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Enediyne
Enediynes are organic compounds containing two triple bonds and one double bond. Enediynes are most notable for their limited use as antitumor antibiotics (known as enediyne anticancer antibiotics). They are efficient at inducing apoptosis in cells, but cannot differentiate cancerous cells from healthy cells. Consequently, research is being conducted to increase the specificity of enediyne toxicity. Structure and reactivity A nine- or ten-membered ring containing a double bond between two triple bonds is termed the warhead of the enediyne. In this state, the warhead is inactive. Enediynes are triggered into a chemically active state via Bergman or Myers-Saito cyclization. The triggering mechanism can be attributed to an intramolecular nucleophilic attack initiated by one of the variable regions of the molecule. Triggering can also occur via attack by an external nucleophile. Bergman cyclization restructures the enediyne ring into two smaller rings. One electron from each of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enediyne DNA Damage
Enediynes are organic compounds containing two triple bonds and one double bond. Enediynes are most notable for their limited use as antitumor antibiotics (known as enediyne Chemotherapy, anticancer antibiotics). They are efficient at inducing apoptosis in Cell biology, cells, but cannot differentiate Cancer cell, cancerous cells from healthy cells. Consequently, research is being conducted to increase the specificity of enediyne toxicity. Structure and reactivity A nine- or ten-membered ring containing a double bond between two triple bonds is termed the warhead of the enediyne. In this state, the warhead is inactive. Enediynes are triggered into a chemically active state via Bergman cyclization, Bergman or Myers-Saito cyclization. The triggering mechanism can be attributed to an intramolecular nucleophilic attack initiated by one of the variable regions of the molecule. Triggering can also occur via attack by an external nucleophile. Bergman cyclization restructures the ened ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C-1027
C-1027 or lidamycin is an antitumor antibiotic consisting of a complex of an enediyne chromophore and an apoenzyme, apoprotein. It shows antibiotic activity against most Gram-positive bacteria. It is one of the most potent cytotoxic molecules known, due to its induction of a higher ratio of DNA double-strand breaks than single-strand breaks. C-1027's chromophore contains a nine-membered enediyne that is responsible for most of the molecule's biological activity. Unlike other enediynes, this molecule contains no triggering mechanism. It is already primed to undergo the cycloaromatization reaction without external activation to produce the toxic 1,4-benzenoid diradical species. C-1027 can induce oxygen-independent interstrand DNA crosslinks in addition to the oxygen-dependent single- and double-stranded DNA breaks typically generated by other enediynes. This unique oxygen-independent mechanism suggests that C-1027 may be effective against Tumor hypoxia, hypoxic tumor cells. C-102 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calicheamicin
The calicheamicins are a class of enediyne antitumor antibiotics derived from the bacterium '' Micromonospora echinospora'', with calicheamicin γ1 being the most notable. It was isolated originally in the mid-1980s from the chalky soil, or "caliche pits", located in Kerrville, Texas. The sample was collected by a scientist working for Lederle Labs. It is extremely toxic to all cells and, in 2000, a CD33 antigen-targeted immunoconjugate N-acetyl dimethyl hydrazide calicheamicin was developed and marketed as targeted therapy against the non-solid tumor cancer acute myeloid leukemia (AML). A second calicheamicin-linked monoclonal antibody, inotuzumab ozogamicin (marketed as Besponsa), an anti-CD22-directed antibody-drug conjugate, was approved by the U.S. Food and Drug Administration on August 17, 2017, for use in the treatment of adults with relapsed or refractory B-cell precursor acute lymphoblastic leukemia. Calicheamicin γ1 and the related enediyne esperamicin are two of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neocarzinostatin
Neocarzinostatin (NCS) is a macromolecular chromoprotein enediyne antitumor antibiotic secreted by ''Streptomyces macromomyceticus''. It consists of two parts, a labile chromophore (the non-protein molecular entity shown at right) and a 113 amino acid protein to which the chromophore is tightly and non- covalently bound with high affinity (Kd ~ 10−10 M). The non-protein component is a very potent DNA-damaging agent; However it is extremely unstable and the role of the protein is to protect it and release it to the target DNA. Opening of the epoxide under reductive conditions present in cells creates favorable conditions for a Bergman cyclization, leading to formation of a benzenoid diradical, followed by DNA strand cleavage. Another important member of the chromoprotein group of natural products is kedarcidin. As a medicine it is among the most potent, and in Japan only it has been used against liver cancer clinically. __TOC__ Biosynthesis of NCS Chromophore The biosynt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynemicin A
Dynemicin A is an anti-cancer enediyne drug. It displays properties which illustrate promise for cancer treatments, but still requires further research. History and background Dynemicin A was first isolated from the soil in the Gujarat State of India. It was discovered to be the natural product of the indigenous bacteria ''Micromonospora chersina''. The natural product displays a bright purple color due to the anthraquinone chromophore structure within it. Initially, this compound was isolated for its aesthetic properties as a dye until further research demonstrated its anti-cancer properties. Shortly after the compound's discovery, the Bristol-Myers Pharmaceutical Company elucidated the structure in Japan using X-ray diffraction studies of triacetyldynemicin A; a closely related compound. Synthesis The first reported chemical synthesis of dynemicin was accomplished by Myers and coworkers. Biosynthesis Dynemicin A is an antitumor natural product isolated from ''Micromonos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bergman Cyclization
The Masamune-Bergman cyclization or Masamune-Bergman reaction or Masamune-Bergman cycloaromatization is an organic reaction and more specifically a rearrangement reaction taking place when an enediyne is heated in presence of a suitable hydrogen donor (''Scheme 1''). It is the most famous and well-studied member of the general class of cycloaromatization reactions. It is named for Japanese-American chemist Satoru Masamune (b. 1928) and American chemist Robert G. Bergman (b. 1942). The reaction product is a derivative of benzene. The reaction proceeds by a thermal reaction or pyrolysis (above 200 °C) forming a short-lived and very reactive para-benzyne biradical species. It will react with any hydrogen donor such as 1,4-cyclohexadiene which converts to benzene. When quenched by tetrachloromethane the reaction product is a 1,4-dichlorobenzene and with methanol the reaction product is benzyl alcohol. When the enyne moiety is incorporated into a 10-membered hydrocarbo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micromonospora Echinospora
''Micromonospora echinospora'' is a species of bacteria that is known for producing the enediyne antibiotic calicheamicin The calicheamicins are a class of enediyne antitumor antibiotics derived from the bacterium '' Micromonospora echinospora'', with calicheamicin γ1 being the most notable. It was isolated originally in the mid-1980s from the chalky soil, or "cal ...s. References External linksType strain of ''Micromonospora echinospora'' at Bac''Dive'' - the Bacterial Diversity Metadatabase Micromonosporaceae Bacteria described in 1923 {{Micromonospora-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemotherapy
Chemotherapy (often abbreviated chemo, sometimes CTX and CTx) is the type of cancer treatment that uses one or more anti-cancer drugs (list of chemotherapeutic agents, chemotherapeutic agents or alkylating agents) in a standard chemotherapy regimen, regimen. Chemotherapy may be given with a cure, curative intent (which almost always involves combinations of drugs), or it may aim only to prolong life or to Palliative care, reduce symptoms (Palliative care, palliative chemotherapy). Chemotherapy is one of the major categories of the medical discipline specifically devoted to pharmacotherapy for cancer, which is called ''oncology#Specialties, medical oncology''. The term ''chemotherapy'' now means the non-specific use of intracellular poisons to inhibit mitosis (cell division) or to induce DNA damage (naturally occurring), DNA damage (so that DNA repair can augment chemotherapy). This meaning excludes the more-selective agents that block extracellular signals (signal transduction) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromophore
A chromophore is the part of a molecule responsible for its color. The word is derived . The color that is seen by our eyes is that of the light not Absorption (electromagnetic radiation), absorbed by the reflecting object within a certain wavelength spectrum of visible spectrum, visible light. The chromophore is a region in the molecule where the energy difference between two separate molecular orbitals falls within the range of the visible spectrum (or in informal contexts, the spectrum under scrutiny). Visible light that hits the chromophore can thus be absorbed by exciting an electron from its ground state into an excited state. In biological molecules that serve to capture or detect light energy, the chromophore is the Moiety (chemistry), moiety that causes a conformational change in the molecule when hit by light. Conjugated pi-bond system chromophores Just like how two adjacent p-orbitals in a molecule will form a pi-bond, three or more adjacent p-orbitals in a molec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thiol
In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols (that is, sulfur takes the place of oxygen in the hydroxyl () group of an alcohol), and the word is a blend of "''thio-''" with "alcohol". Many thiols have strong odors resembling that of garlic, cabbage or rotten eggs. Thiols are used as odorants to assist in the detection of natural gas (which in pure form is odorless), and the smell of natural gas is due to the smell of the thiol used as the odorant. Nomenclature Thiols are sometimes referred to as mercaptans () or mercapto compounds, a term introduced in 1832 by William Christopher Zeise and is derived from the Latin ('capturing mercury')''Oxford American Dictionaries'' (Mac OS X Leopard). because the thiolate grou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gram-negative Bacteria
Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the Crystal violet, crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists of a thin peptidoglycan gram-negative cell wall, cell wall sandwiched between an inner (Cytoplasm, cytoplasmic) Cell membrane, membrane and an Bacterial outer membrane, outer membrane. These bacteria are found in all environments that support life on Earth. Within this category, notable species include the model organism ''Escherichia coli'', along with various pathogenic bacteria, such as ''Pseudomonas aeruginosa'', ''Chlamydia trachomatis'', and ''Yersinia pestis''. They pose significant challenges in the medical field due to their outer membrane, which acts as a protective barrier against numerous Antibiotic, antibiotics (including penicillin), Detergent, detergents that would normally damage the inner cell membrane, and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gram-positive Bacteria
In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. The Gram stain is used by microbiologists to place bacteria into two main categories, gram-positive (+) and gram-negative (−). Gram-positive bacteria have a thick layer of peptidoglycan within the cell wall, and gram-negative bacteria have a thin layer of peptidoglycan. Gram-positive bacteria retain the crystal violet stain used in the test, resulting in a purple color when observed through an optical microscope. The thick layer of peptidoglycan in the bacterial cell wall retains the stain after it has been fixed in place by iodine. During the decolorization step, the decolorizer removes crystal violet from all other cells. Conversely, gram-negative bacteria cannot retain the violet stain after the decolorization step; alcohol used in this stage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
