The type of amide bond that occurs during the formation of peptide proteins after the interactions of two amino acids, this is the answer to the question of what a peptide bond is.
From a pair of amino acids, a dipeptide appears, that is, a chain of these amino acids, plus a water molecule. According to the same system, longer chains are generated from amino acids in ribosomes, that is, polypeptides and proteins.
Chain Properties
Various amino acids, which are a kind of "building material" for proteins, have a radical R.
As with any amides, the peptide bond of the C-N chain protein, by means of the interaction of canonical structures between the carbonyl carbon and the nitrogen atom, usually has the double property. This usually finds expression in reducing its length to 1.33 angstroms.
All this leads to the following conclusions:
- C, H, O and N - 4 connected atoms, plus 2 a-carbons are located on the same plane. R groups of amino acids anda-carbon hydrogens are already outside this zone.
- H and O in the peptide bond of amino acids and the a-carbons of the amino acid pair are trans-oriented, although the trans-isomer is more stable. In L-amino acids, the R-groups are also trans-oriented, which is present in all peptides and proteins in nature.
- Rotation around the C-N chain is difficult, rotation at the C-C link is more likely.
In order to understand what a peptide bond is, as well as to detect the peptides themselves with proteins and determine their amount in a certain solution, use the biuret reaction.
Arrangements of atoms
Connection in protein peptides is shorter than in other peptide groups, as it has a partial double bond characteristic. Considering what a peptide bond is, we can conclude that its mobility is low.
The electronic construction of the peptide bond sets the solid planar structure of a group of peptides. The planes of such groups are located at an angle to each other. The bond between the a-carbon atom and the a-carboxyl and a-amino groups can rotate freely along its axis, while being limited in size and the nature of the radicals, and this makes it possible for the polypeptide chain to set itself various settings.
Peptide bonds in proteins, as a rule, are in the trans-configuration, that is, the arrangement of a-carbon atoms is located in different parts of the group. The result is the location of side radicals in amino acids at a more distant distance in space from each other.friend.
Protein rupture
When studying what a peptide bond is, its strength is usually taken into account. Such chains do not break on their own under normal conditions inside the cell. That is, at a suitable body temperature and a neutral environment.
In laboratory conditions, the hydrolysis of protein peptide chains is studied in sealed ampoules, inside which there is concentrated hydrochloric acid, at a temperature of over one hundred and five degrees Celsius. Full protein hydrolysis to free amino acids occurs in approximately 24 hours.
On the question of what a peptide bond is inside living organisms, then they break occurs with the participation of certain proteolytic enzymes. In order to find peptides and proteins in a solution, as well as to find out their amount, they use the positive result of substances that contain two or more peptide bonds, that is, the biuret reaction.
Amino acid replacement
Inside the abnormal hemoglobin S, 2 β-chains were mutated, in which glutamate, as well as a negatively charged highly polar amino acid in the sixth position, were replaced with a radical-containing hydrophobic valine.
Inside the mutated hemoglobin is a region that is complementary to another region with the same molecules that contains the altered amino acid. Ultimately, the hemoglobin molecules "stuck together" and formed long fibrillar aggregates that alter the red blood cell and lead to the appearance of a mutated crescent-shaped red blood cell.
Inside oxyhemoglobin S, as a result of a change in protein conformation, a complementary site is masked. Lack of access to it makes it impossible for molecules to connect to each other in this oxyhemoglobin. There are conditions conducive to the formation of HbS aggregates. They increase accumulations of deoxyhemoglobin inside cells. These may include:
- hypoxia;
- alpine conditions;
- physical labor;
- airplane flight.
Sickle Cell Anemia
Since sickle-shaped erythrocytes have low permeability through tissue capillaries, they can block blood vessels and thus create local hypoxia. This will increase the accumulation of deoxyhemoglobin S inside the red blood cells, as well as the rate at which S-hemoglobin aggregates appear and create even more conditions for red blood cell deformation.
Sickle cell disease is a homozygous recessive disease that occurs only when both parents pass on a pair of mutated β-chain genes. After the baby is born, the disease does not manifest itself until large amounts of HbF are changed to HbS. Patients show clinical symptoms that are characteristic of anemia, that is: headaches and dizziness, palpitations, shortness of breath, weakness to infections, and so on.
