<p>Sorry for this very beginner homework question:</p>
<p>Which of the following linear peptides is consistent with Spectrum = {0 71 99 101 103 128 129 199 200 204 227 230 231 298 303 328 330 332 333}? (Select all that apply.)</p>
<pre><code>CTV

TCE

QCV

AQV

VAQ

TCQ
</code></pre>
<p>I tried to use the molecular weight to deduce the answer, but I failed.</p>
<pre class="lang-py prettyprint-override"><code>In [1]: from rdkit import Chem
   ...: from rdkit.Chem import Descriptors

In [2]: chemical_string = 'A'

In [3]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [4]: print( Descriptors.ExactMolWt(mol) )
89.047678464

In [5]: chemical_string = 'C'

In [6]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [7]: print( Descriptors.ExactMolWt(mol) )
121.019749464

In [8]: chemical_string = 'E'

In [9]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [10]: print( Descriptors.ExactMolWt(mol) )
147.053157768

In [11]: chemical_string = 'T'

In [12]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [13]: print( Descriptors.ExactMolWt(mol) )
119.058243148

In [14]: chemical_string = 'Q'

In [15]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [16]: print( Descriptors.ExactMolWt(mol) )
146.06914218

In [17]: chemical_string = 'V'

In [18]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [19]: print( Descriptors.ExactMolWt(mol) )
117.078978592

In [20]: 
<span class="math-container">```</span>
</code></pre>

CC BY-SA 4.0
2022-09-14T18:06:20.363Z
what kind of spectrum ??
pippo1980
CC BY-SA 4.0
2022-09-14T18:44:53.793Z
are you trying to accomplish what this server does ? https://iomics.ugent.be/ms2pip/
pippo1980
CC BY-SA 4.0
2022-09-25T02:34:57.020Z
@pippo1980 Someone told me the following: `The first six fragments are the dehydrated mass of each amino acid, so all tripeptides are "consistent". Then it makes no sense again. I think the question might be something like what combination of (cleaved) tripeptides would have dehydrated masses combined to make this set of masses. Then in the dipeptides, the TCE, QCV, VAQ are inconsistent`
kevin
CC BY-SA 4.0
2022-09-27T05:30:48.907Z
what does 'the dehydrated mass of each amino acid' means ? AA Mw - H2O Mw ? What about N-term-AA and C-term AA ?
pippo1980
CC BY-SA 4.0
2022-09-27T22:38:50.120Z
@pippo1980 what do you mean by `N-term-AA and C-term AA` ?
kevin
CC BY-SA 4.0
2022-09-27T22:39:34.517Z
@pippo1980 See the [mass composition analysis](https://i.imgur.com/vkZs26B.png)
kevin
CC BY-SA 4.0
2022-09-28T15:16:39.937Z
Alanine is 71 = 89 - H2O (18). What about N-term, C-term , first and last aa of polipeptide chain ?
pippo1980
CC BY-SA 4.0
2022-10-01T01:53:39.573Z
@pippo1980 I am not from chemistry background.  May I ask what `N-term, C-term , first and last aa` means ?
kevin
CC BY-SA 4.0
2022-10-01T07:56:00.403Z
The free amine end of the chain is called the “N-terminus” or “amino terminus” and the free carboxylic acid end is called the “C-terminus” or “carboxyl terminus, from google could be incorrect
pippo1980
CC BY-SA 4.0
2022-10-02T03:14:07.383Z
@pippo1980 okay, but how does that help to solve this question ?
kevin
CC BY-SA 4.0
2022-10-02T06:17:08.640Z
Was wondering about your mass composition analysis weight, like N e C term AA weights are missing, unless your machine has a resolution power that cannot distinguish that weights differences
pippo1980
<phylogenetics><homework>
Relationship between molecular weight and linear peptide
# Relationship between molecular weight and linear peptide

(Asked by: username_0 on 2022-09-11)

Sorry for this very beginner homework question:
Which of the following linear peptides is consistent with Spectrum = {0 71 99 101 103 128 129 199 200 204 227 230 231 298 303 328 330 332 333}? (Select all that apply.)
CTV

TCE

QCV

AQV

VAQ

TCQ

I tried to use the molecular weight to deduce the answer, but I failed.
In [1]: from rdkit import Chem
   ...: from rdkit.Chem import Descriptors

In [2]: chemical_string = 'A'

In [3]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [4]: print( Descriptors.ExactMolWt(mol) )
89.047678464

In [5]: chemical_string = 'C'

In [6]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [7]: print( Descriptors.ExactMolWt(mol) )
121.019749464

In [8]: chemical_string = 'E'

In [9]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [10]: print( Descriptors.ExactMolWt(mol) )
147.053157768

In [11]: chemical_string = 'T'

In [12]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [13]: print( Descriptors.ExactMolWt(mol) )
119.058243148

In [14]: chemical_string = 'Q'

In [15]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [16]: print( Descriptors.ExactMolWt(mol) )
146.06914218

In [17]: chemical_string = 'V'

In [18]: mol: Chem.Mol = Chem.MolFromFASTA(chemical_string)

In [19]: print( Descriptors.ExactMolWt(mol) )
117.078978592

In [20]: 
```

**Tags:** phylogenetics, homework
> **Comments:**
> **username_1**: what kind of spectrum ??  
> **username_1**: are you trying to accomplish what this server does ? https://iomics.ugent.be/ms2pip/  
> **username_0**: @pippo1980 Someone told me the following: `The first six fragments are the dehydrated mass of each amino acid, so all tripeptides are "consistent". Then it makes no sense again. I think the question might be something like what combination of (cleaved) tripeptides would have dehydrated masses combined to make this set of masses. Then in the dipeptides, the TCE, QCV, VAQ are inconsistent`  
> **username_1**: what does 'the dehydrated mass of each amino acid' means ? AA Mw - H2O Mw ? What about N-term-AA and C-term AA ?  
> **username_0**: @pippo1980 what do you mean by `N-term-AA and C-term AA` ?  
> **username_0**: @pippo1980 See the [mass composition analysis](https://i.imgur.com/vkZs26B.png)  
> **username_1**: Alanine is 71 = 89 - H2O (18). What about N-term, C-term , first and last aa of polipeptide chain ?  
> **username_0**: @pippo1980 I am not from chemistry background.  May I ask what `N-term, C-term , first and last aa` means ?  
> **username_1**: The free amine end of the chain is called the “N-terminus” or “amino terminus” and the free carboxylic acid end is called the “C-terminus” or “carboxyl terminus, from google could be incorrect  
> **username_0**: @pippo1980 okay, but how does that help to solve this question ?  
> **username_1**: Was wondering about your mass composition analysis weight, like N e C term AA weights are missing, unless your machine has a resolution power that cannot distinguish that weights differences  

---

## 0 answers

