OK the title is a little misleading as I suspect that a Mega Dalton is simply a way of counting the overall size of something, when you don't know what all the constituent parts are? Is this correct? I mean looking it up on Wikipedia it says it says one Dalton is equivalent to the mass of one proton. Which is fair enough. So if a protein was one million Daltons in size (or one mega Dalton), that would just mean that it contains overall one million protons? (These are questions BTW).

 

However the question is if this is correct, why is the Dalton used over any other measure in biology, how is it calculated and how is it denoted?

 

Thanks!

OK the title is a little misleading as I suspect that a Mega Dalton is simply a way of counting the overall size of something, when you don't know what all the constituent parts are? Is this correct? I mean looking it up on Wikipedia it says it says one Dalton is equivalent to the mass of one proton. Which is fair enough. So if a protein was one million Daltons in size (or one mega Dalton), that would just mean that it contains overall one million protons? (These are questions BTW).

 

However the question is if this is correct, why is the Dalton used over any other measure in biology, how is it calculated and how is it denoted?

 

Thanks!

 

Huh, never knew it was called a Dalton. I always just used atomic mass unit or proton mass (although I guess this last is not exactly the same).

 

It's a unit of mass. Just like a kilogram or ounce, but it's a convenient size for molecules and similar sized things.

 

If a protein is 1MD in mass, then it has 1 million nucleons (protons or neutrons).

If a protein is 1MD in mass, then it has 1 million nucleons (protons or neutrons).

careful, at that many daltons the cumulative mass of the electrons starts to become significant. roughly 1kDa would be down to electrons alone.

careful, at that many daltons the cumulative mass of the electrons starts to become significant. roughly 1kDa would be down to electrons alone.

 

Good point, although technically I only quoted one sig fig

But yes, the electrons could become quite important if you were doing precise work.

Dalton is synonymous to atomic mass unit (1/12 of 12C) as mentioned, this is not precisely the same as the mass of a proton (and with increasing mass the error become bigger). Again, it is a measure of mass, not size.