Protein Related Question Please HELP You have a 9residue pep

Protein Related Question! Please HELP!

You have a 9-residue peptide hormone. The peptide initially does not react with Ellman\'s Reagent. However, after the peptide is treated with DTT (and the DTT is removed), addition of Ellman\'s Reagent generates a yellow signal. What does this tell you? When the peptide is treated with 1-fluorodinitrobenzene (FDNB, Sanger\'s Reagent), it reacts at a Cys residue. What does this tell you? When the peptide is treated with chymotrypsin, there is only one product. However, when the peptide is treated first with DTT and then with chymotrypsin, it fragments into two peptides. How is this possible? When the peptide is treated with carboxypeptidase it does not react. When the peptide is treated with DTT and then with chymotrypsin, the two fragments generated are IQNCPLG-NH2 and CY. You come to realize this means there is a chemical modification (an \"amide cap\") at the C-terminus. Using all the information from parts a-d, please draw the chemical structure of this 9-residue peptide. Follow the rules learned in class for peptide structures. The molecular mass of the 9-residue peptide hormone is 1007. Sketch a plausible mass spectrum for this molecule, showing a +1 and a +2 charge state. Label your axes, and the values for each peak. Use the internet to find out the common name of this hormone

Solution

fuuny question - on valentine day right

they are asking about female sex hormon-Oxytocine

oxytocine and vasopressin both are nano peptide but they are asking about oxytocine, on special day,

Oxytocinis a nonapeptide(containsnineaminoacids) oxytocin is neuro-hormone synthesizedby magnocellularneuronsthat locatedin supraoptic(SON) & paraventricularnuclei of hypothalamus.

oxytocine primary sequence of amino acide is- cys-tyr-lle-gln-asn-cys-pro-leu-gly- NH₂,

b)Dinitrofluorobenzene reacts to the amine group in the amino acids to produce the dinitrophenyl-AAs. DNP-amino acids moderately stablized under acid hydrolysis that break the peptide bonds. by using sanger reaction to determining the N-terminal amino acid in polypeptide chains. and FDNB reagent chemical use for polypeptide sequencing.

c) chymotrypsin is serin protease enzyme cleaves on aromatic amino acid C-terminal phenylalanine(F),Tryptophan(W),tyrosine(Y) on petide chain. when this peptide directly treated with chymotrypsin give only one product because of complex structure of peptide, but it’s treat with DDT- it fragments into two peptide because DDT break this peptide so it’s generate two fragment of peptide.

d)carboxypeptidase is protease enzyme cleaves peptide-bond at C-terminal end of protein, substrate of carboxypeptidase A is aromatic or aliphatic amino acid, carboxypeptidase cleave positively charge amino acide Arginine or lysine called carboxypeptidase B. a metallo- carboxypeptidase cleaves a C-terminal glutamate.

according to enzyme it’s possible to generate two fragment after treatment with carboxypeptidase.

amide cap at C-terminus on peptide of oxytocine, so DDT requied to break this cap than other enzyme enable to act on peptide to break the peptide bond in peptide residues, so that the possible fragment is generated