The type of amide bond that occurs during the formation of peptide proteins after interactions of two amino acids 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. Using the same system, chains are generated that are more authentic from amino acids in ribosomes, that is, polypeptides and proteins.
Chain Properties
Various amino acids, which are a kind of "building material" for the protein, have the radical R.
As with any amides, the peptide bond of a CN chain protein by the interaction of canonical structures between a carbonyl carbon and a nitrogen atom, as a rule, has a double property. Usually this is manifested in a decrease in its length to 1.33 angstroms.
All this leads to the following conclusions:
- C, H, O, and N are 4 connected atoms, plus 2 a-carbon atoms are located on the same plane. The amino acid groups R and a-carbon hydrogens are already located outside this zone.
- H and O in the peptide bond of amino acids and a-carbons of a pair of amino acids are trans-oriented, although the trans-isomer is more stable. In L-amino acids, R-groups are also trans-oriented, which is present in all peptides and proteins in nature.
- Rotation around the CN chain is complex, more likely rotation at the CC bond.
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 particular solution, they use a biuret reaction.
Atomic arrangements
The compound in protein peptides is shorter than in other peptide groups, since it has a partial double bond characteristic. Given what a peptide bond is, it can be concluded that its mobility is low.
The electronic construction of the peptide bond defines a solid planar structure of the 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 be rotated freely along its axis, although it is limited in the size and nature of the radicals, and this makes it possible for the polypeptide chain to set various settings for itself.
Peptide bonds in proteins, as a rule, are in a trans configuration, that is, the arrangement of a-carbon atoms is located in different parts of the group. The result is the location of the side radicals of amino acids at a more distant distance in space from each other.
Protein breakdown
When studying what a peptide bond is, its strength is usually taken into account. Such chains do not break by themselves under normal conditions inside the cell. That is, at a suitable body temperature and a neutral environment.
In a laboratory, the hydrolysis of protein peptide chains is studied in sealed ampoules, inside which is concentrated hydrochloric acid, at a temperature of over one hundred and five degrees Celsius. Completely protein hydrolysis to the state of free amino acids occurs in about 24 hours.
To the question, what is the peptide bond inside living organisms, then a break in them occurs with the participation of certain proteolyte enzymes. In order to find peptides and proteins in a solution, as well as find out their amount, they use the positive result of substances that contain two or more peptide bonds, i.e. a biuret reaction.
Amino acid replacement
Inside the abnormal hemoglobin S, 2 β-chains mutated, in which glutamate, as well as the negatively charged highly polar amino acid in the sixth position, were replaced by a hydrophobic valine containing the radical.
Inside the mutated hemoglobin, there is a site that is complementary to another site with the same molecules that contains the altered amino acid. Ultimately, the hemoglobin molecules “stuck together” and formed long fibrillar aggregates that change the red blood cell and lead to the appearance of a sickle-shaped mutating red blood cell.
Inside the oxyhemoglobin S, a complementary region is masked as a result of a change in the protein conformation. The lack of access to it does not allow the connection of molecules with each other in this oxyhemoglobin. There are conditions conducive to the formation of HbS aggregates. They increase the accumulation of deoxyhemoglobin inside the cells. These may include:
- hypoxia;
- high mountain conditions;
- physical work;
- flight by plane.
Sickle cell anemia
Since erythrocytes in the form of "sickles" have a low passability through the capillaries of tissues, they can block the vessels and, thus, create local hypoxia. This will increase the accumulation of deoxyhemoglobin S inside red blood cells, as well as the rate at which S-hemoglobin aggregates appear and create even greater conditions for red blood cell deformation.
Sickle cell anemia is a recessive homozygous disease that occurs only when both parents transmit a pair of mutating β-chain genes. After the baby is born, the disease will not manifest itself until such time as large quantities of HbF change 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.