finding GFP's mass

Sergio sergioal at bbm1.ucm.es
Wed Apr 11 10:20:51 EST 2001



Frederic Langlois wrote:

> [...]

> 2) Then I searched many databanks and found GFP's amino acid sequence. I
> used this equation to find GFP's mass:
>
> mass = [(n1*molecular
> weight1)+(n2*mol.weight2)+...(n20*mol.weight20)]/[(n1+n2+...n20-1)*33g/mol]
>
> where 1=glycin; 2 to 20= all the other amino acids
>       n=the sum of the amino acids of each kind
>       33g/mol=a water molecule's molecular weight (approximately)
>
> I substrated the water molecules that are "lost" when the peptidic bonds are
> made.
>
> I converted the molecular weight in Dalton units...
>

I don't understand why do you divide by (n1+n2...+n20-1)*33g/mol
being N the total aa numer:  (n1+n2...n20-1) = N-1
and 18 g/mol the water MW,

the correct formula is to SUBTRACT  (N-1)*18, not divide by it...

Sergio






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