Tag Archives: peptide

A milk peptide could lead us to new, non-addictive sleep medication

A new study highlights that certain elements in casein tryptic hydrolysate (CTH), a mixture of protein elements that are naturally produced from the digestion of milk, could form the basis of new sleep remedies.

Image via Pixabay.

The calming, rest-inducing effect of a glass of warm milk before bedtime is already well known. Researchers ascribe this mostly to tryptophan, an amino acid present in milk. However, new research suggests that this isn’t the only compound in milk that helps us sleep. A mixture of peptides (the building blocks of proteins) collectively known as CTH, which is also present in milk, also seems to have such an effect.

New research zooms in on the issue more closely, identifying which specific peptides in CTH produce this effect. Such molecules could be used to create novel, all-natural treatments for sleep disorders, the study explains.

Milk for sleep

Insomnia is quite a serious issue on a global level. Different sources estimate that between 10% and 30% of adults worldwide suffer from chronic insomnia, although some estimates place it as high as 50% or even 60%. Since lack of sleep can quickly become a debilitating issue, doctors often prescribe sedatives to help their patients get some shut-eye. The most common drugs used for this purpose are benzodiazepines and zolpidem (brand name Ambien).

They do their job well, but the side effects can become very uncomfortable, even debilitating in their own right. Both of these sedatives are also quite addictive. So any alternatives to these treatments would be welcome, for both doctors and patients.

Many sedatives today work by activating the GABA receptor in the brain — this is a receptor site that, once bound, reduces anxiety and enhances sleep. The interaction between the casein in cow’s milk with trypsin, a digestive enzyme present in the human stomach, produces a peptide complex known as CTH. A specific element in this mixture, α-casozepine (α-CZP), has previously been identified as interacting with the GABA receptor. Starting from this background, the authors wanted to see if other peptides in this complex can produce similar or greater sleep-enhancing effects.

The authors used mass spectrometry to identify other peptides with bioactive properties released from CTH during a simulated gastric process (simulated digestion). They then virtually estimated their potential to pass through the blood-brain barrier and tie to the GABA site. The most promising candidates were then tested in live mice.

One, in particular, christened YPVEPF, had a very encouraging effect. Compared to mice in the control group, 25% of those who were administered YPVEPF fell asleep more quickly. Mice in the experimental group also slept on average more than 4 times as much as those in the control group.

Considering the efficacy YPVEPF showed in mice, the team hopes to carry on investigating its potential in human subjects. Eventually, they hope, it will form the basis for new, non-addictive drugs meant to tackle sleep disorders. They also advise that other promising peptides in the CTH complex be investigated further, especially those that can produce sleep-enhancing effects through pathways other than the GABA receptor.

The paper “Identification and Screening of Potential Bioactive Peptides with Sleep-Enhancing Effects in Bovine Milk Casein Hydrolysate” has been published in the Journal of Agricultural and Food Chemistry.

Scientists explore the origin of metabolism to reveal secrets of primordial life

Many scientists believe that life likely first appeared in hydrothermal vents rich in iron and sulfur. The first cells incorporated these elements into peptides which became the first ferredoxins. Credit: Ian Campbell, Rice University.

Life couldn’t exist without some form of energy to power it, and in order to access energy from the environment (i.e. food), animals and plants have had to evolve a conversion process known as metabolism. In a new exciting study, researchers at Rutgers University and Rice University reverse-engineered a primordial protein which might resemble the first biological machines involved in metabolism. In doing so, the researchers have brought us a step closer to uncovering the very origins of life itself.

“We are closer to understanding the inner workings of the ancient cell that was the ancestor of all life on earth – and, therefore, to understanding how life arose in the first place, and the pathways life might have taken on other worlds,” said lead author Andrew Mutter, a postdoctoral associate at Rutgers University’s Department of Marine and Coastal Sciences.

Mutter and colleagues studied a class of proteins called ferredoxins, which play a crucial role in supporting the metabolism of bacteria, plants, and animals by moving electrical charge through cells.

Although today’s ferredoxins are complex, scientists believe that in life’s early days, these proteins had a much simpler form. But what did they look like exactly? Similarly to how biologists compare modern birds and reptiles to infer characteristics about their shared ancestor, the researchers compared various ferredoxins found in all sorts of living things. With the help of computer models, this information enabled the team to design possible forms which the very first metabolic proteins might have taken.

A basic version of the protein was created by the researchers and then inserted into living cells. The researchers first removed the gene responsible for encoding ferredoxin from the E. coli bacteria’s genome, and replaced with a gene for their simple protein. Remarkably, the modified bacteria survived and replicated, although the colony’s growth rate was slower than normal.

The findings have important implications for synthetic biology and bioelectronics, the authors emphasized.

“These proteins channel electricity as part of a cell’s internal circuitry. The ferredoxins that appear in modern life are complex – but we’ve created a stripped-down version that still supports life. Future experiments could build on this simple version for possible industrial applications,” said co-author Vikas Nanda, a professor at Rutgers Robert Wood Johnson Medical School and Center for Advanced Biotechnology and Medicine.

The new study was published in the Proceedings of the National Academy of Sciences.

Researchers repurpose wasp venom peptides as antibiotics

The compounds can kill unwanted bacteria but are completely harmless to humans.

Finally, a use for wasps.

Few creatures are as hated as wasps. Although they do provide some environmental services, they’re often parasitic species, they’re nasty, and their sting can pack quite a punch. Unlike bees, their stingers don’t get lodged in the unfortunate victim, but even so, a wasp’s venom can cause great pain and irritation to humans.

Naturally, it’s also excellent at killing bacteria — the problem is that it also kills healthy, clean cells. Now, A team of MIT researchers managed to tweak the wasp venom so that it only kills bacteria, and leaves good cells alone.

“We’ve repurposed a toxic molecule into one that is a viable molecule to treat infections,” says Cesar de la Fuente-Nunez, an MIT postdoc. “By systematically analyzing the structure and function of these peptides, we’ve been able to tune their properties and activity.”

The key lies in a group of compounds called peptides. These are essentially a group of amino acids linked together to form a chain. They carry out important physiological functions, and in many ways, are similar to proteins. However, peptides are much smaller than proteins. They also tend to be less well defined in structure and scope than proteins.

Peptides in the wasps’ venom kill microbes by destroying their cell membranes — this happens because the peptides have a helix-type structure, with a right-hand spiral spin (which is known to strongly interact with cell membranes). The researchers isolated a venom peptide from a wasp called Polybia paulista, whose habitat ranges over several South American countries.

The peptide is small, containing only 12 amino acids, which allows researchers to experiment with it more easily.

“It’s a small enough peptide that you can try to mutate as many amino acid residues as possible to try to figure out how each building block is contributing to antimicrobial activity and toxicity,” de la Fuente-Nunez says.

A typical alpha-helical structure.

They tweaked a few dozen versions, measuring how each alteration affected the peptide’s properties, and then tested them against seven strains of bacteria and two of fungus, further correlating their structure and physiochemical properties (such as hydrophobicity and helicity) with their antimicrobial potency. After these observations, they designed several other versions, identifying the optimal percentages and structures of different amino acids so that they harm bacteria while leaving healthy tissue intact. Then, to test if the resulting peptides really were harmless, they tested their toxicity on human embryonic kidney cells grown in a lab dish.

The cells were infected with Pseudomonas aeruginosa — a common source of respiratory and urinary tract infections. They found that one peptide could completely clear the infection, eliminating it after only a few days.

“After four days, that compound can completely clear the infection, and that was quite surprising and exciting because we don’t typically see that with other experimental antimicrobials or other antibiotics that we’ve tested in the past with this particular mouse model,” de la Fuente-Nunez says.

In addition, researchers say a similar technique could be used in a wide array of situations.

“I do think some of the principles that we’ve learned here can be applicable to other similar peptides that are derived from nature,” he says. “Things like helicity and hydrophobicity are very important for a lot of these molecules, and some of the rules that we’ve learned here can definitely be extrapolated.”

This is not the first time peptides have been used to kill pathogens. The technique is particularly promising considering the worrying emergence of drug-resistant bacteria. Not only could this technology work as a new class of antibiotics, but it could also render pathogens incapable to adapt to it since adaptation processes usually take place at the cellular walls, and these peptides actually destroy the wall.

Due to their small size, peptides from wasp and scorpion venom are also being investigated as tools to ferry drugs to the brain, through the blood-brain barrier.

The paper was published in Nature Communications Biology.

Scorpion venom protein might be used to ferry drugs to the brain

Researchers have found a way to take advantage of one of venom’s most dangerous properties: its ability to reach the brain.

Image via Wikipedia.

The brain is the most complex human organ, and like any complex mechanism, it’s vulnerable to external interference. That’s why it’s hidden in our sturdy skulls, surrounded by cerebrospinal fluid, and locked tight by the blood-brain barrier (BBB). The blood-brain barrier is a highly selective semipermeable border that ensures no unwanted pathogens reach the brain.

However, all this protection comes at a cost: it’s really hard to for doctors to deliver necessary drugs to the brain, and sometimes, a drug has to be administered directly into the cerebrospinal fluid.

“About 98% of drugs that could have therapeutic applications cannot be used because they cannot cross this barrier,” explains Ernest Giralt one of the authors of the new study, and lab leader at the Institute for Research in Biomedicine Barcelona.

Giralt and colleagues may have found a workaround that issue, employing the usage of an unexpected substance: venom.

The venom of the Giant Yellow Israeli scorpion (Leiurus quinquestriatus), a species native to desert habitats ranging from North Africa through to the Middle East, could hold the key. The venom holds a small protein (a peptide) derived from chlorotoxin that has the ability to penetrate the blood-brain barrier.

“Our goal is to enable drugs to enter the brain and to do this we bind them to peptides specifically designed to cross the BBB. The conjugation of these drugs to the shuttles would improve their efficacy,” says Meritxell Teixidó, co-leader of the research.

Essentially, the venom could serve as a shuttle for drugs — which is not entirely a new idea. In previous studies, scientists took inspiration from a peptide found in bee venom (named apamin), making a few minor chemical modifications to ensure that it can pass the BBB. However, chlorotoxin, which is found in the venom of the scorpion, already has this ability — it’s one of the reasons why the scorpion’s venom is so dangerous. In other words, they took one of the threats of venom and found a way to use it as an advantage.

“Thousands of venoms that hold millions of peptides with the shuttle potential have been described. We chose chlorotoxin because it has already been reported that it acts like a toxin in the brain,” explains Teixidó.

So far, preliminary results are highly encouraging. Although this still needs to be investigated and thoroughly confirmed, it’s quite promising.

“Our results reveal animal venoms as an outstanding source of new families of BBB-shuttles,” researchers conclude.

The study “From venoms to BBB-shuttles. MiniCTX3: a molecular vector derived from scorpion venom” has been published in Chemical Communications.

New star-shaped polymer can shred bacteria membranes to bits, offering alternative to antibiotics

A new class of star-shaped polymers has proven effective at killing drug-resistant bacteria, opening new potential treatment options in the future.

Neutrophil and Methicillin-resistant Staphylococccus aureus (MRSA) Bacteria.
Image credits NIAID / Flickr.

Bacteria are an adaptable lot. We’ve learned before just how incredibly fast these bugs can learn to thrive in antibiotics which took us decades to develop. A new approach in medicine is to use physical rather than chemical means of killing these single-cell organisms. And now we have another such weapon: a team from the Melbourne School of Engineering has developed a new class of star-like protein chains or “peptide polymers,” that can effectively kill bacteria which are impervious to current antibiotics.

Professor Greg Qiao from the school’s Department of Chemical and Biomolecular Engineering and his team said that the only real avenue of treatment currently available for infections caused by bacteria is antibiotics. But he’s worried that if we continue the arms race with bacteria in this way, we will be left defenseless in a few decades.

“It is estimated that the rise of superbugs will cause up to ten million deaths a year by 2050. In addition, there have only been one or two new antibiotics developed in the last 30 years,” he said.

The team has been working with peptide polymers for the past few years, looking for a way to weaponize them in our favor. Recently, they developed a star-shaped polymer that might become one of the best foot-soldier in this fight. And the upshot is that the substance is harmless to the patient.

Tests undertaken on mice have shown that the polymer is extremely effective at killing Gram-negative bacteria — a class known for its propensity to develop antibiotic resistance. The bacteria showed no signs of resistance against the peptide polymers, and the little ninja stars have shown they can destroy bacteria through multiple pathways, unlike most antibiotics which kill with a single pathway — meaning they can be used to cure several types of bacteria.

“Comprehensive analyses using a range of microscopy and (bio)assay techniques revealed that the antimicrobial activity of SNAPPs [the polymers] proceeds via a multimodal mechanism of bacterial cell death by outer membrane destabilization, unregulated ion movement across the cytoplasmic membrane and induction of the apoptotic-like death pathway,” the paper reads.

One of these pathways includes ‘ripping apart’ the bacteria cell wall.
Image credits University of Melbourne.

They’ve also determined experimentally, by testing with red blood cells, that you’d have to pump 100 times the effective dosage into a patient for it to become toxic to the body. While more research is needed to bring the ninja stars of bactericide to market, Professor Qiao and his team believe that their discovery is the beginning of unlocking a new treatment for antibiotic-resistant pathogens.

The full paper, titled “Combating multidrug-resistant Gram-negative bacteria with structurally nanoengineered antimicrobial peptide polymers,” has been published in the journal Nature Microbiology.

Cheap self-assemling anti-cancer molecules created in minutes

Researchers have developed a simple, highly effective and cheap way of making artificial anti-cancer molecules that mimic the properties of one of the body’s natural defense systems – peptides.

Peptides are naturally occurring biological molecules. Peptides are naturally produced by the body to fight some infections and cancers and have proven to be effective against colon cancer cells in laboratory tests. Now, a team of chemists led by Professor Peter Scott at the University of Warwick, UK, have been able to produce molecules that have a similar structure to peptides.

The idea of developing peptides in a lab is not new, but producing artificial peptides has been prohibitively expensive, and highly time-consuming. However, with this new technique, artificial peptides can be produced in a matter of minutes, and the process doesn’t require expensive materials or machines.

They key here was a form of complex chemical self-assembly which, in addition to reduced costs and time, also produces very stable molecules. The authors have a very poetic way of visualizing this process:

“The chemistry involved is like throwing Lego blocks into a bag, giving them a shake, and finding that you made a model of the Death Star” says Professor Scott. “The design to achieve that takes some thought and computing power, but once you’ve worked it out the method can be used to make a lot of complicated molecular objects.”

However, just because the process is effective doesn’t mean it’s also simple – on the contrary.

“When the organic chemicals involved, an amino alcohol derivative and a picoline, are mixed with iron chloride in a solvent, such as water or methanol, they form strong bonds and are designed to naturally fold together in minutes to form a helix. It’s all thermodynamically downhill. The assembly instructions are encoded in the chemicals themselves.”

“Once the solvent has been removed we are left with the peptide mimics in the form of crystals”, says Professor Scott. “There are no complicated separations to do, and unlike a Lego model kit there are no mysterious bits left over. In practical terms, the chemistry is pretty conventional. The beauty is that these big molecules assemble themselves. Nature uses this kind of self-assembly to make complex asymmetric molecules like proteins all the time, but doing it artificially is a major challenge.”

So far, the results have proven very effective in lab tests, but the real test will be to see how they fare in clinical trials on patients. However, scientists are optimist, especially as the artificial peptides exhibit a very low toxicity to bacteria, and will probably not have significant side effects.

“This is very unusual and promising selectivity,” says Professor Scott.

Scientific Reference: Alan D. Faulkner, Rebecca A. Kaner, Qasem M. A. Abdallah, Guy Clarkson, David J. Fox, Pratik Gurnani, Suzanne E. Howson, Roger M. Phillips, David I. Roper, Daniel H. Simpson & Peter Scott. Asymmetric triplex metallohelices with high and selective activity against cancer cells. Nature Chemistry (2014)    doi:10.1038/nchem.2024

Red wine’s link to health gains support

About a decade ago, researchers started paying closer attention to the much hailed healthy properties of red wine. Particularly, a compound found in red wine (resveratrol – also found in the “anti-cancer beer”) was shown by some to provide a healthier and longer life. However, while the claim was supported with evidence by several teams, it was attacked from all sides by scientits who don’t believe that resveratrol, a compound expensively synthesized in several drugs has so much benefits when ingested via red wine.

red wine

This week in the journal Science, researchers showed that resveratrol acts directly on a protein that has been linked to cell metabolism and inflammatory diseases – SIRT1.

“This will be a major step forward for the field,” says David Sinclair, a molecular biologist at Harvard Medical School in Boston, Massachusetts, and lead author of the study. ”The controversy has no doubt scared people off from studying these molecules.”

Some 10 years ago, Sinclair and his co-workers reported that resveratrol activated SIRT1, a member of a family of enzymes that is connected with ageing and several dangerous conditions. They founded a company that was acquired 4 years later by GSK. The main issue however was that several other teams tried to replicate their results, but weren’t able – which raised quite a lot of question marks. The only time they could replicate the results was when a bulky, hydrophobic tag was present on the accompanying peptide. Controversy went on and on, polarizing the situation into two opposite camps: those who believed you need the tag for resviretol to work its magic, and those who believe you don’t.

But Sinclair and his colleagues now report that some of the naturally occurring targets that are amenable to SIRT1 activation by resveratrol and other such compounds have a common feature: bulky, hydrophobic amino acids at a key position. This would pretty much eliminate previous controversies, because it doesn’t matter if you need the tag or not, since you have it anyway; the study they published now produces the much needed clarification and scoring a goal for red wine supporters.

However, it is still unclear to what extent the compound’s biological effects are caused by its interaction with SIRT1 – since resviretol actually acts on a number of different proteins.

Via Nature doi:10.1038/nature.2013.12563