As has been often noted about a number of topics, one’s biases will always skew one’s perspective.

On the one hand, we have this very interesting paper where the authors suggest correlated motions in ubiquitin over a distance of ~ 15 Angstroms (1.5 nm) based on further squeezing information from previously acquired NMR data with the help of computational methods. On the other hand, there is this other very intriguing paper where the authors put forth using gadolinium tags as a way to obtain structural constraints in proteins on the order of ~ 6 nm (60 Angstroms) via ESR/EPR techniques.

In the former, we’re looking at proposed long-distance correlations based on a bunch of relatively weak, short-range interactions (NOEs and RDCs), while in the latter we have nanometer-scale distance constraints being derived from a technique that is well matched to determining distances at the nanoscale. I figure the astute reader can figure where I stand on each given my tone.

Suffice it to say, it’s the reason why I’ve recently developed an interest in ¹⁹F NMR (oh, to work with a nucleus that has a decent gyromagnetic ratio and isn’t as common as protons in biological materials!), for one, as well as metal binding tags for paramagnetic relaxation enhancement studies.

In other news, my resolution for the second half of 2011 is to always try and work in a mention of the Helmholtz free energy into each discussion I am involved in that touches upon thermodynamics, as I think far too many chemists have gotten comfortable in their Gibbsian-oriented world.

I suppose this is one of those “it was bound to happen” things – one of the summer undergraduates who is in my lab at my current institution mentioned that the undergrad biochem lab uses a hexahistidine-tagged protein for overexpression & purification. I of course remember having to prep and subsequently grind up giant amounts of animal muscle to extract a protein in my undergrad biochem lab. I feel slightly dusty.

With that observation, I will call this blog post to an end. Read more!

Clusters of Spins (AKA the Promised NMR Lit Post)

So, here's the citation-heavy post about some interesting work done on systems of primarily – but not exclusively – biological interest via magnetic resonance spectroscopy since the turn of the century (I've always wanted to say that).


I mentioned CERM at the University of Florence in my last post for good reason – it's something of a place where, sooner or later, all paths seem to cross there in one way or another. It's either having read one of the texts that's come out of the faculty there, collaboration, or you just find inspiration in what they're doing. Because I have a certain unavoidable bias towards ssNMR out of (most likely) residual Stockholm Syndrome, I will mention this paper as an example of extending the work done at Florence in using NMR to understand paramagnetic metalloproteins in solution to the solid state.

Lyndon Emsley and coworkers at ENS-Lyon are pursuing a number of really interesting projects in magnetic resonance, both of basic importance to NMR (see, for instance, this paper) as well as to problems in chemistry, metabonomics, biology, and paramagnetic systems.

Paul Ellis & coworkers at PNNL have done some really stunning work with Zn-67 ssNMR and Mg-25 ssNMR. Zinc is one of the most common metal cofactors found in biology, and they've managed to do direct measurements of zinc in proteins via solid state NMR (see here and here for examples). Given that it's a quadrupolar nucleus, it's even more awesome. (While comments noting that they do this sort of work at really low temperature are accurate, it does not diminish its luster.) Magnesium-25 is another nucleus that this group has focused on as of late. See this paper for some Mg-25 ssNMR. The applications to half-integer quadrupolar nuclei in general, as well as their efforts in developing low-temperature ssNMR methods, are of interest in general and not just for biological systems.

Dieter Suter and his group at Dortmund have done some really neat things with optically-detected magnetic resonance, including metalloprotein research and their work on NMR of quantum wells. You can read more at their webpage here Fortunately for all of us, you can find a number of publications here. Suter was also involved in the Pines' group work on geometric phases in the late 1980s, so if you love it when interesting theory and experiment comes together, it should bring a smile to your face.

The Jaroniec group at Ohio State has been doing a variety of interesting things in solid state NMR, but I will mention their work with spin-labeled proteins here since it most tickles my fancy. You can read about it here, where they used spin-labeled proteins to obtain long-range structural constraints. Another advantage of spin-labeling is in facilitating assignment of congested NMR spectra – since you know where you introduce your spin label, you could potentially “blank out” certain residues that crop up in these congested regions to simplify assignments.

This is by no means a comprehensive list or thorough assessment of the field, more just intended to whet one's appetite. I would also like to point out the lecture notes from a solid state NMR workshop for graduate students and postdocs here. It may be a bit much to take in all at once, but some of you may find it makes for interesting reading despite not having a chance to hear the actual lecture. (FYI – no, I did not attend this workshop.) The list of speakers is a lineup of some of the major players in (biological) solid state NMR in the United States. If one's curiosity is still rampant, and you wish to expand your geographical purview, here is a list of lecture notes from a European ssNMR school (which, in case you're trying to pin me down, I did not attend) taught by a number of the major names in ssNMR in Europe. While I've long since downloaded these files and saved them, I can't guarantee that all lecture notes are still functional.

FYI - If I didn't mention you or your advisor or past advisor, I really didn't mean to do so. I would be pretty sure you've done/are doing awesome work, it's just that this is not a detailed journal club-style post. I will take recommendations, though, for any possible "journal club"-style posts, where the focus is on a single article or group of related articles. Tell me what totally BAMF science you've done, I'd love to hear it!
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