Medical research

Trio win medicine Nobel for work on how cells adapt to oxygen

Three researchers from the United States and Britain on Monday shared the Nobel Medicine Prize for research into how human cells sense and adapt to changing oxygen levels, opening up new strategies to fight such diseases ...

Neuroscience

Calcium is key to age-related memory loss

Research at the University of Leicester is offering new clues into how and why cognitive functions such as memory and learning become impaired with age. A paper published recently in a specialist neuroscience journal shows ...

Parkinson's & Movement disorders

New research shows Parkinson's disease origins in the gut

In experiments in mice, Johns Hopkins Medicine researchers say they have found additional evidence that Parkinson's disease originates among cells in the gut and travels up the body's neurons to the brain. The study, described ...

Medical research

Sleep and synaptic rhythms

Chronobiologists at Ludwig-Maximilians-Universität (LMU) in Munich, Germany, show in two articles in the journal Science how critical the sleep-wake cycle is for protein and phosphorylation dynamics in synapses to ultimately ...

Neuroscience

Tau-mediated RNA splicing errors linked to Alzheimer's disease

A collaborative study published today in the journal Cell Reports provides evidence for a new molecular cause for neurodegeneration in Alzheimer's disease. The study, led by researchers at Baylor College of Medicine and the ...

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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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