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27-478: Two structural features distinguish fucose from other six-carbon sugars present in mammals: the lack of a hydroxyl group on the carbon at the 6-position (C-6) (thereby making it a deoxy sugar ) and the L -configuration . It is equivalent to 6-deoxy- L - galactose . In the fucose-containing glycan structures, fucosylated glycans, fucose can exist as a terminal modification or serve as an attachment point for adding other sugars. In human N -linked glycans, fucose

54-439: A peptide or protein chain. It can also be called a eupeptide bond to distinguish it from an isopeptide bond , which is another type of amide bond between two amino acids. When two amino acids form a dipeptide through a peptide bond , it is a type of condensation reaction . In this kind of condensation, two amino acids approach each other, with the non- side chain (C1) carboxylic acid moiety of one coming near

81-447: A peptide bond is 190–230 nm, which makes it particularly susceptible to UV radiation. Significant delocalisation of the lone pair of electrons on the nitrogen atom gives the group a partial double-bond character. The partial double bond renders the amide group planar , occurring in either the cis or trans isomers . In the unfolded state of proteins, the peptide groups are free to isomerize and adopt both isomers; however, in

108-662: A rock sample at a wavelength of 2.85 micrometers indicated localized water/hydroxyl concentrations as high as 180 parts per million. The Venus Express orbiter collected Venus science data from April 2006 until December 2014. In 2008, Piccioni, et al. reported measurements of night-side airglow emission in the atmosphere of Venus made with the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on Venus Express. They attributed emission bands in wavelength ranges of 1.40 - 1.49 micrometers and 2.6 - 3.14 micrometers to vibrational transitions of OH. This

135-498: A wavelength of 6.1 micrometers that are present in water but not in hydroxyl. The abundance of water on the Moon's surface was inferred to be equivalent to the contents of a 12-ounce bottle of water per cubic meter of lunar soil. The Chang'e 5 probe, which landed on the Moon on 1 December 2020, carried a mineralogical spectrometer that could measure infrared reflectance spectra of lunar rock and regolith. The reflectance spectrum of

162-442: Is a functional group with the chemical formula −OH and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry , alcohols and carboxylic acids contain one or more hydroxy groups. Both the negatively charged anion HO , called hydroxide , and the neutral radical HO· , known as the hydroxyl radical , consist of an unbonded hydroxy group. According to IUPAC definitions,

189-511: Is extremely slow, with the half life at 25 °C of between 350 and 600 years per bond. In living organisms, the process is normally catalyzed by enzymes known as peptidases or proteases , although there are reports of peptide bond hydrolysis caused by conformational strain as the peptide/protein folds into the native structure. This non-enzymatic process is thus not accelerated by transition state stabilization, but rather by ground-state destabilization. The wavelength of absorption for

216-481: Is illuminated by diffuse light, called airglow , that is produced by radiative transitions of atoms and molecules. Among the most intense such features observed in the Earth's night sky is a group of infrared transitions at wavelengths between 700 nanometers and 900 nanometers. In 1950, Aden Meinel showed that these were transitions of the hydroxyl molecule, OH. In 2009, India's Chandrayaan-1 satellite and

243-516: Is most commonly linked α-1,6 to the reducing terminal β- N -acetylglucosamine . However, fucose at the non-reducing termini linked α-1,2 to galactose forms the H antigen , the substructure of the A and B blood group antigens. Fucose is released from fucose-containing polymers by an enzyme called α-fucosidase found in lysosomes . L -Fucose has several potential applications in cosmetics, pharmaceuticals, and dietary supplements Fucosylation of antibodies has been established to reduce binding to

270-471: The Fc receptor of Natural Killer cells and thereby reduce antibody-dependent cellular cytotoxicity . Therefore, afucosylated monoclonal antibodies have been designed to recruit the immune system to cancers cells have been manufactured in cell lines deficient in the enzyme for core fucosylation ( FUT8 ), thereby enhancing the in vivo cell killing. Hydroxyl In chemistry , a hydroxy or hydroxyl group

297-622: The LCROSS probe revealed an ultraviolet emission spectrum consistent with hydroxyl presence. On 26 October 2020, NASA reported definitive evidence of water on the sunlit surface of the Moon, in the vicinity of the crater Clavius (crater) , obtained by the Stratospheric Observatory for Infrared Astronomy (SOFIA) . The SOFIA Faint Object infrared Camera for the SOFIA Telescope (FORCAST) detected emission bands at

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324-672: The National Aeronautics and Space Administration (NASA) Cassini spacecraft and Deep Impact probe each detected evidence of water by evidence of hydroxyl fragments on the Moon . As reported by Richard Kerr, "A spectrometer [the Moon Mineralogy Mapper, also known as "M3"] detected an infrared absorption at a wavelength of 3.0 micrometers that only water or hydroxyl—a hydrogen and an oxygen bound together—could have created." NASA also reported in 2009 that

351-473: The aldehyde end of one sugar . The creation of a peptide bond to link two amino acids to make a protein removes the −OH from the carboxy group of one amino acid. Hydroxyl radicals are highly reactive and undergo chemical reactions that make them short-lived. When biological systems are exposed to hydroxyl radicals, they can cause damage to cells, including those in humans, where they can react with DNA , lipids , and proteins . The Earth's night sky

378-775: The amino group of the other amino acid molecule, causing the release of a molecule of water (H 2 O), hence the process is a dehydration synthesis reaction. The formation of the peptide bond consumes energy, which, in organisms, is derived from ATP . Peptides and proteins are chains of amino acids held together by peptide bonds (and sometimes by a few isopeptide bonds ). Organisms use enzymes to produce nonribosomal peptides , and ribosomes to produce proteins via reactions that differ in details from dehydration synthesis. Some peptides, like alpha-amanitin , are called ribosomal peptides as they are made by ribosomes, but many are nonribosomal peptides as they are synthesized by specialized enzymes rather than ribosomes. For example,

405-475: The activation energy have been observed in peptidyl prolyl isomerases (PPIases), which are naturally occurring enzymes that catalyze the cis-trans isomerization of X-Pro peptide bonds. Conformational protein folding is usually much faster (typically 10–100 ms) than cis-trans isomerization (10–100 s). A nonnative isomer of some peptide groups can disrupt the conformational folding significantly, either slowing it or preventing it from even occurring until

432-465: The atmosphere of exoplanet WASP-76b was subsequently found. Both WASP-33b and WASP-76b are ultra-hot Jupiters and it is likely that any water in their atmospheres is present as dissociated ions. Peptide bond In organic chemistry , a peptide bond is an amide type of covalent chemical bond linking two consecutive alpha-amino acids from C1 ( carbon number one) of one alpha-amino acid and N2 ( nitrogen number two) of another, along

459-412: The chemical compound produced on the largest scale industrially. Hydroxy groups participate in the dehydration reactions that link simple biological molecules into long chains. The joining of a fatty acid to glycerol to form a triacylglycerol removes the −OH from the carboxy end of the fatty acid. The joining of two aldehyde sugars to form a disaccharide removes the −OH from the carboxy group at

486-466: The electrostatic attraction between molecules and thus to higher boiling and melting points than found for compounds that lack this functional group . Organic compounds, which are often poorly soluble in water, become water-soluble when they contain two or more hydroxy groups, as illustrated by sugars and amino acid . The hydroxy group is pervasive in chemistry and biochemistry. Many inorganic compounds contain hydroxyl groups, including sulfuric acid ,

513-452: The figure below. The dihedral angle associated with the peptide group (defined by the four atoms C –C'–N–C ) is denoted ω {\displaystyle \omega } ; ω = 0 ∘ {\displaystyle \omega =0^{\circ }} for the cis isomer ( synperiplanar conformation), and ω = 180 ∘ {\displaystyle \omega =180^{\circ }} for

540-411: The folded state, only a single isomer is adopted at each position (with rare exceptions). The trans form is preferred overwhelmingly in most peptide bonds (roughly 1000:1 ratio in trans:cis populations). However, X-Pro peptide groups tend to have a roughly 30:1 ratio, presumably because the symmetry between the C and C atoms of proline makes the cis and trans isomers nearly equal in energy, as shown in

567-448: The native isomer is reached. However, not all peptide groups have the same effect on folding; nonnative isomers of other peptide groups may not affect folding at all. Due to its resonance stabilization, the peptide bond is relatively unreactive under physiological conditions, even less than similar compounds such as esters . Nevertheless, peptide bonds can undergo chemical reactions, usually through an attack of an electronegative atom on

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594-437: The non-side chain (N2) amino moiety of the other. One loses a hydrogen and oxygen from its carboxyl group (COOH) and the other loses a hydrogen from its amino group (NH 2 ). This reaction produces a molecule of water (H 2 O) and two amino acids joined by a peptide bond (−CO−NH−). The two joined amino acids are called a dipeptide. The amide bond is synthesized when the carboxyl group of one amino acid molecule reacts with

621-417: The partial double bond be broken, so that the activation energy is roughly 80 kJ/mol (20 kcal/mol). However, the activation energy can be lowered (and the isomerization catalyzed ) by changes that favor the single-bonded form, such as placing the peptide group in a hydrophobic environment or donating a hydrogen bond to the nitrogen atom of an X-Pro peptide group. Both of these mechanisms for lowering

648-434: The term hydroxyl refers to the hydroxyl radical ( ·OH ) only, while the functional group −OH is called a hydroxy group . Water, alcohols, carboxylic acids , and many other hydroxy-containing compounds can be readily deprotonated due to a large difference between the electronegativity of oxygen (3.5) and that of hydrogen (2.1). Hydroxy-containing compounds engage in intermolecular hydrogen bonding increasing

675-422: The trans isomer ( antiperiplanar conformation). Amide groups can isomerize about the C'–N bond between the cis and trans forms, albeit slowly ( τ ∼ 20 {\displaystyle \tau \sim 20}  seconds at room temperature). The transition states ω = ± 90 ∘ {\displaystyle \omega =\pm 90^{\circ }} requires that

702-440: The tripeptide glutathione is synthesized in two steps from free amino acids , by two enzymes : glutamate–cysteine ligase (forms an isopeptide bond , which is not a peptide bond) and glutathione synthetase (forms a peptide bond). A peptide bond can be broken by hydrolysis (the addition of water). The hydrolysis of peptide bonds in water releases 8–16  kJ / mol (2–4  kcal / mol ) of Gibbs energy . This process

729-550: Was the first evidence for OH in the atmosphere of any planet other than Earth's. In 2013, OH near-infrared spectra were observed in the night glow in the polar winter atmosphere of Mars by use of the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). In 2021, evidence for OH in the dayside atmosphere of the exoplanet WASP-33b was found in its emission spectrum at wavelengths between 1 and 2 micrometers. Evidence for OH in

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