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Why Are Proteins Hard to Isolate?

Update Date: Jan 04, 2020 12:26 PM EST
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Proteins play an important part in many different industries. The pharmaceutical industry researches the interactions of each drug's effects on the proteins it will encounter within the human body. Biotechnology uses proteins to assess some of the most crucial processes of living organisms.


The food industry depends heavily on protein analysis. Even the cosmetic industry utilizes protein research and purification for the development of its products. It's safe to say that the isolation and purification of proteins plays an important role for many businesses across multiple sectors.

Protein Isolation Is Complex

Retrieving a specific protein for study is a more complicated process than you might think. Obtaining a desired protein from a patient's tissue can result in the presence of other undesirable proteins. Isolating the desired protein presents a few common obstacles: 

1.    Researchers can't separate proteins in a single step. In the case of DNA and other nucleic acids, researchers can use a process called selective adsorption to attract the desired, negatively charged DNA molecules to a positively charged substance. However, proteins are not subject to the same, one-step procedure and require multi-step processes for optimal purification.

2.   The amount of the desired protein is often limited. A cell can contain tens of thousands of active proteins, the vast majority of which are other, undesirable proteins. Target proteins can be present in as sparse as femtomolar concentrations, equivalent to 10-15 moles of proteins per litre, much smaller than concentrations necessary for most biophysics' analytical instruments.

3.   Proteins can't be amplified. For DNA and RNA, amplification is possible through a common process known as polymerase chain reaction or reverse transcription polymerase chain reaction. Unfortunately, there is not a similar way to amplify proteins. 

1.             The risk of contamination is always present. As a result of minuscule protein concentrations and the unavailability of amplification techniques resulting in protein loss, contamination happens very easily. Other proteins, cellular parts, and molecules make the study of a particular protein very difficult.

1.             Proteins are unstable. Proteins are easily degraded within living organisms as well as in the laboratory. Denaturation can result from exposure to heat, light, radiation, and solvents, making the study of a protein in its natural state difficult. 

How Can Protein Purification Happen Successfully?

The purification and isolation of proteins is crucial to studying a particular protein's effects on pharmaceuticals, disease processes, and enzymology. However, researchers must employ highly technological, multistep methods for isolation. Current methods include differential centrifugation, differential salt or solvent precipitation, preparative electrophoresis, and gel filtration, affinity, and ion-exchange chromatography.

Each of these methods can be differentiated depending on the types of proteins researchers are interested in. Developing sound methods of protein research is an ongoing effort that is constantly evolving and fueling advancements across many different industries. 

Sources:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5368116/  * http://www-users.med.cornell.edu/~jawagne/proteins_%26_purification.html 

https://pdfs.semanticscholar.org/8aec/55957239fb7a266e5149023db68e6f822d12.pdf 

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