 |
 |
Hi Peter, I don't have access to the paper from here, but the abstract implies that the H+ is attached to a cysteine sulphur. In that case it have the shared electrons to scatter X-rays. The text "a proton (H+) attached to the sulphur of a cysteine ligand" is not very pretty. I would call it a hydrogen atom in this context, or I would at least leave out the '(H+)'. Perhaps the full paper is clearer. Cheers, Robbie > -----Original Message----- > From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of > Peter Moody > Sent: Monday, February 02, 2015 14:08 > To: [log in to unmask] > Subject: [ccp4bb] proton scattering by X-rays > > Dear BB > > > > > I have (again) realised how limited by understanding of our subject is. > > > > > In Nature’s online site > http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14110.ht > ml?WT.ec_id=NATURE-20150129 there is a paper describing an X-ray > structure determined with sub-atomic data (nice!). The figures show density > for H+ as well as H-. In my simple way I had assumed that any X-ray scattering > from the nucleus was negligible, and that the electrons are responsible for > this. I would expect a proton (i.e. H+) alone to be invisible to X-rays, and > certainly not to look similar to a hydride (with two electrons in (electron > density) maps. What have I missed? Could someone please explain, or point > me to a suitable reference? > > > > > Best wishes, Peter > > > (please use [log in to unmask] to reply directly) > > > http://www2.le.ac.uk/departments/biochemistry/staff/moody >