A nonapeptide was determined to have the following amino acid composition: (Arg)2, (Gly)2, (Phe)2, His, Leu, Met.
1-fluoro-2,4-dinitrobenzene (FDNB) reacts with free amino (but not amido or guanidino) groups in proteins to produce dinitrophenyl (DNP) derivatives of amino acids.
The native peptide was incubated with 1-fluoro-2,4-dinitrobenzene (FDNB) and then completely hydrolyzed; 2,4-dinitrophenylhistidine was identified by HPLC. What does this tell you about the peptide sequence?
When the native peptide was exposed to cyanogen bromide (CNBr), an octapeptide and free glycine were recovered. What does this tell you about the peptide sequence?
Incubation of the native peptide with trypsin gave a pentapeptide, a tripeptide, and free Arg.The peptides were separated and treated with FDNB. 2,4-Dinitrophenyl-histidine was recovered from the pentapeptide, and 2,4-dinitrophenylphenylalanine was recovered from the tripeptide.What does this tell you about the peptide sequence?
Digestion with the enzyme pepsin produced a dipeptide, a tripeptide, and a tetrapeptide. The tetrapeptide was composed of (Arg) 2, Phe, and Gly. What does this tell you about the peptide sequence?
What is the sequence of the nonapeptide?
the nonapeptide sequence is His-Leu-Phe-Gly-Lys-Lys-Phe-Met-Gly
the above person is wrong. he googled the question and pasted the first answer he saw. the Lys will be replaced by arg
Based on the information provided, we can deduce the following about the peptide sequence:
1. The presence of 2,4-dinitrophenylhistidine from the reaction with FDNB tells us that the peptide contains at least one histidine residue.
2. Cyanogen bromide (CNBr) cleaved the peptide into an octapeptide and free glycine. This suggests that the peptide sequence contains a peptide bond that can be cleaved by CNBr, resulting in the release of an octapeptide and glycine.
3. Trypsin digestion of the native peptide produced a pentapeptide, a tripeptide, and free arginine. The recovery of 2,4-dinitrophenyl-histidine from the pentapeptide and 2,4-dinitrophenylphenylalanine from the tripeptide indicates the presence of histidine and phenylalanine residues in the peptide sequence.
4. Pepsin digestion of the native peptide yielded a dipeptide, a tripeptide, and a tetrapeptide. The tetrapeptide composed of (Arg)2, Phe, and Gly indicates the presence of two arginine residues, one phenylalanine residue, and one glycine residue in the peptide sequence.
From the information provided, we can determine the sequence of the nonapeptide as follows:
(Arg)-Gly-(Arg)-Gly-(Phe)-His-Leu-Met.
To answer these questions, we need to understand the reactions and methods used in each experiment. This will allow us to deduce information about the peptide sequence.
1. Reaction with FDNB and identification of 2,4-dinitrophenylhistidine:
In this experiment, FDNB reacts with free amino groups in proteins to produce dinitrophenyl (DNP) derivatives of amino acids. If 2,4-dinitrophenylhistidine was identified by HPLC, it means that there was a histidine residue in the peptide sequence.
2. Reaction with CNBr and recovery of an octapeptide and free glycine:
Cyanogen bromide (CNBr) cleaves peptide bonds at the C-terminal side of methionine residues. If an octapeptide and free glycine were recovered, it suggests that the peptide contained a methionine residue followed by the octapeptide sequence.
3. Incubation with trypsin and recovery of a pentapeptide, a tripeptide, and free Arg:
Trypsin is a proteolytic enzyme that cleaves peptide bonds specifically after arginine and lysine residues. In this experiment, the presence of a pentapeptide, a tripeptide, and free Arg indicates that the nonapeptide contained an arginine residue followed by the pentapeptide, then the tripeptide sequence.
4. Digestion with pepsin and recovery of a dipeptide, a tripeptide, and a tetrapeptide:
Pepsin is another proteolytic enzyme that cleaves peptide bonds specifically after aromatic amino acids. The tetrapeptide composed of (Arg)2, Phe, and Gly suggests that the peptide sequence contained two consecutive arginine residues followed by a phenylalanine residue, and then glycine.
Now, let's combine the information obtained from these experiments to deduce the sequence of the nonapeptide:
From experiment 1: There is a histidine residue.
From experiment 2: The sequence starts with a methionine followed by an octapeptide.
From experiment 3: The sequence contains two consecutive arginine residues, followed by a pentapeptide and then a tripeptide with free arginine.
From experiment 4: There are two consecutive arginine residues, followed by a phenylalanine residue and then a glycine residue.
Putting all the information together, the sequence of the nonapeptide is:
Met-(Arg)2-Pentapeptide-Tripeptide-(Arg)2-Phe-Gly-His-Leu