Neurotransmitters Are Chemicals That Help In Transmitting Signals Across A Synapse. Different Neurotransmitters

Today is the Autumn Equinox in the northern hemisphere! What’s behind the changing colours of autumn leaves? http://wp.me/p4aPLT-sn

The Portuguese man o’ war delivers a powerful sting to its prey—and sometimes to people—through venom-filled structures on its tentacles. It is not a jellyfish, but rather a colony of different types of zooids (small animals). Jean Louis Coutant engraved the plate for this illustration.

My new favorite: Solvatofluorescence of Nile Red

Solvatochromism is the ability of a chemical substance to change color due to a change in solvent polarity, so it has different color in different solvents.

Also in some cases, the emission and excitation wavelength both shift depending on solvent polarity, so it fluoresces with different color depending on the solvent what it’s dissolved in. This effect is solvatofluorescence.

On the video the highly solvatochromic organic dye, Nile Red was added to different organic solvents and was diluted with another, different polarity organic solvent. As the polarity of the solution changed, the emitted color from the fluorescent dye also varied as seen on the gifs above and as seen on the video:

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Molecule of the Day: VX

VX (C11H26NO2PS) is a colourless, odourless, oily liquid under room temperatures. It is a member of the V-series of nerve agents, and is an extremely potent poison - only 0.01 grams of it is needed to kill a person by skin contact. VX was recently implicated in the assassination of Kim Jong-nam, the half-brother of the North Korean leader Kim Jong-un, in Malaysia.

VX is a potent inhibitor of acetylcholinesterase, which breaks down the neurotransmitter acetylcholine into acetic acid and choline. The normal function of the enzyme is to regulate the concentration of acetylcholine within the synaptic cleft, so as to control the frequency of binding of acetylcholine to cholinergic receptors on the postsynaptic cell membrane and hence the transmission of impulses across the synapse.

Consequently, the inhibition of acetylcholinesterase results in a rapid increase in the synaptic concentration of acetylcholine, as the presynaptic knob continues to synthesise it and secrete it into the synaptic cleft. As a result, the cholinergic receptors on the postsynaptic cell membrane are continually stimulated, and a rapid series of action potentials are triggered. This results in muscle spasms and eventual paralysis, leading to death by asphyxiation due to paralysis of the diaphragm.

VX exposure is usually treated using an injection of atropine and pralidoxime. Atropine inhibits certain cholinergic receptors, reducing the binding of acetylcholine to receptors and thus the triggering of action potentials. On the other hand, one end of pralidoxime binds to acetylcholinesterase and the other binds to the phosphate group of VX, which causes the VX molecule to detach from the enzyme together with the pralidoxime molecule (see below). This restores the ability of acetylcholinesterase to hydrolyse acetylcholine, hence reducing its synaptic levels.

VX is synthesised from phosphorus trichloride over multiple steps; first, it is methylated, reacted with ethanol, then transesterified with N,N-diisopropylaminoethanol to produce QL. This is then oxidised with sulfur, and isomerised via heating to produce VX.

The first of the 2016 science Nobel Prizes was announced earlier today. The prize for Medicine or Physiology was awarded to Yoshinori Ohsumi for his work on the mechanisms behind autophagy. Find out more about his Nobel-winning work with this graphic! http://bit.ly/NobelSci2016

(Image caption: Brandeis University professor Ricardo Godoy conducts the experiment in a village in the Bolivian rainforest. The participants were asked to rate the pleasantness of various sounds, and Godoy recorded their response. Credit: Alan Schultz)

Why we like the music we do

In Western styles of music, from classical to pop, some combinations of notes are generally considered more pleasant than others. To most of our ears, a chord of C and G, for example, sounds much more agreeable than the grating combination of C and F# (which has historically been known as the “devil in music”).

For decades, neuroscientists have pondered whether this preference is somehow hardwired into our brains. A new study from MIT and Brandeis University suggests that the answer is no.

In a study of more than 100 people belonging to a remote Amazonian tribe with little or no exposure to Western music, the researchers found that dissonant chords such as the combination of C and F# were rated just as likeable as “consonant” chords, which feature simple integer ratios between the acoustical frequencies of the two notes.

“This study suggests that preferences for consonance over dissonance depend on exposure to Western musical culture, and that the preference is not innate,” says Josh McDermott, the Frederick A. and Carole J. Middleton Assistant Professor of Neuroscience in the Department of Brain and Cognitive Sciences at MIT.

McDermott and Ricardo Godoy, a professor at Brandeis University, led the study, which appeared in Nature on July 13. Alan Schultz, an assistant professor of medical anthropology at Baylor University, and Eduardo Undurraga, a senior research associate at Brandeis’ Heller School for Social Policy and Management, are also authors of the paper.

Consonance and dissonance

For centuries, some scientists have hypothesized that the brain is wired to respond favorably to consonant chords such as the fifth (so-called because one of the notes is five notes higher than the other). Musicians in societies dating at least as far back as the ancient Greeks noticed that in the fifth and other consonant chords, the ratio of frequencies of the two notes is usually based on integers — in the case of the fifth, a ratio of 3:2. The combination of C and G is often called “the perfect fifth.”

Others believe that these preferences are culturally determined, as a result of exposure to music featuring consonant chords. This debate has been difficult to resolve, in large part because nowadays there are very few people in the world who are not familiar with Western music and its consonant chords.

“It’s pretty hard to find people who don’t have a lot of exposure to Western pop music due to its diffusion around the world,” McDermott says. “Most people hear a lot of Western music, and Western music has a lot of consonant chords in it. It’s thus been hard to rule out the possibility that we like consonance because that’s what we’re used to, but also hard to provide a definitive test.”

In 2010, Godoy, an anthropologist who has been studying an Amazonian tribe known as the Tsimane for many years, asked McDermott to collaborate on a study of how the Tsimane respond to music. Most of the Tsimane, a farming and foraging society of about 12,000 people, have very limited exposure to Western music.

“They vary a lot in how close they live to towns and urban centers,” Godoy says. “Among the folks who live very far, several days away, they don’t have too much contact with Western music.”

The Tsimane’s own music features both singing and instrumental performance, but usually by only one person at a time.

Dramatic differences

The researchers did two sets of studies, one in 2011 and one in 2015. In each study, they asked participants to rate how much they liked dissonant and consonant chords. The researchers also performed experiments to make sure that the participants could tell the difference between dissonant and consonant sounds, and found that they could.

The team performed the same tests with a group of Spanish-speaking Bolivians who live in a small town near the Tsimane, and residents of the Bolivian capital, La Paz. They also tested groups of American musicians and nonmusicians.

“What we found is the preference for consonance over dissonance varies dramatically across those five groups,” McDermott says. “In the Tsimane it’s undetectable, and in the two groups in Bolivia, there’s a statistically significant but small preference. In the American groups it’s quite a bit larger, and it’s bigger in the musicians than in the nonmusicians.”

When asked to rate nonmusical sounds such as laughter and gasps, the Tsimane showed similar responses to the other groups. They also showed the same dislike for a musical quality known as acoustic roughness.

The findings suggest that it is likely culture, and not a biological factor, that determines the common preference for consonant musical chords, says Brian Moore, a professor of psychology at Cambridge University, who was not involved in the study.

“Overall, the results of this exciting and well-designed study clearly suggest that the preference for certain musical intervals of those familiar with Western music depends on exposure to that music and not on an innate preference for certain frequency ratios,” Moore says.

This year’s Halloween special wraps up the chemistry behind making a mummy: http://wp.me/p4aPLT-26m

Stephanie Kwolek was born #OTD in 1923. She’s most famous for inventing the bulletproof polymer Kevlar: wp.me/p4aPLT-3dv