Proteins, dipeptides

Chumanov, G.D., Efremov, R.G., and Nabiev, LR. (1990) Surface-enhanced Raman spectroscopy of biomolecules 1. Water-soluble proteins, dipeptides and amino acids. Journal of Raman Spectroscopy, 21, 43-48. 

Amino acids join together to form the (amide or) peptide bond of peptides and proteins. Dipeptides and tripeptides are formed, for example, by the combination of two and three amino acids, respectively. The individual amino acids within the peptide are known as residues, and whereas polypeptides usually contain less than 50 residues, proteins often contain more than 50 residues. 

M.p. 246-250°C (decomp.). A dipeptide present in mammalian muscle. Like anserine it contains the amino-acid -alanine which is not found in proteins. 

A dipeptide is a molecule consisting of two ammo acids joined by a peptide bond A tnpeptide has three ammo acids joined by two peptide bonds a tetrapeptide has four ammo acids and so on Peptides with more than 30-50 ammo acids are polypeptides Proteins are polypeptides that have some biological function... 

A key biochemical reaction of ammo acids is their conversion to peptides polypeptides and proteins In all these substances ammo acids are linked together by amide bonds The amide bond between the ammo group of one ammo acid and the carboxyl of another IS called a peptide bond Alanylglycme is a representative dipeptide... 

Proteins. The most abundant and physiologically diverse natural biopolymers are proteins, which make up enzymes, hormones, and stmctural material such as hair, skin, and connective tissue. The monomer units of natural proteins, a-amino acids, condense to form dipeptides, tripeptides, polypeptides, and proteins. 

AG Anderson, J Hermans. Microfoldmg Conformational probability map for the alanine dipeptide in water from molecular dynamics simulations. Proteins 3 262-265, 1988. 

Proteins and peptides are amino acid polymers in which the individual amino acids, called residues, are linked together by amide bonds, or peptide bonds. An amino group from one residue forms an amide bond with the carboxyl of a second residue, the amino group of the second forms an amide bond with the carboxyl of a third, and so on. For example, alanylserine is the dipeptide that... 

An exopeptidase that sequentially releases a dipeptide from the N-terminus of a protein or peptide. Dipeptidy 1-peptidases are included in Enzyme Nomenclature subsubclass 3.4.14 along with tripeptidyl-peptidases. 

An exopeptidase that sequentially releases dipeptides from the C-terminus of a protein or peptide. An example is angiotensin-converting enzyme (also known as peptidyl-dipeptidase A MEROPS XM02-001), which plays an important role in the control of blood pressure by converting angiotensin I to angiotensin II. Peptidyl-dipeptidases are included in Enzyme Nomenclature sub-subclass 3.4.15. 

The —CO—NH - link shown in the red box is called a peptide bond, and each monomer used to form a peptide is called a residue. A typical protein is a polypeptide chain of more than a hundred residues joined through peptide bonds and arranged in a strict order. When only a few amino acid residues are present, we call the molecule an oligopeptide. The artificial sweetening agent aspartame is a type of oligopeptide called a dipeptide because it has two residues. 

To prevent insolubility resulting from uncontrolled aggregation of extended strands, two adjacent parallel or antiparallel yS-peptide strands can be connected with an appropriate turn segment to form a hairpin. The / -hairpin motif is a functionally important secondary structural element in proteins which has also been used extensively to form stable and soluble a-peptide y9-sheet arrangements in model systems (for reviews, see [1, 4, 5] and references therein). The need for stable turns that can bring the peptide strands into a defined orientation is thus a prerequisite for hairpin formation. For example, type F or II" turns formed by D-Pro-Gly and Asn-Gly dipeptide sequences have been found to promote tight a-pep-tide hairpin folding in aqueous solution. Similarly, various connectors have been... 

Proteins form in a sequence of condensation reactions in which the amine end of one amino acid combines with the carboxyl end of another, eliminating a water molecule to create an amide linkage. The amide group that connects two amino acids is called a peptide linkage, and the resulting molecule is known as a peptide. When two amino acids are linked, the product is a dipeptide. A dipeptide formed from alanine and glycine is shown in Figure 13-33. 

The oligomeric formulas are also known as chemically defined formulas. This class of formulas can be subcategorized based on whether the formula contains all free amino acids (elemental formulas) or peptides (peptide-based) as the protein source. Some of these formulas contain a combination of free amino acids and small peptides. Actually, dipeptides and tripeptides in these formulas are absorbed more efficiently than free amino acids. Oligomeric formulas may be better tolerated than polymeric formulas for patients with defects in GI function and maybe particularly useful in patients with severe pancreatic dysfunction or significantly decreased GI surface area (e.g., short bowel syndrome). 

Figure 34 Palladium(II) complexes act with different regioselectivity in cleaving dipeptides and proteins.

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