The protein structure can be defined as the three dimensional arrangement for atom within any particular amino acid chain molecule. This type of protein is referred to as a polymer or polypeptide that is being formed from the numerous sequences of amino acid as well as monomer of polymers involved. Any specified monomer of the amino acid might even be termed as the residue, which indicates about the repeating units within the polymers. Each and every protein forms through amino acid after under going the reactions of condensation, where the amino acid might lose any 1 molecule of water in 1 reaction for the purpose of attaching to each other with the help of one peptide bond.

After consideration of convention, the molecule chain that remains under less than thirty amino acids could be recognized as one peptide and not only a protein. For effectively performing the biological functionality, these proteins could easily fold into 1 and more than 1 specified spatial conformation that is being driven by the total number of a non covalent interaction like hydro phobic packing, ionic interaction, hydrogen bonding, force of Van der waals forcing. Moreover, for understanding each and every function of the protein within the respective molecular level, this is eventually required to understand the 3 dimensional structure. It is the specific topic for structural biology that can employ certain techniques like NMR spectroscopy, dual polarisation interferometry and even X Ray crystallography for successful determination of the protein structure.

These distinctive structures of protein subsequently range in size from around 10 to 1000 amino acid. According to the physical sizes, these proteins could be classified as the nano particles within the range of 1 to 100 nm. The numerous larger aggregates could be effectively formed from proper protein sub unit. As for an example, numerous molecules of actin efficiently assemble within the micro filament.  Any protein usually undergoes the reversible structure based changes while performing the biological function. There are few alternative structures within the similar protein, which are termed as various conformational isomers. These kinds of transitions as well as conformations within the isomers are termed as conformational alterations.

There are four distinctive and important levels of protein structure, which include primary structure, secondary structure, tertiary structure and quaternary structure. The first and the foremost level of protein structure is primary structure. This particular structure of the protein eventually refers to a significant sequence of several amino acid within the entire chain of polypeptide. The primary level is being held altogether by certain bonds of peptide, which are being created during the entire procedure of biosynthesis in protein. There are two ends of this chain of poly peptide, which are being termed as C terminus or carboxyl terminus as well as the N terminus or amino terminus on the basis of the nature or structure of a free group over every extremity. This specific primary level can be determined with the help of gene that corresponds to a protein and a proper sequence of the nucleotides within the DNA could be transcribed into m RNA. It is being read by a ribosome with the procedure, known as translation.

A proper sequence of the proteins is extremely unique to a protein for defining the entire functionality and structure of protein. The protein sequence could even be determined by certain methodologies like tandem mass spectro metry or Edman degradation. However, it is often read directly from gene sequence with the help of genetic code. This is strongly advised to utilize certain words of residues of amino acid while making discussions about protein as when one peptide bond gets formed and the water molecule is being lost. Hence, the proteins are eventually formed of the residues of amino acids. The modification for post translation like glycosylations and phosphorylation is generally being considered as the core part of this primary structure, hence could not be read from genes.

The second level of the protein structure is secondary structure. This particular structure eventually refers to the highly regular local sub structure over the actual chain of poly peptide back bone. The two major kinds of this secondary structure include alpha helix and beta sheets. These two types were being recommended during the year of 1951 and these distinctive secondary structures could be eventually defined by proper patterns of the hydrogen bonds within main chain groups of peptide. These comprise of a regular geometry that are effectively constrained to the respective values for dihedral angle over the plot of Ramachandran. Both of these alpha helix and beta sheets effectively represent a proper methodology to saturate each and every hydrogen bond donor as well as acceptor within the backbone of peptide. Few distinctive portions of this protein structure are being ordered, however they do not comprise of any regular structure and these must not be mixed with the random coil, which is an unfolded chain of poly peptide.

The third distinctive level of protein structure is tertiary structure. This specific structure refers to a 3 dimensional structure of the multi meric or monomeric protein molecule. The alpha helix and beta sheets could be folded into one compact globular structure and the folding is being driven by a non specified hydro phobic interaction or the burial of hydro phobic residue from molecules of water, however the structure can be stated as stable as soon as the protein parts are being locked into a place by the interactions of tertiary like hydrogen bonds or salt bridges. The disulphide bonds could become quite rare within the cytosolic protein. The final protein structure level is quaternary structure, which is also a 3 dimensional structure comprising of a separation of 2 and more chain of poly peptide, which could operate as 1 functional unit. The multimer could be effectively stabilized by similar interactions of non co valence as well as bonds of disulphide within the tertiary structure. There are several possible organizations of quaternary structure and the alpha helix and beta sheets are being involved.