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Bacteriophage Qβ
Bacteriophage Qbeta (''Qubevirus durum''), commonly referred to as Qbeta or Qβ, is a positive-strand RNA virus which infects bacteria that have F-pili, most commonly ''Escherichia coli''. Its linear genome is packaged into an icosahedral capsid with a diameter of 28 nm. Bacteriophage Qβ enters its host cell after binding to the side of the F-pilus. Genetics The genome of Qβ is approximately 4,217 nucleotides, depending on the source which sequenced the virus. Qβ has been isolated all over the world, multiple times, with various subspecies that code for nearly identical proteins but can have very different nucleotide sequences. The genome has three open reading frames that encode four proteins: the maturation/lysis protein A2; the coat protein; a readthrough of a leaky stop codon in the coat protein, called A1; and the β-subunit of an RNA-dependent RNA-polymerase (RdRp) termed the replicase. The genome is highly structured, regulating gene expression and protecting ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission Electron Micrograph
Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid. An image is formed from the interaction of the electrons with the sample as the beam is transmitted through the specimen. The image is then magnified and focused onto an imaging device, such as a fluorescent screen, a layer of photographic film, or a sensor such as a scintillator attached to a charge-coupled device. Transmission electron microscopes are capable of imaging at a significantly higher resolution than light microscopes, owing to the smaller de Broglie wavelength of electrons. This enables the instrument to capture fine detail—even as small as a single column of atoms, which is thousands of times smaller than a resolvable object seen in a light microscope. Transmission electron microscopy is a major analytical method i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA-dependent RNA Polymerase
RNA-dependent RNA polymerase (RdRp) or RNA replicase is an enzyme that catalyzes the replication of RNA from an RNA template. Specifically, it catalyzes synthesis of the RNA strand complementary to a given RNA template. This is in contrast to typical DNA-dependent RNA polymerases, which all organisms use to catalyze the transcription of RNA from a DNA template. RdRp is an essential protein encoded in the genomes of most RNA-containing viruses with no DNA stage including SARS-CoV-2. Some eukaryotes also contain RdRps, which are involved in RNA interference and differ structurally from viral RdRps. History Viral RdRps were discovered in the early 1960s from studies on mengovirus and polio virus when it was observed that these viruses were not sensitive to actinomycin D, a drug that inhibits cellular DNA-directed RNA synthesis. This lack of sensitivity suggested that there is a virus-specific enzyme that could copy RNA from an RNA template and not from a DNA template. Distr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Ancestor's Tale
''The Ancestor's Tale: A Pilgrimage to the Dawn of Life'' is a science book by Richard Dawkins and Yan Wong on the subject of evolution, which follows the path of humans backwards through evolutionary history, describing some of humanity's cousins as they converge on their common ancestors. The book was first published in 2004 and substantially updated in 2016. It was nominated for the 2005 Aventis Prize for Science Books. Synopsis The book takes a different path backwards through evolution and meets different groupings of organisms. The authors use backward chronology instead of a forward chronology as a way of celebrating the unity of life. In a backward chronology, the ancestors of any set of species must eventually meet at a particular moment. The last common ancestor is the one that they all share which the authors call a "concestor". The oldest concestor is the ancestor of all surviving life forms on this planet. The evidence for this is that all organisms share the sa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sol Spiegelman
Sol Spiegelman (December 14, 1914 – January 21, 1983) was an American molecular biologist. He developed the technique of nucleic acid hybridization, which helped to lay the groundwork for advances in recombinant DNA technology. Early life and education Spiegelman was born in Brooklyn, New York City in 1914. He attended the City College of New York and was initially interested in biology, but found the courses uninspiring and instead chose to focus on math and physics. During his undergraduate work he took a leave of absence to work in a biology laboratory, where he studied the genetics of bacteria. He graduated in 1939 with a bachelor's degree in mathematics. He then began his graduate studies at Columbia University in 1940, studying cellular physiology under the supervision of H.B. Steinbach. Spiegelman joined Steinbach in his move to Washington University two years later, and received his PhD from that institution in 1944. His graduate work focused on what was then known as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peptidoglycan
Peptidoglycan or murein is a unique large macromolecule, a polysaccharide, consisting of sugars and amino acids that forms a mesh-like peptidoglycan layer outside the plasma membrane, the rigid cell wall (murein sacculus) characteristic of most bacteria (domain ''Bacteria''). The sugar component consists of alternating residues of β-(1,4) linked ''N''-acetylglucosamine (NAG) and ''N''-acetylmuramic acid (NAM). Attached to the ''N''-acetylmuramic acid is a oligopeptide chain made of three to five amino acids. The peptide chain can be cross-linked to the peptide chain of another strand forming the 3D mesh-like layer. Peptidoglycan serves a structural role in the bacterial cell wall, giving structural strength, as well as counteracting the osmotic pressure of the cytoplasm. This repetitive linking results in a dense peptidoglycan layer which is critical for maintaining cell form and withstanding high osmotic pressures, and it is regularly replaced by peptidoglycan production. Pep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Penicillin
Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using deep tank fermentation and then purified. A number of natural penicillins have been discovered, but only two purified compounds are in clinical use: penicillin G (intramuscular or intravenous use) and penicillin V (given by mouth). Penicillins were among the first medications to be effective against many bacterial infections caused by staphylococci and streptococci. They are still widely used today for different bacterial infections, though many types of bacteria have developed resistance following extensive use. 10% of the population claims penicillin allergies but because the frequency of positive skin test results decreases by 10% with each year of avoidance, 90% of these patients can tolerate penicillin. Additionally, those with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacteriophage MS2
Bacteriophage MS2 (''Emesvirus zinderi''), commonly called MS2, is an icosahedral, positive-sense single-stranded RNA virus that infects the bacterium ''Escherichia coli'' and other members of the Enterobacteriaceae. MS2 is a member of a family of closely related bacterial viruses that includes bacteriophage f2, bacteriophage Qβ, R17, and GA. History In 1961, MS2 was isolated by Alvin John Clark and recognized as an RNA-containing phage very similar to bacteriophage f2. In 1976, the MS2 genome was the first genome to be completely sequenced. This was accomplished by Walter Fiers and his team, building upon their earlier milestone in 1972 of the first gene to be completely sequenced, the MS2 coat protein. These sequences were determined at the RNA level, whereas the next landmark achievement, the sequence of the bacteriophage ΦX174 genome in 1977, was determined using DNA. The first effort at a statistical analysis of the MS2 genome was a search for patterns in the nucleoti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amber Mutation
In molecular biology (specifically protein biosynthesis), a stop codon (or termination codon) is a codon (nucleotide triplet within messenger RNA) that signals the termination of the translation process of the current protein. Most codons in messenger RNA correspond to the addition of an amino acid to a growing polypeptide chain, which may ultimately become a protein; stop codons signal the termination of this process by binding release factors, which cause the ribosomal subunits to disassociate, releasing the amino acid chain. While start codons need nearby sequences or initiation factors to start translation, a stop codon alone is sufficient to initiate termination. Properties Standard codons In the standard genetic code, there are three different termination codons: Alternative stop codons There are variations on the standard genetic code, and alternative stop codons have been found in the mitochondrial genomes of vertebrates, ''Scenedesmus obliquus'', and '' Thraust ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1-s2
1S or 1s may refer to: * 1s electron, in an atomic orbital * Sabre (computer system)'s IATA code * 1S, a series of Toyota S engines * SSH 1S (WA); see Washington State Route 502, Washington State Route 503 See also *Shilling *Second * Ones (other) Ones may refer to: * ''Ones'' (album), by Selena, 2002 * The Ones, New York electronica group * "The Ones" (''30 Rock''), an episode of ''30 Rock'' * In music, single bars of alternating solos (as in "trading ones"); see Rhythm section#Musical r ... * S1 (other) {{Letter-NumberCombDisambig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chaperone (protein)
In molecular biology, molecular chaperones are proteins that assist the conformational folding or unfolding of large proteins or macromolecular protein complexes. There are a number of classes of molecular chaperones, all of which function to assist large proteins in proper protein folding during or after synthesis, and after partial denaturation. Chaperones are also involved in the translocation of proteins for proteolysis. The first molecular chaperones discovered were a type of assembly chaperones which assist in the assembly of nucleosomes from folded histones and DNA. One major function of molecular chaperones is to prevent the aggregation of misfolded proteins, thus many chaperone proteins are classified as heat shock proteins, as the tendency for protein aggregation is increased by heat stress. The majority of molecular chaperones do not convey any steric information for protein folding, and instead assist in protein folding by binding to and stabilizing folding interme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA Replicase
RNA-dependent RNA polymerase (RdRp) or RNA replicase is an enzyme that catalyzes the replication of RNA from an RNA template. Specifically, it catalyzes synthesis of the RNA strand complementary to a given RNA template. This is in contrast to typical DNA-dependent RNA polymerases, which all organisms use to catalyze the transcription of RNA from a DNA template. RdRp is an essential protein encoded in the genomes of most RNA-containing viruses with no DNA stage including SARS-CoV-2. Some eukaryotes also contain RdRps, which are involved in RNA interference and differ structurally from viral RdRps. History Viral RdRps were discovered in the early 1960s from studies on mengovirus and polio virus when it was observed that these viruses were not sensitive to actinomycin D, a drug that inhibits cellular DNA-directed RNA synthesis. This lack of sensitivity suggested that there is a virus-specific enzyme that could copy RNA from an RNA template and not from a DNA template. Distr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EF-Ts
EF-Ts (elongation factor thermo stable) is one of the prokaryotic elongation factors. It is found in human mitochrondria as TSFM. It is similar to eukaryotic EF-1B. EF-Ts serves as the guanine nucleotide exchange factor for EF-Tu (elongation factor thermo unstable), catalyzing the release of guanosine diphosphate from EF-Tu. This enables EF-Tu to bind to a new guanosine triphosphate molecule, release EF-Ts, and go on to catalyze another aminoacyl tRNA addition. Structure The protein Qβ-Replicase is a tetrameric protein, meaning it contains four subunits. These subunits are the two elongation factors, EF-Tu & EF-Ts, the ribosomal protein subunit S1, and the RNA dependent RNA polymerase β-subunit. The two elongation factors form a heterodimer structure known as The Elongation factor complex, which is necessary for the polymerization activity of the RDRP β-Subunit. Its secondary structural components consists of α-helices, β-sheets and β-barrels. EF-Ts comprises the maj ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
