Peptides sequence determination

Mass spectral fragmentation patterns of alkyl and phenyl hydantoins have been investigated by means of labeling techniques (28—30), and similar studies have also been carried out for thiohydantoins (31,32). In all cases, breakdown of the hydantoin ring occurs by a-ftssion at C-4 with concomitant loss of carbon monoxide and an isocyanate molecule. In the case of aryl derivatives, the ease of formation of Ar—NCO is related to the electronic properties of the aryl ring substituents (33). Mass spectrometry has been used for identification of the phenylthiohydantoin derivatives formed from amino acids during peptide sequence determination by the Edman method (34). 

Part 2. Mass spectrometry in amino-acid and peptide analysis and in peptide sequence determination... 

The peptide sequence determination can be preceded via stepwise (cyclic) degrada-tion/identification of N-terminal residues or C-terminal residues. This is accomplished by either chemical or enzymatic methods. 

Peptide Sequence Determination Using Mass Spectrometry... 

Neutral Loss-Driven MS This triggers additional fragmentation of the dominant and specified NL-associated peak observed in the MS/MS scan. It results in the generation of more fragment ions for accurate peptide sequence determination. MS spectra are helpful when peptide backbone cleavage by MS/MS is inefficient. 

The Golgi apparatus consists of a stack of membrane sacs and associated vesicles. It is an extension of the ER. Transfer vesicles transport the proteins issued from the ER to the sacs of the Golgi apparatus. The Golgi apparatus has a dual function. It is responsible for the glycosylation of protein, then sorts so as to direct them via specialized vesicles either into the vacuole or into the plasmic membrane. An N-terminal peptidic sequence determines the directing of proteins towards the vacuole. This sequence is present in the precursors of two vacuolar-orientated enzymes in the yeast Y carboxypeptidase and A proteinase. The vesicles that transport the proteins of the plasmic membrane or the secretion granules, such as those that transport the periplasmic invertase, are still the default destinations. 

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