Growing a crystal of a protein often starts by mixing a solution of protein with a solution of a salt. If you imagine sitting on a point that starts in the protein solution, as mixing occurs protein diffuses away into the salt solution and is diluted, so the protein concentration decreases, while as the salt arrives, the salt concentration increases. This means that in a plot with the x-axis the salt concentration, and the y-axis the protein concentration, the concentrations at the point move down and to the right. It will start at the point marked above by the blue circle, and finish at the magenta circle. If the mixing is just diffusion of the protein and salt, and if they diffuse equally fast, the point will follow the path of the straight dashed-red line above. But if protein diffuses much slower (which it does) and there is flow of the solutions (almost unavoidable except for the smallest volumes*) the point should follow the path of the dashed black line — this is a very different path of course.
I am at a conference in Sorrento, Italy. My hotel room is described as having a ‘hill view’, and as you can see from this picture taken from my hotel room, the description is accurate. That is a genuine Italian hill. In Sorrento, I will be talking about my work on paint drying, but I have a bit of time before the conference sessions start. So, I am also working on a course I am teaching next month for the EU network on RAtionalising Membrane Protein crystallisation (RAMP).
I spent part of this week at the kick-off meeting for an EU-funded PhD training network: Engineered Calcium-Silicate-Hydrates for Applications (ERICA for short). The network is run from Surrey and I was invited along to give a talk, and to help out. These calcium-silicate-hydrates are better known as cement. Cement is, very roughly speaking, a type of artificial stone in the sense that when poured it crystallises to form a semi-crystalline solid. The world’s most widely used construction material, concrete, is basically cement plus gravel filler. Concrete is not the most glamorous, but it is strong and above all it is cheap, less than £100 for a ton.
I would to start this post by acknowledging how impressed I am with the style of the French guy who strode confidently onto Friday’s flight from Bordeaux to London wearing a large string of cloves of garlic draped around his neck. Some people just have natural style. As someone who does not, I am a bit envious. My PhD student and I were in Bordeaux as part of an EU research network (called RAMP) on crystallising proteins. There is a research lab in the suburbs of Bordeaux that is world leading at what is called microfluidics — essentially plumbing but instead of pipes centimetres across that move litres, microfluidics has pipes that are less than 1 millimetre wide and move as little as billionth of a litre, a nanolitre. The channels above in the microfluidic device shown above are only 0.15 mm wide.
Over the last six months I have been thinking a lot about the movement of small solid particles in liquids, but a couple of weeks ago I came across examples, that were new to me, of the reverse. The motion of liquid droplets or gas bubbles in solids. I think they are fascinating. One example of liquid droplets moving inside a solid, are pockets of brine (i.e., salty water) moving inside ice.
The life of an academic involves a certain amount of travel, in my case to Manchester in January. This as glamorous as it sounds, the drizzle has been unrelenting. Although on the bright side I was able to finish my talk for tomorrow in the Lass o Gowrie, which I can recommend; friendly barstaff, and the Citrus IPA was good. Tomorrow, I am going to give a talk about growing crystals, in particular growing crystals of a small molecule called glycine. We* studied the glycine molecule because when crystallised from water, it forms not one but two types of crystals.
Next week, I am off to Paris for a workshop, so I am writing my talk. Above is a plot of French cities. The x-axis is the log of the rank of the city, where the ranking of the city is by size, i.e., the first point (shown in pink) is for France’s largest city, Paris, at an a x value of log(1)=0, while the second point is France’s second largest city, Marseille, at a value log(2)=0.30, the third is Lyon at log(3)=0.48, etc. The y axis is the population of the city, raised to the power c = 0.18. This value is a fitting parameter, the value of 0.18 is the one that makes the data closest to a straight line — as you can see for this value of c the data falls on a pretty decent straight line.
Earlier this week I was at scientific meeting on how water freezes, a key problem in understanding how the cold clouds and snow form. The very last talk I caught before I had to leave to catch my train, showed some striking data. We know that ice and snow in the atmosphere almost always start to form not just from water on its own, but from water in contact with a tiny particle in the atmosphere. So the number of these particles and their surface properties greatly influence how clouds and snow form. If, for whatever reason, there are many of these particles in the air, we may get more snow.