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  1. page polylactic_acid edited ... of Plastic Megan BroccoOrganic Molecules ProjectChemistry 263 Polylactic acid (PLA) is a b…
    of Plastic
    Megan BroccoOrganic Molecules ProjectChemistry 263
    Polylactic acid (PLA) is a biocompatible and biodegradable polymer with a wide range of applications. A biodegradable polymer is a large molecule composed of repeating subunits, called monomers, that can be broken down by microorganisms[1]. PLA has recently attracted a lot of attention from advocates of sustainable development and green chemistry. It is made from renewable resources, has a small carbon footprint and is an environmentally friendly compound with properties that can commercially compete with nonbiodegradable polymers such as petroleum based plastics [2].
    PLA belongs to a group of aliphatic polyesters that are synthesized from a-hydroxy acids (AHAs). An aliphatic polyester is a non-aromatic polymer that contains many ester groups. AHAs are compounds that contain a carboxylic acid group adjacent to a carbon with a hydroxyl group and include lactic acid, citric acid, and glycolic acid [1]. The building block, or monomer, for PLA synthesis is lactic acid (2-hydroxypropionic acid). Lactic acid is a water-soluble and chiral molecule produced from the bacterial fermentation of dextrose, an extract from carbohydrate renewable resources such as corn starch, cane sugar, or potatoes [1]. The Lactobacilli bacteria give high yields of the L isomer [2].
    Figure 1. Synthesis of lactic acid from dextrose, a simple sugar commonly found in nature.
    Lactic acid is difficult to polymerize by the direct condensation of lactic acid because the water that is formed by joining two lactic acid molecules hydrolyzes the newly created ester bond and results in a low molecular weight product [1,3]. Therefore, the ring-opening polymerization of lactide, a cyclic di-ester, is the most common method used to synthesize PLA [3]. In this esterifcation reaction, lactic acid is heated with an acid catalyst to form a dimer which then converts to lactide, a hexagonal ring with two ester groups [1,4].
    Figure 2. Synthesis of lactide, a cyclic diester, from lactic acid.
    Figure 3. Lactide synthesis results in three stereoisomers because lactic acid has a chiral center.
    Figure 4. Ring opening polymerization of lactide showing nucleophilic and electrophilic sites.
    Typically tin octoate or stannous octoate are used as catalysts for this reaction [3]. This method of synthesis greatly reduces the use of expensive and harmful solvents and results in a product that is biodegradable. In the presence of microorganisms and oxygen, PLA will naturally degrade to non-toxic carbon dioxide and water within a few weeks [1]. In addition, the ester linkages in PLA can be easily hydrolyzed with water to form lactic acid, the monomer for PLA synthesis. The hydrolysis is typically catalyzed by the carboxylic acid group located at the end of the chain that has a pKa of 3 [3]. This way, the PLA monomer can be recycled and used to make more PLA [3].
    Figure 5. Life Cycle of polylactic acid.
    The physical properties of PLA vary because the building blocks used in its synthesis come in different forms. For example, lactic acid has two optical isomers, L-lactic acid and D-lactic acid, while lactide has three optical isomers, L-lactide, D-lactide, and meso-lactide. This allows the properties of PLA to be modified by changing the ratio of L and D enantiomers of lactic acid used in the synthesis which affects the degree of crystallinity and many other important properties such as density, molecular weight, melt temperature, strength, and glass transition [1.3.5]. Depending on the L/D ratio, PLA can be semi-crystalline or amorphous, which reflects the structure of the polymer’s carbon backbone. In general, PLA behaves like polyethylene terephtalate (PET or PETE), a recyclable amorphous to semi-crystalline thermoplastic polymer that we commonly find in synthetic fibers, containers, and plastic bottles [4]. Like PLA, PET is synthesized from an esterification reaction. However, it’s monomer, bis-B-hydroxyterephthalate, is made using p-xylene, acetic acid solvent, cobalt and manganese catalysts, and bromide or ethylene glycol, dimethyl terephtalate and methanol instead of renewable resources [6]. PLA also acts like polypropylene, a tough and flexible thermoplastic polymer found in packaging, industrial textiles, piping, heat-resistant plastics, and floating rope[[#_edn1|[i]]]. In addition, the properties of PLA can be customized by adding plasticizers, biopolymers, and other fillers [2]. The variety of structures and physical properties that result from modifying all of these variables has therefore been the subject of much research in the scientific community. Chemists have been working hard to tailor the properties of PLA to make it practical for a wide variety of applications in addition to exploring the endless list of PLA blends that can be created using other polymers.
    A diverse assortment of products can be manufactured from PLA because its properties allow it to be stress crystallized, thermally crystallized, filled, and processed in many polymer manufacturing plants [3]. Biodegradability and non-hazardous materials makes PLA a great choice for post-consumer products that typically end up in landfills like plastic bags, food containers, and other packaging. Products can be fabricated from PLA by the following processes: injection molding (plastic bottles), sheet extrusion (plastic containers and truck bed liners), blow molding (hoses and pipes), film forming (wrappers) and fiber spinning (carpeting and fiberfill) [4]. In addition, the biocompatible properties of PLA allows it to be in contact with tissues and have many applications in the biomedical field [8.9]. Currently, PLA is used in the manufacture of sutures, stents, dialysis equipment and other medical devices. PLA has also found uses in tissue engineering where it is used as the artificial scaffold to support the three-dimensional growth of cells ex vivo and in vivo [10]. The scaffold gives cells a place to attach and grow, allows diffusion of nutrients, and gives support to the structure and shape of the growing tissue[11]. This application requires strong but malleable porous materials that are biocompatible and biodegradable so that the scaffold does not need to be surgically removed after the tissue has formed. PLA is even more competitive because it biodegrades into lactic acid, a naturally occurring compound that is easily removed from the body.
    In conclusion, PLA is a promising polymer with a wide variety of physical properties and applications. PLA is currently used in the production of packaging, textiles, and biomedical devices. PLA is similar to other petroleum-based polymers on the market but has a competitive edge because of the growing demand for non-toxic, environmentally friendly, and sustainable products that do not increase emissions or fill up landfills. PLA differs from these other recyclable plastics because it is made from renewable resources and biodegrades into naturally occurring compounds[12]. The biomedical and tissue engineering fields are also utilizing PLA’s unique properties especially because it is biocompatible and degrades. The production cost of PLA has been falling, allowing it to become more competitive with other polymers on the market. Cost no longer seems to be a factor limiting the use of PLA. Many scientists are focusing research on PLA and exploring the properties that can be achieved in the lab. Overall, it looks like PLA has the potential to change to plastics industry and that we will see a lot more of PLA in the future.
    [1] Bruice, P.Y. (2011). Organic Chemistry. Glenview, IL: Prentice Hall.
    [2] Averous, L. (2008). Polylactic Acid: Synthesis. Properties, and Applications. Retrieved from
    [3] Henton, D., et al. Polylactic Acid Technology. (2005). Retrieved from
    [4] Wikipedia. (2011). Polylactic acid. Retrieved from
    [5] Södergård, A., & Stolt, M. (2002). Properties of lactic acid based polymers and their correlation with composition. Progress in Polymer Science, 27 (6): 1123–1163. doi:10.1016/S0079-6700(02)00012-6
    [6] Wikipedia. (2011). Polyethylene terephthalate Retrieved from
    [7] Wikipedia. (2011). Polyproylene. Retrieved from
    [8] Middelton, J., & Tipton, A. (2000). Synthetic biodegradable polymers as orthopedic devices.Biomaterial, 21 (23), 2335–2346. doi:10.1016/S0142-9612(00)00101-0
    [9] Moran, J., et al. (2003). Characterization of Polylactic Acid–Polyglycolic Acid Composites forCartilage Tissue Engineering Tissue Engineering, 9 (1). Retrieved from
    [10] Chen, G., et al. (2002). Scaffold Design for Tissue Engineering. Macromolecular Bioscience, 2, 67-77. Retrieved fro
    [11] Tu, C., et al. (2003). The fabrication and characterization of poly(lactic acid) scaffolds for tissue engineering by improved solid–liquid phase separation. Center for Molecular Sciences, Institute of Chemistry, Chinese Academy of Science. Retrieved from
    [12] Royte, E. (2006, August). Corn plastic to the rescue. Smithsonian. Retrieved from

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  3. page melamine edited Melamine Melamine is a white crystalline organic base chemical with formula of C3H6N6 with a hi…

    Melamine is a white crystalline organic base chemical with formula of C3H6N6 with a high melting point that is used especially in melamine resins or plastic, and most commonly found in the form of white crystals rich in nitrogen.(1) The compound was invented in 1835 by a German scientist and becomes fashion as a material used to make plastics and laminates in the late 1930s. When combined with formaldehyde and exposed to extreme heat, melamine creates a moldable material that, when cooled, is virtually unbreakable and dishwasher-safe. [2]
    Melamine can also be used as a colorant and as fetilizer, however, it is not approved for these uses in the USA. There are no approved uses for the direct addition of melamine to food in the USA. Melamine can be produced from three different starting materials: urea, dicyandiamide or Hydrogen cyanide. Commercially produced melamine is manufactured using urea as a starting material.[3] The reaction for the production of melamine from urea is typically carried out in one or more stages using either a higher-pressure or a low-pressure process. The high-pressure process is performed in the liquid phase without a catalyst, at pressure of 90-150 bar and temperatures of 380-450 Celsius. In this process, urea is first converted to isocyanic acid, which then forms cyanuric acid. The cyanuric acid is then reacted with ammonia to form melamine. (Figure below) [4]
    Urea also known as carbamide is a waste product of many living organisms and is the major organic component of human urine. Urea is produced commercially by several steps, which begin with direct reaction of ammonia with carbon dioxide in a high pressure, high temperature reactor. It is a very important starting material in a number of chemical syntheses, and is used on an industrial scale for the manufacture of gertilisers, pharmaceuticals and resins. [5]
    In 2007, it was found in wheat gluten and rice protein concentrate exported from China and used in the manufacture of pet food in the United States. This caused the death of a large number of dogs and cats due to kidney failure. In the present event, melamine contamination has been found in a number of different brands of powdered infant formula, in one brand of a frozen yogurt dessert and in one brand of canned coffee drink. All these products were most probably manufactured using ingredients made from melamine-contaminated milk.
    After a Canadian pet food company announced it was voluntarily recalling food that was sickening pets, the U.S. Food and Drug Administration fielded thousands of similar complaints across the U.S. Soon after, a myriad of pet foods contaminated with the tainted gluten and protein from China were recalled from the market, but not before thousands of pets had died from renal failure. It has been established that oral exposure of diverse animal species (cats, dogs, rats, pigs and fish) to a combination of melamine and cyanuric acid in feed produces calculi that obstruct renal tubules, leading to acute renal failure. [6] Unfortunately, melamine has been used in food companies because its cheap and abundant filler substance for products ranging from livestock feed to pet food-and now, apparently, to baby formula. In some tests used to determine the nutritional value of a foodstuff, melamine shows up protein-so manufacturers can use the compound to make their products appear more nutritious. Melamine is not toxic, but inside the body it can cause kidney stones and renal failure.
    Animal studies have demonstrated that exposure to low levels of melamine produced no observable toxic effects. Exposures to high levels of melamine, or exposures to lower doses of melamine together with certain other chemicals, have caused urinary tract problems in animals. These have included urinary tract and kidney crystal and stone formation, and kidney failure. Exposures of animals to high doses of melamine over long time periods (years) have been associated with cancer of the bladder. [7]
    Works Cited
    1Kate Pickert. 17 Sep. 2008. 31May, 2011.,8599,1841757,00.html
    2Maxwell GR (2007). Synthetic nitrogen products. In: Kent and Rigel’s handbook of industrial chemistry and biotechnology, 11th ed. New York, NY, springer, pp 996-1085
    3Melamine in Food Products Manufactured in China. (2008, October 8). Retrieved from
    4 Merriam-Webster. Melamine. Retrived from
    5Paul May, Urea and Melamine. Retrieved from
    6Puschner B et al. (2007). Assessment of melamine and cyanuric acid toxicity in cats. Journal of Veterianary Diagnostic Investication, 19:616-624
    7W.H Tolleson(2009), Background Paper Chemistry. National Center for Toxicological Research, Food and Drug Administration. Web. 31 May, 2011
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  4. page nucleic_acids edited Chemistry of Nucleic Acids fagime was here Nucleic acids are macromolecules linked by many nucleo…
    Chemistry of Nucleic Acids fagime was here
    Nucleic acids are macromolecules linked by many nucleotides at phosphate groups. Each nucleotide is composed of a ring sugar (known as backbone) which binds to a phosphate group and a nitrogenous base. There are two types of nucleic acid: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is a blue print for organism’s life. It stores the genetic material which will be transmitted from parent to offspring. RNA is generated from DNA by transcription. The information in RNA is used to synthesis protein and amino acid which are essential for the function of cellular and organism [1].
    Nucleic acid was named because DNA was first found in the nuclei of white blood cells (an acidic environment) in 1869. Until 1951, Rosalind Franklin, who graduated from Cambridge University in London, worked in a lab at King’s College, and studied X-ray crystallography, figured out the structure of DNA through X-ray; Unfortunately, Franklin died in 1958 [2]. In 1953, James Watson and Francis Crick had visited Franklin’s lab and they had seen the X-ray of DNA that Franklin took. James Watson and Francis Crick had identified the three dimensional model of DNA, and they won the Nobel Prize in 1962.
    DNA is composed of two strands which are anti- parallel to each other. Each stand is a polynucleotide. Two strands connect to each other by hydrogen bonds between H with O, or N which are in bases [3]. This makes DNA look like a ladder. There are
    four types of base, which bind to sugar backbone, in nucleic acid: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). Adenine bind to Thymine and Cytosine binds to Guanine by hydrogen bonds. If one strand has Adenine, Thymine and Cytosine, so the other strand must have Thymine, Adenine and Guanine [3]. The difference of those bases and its arrangement makes different organism and species (due to genetic variation).
    Having Thymine as a base of structure of DNA also helps to prevent mutation for the following reasons: Cytosine can undergo deamination (a reaction of removing amino group) to become Uracil. When Uracil presents in DNA structure, it will be recognized by an enzyme as a mistake. The enzyme repairs this by cutting out the Uracil and replacing with Cytosine before DNA undergoes transcription process. Following is the mechanism when Cytosine undergoes deamination [1].
    RNA is a single strand which is transcribed from DNA [1]. Basically, the RNA strand has same structure of the DNA template except Thymine (T) base in DNA is replaced by Uracil base in RNA and RNA contain a hydroxyl (OH) in the sugar backbone. Having a hydroxyl in each sugar makes the RNA easier to be degraded after it has done its job. The mechanism is shown on the right.
    In general, understanding the DNA structure helps scientists to figure out the method to treat cancer. According to Benno Neto and Alexandre Lapis [7], a quercetin zinc (II) can be synthesized by quercetin-a compound is found in food and vegetable- and zinc (II). The quercetin zinc (II) would interact with DNA in tumor cells, and inhibit growth and proliferation of tumer cells. This complex makes tumor cells undergo apoptosis (program cell dead). The scheme 9 and scheme 10 in the journal shows how a quercetin zinc (II) is synthesized and interacts with DNA molecule.[7]
    Literature Cited:
    1. Bruice, P. Y. (2011). Organic Chemistry, Sixth Edition. Prentice Hall
    2. MSU Gallery of Chemists' Photo-Portraits and Mini-Biographies
    Women's Interchange at SLAC
    3. Watson, J. D., Crick, F.H.C. (1953). A structure of Deoxyribose Nucleic Acid. Nature 1953, 171:737-738
    4. Allen, F. W. (1954). Nucleic Acids, 23, 99-124. doi: 10.1146/
    5. Roth, C. M., Yarmush, M. L. (1999) Nucleic Acid Biotechnology, 1, 265-297 doi: 10.1146/annurev.bioeng.1.1.265
    6. Volker, J., Klump, H. H., Manning, G. S. (2001). Counterion Association with Native and Denatured Nucleic Acids: An Experimental Approach.doi:10.1006/jmbi.2001.4841
    7. Neto, B., Lapis A. (2009). Recent Developments in the Chemistry of Deoxyribonucleic Acid (DNA) Intercalators: Principles, Design, Synthesis, Applications and Trends. 14, 1725-1746doi: 10.3390/molecules14051725
    8. J. Tan et al./Bioorg. Med. Chem. 17 (2009) 614-620
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  5. page nonbenzodiazapines edited Nonbenzodiazepines Lindsey Berg | Chem 263 | Spring 2010 | Bellevue College Nonbenzodiazepines a…
    Lindsey Berg | Chem 263 | Spring 2010 | Bellevue College
    Nonbenzodiazepines are a class of drugs that is generally known to the public for its hypnotic properties and is often prescribed to treat insomnia.[1] They may have sedative or anti-anxiety properties as well, but the most popular compounds were not designed and are not prescribed for such.[2] A sedative is a substance that has the effect of calming and lowering excitement, agitation, or anxiety, a hypnotic is a substance that induces or maintains sleep, and insomnia is a chronic inability to fall asleep, stay asleep, or have restful sleep.[1]
    Included in the nonbenzodiazepines class are three commonly prescribed brand name drugs—Ambien® (zolpidem), Sonata® (zaleplon), and Lunesta® (eszopiclone)—often referred to as “z-drugs” because their generic names all start with the letter z and because they have similar therapeutic properties.[3] Zolpidem was first approved by the FDA in 1992 followed by zaleplon in 1999 and finally eszopiclone in 2004. All of these are officially described by the FDA as hypnotics to be prescribed for the treatment of insomnia.[2] This discussion will focus primarily on these three compounds.
    The name nonbenzodiazepine has reference to another class of drugs, benzodiazepines which functionally can be considered their precursors. They are similar to nonbenzodiazepines in how they function on a cellular level, but are unrelated in chemical structure. The nonbenzodiazepines were developed because they can offer more selective properties, hypnotic effects in the case of z-drugs, while reducing unwanted side effects including risk of addiction and unintentional overdose.[3][4][5] An understanding of how benzodiazepines work is required to understand how nonbenzodiazepines work and to understand why nonbenzodiazepines are superior as hypnotics.
    Benzodiazepines, which are also hypnotics and sedatives, have been on the market since the 1960’s.[3] They have a very specific chemical structure that includes a base consisting of a benzene ring and a diazepine ring joined together and only slight changes in substitutes on each unique compound. When ingested orally, the benzodiazepine travels to the central nervous system (CNS) where it has a repressing effect.[1][6]
    Our CNS is the control center of the human body and is made of a series of neuron cells that transmit and receive data (both chemically and electrically) throughout the body. On each neuron cell are channel receptors named GABAA which remain closed except when in the presence of GABA. GABA is an inhibitory neurotransmitter that can attach to GABAA channel receptors, and while attached will allow extracellular Cl- ions to flow into the neuron cell. The influx of Cl- ions inside the neuron is what actually slows down neurotransmission and results in CNS repression.[1,6]
    Benzodiazepines work in conjunction with GABA. If GABA is not present, the drug will have no sedating effect. Each GABAA receptor has an attachment site specific to GABA and another specific to benzodiazepines. When both GABA and a benzodiazepine are attached to the same GABAA channel receptor (not the same site), the flow of Cl- ions into the neuron cell through the channel will increase even further than when GABA alone is attached. Thus the partnership of GABA and benzodiazepines results in an even higher repression of the CNS. This is what causes someone to rapidly become drowsy and fall asleep after taking a benzodiazepine.[1][6]
    Nonbenzodiazepines are able to attach to the benzodiazepine sites on the GABAA receptors and cause the same effect of increasing the flow of Cl- ions, in conjunction with GABA, into the neuron cells. This is where the benefits (and motivation to create) nonbenzodiazepines lie. There are actually multiple sites on the GABAA receptors where the benzodiazepine can attach. The distinct sites have differing effects which ultimately may include sedation for one site, sleepiness for another site, or a number of other repressive type effects for other combinatory site docking, as the benzodiazepines can attach to all. In comparison, the z-drugs are designed to be more selective and can only bind to the sites that cause the hypnotic effect due their chemical shape.[3]
    Z-drugs are rapidly absorbed by the system and are at their max blood concentrations within an hour of consumption. The half life for the three compounds varies from one to six hours, and they have mostly pharmacologically inactive metabolites. This is part of what makes them well suited for treatment of insomnia. They are effective in the body for only the duration of one average night’s sleep and are not broken down into other active compounds. For these reasons, they have a reduced or no "hang-over" effect like those observed in older sedatives—benzodiazepines and barbiturates.[1][2]
    Z-drugs are now well known to be associated with complex behaviors that manifest in a very minority set of users. These behaviors were not observed in clinical trials, but rather through observations after they were approved and had been in the mass market for years. Reports of individuals being quite active during the night while having complete amnesia include activities such as cooking, eating, talking on phone, having sex, and even driving. Though they are rare events, the potential consequences can be severe and prompted a change in labeling by the FDA for all sleep disorder medications in 2006. The cause for the complex behaviors is not well known and reported incidents often cite the mixing of medications or alcohol.[3]
    Nelson, M. (2006). Sedative-hypnotic drugs. Retrieved from
    U.S. Food and Drug Administration. (2011). Drugs@FDA. Retrieved from
    Mitchell, H. A., & Weinshenker, D. (2010, March 15). Good night and good luck: Norepinephrine in sleep pharmacology. Biochem Pharmacol, 79(6), 801–809.
    Hoque, R., & Chesson, A.L. (2009, October 15). Zolpidem-induced sleepwalking, sleep related eating disorder, and sleep-driving: fluorine-18-flourodeoxyglucose positron emission tomography analysis, and a literature review of other unexpected clinical effects of zolpidem. Journal of Clinical Sleep Medicine, 5(5), 471-476.
    Zammit, G. (2009). Comparative Tolerability of Newer Agents for Insomnia. Drug Safety, 32(9), 735-748. Retrieved from EBSCOhost.
    Ashton, C. H. (2002). Benzodiazepines: how they work and how to withdraw. Retrieved from
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  6. page nucleic_acids edited ... Nucleic Acids fagime was here Nucleic acids are macromolecules linked by many nucleotides …
    Nucleic Acids fagime was here
    Nucleic acids are macromolecules linked by many nucleotides at phosphate groups. Each nucleotide is composed of a ring sugar (known as backbone) which binds to a phosphate group and a nitrogenous base. There are two types of nucleic acid: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is a blue print for organism’s life. It stores the genetic material which will be transmitted from parent to offspring. RNA is generated from DNA by transcription. The information in RNA is used to synthesis protein and amino acid which are essential for the function of cellular and organism [1].
    Nucleic acid was named because DNA was first found in the nuclei of white blood cells (an acidic environment) in 1869. Until 1951, Rosalind Franklin, who graduated from Cambridge University in London, worked in a lab at King’s College, and studied X-ray crystallography, figured out the structure of DNA through X-ray; Unfortunately, Franklin died in 1958 [2]. In 1953, James Watson and Francis Crick had visited Franklin’s lab and they had seen the X-ray of DNA that Franklin took. James Watson and Francis Crick had identified the three dimensional model of DNA, and they won the Nobel Prize in 1962.
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  7. page penicillin edited {penicillin_g_functional_groups.jpg} Functional groups present in penicillin, which only differ …

    {penicillin_g_functional_groups.jpg} Functional groups present in penicillin, which only differ in their "R" group or acyl side chain. Penicillin G (shown) possesses a phenyl.
    Penicillin is an antimicrobial drug that is isolated from the mold Penicillium chrysogenum (formerly known as Penicillium notatum).[[#_ftn1|[1]]] Penicillin was discovered in 1928 by Alexander Fleming, but was not until 15 years later that it was understood well enough to be able to isolate and treat bacterial infections.[[#_ftn2|[2]]] The discovery is serendipitous as a series of fortunate events lead to its detection. Alexander Fleming left for a two-week vacation leaving a cultured plate of Staphylococcus aureus on his workbench. The lab on the floor below was working with P. chrysogenum and the spores traveled to Fleming’s lab and onto the culture plate. Upon his return he observed that the growth of S. aureus was inhibited where the mold had grown. He inferred correctly that an aspect of the mold was able to inhibit the growth, but it wasn’t until Drs. Florey and Chain that Penicillin’s ultimate importance was realized to its full potential and it began to be used to treat disease.[[#_ftn3|[3]]]
    Florey and Chain found that they could isolate Penicillin in substantial quantities to treat infection and disease. Penicillin began to be used extensively during World War II as the “Wonderdrug”.[[#_ftn3|[3]]] For the first time, a wound or gash in the field was no longer a death sentence from infection. Today, there are five types of Penicillin used in medicine: Penicillin G, Aminopenicillins, Penicillinase-resistant penicillins, Anti-Pseudomonal penicillins and Cephalosporins.[[#_ftnref1|[4]]]
    Penicillinase-resistant penicillins are especially useful since they can be used with bacteria that posses an enzyme that inhibits the antimicrobial activity of penicillin. However, bacteria have recently begun to emerge with resistance to this group as well. One of the most notable of these is commonly referred to as Methicillin resistant Staphylococcus aureus, or MRSA.
    MRSA’s key to antibiotic resistance is its mecA gene, which is transmitted through the SCCmec cassette.[[#_ftn1|[5]]] MecA gives the microbe the ability to produce a β-lactamase enzyme that breaks down the β-lactam ring structure present in drugs such as penicillin. [[#_ftn2|[6]]] Penicillin functions in its ability to kill microbes by inhibiting cell wall synthesis, but the ability to produce Beta-lactamase via the mecA gene results in nonsuceptability to these drugs. [[#_ftn1|[5]]] Additionally, mecA codes for a protein on S. aureus’ surface (known as the penicillin-binding protein, or PBP 2a) that has “a decreased affinity to Beta-lactams”.[[#_ftn1|[5]]]
    Penicillin is a substituted β-lactam ring that is able to bind to and acylate a CH2OH group on an enzyme in bacteria (called transpeptidase) responsible for the cell wall synthesis[[#_ftn1|[7]]] and crosslinking of the cell wall layers in Gram-positive bacteria. Gram-positive bacteria posses an extremely high internal osmotic pressure and without an ability to build an effective cell wall, the bacteria succumb to osmotic lysis. The major component of the bacterial cell wall is peptidoglycan consisting of both polysaccharides and peptides that are cross-linked for stability.[2] Transpeptidase is the enzyme that catalyzes the linking of these into place and is what the β-lactam ring acts upon to hinder cell wall synthesis.
    {pcn-pbp.png} Complex formed between β-Lactam Ring and transpeptidase
    The β-lactam ring of all penicillins are strained and include an amide moiety, though each of the different penicillins differ in their R-group that is attached to the ring itself.[[#_ftn1|[2]]] Penicillin acts as a competitive inhibitor of the transpeptidase enzyme in the following way: Transpeptidase attacks the reactive carbonyl of the amide moiety and creates a covalent acyl-enzyme product.[[#_ftn1|[2]]] This hydrolyzes so slowly that the adduct formation is considered irreversible [2] and the transpeptidase becomes inactivated and unable to facilitate cell wall synthesis.
    As with MRSA, other strains of pathogenic bacteria are able to produce Penicillinase or β-lactamases that are able to evade penicillin. These β-lactamases cleave the ring, therefore inactivating it entirely. Another mechanism of resistance to penicillin is coding for a differently shaped penicillin binding protein (transpeptidase) entirely.[[#_ftn1|[8]]] Genes for β-lactamase production has spread rapidly (mecA in S. aureus for example) and the development of stronger and more innovative drugs continues to be a demanding force in biomedical research.
    {beta_lactam_cleave.png} β-Lactamase opening the 5-membered ring on penicillin
    [[#_ftn1|[1]]] Samson RA, Hadlok R, Stolk AC (1977). "A taxonomic study of the Penicillium chrysogenum series". Antonie van Leeuwenhoek 43 (2): 169–175.
    [[#_ftnref2|[2]]] Cox M., Nelson D. 2009. Lehinger Principles of Biochemistry. Fifth edition. New York: W.H. Freeman and Company.
    [[#_ftnref3|[3]]]The Role of Chemistry in History. [Internet]. Carlisile, (PA): Dickinson College.[updated 2008 March 28; cited 2011 May 10]. Available from:
    [[#_ftnref1|[4]]] Gladwin, M., Trattler, B. 2008. Clinical Microbiology Made Ridiculously Simple. Fourth edition. Miami: MedMaster, Inc.
    [[#_ftnref1|[5]]] Appelbaum, P.C. 2007. Microbiology of Antibiotic Resistance in Staphylococcus aureus. Clinical Infectious Diseases 45:S165-170.
    [[#_ftnref2|[6]]] Cowan, M. 2010. Microbiology: A Systems approach, 2nd edition. New York: McGraw-Hill.
    [[#_ftnref1|[8]]] Ding J., Su X., Guo F., Shi Y., Shao H. Meng X. Comparison of three different PCR-based methods to predict the penicillin nonsusceptible Streptococcus pneumoniae isolates from China. Letters in Applied Microbiology 2009; 48:105-111.

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  8. page nylon edited NYLON 6, 6 By Robert Elliott In 1928 Wallace Hume Crothers started working at Du Pont where he …

    NYLON 6, 6 By Robert Elliott
    In 1928 Wallace Hume Crothers started working at Du Pont where he ran a program investigating the composition of natural polymers with a focus on condensation polymers. In 1935 he discovered Nylon and in 1940 it was advertised in the New York World’s Fair. By the middle of May that year 4 million pairs of stockings had been sold in New York City but then the sales dropped during WWII because nylon was needed to make parachutes. Nylon was made into fibers and plastics. Examples are: fleece, satin clothing, rope, undergarments, socks, taffeta dresses, bicycle wheels, lawnmower blades, hairbrushes, and bearings. Around this time Nomex was invented which is a flame retardant fiber. Also Stephanie Kwolek invented Kevlar which is bullet proof. The patent for Kevlar was just the first of 17. Nylon was also the first engineering thermoplastic and it represented all sales in engineered thermoplastics until 1953. Also during the 1950’s George deMestral invented Velcro which he discovered while walking through the Swiss countryside. Velcro is a hook-and-eye combination where both components are made from nylon. During the 1990’s the Dutch State Mines created nylon 4, 6 “Stanyl” which is considered a green product because it is made from renewable resources and can be composted. Leading into the year 2000 1134 million kg of nylon 6, 6 was used in fiber applications.1
    The mechanism for nylon is a simple one. Starting with the products adipic acid and hexamethylene diamine the adipic acid will protonate itself and then the lone pair on a nitrogen of the hexamethylene diamine will bond to the carbon of the activated carbonyl. Next some electron flow results in the creation of a dimer between the adipic acid and the hexamethylene diamine and also the creation of water and more acid. This creation of water is why this reaction is called a condensation reaction. The removal of water will help shift this reaction to the right and produce more nylon 6,6. This principle is something we know as Le Chatlier. The resulting dimer mentioned before still has a reactive carboxylic acid and amine functional group so this is why this process can result in the long polymer chains that are observed. Towards the end of the reaction little acid is left to catalyze any carbonyls but the reaction will still continue and this is because the lone pair on a nitrogen of the hexamethylene diamine is reactive enough to attack the partial positive charge of the carbonyl regardless of activation.234
    In conclusion nylon is a synthesized product that even to this day we refashion into new uses. Whether that is in the medical profession or on the runway. Looking forward a new use of nylon has been found in cataract surgery. In cataract surgery the surgeon removes the opaque natural lens of the eye and the power of the eye is reduced 25%. This makes it impossible to form a focused image on the retina and to correct this they replace the natural lens of the eye with an intraocular implant. The intraocular lens is iris-supported and the lens is anchored with loops made of nylon.5 Another application for nylon has been found in sexual assault cases. Tests were performed with post-coital vaginal sampling using nylon or cotton flocked swabs. The problem with cotton swabs is a low yield of male cells. Results show that the nylon produces 6 fold more male cells in the sample. This means that the nylon will improve microscopic analysis and DNA typing in the medical forensic investigation of sexual assault cases.6 A third use for nylon is in healing burn victims. A nylon mesh is coated in silicon and then this is used as the dressing. This product Mepitel significantly reduces the amount of time needed to heal and the number of dressings that needed to be changed.7
    1Lagowski JJ. 2004. Chemistry foundations and applications: Macmillan Reference USA.
    2Considine GD. 2005. Van Nostrand’s encyclopedia of chemistry 5th edition: John Wiley & Sons, Inc.
    3Lagowski JJ. 1997. Macmillan encyclopedia of chemistry: Simon & Schuster Macmillan.
    4Montney CB, 2006. Chemical compounds volume 2: Thomson Gale.
    5Thoft RA. 1984. The role of lens implantation in cataract surgery. Annual Reviews Medicine: 35: 595-604.
    6Benschop CCG, Wiebosch DC, Kloosterman AD, Sijen T. 2010. Post-coital vaginal sampling with nylon flocked swabs improves DNA typing. Forensic Science International: Genetics 4: 115–121.
    7Bugmann P, Taylor S, Gyger D, Lironi A, Genin B, Vunda A, La Scala G, Birraux J, Le Coultre C. 1998. A silicone-coated nylon dressing reduces healing time in burned paediatric patients in comparison with standard sulfadiazine treatment: a prospective randomized trial. Burns. 24(7): 609-612.
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  10. page nicotine edited Nicotine: Any Way to Quit it ??? Nicotine (β-pyridyl-a-n-methyl-pymolidine),is an important molec…
    Nicotine: Any Way to Quit it ???
    Nicotine (β-pyridyl-a-n-methyl-pymolidine),is an important molecule in organic chemistry. It is consistent of ten carbon atoms, fourteen hydrogens, and two nitrogens, which make the nicotine molecule to be reactive because of the nitrogenous base end that burns at a low temperature (5).
    The history of nicotine is interesting. It was named after a plant called "Nicotiana tabacum", which in its turn, was named after the french ambassador Jen Nicot de Villemain, who sent the tobacco and the seeds from Brazil to Paris in 1560, then started to spread through Europe with promoting its medical use. It was isolated first in 1828 by Posselt and Reimann the German chemists, describing it as a poison, therefore they used it as an agricaultural pesticide(8). Nicotine is consumed by people in different ways, smoking tobacco is the most popular form of nicotine, besides the nicotine patches, gums, also liquids and sprays.
    Biologically, when nicotine enters the body, it automatically get transfered via the blood stream to the brain to get in control of the neurotransmitters in the brain, once the nicotine is consumed and reaches the brain, it promotes the production of dopamine, the neurotransmitter that carries messages between the nerve cells, to help the body recieving pleasure (in many cases, that will be when doing something necessary, like eating, or even in giving someone a hug), that means the dopamine is making the body to precieve that pleasue from smoking or getting nicotine. Another neurotransmitter, acetylcholine, which fills the receptors to produce the dopamine. When nicotine enters the brain it acts as the acetylcholine and triggers the production of dopamine. (FYI, Alcohol, Heroin, and Cocaine, work the same with dopamine) (1,5).
    Glutamate is another neurotransmitter in the brain that enhances the memory and learning, its production is triggered by nicotine, which means the brain would learn the pleasure that it recieves from the nicotine that is taken in, and it reminds the brain and body to get more nicotine. besides a lot of other neurotransmitters, nicotine increases the production of the natural body pain killer, endorphins, which when it is released, it gives the body a mental advantage like in runners' bodies, they experience "runner's high", from the release of endorphins that makes them not to worry about the smallaches and pains while they are running (7,8)
    Beside all the biological effects that nicotine causes, we have to mention that it also causes a fast metabolism rate, therefore a smoker would start losing the appetite and has the nicotine as a substitute for food, or it would be the opposite depending on the body nature and how it react to the strange substances that enters it. On the other hand, if a smoker would quit smoking, the appetite would come back and the body would need more food than before to substitute the nicotine loss, therefore the body would gain extra weight than before (7).
    We see that the nicotine is an interesting molecule to study and researches are still working on developing newer versions of different medicines tofind a substitute for nicotine in between the signaling and recieving cells in the nerve cells, also to find a blocker for the receptor gaps so the nicotine would not be blocking those spots.
    (1)Benowitz, N, L., Dains, K, M., Dempsey, D., Herrera, B., Yu, L., Jacob P. (2009). Urine nicotine metabolite concentrations in relation to plasma cotinine during low-level nicotine exposure. Nicotine & tobacco research, Vol 11, 954-960.
    (2)Cartoon Stock. (06/09/2011). Nicotine cartoons and comics.
    (3)Charlton, A,. (June, 2004). Medical uses of tobacco in history. The royal society of medicine
    (4)ChemBlink (06/09/2011)
    (5)Farrington, K. (2002). This is nicotine. London, United Kingdom: Sanctuary Publishing Limited, Sanctuary House.
    (6)Gangster Legs.
    (7)Henningfield, J. E., Zeller. M., (December, 2005). Nicotine psychopharmacology research contributions to United States and global tobacco regulation: a look back and a look forward.
    (8)Rackley, J. (2002). Nicotine. San Diego, California: Lucent Books.
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