filter was 1,5 mL for injection into the gel filtration station.
Parallel the L-, FL-, W- and E 1-6-samples were analyzed on a SDS-PAGE gel in order to proof the purification in the elution fractions.
The gel shows a huge protein concentration in E1 and E2 so that the purification could be continued with the next step – gel filtration. For that purpose the filtrate out of the concentrator was transferred into a new 2 mL tube resuspending very well without air bubbles.
20 mL of GeFi-buffer werd injected into the 2mL loop. After that the protein filtrate was injected as well.
The GeFi was started according to the following settings:
- Flow rate: 2500-3000 µL / min
- max. pressure: 0,60 – 0,65 mPa
- First endtimer at 80-90 mL volumen before fractioning
- Injectvalve
After observing a peak on the screen 40 µL of different fractions (C7 , C9, C11, D1, D3, D5, D7, D9) covering the peak were taken for analysis via SDS-PAGE gel.
The gel shows that the elutions contain the protein concentrated. The Elutions C7-D9 were pooled and transferred to a new concentrator until an end volume of 400 µL.
The concentrated protein had a pink color. The protein concentrate (38 mg/mL A280) was used for crystallization pure and in a 1:2 dilution with GeFi buffer.
Core I - IV were used for setting drops.