TERMIUM Plus^®

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Folding a polypeptide chain to a compact globular form will necessitate some way to change the direction of the polypeptide chain, as might, for example, be required to connect adjacent ends of the polypeptide chains in an antiparallel [beta]-sheet. A commonly observed and particularly efficient way to do this is by formation of a tight loop in which a residue's carbonyl group forms a hydrogen bond with the amide NH group of the residue three positions further along the polypeptide chain. The resulting so-called [beta]-bend reverses the direction of the polypeptide chain.  1, record 1, English, - beta%2Dbend

Record 1,  Textual support,  French

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Les retournements de la chaîne polypeptidique s'effectuent selon des structures déterminées appelées virages [bêta]. [...] Un virage [bêta] comporte un segment de la chaîne polypeptidique de quatre acides aminés consécutifs [...], se retournant de 180°, et tels que la distance entre [le premier et le quatrième] soit inférieure à 7 A et que ce segment ne forme pas d'hélice. Il existe différents types de virages [bêta] selon la valeur des angles dihédraux.  2, record 1, French, - virage%20b%C3%AAta

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Record 2,  Textual support,  English

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The complex structural arrangement of some protein molecules, such as keratin, in which the single polypeptide chains of proteins spiral right-handedly to form helices. Each NH group is connected to a CO group by a hydrogen bond at a distance equivalent to 3 amino acid residues; the helix makes a complete turn for each 3. 6 residues.  2, record 2, English, - alpha%20helix

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One of the most commonly observed protein secondary structures is the [alpha] helix .... Several researchers have ... designed totally synthetic proteins based on natural folding patterns -- the alpha helix and the beta pleated sheet.  3, record 2, English, - alpha%20helix

Record 2,  Textual support,  French

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Structure hélicoïdale d'enroulement d'une chaîne peptidique, en fonction des contraintes imposées par les liaisons peptidiques et leurs dimensions spécifiques. Dans cette structure, existent environ 3,6 résidus d'aminoacides par tour de spire. Les chaînes latérales R des aminoacides se placent à l'extérieur de l'hélice formée par le squelette peptidique. Dans cette structure, l'unité périodique, un simple tour de spire de l'hélice, s'étend sur environ 0,54 mm le long de l'axe. La disposition des chaînes peptidiques sous forme d'hélice est favorisée par rapport aux autres structures hélicoïdales ou aux autres enroulements possibles, car elle permet l'établissement de liaisons par ponts hydrogène entre les spires successives de l'hélice.  2, record 2, French, - h%C3%A9lice

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La structure secondaire de l'alcool déhydrogénase est constituée de nombreuses hélices alpha et feuillets bêta reliés entre eux par de courts segments apparemment sans structure secondaire.  3, record 2, French, - h%C3%A9lice

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Record 3,  Textual support,  English

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Surface cracking due to oxidation and shrinkage stresses, which shows as repetitive mounding of an asphalt surface, resembling the hide of an alligator.  2, record 3, English, - alligatoring

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Although heat is also a factor in the deterioration of asphalt on a roof, the real source of decay is the energy carried by the ultra-violet(UV) light of the sun, combined with the ready supply of oxygen in ozone. The "links" in asphalt molecular chains are hydrogen. The molecular bond is overcome by the strong attraction of the oxygen, which pulls the hydrogen away from the asphalt molecules. This process is called photo-oxidation, and these breaks in the "aliphatic" chain results in the shrinkage cracking common to asphalt. This phenomenon is commonly called "alligatoring" in roofing parlance, a term which describes the similarity of aged asphalt surfaces to an alligator's back.  3, record 3, English, - alligatoring

Record 3,  Textual support,  French

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Durcissement et rétrécissement causés par l'oxydation des enduits bitumineux exposés, qui produisent de petits monticules entre des fissures profondes qui donnent l'aspect d'une peau de crocodile.  2, record 3, French, - crocodilage

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Record 4,  Textual support,  English

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To remove a methyl group from (a chemical compound).  3, record 4, English, - desmethylate

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Three active demethylation mechanisms have been proposed.... The first mechanism is direct replacement of the methyl moiety by a hydrogen atom. The human MBD2(Methylated DNA binding protein 2) was reported to demethylate DNA by this mechanism, i. e., the thermodynamically unfavorable breakage of the carbon-carbon bond that links the pyrimidine to its methyl group.  4, record 4, English, - desmethylate

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The enzymes that actively demethylate DNA include 5-methylcytosine glycosylase, which removes the methylated cytosine from DNA, leaving the deoxyribose intact ...  5, record 4, English, - desmethylate

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desmethylate: form recommended by the IUPAC (International Union of Pure and Applied Chemistry).  1, record 4, English, - desmethylate

Record 4,  Textual support,  French

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Action de provoquer une déméthylation, c'est-à-dire de détacher, de retirer un groupement méthyle (-CH₃) d'un composé, d'une cellule.  3, record 4, French, - desm%C3%A9thyler

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Méthylation et déméthylation des pectines. Des PMT (pectine méthyl transférases) peuvent méthyler des pectines acides au cours du transfert golgien. Des PME (pectine méthyl estérases) secrétées par la voie golgienne peuvent déméthyler les pectines méthylées et les rendre acides dans la paroi elle même.  4, record 4, French, - desm%C3%A9thyler

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La découverte d'activités capables de déméthyler les séquences mCG de l'ADN ouvre un nouveau chapitre des connaissances sur la régulation des gènes et laisse entrevoir d'importantes applications thérapeutiques et biotechnologiques.  5, record 4, French, - desm%C3%A9thyler

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Étude de la capacité d'un certain nombre de bactéries aérobies et anaérobies de N-déméthyler l'imipramine (I) en désipramine (II).  1, record 4, French, - desm%C3%A9thyler

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desméthyler : forme recommandée par l'UICPA (Union internationale de chimie pure et appliquée).  1, record 4, French, - desm%C3%A9thyler

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Record 5,  Textual support,  English

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Weak bond, primarily electrostatic, between an electronegative atom within a given molecule and a hydrogen atom attached to another electronegative atom.  3, record 5, English, - hydrogen%20bond

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The intermolecular attractive forces binding antigen to antibody. ... Hydrogen bonding results from the formation of hydrogen bridges between appropriate atoms.  4, record 5, English, - hydrogen%20bond

Record 5,  Textual support,  French

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Type de liaison moléculaire où l'hydrogène établit un pont entre deux atomes fortement électronégatifs (azote, oxygène). Dans les macromolécules, elle assure le maintien de la structure. Ce type de liaison se répète un grand nombre de fois tout le long de la molécule concernée.  3, record 5, French, - liaison%20hydrog%C3%A8ne

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Les forces unissant antigène et anticorps sont de quatre types. [...] Les liaisons hydrogène sont des liaisons de faible énergie (0, 5 à 2 kcal/mole) entre atomes électropositifs (hydrogène) et atomes électronégatifs (oxygène ou azote). La stabilité de ces liaisons dépend de la présence de molécules d'eau. Elle augmente quand la température diminue.  4, record 5, French, - liaison%20hydrog%C3%A8ne

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Record 6,  Textual support,  English

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Molecules are usually forms into aggregates called clusters by the intermolecular force, and their physicochemical behavior is sometimes different from that of bulks. Clusters are classified into the van der Waals cluster, covalent cluster, hydrogen bond cluster, metal cluster, ionic bond cluster, and so on. These types of cluster are expected to be applied to surface modification and so on.  2, record 6, English, - van%20der%20Waals%20cluster

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This new model has been tested by comparing its predictions with the results of Molecular Dynamics (MD) simulations for the unimolecular evaporation of two types of van der Waals clusters: the aniline-(argon)n molecular clusters and the neat argon Arn clusters.  3, record 6, English, - van%20der%20Waals%20cluster

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cluster: An aggregate of molecules, consisting of two to several hundreds of molecules.  2, record 6, English, - van%20der%20Waals%20cluster

Record 6,  Textual support,  French

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Isomérisation et évaporation dans des agrégats de van der Waals. Résumé : Au cours de ce séminaire, nous présenterons les derniers résultats obtenus sur les dynamiques d'isomérisation et d'évaporation dans les agrégats de van der Waals aniline-Ar_n et benzene-Ar_n (n=7-25).  1, record 6, French, - agr%C3%A9gat%20de%20van%20der%20Waals

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Record 7,  Textual support,  English

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... the existence of two or more chemical compounds that are capable of facile interconversion, in many cases merely exchanging a hydrogen atom between two other atoms, to either of which it forms a covalent bond. Unlike other classes of isomers, tautomeric compounds exist in mobile equilibrium with each other, so that attempts to prepare the separate substances usually result in the formation of a mixture that shows all the chemical and physical properties to be expected on the basis of the structures of the components.  2, record 7, English, - tautomerism

Record 7,  Textual support,  French

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Cas particulier de transposition intramoléculaire, résultant de réarrangements rapides et réversibles (isomérie dynamique). Plus précisément, on appelle ainsi la transformation d'un corps chimique en un isomère différent du premier par l'emplacement d'un atome et par la disposition des liaisons, cette transformation aboutissant à un équilibre.  3, record 7, French, - tautom%C3%A9rie

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Le sens du terme tautomérie n'est pas exactement le même pour tous les chimistes. Les uns l'emploient comme synonyme de desmotropie, les autres dans un sens plus général (...)  2, record 7, French, - tautom%C3%A9rie

Record 7,  Textual support,  Spanish

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Isomería originada por el cambio de posición de uno o más átomos en una molécula, con modificación simultánea de la distribución electrónica.  3, record 7, Spanish, - tautomer%C3%ADa

Record 8,  Textual support,  English

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An analytical technique analogous to x-ray diffraction in which an incident beam of neutrons is scattered by the atoms of a crystal.  2, record 8, English, - neutron%20diffraction

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Because elements that are close to each other in the Periodic Table differ considerably in their neutron-scattering ability, neutron diffraction is capable of distinguishing between them. For example, carbon nitrogen, and oxygen atoms can be readily identified by neutron diffraction, where as they appear almost identical by the x-ray method. More accurate determination of the bond lengths of light atoms and distribution of molecular bonding electrons is also possible. Details of molecular structure that can only be inferred by other techniques can often be observed directly by neutron diffraction. Investigations using this method include hydrogen bonding, so-called metal cluster compounds(C. H. M relationships) and electronic charge distributions.  2, record 8, English, - neutron%20diffraction

Record 8,  Textual support,  French

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En réalité la seule méthode capable de déceler la structure atomique de la plupart des macromolécules est la diffraction des rayons X par des cristaux. [...] La diffraction neutronique est surtout utilisée pour placer les atomes d'hydrogène, trop légers pour être normalement détectés par diffraction des rayons X, dans des modèles atomiques obtenus par cette dernière méthode.  4, record 8, French, - diffraction%20neutronique

Record 8,  Textual support,  Spanish

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Difracción de los neutrones térmicos que por tener una longitud de onda asociada aproximadamente igual a la distancia entre los átomos de los cristales, son difractados por éstos.  1, record 8, Spanish, - difracci%C3%B3n%20de%20neutrones

Record 9,  Textual support,  English

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cyanides : Salts and C-organyl derivatives of hydrogen cyanide, HC[ triple bond] N.  2, record 9, English, - cyanide

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[For example:] CH₃C[triple bond]N methyl cyanide (acetonitrile), NaCN sodium cyanide, PhC([double bond]O)CN benzoyl cyanide.  2, record 9, English, - cyanide

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The first type of effluent contains mineral, acid, basic or toxic pollutants (various cyanides, hexavalent chrome, fluorides, heavy metals) and small quantities of organic pollutants (surfactants).  3, record 9, English, - cyanide

Record 9,  Textual support,  French

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Sel et dérivé C-organylé de l'acide cyanhydrique, HC[liaison triple]N.  2, record 9, French, - cyanure

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Par exemple : CH₃-C[liaison triple]N cyanure de méthyle (acétonitrile), NaC[liaison triple]N cyanure de sodium, PhC([liaison double]O)C[liaison triple]N cyanure de benzoyle.  2, record 9, French, - cyanure

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Les premiers effluents comportent des polluants minéraux, acides, basiques ou toxiques (cyanures divers, chrome hexavalent, fluorures, métaux lourds) et des polluants organiques (tensio-actifs) en faible quantité.  3, record 9, French, - cyanure

Record 9,  Textual support,  Spanish

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Sal del ácido cianhídrico. En general, son grupos muy tóxicos.  2, record 9, Spanish, - cianuro

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Gaseous or liquid compounds of silicon and hydrogen... analogous to alkanes or saturated hydrocarbons.... Organo-functional silanes are noted for their ability to bond organic polymer systems to inorganic substrates.  2, record 10, English, - silane

Record 10,  Textual support,  French

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Nom générique des composés hydrogénés du silicium, qui présentent des analogies avec les hydrocarbures.  2, record 10, French, - silane

Record 10,  Textual support,  Spanish

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Compuestos con gran habilidad para enlazar sistemas de polímeros orgánicos a sustratos inorgánicos. Tóxicos e inflamables.  1, record 10, Spanish, - silano

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With the halogens, fluorine, chlorine, bromine, and iodine, hydrogen forms hydrides containing 1 atom of hydrogen per atom of halogen. These compounds are usually referred to as hydrogen halides, for example, hydrogen chloride, HCl, or as hydrohalic acids, for example hydrochloric acid. The hydrogen halides are gases at room temperature.  2, record 11, English, - hydrogen%20halide

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Electrochemical conversion of anhydrous hydrogen halide to halogen gas using an ionically conducting membrane.  3, record 11, English, - hydrogen%20halide

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hydrohalic acid: An aqueous solution of a hydrogen halide.  4, record 11, English, - hydrogen%20halide

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Reactions of alkenes and alkynes(at the double bond site). A. Addition of halides(chlorine, bromine, iodine)--yields dihalogen substituted alkane. B. Addition of hydrogen halides(HCl, HBr, HI)--yields monohalogen alkanes CH₃CH₂-Cl.  5, record 11, English, - hydrogen%20halide

Record 11,  Textual support,  French

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Les halogénures d'hydrogène sont des composés des halogènes avec l'hydrogène. Leurs solutions aqueuses sont acides et portent alors, et alors seulement, le nom d'hydracide (acide fluorhydrique, acide chlorhydrique, acide bromhydrique, acide iodhydrique). Les sels sont les halogénures métalliques [...]  2, record 11, French, - halog%C3%A9nure%20d%27hydrog%C3%A8ne

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L'hydrogène peut [...] donner lieu à une réaction explosive avec certains halogènes (dont le chlore), laquelle produit un halogénure d'hydrogène.  3, record 11, French, - halog%C3%A9nure%20d%27hydrog%C3%A8ne

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Record 12,  Textual support,  English

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The hydrogen ion(a positively charged hydrogen atom) is acidic and, when released, can cause the break of the covalent bond in the cellulose chain. A continuation of that process produces acidic degradation. Such impurities in paper as lignin, hemicellulose, hydrolyzed cellulose, and others will oxidize and produce acidic degrading of paper.  1, record 12, English, - hydrolyzed%20cellulose

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Record 12,  Textual support,  Spanish

Record 13,  Textual support,  English

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To subject to hydrolysis.  3, record 13, English, - hydrolyze

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Enzymes sometimes form transient covalent bonds with their substrates. In one example, a carboxyl group in a polypeptide chain forms a covalent bond at an activated serine residue of a protease as the backbone chain is broken. When the unbound portion of the polypeptide chain has diffused away, a second step occurs in which a water molecule hydrolyzes the newly formed covalent bond, thereby releasing the portion of the polypeptide bound to the enzyme surface and restoring a hydrogen atom to the serine.  4, record 13, English, - hydrolyze

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See "hydrolysis".  5, record 13, English, - hydrolyze

Record 13,  Textual support,  French

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Soumettre à l'hydrolyse.  2, record 13, French, - hydrolyser

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Des développements liés à la mise en évidence récente d'enzymes capables d'hydrolyser spécifiquement certains composés organophosphorés [...] peuvent actuellement être envisagés. Ces enzymes devraient permettre d'une part de doser spécifiquement l'un ou l'autre des composés organophosphorés présents dans un échantillon, et d'autre part de détoxifier un milieu contaminé par l'un de ces composés.  3, record 13, French, - hydrolyser

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Record 14,  Textual support,  English

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A type of bond formed when a hydrogen atom bonded to atom A in one molecule makes an additional bond to atom B either in the same or another molecule.  2, record 14, English, - hydrogen%20bond

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hydrogen-containing substances... can only be brought logically into the Lewis Scheme by appealing to the fact that the reaction between a proton acid, which may be designated as XH, and a base, denoted by B, passes through an intermediate hydrogen-bonded state X-H... B(in which the dotted line indicates a hydrogen-bond, a relatively weak secondary attractive force).  3, record 14, English, - hydrogen%20bond

Record 14,  Textual support,  French

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Force d'origine électrostatique intermédiaire entre la liaison ionique et la force Van der Waals, que l'on rencontre chez les corps à constante diélectrique élevée H₂O, HCN, H₂O₂, HF, etc., et responsable d'un grand nombre de propriétés physiques et chimiques.  2, record 14, French, - liaison%20hydrog%C3%A8ne

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[...] au cours de la neutralisation, il se forme d'abord un composé moléculaire entre l'acide et la base (l'un des deux partenaires pouvant être une molécule de solvant). Ce composé résulte en fait de l'établissement d'une liaison hydrogène entre l'atome H de l'acide et l'atome donneur d'électrons de la base; [...].  1, record 14, French, - liaison%20hydrog%C3%A8ne

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Record 15,  Textual support,  English

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Association between a base and the conjugate acid of a different base through a hydrogen bond...  1, record 15, English, - heteroconjugation

Record 15,  Textual support,  French

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Association, par liaison hydrogène, d'une base et de l'acide conjugué d'une autre base [...]  1, record 15, French, - h%C3%A9t%C3%A9roconjugaison

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Record 16,  Textual support,  English

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Association between a base and its conjugate acid through a hydrogen bond...  1, record 16, English, - homoconjugaison

Record 16,  Textual support,  French

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Association par liaison hydrogène d'une base et de son acide conjugué [...]  1, record 16, French, - homoconjugaison

Record 16,  Textual support,  Spanish