This post could also be called “How We Spent Thanksgiving,” although the order of events would be reversed … in that the turkey came last.
Tryptophan and Sleep. Everyone is familiar with that sleepy feeling after the big Thanksgiving meal, that’s often blamed on the presence of the amino acid tryptophan in the bird’s meat. Tryptophan can be metabolized by our body to produce melatonin and seratonin, and both substances have known calming effects. However, for tryptophan to cause sleepiness, it must be consumed in pure form and on an empty stomach, a situation far from reality at the Thanksgiving table. Oddly enough, turkey meat contains about the same amount of tryptophan as other types of poultry, and actually less (on a percentage basis) than items such as chocolate, oats, milk, or peanuts. Its bad reputation is unfair!
The sleepy feeling associated with a big meal in fact results from a combination of factors, in which the tryptophan only plays a partial role. Meals with a high carbohydrate content induce the production of insulin, which is responsible for the control of sugar metabolism, but also for changes in the way amino acids are absorbed from the bloodstream. In the presence of insulin some amino acids are preferentially removed from circulation and absorbed by muscle cells, but tryptophan is not part of that group, so its relative concentration in the blood increases. Some of the tryptophan is converted into serotonin, and this compound makes a person sleepy. Of course, a large, carbo-loaded meal coupled with a few glasses of wine (or other alcoholic beverages) just adds to the overall desire to take a nap.
Tryptophan and Fluorescence. Tryptophan has an interesting characteristic: it is fluorescent! When it is excited by light, a fluorescent substance subsequently emits light. It’s almost like a happy diner opening a huge smile when the turkey is served… All proteins contain tryptophan, some in higher proportions than others. By purifying a particular protein we can measure its fluorescence in the laboratory using a fancy, $150,000 instrument called a fluorometer. Here is the little station where I spent a few hours on Thanksgiving Day:
A close up of the computer screen shows what the fluorescence measurement looks like: a curve with a peak, a “mountain-like”shape, and the height of the peak is related to the amount of light emitted by the protein.
The whole idea is to study the protein by adding different substances to it and observing how the fluorescence changes. The purified protein, as well as anything else added to it, is placed inside an expensive, transparent cell called a “cuvette,“ made of an optical-quality quartz glass that allows the passage of light without any interference.
But, after the work was done, the equipment was shut down, and the reagents were put away, we enjoyed a great Thanksgiving meal! We met many interesting people and had fun with four strong-willed golden retrievers, one of whom had a remarkable ability to jump up and gently steal a cracker with brie cheese from your hand.
ONE YEAR AGO: The Ultimate Apple Cake
TWO YEARS AGO: Trouble-Free Pizza Dough