Primary structures, of peptides

Fig. 1.1 Comparison of the primary structure of peptide and peptoid oligomers...

The primary structure of peptides (oligopeptides and polypeptides) is described as a linear sequence consisting of the 20 naturally occurring L-amino acids. These amino acids are linked together by amide bonds. Fig. 33 illustrates this for the pentapeptide Leu-enkephalin. 

Following the isolation and characterization of a peptide, procedures for its quantitative analysis in physiological and pharmacological studies must be sentitive and specific. Since there are frequently species variations in the primary structures of peptides, it is necessary to isolate the analogous peptide from the same species in which it is to be assayed. Chemical analysis offers a degree of specificity beyond that provided by bicassay or radioimmunoassay, but it must be applicable at the physiological level of laboratory animals. 

Confirmation of the primary structure of peptides and proteins generated using recombinant DNA was rapidly identified as an important application. Indeed, using a magnetic sector instrument, accurate mass measurements could be carried out. In an early case using peak matching and a resolution of 10000 the mass of a recombinant octapeptide... 

In the remainder of this chapter, we will describe the main features of peptide and protein structure. We will first examine what is called the primary structure of peptides and proteins that is, how many amino acids are present and what their sequence is in the peptide or protein chain. We will then examine three-dimensional aspects of peptide and protein structure, usually referred to as their secondary, tertiary, and quaternary structures. 

We have seen how the primary structure of peptides and proteins can be determined and how peptides can be synthesized in the laboratory. Now let us examine some further details of protein structure. 

FIG. 1 Primary structure of peptides corresponding to the N-terminal of 23 residues of ttsi-casein. Hydrophobic amino acids are shown by closed circles, hydrophilic charged amino acids by open circles, and hydrophilic uncharged amino acids by shaded... 

Reaction with phenyl isothiocyanate (Edman degradation) has been of great significance in determining the primary structure of peptides. 

A benefit of peptide synthesis is that one can easily fine tune amino acid content (i.e. primary structure) of peptides to customize final molecular conformations, gelation times, or other molecular interactions. This allows the creation of an array of peptides with minute differences in sequences but vast differences in final properties. Characterization is important to understanding the secondary structures formed by individual peptides and, consequently, the higher order structures that are formed during gelation. To confirm and characterize second order stracture, two spectroscopic methods, circular dichroism spectroscopy (CD) and Fourier-transform infrared spectroscopy (FUR) are frequently used. Both methods examine light absorption... 

TABLE 5.6 Primary Structures of Peptides with Growth Hormone Releasing Activity... 

Tosteson, M.T., Alvarez, O., Hubbell, W., Bieganski, R.M., Attenbacher, C., Caporale, L.H., Levy, J.J., Nutt, R.F., Rosenblatt, M., and Tosteson, D.C., 1990, Primary structure of peptides and ion channels -Role of amino acid side chains in voltage gating of melittin channels. Biophys. J. 58 1367-1375. 

The primary structure of a peptide is its ammo acid sequence We also speak of the secondary structure of a peptide that is the conformational relationship of nearest neighbor ammo acids with respect to each other On the basis of X ray crystallographic studies and careful examination of molecular models Linus Pauling and Robert B Corey of the California Institute of Technology showed that certain peptide conformations were more stable than others Two arrangements the a helix and the (5 sheet, stand out as... 

The primary structure of a peptide is given by its ammo acid sequence plus any disulfide bonds between two cysteine residues The primary structure is determined by a systematic approach m which the protein is cleaved to smaller fragments even individual ammo acids The smaller fragments are sequenced and the mam sequence deduced by finding regions of overlap among the smaller peptides... 

The folding of a single polypeptide chain in three-dimensional space is referred to as its tertiary structure. As discussed in Section 6.2, all of the information needed to fold the protein into its native tertiary structure is contained within the primary structure of the peptide chain itself. With this in mind, it was disappointing to the biochemists of the 1950s when the early protein structures did not reveal the governing principles in any particular detail. It soon became apparent that the proteins knew how they were supposed to fold into tertiary... 

The primary structure of a protein is the sequence of residues in the peptide chain. Aspartame consists of phenylalanine (Phe) and aspartic acid (Asp), and so its primary structure is Phe-Asp. Three fragments of the primary structure of human hemoglobin are... 

Fig. 1 Primary structure of human tropoelastin isoform 3 (EBI accession no. P15502). The highlighted regions correspond to the signal peptide and hydrophobic and hydrophilic domains. Based on [2]...

Peptides are named for the number of amino acid residues present, and as derivatives of the carboxyl terminal residue. The primary structure of a peptide is its amino acid sequence, starting from the amino-terminal residue. 

The primary structure of a polypeptide is its sequence of amino acids. It is customary to write primary structures of polypeptides using the three-letter abbreviation for each amino acid. By convention, the structure is written so that the amino acid on the left bears the terminal amino group of the polypeptide and the amino acid on the right bears the terminal carboxyl group. Figure 13-35 shows the two dipeptides that can be made from glycine and serine. Although they contain the same amino acids, they are different molecules whose chemical and physical properties differ. Example shows how to draw the primary stmcture of a peptide. 

Pellequer, J. L., Westhof, E. andVanRegenmortel, M. H. V. (1994), Epitope prediction from primary structure of proteins , in G. B. Wisdom (Ed.), Peptide Antigens A Practical Approach, IRL Press, Oxford, UK, pp. 7-25. 

Proteins are built up by aminoacids linked by peptide bonds into a polypeptide chain (Figure 2). The sequence of the aminoacids in the chain is known as the primary structure of the protein. The primary structure of the protein gives rise to the corresponding three-dimensional structure, and the spatial relationships of the constituents are the key for the peptide function. 

Heller, E., Kaczmarek, L. K., Hunkapiller, M. H., Hood, L. E., and Strumwasser, F. (1980) Purification and primary structure of two neuroactive peptides that cause bag cell afterdischarge and egg laying in Aplysia. Proc. Natl. Acad. Sci. USA, 77 2328-2332. 

The primary structure of a protein is the linear sequence of amino acids linked by peptide bonds. The structural heirarchy of proteins is as follows. 

The amino group of the N-terminal amino acid residue of a peptide will react with the FDNB reagent to form the characteristic yellow DNP derivative, which may be released from the peptide by either acid or enzymic hydrolysis of the peptide bond and subsequently identified. This is of historic interest because Dr F. Sanger first used this reaction in his work on the determination of the primary structure of the polypeptide hormone insulin and the reagent is often referred to as Sanger s reagent. 

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