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Gramicidin
Gramicidin, also called gramicidin D, is a mix of ionophoric antibiotics, gramicidin A, B and C, which make up about 80%, 5%, and 15% of the mix, respectively. Each has 2 isoforms, so the mix has 6 different types of gramicidin molecules. They can be extracted from ''Brevibacillus brevis'' soil bacteria. Gramicidins are linear peptides with 15 amino acids. This is in contrast to unrelated gramicidin S, which is a cyclic peptide. Medical uses Gramicidins work as antibiotics against gram-positive bacteria like ''Bacillus subtilis'' and ''Staphylococcus aureus'', but not well against gram-negative ones like ''E. coli''. Gramicidins are used in medicinal lozenges for sore throat and in topical medicines to treat infected wounds. Gramicidins are often mixed with other antibiotics like tyrocidine and antiseptics. Gramicidins are also used in eye drops for bacterial eye infections. In drops, they are often mixed with other antibiotics like polymyxin B or neomycin. Multiple antibio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Gramicidin S
Gramicidin S or Gramicidin Soviet is an antibiotic that is effective against some gram-positive and gram-negative bacteria as well as some fungi. It is a derivative of gramicidin, produced by the gram-positive bacterium ''Brevibacillus brevis''. Gramicidin S is a cyclodecapeptide, constructed as two identical pentapeptides joined head to tail, formally written as ''cyclo''(- Val- Orn- Leu-D- Phe- Pro-)2. That is to say, it forms a ring structure composed of five different amino acids, each one used twice within the structure. Another interesting point is that it utilizes two amino acids uncommon in peptides: ornithine as well as the atypical stereoisomer of phenylalanine. It is synthesized by gramicidin S synthetase. Biosynthesis Gramicidin S biosynthetic pathway consists of two-enzyme of nonribosomal peptide synthases ( NRPSs), gramicidin S synthetase I (GrsA) and gramicidin S synthetase II (GrsB), to give a product as a cyclic decapeptide. Within the biosynthetic pat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Gramicidin Helices
Gramicidin, also called gramicidin D, is a mix of ionophore, ionophoric antibiotics, gramicidin A, B and C, which make up about 80%, 5%, and 15% of the mix, respectively. Each has 2 isoforms, so the mix has 6 different types of gramicidin molecules. They can be extracted from ''Brevibacillus brevis'' soil bacteria. Gramicidins are linear peptides with 15 amino acids. This is in contrast to unrelated gramicidin S, which is a cyclic peptide. Medical uses Gramicidins work as antibiotics against gram-positive bacteria like ''Bacillus subtilis'' and ''Staphylococcus aureus'', but not well against gram-negative ones like ''E. coli''. Gramicidins are used in medicinal Throat lozenge, lozenges for sore throat and in topical medicines to treat infected wounds. Gramicidins are often mixed with other antibiotics like tyrocidine and antiseptics. Gramicidins are also used in eye drops for bacterial eye infections. In drops, they are often mixed with other antibiotics like polymyxin B or neo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Ionophore
In chemistry, an ionophore () is a chemical species that reversibly binds ions. Many ionophores are lipid-soluble entities that transport ions across the cell membrane. Ionophores catalyze ion transport across hydrophobic membranes, such as liquid polymeric membranes (carrier-based ion selective electrodes) or lipid bilayers found in the living cells or synthetic vesicles ( liposomes). Structurally, an ionophore contains a hydrophilic center and a hydrophobic portion that interacts with the membrane. Some ionophores are synthesized by microorganisms to import ions into their cells. Synthetic ion carriers have also been prepared. Ionophores selective for cations and anions have found many applications in analysis. These compounds have also shown to have various biological effects and a synergistic effect when combined with the ion they bind. Classification Biological activities of metal ion-binding compounds can be changed in response to the increment of the metal concentr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
René Dubos
René Jules Dubos (February 20, 1901 – February 20, 1982) was a French-American microbiologist, experimental pathologist, environmentalist, humanist, and winner of the Pulitzer Prize for General Nonfiction for his book '' So Human An Animal''. He is credited for having made famous the environmental maxim: "Think globally, act locally." Aside from a period from 1942 to 1944 when he was George Fabyan Professor of Comparative Pathology and professor of tropical medicine at Harvard Medical School and Harvard School of Public Health, his scientific career was spent entirely at The Rockefeller Institute for Medical Research, later renamed The Rockefeller University. Early life and education Dubos was born in Saint-Brice-sous-Forêt, France, on February 20, 1901, and grew up in Hénonville, another small Île-de-France farming village north of Paris. His parents operated butcher shops in each of these villages. He attended high school and the National Institute of Agronomy in Pari ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Nonribosomal Peptide
Nonribosomal peptides (NRP) are a class of peptide secondary metabolites, usually produced by microorganisms like bacterium, bacteria and fungi. Nonribosomal peptides are also found in higher organisms, such as nudibranchs, but are thought to be made by bacteria commensalism, inside these organisms. While there exist a wide range of peptides that are not synthesized by ribosomes, the term ''nonribosomal peptide'' typically refers to a very specific set of these as discussed in this article. Nonribosomal peptides are synthesized by nonribosomal peptide synthetases, which, unlike the ribosomes, are independent of messenger RNA. Each nonribosomal peptide synthetase can synthesize only one type of peptide. Nonribosomal peptides often have cyclic compound, cyclic and/or branched structures, can contain non-proteinogenic amino acids including D-amino acids, carry modifications like ''Nitrogen, N''-methyl and ''N''-formyl groups, or are Glycosylation, glycosylated, Acylation, acylated, Ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Antibiotics
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy, treatment and antibiotic prophylaxis, prevention of such infections. They may either bactericide, kill or bacteriostatic agent, inhibit the growth of bacteria. A limited number of antibiotics also possess antiprotozoal activity. Antibiotics are not effective against viruses such as the ones which cause the common cold or influenza. Drugs which inhibit growth of viruses are termed antiviral drugs or antivirals. Antibiotics are also not effective against fungi. Drugs which inhibit growth of fungi are called antifungal drugs. Sometimes, the term ''antibiotic''—literally "opposing life", from the Greek language, Greek roots ἀντι ''anti'', "against" and βίος ''bios'', "life"—is broadly used to refer to any substance used against ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Lipid Bilayer
The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes form a continuous barrier around all cell (biology), cells. The cell membranes of almost all organisms and many viruses are made of a lipid bilayer, as are the nuclear envelope, nuclear membrane surrounding the cell nucleus, and biological membrane, membranes of the membrane-bound organelles in the cell. The lipid bilayer is the barrier that keeps ions, proteins and other molecules where they are needed and prevents them from diffusing into areas where they should not be. Lipid bilayers are ideally suited to this role, even though they are only a few nanometers in width, because they are impermeable to most water-soluble (hydrophilic) molecules. Bilayers are particularly impermeable to ions, which allows cells to regulate salt concentrations and pH by transporting ions across their membranes using proteins called Ion transporter, ion pumps. Biological bilaye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Isoleucine
Isoleucine (symbol Ile or I) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a hydrocarbon side chain with a branch (a central carbon atom bound to three other carbon atoms). It is classified as a non-polar, uncharged (at physiological pH), branched-chain, aliphatic amino acid. It is essential in humans, meaning the body cannot synthesize it. Essential amino acids are necessary in the human diet. In plants isoleucine can be synthesized from threonine and methionine. In plants and bacteria, isoleucine is synthesized from a pyruvate employing leucine biosynthesis enzymes. It is encoded by the codons AUU, AUC, and AUA. Metabolism Biosynthesis In plants and microorganisms, isoleucine is synthesized from pyruvate and alpha-ketobutyrate. This pathway ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Valine
Valine (symbol Val or V) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated −NH3+ form under biological conditions), an α- carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a side chain isopropyl group, making it a non-polar aliphatic amino acid. Valine is essential in humans, meaning the body cannot synthesize it; it must be obtained from dietary sources which are foods that contain proteins, such as meats, dairy products, soy products, beans and legumes. It is encoded by all codons starting with GU (GUU, GUC, GUA, and GUG). History and etymology Valine was first isolated from casein in 1901 by Hermann Emil Fischer. The name valine comes from its structural similarity to valeric acid, which in turn is named after the plant valerian due to the presence of the acid in the roots of the plant. Nomenclature According to IUPAC, carbon atoms forming v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Isoform
A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene and are the result of genetic differences. While many perform the same or similar biological roles, some isoforms have unique functions. A set of protein isoforms may be formed from alternative splicings, variable promoter usage, or other post-transcriptional modifications of a single gene; post-translational modifications are generally not considered. (For that, see Proteoforms.) Through RNA splicing mechanisms, mRNA has the ability to select different protein-coding segments ( exons) of a gene, or even different parts of exons from RNA to form different mRNA sequences. Each unique sequence produces a specific form of a protein. The discovery of isoforms could explain the discrepancy between the small number of protein coding regions of genes revealed by the human genome project and the large diversity of proteins seen in an organism: different proteins e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Tyrosine
-Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a conditionally essential amino acid with a polar side group. The word "tyrosine" is from the Greek ''tyrós'', meaning ''cheese'', as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. It is called tyrosyl when referred to as a functional group or side chain. While tyrosine is generally classified as a hydrophobic amino acid, it is more hydrophilic than phenylalanine. It is encoded by the codons UAC and UAU in messenger RNA. The one-letter symbol Y was assigned to tyrosine for being alphabetically nearest of those letters available. Note that T was assigned to the structurally simpler threonine, U was avoided for its similarity with V for valine, W was assigned to tryptophan, while X was reserved for undetermined or atypical amino acids. The mnemonic t''Y''rosine was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Phenylalanine
Phenylalanine (symbol Phe or F) is an essential α-amino acid with the chemical formula, formula . It can be viewed as a benzyl group substituent, substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino acid is classified as neutral, and chemical polarity, nonpolar because of the inert and hydrophobic nature of the benzyl side chain. The chirality (chemistry)#Naming conventions, L-isomer is used to biochemically form proteins coded for by DNA. Phenylalanine is a precursor for tyrosine, the monoamine neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), and the biological pigment melanin. It is Genetic code, encoded by the messenger RNA codons UUU and UUC. Phenylalanine is found naturally in the milk of mammals. It is used in the manufacture of food and drink products and sold as a nutritional supplement as it is a direct precursor to the neuromodulation, neuromodulator phe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
