Protocols

Used Protocols

Protocols

Standard protocols

Blunt end ligation

For "intramolecular" ligation of a PCR product the 5'-ends are phosphorylated with T4 Polynucleotidekinase (PNK)
Set up the following reaction:

reagent	volume [ µL]
10x T4 DNA ligase buffer	2.5
T4 PNK	1
PEG 4000 50% (w/v)	2.5
DNA (100 to 600 ng)	x
ddH₂O	to 25

Incubate at 37 °C, 30 min
Heat inactivate at 65 °C, 20 min
Add 1 µL T4 DNA ligase after reaction has cooled down to room temperature
Incubate at room temperature for at least 2 h, overnight also works.
Next step: Transformation via heat shock

Colony PCR

One Reaction mix contains

5 µL 5x GoTaq buffer (Promega)
1 µL MgCl₂ (25 mM stock)
0.5 µL dNTPs (10 mM each)
0.25 µL primer mix (prefix/suffix primers or sequencing primers) 100 mM
17.625 µL ddH₂O
0.125 µL GoTaq polymerase (Promega)
0.5 µL template

PCR program

Cell lysis and denaturation: 5 min, 95 °C
30 cycles

Denaturation: 10 s, 95 °C
Hybridisation: 30 s, annealing temperature
Elongation: 60 s/kb of product, 72 °C

Final elongation: 5 min, 72 °C

Template alternatives

Pick a colony with sterile tip, elute in 100 µL ddH₂O or buffer, store at 4 °C during PCR, plate if insert is of correct size
Pick colony, streak at marked position on a new plate and solute remaining cells on the tip in the PCR tube with reaction mixture, cultivate if insert is of correct size

Gel electrophoresis for control of fragment size

DNA Purification

We used the following kits for DNA purification. For each kit the specific protocol is described seperately:

Thermo Scientific GeneJET Gel Extraction Kit

Note: all centrifugations should be carried out in a table-top microcentrifuge at > 12000 x g/10.000-14.000 rpm
Preparation

Excise gel slice containing the DNA fragment using a clean scalpel or razor blade. Cut as close to the DNA band as possible to minimize the gel volume. Place the gel slice into a pre-weighed 1.5 mL tube. Record the weight of the gel slice. Note: If the purified fragment will be used for cloning reactions, avoid damaging the DNA through UV light exposure. Minimize UV exposure to a few seconds or keep the gel slice on a glass or plastic plate during UV illumination.
Add 1:1 volume of Binding Buffer to the gel slice (volume:weigt)
Incubate the gel mixture at 50-60 °C for 10 min or until the gel slice is completely dissolved. Mix the tube by inversion every few minutes to facilitate the melting process. Ensure that the gel slice is completely dissolved. Vortex the gel buffer mixture briefly before loading on the column.
Check the color of the solution. A yellow color indicates an optimal pH for DNA binding. If the color of the solution is orange or violet, add 10 µL of 3 M sodium acetate, pH 5.2 solution and mix. The color of the mix will become yellow.
Optional: Use this step only when DNA fragment is <500 bp or >10 kb long.
- If the DNA fragment is <500 bp, add 1:2 volume of 100 % isopropanol to the solubilized gel solution. Mix thoroughly.
- If the DNA fragment is >10 kb, add 1:2 volume of water to the solubilized gel solution. Mix thoroughly.

Binding of DNA

Transfer up to 800 µL of the solubilized gel solution (from step 3/4) to the GeneJET purification column. Centrifuge 1 min at 11,000 x g. Discard the flow-through and place the column back into the same collection tube. Note: If the total volume exceeds 800 µL, the solution can be added to the column in stages. After each application, centrifuge the column for 30-60 s and discard the flow through after each spin. Repeat until the entire volume has been applied to the column membrane. Do not exceed 1 g of total agarose gel slice per column.
Add 100 µL of Binding Buffer to the GeneJet purification column. Centrifuge for 1 min. Discard the flow-through and place the column back into the same collection tube.

Washing

Add 700 µL of Wash Buffer to the GeneJet purification column. Centrifuge for 1 min. Discard the flow-through and place the column back into the same collection tube. (We altered the protocol to to wash steps a 350 µL optional)
Centrifuge the empty GeneJet purification column for an additional 1 min to completely remove residual wash buffer

Elution

Transfer the GeneJET purification column into a clean 1.5 mL microcentrifuge tube. Add 50 µL of Elution Buffer to the center of the purification column membrane. Centrifuge for 1 minute. Note: for low DNA amounts the elution volumes can be reduced to increase DNA concentration. An elution volume between 20-50 µL does not significantly reduce the DNA yield. However, elution volumes less than 10 µL are not recommended. If DNA fragment is >10 kb, preheat Elution Buffer to 65 °C before applying to column. If the elution volume is 10 µL and DNA amount is <5 µg, incubate column for 1 min at room temperature before centrifugation.(We altered the protocol to 30 µL Elution Buffer preheated to 60 °C and 1 min incubation before centrifuging for all sizes.)
Discard the GeneJet purification column and store the purified DNA at -20 °C.

Qiagen QIAquick Gel Extraction Kit (Centrifugation)

Note: All centrifugation steps are carried out at 17.900 x g (13.000 rpm) in a conventional table-top microcentrifuge
Preparation

Excise the DNA fragment from the agarose gel with a clean, sharp scalpel
Weigh the gel slice in a colorless tube. Add 3 volumes of Buffer QG to 1 volume gel (100 mg gel - 100 µL). The maximum amount of gel per spin column is 400 mg. For >2 % agarose gels, add 6 volumes Buffer QG
Incubate at 50°C for 10 min (or until the gel slice has completely dissolved). Vortex the tube every 2-3 minutes to help dissolve the gel. After the gel slice has dissolved completely, check that the color of the mixture is yellow(similar to Buffer QG without dissolved agarose). If the color of the mixture is orange or violet, add 10 µL of 3 M sodium acetate, pH 5.0, ad mix. The mixture turns yellow.

Binding of DNA

Add 1 volume isopropanol to the sample and mix.
Place a QIAquick spin column in a provided 2 mL collection tube. To bind DNA, apply the sample to the QIAquick column and centrifuge for 1 min until all the samples have passed through the column. Discard the flow-through and place the QIAquick column back into the same tube. For sample volumes >800 µL, load and spin again.

Washing

If DNA will subsequently be used for sequencing,
in vitro
To wash, add 750 µL Buffer PE to QIAquick column and centrifuge for 1 min. Discard flow-through and place the QIAquick column back into the same tube. If the DNA will be used for salt-sensitive applications (sequencing, blut-ended-ligation) let the column stand 2-5 minutes after addition of Buffer PE. Centrifuge the QIAquick column in the provided 2 mL collection tube for 1 min to remove residual wash buffer
Place QIAquick column into a clean 1.5 mL microcentrifuge tube

Elution

To elute DNA, add 50 µL Buffer EB (10 mM TRIS-HCl, pH 8.5) or water to the center of the QIAquick membrane and centrifuge the column for 1 min. For increased DNA concentration, add 30 µL Buffer EB to the center of the QIAquick column, let the column stand for 1 min, and then centrifuge for 1 min. After the addition of Buffer EB to the QIAquick membrane, increasing the incubation time up to 4 min can increase the yield of purified DNA.
If the purified DNA is to be analyzed on a gel, add 1 volume of loading dye to 5 volumes of purified DNA. Mix the solution by pipetting up and down before loading the gel.

Analytik Jena InnuPREP Gel Extraction Kit

Preparation

Excise the DNA fragment from the agarose gel with a sharp scalpel. Note: minimize the agarose gel slice. Check the weight. Do not use more than 300 mg gel slice for one spin filter.
Transfer the gel slice into a 1.5 mL or 2.0 mL reaction tube and add the 650 µL Gel Solubilizer.
Incubate for 10 min at 50°C until the agarose gel slice is completely dissolved.

Binding of DNA

Add 50 µL Binding Optimizer and mix the suspension by vortexing or piepetting sometimes up and down.
Apply the sample onto the spin filter (green) located in a 2.0 mL Receiver Tube. Close the cap and centrifuge at 10.000 x g (12.000 rpm) for 1 min. Discard the filtrate and re-use the Receiver Tube. Place the Spin Filter back into the 2.0 mL Receiver Tube.

Washing

Open the Spin Filter and add 700 µL Washing Solution LS, close the cap and centrifuge at 10.000 x g (12.000 rpm) for 1 min. Discard the filtrate and re-use the Receiver Tube. Place the Spin Filter back into the 2.0 mL Receiver Tube. Repeat the entire step.
Centrifuge at max speed for 2 min to remove all traces of ethanol. Discard the 2.0 mL Receiver Tube.

Elution

Place the Spin Filter into a 1.5 mL elution Tube. Carefully open the cap of the Spin Filter and add 30-50 µL Elution Buffer (optionally preheated to 50°C). Incubate at room temperature for 1 min. Centrifuge at 6.000 x g (8.000 rpm) for 1 min. A second elution step will increase the yield of extracted DNA. Note: The DNA can be eluted with a lower or a higher volume of Elution Buffer. (...) Store the extracted DNA at +4 °C. For long time storage placing at -20°C us recommended

Promega Wizard SV Gel and PCR CleanUp System

Gel Slice/PCR product preparation

Following electrophoresis, excise DNA band from gel and place gel slice in a 1.5 mL microcentrifuge tube.
Add 10 µL of Membrane Binding solution per 10 mg of gel slice. Vortex and incubate at 50-65 °C until gel slice is copletely dissolved.
Alternative for PCR amplifications: Add an equal volume of Membran Binding Solution to the PCR amplification

Binding of DNA

Insert SV Minicolumn into Collection Tube.
Transfer dissolved gel mixture or prepared PCR product to the Minicolumn assembly. Incubate at room temperature for 1 min.
Centrifuge at 16.000 x g for 1 minute. Discard flow through and reinsert Minicolumn into Collection Tube.

Washing

Add 700 µL Membrane Wash Solution (ethanol added). Centrifuge at 16.000 x g for 1 minute. Discard flow-through and reinsert Minicolumn into Collection Tube.
Repeat previous Step with 500 µL Membrane Washing Solution. Centrifuge at 16.000 x g for 5 minutes.
Empty the Collection Tube and recentrifuge the column assembly for 1 minute with the microcentrifuge lid open (or off) to allow evaporation of any residual ethanol.

Elution

Carefully transfer Minicolumn to a clean 1.5 mL microcentrifuge tube.
Add 50 µL of Nuclease-Free Water to the Minicolumn. Incubate at room temperature for 1 minute. Centrifuge at 16.000 x g for 1 minute.
Discard Minicolumn and store DNA at 4 °C or -20°C.

This assembly method is an isothermal, single-reaction method for assembling multiple overlapping DNA molecules. By coordinating the activity of a 5' exonuclease, a DNA polymerase and a DNA ligase two adjacent DNA fragments with complementary terminal sequence overlaps can be joined into a covalently sealed molecule, without the use of any restriction endonuclease.

Preparation of DNA molecules for in vitro recombination

Generate the complenentary sequence overlaps by PCR using the Phusion DNA-polymerase. If necessary add 5 M Betain in the reaction mix by reducing the amount of H₂O to decrease the number of false PCR products.
Seperate the PCR product of interest by gel electrophoresis, extract the products via Gel Extraction.

In vitro recombination

Preparing assembly mixture

320 µL 5x isothermal reaction buffer
0.64 µL of 10 U ml^-1 T5 exonuclease (for DNA molecules overlapping by greater than 150 bp add 3.2 µL of 10 U mL^-1 T5 exonuclease)
20 µL of 2 U mL^-1 Phusion DNA polymerase
160 µL of 40 U mL^-1 taq DNA ligase
add ddH₂O up to a final volume of 1.2 mL

Aliquote 15 µL of the assembly mixture and store at -20 °C

That 15 µL assembly mixture on ice until use
Add 5 µL of the purified DNA molecules in equimolar amounts (between 10 and 100 ng of each fragment).
Incubate the mixture at 50 °C for 15 to 60 min with 60 min being optimal.

Transformation via heat shock or electroporation without cleaning up the assembly product.

Q5 PCR

Q5

Q5 master mix (25 µL)

5 µL 5 x Q5 buffer
0.5 µL 10 mM dNTPs
Up to 50 ng*µL^-1template
0.1 µL Q5 DNA polymerase
0.5-1 µL primer 10 µM each
Ad 25 µL dH₂O

Q5 standard protocol

Initial denaturation: 98°C - 30 s
30-35 cycles of

Denaturation: 98 °C - 20 s
Annealing: 50-75 °C - 30 s
Elongation: 72 °C - 20 s/kb

Final elongation: 72 °C - 5 min
Storage: 4 °C

Generating competent cells

We generated chemocompetent, ultra-chemocompetent and electrocompetent E. coli using the following protocols:

Chemo competent cells

Preparation

Cool 5 50 mL Falcons
Cool TSS buffer
Cool centrifuge

Protocol

Inoculate 2 x 3 mL LB with bacterial stock over night at 37 °C and 200 rpm
Inoculate 1 x 250 mL LB with the over night cultures in 1 L flask at 37 °C and 140 rpm
Incubate to OD₆₀₀ 0.4-0.6
Devide the culture into 5 cooled 50 mL falcons and incubate on ice for 10 min
Onwards all steps at 4 °C
Centrifuge at 3000 rpm, 4 °C, 10 min
Discard supernatant
Pipette remaining media out carefully
Add 10% volume cold TSS buffer of original cultur, about 1-2 mL
Resuspend pellet
Aliquot 100 µL and drop in liquid nitrogen immediatly
Store at -80 °C

Electro competent cells

Preparation

Autoclave 550 mL LB-Medium
Cool 1 L bidest. H₂O
Cool 50 mL 10% glycerine
Cool 10 50 mL Falcons

Protocol

Inoculate 2 x 3 mL LB with bacterial stock, incubate over night at 37 °C and 200 rpm
Inoculate 2 x 250 mL LB with the over night culture in 1 L flask at 37 °C and 140 rpm
Cultivate until OD₆₀₀0.4-0.6
Store on ice for 15-30 min
Onwards all steps at 4 °C
Divide the cultures into the pre-cooled 50 mL Falcons and centrifuge at 4000 rpm, 4 °C, 15 min with slow acceleration and decceleration
Discard supernatant
Resuspend in 5 mL cooled bidest H₂O shaking gently
Pool two suspensions, add bidest. H₂ to 50 mL and centrifuge again at 4000 rpm, 4°C, 15 min
Discard supernatant
Resuspend pellet in 5 mL cooled bidest H₂O
Add bidest H₂O up to 50 mL and centrifuge again at 4000 rpm, 4 °C, 15 min
Discard supernatant
Resuspend in 5 mL cooled 10% glycerine
Transfer suspensions in two 50 mL falcons and centrifuge again at 4000 rpm, 4 °C, 15 min
Discard supernatant
Add 1 volume similar to the pellet of 10% glycerine and resuspend
Aliquot in 50 µL and freeze in liquid nitrogen immediately
Store at -80 °C

Ultra chemo competent cells

Preparation

Inoculate 10 mL LB medium in a 100 mL flask with 50 µL cells from glycerol culture, e.g. E. coli DH5a MCR
Incubate over night at 37 °C and 180 rpm

Protocol

Precool centrifuge and media
Inoculate 250 mL SOB-Medium in a 1 L flask with 2.5 mL of the preculture
Incubate at 19 °C and 180 rpm up to OD₆₀₀ 0.5 (about 24-36 hours)
Cool flask 10 min in ice water
Onwards all steps at 4 °C
Devide the culture in 5 50 mL cooled falcons
Centrifuge 5 min at 4 °C and 5000 x g
Discard supernatant
Resuspend in each 6 mL icecold TB Buffer
Incubate 10 min on ice
Centrifuge 5 min at 4 °C and 5000 x g
Discard supernatant
Resuspend in each 6 mL icecold TB Buffer
Add 420 µL DMSO and vortex immediately
Aliquot 150 µL and freeze in liquid nitrogen immediately
Store at - 80 °C

Plasmid Isolation

For Plasmid Isolation we used the following kits. The methods are described seperately:

PureYield^TM Plasmid Miniprep System (Promega)

Prepare Lysate

Add 600 µL of bacterial culture to a 1.5 mL microcentrifuge tube
Alternative for larger cultures: Centrifuge 1.5 mL bacterial culture for 30 s at maximum speed in a microcentrifuge. Discard the supernatant. Add an additional 1.5 mL bacterial culture to the same tube and repeat previous step. Add 600 µL of TE buffer or water to the pellet, and resuspend completely.
Add 100 µL of Cell Lysis Buffer (blue), and mix by inverting the tube 6 times.
Add 350 µL of cold (4-8 °C) Neutralization Solution and mix thoroughly by inverting.
Centrifuge at maximum speed in a microcentrifuge for 3 minutes.
Transfer the supernatant (about 900 µL) to a PureYield^TM Minicolumn without disturbing the cell debris pellet
Place the minicolumn into a Collection Tube and centrifuge at maximum speed in a microcentrifuge for 15 s
Discard the flowthrough, and place the minicolumn into the same Collection Tube.

Wash

Add 200 µL of Endotoxin Removal Wash (ERB) to the minicolumn. Centrifuge at maximum speed in a microcentrifuge for 15 s
Add 400 µL of Column Wash Solution (CWC)to the minicolumn. Centrifuge at maximum speed in a microcentrifuge for 30 seconds

Elute

Transfer the microcolumn to a clean 1.5 mL microcentrifuge tube, then add 30 µL of Elution Buffer or nuclease-free water directly to the minicolumn matrix. Let stand for 1 minute at room temperature
Centrifuge for 15 seconds to elute the plasmid DNA. Cap the microcentrifuge tube, and store eluted plasmid DNA at -20°C

Thermo Scientific GeneJET Plasmid Miniprep Kit (Centrifugation)

All purification steps should be carried out at room temperature.
All centrifugations should be carried out in a table-top microcentrifuge at >12.000 x g (10.000-14.000 rpm)
Use 1-5 mL of E. coli culture in LB media for purification of high-copy plasmids.
Use up to 10 mL culture for low-copy plasmids
Protocol

Resuspend the pelleted cells in 250 µL of the Resuspension Solution. Transfer the cell suspension to a microcentrifuge tube. The bacteria should be resuspended completely by vortexing or pipetting up and down until no cells clumps remain.Note: Ensure RNase A has been added to the Resuspension Solution.
Add 250 µL of the Lysis Solution and mix throughly by inverting the tube 4-6 tines until the solution becomes viscous and slightly clear. Note: Do not vortex to avoid shearing of chromosomal DNA. Do not incubate for more than 4 min to avoid denaturation of supercoiled DNA.
Add 350 µL of the Neutralization Solution and mix immediately and thoroughly by inverting the tube 4-6 times. Note:It is important to mix throughly and gently after the addition of the Neutralization Solution to avoid localized precipitation of bacterial cell debris. The neutralized bacterial lysate should become cloudy.
Centrifuge for 5 min to pellet cell debris and chromosomal DNA
Transfer the supernatant to the supplied GeneJET spin column by decanting or pipetting. Avoid disturbing or transferring the white precipitate.
Centrifuge for 1 min. Discard the flow-through and place the column back into the same collection tube.
Add 500 µL of the Wash Solution (diluted with ethanol prior to use) to the GeneJET spin column. Centrifuge for 30-60 seconds and discard the flow-through. Place the column back into the same collection tube.
Repeat the wash procedure using 500 µL of the Wash Solution
Discard the flow-through and centrifuge an additional 1 min to remove residual Wash Solution. This step is essential to avoid residual ethanol in plasmid preps.
Transfer the GeneJET spin column into a fresh 1.5 mL microcentrifuge tube. Add 50 µL of the Elution Buffer to the center of GeneJET spin column membrane to elute the plasmid DNA. Take care not to contact the membrane with the pipette tip. incubate for 2 min at room temperature and centrifuge for 2 min.
Discard the column and store the purified plasmid DNA at -20°C.

Analytik Jena innuPREP Plasmid Mini Kit (Centrifugation)

Starting material: 0.5-5.0 mL
Pellet cells

Centrifuge: max speed, 1 min
Discard supernatant completely

Resuspend cells

Add 250 µL Resuspension Buffer
Vortex

Lysis (do not vortex)

Add 250 µL Lysis Buffer
Mix: invert tube 6-8 times
Lysis time: <5 min

Neutralization

Add 350 µL Neutralization Buffer
Mix: invert tube 6-8 times
Centrifuge max speed, 8 min

Binding of DNA

Add Spin Filter to Receiver Tube
Add clarified sample Spin Filter
Centrifuge at 11.000 x g (12.000 rpm) 1 min

Washing

Add 500 µL Washing Solution A
Centrifuge 1 min at 11.000 g (12.000 rpm)
Add 700 µL Washing Solution B
Centrifuge 11.000 x g (12.000 rpm) 1 min

Remove ethanol

Discard filtrate
Add Spin Filter to Receiver Tube
Centrifuge Max speed, 2 min

Elution

Add Spin Filter to a 1.5 mL reaction tube
Add 50-100 µL Elution Buffer P
Incubation 1 min at room temperature
Centrifuge at 11.000 x g (12.000 rpm) 1 min

QIAprep Spin Miniprep Kit (Qiagen)

All centrifugation steps are carried out at 13.000 rpm (17.900m x g) in a conventional table-top microcentrifuge
Pellet 1-5 mL bacterial overnight culture by centrifugation at >8.000 rpm (6.800 x g) for 3 min at room temperature (15-25 °C)
Resuspend pelleted bacterial cells in 250 µL Buffer P1 and transfer to a microcentrifuge tube.
Add 250 µL Buffer P2 and mix thoroughly by inverting the tube 4-6 times until the solution becomes clear. Do not allow the lysis reaction to proceed for more than 5 min . If using LyseBlue reagent, the solution will turn blue.
Add 350 µL Buffer N3 and mix immediately and thoroughly by inverting the tube 4-6 times. If using LyseBlue reagent, the solution will turn colorless.
Centrifuge for 10 minutes at 13.000 rpm (17.900 x g) in a table-top microcentrifuge.
Apply the supernatant to the QIAprep spin column by decanting or pipetting. Centrifuge for 30-60 s and discard the flow-through.
Wash the QIAprep spin column by adding 500 µL Buffer PB. Centrifuge for 30-60 s and discard the flow-through
Wash the QIAprep spin column by adding 750 µL Buffer PB. Centrifuge for 30-60 s and discard the flow-through. Transfer the QIAprep spin column to the collection tube.
Centrifuge for 1 min to remove residual wash buffer.
Place the QIAprep column in a clean 1.5 mL microcentrifuge tube. To elute DNA, add 50 µL Buffer EB(10mM Tris-Cl, pH8.5) or water to the center of the QIAprep spin column, let it stand for 1 min, and centrifuge for 1 min.

Standard BioBrick Assembly

Modified from Silver Lab
Minimum size of the BioBricks for this methods is 150 bp, whereas it should be at least 500 bp bigger or smaller than the used backbone. The BioBricks, which complies with these conditions, is used as the insert and is assembled into the prefix or suffix of the other BioBrick called vector. The methods differ in prefix and suffix insertion.
Suffix insertion

Digestion of inserted Biobrick

Acquire > 700 ng DNA (10 µL volume)
Add 1 µL 10 x NEBuffer
Add 0.5 µL XbaI
Add 0.5 µL PstI
Digest 1 h at 37 °C
Inactivate 20 min at 80 °C
Clean up via gel electrophoresis, cut and extract from gel

Digestion of the vector

Acquire about 700 ng DNA (10 µL volume)
Add 1 µL 10 x NEBuffer 2.1
Add 0.5 µL SpeI
Add 0.5 µL PstI
Digest 1 h at 37 °C
Inactivate 20 min at 80 °C
Add 1 µL Antarctic Phosphatase (AP) and 1.2 µL 10 x AP reaction buffer
Incubate 1 h at 37°C
Clean up with PCR clean up kit

Ligation

Mix 50-200 ng vector with 3-10 fold molar access of insert
Add 2 µL T4-Ligase-Buffer, 1 µL T4-DNA-Ligase
Incubate for a minimum 20-30 min at room temperature (we usually ligate over night)
Inactivate 5 min at 70 °C
Store at -20 °C or transform

Prefix insertion

Follow protocol of Suffix insertion, replace the restriction enzymes as following:

Digest insert with EcoRI and SpeI
Digest vector with EcoRI and XbaI

Transformation via Electroporation

Thaw 50 µL electrocompetent E. coli cells on ice, dilute with icecold 50 µL glycerine (10%) if necessary
Add 0.5-5 µL plasmid to 50 µL electrocompetent cells
Store cells on ice for 1 minute
Electroporate at U = 2.5 kV, C = 25 µF, R = 400 Ω
Transfer transformation reaction to 450 µL SOC-Medium and incubate 1 h at 37 °C
Plate on selective LB-Medium
Incubate over night at 37 °C

Transformation via Heat Shock

Thaw 100 µL chemo competent E. coli cells on ice
Add 0.5-5 µL plasmid to 100 µl chemocompetent cells
Store cells on ice for 10-30 min on ice
Heat shock for 90 seconds at 42 °C
Store reaction on ice for 60 seconds
Optional: Preheat SOC medium to 37 °C
Transfer reaction to 1 ml SOC medium and incubate at 37 °C for at least 1 hour
Centrifuge 3 minutes at 12000 rpm and plate on selective LB medium
Incubate at 37 °C over night

SDS-PAGE

Pouring the polyacrylamide gel:

For 2 resolving gel (14 %):

4.7 mL Bisacrylamid/Acrylamid (0.8 %; , 30 %;, at the ratio of 37.5:1)
2.7 mL H₂O
2.5 mL 0.5 M TRIS-HCl, pH 6.8
0.1 mL 10% SDS

Add 50 µL 10 % ammonium persulfate and 10 µL TEMED and mix.

Pour the solution quickly into the gel casting form. Leave about 2 centimeters below the bottom of the comb for the stacking gel.

Layer isopropanol on top of the gel.

Leave the resolving gel at room temperature for 30-45 minutes to polymerize.

Remove isopropanol and wash the surface of the separating gel with H₂O. Wait until the surface is dry.

For 2 stacking gel (4 %):

1.3 mL Bisacrylamid/Acrylamid (0.8 %; , 30 %;, at the ratio of 37.5:1)
6.1 mL H₂O
2.5 mL 0.5 M TRIS-HCl, pH 6.8
0.1 mL 10% SDS
50 µL 10 % ammonium persulfate
5 µL TEMED

Add 50 µL 10 % ammonium persulfate and 5 µL TEMED to each aliquote and mix.

Insert comb without getting bubbles stuck underneath.

Leave the gel at room temperature for 30-45 minutes to polymerize.

For storage:

Remove sealing and store the gel wrapped in moistened paper towel at 4 °C.

Preparing the sample:

Mix your protein mixture 3:1 with PBJR buffer (15 µL protein solution + 5 µL PBJR buffer)
Heat for 5 minutes at 95 °C

Running the gel:

Remove sealing, put the polymerized gel into gel box and pour 1x SDS-PAGE running buffer into the negative and positive electrode chamber.
Remove comp without destroying the gel pockets.
Pipet the SDS running buffer in the gel pockets up and down for flushing the gel pockets.
Pipet slowly 20 µL of the sample into the gel pockets.
Make sure to include at least one lane with molecular weight standards (PageRuler Prestained Protein Ladder™ (Fa. Fermentas)) to determinate the molecular weight of the sample.
Connect the power lead and run the gel with 180 V until the distance of the lowest molecular weight standard lane to the gel end is down to 0.5 cm.

Staining the polyacrylamide gel (Colloidal Coomassie Brilliant Blue staining):

After finishing the SDS-PAGE remove gel from gel casting form and transfer it into a box.
Add 100 mL of the Colloidal Coomaassie Brilliant Blue staining solution to your polyacrylamid gel.
Incubate the gel in the solution at room temperature until the protein bands got an intensive blue color. Shake the gel continuously during incubation.
Remove the staining solution.
Wash the gel with destaining buffer.
Incubate the gel in H₂O (2-6 h) for bleaching the background. Shake the gel continuously during incubation. If necessary replace the colored water with new one.

MALDI-TOF/TOF sample preparation

Tryptic digest of gel lanes for analysis with MALDI-TOF:

Be careful that skin scales or hair do not contaminate your sample. So wear hand gloves and tie up your hair.
Reaction tubes have to be cleaned with 60 % (v/v) CH₃CN and 0.1 % (v/v) TFA. Afterwards the solution has to be removed completely followed by evaporation of the tubes under a fume hood. Alternatively, microtiter plates from Greiner® (REF 650161) can be used without washing. If you work with reaction tubes from Eppendorf, you do not need the wash step either.
Cut out the protein lanes of a Coomassie-stained SDS-PAGE using a clean scalpel. Gel parts are transferred to the washed reaction tubes. If necessary, cut the parts to smaller slices
Gel slices should be washed two times. Therefore add 200 µL 30 % (v/v) acetonitrile in 0.1 M ammonium hydrogen carbonate each time and shake lightly for 20 minutes till the gel slices are destained. Remove supernatant and discard to special waste
Dry gel slices at least 30 minutes in a Speedvac.
Rehydrate gel slices in 15 µL trypsin solution followed by short centrifugation.

Trypsin-solution: 1 µL trypsin + 14 µL 10 mM NH₄HCO₃

For this solution solubilize lyophilized trypsin in 200 µl of provided buffer and activate Trypsin for 15 minutes at 30 °C. For further use it can be stored at -20 °C.

Gel slices have to be incubated 30 minutes at room temperature, followed by incubation at 37 °C overnight
Dry gel slices at least 60 minutes in a Speedvac.
According to the size of the gel slice, add 5 - 20 µL 50 % (v/v) ACN / 0.1 % (v/v) TFA
Samples can be used for MALDI measurement or stored at -20 °C

Preparation and Spotting for analysis of peptides on Bruker AnchorChips:

Spot 0.5 - 1 µL of sample aliquot
Add 1 µL HCCA matrix solution to the spotted sample aliquots. Pipet up and down approximately five times to obtain a sufficient mixing. Be careful not to contact the AnchorChip. Note: Most of the sample solvent needs to be gone in order to achieve a sufficiently low water content. When the matrix solution is added to the previously spotted sample aliquot at a too high water content in the mixture, it will result in undesired crystallization of the matrix outside the anchor spot area.
Dry the prepared spots at room temperature
Spot external calibrants on the adjacent calibrant spot positions. Use the calibrant stock solution (Bruker’s “Peptide Calibration Standard II”, Part number #222570), add 125 µL of 0.1 % TFA (v/v) in 30 % ACN to the vial. Vortex and sonicate the vial.
Mix the calibrant stock solution in a 1:200 ratio with HCCA matrix and deposit 1 µL of the mixture onto the calibrant spots.
Analyze samples in ultrafleXtreme by Bruker Daltonics.

Phagemid display

Preparing immune-tubes for phage panning:

Dilute 45 μg of your target protein in 1.5 mL 1 M NaHCO3
Incubate rolling over night at 4 °C and discard the rest
Coat free surfaces by incubating 1 h filled with 5 mg/mL BSA
Wash three times with PBST
Store at 4 °C in the dark

Phagemid display:
Insert a variable library of binding protein CDSs in the phagemid vector pAK100 by Gibson or restriction cloning
Transformate the vector in E. coli ER2738
Remaining colonies form the phagemid library, screened for binders in the following procedure
Wash up all colonies with 5 mL LB and inoculate 200 mL LB, containing chloramphenicol, up to OD 0.1
Incubate the culture, shaking at 37°C, up to OD 0.5
Add 10 x Phages per E. coli cell to infect the bacteria
Incubate 1.5 h at 37°C, then add kanamycin
Incubate further 1.5 h at 37°C
Centrifuge at 5,000 g for 10 min and decant the supernatant
Add 25 %vol PEG NaCl and mix well
Precipitation of produced phages at 4 °C, over night
Centrifuge at 12,000 g and 4°C for 30 min and discard the supernatant
Resuspend the pellet with 3 mL PBS and centrifuge at 13,000 g and room temperature for 10 min and decant the supernatant
Add 20 %vol PEG NaCl and precipitate for 1 h on ice
Centrifuge at 4 °C and 13,000 g for 10 min and discard supernatant
Resuspend the pellet in 500 μL PBS
Centrifuge at 13,000 g and room temperature for 10 min
Measure UV-VIS absorbance of an 1:50 aliquot at 269 nm and 320 nm to calculate the phage concentration
Add 1x1012 to 5x1012 Phages diluted in 1 mL PBST containing 1 mg/mL BSA on the prepared immune-tubes and incubate rolling at 4°C for 1 h
Wash the immune-tubes carefully with PBST for at least 10 times and discard the washing buffer
Eluate remaining phages by adding 1 mL Glycine-HCl, containing 1 mg/mL BSA by incubating rolling for 10 min at room temperature
Neutralize the eluate by adding 150 μL TRIS at pH 9
Add 10 μL eluted phages to 140 μL of E. coli ER2738 at OD 0.5, incubate for 10 min at room temperature and ausstreichen at LB agar containing tetracycline and chloramphenicol

Team:Bielefeld-CeBiTec/Experiments/Protocols

Protocols

Used Protocols

Protocols

Standard protocols

Blunt end ligation

Colony PCR

DNA Purification

Thermo Scientific GeneJET Gel Extraction Kit

Qiagen QIAquick Gel Extraction Kit (Centrifugation)

Analytik Jena InnuPREP Gel Extraction Kit

Promega Wizard SV Gel and PCR CleanUp System

Gibson Assembly

Q5 PCR

Generating competent cells

Chemo competent cells

Electro competent cells

Ultra chemo competent cells

Plasmid Isolation

PureYield^TM Plasmid Miniprep System (Promega)

Thermo Scientific GeneJET Plasmid Miniprep Kit (Centrifugation)

Analytik Jena innuPREP Plasmid Mini Kit (Centrifugation)

QIAprep Spin Miniprep Kit (Qiagen)

Standard BioBrick Assembly

Transformation via Electroporation

Transformation via Heat Shock

SDS-PAGE

MALDI-TOF/TOF sample preparation

Phagemid display