Sticking your neck out: How did plesiosaurs swim with such long necks?
When dinosaurs ruled the land, plesiosaurs ruled the oceans. Famous for their incredibly long necks — some of which were up to 7 metres long — plesiosaurs have remained an evolutionary mystery for hundreds of years. Pernille V. Troelsen, a PhD student at Liverpool John Moores University, UK is simulating plesiosaur locomotion with a 3D model to understand how they could swim with such long necks.
“A steady neck would be more hydrodynamic than a bent neck, and due to the pressure on a bent neck, plesiosaurs would probably only bend them when moving at slow speeds or when floating,’ says Ms Troelsen.
She reveals that not only increasing the bend in a plesiosaurs neck would have a big effect on the production of ‘hydrodynamic drag’, but the location of the bending may also play a large role. She adds that plesiosaurs would likely have had a more patient hunting style similar to today’s crocodiles and snakes.
“We have some ideas about why they had long necks and they mainly concern feeding strategies, but we still don’t fully understand how they moved,” explains Ms Troelsen. “These were extremely successful animals that existed for 140 million years, but we don’t have any living equivalents to compare with.”
Also Read: Klosneuviruses (Giant Virus): Contradict the theory of virus as fourth domain of life alongside Bacteria, Eukaryotas and Archean
Several possible theories suggest that plesiosaurs may have developed long necks to extend their feeding range. By laying immobile on the sea floor or floating at the surface and using their protruding necks to hunt, they may have been able to sneak up on their prey more easily, or simply been more effective at snapping up fast-moving prey.
To test the hydrodynamic effects of different neck bending degrees and locations, Ms Troelsen created a digital 3D model based on a simplified plesiosaur body shape and uses computational fluid dynamics to visualise and determine how bending the neck affects the flow of water around the animal.
To improve these 3D models for in future, Ms Troelsen will be looking at fossil evidence for more information about the shape and bendiness of plesiosaur necks: “Further studies will include digitized neck vertebrae from actual plesiosaurs which will allow us to have an even more realistic approach.”
Ms Troelsen believes that these and future results will provide deeper insights into this mysterious group of marine reptiles: “We hope that we can shed some light on the biomechanical implications of having such a long neck and learn more about the lifestyle and evolutionary history of plesiosaurs.”
The LHCb experiment is charmed to announce observation of a new particle with two heavy quarks
Today at the EPS Conference on High Energy Physics in Venice, the LHCb experiment at CERN’s Large Hadron Collider has reported the observation of Ξcc++ (Xicc++) a new particle containing two charm quarks and one up quark. The existence of this particle from the baryon family was expected by current theories, but physicists have been looking for such baryons with two heavy quarks for many years. The mass of the newly identified particle is about 3621 MeV, which is almost four times heavier than the most familiar baryon, the proton, a property that arises from its doubly charmed quark content. It is the first time that such a particle has been unambiguously detected.
Nearly all the matter that we see around us is made of baryons, which are common particles composed of three quarks, the best-known being protons and neutrons. But there are six types of existing quarks, and theoretically many different potential combinations could form other kinds of baryons. Baryons so far observed are all made of, at most, one heavy quark.
“Finding a doubly heavy-quark baryon is of great interest as it will provide a unique tool to further probe quantum chromodynamics, the theory that describes the strong interaction, one of the four fundamental forces,” said Giovanni Passaleva, new Spokesperson of the LHCb collaboration. “Such particles will thus help us improve the predictive power of our theories.”
Also Read: Yale Chemistry Professor Has the Key for More Sustainable Agro-Chemicals
“In contrast to other baryons, in which the three quarks perform an elaborate dance around each other, a doubly heavy baryon is expected to act like a planetary system, where the two heavy quarks play the role of heavy stars orbiting one around the other, with the lighter quark orbiting around this binary system,” added Guy Wilkinson, former Spokesperson of the collaboration.
Measuring the properties of the Ξcc++ will help to establish how a system of two heavy quarks and a light quark behaves. Important insights can be obtained by precisely measuring production and decay mechanisms, and the lifetime of this new particle.
The observation of this new baryon proved to be challenging and has been made possible owing to the high production rate of heavy quarks at the LHC and to the unique capabilities of the LHCb experiment, which can identify the decay products with excellent efficiency. The Ξcc++ baryon was identified via its decay into a Λc+ baryon and three lighter mesons K-, π+ and π+.
The observation of the Ξcc++ in LHCb raises the expectations to detect other representatives of the family of doubly-heavy baryons. They will now be searched for at the LHC.
This result is based on 13 TeV data recorded during run 2 at the Large Hadron Collider, and confirmed using 8 TeV data from run 1. The collaboration has submitted a paper reporting these findings to the journal Physical Review Letters.
Harvard University researchers have resolved a conflict in estimates of how much the Earth will warm in response to a doubling of carbon dioxide in the atmosphere.
What is the Conflict
That conflict — between temperature ranges based on global climate models and paleoclimate records and ranges generated from historical observations — prevented the United Nations’ Intergovernmental Panel on Climate Change (IPCC) from providing a best estimate in its most recent report for how much the Earth will warm as a result of a doubling of CO2 emissions.
Temperature increase between 1 to 3 degrees celsius
The researchers found that the low range of temperature increase — between 1 and 3 degrees Celsius — offered by the historical observations did not take into account long-term warming patterns. When these patterns are taken into account, the researchers found that not only do temperatures fall within the canonical range of 1.5 to 4.5 degrees Celsius but that even higher ranges, perhaps up to 6 degrees, may also be possible.
Also Read:
The research is published in Science Advances.
It’s well documented that different parts of the planet warm at different speeds. The land over the northern hemisphere, for example, warms significantly faster than water in the Southern Ocean.
“The historical pattern of warming is that most of the warming has occurred over land, in particular over the northern hemisphere,” said Cristian Proistosescu, PhD ’17, and first author of the paper. “This pattern of warming is known as the fast mode — you put CO2 in the atmosphere and very quickly after that, the land in the northern hemisphere is going to warm.”
But there is also a slow mode of warming, which can take centuries to realize. That warming, which is most associated with the Southern Ocean and the Eastern Equatorial Pacific, comes with positive feedback loops that amplify the process. For example, as the oceans warm, cloud cover decreases and a white reflecting surface is replaced with a dark absorbent surface.
Also read:
The researchers developed a mathematical model to parse the two different modes within different climate models.
“The models simulate a warming pattern like today’s, but indicate that strong feedbacks kick in when the Southern Ocean and Eastern Equatorial Pacific eventually warm, leading to higher overall temperatures than would simply be extrapolated from the warming seen to date,” said Peter Huybers, Professor of Earth and Planetary Sciences and of Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and co-author of the paper.
Huybers and Proistosescu found that while the slow mode of warming contributes a great deal to the ultimate amount of global warming, it is barely present in present-day warming patterns. “Historical observations give us a lot of insight into how climate changes and are an important test of our climate models,” said Huybers, “but there is no perfect analogue for the changes that are coming.”
University of Washington researchers have invented a cellphone that requires no batteries — a major leap forward in moving beyond chargers, cords and dying phones. Instead, the phone harvests the few microwatts of power it requires from either ambient radio signals or light.
The team also made Skype calls using its battery-free phone, demonstrating that the prototype made of commercial, off-the-shelf components can receive and transmit speech and communicate with a base station.
The new technology is detailed in a paper published July 1 in the Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies.
Cell phone use zero power
“We’ve built what we believe is the first functioning cellphone that consumes almost zero power,” said co-author Shyam Gollakota, an associate professor in the Paul G. Allen School of Computer Science & Engineering at the UW. “To achieve the really, really low power consumption that you need to run a phone by harvesting energy from the environment, we had to fundamentally rethink how these devices are designed.”
The team of UW computer scientists and electrical engineers eliminated a power-hungry step in most modern cellular transmissions — converting analog signals that convey sound into digital data that a phone can understand. This process consumes so much energy that it’s been impossible to design a phone that can rely on ambient power sources.
Phone vibration is source of power
Instead, the battery-free cellphone takes advantage of tiny vibrations in a phone’s microphone or speaker that occur when a person is talking into a phone or listening to a call.
An antenna connected to those components converts that motion into changes in standard analog radio signal emitted by a cellular base station. This process essentially encodes speech patterns in reflected radio signals in a way that uses almost no power.
To transmit speech, the phone uses vibrations from the device’s microphone to encode speech patterns in the reflected signals. To receive speech, it converts encoded radio signals into sound vibrations that that are picked up by the phone’s speaker. In the prototype device, the user presses a button to switch between these two “transmitting” and “listening” modes.
Using off-the-shelf components on a printed circuit board, the team demonstrated that the prototype can perform basic phone functions — transmitting speech and data and receiving user input via buttons. Using Skype, researchers were able to receive incoming calls, dial out and place callers on hold with the battery-free phone.
“The cellphone is the device we depend on most today. So if there were one device you’d want to be able to use without batteries, it is the cellphone,” said faculty lead Joshua Smith, professor in both the Allen School and UW’s Department of Electrical Engineering. “The proof of concept we’ve developed is exciting today, and we think it could impact everyday devices in the future.”
The team designed a custom base station to transmit and receive the radio signals. But that technology conceivably could be integrated into standard cellular network infrastructure or Wi-Fi routers now commonly used to make calls.
Future
“You could imagine in the future that all cell towers or Wi-Fi routers could come with our base station technology embedded in it,” said co-author Vamsi Talla, a former UW electrical engineering doctoral student and Allen School research associate. “And if every house has a Wi-Fi router in it, you could get battery-free cellphone coverage everywhere.”
The battery-free phone does still require a small amount of energy to perform some operations. The prototype has a power budget of 3.5 microwatts.
The UW researchers demonstrated how to harvest this small amount of energy from two different sources. The battery-free phone prototype can operate on power gathered from ambient radio signals transmitted by a base station up to 31 feet away.
Using power harvested from ambient light with a tiny solar cell — roughly the size of a grain of rice — the device was able to communicate with a base station that was 50 feet away.
Other battery free technologies
Many other battery-free technologies that rely on ambient energy sources, such as temperature sensors or an accelerometer, conserve power with intermittent operations. They take a reading and then “sleep” for a minute or two while they harvest enough energy to perform the next task. By contrast, a phone call requires the device to operate continuously for as long as the conversation lasts.
“You can’t say hello and wait for a minute for the phone to go to sleep and harvest enough power to keep transmitting,” said co-author Bryce Kellogg, a UW electrical engineering doctoral student. “That’s been the biggest challenge — the amount of power you can actually gather from ambient radio or light is on the order of 1 or 10 microwatts. So real-time phone operations have been really hard to achieve without developing an entirely new approach to transmitting and receiving speech.”
Next, the research team plans to focus on improving the battery-free phone’s operating range and encrypting conversations to make them secure. The team is also working to stream video over a battery-free cellphone and add a visual display feature to the phone using low-power E-ink screens.
Our galaxy could have 100 billion brown dwarfs or more, according to work by an international team of astronomers, led by Koraljka Muzic from the University of Lisbon and Aleks Scholz from the University of St Andrews. On Thursday 6 July Scholz will present their survey of dense star clusters, where brown dwarfs are abundant, at the National Astronomy Meeting at the University of Hull.
What are Brown dwarfs objects?
Brown dwarfs are objects intermediate in mass between stars and planets, with masses too low to sustain stable hydrogen fusion in their core, the hallmark of stars like the Sun. After the initial discovery of brown dwarfs in 1995, scientists quickly realised that they are a natural by-product of processes that primarily lead to the formation of stars and planets.
All of the thousands of brown dwarfs found so far are relatively close to the Sun, the overwhelming majority within 1500 light years, simply because these objects are faint and therefore difficult to observe. Most of those detected are located in nearby star forming regions, which are all fairly small and have a low density of stars.
When the research of brown dwarfs started?
In 2006 the team began a new search for brown dwarfs, observing five nearby star forming regions. The Substellar Objects in Nearby Young Clusters (SONYC) survey included the star cluster NGC 1333, 1000 light years away in the constellation of Perseus. That object had about half as many brown dwarfs as stars, a higher proportion than seen before.
To establish whether NGC 1333 was unusual, in 2016 the team turned to another more distant star cluster, RCW 38, in the constellation of Vela. This has a high density of more massive stars, and very different conditions to other clusters.
RCW 38 is 5500 light years away, meaning that the brown dwarfs are both faint, and hard to pick out next to the brighter stars. To get a clear image, Scholz, Muzic and their collaborators used the NACO adaptive optics camera on the European Southern Observatory’s Very Large Telescope, observing the cluster for a total of 3 hours, and combining this with earlier work.
The researchers found just as many brown dwarfs in RCW 38 — about half as many as there are stars — and realised that the environment where the stars form, whether stars are more or less massive, tightly packed or less crowded, has only a small effect on how brown dwarfs form.
Scholz says: “We’ve found a lot of brown dwarfs in these clusters. And whatever the cluster type, the brown dwarfs are really common. Brown dwarfs form alongside stars in clusters, so our work suggests there are a huge number of brown dwarfs out there.”
From the SONYC survey, Scholz and team leader Koraljka Muzic, estimate that our galaxy, the Milky Way, has a minimum of between 25 and 100 billion brown dwarfs. There are many smaller, fainter brown dwarfs too, so this could be a significant underestimate, and the survey confirms these dim objects are ubiquitous.
The last time you watched a spider drop from the ceiling on a line of silk, it likely descended gracefully on its dragline instead of spiraling uncontrollably, because spider silk has an unusual ability to resist twisting forces.
In a new paper appearing this week in Applied Physics Letters, from AIP Publishing, researchers from China and the U.K. showed that unlike human hair, metal wires or synthetic fibers, spider silk partially yields when twisted. This property quickly dissipates the energy that would otherwise send an excited spider spinning on the end of its silk.
Dragline silk from golden orb weaver spiders dissipates energy to prevent spinning
“Spider silk is very different from other, more conventional materials,” said Dabiao Liu of Huazhong University of Science and Technology. “We find that the dragline from the web hardly twists, so we want to know why.”
A greater understanding of how spider silk resists spinning could lead to biomimetic fibers that mimic these properties for multiple potential uses such as in violin strings, helicopter rescue ladders and parachute cords. “If we understood how spider silk achieves this, then maybe we could incorporate the properties into our own synthetic ropes,” said David Dunstan of Queen Mary University of London.
Spiders use dragline silk for the outer rim and spokes of their webs, and as a lifeline when dropping to the ground. The material has intrigued scientists because of its incredible strength, stretchiness and ability to conduct heat, but little research has focused on its torsional properties — how it responds to twisting.
Also Read: New research could help humans see what nature hides
Researchers used a torsion pendulum, the same tool used by Henry Cavendish to weigh the Earth in the 1790s, to investigate dragline silk from two species of golden silk orb weavers. They collected strands of silk from captive spiders and suspended the strands inside a cylinder using two washers at the end to mimic a spider. The cylinder isolated the silk from environmental disturbances and kept the strand at a constant humidity, because water can cause the fibers to contract. A rotating turntable twisted the silk while a high-speed camera recorded the silk’s back and forth oscillations over hundreds of cycles.
Unlike synthetic fibers and metals, spider silk deforms slightly when twisted, which releases more than 75 percent of its potential energy, and the oscillations rapidly slow. After twisting, the silk partially snaps back.
The team suspects that this unusual behavior is linked to the silk’s complex physical structure, consisting of a core of multiple fibrils inside a skin. Each fibril has segments of amino acids in organized sheets and others in unstructured looping chains. They propose that torsion causes the sheets to stretch like elastic, and warp the hydrogen bonds linking the chains, which deform like plastic. The sheets can recover their original shape, but the chains remain partially deformed. The pendulum exhibits this change with reduced magnitude of the silk’s oscillations, as well as a shifting of the equilibrium point of the oscillation.
The group will continue to investigate how spider silk reacts to twisting in this way and is also looking into how it maintains its stiffness during torsion, what effect humidity has and to what degree air helps dissipate the energy. “There is a lot of further work needed,” Dunstan said. “This spider silk is displaying a property that we simply don’t know how to recreate ourselves, and that is fascinating.”
Lipids are the fourth major group of molecules found in all the cells. Lipids are insoluble biomolecules that can be extracted from cells and tissues by non-polar solvents viz. chloroform ether, benzene. Unlike nucleic acids, proteins and polysaccharides, lipids are not polymeric. However, they aggregate, and it is in this state they perform their most important function as the structural matrix of biological membranes. They occur in oilseeds as a stored energy, required during germination. In animals, they are stored as fat granules in specialized cells of adipose tissues. Lipids have several biological functions:
Structural component of membranes (cell or organelles membranes)
As storage and transport form of metabolic fuel
As protective coating on surfaces of many organisms (leaf top and insects)
As cell surface component concerned in cell recognition, species specificity, and tissue immunity.
As insulation subcutaneously in some of the warm-blooded animals required during winter seasons, also engulfing some of the essential organs as protecting against any external injury.
Some have intensive biological activity viz. vitamins and hormones.
Classification of lipids with examples
The most satisfactory classification divides lipids into two classes. Complex lipids (saponifiable lipids) yield soaps (sodium salt of fatty acid) on alkali hydrolysis. They include acylglycerol, phospholipids, sphingolipids, and waxes. They differ in their backbone structure to which the fatty acids are covalently joined. Simple lipids (non-saponifiable lipids) do not contain fatty acids and hence are nonsaponifiable, e.g. terpenoids, steroids, and prostaglandins.
Complex Lipids Backbone
Acylglycerol Glycerol
Phospholipids Glycerol-3-Phosphate
Sphingolipids Sphingosine
Waxes Non-polar alcohols of high mol. wt.
Fatty acids
Fatty acids are carboxylic acids with long-chain hydrocarbon as the side group. They are mostly in esterified form; traces occur in free form in cell/tissues. Over 100 different fatty acids have been identified in nature in various plants and animals and microorganisms. The predominant fatty acid occurring in animals and plants are of C16 and C18 family, i.e., palmitic, oleic, linoleic and stearic acids. A fatty acid with <14 and >18 carbons are uncommon. Mostly they have carbon atoms in the even number, as they are synthesized in plants or animals by the catenation of C2 units. Over half of the fatty acids residues of plants and animals, lipids are unsaturated (contains double bond) and are often polyunsaturated (contains more than one double bond). Bacterial fatty acids are rarely polyunsaturated but are commonly branched, hydroxylated or contain cyclopropane ring.
Stearic acidOleic acidLinoleic acidα-Linolenic acid
Some generalization of fatty acids:
The most abundant fatty acids are even numbered than odd numbered
Chain length between C14 and C18 is predominant
The most common saturated fatty acid is palmitic and stearic, whereas unsaturated is oleic.
Unsaturated fatty acids (UFA) predominate over the saturated ones in plants and animals whose habitat is at lower ambient temperatures.
UFA has the lower melting point than the saturated ones with the same chain length.
The methylene group separates the double bonds and are rarely conjugated as shown:
Double bonds of nearly all the fatty acids are cis type rather than trans, although the cis is less stable than trans ones. The cis double bond makes a king of 30 degrees and hence are not tightly packed. The saturated fatty acid has free rotation around their carbon-carbon bond gives the hydrocarbon chain great flexibility and thus are tightly packed. The number of saturated fatty acids in the same volume are more in number than the unsaturated ones as shown. This is due to kinks in the unsaturated fatty acids.
Fatty acids which are required by mammals from the external source/ in the diet are termed as essential fatty acids. Linoleic and lemma-linolenic acid cannot be synthesized by mammals and must be obtained from the plant source. Linoleic acid is a necessary precursor for the biosynthesis of arachidonic acid, which is not present in plants. They are precursors of prostaglandins and like hormones have the profound effect on the physiological activity. Linoleic acid makes 10-20% of total fatty acid of the triacylglycerol and phospholipids.
Triacylglycerol
The fat and oils that occur in plants and animals consist primarily of the mixture of triacylglycerols (also called triglycerides). These nonpolar, water-insoluble substances are fatty acid triester of polyol, i.e., glycerol. Triacylglycerols that are solids at room temperature are termed as fats, whereas liquids are termed as oils. Diacylglycerol and cottonseed oil, groundnut oil, mustard oil, etc. are all plant lipids. The animal fat is not used in the diets of Indians but is used for making soaps.
Chemical properties
Glycerol molecule itself is not having any asymmetric carbon atom, and hence their ambiguity in naming it as shown below
When one of the primary alcohol groups is modified, the molecule becomes asymmetric, i.e., it can be written as L-glycerol-3-phosphate or D-glycerol 1-phosphate. Hence IUB (The International Union of Biochemists) have recommended that glycerol written in Fisher’s formula with the hydroxyl group on the central carbon if placed on the left, the top carbon is numbered as one and the bottom carbon as number three. This system of numbering is stereospecific numbering (Sn), and this prefix is used in naming asymmetric glycerol derivatives.
Hydrolysis and Saponification:
Triacylglycerols are split into glycerol and fatty acids by enzymes (lipases) and by alkali as shown below
This process of breaking ester linkage between fatty acid and glycerol by the addition of three water molecules is termed as hydrolysis, whereas splitting triglycerides by alkali is called saponification. The product formed is glycerol and sodium salt of fatty acids (soaps).
Rancidity
When butter or fats are stored, they often become rancid, give the foul smell. This is caused by the presence of proteins (enzymes, lipases) in them. The presence of catalysts may be due to impurities in fat or due to microorganism growth. This happens typically when oils are not well purified and are devoid of water in them. In this process low mol. Wt (4-10 carbon) aldehydes are released, which give the foul smell. To escape rancidity either:
The fats are stored at low temperature
Refined to the extent of purest form (with no water and proteins)
Solidified by hydrogenation
Hydrogenation changes the chemical structure of fatty acid present in fats. The process not only helps in removing rancidification but also makes transport more accessible. As hydrogenated fats are thought to cause atherosclerosis, in the present day world refined oils are being used for a useful purpose.
Microbes on farms protect children from asthma and allergies
It is a known fact that microbes on farms protect children from asthma and allergies. But even non-microbial molecules can have a protective effect: Immunologists from the University of Zurich have shown that a sialic acid found in farm animals is effective against inflammation of lung tissue. This study opens up a wide variety of perspectives for the prevention of allergies.
More and more people suffer from allergies and asthma. In the past decades, these diseases have massively increased in industrialized countries. Today, about 30 percent of children have allergies — with the exception of farm children. Among farm children, the disease is increasing less dramatically than in the case of their friends who live in the same village, but not on a farm. Microbes that occur in higher amounts and greater diversity on farms protect farm children from allergies and asthma. An environment that is not highly hygienic has a positive effect on the development of the immune system as it learns not to react to harmless materials as is the case with allergies.
A sialic acid acts as protection
Not only microbes protect against asthma evidently, but also farm animals: Petting cats and cows and drinking farm milk can also prevent asthma, as the team of researchers headed up by Remo Frei of the Swiss Institute of Allergy and Asthma Research from the University of Zurich in cooperation with the Center for Allergy Research and Education (CK-CARE) in Davos and the Children’s Hospital of Eastern Switzerland in St. Gallen: “Early childhood contact with animals and the consumption of food of animal origin seems to regulate the inflammatory reactions of the immune system,” says immunologist Frei. His study shows that a non-microbial substance, a sialic acid, is responsible for this mechanism. This substance is widespread in vertebrates — and therefore in many farm animals — but missing in the human organism: N-Glycolylneuraminic acid (Neu5Gc).
Antibodies as measure for contact with farm animals
Based on a genetic mutation, humans do not produce Neu5Gc. They can absorb sialic acid through contact with animals or by eating food of animal origin and integrate it into their glycoproteins. Contact with Neu5Gc triggers an antibody reaction in humans which can act as a measure for contact with Neu5Gc, that is, with farm animals. The researchers led by Remo Frei have measured the concentrations of Neu5Gc antibodies in the serum samples of children collected within the scope of two epidemiological studies financed by the European Union (PARSIFAL and PASTURE study).
Data comparison of more than a thousand children
As a comparison of the Neu5Gc antibody concentration of over a thousand children and the occurrence of asthma has clearly shown, “Farm children have many more antibodies against Neu5Gc in their blood — and children with more antibodies suffered considerably less from asthma,” Frei says. The positive effect of sialic acid Neu5Gc on the respiratory system was confirmed using a mouse-model: The Neu5Gc molecules consumed with food improved the pulmonary function of the mice, therefore reducing asthma symptoms.
From farm effect to allergy prevention
To understand the mechanism of how Neu5Gc affects the human immune system, researchers analyzed various cells of the immune system that play a role during an inflammatory reaction. With an interesting result — both in the children tested and on the animal model: Contact with Neu5Gc did not reduce immunoglobulin E, the antibody that frequently occurs during allergic reactions, but it initiates an anti-inflammatory reaction of the immune system. “This takes place through so-called regulatory T-cells, which have an increased presence,” Frei explains. “These T-cells dampen incorrect responses of the immune system and have a strong anti-inflammatory effect. Our research results open up opportunities for transferring the protective effect of farms to all children. In this way, we can possibly lay an important foundation stone for effective allergy prevention.”
Vitamins are organic compounds required in small amount in the diet of animals in order to ensure, healthy growth and production. Vitamins are essential nutrients because animal cannot synthesize such compounds inadequate amount for its daily needs. Historically the name vitamins arose from the fact that they are vital amines, hence were named vitamins. The alphabet ‘e’ from vitamins was removed when it was found that all such compounds were not amines, and named vitamins.
Classification of Vitamins
Vitamins may be classified into two groups according to their solubility
The water soluble (B) vitamins.
The fat soluble vitamins
Many of the water-soluble vitamins are components of larger coenzyme molecules, or in other words, the coenzymes are the derivatives of vitamins. Plants, however, have the ability to synthesize the vitamins (from CO2, NH3, and H2S) and in fact, serve as excellent source of these dietary essentials.
Thiamine
Thiamine, also in short B1, is a substituted pyrimidine joined by methylene bridge to a substituted thiazole.
Thiamine Chloride
It occurs in outer coat of seeds. The use of polished rice or refined wheat flour removes much of this vitamin. In animal tissue and yeast, it occurs primarily as the coenzyme thiamine pyrophosphate. Animals other than ruminants (whose bacteria can provide the vitamin) require thiamine in their diet.
Biochemical function:
It functions as coenzyme in many biochemical reactions as a component of enzymes. For example, Pyruvate dehydrogenase enzyme contains this TPP as coenzyme, catalyzes the reaction mentioned below. TPP is a nonprotein part of enzyme and helps in catalyzing the reaction.
Riboflavin
Riboflavin (vitamin B2) consists of the sugar alcohol (D-ribitol) attached to 7,8-dimethyl-isoallaxazine ring.
Riboflavin
The vitamin occurs as a component of the two flavin coenzymes, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)
Flavin mononucleotide
Riboflavin is synthesized by green plants, many bacteria, and fungi, but not by any animal. It is less soluble in water than thiamine. It is destroyed when exposed to bright light. Its main sources are milk, legumes, cereals, green leafy vegetables.
Flavin adenine dinucleotide (FAD)
Biochemical function:
Riboflavin functions as coenzyme because of its ability to undergo oxidative-reduction reactions. On reduction, the yellow color disappears since the reduced flavin is colorless. Overall reaction is addition of two hydrogen atoms in a 1, 4 addition to form reduced, colorless flavin.
oxidized riboflavin to Reduced riboflavin
FMN and FAD functions as coenzymes for a group of proteins known as flavoproteins. The enzyme succinate dehydrogenase that catalyzes the oxidation of succinate to fumarate contains FAD as covalent linked prosthetic group
Nicotinic Acid
The vitamin known as a niacin or vitamin B3 is nicotinic acid. Another form of the vitamin is the amide, nicotinamide or niacinamide.
Nicotinic acidNicotinamide
It is widely distributed in plants and animals tissues. The coenzyme form of the vitamin are the nicotinamide nucleotide, namely Nicotinamide adenine dinucleotide (NAD+) and Nicotinamide adenine dinucleotide phosphate (NADP+).
Nicotinamide Adenine dinucleotide (NAD+)Nicotinamide adenine dinucleotide phosphate (NADP+)Biochemical Function: Oxidation of alcohol to acetaldehyde, occurs by transfer of a hydride ion (a hydrogen atom with additional electron) and the release of a proton. H+.
It is component of dehydrogenases and helps in oxidation reduction reactions. For example conversion of alcohol to acetaldehyde is carried enzymes alcohol dehydrogenase, that contains NAD+ as coenzyme.
Vitamin B6 Groups
They are pyridoxal, pyridoxine, and pyridoxamine. These three forms of vitamin B6 are widely distributed in animal and plant sources, cereal grains are expecially rich source of this vitamin. All these three forms are interconvertible i.e. if one is ingested it can be converted to other two forms.
PyridoxalPyridoxinePyridoxaminePyridoxal 5′-phosphate
Pyridoxal phosphate is a versatile coenzyme that participates in the catalysis of several important reactions of amino acid metabolism i.e. transamination, decarboxylation, and racemization.
Transamination:
Glutamic aspartic transaminase
The enzyme glutamic aspartic transaminase consists of pyridoxal phosphate as cofactor.
Lipoic Acid
Lipoic acid is covalently linked through its carboxylic group to the e-amino group of a specific lysine residue of some enzymes.
lipoic acid
It can exist in either of the forms i.e. reduced or oxidized as shown above. It is involved in the reaction where pyruvate is converted to acetyl CoA with the help of enzyme pyruvate dehydrogenase. This enzyme contains the lipoic acid as one of the cofactor. Lipoic acid is attached to the protein though the lysine residue as shown below.
Biotin
The requirement of this vitamin is very low and its deficiency creation is very difficult. Its requirement is met through the intentinal bacteria as they can synthesize this vitamin. Its deficiency can be created by feeding large amount of raw avian egg white, which contains a protein avidin that has the ability to bind the biotin, and does not allow its absorption.
biotin
It is bound to protein through e-amino group of lysine residue of proteins as shown. Biocytin E-N-lysine is isolated when such proteins are hydrolysed. The bound form of this vitamin helps in carboxylation and transfer of carboxyl group in many biological reactions.
Biochemical Function
Pyruvate is converted to oxaloacetate by the help of enzyme pyruvate carboxylase. The enzyme contains biotin as a prosthetic group.
Folic Acid
Its requirement is very less in animal systems, hence its very difficult to produce its deficiency in them. Its main constitutents are 2, amino-hydroxy-6methyl pteridine, p-amino benzoic acid and gluatmic acid as shown below.
Folic acid
Folic acid is the vitamin and its reduction products is the coenzymic form. Enzyme L-folate reductase, reduces folic acid to dihydrofolate (H2F). The double bond at position 7-8 is lost as two hydrogen atoms are added. Dihydrofolate is further reduced to (H4F) tetrahydrofolate. The double bond at position 5-6 is lost by further addition of two hydrogen atoms. The reduction is carried out with the help of NADH and H+.
The central role of tetrahydrofolate is to act as a carrier of one carbon unit, at the oxidation level of formate. The formate unit is used in the biosynthesis of pyrimidine, purines, serine and glycine.
Biochemical function:
The enzyme serine hydroxymethyl transferase contains THF as coenzyme to carry out one carbon transfer reaction, e.g. as shown below.
Vitamin B12
This enzyme is isolated from liver as a cyanocobalamine. It may also be isolated with anions other than cyanide, viz. hydroxyl, nitrate, chloride or sulphate. It is found only in animals and microorganisms and not in plants. It is involved in reactions like transmethylation and intramolecular migration. One of the reactions in which it is involved is given below.
Vitamin B12
Biochemical function:
The enzyme contains the cyanocoblamine as the coenzyme
Pantothenic Acid
It occurs as a component of coenzyme A and acyl carrier protein (ACP).
Pantothenic Acid
In 1954 Lipman found that a heat stable cofactor was required in many enzymes catalyzing acetylation. This cofactor was named coenzyme A, where A stands for acetylation. The terminal sulfhydryl group of CoA is the reactive site. The acyl group is attached to the CoA by thioester found.
Acyl carrier protein (ACP): Vagelos discovered that the intermediates in fatty acid synthesis in E.Coli are linked to an acyl carrier protein. Specifically they are linked to the sulfhydryl terminus of phosphantotheine group.
Vitamin C
This enzyme is water soluble. It is also named as ascorbic acid and can be isolated in pure crystalline form from lemon juice. Vitamin C also required in diet of only a few vertebrates- man, monkey, the guinea pigs and certain fishes, which are unable to synthesize them. Most other higher animals and plants can synthesize ascorbic acid from glucose or other simple precursors. It is requried for the normal formaiton of connective tissues (collagen). The vitamin especially is involved in the hydroxylation of proline and lysine residues of the collagen.
Vitamin C
Its deficiency leads to scurvy.
Fat Soluble Vitamins
These vitamins are designated by the letters A, D, E and K. Unlike water soluble vitamins, they are stored in the organisms. Therefore, their supply in excess can be harmful. No specific coenzyme function has yet been found for any of the fat soluble vitamins.
Vitamin-A
Vitamin A1 or retinol and its aldehyde derivative, retinal, has the following structure:
These compounds are formed from their parent substance beta-carotene, which is called its provitamin.
Vitamin A
An oxygenase located in the intestinal mucosa cleaves the beta-carotene as shown above, yielding two molecules of vitamin A1 aldehyde or retinal, which is then reduced to retinol by alcohol dehydrogenase. Beta-carotene is synthesized in plants by not in animals. The deficiency of vitamin A leads to night blindness. It is stored in liver. Excess intake leads to toxicity. Retinol and its aldehyde, retinal are the intermediates in chemical changes that occur during the visual process in the rods cell of an eye.
Rhodopsin consists of 11 cis-retinal bound to a protein (opsin). Light isomerizes 11-cis-retinal and it leads to the conversion of rhodopsin to opsin and all trans-retinal, which ultimaely leads to cascade of reactions that make us to see.
Vitamin D
Vitamin D also called calciferol, has two important forms i.e. D2 (ergocalciferol) found in plants and D3 (cholecalciferol) found in animals. They are the derviatives of cholesterol and are involved in the calcium and phosphorous metabolism.
Cholecalciferol or Vitamin D
The active form of vitamin D3 is 1.25 dihydrocholecalciferol (calcitriol), which is required for the normal formation of bones. The vitamin increases the calcium absorption into intestinal cells and brings about normal calcification of bone matrix. Its deficiency leads to rickets. Vitamin D2 is formed from ergosterols in plants.
Vitamin E
They are also named as tocopherols (group of related compounds). It contains substituted aromatic ring and long hydrocarbon chain as shown.
Tocopherol or Vitamin E
This vitamin prevents the oxidatin of unsaturated fatty acids. It occurs in plant oils, wheat germ, rice bran and soyabean. Its deficiency leads to destruction of erythrocytes and causes muscular dystrophy. Tocopherols are used commercially to retard spoilage of foods.
Vitamin K
Also called coagulation vitamin as its deficiency increases blood clotting time. At least two forms are known: Vit-K1 (Phylloquinone) in plants, Vit-K2 (menaquinone) in intestinal microflora
Vitamin K or Phylloquinone
Vitamin K2 consists of 6-9 isoprene units that are indicated in the brackets. The vitamin helps in the formation of prothrombin, a blood plasma protein which is essential in blood clot formation.
Nitrogen Base
The nitrogenous bases are derivatives of two heterocyclic compounds, pyrimidine and purine
Nucleic acids have three principal derivatives of pyrimidine base i.e. cytosine, thymine, and uracil, whereas two principal purine bases i.e. guanine and adenine. Thymine is only present in DNA and uracil in RNA.
Hormones (Greek meaning to excite) are chemical substance that has their site of synthesis and action at different places in an organism. They are secreted and synthesized by specialized endocrine glands. Mostly, fall under they four categories;
Polypeptides
Amino acid derivatives
Steroids
Eicosanoids
Polypeptide hormones
Insulin is one of the most important polypeptide hormones. It was discovered by Banting and Best is 1922 and sequenced in 1955 by Fred Sanger. About 20 years later, Stainer discovered that the two polypeptide chains of insulin are synthesized as a single polypeptide, proinsulin, which folds and is crosslinked by disulfide bonds. The internal peptide is then removed by the concerted action of specific proteases. All these events occur in pancreatic beta cells that synthesize insulin.
All polypeptide hormones are synthesized as large precursors. Some examples of polypeptide hormones are oxytocin, vasopressin, glucagon, Thyrotropin-releasing hormone (TRH) etc.
Amino acid derivatives:
Thyroid hormones and epinephrine are amino acid derivatives. Thyroxine (T4) and the more potent triiodothyroxin (T3) are cleaved from a large precursor protein called thyroglobulin. Thyroglobulin exists as a dimer of two identical polypeptides. It is a strange protein for iodine and can be considered a prehormone of the circulating thyroid hormone.
Thyroglobulin is excreted into the lumen of the thyroid gland, where specific residues are iodinated in one or two positions by special peroxidases. Then two iodinated residues condense and ultimately lysed from the protein in form of hormone. The whole processing takes place on the protein itself.
Epinephrin
Sometime epinephrine also called as adrenalin. Its precursors-norepinephrin are synthezed from tyrosine in cells of adrenal medulla.
Steroid hormones
Steroid hormones are derived from cholesterol: Steroid hormones are derived from cholesterol by stepwise removal of carbon atoms and hydroxylation. They are synthesized by cells of the adrenal cortex and the gondas (e.g. estrogen progestrons, androgens)
Mode of action
Many hormones, especially water soluble ones, do not enter the cells and exert their influence by binding to the receptor proteins and communicate through small molecules. The best-understood messenger is cAMP. Some hydrophilic hormones, like thyroxine and steroid, enter the cells and bind to specific receptors within the cytoplasm of target tissues. These together may directly bind the DNA and influence the cell metabolism.
When one of the primary alcohol groups is modified, the molecule becomes asymmetric, i.e., it can be written as L-glycerol-3-phosphate or D-glycerol 1-phosphate. Hence IUB (The International Union of Biochemists) have recommended that glycerol written in Fisher’s formula with the hydroxyl group on the central carbon if placed on the left, the top carbon is numbered as one and the bottom carbon as number three. This system of numbering is stereospecific numbering (Sn), and this prefix is used in naming asymmetric glycerol derivatives.
This process of breaking ester linkage between fatty acid and glycerol by the addition of three water molecules is termed as hydrolysis, whereas splitting triglycerides by alkali is called saponification. The product formed is glycerol and sodium salt of fatty acids (soaps).
