Wiktionary Hydrophobia or hydrophobe may refer to Rabies , especially a set of symptoms of the later stages of an infection, in which the victim has difficulty swallowing, shows panic when presented with liquids to drink, and cannot quench his or her thirst. Phobia of water this is mainly colloquial, phobia of water is usually called aquaphobia , see below, to differentiate it from rabies. Aquaphobia , a morbid fear of water, or of swimming. Hydrophobe , a term used in chemistry to describe chemical aversions of a molecule, or part of a molecule, to water. Hydrophobia video game Hydrophobia video game Hydrophobia, a Hungarian List of disk magazines H disk magazine 1996 1997 disambig de Hydrophobie Begriffskl rung es Hidrofobia fr Hydrophobie ... more details
Multiple issues primarysources December 2010 onesource December 2010 Protectosil is a silane manufactured by Evonik and marketed a protective coating for building surfaces. It is used as a Hydrophobe water repellant , and for corrosion and graffiti control. ref Cite web url http www.protectosil.com title Protectosil format work accessdate 2008 06 11 ref References Reflist Category Brand name materials Category Silanes Material stub ... more details
Magic sand , Mars Sand , Space Sand , Nickelodeon Compounds Nickelodeon Sqand Sqand or Aqua Sand is a toy made from sand coated with a Hydrophobe hydrophobic compound. The presence of this hydrophobic compound causes the grains of sand to adhere to one another and form cylinder geometry cylinder s to minimize surface area when exposed to water. As soon as the sand is taken out of water, it is completely dry and flows freely. These properties are achieved by covering ordinary beach sand, which contains tiny particles of pure silica , and exposing them to vapors of trimethylsilanol Methyl CH sub 3 sup sub 3 sub Silicon Si Hydroxyl OH , an organosilicon compound. Upon exposure, the trimethylsilane compound bonds to the silica particles while forming water. The exteriors of the sand grains are thus coated with Hydrophobe hydrophobic groups. Magic sand was originally developed to trap ocean oil spill s near the shore. This would be done by sprinkling Magic sand on floating petroleum, which would then mix with the oil and make it heavy enough to sink. However, due to the expense of production, it is not being used for this purpose. It has also been tested by utility companies in the Arctic areas as a foundation for junction boxes, as it never freezes. It can be also used as an aerating medium for potted plants. Magic sand is made in blue, green, or red in colors but appears silvery in water because of a layer of air that forms around the sand. External links http portal.acs.org portal fileFetch C CTP 004121 pdf CTP 004121.pdf Magic Sand Experiment from the American Chemical Society dead link date December 2010 http www.neatorama.com 2006 06 06 magic sand remains dry after being submerged in water Video of Magic sand http www.youtube.com watch?gl US&hl uk&v 1id gHQjbs Magic Sand http video.google.de videoplay?docid 7066932745657984611&q type 3Agpick Google Video how to make magic sand at your home http inventorspot.com articles aqua sand sand never gets wet 36151 Aqua Sand ... more details
lowercase Fluids Home is a computer simulation of two phase flow behavior in microgravity and microfluidics ref cite web url http news.uns.purdue.edu html4ever 2004 040107.Ladisch.chip.html title Purdue engineers develop quick, inexpensive method to prototype microchips publisher News.uns.purdue.edu date 2004 01 07 accessdate 2011 02 20 ref problems at Purdue University , using the Surface Evolver program. About The project s purpose is to develop better methods for the management of liquid rocket propellant s in microgravity, ref cite web url http news.uns.purdue.edu x 2007b 070905CollicottSatellites.html title Engineers rescue aging satellites, saving millions publisher News.uns.purdue.edu date 2007 09 05 accessdate 2011 02 20 ref ref cite web url http news.uns.purdue.edu insidepurdue 2009 090716 ResearchCollicott.html title Research focuses on fuel injection in rockets publisher News.uns.purdue.edu date 2009 07 16 accessdate 2011 02 20 ref and to investigate two phase flow in microelectromechanical systems , taking into account factors like surface tension . Systems can then be designed that use electrowetting , channel geometry , and Hydrophobe hydrophobic or Hydrophile hydrophilic coating s to allow the smooth passage of fluids. Such systems would include compact medical device s, biosensor s, ref cite web url http news.uns.purdue.edu x 2009a 090421WereleyChips.html title Innovation could make lab on a chip devices easier to use, cheaper to make publisher News.uns.purdue.edu date 2009 04 21 accessdate 2011 02 20 ref and fuel cell s, to name a few. Computing platform It uses the Berkeley Open Infrastructure for Network Computing BOINC distributed computing platform. Application notes There is no screen saver. Work unit Central processing unit CPU times are generally less than 20 hours. Work units average in size around 500 Kilobyte kB . You have to run many work units to get levels of credit comparable to SETI Home or Climateprediction.net distributed programs. ... more details
refimprove date March 2010 Image Scheme facilitated diffusion in cell membrane en.svg thumb 300px right Facilitated diffusion in cell membrane, showing ion channel s and carrier proteins Not to be confused with diffusion . Facilitated diffusion is not a type of diffusion thermal motion but a type of transport process. Facilitated diffusion also known as facilitated transport or passive mediated transport is a process of passive transport , facilitated by integral proteins. Facilitated diffusion is the spontaneous passage of molecules or ions across a biological membrane passing through specific transmembrane integral proteins. The facilitated diffusion may occur either across biological membrane s or through aqueous compartments of an organism. ref name isbn0 471 41759 9 cite book author Pratt, Charlotte Amerley Voet, Donald Voet, Judith G. title Fundamentals of biochemistry upgrade publisher Wiley location New York year 2002 pages 264 266 isbn 0 471 41759 9 oclc doi accessdate ref Polar molecules and charged ions are dissolved in water but they can not diffuse freely across the plasma membrane due to the hydrophobe hydrophobic nature of the fatty acid tails of phospholipid s that make up the lipid bilayer s. Only small nonpolar molecules, such as oxygen can diffuse easily across the membrane. All polar molecules are transported across cell membrane membranes by proteins that form transmembrane channels. These channels are gated so they can open and close, thus regulating the flow of ions or small polar molecules. Larger molecules are transported by transmembrane carrier proteins, such as permease s that change their conformation as the molecules are carried through, for example glucose or amino acids . Non polar molecules, such as retinol or fatty acid s are poorly soluble in water. They are transported through aqueous compartments of cells or through extracellular space by water soluble carriers as retinol binding protein . The metabolites are not changed because ... more details
Technical date August 2010 section Biomolecular structure Image Collagentriplehelix.png thumb right 79px Tropocollagen triple helix. Scleroproteins , or fibrous proteins , constitute one of the two main classes of protein s, alongside globular protein s. Keratin , collagen , elastin , and fibroin ref name urlFibrous Protein Homepage Cite web url http web.chemistry.gatech.edu williams bCourse Information 6521 protein fibrous fibrous.html title Fibrous Protein Homepage work accessdate 2008 11 26 ref are all scleroproteins. The roles of such proteins include protection and support, ref DorlandsDict seven 000095173 scleroprotein ref forming connective tissue , tendon s, Bone Matrix bone matrices , and muscle fiber . Biomolecular structure A scleroprotein forms long protein filament s, which are shaped like rods wires. Scleroprotein are structural proteins or storage protein s that are typically inert and water Solubility insoluble . A Scleroprotein occurs as an aggregate due to Hydrophobe hydrophobic side chain s that protrude from the molecule. A scleroprotein s peptide sequence often has limited Residue chemistry residues with repeats these can form unusual secondary structure s, such as a collagen helix . The structures often feature cross links between chains e.g., cys cys disulfide bond s between keratin chains . Scleroproteins tend not to Denaturation biochemistry denature as easily as globular protein s. Miroshnikov et al. 1998 are among the researchers who have attempted to synthesize fibrous proteins. ref name pmid9680195 Cite journal author Miroshnikov KA, Marusich EI, Cerritelli ME, et al. title Engineering trimeric fibrous proteins based on bacteriophage T4 adhesins journal Protein Eng. volume 11 issue 4 pages 329 32 year 1998 month April pmid 9680195 doi 10.1093 protein 11.4.329 url http peds.oxfordjournals.org cgi pmidlookup?view long&pmid 9680195 ref References Reflist External links MeshName Scleroproteins Protein topics Fibrous proteins Category Molecul ... more details
Pfam box Symbol Hydrophobin 2 Name Fungal hydrophobin image Hydrophobin.png width 250 caption Structure of hydrophobin HFBI from Trichoderma reesei Pfam PF06766 InterPro IPR010636 SMART PROSITE PDOC00739 SCOP 1r2m TCDB OPM family OPM protein 1r2m PDB PDB3 1r2m B 17 82 Hydrophobins are a class of small, cysteine rich proteins 100 amino acids that are expressed only by Mold filamentous fungi . They are known for their capability of forming a Hydrophobe hydrophobic water repellent coating on a surface of an object. They were first discovered and separated in Schizophyllum commune in 1991. Based on differences in hydropathy patterns and biophysics biophysical properties, they are divided into two categories class I and class II. Fungi make complex aerial structures and spores even in aqueous environments. Hydrophobins have been identified in ascomycetes and basidiomycetes whether they exist in other groups is not known. ref cite pmid 11544369 ref Hydrophobins are generally found on the outer surface of Conidium conidia and of the Hypha hyphal wall, and may be involved in mediating contact and communication between the fungus and its environment. ref name PUB00012827 cite journal author Whiteford JR, Spanu PD title The hydrophobin HCf 1 of Cladosporium fulvum is required for efficient water mediated dispersal of conidia journal Fungal Genet. Biol. volume 32 issue 3 pages 159 168 year 2001 pmid 11343402 doi 10.1006 fgbi.2001.1263 ref Some family members contain multiple copies of the domain. References reflist Further reading cite paper author Scholtmeijer, Karin title Expression and engineering of hydrophobin genes publisher University of Groningen date 2000 url http irs.ub.rug.nl ppn 240088549 cite journal author J. Hakanp , A. Paananen, S. Askolin, T. Nakari Set l , T. Parkkinen, M. Penttil , M. B. Linder, J. Rouvinen title Atomic Resolution Structure of the HFBII Hydrophobin, a Self assembling Amphiphile journal The Journal of Biological Chemistry volume 279 issue 1 ... more details
otheruses4 the traction aid the heraldic device crampon heraldry Image Crampon.JPG thumb right 250px Rigid step in crampons used for vertical ice climbing Crampons are traction devices used to improve mobility on snow and ice . ref name freedom cite book edition 7 editor Cox, Steven M. and Kris Fulsaas, ed. title Mountaineering The Freedom of the Hills publisher The Mountaineers isbn 0898868289 location Seattle year 2003 09 ref There are three main attachment systems for footwear step in, hybrid, and strap bindings. The first two require boots with welt s, the last adapt to any type. Oscar Eckenstein designed the first 10 point crampon in 1908, dramatically reducing the need for step cutting. This design was then made commercially available by the Italian Henry Grivel. Characteristics Image Strap on crampon.JPG thumb right Yellow grey plastic anti balling plates prevent snow from building up Materials Crampons are made of hardened steel, light weight aluminum, or a combination of the two. Lighter weight crampons are popular for ski touring alpine ski touring where demands are generally lower and light weight a premium. Points Early 10 point crampons lacked forward angled spikes and thus required step cutting on steep terrain. In the 1930s two additional forward slanting points were added, making them exceptional for mountaineering and glacier travel and beginning a revolution in front pointing . Today, specialized crampons with as many as 14 points, and models with single monopoints for ice climbing , are made. Attachment Improved attachment systems such as a cam action step in system similar to a ski binding and particularly well adapted to plastic technical mountaineering boots have widely increased crampons use. Anti balling To prevent snow from balling up under crampons, especially in temperatures around freezing, most models can be fitted with plastic or rubber anti balling sytems to reduce build up. Rubber models use flexion to repel snow while plastic employ ... more details
Image Jonofory.png thumb right 350 px Carrier Ionophores An ionophore is a lipid soluble molecule usually synthesized by microorganisms to transport ion s across the lipid bilayer of the cell membrane . There are two broad classifications of ionophores. Chemical compound s mobile ion carriers that bind to a particular ion, ref GoldBookRef title Ionophore file IT06772 ref shielding its charge from the surrounding environment, and thus facilitating its crossing of the Hydrophobe hydrophobic interior of the lipid membrane. Channel formers ref cite web url http www.ncbi.nlm.nih.gov sites entrez?Db mesh&Cmd ShowDetailView&TermToSearch 68007476&ordinalpos 1&itool EntrezSystem2.PEntrez.Mesh.Mesh ResultsPanel.Mesh RVDocSum title Ionophores MeSH Result format work accessdate ref that introduce a hydrophilic pore into the membrane, allowing ions to pass through while avoiding contact with the membrane s hydrophobic interior. Ionophores disrupt transmembrane ion concentration gradients, required for the proper functioning and survival of microorganisms, and thus have antibiotic properties. They are produced naturally by certain microbes and act as a defense against competing microbes. In laboratory research, ionophores are used to increase the permeability of biological membranes to certain ions. Additionally, some ionophores are used as antibiotics and or as growth enhancing feed additives for certain feed animals such as cattle see monensin . The U.S. Department of Agriculture sent a letter to Tyson Foods to remove labels for chickens that said raised without antibiotics because of the use of ionophores in their feed. ref cite web first Marcus last Kabel coauthors Christine Simmons title USDA Revokes OK for Tyson Chicken Labels date 2007 11 20 url http ap.google.com article ALeqM5iYfYJmjwYMb 6RiqjCbJ481k5xjgD8T16P5O0 accessdate 2007 11 20 ref Representative ionophores with the ion s they act upon 2,4 Dinitrophenol H sup sup A23187 Ca sup 2 sup Beauvericin Ca sup 2 sup , Ba s ... more details
chembox verifiedrevid 399188046 ImageFile bmim.svg ImageSize IUPACName 1 butyl 3 methylimidazol 3 ium hexafluorophosphate OtherNames BMIM PF sub 6 sub Section1 Chembox Identifiers ChemSpiderID Ref chemspidercite correct chemspider ChemSpiderID 2015930 InChI 1 C8H15N2.F6P c1 3 4 5 10 7 6 9 2 8 10 1 7 2,3,4,5 6 h6 8H,3 5H2,1 2H3 q 1 1 SMILES1 CCCCn1cc n c1 C.F P F F F F F InChIKey IXQYBUDWDLYNMA UHFFFAOYAH StdInChI 1S C8H15N2.F6P c1 3 4 5 10 7 6 9 2 8 10 1 7 2,3,4,5 6 h6 8H,3 5H2,1 2H3 q 1 1 StdInChIKey IXQYBUDWDLYNMA UHFFFAOYSA N CASNo 174501 64 5 PubChem 2734174 SMILES CCCCN1C C N C1 C.F P F F F F F Section2 Chembox Properties Formula C sub 8 sub H sub 15 sub F sub 6 sub N sub 2 sub P MolarMass 284.18228 Appearance Light Yellow, Liquid Density 1.38 g mL at 20 C MeltingPt BoilingPt Solubility Section3 Chembox Hazards MainHazards FlashPt Autoignition 1 Butyl 3 methylimidazolium hexafluorophosphate , also known as BMIM PF sub 6 sub , is a viscous, colourless, hydrophobe hydrophobic and non water soluble ionic liquid . Together with 1 butyl 3 methylimidazolium tetrafluoroborate, BMIM BF sub 4 sub , it is one of the most widely studied ionic liquids and is commercially available from most of the major international suppliers of chemicals. It is known to very slowly decompose in the presence of water. ref cite journal author R.P. Swatloski, J.D. Holbrey and R.D. Rogers title Ionic liquids are not always green hydrolysis of 1 butyl 3 methylimidazolium hexafluorophosphate journal Green Chem. year 2003 volume 5 pages 361 363 doi 10.1039 b304400a ref Preparation BMIM PF sub 6 sub is commercially available. It may be obtained in two steps BMIM Cl is synthesized by alkylating 1 methylimidazole with 1 chlorobutane . A metathesis reaction with potassium hexafluorophosphate gives the desired compound the tetrafluoroborate may be prepared by analogously using potassium tetrafluoroborate . ref OrgSynth author Dupont, J., Consorti, C., Suarez, P., de Souza, R. title Preparation of 1 ... more details
A multiphasic liquid is a mixture consisting of more than two miscibility immiscible liquid Phase matter phases . Biphasic mixtures consisting of two immiscible phases are very common and usually consist of an organic compound organic solvent and an water molecule aqueous phase oil and water . Multiphasic liquids are rare and only triphasic three phases and tetraphasic four phases are known. Multiphasic liquids can be used for selective liquid liquid extraction s or for decorative purposes, e.g. in cosmetics . While it is possible to get multilayered phases by layering Nonpolarity nonpolar and aqueous phases of decreasing density densities on top of each other, these phases will not separate after mixing like true multiphasic liquids. Compositions The following types of multiphasic liquids exist Triphasic systems Nonpolar solvent aqueous biphasic mixture e.g. using hexane , heptane , cyclohexane , or mineral oil as the nonpolar solvent Nonpolar solvent Polar molecule polar solvent salt water e.g. 100 ml mineral oil, 100 ml isopropanol , 75 ml water molecule water , 35 g calcium chloride Nonpolar solvent water soluble polymer A, water soluble polymer B, water e.g. hexane, polyethylene oxide , dextran , water Nonpolar solvent water soluble polymer salt water e.g. hexane, polyethylene oxide, sodium sulfate , water Nonpolar solvent A solvent B polymer soluble in solvent B and water water e.g. heptane, dichloromethane , polyethylene oxide, water Nonpolar solvent A solvent B polymer soluble in solvent B and water salt water e.g. 16.3 heptane, 21.7 dichloromethane, 9.5 polyethylene oxide, 51.5 water, 0.1 sodium sulfate Nonpolar solvent hydrophobe hydrophobic salt water e.g. 2,2,4 Trimethylpentane iso octane , Aliquat 336 methyltrioctylammonium chloride, a phase transfer catalyst , water http venus.unive.it alvise index file page0003.htm or cyclohexane, 1 Butyl 3 methylimidazolium hexafluorophosphate bmim PF sub 6 sub an ionic liquid , water http www.mariecurie.org annals v ... more details
Image DAGv1.png thumb right 250px 1 Palmitoyl 2 oleoyl glycerol A diglyceride , or a diacylglycerol DAG , is a glyceride consisting of two fatty acid chains covalent bond covalently bonded to a glycerol molecule through ester linkages. One example, shown on the right, is 1 palmitoyl 2 oleoyl glycerol, which contains side chains derived from palmitic acid and oleic acid . Diacylglycerols can also have many different combinations of fatty acids attached at both the C 1 and C 2 positions. Food additive Mono and diacylglycerols are common food additives used to blend together certain ingredients, such as oil and water, which would not otherwise blend well. The commercial source may be either animal cow or hog derived or vegetable, derived primarily from soy bean and canola oil. They may also be synthetically produced. They are often found in bakery products, beverages, ice cream, chewing gum, shortening , whipped toppings, margarine, and confections. Biological functions PKC activation Image PIP2 cleavage to IP3 and DAG.jpg thumb PIP2 cleavage to IP3 and DAG initiates intracellular calcium release and PKC activation. In biochemical signaling, diacylglycerol functions as a second messenger lipid signaling signaling lipid , and is a product of the hydrolysis of the phospholipid PIP2 phosphatidyl inositol bisphosphate by the enzyme phospholipase C phospholipase C PLC a cell membrane membrane bound enzyme that, through the same reaction, produces inositol trisphosphate IP sub 3 sub . Although inositol trisphosphate IP sub 3 sub diffuses into the cytosol , diacylglycerol DAG remains within the plasma membrane , due to its hydrophobe hydrophobic properties. IP sub 3 sub stimulates the release of calcium ions from the smooth endoplasmic reticulum, whereas DAG is a physiological activator of protein kinase C PKC . The production of DAG in the membrane facilitates translocation of PKC from the cytosol to the plasma membrane . Diacylglycerol can be mimicked by the tumor promoting ... more details
Membrane fouling is a process where solute or particles deposit onto a Artificial membrane membrane surface or into membrane pores in a way that degrades the membrane s performance. It is a major obstacle to the widespread use of this technology. Membrane fouling can cause severe flux decline and affect the quality of the water produced. Severe fouling may require intense chemical cleaning or membrane replacement. This increases the operating costs of a Sewage treatment treatment plant . There are various types of foulants colloid al clays, flocculation floc s , biological bacteria , fungi , organic oils , polyelectrolyte s, humic s and scaling mineral precipitates . ref Baker, R.W. 2004 . Membrane Technology and Applications, England John Wiley & Sons Ltd ref Fouling can be divided into reversible and irreversible fouling based on the attachment strength of particles to the membrane surface. Reversible fouling can be removed by a strong shear force of backwashing . Formation of a strong matrix of fouling layer with the solute during a continuous filtration process will result in reversible fouling being transformed into an irreversible fouling layer. Irreversible fouling is the strong attachment of particles which cannot be removed by physical cleaning. ref Choi, H., Zhang, K., Dionysiou, D.D.,Oerther, D.B.& Sorial, G.A. 2005 Effect of permeate flux and tangential flow on membrane fouling for wastewater treatment. J. Separation and Purification Technology 45 68 78. ref Factors affecting membrane fouling Factors that affect membrane fouling Membrane properties such as pore size, hydrophobe hydrophobicity , pore size distribution and membrane material. Solution properties such as concentration, the nature of the components and particle size distribution. Operating conditions such as pH , temperature , flow rate and pressure. Measure of membrane fouling Flux and transmembrane pressure TMP are the best indicators of membrane fouling. Under constant flux operation, TMP ... more details
Cleanup date September 2007 Image L serine skeletal.png thumb serine Image L threonine skeletal.png thumb threonine Image Phosphate Group.PNG right thumb phosphate Serine threonine protein kinases EC number 2.7.11.1 phosphorylate the OH group of serine or threonine which have similar sidechains . At least 125 of the 500 human protein kinases are serine threonine kinases STK . ref name Capra Regulation Empty section date December 2010 Selectivity While serine threonine kinases all phosphorylate serine or threonine residues in their substrates, they select specific residues to phosphorylate on the basis of residues that flank the phosphoacceptor site, which together comprise the consensus sequence . Since the consensus sequence residues of the substrate to be phosphorylated make contact with the catalytic cleft of the kinase at several key amino acids usually through hydrophobe hydrophobic forces and ionic bond s , a kinase is usually not specific to a single substrate, but instead can phosphorylate a whole substrate family having common recognition sequences. While the catalytic domain of these kinases is Conserved sequence highly conserved , the sequence variation that is observed in the kinome the subset of genes in the genome that encode kinases provides for recognition of distinct substrates. Most kinases are inhibited by a pseudosubstrate that binds to the kinase like a real substrate but lacks the amino acid to be phosphorylated. When the pseudosubstrate is removed, the kinase can perform its normal function. EC numbers Many serine threonine protein kinases do not have their own individual EC number s and use 2.7.11.1 . These were formerly included in EC number 2.7.1.37 , which was a general EC number for any enzyme that phosphorylates proteins while converting ATP to ADP i.e., ATP protein phosphotransferases. Types Types include those acting directly as receptors Receptor protein serine threonine kinase and Intracellular signaling peptides and proteins . Of th ... more details
Poloxamers are nonionic triblock copolymers composed of a central hydrophobic chain of polypropylene glycol polyoxypropylene poly propylene oxide flanked by two hydrophilic chains of polyethylene glycol polyoxyethylene poly ethylene oxide . The word poloxamer was coined by the inventor, Irving Schmolka, who received the patent for these materials in 1973. ref cite patent US 3740421 ref Poloxamers are also known by the trade name Pluronics . ref cite web url http worldaccount.basf.com wa NAFTA en US Catalog ChemicalsNAFTA pi BASF Brand pluronic title BASF Product information the chemicals catalog Pluronics work BASF Corporation Website accessdate 2008 12 09 ref Because the lengths of the polymer blocks can be customized, many different poloxamers exist that have slightly different properties. For the generic term poloxamer , these copolymers are commonly named with the letter P for poloxamer followed by three digits, the first two digits x 100 give the approximate molecular mass of the polyoxypropylene core, and the last digit x 10 gives the percentage polyoxyethylene content e.g., P407 Poloxamer with a polyoxypropylene molecular mass of 4,000 g mol and a 70 polyoxyethylene content . For the Pluronic tradename, coding of these copolymers starts with a letter to define its physical form at room temperature L liquid, P paste, F flake solid followed by two or three digits, The first digit two digits in a three digit number in the numerical designation, multiplied by 300, indicates the approximate molecular weight of the hydrophobe and the last digit x 10 gives the percentage polyoxyethylene content e.g., L61 Pluronic with a polyoxypropylene molecular mass of 1,800 g mol and a 10 polyoxyethylene content . In the example given, poloxamer 181 P181 Pluronic L61. Uses of poloxamers Because of their amphiphilic structure, the polymers have surfactant properties that make them useful in industrial applications. Among other things, they can be used to increase the water solubil ... more details
refimprove date June 2008 Electrochemical gas sensors are gas detectors that measure the concentration of a target gas by Redox oxidizing or reducing the target gas at an electrode and measuring the resulting current. Construction The sensors contain two or three electrodes, occasionally four, in contact with an electrolyte . The electrodes are typically fabricated by fixing a high surface area precious metal on to the porous Hydrophobe hydrophobic membrane. The working electrode contacts both the electrolyte and the ambient air to be monitored usually via a porous membrane. The electrolyte most commonly used is a mineral acid , but organic electrolytes are also used for some sensors. The electrodes and housing are usually in a plastic housing which contains a gas entry hole for the gas and electrical contacts. Theory of operation The gas diffuses into the sensor, through the back of the porous membrane to the working electrode where it is oxidized or reduced. This Electrochemistry electrochemical reaction results in an electric current that passes through the external circuit. In addition to measuring, amplifying and performing other signal processing functions, the external circuit maintains the voltage across the sensor between the working and counter electrodes for a two electrode sensor or between the working and reference electrodes for a three electrode cell. At the counter electrode an equal and opposite reaction occurs, such that if the working electrode is an oxidation, then the counter electrode is a reduction. Diffusion controlled response The magnitude of the current is controlled by how much of the target gas is oxidized at the working electrode. Sensors are usually designed so that the gas supply is limited by diffusion and thus the output from the sensor is linear ly proportional to the gas concentration . This linear output is one of the advantages of electrochemical sensors over other sensor technologies, e.g. infrared , whose output must be linear ... more details
enzyme Name chymotrypsin EC number 3.4.21.1 CAS number 9004 07 3 IUBMB EC number 3 4 21 1 GO code 0004263 image ChymotrypsinA1.jpg width caption enzyme Name chymotrypsin C EC number 3.4.21.2 CAS number 9036 09 3 IUBMB EC number 3 4 21 2 GO code image width caption Chymotrypsin is a digestive enzyme that can perform proteolysis . ref name Wilcox 1970 cite journal author Wilcox PE year 1970 title Chymotrypsinogens chymotrypsins journal Methods in Enzymology volume 19 pages 64 108 doi 10.1016 0076 6879 70 19007 0 ref Chymotrypsin preferentially cleaves peptide amide bonds where the carboxyl side of the amide bond the P sub 1 sub position is a tyrosine , tryptophan , or phenylalanine . These amino acid s contain an aromatic ring in their substituent sidechain that fits into a hydrophobe hydrophobic pocket the S sub 1 sub position of the enzyme. The hydrophobic and shape complementarity between the peptide enzyme substrate substrate P sub 1 sub sidechain and the enzyme S sub 1 sub binding cavity accounts for the substrate specificity of this enzyme. ref name pmid3555886 cite journal author Appel W title Chymotrypsin molecular and catalytic properties journal Clin. Biochem. volume 19 issue 6 pages 317 22 year 1986 month December pmid 3555886 doi 10.1016 S0009 9120 86 80002 9 url issn ref ref name pmid4399049 cite journal author Berger A, Schechter I title Mapping the active site of papain with the aid of peptide substrates and inhibitors journal Philos. Trans. R. Soc. Lond., B, Biol. Sci. volume 257 issue 813 pages 249 64 year 1970 month February pmid 4399049 doi 10.1098 rstb.1970.0024 url issn ref Chymotrypsin also hydrolyzes other amide bonds in peptides at slower rates, particularly those containing leucine at the P sub 1 sub position. Activation of chymotrypsin Chymotrypsin is synthesized in the pancreas by protein biosynthesis as a wiktionary Precursor precursor called chymotrypsinogen that is enzymatically inactive. On cleavage by trypsin into two parts that are sti ... more details
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