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    Recombinant αS purification Protocol

    Jane Balster

    Published: 2024-03-20 DOI: 10.17504/protocols.io.q26g7popkgwz/v1
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    Abstract

    This protocol details the recombinant αS purification.

    Attachments

    Generation of recombinant aS and PFF protocol.docx

    Steps

    Culture Growth and Induction

    1.

    Day 1: Inoculate 5mL of LB/Amp [100: 1µL of 100 Amp stock (freezer) for every 1mL of culture] with 1 colony from LB/Amp plate and put in a shaker at 37°C w/250rpm .

    • Modification:
    1. Inoculate 10mL of LB/Amp with 1 colony (allows more rapid growth).
    • If no viable plate:
    1. Take a stab from glycerol stock (-80°C Freezer) and grow .
    2. Streak LB/Amp agar plate with culture.
    2.

    Day 2: Inoculate 500mL of LB/Amp (100: 1µL of 100 stock for every 1mL of culture) with 5mL of culture and put in shaker at 37°C until O.D = 0.5 – 0.6 (~1.5h -3h 0m 0s)

    • Modification:
    1. Inoculate 1000mL of LB/Amp with 10mL of culture and put in shaker.
    2. Nano-drop:
    • Use 2µL drop.
    • Use LB or LB/Amp as a blank.
    1. Formula to determine the time it will take the culture to hit an OD of 0.5 (assuming 30 min doubling time):
    3.

    Induce with IPTG ( : of ) for every of culture) for 4h- at . 400: 6.4µL of 0.5Molarity (M)) for every 10mLof culture) for 4h-6h 0m 0s at 37°C.

    4.

    Spin down culture at 4600x g,4°C in 500mL buckets (max volume 350mL) in JLA-10.5 rotor (blue rotor, standing centrifuge).

    Note
    First Stopping Point: Pellet can be frozen at -20°C. For > 500mL culture, split pellet into 500mL equivalent fractions

    5.

    Day 3 : Resuspend in 50mLof lysis buffer. Add 1 tablet of protease inhibitor cocktail (NOT MINI) and 50µL of 500PMSF (500 stock in floor -20°C; Final conc. 500; incubate at 37°C without shaking for 35min-0h 40m 0s.

    Lysis Buffer:

    AB
    NaOH40 mM
    Tris pH 8.020 mM
    EDTA1 mM
    Triton X-1000.1%
    6.

    Add 500µL of 1Molarity (M) MgCl2, 500µL of 1Molarity (M) CaCl2, and 20µL of DNase from Roche (200µL total) and incubate at 37°C with 250rpm shaking for1h 0m 0shour.

    7.

    Add 1mL 0.25Molarity (M)EDTA, mix well, and remove cellular debris by centrifugation at 16900x g (JA 25.50 rotor).

    8.

    Add 0.116g of ammonium sulfate per mL of supernatant and stir at 4°C for 1h 0m 0s. Centrifuge at 20000x g,0h 0m 0s for 0h 30m 0s, use new tubes. (~5.8g; Toss pellet).

    9.

    Add 0.244g of ammonium sulfate per mL of supernatant and stir at 4°C for 1h 0m 0s (or 1h 0m 0s). Centrifuge at20000x g,0h 0m 0s for 0h 30m 0s, use new tubes. (~12.9g; **Keep pellet).

    • Quality Control Checkpoint: Pellet should be at bottom of tube. Excessive proteolysis is indicated by floating pellet or significant smearing of pellet along the side of the tube.
    10.

    Day 4: Resolubilize in 25mLs Buffer A and add PMSF to 1. Stir in refrigerator for ~0h 30m 0s.

    Buffer A:

    AB
    Thris pH 8.025 mM
    NaCl20 mM
    EDTA1 mM
    11.

    Dialyze against 1L of Buffer A with 0.5 PMSF .

    12.

    Day 5: Filter through 0.22 filter, Milex, Millipore.

    13.

    LPLC: Run over Anion Exchange column HiTrap Q FF (program: SC IExAlphasS, Buffer A, filtered Buffer B), aS will start to come off at ~20% Buffer B). Keep samples at 4°C. SEE DETAILED QFF PROTOCOL

    Buffer B (filtered):

    AB
    Tris pH 8.025 mM
    NaCl1 M
    EDTA1 mM
    14.

    Concentrate αS positive fractions with Amicon Ultracel-3KD MWCO, Millipore, and exchange into filtered Buffer C. Perform during Day 6 equilibration.

    • Spin the samples at 4500x g,0h 0m 0s for ~0h 20m 0s till final sample volume <= 1mL (lower volume better e.g. 750µL).

    Buffer C (filtered):

    AB
    Tris pH 825 mM
    NaCl1 M
    EDTA1 mM
    15.

    Day 6: LPLC: Run over size exclusion column in Buffer C. aS will start to come off at ~80mL. SEE DETAILED SEC PROTOCOL – Freeze tubes until Conc./BCA.

    16.

    Concentrate aS positive fractions with Amicon Ultracel-3KD MWCO, Millipore, and exchange into sterile PBS.

    • BCA samples and aliquot at desired concentration/volume (recommended at 5).
    • Freeze aliquots at -80°C

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