Saturday, 4 January 2014

Blood, sweat, tears and the milk of human kindness! Part 1

Happy New Year to everyone and welcome back to the UTC. This is a new blog site where I will comment on the activities in the Innovation labs, add some supporting material and provide you with links to interesting articles, new and old, in the Life Sciences.

In this first post, I shall reflect on the lab activities since we opened for business at Y10 (and Y12 will follow in Part 2). All comments are of course welcome from students, staff, parents and partner organisations. I the blog format provides another window on the activities that form part of our REAL programme, that's Research Enhanced Active Learning at the UTC.

The first thing that Y10s will think of when they look back on the first term, will be milk! While the Y12s will probably think of GFP and the challenge of presenting their lab work to an audience of experts from Eden Biodesign (see Part 2).

Let's begin with the Y10s. Why you may ask, did I focus so much on milk? Well, my aim was to use a biological fluid that would introduce principles of separation science, volumetric analysis and expose you at an early stage to "Translational Biology". This is the phrase in current use to describe the way in which scientists attempt to harness knowledge of basic biological research for human benefit (both in social and economic terms). The production of cheese from milk is one of the earliest examples of "Biotechnology" and allowed me to introduce the science behind cheese making. While you were acquiring the skills of micro-pipetting, centrifugation and spectrophotometry, you were exploring the problems of protein analysis in biological fluids with a naturally high concentration of fats. Recall that acid and salt (ammonium sulphate) precipitation of proteins from milk was much easier using skimmed milk. If you remember, precipitates were seen to float on the top of the liquid following centrifugation of full milk! Can you think why?

The cheese making class allowed me to demonstrate how enzymes can be used to transform substrates (rennet is an extract from the fourth stomach of young ruminants that contains a number of enzymes that help these animals digest their mother's milk). As with salts and acids, when added to milk, the rennet causes milk to coagulate, forming the curds and whey. 

One of the key components of rennet is the enzyme chymosin (see image on the left), which is a protease (an enzyme that hydrolyses the peptide bonds that underpin the primary structure, or sequence of amino acids, of a protein). Milk proteins such as the caseins sequester calcium ions (one of the valuable nutrients in milk), but when rennet is added to the milk, these proteins are destroyed and their calcium stores released. This process leads to the coagulation stage in cheese making. This process of calcium release from stores in the cell is of fundamental importance in cell biology.

Finally, I want to point out that the use of ion exchange column chromatography to separate out the proteins in milk is one of the most important techniques in Molecular Biology (well to be precise, Biochemistry). [In year 12 (see below), you used a different version of this method, called affinity chromatography]. 

Milk contains several hundred different types of proteins, but some are more abundant than others. I was delighted when you were able to separate proteins on the ion exchange resin (DEAE-Sephacel) using salt to elute the bound (proteins with a net negatively charge). 

SDS PAGE of milk fractions
eluted from DEAE Sephacel
The analysis of your fractions by SDS PAGE, were excellent (see left: from right to left, the two major casein "bands" are eluted from the column, with increasing salt). You can really be proud of your achievements in mastering these manipulative skills and, although I don't expect you to understand all of the principles involved at this stage, you are already carrying out Science at a very high level, and I haven't mentioned your basic microbiology and isolation of plasmid DNA which will form the basis of another posting. 

In the meantime, Happy New Year and see you all next week.  

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