Central Department of Chemistry

Central Department of Chemistry
Me @ Central Department of Chemistry(CDC), Kirtipur, Kathmandu, Nepal

Friday, June 16, 2017

Pregnant Women and Coffee

“Coffee, for many of us, is a daily fix. But few would relate to it as being a life changer” – this is what BBC (27th Feb, 2013 issue) writes by narrating a story of Nepali farmer whose life was changed by farming coffee instead of regular maize and paddy cultivation. Nepalese coffee is different from other countries. People mainly produce Arabica type of coffee which is organic. But, what about intake of coffee by Nepalese women? Frankly, in Nepal tea is preferred than coffee. Most of the people in the rural area take milk-added-tea which is considered more harmful than black tea. Let’s know something about caffeine, a key component in coffee and its effect on the pregnant women.

Caffeine is a natural component of coffee, tea, and cocoa products. It is added to many soft drinks and to certain prescription and over-the-counter medications. Caffeine's pharmacologic effects include central nervous system stimulation, bronchodilation, and higher blood pressure, most likely through antagonism of adenosine receptors in the brain, heart, lungs, and blood vessels. Based on a recent survey by the U.S. Department of Agriculture, coffee, soft drinks, and tea (in that order) are the major sources of caffeine among adults. Average caffeine intake is estimated to be 164 mg per day among women 18–34 years and 125 mg per day among pregnant women. In a prospective cohort study conducted in Connecticut during 1988–1992, caffeine consumption during the first month of pregnancy was reported by 60% of study participants, with 16% consuming 150 mg or more of caffeine per day.

Caffeine is teratogenic in animal studies when administered at high concentrations. There is no evidence to support a teratogenic effect of caffeine in humans. Current epidemiologic evidence is not adequate to assess the possibility of a small change in risk of congenital anomalies resulting from maternal caffeine consumption.

Picture from Google on 16th June 2017 
Marilyn Brown has published a review paper in epidemiology journal by evaluating methodological aspects of epidemiologic studies of maternal caffeine exposure and risk of congenital anomalies1. He has reported that there is no evidence that caffeine intake causes a large increase in the risk of various types of congenital anomalies, but there is greater uncertainty about small elevations in risk. Given the relatively high prevalence of maternal caffeine exposure, even a small increase in the risk of congenital anomalies would have an important effect on public health. 

Large study populations and improved exposure assessment methods would be necessary to rule out small risks for specific categories of congenital anomalies after maternal exposure to caffeine.
In the United States, some 60 percent of women continue to drink caffeinated coffee during their first month of pregnancy.  About 16 percent of pregnant mothers consume 150 mg of caffeine or more per day. But the question is, Is this harmful to your unborn baby? Three things to know.  One, caffeine can freely cross the placenta.  Two, 90 percent of a mother’s caffeine level reaches the developing fetus.  Three, the half-life of caffeine is much longer in the fetus than in the adult2.
Some studies have shown a correlation between prenatal caffeine consumption and decreased birth weight.  But are there longer-term consequences? Researchers in Florida studied mice that had were exposed to physiologically relevant doses of caffeine in utero.  They found that caffeine significantly altered the expression of genes in embryonic hearts.  Pathways related to cardiovascular development and diseases were significantly affected by caffeine. The researchers stress that “the long-term effects of caffeine on human cardiac function are unclear.”  They recommend further studies “to evaluate the safety of caffeine exposure during human pregnancy.”

1.         Browne, M. L., Maternal exposure to caffeine and risk of congenital anomalies: a systematic review. Epidemiology 2006, 17 (3), 324-331.
2.         Fang, X.; Mei, W.; Barbazuk, W. B.; Rivkees, S. A.; Wendler, C. C., Caffeine exposure alters cardiac gene expression in embryonic cardiomyocytes. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 2014.

Friday, November 18, 2016

Viagra (Sildenafil) And Its Chemistry

     Erectile dysfunction is a common problem faced by elderly men. According to a report, about 60% of men older than 60 and 70% of those in their 70s have trouble getting or maintaining erections, often because of diabetes, cardiovascular disease or prostate cancer treatment. Not all of them want treatment, of course. A large proportion of older men have lost sexual interest, don’t have a partner or have other illnesses that preclude sexual activity. Paula Span writes in The New York Times (July 31, 2015 issue) on a heading “Sex Never Dies, but a Medicare Option for Older Men Does”. Yes, it does. She also writes that Medicare (Government medical insurance in USA) stopped covering erection pumps from July 1, 2015 an indication, some experts say, that the sexual health of older adults is not taken seriously. These erection pump treatment option naturally pulls blood into the erectile tissues to help men maintain an erection without medication or invasive procedures. That is another aspect to be discussed. Here, I want to discuss about the medication suggested by experts for erectile dysfunction and its chemistry.
    Viagra (sildenafil) is a suggested medicine for the erectile dysfunction for men (also women) that relaxes muscles found in the walls of blood vessels and increases blood flow to particular areas of the body. It has been since long to treat erectile dysfunction (impotence) in men. Another brand of sildenafil is Revatio, which is used to treat pulmonary arterial hypertension and improve exercise capacity in men and women. The chemical formula of Viagra is C22H30N6O4S and its IUPAC name is 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d] pyrimidin-5-yl)-4-ethoxyphenyl] sulfonyl]-4-methylpiperazine citrate.
Pfizer scientists Andrew Bell, David Brown, and Nicholas Terrett originally discovered sildenafil as a treatment for various cardiovascular disorders. Since becoming available in 1998, sildenafil has been a common treatment for erectile dysfunction; its primary competitors are tadalafil (Cialis) and vardenafil (Levitra). Beside the treatment of erectile dysfunction, sildenafil is also used in pulmonary hypertension. While sildenafil improves some markers of disease in people with pulmonary arterial hypertension, it does not appear to affect the risk of death or serious side effects as of now. Furthermore, it has also been used as antidepressant-associated sexual dysfunction. Tentative evidence suggests that sildenafil may help men who experience antidepressant-induced erectile dysfunction. In addition, the altitude sickness problem has been solved surprisingly by it. Sildenafil appears to improve some risk factors for high-altitude pulmonary edema but it is unclear whether or not it affects the rate of the condition itself.
    There are few side effects due to the administration of this drug in human body. Common side effects include headaches and heartburn, as well as flushed skin. Caution is advised in those who have cardiovascular disease. Rare but serious side effects include prolonged erections, which can lead to damage to the penis, and sudden-onset hearing loss. Sildenafil should not be taken by people who take nitrates such as nitroglycerin (GTN), as this may result in a severe and potentially fatal drop in blood pressure. Let’s know how this drug acts on the targeted area.
Mode of Action
Schematic illustration adopted from Peter Volsky
  Robert F. Furchgott, Ferid Murad, and Louis Ignarro won the Nobel Prize in Physiology or Medicine in 1998 for their independent study of the metabolic pathway of nitric oxide in smooth muscle vasodilation. In their study, they found that Sildenafil (Viagra) protects cyclic guanosine monophosphate (cGMP) from degradation by cGMP-specific phosphodiesterase type 5 (PDE5) in the corpus cavernosum. A corpus cavernosum is one of a pair of sponge-like regions of erectile tissue, which contain most of the blood in the penis during an erection. Nitric oxide (NO) in the corpus cavernosum of the penis binds to guanylate cyclase receptors, which results in increased levels of cGMP, leading to smooth muscle relaxation (vasodilation) of the intimal cushions of the helicine arteries. The helicine arteries of penis are arteries in the penis which are involved in the process of erection. This smooth muscle relaxation leads to vasodilation and increased inflow of blood into the spongy tissue of the penis, causing an erection. 
   Sildenafil is best regarded as a potent and selective inhibitor of cGMP-specific phosphodiesterase type 5 (PDE5), which is responsible for degradation of cGMP in the corpus cavernosum. Various researches have shown that the molecular structure of sildenafil is similar to that of cGMP and acts as a competitive binding agent of PDE5 in the corpus cavernosum, resulting in more cGMP and better erections. Without sexual stimulation, and therefore lack of activation of the NO/cGMP system, sildenafil should not cause an erection. Other drugs that operate by the same mechanism include tadalafil (Cialis) and vardenafil (Levitra).
      After its desired action, Sildenafil is broken down in the liver by hepatic metabolism using cytochrome p450 enzymes, mainly CYP450 3A4(major route), but also by CYP2C9 (minor route) hepatic isoenzymes. The major product of metabolisation by these enzymes is N-desmethylated sildenafil, which is metabolised further. This metabolite also has an affinity for the PDE receptors, about 40% of that of sildenafil. Thus, the metabolite is responsible for about 20% of sildenafil's action. Sildenafil is excreted as metabolites predominantly in the feces (about 80% of administered oral dose) and to a lesser extent in the urine (around 13% of the administered oral dose). If taken with a high-fat meal, absorption is reduced; the time taken to reach the maximum plasma concentration increases by around one hour, and the maximum concentration itself is decreased by nearly one-third.

Saturday, July 9, 2016

Cool Chemistry!!!

Chemistry is always cool! I am letting you know some interesting chemistry facts which you may not know:
1.There is enough gold in the earth crust which is sufficient to deep knee.
2. In the early 1940s a large portion of the world’s plutonium supply was accidentally ingested by a lab technician. The majority of plutonium, like other heavy metals, passes right through your digestive tract. 
3. Did your high school tell you there are three states of matter? Solid, liquid, gas. Or Maybe they threw in a fourth state, plasma. In fact, there are many more than just three or four states of matter. Around absolute zero a lot of funny things happen and new states of matter pop up, like Bose-Einstein condensates which defy gravity.
4. Watson and Crick, the co-discoverer’s of the DNA double helix never actually ran any experiments on their own, but rather read deeply into others’ work and deduced the structure.
5. Lithium can alter how you think and has been known to “cure” certain mental illnesses. In fact, lithium is used in a lot of psychoactive drugs.
6. One of the first x-rays, a picture you’ve probably seen of a woman’s hand with a ring on it, was of Bertha Rontgen’s hand. She thought seeing her bones was a death omen.
7. Hot water freezes quicker than cold water.
8. People used to drink radioactive water from a device called the “Revigator.” It was considered to be a healthy drink.
9. Diamonds aren’t the rarest gems on Earth. In fact, they’re relatively common. The rarest gem is jadeite and costs about $3 million per carat.
10. Only 28 grams of the rarest substance on Earth exist. What’s the rarest substance on Earth? Astatine.
11. Gallium, a metal element, will melt in your hand.
12. Liquid oxygen is blue.
13. The letter J is the only letter that doesn’t appear in the periodic table.
14. Every time lightening strikes, ozone is created.
15. You may think that tropical seeds can not tolerate very very cold temperature but scientists have found that tropical seeds even can tolerate that even -190 degree centigrade. 
16. The lighter was invented before the match (in 1816 by J.W. Dobereiner).
17. Glass is actually a liquid, it just flows very, very slowly. Same with asphalt.
18. Our body has enough carbon which is sufficient to make/fill 9,000 lead pencils.
19. Use of plastic is very dangerous to the earth due to its long term effect. It is said that a plastic container can resist decomposition for as long as 50,000 years. 
20. Do you know why tungsten is used in electric bulbs? This is because its melting point is highest (3410 Degree Centigrade).

Thursday, March 24, 2016

The Sense of Falling in Love With Chemistry

    Chemistry is all around us all the time. I am  able to write this and you are able to read and understand this sentence because chemical reaction are taking taking place in my and your brain. The food we ate for break-fast or lunch is now furnishing energy through chemical reactions. Trees and grass grow because of the chemical changes.
Chemistry also crops up in some unexpected places. When archaeologist Luis Alvarez was studying in college, he probably did not realize that the chemical elements iridium and niobium would make him very famous when they helped him solve the problem of the disappearing dinosaurs. For decades scientists had wrestled with mystery of why the dinosaurs, after ruling the earth for millions of years, suddenly became extinct 65 million years ago. In studying core samples of rock dating back to the period, Alvarez and his co-workers recognized unusual levels of iridium and niobium in these samples-levels much more characteristic of extraterrestrial bodies than of the earth. Based on these observations, Alvarez hypothesized that a large meteor hit the earth 65 million years ago, changing atmospheric conditions so  much that the dinosaur' food couldn't grow, and they died-almost instantly in the geologic timeframe!
     Chemistry is also very important to the historians . Did you realize that lead poisoning probably was a significant contributing factor to the decline of the Roman Empire? The Romans had high exposure to lead-glazed pottery, lead water pipes, and a sweetening syrup called sapa that was prepared by boiling down grape juice in lead lined vessels. It turns out that one reason for sapa's sweetness was lead acetate (sugar of lead) that formed as the juice was cooked down. Lead poisoning with its symptoms of lethargy and mental malfunctions certainly could have contributed to the demise of the Roman Society. 
      Chemistry is also apparently very important in determining a person's behavior. Various studies have shown that many personality disorders can be linked directly to imbalances of trace elements in the body. For example: studies on the inmate at Stateville Prison in Illinois have linked low cobalt levels with violent behavior. Lithium salts have been shown to be very effective in controlling the effects of manic depressive disease, and you have probably at some time in your life felt  a special " Chemistry" for another person. Studies shows that there is literally chemistry going on between two people who are attracted to each other. "Falling in love" apparently causes changes in the chemistry of the brain; chemicals are produced that give that "high" associated with a new relationship. Unfortunately, these chemical effects seem to wear off over time, even if the relationship persists and grows. 
The importance of chemistry in the interactions of people should not really surprise us, since we know that insects communicate by emitting and receiving chemical signals via molecules called pheromones. For example: ants have very complicated set of chemical signals to signify food sources. danger, and so forth. Also, various female sex attractants have been isolated and used to lure males into traps to control insect populations. It would not be surprising if humans also emitted chemical signals that we were not aware of on a conscious level. Thus chemistry is pretty interesting and pretty important.

Source: Chemistry Instructor's Annotation, Zumdahl (7th Edition)

Friday, June 12, 2015

Fluorescence Spectroscopy: Simplified

Fluorescence spectroscopy measures the intensity of photons emitted from a sample after it has absorbed photons. Most fluorescent molecules are aromatic. Fluorescence is an important investigational tool in many areas of analytical science, due to its high sensitivity and selectivity. It can be used to investigate real-time structure and dynamics both in solution state and under microscopes, particularly for bio-molecular systems.

How does it work?

Fluorescence occurs when a fluorescent capable material (a fluorophore) is excited into a higher electronic state by absorbing an incident photon and cannot return to the ground state except by emitting a photon. The emission usually occurs from the ground vibrational level of the excited electronic state and goes to an excited vibrational state of the ground electronic state. Thus fluorescence signals occur at longer wavelengths than absorbance. The energies and relative intensities of the fluorescence signals give information about structure and environments of the fluorophores.
The component parts necessary within a typical Fluorescence Spectrometer (Spectrofluorometer) are a sample holder, incident photon source (typically a xenon lamp), monochromators used for selecting particular incident wavelengths, focusing optics, photon-collecting detector (single, or preferably multiple channel) and finally a control software unit. An emission monochromator or cut-off filters are also usually employed. The detector is usually set at 90 degrees to the light source. The intrinsic sensitivity of fluorescence is also its biggest problem and care must be taken to record a true fluorescence signal of the analyte of interest.
A fluorescence emission spectrum is recorded when the excitation wavelength of light is held constant and the emission beam is scanned as a function of wavelength. An excitation spectrum is the opposite, whereby the emission light is held at a constant wavelength, and the excitation light is scanned as a function of wavelength. The excitation spectrum usually resembles the absorbance spectrum in shape.
Most materials are not naturally fluorescent. However, useful data, particularly in fluorescence microscopy can be obtained by staining non-fluorophores with an active label.

  1.         Studies of molecular structures and molecular interactions
  2.             Localization of molecules (esp. in biological systems) and in types of trace analysis.
  3.             Changes in fluorescence intensity can be used to probe structural changes or binding of two molecules. The wavelength of tryptophan fluorescence can be used to determine whether a tryptophan is in an aqueous environment (longer wavelength) or buried deep within the protein (shorter wavelength).
  4.           Fluorescence polarization anisotropy allows mobility of fluorophores to be studies.

  1.           Sensitivity: Pico gram quantities of luminescent materials can be frequently studied.
  2.        Selectivity: Deriving in part from the two characteristic wavelengths (excitation, fluorescence) of each compound.
  3.          The variety of sampling methods available: dilute and concentrated suspensions and solid surfaces can all be readily studied and combinations of fluorescence spectroscopy and chromatography.


  1.          With high pressure Xenon lamps which are still widely used as light sources.
  2.           These lamps contain gas at several atmosphere pressure and thus should be handled with great circumspections (eye protection, gloves, chest protection recommended).
  3.       Always operate in dust free environment with small temperature variation.
  4.           Extreme precautions must be considered with regards to the cleanliness of cells. Fingerprints exhibit substantial fluorescence.
  5.           Samples should be stored in clean glass vessels (not in plastic containers.


Friday, February 20, 2015

Why being in Love feels so good?

I have been blogging about the Chemistry since 2011. What I love about chemistry is the constant sense of discovery: looking at the simplest reactions on a molecular level is like glimpsing a whole new world. I am also fascinated with the vast research going on Chemistry, which is a boon to the human kind. During the course of my intermediate (+2), bachelors and masters degree I hope to take part in some research. After leaving Tribhuvan University (TU) I began to teach to the B.Sc. students as well as the intermediate(+2) students. I think my desire for acquiring the knowledge in Chemistry will not be quenched even after my Ph.D. I will be looking to work in academic science, possibly in research, and some experience will almost certainly come in useful.
In the previous days,  I blogged mainly on material Chemistry. Recently, a bizarre interest arose within me to write few words on the abstract Chemistry…particularly on the “Chemistry Behind Love”.
Have you ever wondered how much of love is about the heart… and how much is about hormones? And what about chemistry—can you create it, or does it just happen? Most of us have pondered such issues.
Actually, LOVE is due to the Chemical known as Dopamine, which produce feelings of euphoria, energy, sleeplessness, and focused attention on your beloved. That’s why being in love feels so good. Due to dopamine some of the most powerful brain circuits for pleasure are triggered and people experience similar to a cocaine high.

Dopamine is a neurotransmitter released by the brain that plays a number of roles in humans and other animals. Some of its notable functions are: movement, memory, pleasurable reward, behavior and cognition,attention, inhibition of prolactin production, sleep mood, learning etc. Dopamine is the chemical that mediates pleasure in the brain. It is released during pleasurable situations and stimulates one to seek out the pleasurable activity or occupation. This means food, sex, and several drugs of abuse are also stimulants of dopamine release in the brain. Excess and deficiency of this vital chemical is the cause of several disease conditions. Parkinson's disease and drug addiction are some of the examples of problems associated with abnormal dopamine levels.
Dr. Helen Fisher, anthropologist of Rutgers University, who is also the author of a book  “Why We Love”. Her noteworthy career has been dedicated to understanding love—how and why it functions for us humans. Once she was asked how important a role does chemistry play in love. Dr. Fisher answered that when the chemistry of one personality meshes well with the chemistry of another, it will continually combust throughout the relationship—keeping both partners together and happy during dry spells when feelings of romance are low. She also said that having sex makes people fall in love because probably after orgasm, there is a peak in dopamine activity.
Beside the Dopamine, Oxytocin and Vasopressin chemicals play a vital role in attachment. The important hormones like Testosterone and Estrogen are responsible for the lust.

Friday, January 30, 2015

Chemical Education In Nepal: Problems, Efforts and Progress

Tribhuvan University (TU), Nepal has commenced teaching, research, and other academic activities from July 14, 1959. Master's Degree in Chemistry was started only from November 28, 1965.
Within 56 years since the establishment of TU,  the country’s oldest university, there has been little focus on intensive research into science and technology.
There are nine Universities in Nepal. All these universities in the country are keener on handing out affiliations to new private undergraduate schools rather than empowering themselves. TU has 60 constituent campuses and more than 800 affiliated colleges throughout the country. The University has central departments in most disciplines at its Kirtipur campus, which enrolls 90 M.Sc. students each year in Chemistry, 120 in Physics, 48 in Microbiology, 48 in Environment sciences and 90 in Mathematics.
After the completion of final exam, only 30% meritorious students get the opportunity for a Master’s Thesis Research in Chemistry. Moreover, the department has not been able to expand itself beyond the traditional physical, inorganic and organic chemistry disciplines, probably due to the lack of funding and expertise. Recently, TU expanded its M.Sc program in Chemistry to its regional campuses like Tri-Chandra Campus (90 students), Birendra Campus, Bharatpur (60 students) and Mahendra Morang Campus, Biratnagar (60 students) but these programmes too are mostly teaching oriented. The situation is not very different in other universities either.

What is the problem?
·         Nepal Government allocates very less amount of money for the research and maintenance of the department. The prime minister is also chancellor of Nepal’s university system. Similarly, the Education Minister holds the office of pro-chancellor. To hire the top brass of the university, a search committee, recommends names to the associate-chancellor. Then a vice-chancellor is recruited by the prime minister upon the recommendation of the pro-chancellor. Unfortunately, over the past 10 years, the top posts of vice-chancellor, rector, and registrar have been distributed among the major political parties.
·         Faculties within the department are hiring lecturers with Master’s degrees but with no or little research experience. Recently, it was  seen that three masters degree holders were hired representing each from three big parties. Unlike in developed countries, the hiring process is primitive and takes years to complete.
·         Extreme politicizing for a minor event.
·         Lack of energetic staff members in the Central Department of Chemistry (CDC).
·         Professors  in CDC are blamed for working for their political party of  their interest rather than empowering the department.

Key Note
A sensible way to fix this crisis would be to create an educational system where the vice-chancellor and other top policymakers are appointed by a non-political committee composed of experienced and capable scholars with expertise in a variety of fields. If efforts are made to hire candidates with vision beyond politics, many of the current problems facing the Nepali education system will be resolved. Only then will Nepal’s Universities be fast movers in research and innovation. We should set ambitious goals in science and technology; some great initiatives have been undertaken but more need to be done to reform chemical science studies in Nepal.

A dawn of hope:
A handful of energetic and young chemists are working to develop chemical science in Nepal. Several conferences and symposiums are conducted yearly.  The Nepal Chemical Society and TU organized a big International Chemical Science Conference, called ‘Chemical Congress’, in 2008 in Kathmandu. The conference brought national and international exposure to many students, chemists, and professionals in the advancement of chemical science. Since then, other conferences, such as ‘Polychar International Conference on Advance Materials and Nanotechnology’ and ‘Kathmandu Symposia on Advanced Materials’ have been organised every year and are led by a prominent professor of chemistry at the TU Central Department of Chemistry, Rameshwar Adhikari. These conferences have been successful in bringing many international scientists, including Noble laureates, to Nepal from more than 20 countries.
A research lab is now being established at the Department of Chemistry in the Mahendra Morang Adarsh Multiple Campus of TU at Biratnagar under the initiation of a very energetic chemist, Ajaya Bhattarai. Inspite of  several problems he appealed for funds with friends and other chemists who are studying abroad and brought  UV-Visible spectrophotometer. Hats off to Ajaya Bhattarai for his relentless efforts for the development of Chemical Science in Nepal!
Source: Kosh Neupane Oak Ridge National Laboratory in Tennessee, the US (koshalnp@hotmail.com)

Tuesday, January 13, 2015

What affects the color of meat?

In our daily life, when we go to the grocery or meat shop, we see that some meat is red whereas some meat is pale. What causes the change in color of meat? Actually, the muscle that are frequently used are red where as those infrequently used are pale in color. We can notice that the leg meat of chicken is darker and the breast meat is white. The different colors of meat reflect the concentration of myoglobin in the muscle tissue.
What is myoglobin?
Myoglobin is the globular protein that functions as an oxygen storage in muscles. Myoglobin is a monomer whereas hemoglobin is a tetramer. That is, myoglobin consists of a single peptide chain and a heme unit, and hemoglobin has four-peptide chains and four heme units. Thus only one oxygen molecule can be carried by a myoglobin molecule. Myoglobin has a higher affinity for oxygen than does hemoglobin. Thus, transfer of oxygen from hemoglobin to myoglobin occurs readily. Oxygen stored in myoglobin molecules serves as a reserve oxygen source for working muscles when their demand for oxygen exceeds that which can be supplied by hemoglobin.
 The meat that humans eat is composed primarily of muscle tissue. The major proteins present in the muscle tissue are myosin and actin, which lie in alternating layers and which slide past each other during muscle contraction. Contraction is temporarily  maintained through interactions between these two types of proteins.
Structurally, myosin consists of a rod like coil of two alpha helices (fibrous protein) with two globular protein  heads. The head portions of myosin interact with the actin.
Structurally, actin has the appearance of two filaments spiraling about one another. Each circle in the structural diagram represents a monomeric unit of actin (called globular actin). The monomeric actin units associate to form a long polymer (called fibrous actin). Each identical monomeric  actin unit is a globular protein containing many amino acid residues.
The chemical process associated with muscle contration ( interaction between myosin and actin)  requires molecular oxygen. The oxygen storage protein myosin is the oxygen source. The amount of myoglobin present in a muscle is determined by how the muscle is used. Heavily used muscle require larger amount of myoglobin than infrequently used muscles require.
The amount of myoglobin present in muscle tissue is a major determiner of the color of the muscle tissue. Myoglobin molecules have a red color when oxygenated and a purple color when deoxygenated. Thus, heavily worked muscles have a darker color than infrequently used muscles.
The different colors of meat reflect the concentration of myoglobin in the muscle tissue. In turkeys and chickens, which walk around a lot but rarely fly , the leg meat is dark, the breast meat is white.  On the other hand, the flying birds have dark breast meat.
Fish have lighter flesh than the land animals and birds because they do not need to support their own weight (supported by water) while moving/swimming.  This reduces the need for myoglobin oxygen support.    The fish that spend most of their time lying on the bottom of a body of water have lightest meat.
Why meat turns brown in cooking?
Meat, when cooked, turns brown as a result of changes in myoblobin structure caused by the heat; the iron atom in the heme unit of myoglobin becomes oxidized. When meat is salted with preservatives (NaCl, NaNO2 etc.) the myoglobin picks up nitrite ions, and its color changes to pink.

Sunday, November 23, 2014

How to make Chemistry an interesting Science?

Chemistry is often described as the Central Science, highlighting its importance to numerous scientific disciplines, such as Biology, Biomedical and Chemical Engineering, Forensics, Geosciences, Materials Science, Toxicology and many more. It is the study of the structure and transformation of matter. It.is very difficult to say when the documentation of chemistry began from. When Aristotle wrote the first systematic treatises on chemistry in the 4th century BCE, his conceptual grasp of the nature of matter was tailor
ed to accommodate a relatively simple range of observable phenomena. In the 21stcentury, chemistry has become the largest scientific discipline, producing over half a million publications a year ranging from direct empirical investigations to substantial theoretical work.
Why study Chemistry? Many students take this question in mind when they feel difficult in the beginning phase. Well, understanding chemistry helps you to understand the world around you. Cooking is chemistry. Everything you can touch or taste or smell is a chemical. When you study chemistry, you come to understand a bit about how things work. Chemistry isn't secret knowledge, useless to anyone but a scientist. It's the explanation for everyday things, like why laundry detergent works better in hot water or how baking soda works or why not all pain relievers work equally well on a headache. If you know some chemistry, you can make educated choices about everyday products that you use.
This central science has certain difficulties among the beginners of chemistry. Let’s call them as pitfalls in Chemistry. The pitfalls in chemistry can be outlined in different headings. New words and new symbols are the first thing beginners usually trip of. If misunderstanding these new words and symbols is not addressed, it is very difficult to survive. Its effects are immediate and is the usual reason people give up on their exploration of chemistry. The remedy is to find those words or symbols and get a good explanation or definition for them. When looking up the meaning of words, it’s better to try to find the origin of the word and try to understand the words in a funny manner.
The second pitfall is learning without having enough reality on the subject. This means the student only have an abstract or vague familiarity with the subject. The initial reaction to a misunderstood word or symbol is that the mind goes blank. This is my own experience. Have you ever been reading a book and got to the bottom of the page and realized you don’t remember a word you just read? I have witnessed students reading a paragraph out loud, and when they came to a misunderstood word, they skipped right over it and didn't even realize that they had skipped it. Their mind just went blank when they saw it. If that happens to you when studying chemistry, back up and find the misunderstood word or symbol. Perhaps it will work.
The third pitfall is "jumping in over your head;" in other words, you move too fast by tackling difficult tasks without first mastering the simpler tasks. The symptoms may be feeling irritated, impatient and distracted. This is also the sequential cause of misunderstood words and/or misunderstood symbols. Once the mind disconnects from the subject matter due to misunderstood words, students find themselves growing more impatient, irritated, or distracted. Even little things annoy them. If this happens, go back and find the misunderstood words and learn their meanings. Furthermore, try to learn interesting facts about chemistry. They create interest in the subject matter. Do you know, lightning strikes produce O3, which is ozone, and strengthen the ozone layer of the atmosphere? Although oxygen gas is colorless, the liquid and solid forms of oxygen are blue. The human body contains enough carbon to provide 'lead' (which is really graphite) for about 9,000 pencils. One bucket full of water contains more atoms than there are bucket fulls of water in the Pacific Ocean. Is it amazing? Catch up chemistry you will feel amazed every day!

Saturday, November 1, 2014

Garlic: Chemistry behind Antibiotic Nature and Uses

Garlic is extensively used in the kitchen world-wide. It is an herb. Now-a-days the price of garlic is sky-rocketing not only in South Asia but as a whole in this world. When I was in my college life, I used to wonder why this bad smelling stuff has high price in comparison to other vegetables. Later, I found that it was a natural antibiotic! Amazingly, garlic can kill the antibiotic resistant Staphylococus aureus and Salmonella enteritidis too. Here, I have posted the chemistry behind its antibiotic property and its medicinal uses.
Research has identified four major chemical compounds in garlic viz. diallyl disulfide, allyl methyl sulfide, allyl mercaptan, and allyl methyl disulfide. Sulfur-containing compounds are involved in the antibacterial properties of garlic. Researchers tested these compounds on a type of bacteria found in animal faeces (E.coli), one of the most common bacterial causes of gastroenteritis, and found that the anti-microbial activity of the compounds increased with the number of sulfur atoms present; diallyl trisulfide being the most effective, followed by diallyl disulfide, then diallyl sulfide. These compounds are effective as they can penetrate the cell membranes of bacteria cells, and cause changes in structure in thiol (-SH) containing enzymes and proteins, injuring the cell.
Garlic is best known as a flavoring for food. Some scientists have suggested that it might have a role as a food additive to prevent food poisoning. But over the years, garlic has been used as a medicine to prevent or treat a wide range of diseases and conditions. Garlic is used for many conditions related to the heart and blood system. These conditions include high blood pressure, high cholesterol, coronary heart disease, heart attack, and “hardening of the arteries” (artherosclerosis). Some of these uses are supported by science. Garlic actually may be effective in slowing the development of atherosclerosis and seems to be able to modestly reduce blood pressure. Some people use garlic to prevent colon cancer, rectal cancer, stomach cancer, breast cancer, prostate cancer, and lung cancer. It is also used to treat prostate cancer and bladder cancer.

Garlic has been tried for treating an enlarged prostate (benign prostatic hyperplasia; BPH), diabetes, osteoarthritis, hay fever (allergic rhinitis), traveler's diarrhea, high blood pressure late in pregnancy (pre-eclampsia), cold and flu. It is also used for building the immune system, preventing tick bites, and preventing and treating bacterial and fungal infections.

Other uses include treatment of fever, coughs, headache, stomach ache, sinus congestion, gout, rheumatism, hemorrhoids, asthma, bronchitis, shortness of breath ,low blood pressure, low blood sugar, high blood sugar, and snakebites. It is also used for fighting stress and fatigue, and maintaining healthy liver function.

Some people apply garlic oil to their skin to treat fungal infections, warts, and corns. There is some evidence supporting the topical use of garlic for fungal infections like ring worm, jock itch, and athlete’s foot; but the effectiveness of garlic against warts and corns is still uncertain.

Sources: WHO, WebMed