The glycine receptor is the receptor of the amino acid neurotransmitter glycine. GlyR is an ionotropic receptor, it is one of the most distributed inhibitory receptors in the central nervous system and has important roles in a variety of physiological processes in mediating inhibitory neurotransmission in the spinal cord and brainstem. The receptor can be activated by a range of simple amino acids including glycine, β-alanine and taurine, can be selectively blocked by the high-affinity competitive antagonist strychnine. Caffeine is a competitive antagonist of GlyR. Gephyrin has been shown to be necessary for GlyR clustering at inhibitory synapses. GlyR is known to colocalize with the GABAA receptor on some hippocampal neurons; some exceptions can occur in the central nervous system where the GlyR α1 subunit and gephyrin, its anchoring protein, are not found in dorsal root ganglion neurons despite the presence of GABAA receptors. Strychnine-sensitive GlyRs are members of a family of ligand-gated ion channels.
Receptors of this family are arranged as five subunits surrounding a central pore, with each subunit composed of four α helical transmembrane segments. There are presently four known isoforms of the α-subunit of GlyR that are essential to bind ligands and a single β-subunit; the adult form of the GlyR is the heteromeric α1β receptor, believed to have a stoichiometry of three α1 subunits and two β subunits or four α1 subunits and one β subunit. The α-subunits are able to form functional homo-pentameric receptors in heterologous expression systems in African clawed frog's oocytes or mammalian cell lines, the α1 homomeric receptor is essential for studies of channel pharmacokinetics and pharmacodynamics. Auxiliary β subunit is unable to form functional channels without association with α subunits. However, previous reports have demonstrated that β subunit determines the synaptic localization of GlyRs, as well as the pharmacological profile of glycinergic currents Disruption of GlyR surface expression or reduced ability of expressed GlyRs to conduct chloride ions results in the rare neurological disorder, hyperekplexia.
The disorder is characterized by an exaggerated response to unexpected stimuli, followed by a temporary but complete muscular rigidity resulting in an unprotected fall. Chronic injuries as a result of the falls are symptomatic of the disorder. A mutation in GLRA1 is responsible for some cases of stiff person syndrome. Β-Alanine D-Alanine D-Serine Glycine Hypotaurine Ivermectin L-Alanine L-Proline L-Serine Milacemide Quisqualamine Sarcosine Taurine THC Ethanol Toluene Bicuculline Brucine Caffeine Levorphanol Picrotoxin Strychnine Tutin Glycine+Receptors at the US National Library of Medicine Medical Subject Headings
Xenon is a chemical element with symbol Xe and atomic number 54. It is a colorless, odorless noble gas found in the Earth's atmosphere in trace amounts. Although unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized. Xenon is used in flash lamps and arc lamps, as a general anesthetic; the first excimer laser design used a xenon dimer molecule as the lasing medium, the earliest laser designs used xenon flash lamps as pumps. Xenon is used to search for hypothetical weakly interacting massive particles and as the propellant for ion thrusters in spacecraft. Occurring xenon consists of eight stable isotopes. More than 40 unstable xenon isotopes undergo radioactive decay, the isotope ratios of xenon are an important tool for studying the early history of the Solar System. Radioactive xenon-135 is produced by beta decay from iodine-135, is the most significant neutron absorber in nuclear reactors. Xenon was discovered in England by the Scottish chemist William Ramsay and English chemist Morris Travers in September 1898, shortly after their discovery of the elements krypton and neon.
They found xenon in the residue left over from evaporating components of liquid air. Ramsay suggested the name xenon for this gas from the Greek word ξένον, neuter singular form of ξένος, meaning'foreign','strange', or'guest'. In 1902, Ramsay estimated the proportion of xenon in the Earth's atmosphere to be one part in 20 million. During the 1930s, American engineer Harold Edgerton began exploring strobe light technology for high speed photography; this led him to the invention of the xenon flash lamp in which light is generated by passing brief electric current through a tube filled with xenon gas. In 1934, Edgerton was able to generate flashes as brief as one microsecond with this method. In 1939, American physician Albert R. Behnke Jr. began exploring the causes of "drunkenness" in deep-sea divers. He tested the effects of varying the breathing mixtures on his subjects, discovered that this caused the divers to perceive a change in depth. From his results, he deduced. Although Russian toxicologist Nikolay V. Lazarev studied xenon anesthesia in 1941, the first published report confirming xenon anesthesia was in 1946 by American medical researcher John H. Lawrence, who experimented on mice.
Xenon was first used as a surgical anesthetic in 1951 by American anesthesiologist Stuart C. Cullen, who used it with two patients. Xenon and the other noble gases were for a long time considered to be chemically inert and not able to form compounds. However, while teaching at the University of British Columbia, Neil Bartlett discovered that the gas platinum hexafluoride was a powerful oxidizing agent that could oxidize oxygen gas to form dioxygenyl hexafluoroplatinate. Since O2 and xenon have the same first ionization potential, Bartlett realized that platinum hexafluoride might be able to oxidize xenon. On March 23, 1962, he mixed the two gases and produced the first known compound of a noble gas, xenon hexafluoroplatinate. Bartlett thought its composition to be Xe+−, but work revealed that it was a mixture of various xenon-containing salts. Since many other xenon compounds have been discovered, in addition to some compounds of the noble gases argon and radon, including argon fluorohydride, krypton difluoride, radon fluoride.
By 1971, more than 80 xenon compounds were known. In November 1989, IBM scientists demonstrated a technology capable of manipulating individual atoms; the program, called IBM in atoms, used a scanning tunneling microscope to arrange 35 individual xenon atoms on a substrate of chilled crystal of nickel to spell out the three letter company initialism. It was the first time atoms had been positioned on a flat surface. Xenon has atomic number 54. At standard temperature and pressure, pure xenon gas has a density of 5.761 kg/m3, about 4.5 times the density of the Earth's atmosphere at sea level, 1.217 kg/m3. As a liquid, xenon has a density of up to 3.100 g/mL, with the density maximum occurring at the triple point. Liquid xenon has a high polarizability due to its large atomic volume, thus is an excellent solvent, it can dissolve hydrocarbons, biological molecules, water. Under the same conditions, the density of solid xenon, 3.640 g/cm3, is greater than the average density of granite, 2.75 g/cm3.
Under gigapascals of pressure, xenon forms a metallic phase. Solid xenon changes from face-centered cubic to hexagonal close packed crystal phase under pressure and begins to turn metallic at about 140 GPa, with no noticeable volume change in the hcp phase, it is metallic at 155 GPa. When metallized, xenon appears sky blue because it absorbs red light and transmits other visible frequencies; such behavior is unusual for a metal and is explained by the small width of the electron bands in that state. Liquid or solid xenon nanoparticles can be formed at room temperature by implanting Xe+ ions into a solid matrix. Many solids have lattice constants smaller than solid Xe; this results in compression of the implanted Xe to pressures that may be sufficient for its liquefaction or solidification. Xenon is a member of the zero-valence elements that are called inert gases, it is inert to most common chemical reactions because the outer valence shell contains eight electrons. This produces a stable, minimum energy configuration in which the outer electrons are bound.
In a gas-filled tube, xenon em
Simplified molecular-input line-entry system
The simplified molecular-input line-entry system is a specification in the form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules; the original SMILES specification was initiated in the 1980s. It has since been extended. In 2007, an open standard called. Other linear notations include the Wiswesser line notation, ROSDAL, SYBYL Line Notation; the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. Acknowledged for their parts in the early development were "Gilman Veith and Rose Russo and Albert Leo and Corwin Hansch for supporting the work, Arthur Weininger and Jeremy Scofield for assistance in programming the system." The Environmental Protection Agency funded the initial project to develop SMILES. It has since been modified and extended by others, most notably by Daylight Chemical Information Systems.
In 2007, an open standard called "OpenSMILES" was developed by the Blue Obelisk open-source chemistry community. Other'linear' notations include the Wiswesser Line Notation, ROSDAL and SLN. In July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is considered to have the advantage of being more human-readable than InChI; the term SMILES refers to a line notation for encoding molecular structures and specific instances should be called SMILES strings. However, the term SMILES is commonly used to refer to both a single SMILES string and a number of SMILES strings; the terms "canonical" and "isomeric" can lead to some confusion when applied to SMILES. The terms are not mutually exclusive. A number of valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol. Algorithms have been developed to generate the same SMILES string for a given molecule; this SMILES is unique for each structure, although dependent on the canonicalization algorithm used to generate it, is termed the canonical SMILES.
These algorithms first convert the SMILES to an internal representation of the molecular structure. Various algorithms for generating canonical SMILES have been developed and include those by Daylight Chemical Information Systems, OpenEye Scientific Software, MEDIT, Chemical Computing Group, MolSoft LLC, the Chemistry Development Kit. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database; the original paper that described the CANGEN algorithm claimed to generate unique SMILES strings for graphs representing molecules, but the algorithm fails for a number of simple cases and cannot be considered a correct method for representing a graph canonically. There is no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, double bond geometry; these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES.
A notable feature of these rules is. The term isomeric SMILES is applied to SMILES in which isotopes are specified. In terms of a graph-based computational procedure, SMILES is a string obtained by printing the symbol nodes encountered in a depth-first tree traversal of a chemical graph; the chemical graph is first trimmed to remove hydrogen atoms and cycles are broken to turn it into a spanning tree. Where cycles have been broken, numeric suffix labels are included to indicate the connected nodes. Parentheses are used to indicate points of branching on the tree; the resultant SMILES form depends on the choices: of the bonds chosen to break cycles, of the starting atom used for the depth-first traversal, of the order in which branches are listed when encountered. Atoms are represented by the standard abbreviation of the chemical elements, in square brackets, such as for gold. Brackets may be omitted in the common case of atoms which: are in the "organic subset" of B, C, N, O, P, S, F, Cl, Br, or I, have no formal charge, have the number of hydrogens attached implied by the SMILES valence model, are the normal isotopes, are not chiral centers.
All other elements must be enclosed in brackets, have charges and hydrogens shown explicitly. For instance, the SMILES for water may be written as either O or. Hydrogen may be written as a separate atom; when brackets are used, the symbol H is added if the atom in brackets is bonded to one or more hydrogen, followed by the number of hydrogen atoms if greater than 1 by the sign + for a positive charge or by - for a negative charge. For example, for ammonium. If there is more than one charge, it is written as digit.
An inhalational anaesthetic is a chemical compound possessing general anaesthetic properties that can be delivered via inhalation. They are administered through a face mask, laryngeal mask airway or tracheal tube connected to an anaesthetic vaporiser and an anaesthetic delivery system. Agents of significant contemporary clinical interest include volatile anaesthetic agents such as isoflurane and desflurane, as well as certain anaesthetic gases such as nitrous oxide and xenon. Desflurane Isoflurane Nitrous oxide Sevoflurane Xenon Although some of these are still used in clinical practice and in research, the following anaesthetic agents are of historical interest in developed countries: Chloroethane Chloroform Cryofluorane Cyclopropane Diethyl ether Divinyl ether Enflurane Ethylene Fluroxene Halothane Methoxyflurane Methoxypropane Trichloroethylene Divinyl ether Aliflurane Halopropane Norflurane Roflurane Synthane Teflurane Volatile anaesthetic agents share the property of being liquid at room temperature, but evaporating for administration by inhalation.
All of these agents share the property of being quite hydrophobic. The ideal volatile anaesthetic agent offers smooth and reliable induction and maintenance of general anaesthesia with minimal effects on other organ systems. In addition it is pleasant to inhale, it is cheap to manufacture. None of the agents in use are ideal, although many have some of the desirable characteristics. For example, sevoflurane is is rapid in onset and offset, it is safe for all ages. However, it is expensive, half as potent as isoflurane. Other gases or vapors which produce general anaesthesia by inhalation include nitrous oxide and xenon; these are administered using flowmeters, rather than vaporisers. Cyclopropane is explosive and is no longer used for safety reasons, although otherwise it was found to be an excellent anaesthetic. Xenon is odourless and rapid in onset, but is expensive and requires specialized equipment to administer and monitor. Nitrous oxide at 80% concentration, does not quite produce surgical level anaesthesia in most persons at standard atmospheric pressure, so it must be used as an adjunct anaesthetic, along with other agents.
Under hyperbaric conditions, other gases such as nitrogen, noble gases such as argon and xenon become anaesthetics. When inhaled at high partial pressures, nitrogen begins to act as an anaesthetic agent, causing nitrogen narcosis. However, the minimum alveolar concentration for nitrogen is not achieved until pressures of about 20 to 30 atm are attained. Argon is more than twice as anaesthetic as nitrogen per unit of partial pressure. Xenon however is normal atmospheric pressure; the full mechanism of action of volatile anaesthetic agents is unknown and has been the subject of intense debate. "Anesthetics have been used for 160 years, how they work is one of the great mysteries of neuroscience," says anaesthesiologist James Sonner of the University of California, San Francisco. Anaesthesia research "has been for a long time a science of untestable hypotheses," notes Neil L. Harrison of Cornell University."Most of the injectable anesthetics appear to act on a single molecular target," says Sonner.
"It looks. That makes it a more difficult problem to pick apart." The possibility of anaesthesia by the inert gas argon in particular suggests that the mechanism of action of volatile anaesthetics is an effect best described by physical chemistry, not a chemical bonding action. However, the agent may bind to a receptor with a weak interaction. A physical interaction such as swelling of nerve cell membranes from gas solution in the lipid bilayer may be operative. Notably, the gases hydrogen and neon have not been found to have anaesthetic properties at any pressure. Helium at high pressures produces nervous irritation, suggesting that the anaesthetic mechanism may be operated in reverse by this gas; some halogenated ethers possess this "anti-anaesthetic" effect, providing further evidence for this theory. The concept was first used by Arabic physicians, such as Abulcasis and Ibn Zuhr in the 11th century, they used a sponge placed it on a patient's face. These Arabic physicians were the first to use an anaesthetic sponge.
Paracelsus developed an inhalational anaesthetic in 1540. He used sweet oil of vitriol: used to feed fowl: “it was taken by chickens and they fall asleep from it for a while but awaken without harm”. Subsequently, about 40 years in 1581, Giambattista Delia Porta demonstrated the use of ether on humans although it was not employed for any type of surgical anesthesia. A. C. E. M
Alfaxalone known as alphaxalone or alphaxolone and sold under the brand name Alfaxan, is a neuroactive steroid and general anesthetic, used in veterinary practice as an induction agent for anesthesia and as an injectable anesthetic. Though it is more expensive than other induction agents, it preferred due to the lack of depressive effects on the cardiovascular system; the most common side effect is respiratory depression. Alfaxalone works as a positive allosteric modulator on GABAA receptors and, at high concentrations, as a direct agonist of the GABAA receptor, it is cleared by the liver, giving it a short terminal half-life and preventing it from accumulating in the body, lowering the chance of overdose. Alfaxalone is used as an induction agent, an injectable anesthetic, a sedative in animals. While it is used in cats and dogs, it has been used in rabbits, sheep and exotics such as red-eared turtles, green iguanas and koi fish; as an induction agent, alfaxalone causes the animal to relax enough to be intubated, which allows the administration of inhalational anesthesia.
Premedication increases the potency of alfaxalone as an induction agent. Alfaxalone can be used instead of gas anesthetics in surgeries that are under 30 minutes, where it is given at a constant rate via IV. Once the administration of alfaxalone stops, the animal recovers from anesthesia. Alfaxalone can be used as a sedative when given intramuscularly, though this requires a larger volume. Despite its use as an anesthetic, alfaxalone itself has no analgesic properties. Though alfaxalone is not licensed for IM or subcutaneous use in the United States, it is used IM in cats, is licensed as such in other countries. Alfaxalone is dissolved in 2-hydroxylpropyl-β cyclodextrin; the cyclodextrin is a large, starch-derived molecule with a hydrophobic core where alfaxalone stays, allowing the mixture to be dissolved in water and sold as an aqueous solution. They act as one unit, only dissociate once in vivo; the lack of preservatives in alfaxalone vials gives them an short shelf-life once the seal has been broken, as microbes can grow inside the vial.
Official instructions in the U. K. are to discard the rest immediately. In the United States, a vial of alfaxalone can be kept up to six hours after its first use. In New Zealand and Australia, a used vial can be kept in a fridge for up to seven days. Alfaxalone has been used to perform c-sections in pregnant cats. Alfaxalone has been found to be safe in young puppies and kittens. Alfaxalone has been noted to be a good anesthetic agent for dogs with ventricular arrhythmias and for sighthounds. Alfaxalone has few side effects compared to other anesthetics; the most common side effect is respiratory depression: in addition to apnea, the most prevalent, alfaxalone can decrease the respiratory rate, minute volume, oxygen saturation in the blood. Alfaxalone should be administered over a period of at least 60 seconds or until anesthesia is induced, as quick administration increases the risk of apnea. Alfaxalone has some depressive effects on the central nervous system, including a reduction in cerebral flood flow, intracranial pressure, body temperature.
Greyhounds, who are susceptible to anesthetic side effects, can have decreased blood flow and oxygen supply to the liver. When no premedications are used, alfaxalone causes animals to be agitated. Dogs and cats will paddle in the air, vocalize excessively, may remain rigid or twitch, have exaggerated reactions to external stimuli such as light and noise. For this reason, it is recommended that animals recovering from anesthesia by alfaxalone stay in a quiet, dark area; the quick metabolism and elimination of alfaxalone from the body decreases the chance of overdose. It would take over 28 times the normal dose to cause toxicity in cats; such doses, can cause low blood pressure, apnea and arrhythmia. Alfaxalone is a neuroactive steroid derived from progesterone, though it has no glucocorticoid or mineralocorticoid action. Instead, it works by acting on GABAA receptors, it binds to the M3/M4 domains of the α subunit and allosterically modifies the receptor to facilitate the movement of chloride ions into the cell, resulting in hyperpolarization of the post-synaptic nerve.
At concentrations over 1 micromolar, alfaxalone binds to a site at the interface between the α and β subunits and acts as a GABA agonist, similar to benzodiazepines. Alfaxalone, does not share the benzodiazepine binding site, prefers different GABAA receptors than benzodiazepenes do, it works best on the α1-β2-γ2-L isoform. Research suggests that neuroactive steroids increase the expression of GABAA receptors, making it more difficult to build tolerance. Alfaxalone is metabolized and does not accumulate in the body
Halothane, sold under the brand name Fluothane among others, is a general anesthetic. It can be used to maintain anaesthesia. One of its benefits is that it does not increase the production of saliva, which can be useful in those who are difficult to intubate, it is given by inhalation. Side effects include an irregular heartbeat, decreased effort to breathe, liver problems. Like all volatile anesthetics, it should not be used in people with a personal or family history of malignant hyperthermia, it appears to be safe in porphyria. It is unclear whether use during pregnancy is harmful to the baby, it is not recommended for use during a C-section. Halothane is a chiral molecule, used as a racemic mixture. Halothane was discovered in 1955, it is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. As of 2014, the wholesale cost in the developing world is about 22 to 52 USD for a 250 mL bottle, its use in developed countries has been replaced by newer anesthetic agents such as sevoflurane.
It is no longer commercially available in the United States. Halothane contributes to ozone depletion, it is a potent anesthetic with a MAC of 0.74%. Its blood/gas partition coefficient of 2.4 makes it an agent with moderate induction and recovery time. It is not a good analgesic and its muscle relaxation effect is moderate. In rare cases, repeated exposure to halothane in adults was noted to result in severe liver injury; this occurred in about one in 10,000 exposures. The resulting syndrome was referred to as halothane hepatitis, is thought to result from the metabolism of halothane to trifluoroacetic acid via oxidative reactions in the liver. About 20% of inhaled halothane is metabolized by the liver and these products are excreted in the urine; the hepatitis syndrome had a mortality rate of 30% to 70%. Concern for hepatitis resulted in a dramatic reduction in the use of halothane for adults and it was replaced in the 1980s by enflurane and isoflurane. By 2005, the most common volatile anesthetics used were isoflurane and desflurane.
Since the risk of halothane hepatitis in children was lower than in adults, halothane continued to be used in pediatrics in the 1990s as it was useful for inhalation induction of anaesthesia. However, by 2000, excellent for inhalation induction, had replaced the use of halothane in children. Halothane sensitises the heart to catecholamines, so it is liable to cause cardiac arrhythmias fatal if hypercapnia has been allowed to develop; this seems to be problematic in dental anaesthesia. Like all the potent inhalational anaesthetic agents, it is a potent trigger for malignant hyperthermia. In common with the other potent inhalational agents, it relaxes uterine smooth muscle and this may increase blood loss during delivery or termination of pregnancy. People can be exposed to halothane in the workplace by breathing it in as waste anaesthetic gas, skin contact, eye contact, or swallowing it; the National Institute for Occupational Safety and Health has set a recommended exposure limit of 2 ppm over 60 minutes.
Halothane activates glycine receptors. It acts as an NMDA receptor antagonist, inhibits nACh and voltage-gated sodium channels, activates 5-HT3 and twin-pore K+ channels, it does not affect the AMPA or kainate receptors. Chemically, halothane is an alkyl halide; the structure has one stereocenter, so - and -optical isomers occur. The commercial synthesis of halothane starts from trichloroethylene, reacted with hydrogen fluoride in the presence of antimony trichloride at 130 °C to form 2-chloro-1,1,1-trifluoroethane; this is reacted with bromine at 450 °C to produce halothane. Attempts to find anesthetics with less metabolism led to halogenated ethers such as enflurane and isoflurane; the incidence of hepatic reactions with these agents is lower. The exact degree of hepatotoxic potential of enflurane is debated, although it is minimally metabolized. Isoflurane is not metabolized and reports of associated liver injury are quite rare. Small amounts of trifluoroacetic acid can be formed from both halothane and isoflurane metabolism and accounts for cross sensitization of patients between these agents.
The main advantage of the more modern agents is lower blood solubility, resulting in faster induction of and recovery from anaesthesia. Halothane was first synthesized by C. W. Suckling of Imperial Chemical Industries in 1951 in Widnes and was first used clinically by M. Johnstone in Manchester in 1956, it became popular as a nonflammable general anesthetic replacing other volatile anesthetics such as trichloroethylene, diethyl ether and cyclopropane. In many parts of the world it has been replaced by newer agents since the 1980s but is still used in developing countries and in veterinary surgery because of its lower cost. Halothane was given to many millions of adult and pediatric patients worldwide from its introduction in 1956 through the 1980s, its properties include cardiac depression at high levels, cardiac sensitization to catecholamines such as norepinephrine, potent bronchial relaxation. Its lack of airway irritation made it a common inhalation induction agent in pediatric anesthesia.
Due to its cardiac depressive effect, it was contraindicated in patients with cardiac failure. Halothane was contraindicated in patients susceptible to cardiac arrhythmias, or in situations related to high catecholamine levels such as pheochromocytoma, it is available as a volatile liquid, at 30, 50, 200, 250 ml per container but in many developed nations is not available having been displa
Nitrous oxide known as laughing gas or nitrous, is a chemical compound, an oxide of nitrogen with the formula N2O. At room temperature, it is a colourless non-flammable gas, with taste. At elevated temperatures, nitrous oxide is a powerful oxidiser similar to molecular oxygen, it is soluble in water. Nitrous oxide has significant medical uses in surgery and dentistry, for its anaesthetic and pain reducing effects, its name "laughing gas", coined by Humphry Davy, is due to the euphoric effects upon inhaling it, a property that has led to its recreational use as a dissociative anaesthetic. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system, it is used as an oxidiser in rocket propellants, in motor racing to increase the power output of engines. Nitrous oxide occurs in small amounts in the atmosphere, but has been found to be a major scavenger of stratospheric ozone, with an impact comparable to that of CFCs, it is estimated that 30% of the N2O in the atmosphere is the result of human activity, chiefly agriculture.
Nitrous oxide may be used as an oxidiser in a rocket motor. This is advantageous over other oxidisers in that it is much less toxic, due to its stability at room temperature is easier to store and safe to carry on a flight; as a secondary benefit, it may be decomposed to form breathing air. Its high density and low storage pressure enable it to be competitive with stored high-pressure gas systems. In a 1914 patent, American rocket pioneer Robert Goddard suggested nitrous oxide and gasoline as possible propellants for a liquid-fuelled rocket. Nitrous oxide has been the oxidiser of choice in several hybrid rocket designs; the combination of nitrous oxide with hydroxyl-terminated polybutadiene fuel has been used by SpaceShipOne and others. It is notably used in amateur and high power rocketry with various plastics as the fuel. Nitrous oxide may be used in a monopropellant rocket. In the presence of a heated catalyst, N2O will decompose exothermically into nitrogen and oxygen, at a temperature of 1,070 °F.
Because of the large heat release, the catalytic action becomes secondary, as thermal autodecomposition becomes dominant. In a vacuum thruster, this may provide a monopropellant specific impulse of as much as 180 s. While noticeably less than the Isp available from hydrazine thrusters, the decreased toxicity makes nitrous oxide an option worth investigating. Nitrous oxide is said to deflagrate at 600 °C at a pressure of 309 psi. At 600 psi, for example, the required ignition energy is only 6 joules, whereas N2O at 130 psi a 2,500-joule ignition energy input is insufficient. In vehicle racing, nitrous oxide allows the engine to burn more fuel by providing more oxygen than air alone, resulting in a more powerful combustion; the gas is not flammable at a low pressure/temperature, but it delivers more oxygen than atmospheric air by breaking down at elevated temperatures. Therefore, it is mixed with another fuel, easier to deflagrate. Nitrous oxide is a strong oxidant equivalent to hydrogen peroxide, much stronger than oxygen gas.
Nitrous oxide is stored as a compressed liquid. Sometimes nitrous oxide is injected into the intake manifold, whereas other systems directly inject, right before the cylinder to increase power; the technique was used during World War II by Luftwaffe aircraft with the GM-1 system to boost the power output of aircraft engines. Meant to provide the Luftwaffe standard aircraft with superior high-altitude performance, technological considerations limited its use to high altitudes. Accordingly, it was only used by specialised planes such as high-altitude reconnaissance aircraft, high-speed bombers and high-altitude interceptor aircraft, it sometimes could be found on Luftwaffe aircraft fitted with another engine-boost system, MW 50, a form of water injection for aviation engines that used methanol for its boost capabilities. One of the major problems of using nitrous oxide in a reciprocating engine is that it can produce enough power to damage or destroy the engine. Large power increases are possible, if the mechanical structure of the engine is not properly reinforced, the engine may be damaged, or destroyed, during this kind of operation.
It is important with nitrous oxide augmentation of petrol engines to maintain proper operating temperatures and fuel levels to prevent "pre-ignition", or "detonation". Most problems that are associated with nitrous oxide do not come from mechanical failure due to the power increases. Since nitrous oxide allows a much denser charge into the cylinder, it increases cylinder pressures; the increased pressure and temperature can cause problems such as melting valves. It may crack or warp the piston or head and cause pre-ignition due to uneven heating. Automotive-grade liquid nitrous oxide differs from medical-grade nitrous oxide. A small amount of sulfur dioxide is added to prevent substance abuse. Multiple washes through a base can remove this, decreasing the corrosive properties observed when SO2 is further oxidised during combustion into sulfuric