Molecules/Elements/Particles

 

Monday
Feb252013

Estradiol

"Estradiol (E2 or 17β-estradiol, also oestradiol) is a sex hormone. Estradiol is abbreviated E2 as it has two hydroxyl groups in its molecular structure. Estrone has one (E1) and estriol has three (E3). Estradiol is about 10 times as potent as estrone and about 80 times as potent as estriol in its estrogenic effect. Except during the early follicular phase of the menstrual cycle, its serum levels are somewhat higher than that of estrone during the reproductive years of the human female. Thus it is the predominant estrogen during reproductive years both in terms of absolute serum levels as well as in terms of estrogenic activity. During menopause, estrone is the predominant circulating estrogen and during pregnancy estriol is the predominant circulating estrogen in terms of serum levels. Estradiol is also present in males, being produced as an active metabolic product of testosterone. The serum levels of estradiol in males (14 - 55 pg/mL) are roughly comparable to those of postmenopausal women (< 35 pg/mL). Estradiol in vivo is interconvertible with estrone; estradiol to estrone conversion being favored. Estradiol has not only a critical impact on reproductive and sexual functioning, but also affects other organs, including the bones."

Wednesday
Feb202013

Amphotericin B

"Amphotericin B (Fungilin, Fungizone, Abelcet, AmBisome, Fungisome, Amphocil, Amphotec) is a polyene antifungal drug, often used intravenously for systemic fungal infections. It was originally extracted from Streptomyces nodosus, a filamentous bacterium, in 1955 at the Squibb Institute for Medical Research from cultures of an undescribed streptomycete isolated from the soil collected in the Orinoco River region of Venezuela. Its name originates from the chemical's amphoteric properties. Two amphotericins, amphotericin A and amphotericin B are known, but only B is used clinically, because it is significantly more active in vivo. Amphotericin A is almost identical to amphotericin B (having a double C=C bond between the 27th and 28th carbons), but has little antifungal activity. Currently, the drug is available as plain amphotericin B, as a cholesteryl sulfate complex (ABCD), as a lipid complex (ABLC), and as a liposomal formulation (LAmB). The latter formulations have been developed to improve tolerability for the patient, but may show considerably different pharmacokinetic characteristics compared to plain amphotericin B."

"As with other polyene antifungals, amphotericin B binds with ergosterol, a component of fungal cell membranes, forming a transmembrane channel that leads to monovalent ion (K+Na+H+ and Cl) leakage, which is the primary effect leading to fungal cell death. Recently, however, researchers found evidence that pore formation is not necessarily linked to cell death[4][5] The actual mechanism of action may be more complex and multifaceted."

Sunday
Feb102013

Palmitoleic Acid

"Palmitoleic acid, or (Z)-9-hexadecenoic acid, is an omega-7 monounsaturated fatty acid with the formula CH3(CH2)5CH=CH(CH2)7COOH that is a common constituent of the glycerides of human adipose tissue. It is present in all tissues, but generally found in higher concentrations in the liver. It is biosynthesized from palmitic acid by the action of the enzyme delta-9 desaturase. A beneficial fatty acid, it has been shown to increase insulin sensitivity by suppressing inflammation, as well as inhibit the destruction of insulin-secreting pancreatic beta cells."

"Palmitoleic acid can be abbreviated as 16:1∆9. Dietary sources of palmitoleic acid include a variety of animal oils, vegetable oils, and marine oils. Macadamia oil (Macadamia integrifolia) and sea buckthorn oil (Hippophae rhamnoides) are botanical sources with high concentrations, containing 17%[2] and 40%[3] of palmitoleic acid, respectively."

"In an analysis of numerous fatty acids, palmitoleate was shown to possibly influence fatty liver deposition/production, insulin action, palmitate, and fatty acid synthase, leading to proposal of a new term, "lipokine" having hormone-like effects."

Monday
Feb042013

Small Nuclear RNA 

"Small nuclear ribonucleic acid (snRNA), also commonly referred to as U-RNA, is a class of small RNA molecules that are found within the nucleus of eukaryotic cells. The length of the an average snRNA is approximately 150 nucleotides. They are transcribed by either RNA polymerase II or RNA polymerase III, and studies have shown that their primary function is in the processing of pre-mRNA (hnRNA) in the nucleus. They have also been shown to aide in the regulation of transcription factors (7SK RNA) or RNA polymerase II (B2 RNA), and maintaining the telomeres."

"snRNA are always associated with a set of specific proteins, and the complexes are referred to as small nuclear ribonucleoproteins (snRNP) often pronounced "snurps". Each snRNP particle is composed of several Sm proteins, the snRNA component, and snRNP specific proteins. The most common snRNA components of these complexes are known, respectively, as: U1 snRNAU2 snRNAU4 snRNAU5 snRNA, and U6 snRNA. Their nomenclature derives from their high uridine content."

"snRNAs were discovered by accident during a gel electrophoresis experiment in 1966. An unexpected type of RNA was found in the gel and investigated. Later analysis has shown that these RNA were high in uridylate and were established in the nucleus."

 

 

Sunday
Feb032013

Dendralenes

"A dendralene is a discrete acyclic cross-conjugated polyene.[1][2] The simplest dendralene is buta-1,3-diene (1) or [2]dendralene followed by [3]dendralene (2), [4]dendralene (3) and [5]dendralene (4) and so forth. [2]dendralene (butadiene) is the only one not cross-conjugated."

"The name dendralene is pulled together from the words dendrimerlinear and alkene. The higher dendralenes are of scientific interest because they open up a large array of neworganic compounds from a relatively simple precursor especially by Diels-Alder chemistry. Their cyclic counterparts are aptly called radialenes."

"Even-membered dendralenes (e.g. [6]dendralene, [8]dendralene) tend to behave as chains of decoupled and isolated diene units. The ultraviolet absorption maxima equal that of butadiene itself. The dendralenes with an odd number of alkene units are more reactive due to the presence of favorable s-cis diene conformations and Diels-Alder reactions take place more easily with a preference for the termini."


Wednesday
Jan302013

Cyclohexanone

Cyclohexanone is the organic compound with the formula (CH2)5CO. The molecule consists of six-carbon cyclic molecule with a ketonefunctional group. This colorless oil has an odor reminiscent of peardrop sweets as well as acetone. Over time, samples assume a yellow color due to oxidation. Cyclohexanone is slightly soluble in water, but miscible with common organic solvents. Billions of kilograms are produced annually, mainly as a precursor to nylon.

Cyclohexanone is produced by the oxidation of cyclohexane in air, typically using cobalt catalysts:[4]

C6H12 + O2 → (CH2)5CO + H2O

This process co-forms cyclohexanol, and this mixture, called "KA oil" for ketone-alcohol oil, is the main feedstock for the production ofadipic acid. The oxidation involves radicals and the intermediacy of the hydroperoxide C6H11O2H. In some cases, purified cyclohexanol, obtained by hydration of cyclohexene, is the precursor. Alternatively, cyclohexanone can be produced by the partial hydrogenation ofphenol:

C6H5OH + 2 H2 → (CH2)5CO

This process can also be adjusted to favor the formation of cyclohexanol.


Sunday
Jan272013

Citric Acid

"Citric acid is a weak organic acid. It is a natural preservative/conservative and is also used to add an acidic, or sour, taste to foods and soft drinks. In biochemistry, the conjugate base of citric acid, citrate, is important as an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms."

"Citric acid is a commodity chemical, and more than a million tonnes are produced every year by fermentation. It is used mainly as an acidifier, as a flavoring, and as a chelating agent."

"At room temperature, citric acid is a white crystalline powder. It can exist either in an anhydrous (water-free) form or as a monohydrate. The anhydrous form crystallizes from hot water, while the monohydrate forms when citric acid is crystallized from cold water. The monohydrate can be converted to the anhydrous form by heating above 78 °C. Citric acid also dissolves in absolute (anhydrous) ethanol (76 parts of citric acid per 100 parts of ethanol) at 15 °C."

Wednesday
Jan232013

Tyrosine

"Tyrosine (abbreviated as Tyr or Y)[1] or 4-hydroxyphenylalanine, is one of the 22 amino acids that are used by cells to synthesize proteins. Its codons are UAC and UAU. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the Greek tyri, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese.[2][3] It is called tyrosyl when referred to as a functional group or side chain."

"Aside from being a proteinogenic amino acid, tyrosine has a special role by virtue of the phenol functionality. It occurs in proteins that are part of signal transduction processes. It functions as a receiver of phosphate groups that are transferred by way of protein kinases (so-called receptor tyrosine kinases). Phosphorylation of the hydroxyl group changes the activity of the target protein."

"A tyrosine residue also plays an important role in photosynthesis. In chloroplasts (photosystem II), it acts as an electron donor in the reduction of oxidized chlorophyll. In this process, it undergoes deprotonation of its phenolic OH-group. This radical is subsequently reduced in the photosystem II by the four core manganese clusters."

Saturday
Jan192013

Dibenzofuran

"Dibenzofuran, is a heterocyclic organic compound with the chemical  structure shown at right. It is an aromatic compound that has two benzene rings fused to one furan ring in the middle. All of the numbered carbon atoms have a hydrogen atom bonded to each of them (not shown in the image). Dibenzofuran is an aromatic ether having the chemical formula C12H8O."

"Dibenzofurans can also inaccurately refer to polychlorinated dibenzofurans (PCDFs), a family of organic compounds with one or several of the hydrogens in the dibenzofuran structure replaced by chlorines. For example, 2,3,7,8-tetrachlorodibenzofuran (TCDF) has chlorine atoms substituted for each of the hydrogens on the number 2, 3, 7, and 8 carbons (see structure below). Polychlorinated dibenzofurans are much more toxic chemicals than the parent compounds with properties and chemical structures similar to polychlorinated dibenzodioxins. These groups together are often inaccurately called dioxins."


Tuesday
Jan152013

Pyrimidine

"Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring.[2] It is isomericwith two other forms of diazinePyridazine, with the nitrogen atoms in positions 1 and 2; and Pyrazine, with the nitrogen atoms in positions 1 and 4."

"A pyrimidine has many properties in common with pyridine, as the number of nitrogen atoms in the ring increases the ring pi electrons become less energetic and electrophilic aromatic substitution gets more difficult while nucleophilic aromatic substitution gets easier. An example of the last reaction type is the displacement of the amino group in 2-aminopyrimidine by chlorine[3] and its reverse.[4] Reduction in resonance stabilization of pyrimidines may lead to addition and ring cleavage reactions rather than substitutions. One such manifestation is observed in the Dimroth rearrangement."

"Compared to pyridine, N-alkylation and N-oxidation is more difficult, and pyrimidines are also less basic: The pKa value for protonated pyrimidine is 1.23 compared to 5.30 for pyridine."