If you’re preparing to purify proteins, be prepared to keep a detailed inventory of your cell pellets and purified proteins!

some key info to keep:

• cell pellets (cells that made the protein you asked them to, pelleted by centrifugation so you can remove the media they were growing in: more on harvesting them here: https://bit.ly/ultrasonicshearing & https://youtu.be/qPsQd9K7hm8 )
  • L of growth
  • # of tubes
  • cell type
  • date
  • growth conditions
  • induction conditions if relevant
• purified protein
  • prep date
  • MW*
  • concentration – in mg/mL (which you can measure) & μM (which you can calculate)**
  • storage conditions
    • buffer
    • % glycerol if present
    • size of aliquots***
  • other notes
    • be sure to note if there was anything “different” about this prep

some other notes:

*a Dalton (Da) is 1g/mol. Protein MWs are often given in kDa, which is kg/mol. you can find a protein’s MW using a tool like Expasy ProtParam https://web.expasy.org/protparam/ )- be sure to take any tags or truncations into account

**μM is μg/mol (10^-6 g/mol). to get this, divide MW (in Da) by mg/mL concentration and multiply by 10^6. e.g. if your protein construct has a MW of 27 kDa, this means 1 mol of it will weight 27 kg, which is 27,000 g

*** if you get a big yield, you don’t have to aliquot it all at once (or you’ll fill tons of boxes!)

instead, aliquot some and keep unaliquotted tubes to aliquot later

but do make sure you aliquot so you don’t have to freeze-thaw samples more than needed

here’s a link to my example protein prep inventory template spreadsheet: https://docs.google.com/spreadsheets/d/1Qys8OEK-JlTD8kUvHUN0QsoBG_Gh1t3b/edit?usp=sharing&ouid=110501489579733284162&rtpof=true&sd=true 

here’s a link to yesterday’s post on keeping a detailed plasmid inventory: blog: https://bit.ly/plasmid_inventory ; YouTube: https://youtu.be/Zknk4zNLAQ8  

You can download my template for that here: https://docs.google.com/spreadsheets/d/1eMbZUuWlqO-CEYcR445ZaIHUnZYg2uwq/edit?usp=sharing&ouid=110501489579733284162&rtpof=true&sd=true  

more about protein expression & purification: http://bit.ly/bacterialproteinoverexpression & https://bit.ly/baculovirusexpression & http://bit.ly/proteincleaning

more about molarity & concentrations: http://bit.ly/solutionconcentrations 

more on determining protein concentrations: http://bit.ly/proteinmeasuring

more on dimensional analysis: http://bit.ly/dimensionalanalysising