[gregcc]

Hey guys, im trying to work out how much of a molecule is in a gram of an amino acid,for example glycine and alanine. I looked up the molecular mass of these amino acids and have found multiple measures for them.

For example on this link it shows mass of amino acid residue, if i ordered amino acid powder such as l-glycine would those crystals be the residue?

http://www.matrixscience.com/help/aa_help.html

So just as an example if i wanted a 50/ 50 ratio of glycine and alanine according to this i would need to have less than a gram of glycine if having a gram of alanine due to more molecules of glycine being in a gram.. is my thinking correct?

Appreciate any help i can get on this.

[Babcock_Hall]

Your thinking sounds qualitatively OK, but your table is not for free amino acids.  Instead it is for amino acid residues as they would be in a polypeptide.  They are all less than the values for the free acids because when you polymerize amino acids, you also create water from elements within each amino acid.

[Borek]

Besides, without explicitly stating what is meant by 50/50 it is not clear what you mean. It can mean 1 mole/1 mole, it can mean 1 g/1 g.

[gregcc]

Thanks for the replies, sorry for my unclear question. What i would really like to figure out is how many molecules of glycine are in 1 gram of l-glycine powder, and how would i work that out. Thanks

[Borek]

First step would be to find the molar mass from its chemical formula.

[gregcc]

http://www.promega.co.uk/~/media/Files/Resources/Technical%20References/Amino%20Acid%20Abbreviations%20and%20Molecular%20Weights.pdf

Alanine 89Da
Arginine 174Da
Aspargine 132Da
Aspartic Acid 133Da
Cysteine 121Da
Glutamine 146Da
Glutamic Acid 147Da
Glycine 75Da
Histidine 155Da
Isoleucine 131Da
Leucine 131Da
Lysine 146Da
Methionine 149Da
Phenylalanine 165Da
Proline 115Da
Serine 105Da
Threonine 119Da
Tryptophan 204Da
Tyrosine 181Da
Valine 117Da

I tried to calculate it this way, but am unsure if its correct.
1.
I divided the Molar Mass by the smallest molar mass, glycine.
Column C/ 75

2.
I multiplied the result from step 1 by with the percentage of the substance i want, Ie.
Alanine step 1 equals 1.18666, I multiplied this number by 6.97. I want my overall mixture to be 6.97% Alanine.

Is this correct reasoning? The results are below

[gregcc]

It does not show the image for some reason but when i right clicked and selected open in new tab it seemed to work.

[Babcock_Hall]

The table you just presented is correct, but the final result looks wrong.  Are you trying to achieve an equal number of moles of alanine versus glycine?

[gregcc]

on the table alanine and glutamic acid are the closest and would like to achieve the same number of moles, i worked it out as 1.65 grams of l-alanine would equal to the same number of moles as 2.72 grams of glutamic acid.

Is that correct? If it is then the rest of the table should hopefully be right.

[Babcock_Hall]

Your calculation is correct.  The table that you previously presented was correct, but it was not the information that you needed.

[gregcc]

Your calculation is correct.  The table that you previously presented was correct, but it was not the information that you needed.

Sorry I do not follow, which information was incorrect? The molar mass of amino acids ? Thanks!

[Babcock_Hall]

The masses in the table from Matrix Science in the link below (which you posted some time ago) are the masses of amino acid residues within a polypeptide.  They are about 18 units below the masses of the free amino acids. This reflects the loss of water when a peptide bond is formed from two amino acids.
http://www.matrixscience.com/help/aa_help.html