8 Of The World’s Most Bizarre Flowers:

Atomic-level motion may drive bacteria’s ability to evade immune system defenses

A study from Indiana University has found evidence that extremely small changes in how atoms move in bacterial proteins can play a big role in how these microorganisms function and evolve.                                

The research, recently published in the Proceedings of the National Academy of Sciences, is a major departure from prevailing views about the evolution of new functions in organisms, which regarded a protein’s shape, or “structure,” as the most important factor in controlling its activity.

“This study gives us a significant answer to the following question: How do different organisms evolve different functions with proteins whose structures all look essentially the same?” said David Giedroc, Lilly Chemistry Alumni Professor in the IU Bloomington College of Arts and Sciences’ Department of Chemistry, who is senior author on the study. “We’ve found evidence that atomic motions in proteins play a major role in impacting their function.”

Daiana A. Capdevila et al, Entropy redistribution controls allostery in a metalloregulatory protein, Proceedings of the National Academy of Sciences (2017).  DOI: 10.1073/pnas.1620665114

The scientists conducted their experiments in Staphylococcus aureus, a common cause of skin, sinus and lung infections. Credit: Centers for Disease Control and Prevention      

(Image caption: Antidepressants move G proteins out of lipid rafts in the cell membrane. Credit: Molly Huttner)

Why do antidepressants take so long to work?

An episode of major depression can be crippling, impairing the ability to sleep, work, or eat. In severe cases, the mood disorder can lead to suicide. But the drugs available to treat depression, which can affect one in six Americans in their lifetime, can take weeks or even months to start working.

Researchers at the University of Illinois at Chicago have discovered one reason the drugs take so long to work, and their finding could help scientists develop faster-acting drugs in the future. The research was published in the Journal of Biological Chemistry.

Neuroscientist Mark Rasenick of the UIC College of Medicine and colleagues identified a previously unknown mechanism of action for selective serotonin reuptake inhibitors, or SSRIs, the most commonly prescribed type of antidepressant. Long thought to work by preventing the reabsorption of serotonin back into nerve cells, SSRIs also accumulate in patches of the cell membrane called lipid rafts, Rasenick observed, and the buildup was associated with diminished levels of an important signal molecule in the rafts.

“It’s been a puzzle for quite a long time why SSRI antidepressants can take up to two months to start reducing symptoms, especially because we know that they bind to their targets within minutes,” said Rasenick, distinguished professor of physiology and biophysics and psychiatry at UIC. “We thought that maybe these drugs have an alternate binding site that is important in the action of the drugs to reduce depressive symptoms.”

Serotonin is thought to be in short supply in people with depression. SSRIs bind to serotonin transporters – structures embedded within nerve-cell membranes that allow serotonin to pass in and out of the nerve cells as they communicate with one another. SSRIs block the transporter from ferrying serotonin that has been released into the space between neurons – the synapse – back into the neurons, keeping more of the neurotransmitter available in the synapse, amplifying its effects and reducing symptoms of depression.

Rasenick long suspected that the delayed drug response involved certain signaling molecules in nerve-cell membranes called G proteins.

Previous research by him and colleagues showed that in people with depression, G proteins tended to congregate in lipid rafts, areas of the membrane rich in cholesterol. Stranded on the rafts, the G proteins lacked access to a molecule called cyclic AMP, which they need in order to function. The dampened signaling could be why people with depression are “numb” to their environment, Rasenick reasoned.

In the lab, Rasenick bathed rat glial cells, a type of brain cell, with different SSRIs and located the G proteins within the cell membrane. He found that they accumulated in the lipid rafts over time — and as they did so, G proteins in the rafts decreased.

“The process showed a time-lag consistent with other cellular actions of antidepressants,” Rasenick said. “It’s likely that this effect on the movement of G proteins out of the lipid rafts towards regions of the cell membrane where they are better able to function is the reason these antidepressants take so long to work.”

The finding, he said, suggests how these drugs could be improved.

“Determining the exact binding site could contribute to the design of novel antidepressants that speed the migration of G proteins out of the lipid rafts, so that the antidepressant effects might start to be felt sooner.”

Rasenick already knows a little about the lipid raft binding site. When he doused rat neurons with an SSRI called escitalopram and a molecule that was its mirror image, only the right-handed form bound to the lipid raft.

“This very minor change in the molecule prevents it from binding, so that helps narrow down some of the characteristics of the binding site,” Rasenick said.

Trillion-Ton Iceberg Breaks Off Antarctica

Even though the towering berg weighs more than 1.1 trillion tons (1 trillion metric tons), it won't have a direct impact on sea-level rise. That's because the ice was already floating on the sea. Even so, when an iceberg like this one calves, it can speed up the collapse of the rest of the ice shelf.

One of the largest icebergs ever recorded, packing about a trillion tons of ice or enough to fill up two Lake Eries, has just split off from Antarctica, in a much anticipated, though not celebrated, calving event.

A section of the Larsen C ice shelf with an area of 2,240 square miles (5,800 square kilometers) finally broke away some time between July 10 and today (July 12), scientists with the U.K.-based MIDAS Project, an Antarctic research group, reported today.

Continue Reading.

For International Women’s Day, here are 12 women from chemistry history: wp.me/p4aPLT-2ra and 12 from chemistry present: wp.me/p4aPLT-5w7

The Blue Lava of Kawah Ijen Volcano. The ‘blue lavas’ are a rare phenomenon, only visible on the Kawah Ijen Volcano, in Indonesia. It may look like the volcano is spewing blue lava, but in fact, the shocking blue fire occurs when the volcanic sulphuric gases combust. Emerging from cracks in the volcano’s side, these gases ignite when coming into contact with air. It’s not actual blue lava, but blue flames. (video)

Antibiotic resistance discovered in the guts of ancient mummies

The gut bacteria inside 1000-year-old mummies from the Inca Empire are resistant to most of today’s antibiotics, even though we only discovered these drugs within the last 100 years.

“At first we were very surprised,” Tasha Santiago-Rodriguez of California Polytechnic State University in San Louis Opisbo, told the Annual Meeting of the American Society for Microbiology last month.

Her team studied the DNA within the guts of three Incan mummies dating back to between the 10th and 14thcenturies and six mummified people from Italy, from between the 15th and 18th centuries. They found an array of genes that have the potential to resist almost all modern antibiotics, including penicillin, vancomycin and tetracycline.

These ancient genes were largely in microbes whose resistance is problematic today, including Enteroccocus bacteria that can infect wounds and cause urinary tract infections. But they found that many other species, including some harmless ones, carried some of these resistant genes too.

Enterococcus enigma

“When you think about it, almost all these antibiotics are naturally produced, so it makes sense to find antibiotic genes as well,” says Santiago-Rodriguez.

Their finding shows that genes that can confer resistance to antibiotics were relatively widespread hundreds of years before Alexander Fleming discovered penicillin in 1928. “It’s ridiculous to think evolution of antibiotic resistance began when penicillin was discovered,” said team-member Raul Cano, also at California Polytechnic State University, at the meeting while discussing the findings. “It’s been going on for 2 billion years.”

These genes existed long before antibiotics became common, but it is our overuse of these drugs in both people and livestock that caused the superbug resistance to explode worldwide, said Cano.

“This is exciting data,” says Adam Roberts, who studies antibiotic resistance genes at University College London. While it is already well known that antibiotic resistance occurred naturally before people started using antibiotics, this study shows that resistance genes were already within the human gut long before we started using these drugs, he says.

“It begs the question of what was selecting for these genes at this time? Was it the natural production of antibiotics by other bacteria, or were there other, as yet unknown forces at play?” asks Roberts.

January is #NationalBloodDonorMonth 💉 Which different blood types are compatible with one another? This graphic takes a look: https://ift.tt/35wB7S9 https://ift.tt/2ugvtXs

Original illustrations from the 1851 edition of the Iconographic Encyclopedia of Science, Literature and Art by J.G. Heck.

This Week in Chemistry: Preventing marble statue weathering, further progress towards hydrogen fusion, and more! Links: http://goo.gl/WeJRV5