Easier Way to Convert Proteins into Crystals 92
Roland Piquepaille writes "As you might know, proteins need to be transformed into 3-D crystals before their atomic structures and their properties can be analyzed. And production of high quality crystals from proteins has been a difficult task until now. But scientists in the U.K. have successfully used a porous medium, or 'nucleant,' a material that encourages protein molecules to crystallize. Their first step towards 'holy grail' of crystallography could help speed up the development of new medicines and treatments."
Re:This is Big (Score:1, Interesting)
In structural biology, the x-ray crystallographers try to find out the exact 3-dimensional structure of a single protein. Since almost everything in the biochemistry of the human body works with proteins, they are a common target for drugs!
The problem in crystallization lies in the properties of the proteins themselves. They are flexible, dynamic, fragile little machines which SHOULD NOT crystallize in your cells (exactly this happens in diseases linked to prions). So they are very soluble in water. Researchers try to find the right conditions (salts, precipitants, etc.) to get them to build little crystals. Often, this process takes months or years.
This new technique will hopefully fasten it up!
Re:This is Big but not that big (Score:2, Interesting)
Or don't crystallize at all(!) (Score:3, Interesting)
The brilliance of x-ray sources are right now undergoing a revolution much faster than Moore's law.
Re:Ever hear of NMR structure determination? (Score:2, Interesting)
A friend, also doing a Ph. D in chemistry, has just binned half his thesis because the NMR data lead to one conclusion, only to be contradicted by the X-ray data. And this wasn't a small difference either...
Oh well, back to the lab then...
Re:Roland Piquepaille knows nothing. (Score:3, Interesting)
With most Protein Chemistry having the Px structure is the Gold Standard, and you can't really say you understand a protein until you have it. Trouble is, that as the article says, getting crystals is hard, slow, and extrodinarily painstaking work
crystallization is tough stuff (Score:3, Interesting)
It's pretty easy to understand why. Not only do you need pure protein, but one must find conditions under which that protein forms relatively large, single crystals. The chief variables, aside from the homogeneity of the protein you're starting off with, include temperature, pH, protein concentration, choice of and concentration of precipitant (generally a chemical that drives the protein out of solution), choice of and concentration of additive compounds, in some cases detergents... The researcher must traverse this multidemensional search space by trial and error, with a limited quantity of protein, looking for the optimal conditions. On top of that, the conditions that confer the ideal level of nucleation may not be ideal for crystal growth...
We have developed shortcuts over the past 20 years, or so. Kits are available that allow one to screen through frequently successful crystallization conditions. The number of conditions one can test in one go is gradually increasing, as things miniturize somewhat.
The ease-of-crystallization varies amazingly from one protein to another, and tricks that improve one do not necessarily work for another, but anything that simplifies the process will be greatly appreciated by the field.
Re:Understanding protein structure.. (Score:2, Interesting)
Re:crystallization is tough stuff (Score:3, Interesting)
Since X-rays cannot be lensed, the Fourier transform of the diffraction pattern (which is the Fourier synthesis of the ordered electrons in the crystal) requires knowing not only the intensities, a trivial task, but also the relative phase angle of each reflection. This is a problem with possible solutions on the order of 6^n, where n is the total number of unique reflections, or about 5-10,000 for an average macromolecular structure at 3 angstrom Bragg spacing, allowing for a +/- accuracy of 30 degrees for each phase angle. Current solutions rely on searching reciprocal space with similar known structures (Molecular Replacement) or several ab initio methods that require one or more heavy element derivatives of native crystals. The first approach only works for crystals where a very similar structure is already known and available to the investigator. The second approach requires further screening for heavy metals that bind in ordered sites in the crystal without significant alteration of the native lattice, then usually a trip to a tunable X-ray source at a synchrotron. This second approach can burn through an astounding number of crystals and investigator time. There are shortcuts such as making the protein with Seleno-methionine instead of methionine (selenium has a usable X-ray edge for phasing, unlike sulfur),but this is normally done after initial purification and crystallization have been optimized. For more reading on the phase problem, I'd recommend either Alexander McPherson or Jan Drenth's excellent introductory textbooks on macromolecular crystallography.
Probably gonna start a flamewar, but... (Score:3, Interesting)
I know this isn't a new idea. I don't have references handy to prove it isn't, I just know that I have read arguments about it. This theory is used to explain the origins of life (distinct from the theory of evolution). Basically, you have the whole "early earth molecular soup mix with electrical activity providing the spark-o-life" (Miller-Urey Experiment [wikipedia.org]), forming organic compounds, which are then (in some manner) "processed" by crystal structures forming later (?).
It makes me wonder if it wouldn't be possible to study crystals in a similar manner to see whether they could (in some manner) aid the formation of the organic compounds formed by the Miller-Urey (and other similar) experiments into early proteins or protein-like structures? Does anyone know if such a study has already been undertaken? Or, is this idea nothing more than baseless speculation with no foundation in reality? I am sincerely curious...
Re:Probably gonna start a flamewar, but... (Score:1, Interesting)
But whatever the method, the way to make proteins would almost certainly not occur on a naturally formed crystal of another protein. Protein crystals don't form easily, and it's doubtful that they'd ever get concentrated and pure enough in the wild to crystallize on their own.
Re:This is Not so Big (Score:3, Interesting)
You're not kidding. My favorite example is the fact that many crystallographers add diet coke to aid in crystallization.