Buffer & reagent recipes

The buffers and reagents labs make most often. Each recipe calculates amounts for any volume and strength (1X, 10X…) and covers pH, sterilisation, storage, safety and common questions.

Basic stock solutions

Concentrated solutions used to make other buffers

1 M Tris-HClThe basic ingredient of most molecular-biology buffers.1 L 0.5 M EDTA (pH 8.0)A chelator that traps metal ions and inhibits enzymes such as DNases.1 L 5 M NaClA concentrated stock for adding salt to many buffers.1 L 1 M MgCl₂A magnesium stock for PCR and enzyme reactions.1 L 1 M HEPES (pH 7.4)A buffering agent for culture media and protein buffers, effective at pH 7.2–7.6 and less temperature-sensitive than Tris.1 L 10% SDSAn anionic detergent stock for SDS-PAGE gels, buffers and cell lysis.1 L 10% APS (ammonium persulfate)The initiator that polymerises acrylamide gels; together with TEMED it starts setting within minutes.1 L

Wash & general buffers

Everyday buffers such as PBS, TBS and TE

PBS (phosphate-buffered saline)The most widely used isotonic buffer for washing cells, dilutions and antibody incubations.1X · 10X · pH 7.4 TBS (Tris-buffered saline)A buffer widely used for western blot washes and antibody dilutions.1X · 10X · pH 7.6 TBST (TBS + 0.1% Tween-20)The standard wash, blocking and antibody-dilution solution for western blots; Tween-20 reduces non-specific binding.1 L PBST (PBS + 0.1% Tween-20)A PBS-based wash buffer widely used for ELISA and immunostaining.1 L TE buffer (pH 8.0)A buffer for dissolving and storing DNA and primers: Tris holds the pH and EDTA inhibits DNases.1 L Citrate buffer pH 6.0 (antigen retrieval)Used for heat-induced epitope retrieval (HIER) to unmask formalin-fixed antigens in paraffin IHC.1 L · pH 6.0

Protein & western blot

Lysis, sample, running, transfer and blocking buffers

RIPA lysis bufferThe most common lysis buffer for extracting protein from cells and tissue, including nuclear and membrane proteins.1 L 4X Laemmli sample bufferMixed 1:3 with protein samples before SDS-PAGE to denature them.10 mL SDS-PAGE running buffer (Tris-glycine-SDS)Fills the SDS-PAGE tank.1X · 10X Western blot transfer buffer (Towbin)For wet transfer of proteins from gel to membrane: 25 mM Tris, 192 mM glycine, 20% methanol.1 L 5% non-fat milk blocking solutionCovers empty sites on western blot membranes to lower background: 5% non-fat dry milk in TBST.1 L Western blot stripping buffer (mild)A mildly acidic buffer that removes antibodies so a membrane can be re-probed.1 L · pH 2.2

Nucleic acids & electrophoresis

Agarose-gel buffers and loading dye

50X TAE bufferA concentrated stock of agarose-gel running buffer.1 L 10X TBE bufferA stock of running buffer for sharp separation of small DNA fragments.1 L 6X DNA loading dyeWeighs DNA samples down into the wells and shows run progress with tracking dyes: 30% glycerol, 0.25% bromophenol blue, 0.25% xylene cyanol FF.10 mL

Cells, microbes & staining

Media, fixatives and stains

LB medium (Luria-Bertani, Miller)The basic medium for growing E.1 L 4% PFA (paraformaldehyde) fixativeFixes proteins in place before immunostaining cells or tissue: 4% paraformaldehyde in PBS.1 L · pH 7.2–7.4 0.5% crystal violet staining solutionUsed for colony formation assays and viability staining: 0.5% crystal violet in 20% methanol.100 mL

Compositions are widely used standards. Check the formula weight on your bottles and your institution's safety rules.