Hydrangeas and their Variety of Colour

Hydrangeas (Hydrangea macrophylla) have been known to form in a range of colours, from red, to purple, to blue, with having nothing to do with the genetics of the plant. So, if this colour difference isn't due to the genes, it must be due to certain environmental factors, and as it turns out, it is all to do with the pH and other properties of the soil. The more acidic the soil, and the greater [Al³⁺] in the soil, the more blue the sepals of the hydrangea will become. So why is this? Let's start with looking at the pigments which govern the colour of the sepals. The major pigment found in Hydrangeas (along with a number of other plants) is called Myrtillin, also known as delphinidin 3-glucoside, which is part of a group of molecules called anthocyanin.

But odly, this molecule assumes a red colour in acidic conditions and blue in basic conditions¹ (opposite to that of the soil conditions) and the pH within the sepals is usually slightly acidic, with little variation, so the blue colouring must have something to do with the Al³⁺. Through much research, Kondo et al. ², came up with a model proposing that the aluminum acts as a bridge to coordinate the Myrtillin to other copigments pigments known as acylquinic acids, which produces this blue colour.

While this is how the blue colour is formed, it can be safely assumed that the red colour is merely caused by Myrtillin by itself without any co-pigments or metal chelation.  A question which hasn't been answered yet is what the pH of the soil has to do with all of this.  The low pH allows there to be more free aluminum ions within the soil, to allow there to be more [Al³⁺] taken up into the plant.

References:
Second figure from 1.
1. K. Yoshida, M. Mori and T. Kondo, Nat. Prod. Rep., 2009, 26, 884–915.
2. T. Kondo, Y. Toyama-Kato and K. Yoshida, Tetrahedron Lett., 2005, 46, 6645–6649.

Why are Flamingos Pink?

This is a question that many children will ask their parents at some point, and if the child is chemically literate this is what the parents could tell them.  Flamingos primarily eat crustaceans and algae from their aquatic environment, which we usually see them standing in, and in their food, there is what is known as carotenoid pigments. Carotenoids are made from fats, and the incorporated into the chloroplasts of algae to serve as light absorbing pigment.  Then the algae get eaten by the crustaceans or flamingos, the carotenoids get passed on into these animals.  Usually when a molecule is eaten, it breaks down, but something such as a pigment will absorb into your bloodstream and not break down, so when a flamingo eats these, the pigments enter the blood stream and then eventually come out in their feathers.  Now for flamingos, the primary pigments which get absorbed and end up in their feathers, are Canthaxanthin (the molecule below), astaxanthin and  phoenicoxanthin ¹. Canthaxanthin is a molecule which gives of a bright violet colour when it is crystallized  but when it is incorporated into flamingo feathers, it is diluted to give a vibrant pink.

References:
1. Fox, D., and T. Hopkins. "Comparative Metabolic Fractionation of Carotenoids in Three Flamingo Species." Comparative Biochemistry and Physiology 17.3 (1966): 841-56.

When the Catholic Church and Science Get Along

I asked myself yesterday, while watching TV, what is used to make the papal smoke turn either white or black, and how do they make sure there is no false alarm.  In my research I found that they previously used wet straw to make the black smoke and nothing added to make the white smoke. But in an article by The Guardian, I found that they now use an electronic smoke machine, starting in 2005, where potassium perchlorate (KClO₄), anthracene (3 fused benzene rings), and sulphur is used to make the black smoke, while potassium chlorate (KClO₃), lactose and a pine resin is used to make the white smoke.

So how does this work?

Black
The anthracene (from tar) helps the burnt carbon from the paper flow upwards in the smoke instead of remaining in the ash.  The KClO₄ is used to aide the combustion of the paper to create the chunks of carbon. What carries all of this upward is the water that is generated in the chemical reaction of combustion. Just think of it as the burnt carbon as being graphite, which produces a back colour.

White
What creates the white smoke is the existence of unburnt paper, or other unburnt fuel, rising up with the heat.  The paper is thermally broken apart in a process called pyrolisis, leaving small white particles of unburnt cellulose, or from the added resin, rising up as the combustion product of H₂O rises out of the chimney. Just think of the particles of unburnt fuel being like table sugar, which gives off a white colour.

References:
Via: The Guardian