Oncology & Cancer

Novel therapeutic targets in cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinoma (cuSCC) is the second most common diagnosed malignancy in the United States, with approximately 700,000 new cases each year. Cumulative exposure to ultraviolet light is the primary environmental ...

Medical research

An experimental peptide could block COVID-19

In hopes of developing a possible treatment for COVID-19, a team of MIT chemists has designed a drug candidate that they believe may block coronaviruses' ability to enter human cells. The potential drug is a short protein ...

Oncology & Cancer

Insights into the diagnosis and treatment brain cancer in children

Ependymoma is a rare form of brain cancer that implicates children and is often tricky to diagnose. Since effective treatment options can be initiated only after a well-formed diagnosis, there is a dire need among the medical ...

Medical research

Cellular protein shredders for the fight against cancer

An international team of researchers led by the Universities of Bonn and Ulm has investigated how a cell's own "protein shredder" can be specifically programmed to fight cancer. The researchers were able to demonstrate the ...

Alzheimer's disease & dementia

New imaging method sheds light on Alzheimer's disease

To understand what happens in the brain when Alzheimer's disease develops, researchers need to be able to study the molecular structures in the neurons affected by Alzheimer's disease. Researchers at Lund University in Sweden ...

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Protein

Proteins (also known as polypeptides) are organic compounds made of amino acids arranged in a linear chain. The amino acids in a polymer chain are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the genetic code specifies 20 standard amino acids, however in certain organisms the genetic code can include selenocysteine — and in certain archaea — pyrrolysine. Shortly after or even during synthesis, the residues in a protein are often chemically modified by post-translational modification, which alter the physical and chemical properties, folding, stability, activity, and ultimately, the function of the proteins. Proteins can also work together to achieve a particular function, and they often associate to form stable complexes.

Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms and participate in virtually every process within cells. Many proteins are enzymes that catalyze biochemical reactions and are vital to metabolism. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, which form a system of scaffolding that maintains cell shape. Other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. Proteins are also necessary in animals' diets, since animals cannot synthesize all the amino acids they need and must obtain essential amino acids from food. Through the process of digestion, animals break down ingested protein into free amino acids that are then used in metabolism.

Proteins were first described and named by the Swedish chemist Jöns Jakob Berzelius in 1838. However, the central role of proteins in living organisms was not fully appreciated until 1926, when James B. Sumner showed that the enzyme urease was a protein. The first protein to be sequenced was insulin, by Frederick Sanger, who won the Nobel Prize for this achievement in 1958. The first protein structures to be solved were hemoglobin and myoglobin, by Max Perutz and Sir John Cowdery Kendrew, respectively, in 1958. The three-dimensional structures of both proteins were first determined by x-ray diffraction analysis; Perutz and Kendrew shared the 1962 Nobel Prize in Chemistry for these discoveries. Proteins may be purified from other cellular components using a variety of techniques such as ultracentrifugation, precipitation, electrophoresis, and chromatography; the advent of genetic engineering has made possible a number of methods to facilitate purification. Methods commonly used to study protein structure and function include immunohistochemistry, site-directed mutagenesis, and mass spectrometry.

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