Peptides primary structure elucidation

Fig. (1). Peptidomics strategies used to study Drosophila immunity. (A) Using antimicrobial assays (antibacterial and antifungal), the bioactive peptides were isolated from the blood of bacteria-challenged Drosophila. MS was used for molecular mass assignment, to identify post-translational modifications, and for primary structure elucidation (B) Identification of peptidic immune effectors through differential display analysis (DD) by MALDI-MS and micro/nano RP-HPLC coupled (online) or not (off-line) to ESI-MS. When the HPLC was performed off-line to the mass spectrometer, fractions were individually analyzed by MALDI-MS. The identification and the structural characterization were performed either by molecular mass assignment and/or sequencing by ESI-MS/MS.

One of the first tasks in elucidating the primary structure of a protein is to determine its amino acid content. To accomplish this, the protein must first be hydrolyzed to break the peptide linkages. This is generally accomplished with 6... 

Proteins are macromolecules with different levels of structural organization. The primary structure of proteins relates to the peptide bonds between component amino acids and also to the amino acid sequence in the molecule. Researchers have elucidated the amino acid sequence in many proteins. For example, the amino acid composition and sequence for several milk proteins is now well established (Swaisgood 1982). 

The elucidation of the primary structures of proctolin (22) and AKH (2Q), signaled the beginning of the structural identification of insect neuropeptides. These relatively small peptides (pentapeptide proctolin and decapeptide AKH) remained the only known insect peptide sequences for a number of years until, in the early 1980 s, accumulated technical advances in peptide isolation and microsequencing techniques facilitated the analysis of insect peptides (8-12 ... 

Mass spectrometry has been applied to the structure elucidation of peptides and proteins for some time. Depending on the problem, it is used as both a primary and a complementary technique and although many difficulties still remain it is now an established means of determining amino acid sequences. As instrumental methods and new derivatives have developed, the different approaches employed, with particular combinations of chemical pretreatment and sample introduction to the MS, have been dictated by the size and type of the peptide and the information required. 

Schistomyotropins (Scg-MT), neuropeptides from the CNS of the desert locust Schistocerca gregaria). The peptides were isolated from the methanolic extract of about 7000 brains of these insects. The primary structures were elucidated as follows schistomyotropin-1 (Scg-MT-1)... 

D.M. Desiderio, The elucidation of primary structure of oligopeptides of biological importance via mass spectrometry. Proc. of the Second Amer. Peptide Symp. (Gordon and Breach, New York) 1972, pp. 159-168... 

The primary structure of P. is elucidated by the standard methods of sequence analysis (see Proteins). The conformation of P. is an important determinant of their biological activity. It is stabilized by peptide and disulfide bonds In P. containing unusual bonds and/or constituents other factors also stabilize the conformation. Although X-ray crystallography (see) was used in the elucidation of the three-dimensional structures of insulin and gramicidin S, the conformational analysis of P. is now by preference carried out in solution, using the spectroscopic methods ORD, CD, IR, NMR and ESR. 

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