New method to create ultrafast 3-D images of nanostructures

Lensless microscopy with X-rays, or coherent diffractive imaging, is a promising approach. It allows researchers to analyse complex three-dimensional structures, which frequently exist in nature, from a dynamic perspective. ...

Zooming in on an inner-cell DNA repair shop

Inside every cell in your body are molecular machines that help package, read, and repair DNA. These protein assemblies are essential to survival, yet we know little about how they function because, until recently, it was ...

Supercomputers help supercharge protein assembly

Red blood cells are amazing. They pick up oxygen from our lungs and carry it all over our body to keep us alive. The hemoglobin molecule in red blood cells transports oxygen by changing its shape in an all-or-nothing fashion. ...

New tool allows scientists to catch elusive protein in action

Like many of the processes that drive a cell's basic functions, those enabling the splitting of a newly-replicated cell into two, shown above, happen quickly. So quickly, in fact, that scientists often have a hard time pinpointing ...

Protein structure

Proteins are an important class of biological macromolecules present in all biological organisms, made up of such elements as carbon, hydrogen, nitrogen, oxygen, and sulphur. All proteins are polymers of amino acids. The polymers, also known as polypeptides, consist of a sequence of 20 different L-α-amino acids, also referred to as residues. For chains under 40 residues the term peptide is frequently used instead of protein. To be able to perform their biological function, proteins fold into one, or more, specific spatial conformations, driven by a number of noncovalent interactions such as hydrogen bonding, ionic interactions, Van Der Waals forces and hydrophobic packing. In order to understand the functions of proteins at a molecular level, it is often necessary to determine the three dimensional structure of proteins. This is the topic of the scientific field of structural biology, that employs techniques such as X-ray crystallography or NMR spectroscopy, to determine the structure of proteins.

A number of residues are necessary to perform a particular biochemical function, and around 40-50 residues appears to be the lower limit for a functional domain size. Protein sizes range from this lower limit to several thousand residues in multi-functional or structural proteins. However, the current estimate for the average protein length is around 300 residues. Very large aggregates can be formed from protein subunits, for example many thousand actin molecules assemble into a microfilament.

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