[lucaluca]

Could you please help to identify the chemical behind this tatoo? Thanks.

[Borek]

It is a peptide - try to identify amino acids and then google for the list of abbreviations. Peptide page has an example in the upper right corner.

[lucaluca]

Thanks, I will read these pages.

I wonder someone would make a tatoo with a peptide? I whish I asked her at that time.

[Archer]

Maybe she discovered it, could be a medicinal natural product.

Looks like a macrocyclic peptide with a disulphide bridge, some of it is obscured so it will be hard to identify.

[Corribus]

I'm fairly sure it's oxytocin.

http://en.wikipedia.org/wiki/Oxytocin

[Archer]

I'm fairly sure it's oxytocin.

Well spotted, I agree.

What you can see of it matches the structure on wiki exactly, down to the orientation of the groups and inclusion of the unecessary explicit hydrogen in the isoleucine residue.

[lucaluca]

Yep, agreed. Now the question is, why a tatoo of Oxytocin?

[Arkcon]

Well, its an important hormone, attached to a number of biological processes, and implicated in a number of new interesting topics -- form lactation to wound healing to autism:  http://en.wikipedia.org/wiki/Oxytocin#Actions

On the other hand, why does anyone get any tattoo?  Basically, we're all now aware that they've sat still and been needle pricked thousands of times to get the ink into place.  As to what it all means to them, well, you really should have asked at the time.

[Corribus]

They do call it the "hormone of love", so...?

While I wish I could say I knew the structure instantly, to identify it I used Harvard's handy peptide database. You can just enter the sequence (using single letter codes) and it will spit any peptide out that matches.  I couldn't see the tyrosine very well, so I just put in the first five (in reverse order, QNCPLG) and oxytocin was what it spat out.

Nice link to bookmark:
http://pepbank.mgh.harvard.edu/