(n.) A body or compound which is isomeric with another body or compound; a member of an isomeric series.
Example Sentences:
(1) An unsaturated fatty acid auxotroph of Escherichia coli was grown with a series of cis-octadecenoate isomers in which the location of the double bond varied from positions 3 to 17.
(2) Fluorination with [18F]acetylhypofluorite yields 6-[18F]fluoro-L-dopa with 95% radiochemical purity; fluorination of the same substrate with [18F]F2 yields a mixture of all three structural isomers in a ratio of 70:16:14 for 6-, 5-, and 2-fluoro compounds.
(3) The cis isomer was retained longer in liver, particularly in mitochondria, but had low retention in that portion of the endoplasmic reticulum isolated as the rough membrane fraction.
(4) The purity and configuration of each isomer of the free acid and N-chloroacetylated derivative were ascertained by: (a) paper chromatography in five solvent systems, (b) elemental analysis, (c) Van Slyke nitrous acid determination of alpha-carbonyl carbon, and (d) Van Slyke ninhydrin determination of alpha-carbonyl carbon, and (e) optical rotation.
(5) The stronger negative potentials may weaken electrostatic receptor interactions and, thereby, cause the trans(E)-isomers to be less active than cis(Z)-isomers.
(6) The identity of each of the three forms was determined by carboxymethylation of the free cysteines in each isomer with [3H]iodoacetic acid followed by determination of the labelled cysteines by tryptic peptide mapping.
(7) In contrast to the enantiomeric discrimination observed with racemic amine, the individual isomers were metabolized at approximately the same rate.
(8) To further assess different binding behavior of these two isomers, association rate was measured.
(9) None of the 3 beta- or 5 beta-isomers had any effect.
(10) Isomers and epimers of glucose influence insulin and cAMP in a parallel fashion as do sulfonylurea compounds (tolbutamide and glibenclamide).
(11) Bioaccumulation experiments were performed on the hexachlorocyclohexane isomers alpha-HCH, beta-HCH, gamma-HCH and delta-HCH, testing them simultaneously.
(12) Although serum total LDH activity was not altered, the LD5 isoenzyme was proportionately higher in the HCH isomers treated animals.
(13) Racemic verapamil and the L- and D-isomer increased cellular vincristine accumulation to the same extent.
(14) The hypothesis that opiate agonism requires an N substituent in the axial position does not appear to be consistent with the increased potency of beta isomers in which axial N substituents are thermodynamically more unstable.
(15) In the case of adducts with the diol-epoxides of benzo[c]phenanthrene, the energetically most favored structures are isomers with significant biological activity.
(16) Liver regeneration was stimulated in male rats with two-thirds of the liver removed by feeding a basal diet supplemented with acetaminophen (0.35-1.5%; weight basis), 2-acetamidophenol (1.0%) and acetophenetidin (1.0%) over a period of 10 days po, but was in the control range with the m-isomer, 3-acetamidophenol (1.0%), N-butyryl-p-aminophenol (1.0%), o-, m- and p-aminophenols (0.50%) and 4-acetamidothiophenol.
(17) However, exposure of the cells to either of the two isomers of azoxy-procarbazine led to significant DNA damage and cytotoxicity.
(18) 1"-Oxobufuralol (3) was reduced with a complex of (2S)-(-)-2-amino-3-methyl-1,1-diphenylbutan-1-ol and borane, yielding 2, which had a 95:5 ratio of the possible 1"R and 1"S isomers as determined by HPLC.
(19) As the two signals had the same intensities, it was suggested that equivalent amounts of cis and trans isomers of the alkenylmether were formed.
(20) The most important recent work has concerned the different anticoagulant potencies and metabolic pathways of the optical isomers of some of these drugs.
Tautomerism
Definition:
(n.) The condition, quality, or relation of metameric substances, or their respective derivatives, which are more or less interchangeable, according as one form or the other is the more stable. It is a special case of metamerism; thus, the lactam and the lactim compounds exhibit tautomerism.
Example Sentences:
(1) The coupled dienone-phenol re-arrangement and keto-enol tautomerism of this quinone methide produce the observed 3,4-dihydroxybenzaldehyde.
(2) On the other hand, results indicate that the protonation of formycin and its derivatives at the N1 atom leads to a change in their tautomeric preference from N7-H to N8-H.
(3) The inhibitor trapping system, however, prevents the inactivation of succinate dehydrogenase under the conditions when the rate of tautomeric oxaloacetate enol in equilibrium oxaloacetate ketone interconversion is high.
(4) In contrast, equilibria of ring chain tautomerism and covalent hydration of aldoses are almost completely insensitive to the polarity of their surroundings.
(5) The importance of both tautomerism and protonation reactions in the mechanism of action of adenosine deaminase is studied by means of a quantitative structure activity relationships strategy.
(6) The possibility that this product is an equilibrium mixture with the tautomeric 4-hydroxycyclophosphamide has not been as yet defintely ruled out.
(7) In addition to being a possible mechanism for alteration of hydrogen bonding in oxidized DNA, this type of interaction gives a better understanding into N7-N9 tautomerism of adenine.
(8) The product 3-fluorooxalacetate is thus released from phosphoenolpyruvate carboxykinase as the keto form and is reduced more rapidly by reduced nicotinamide adenine dinucleotide with malate dehydrogenase than by the occurrence of tautomerization.
(9) These results strongly suggest that the anomeric, epimeric, and tautomeric form of the sugar phosphate substrates favored by both enzymes is the beta-D-fructofuranose form.
(10) Tautomerization of DOPA quinone to dehydroDOPA may thus be a factor in the sclerotization of natural structures incorporating DOPA containing proteins.
(11) For the complex formed between [5,5-2H,5-13C]ALA and methyl methanethiosulfonate (MMTS) modified PBG synthase, which does not catalyze PBG formation but can form a Schiff base adduct, the chemical shift of 44.2 ppm (line width 92 Hz) identifies an imine structure as the predominant tautomeric form of the Schiff base.
(12) delta 5-3-Ketosteroid isomerase (EC 5.3.3.1) catalyzes the isomerization of delta 5-3-ketosteroids to delta 4-3-ketosteroids by a conservative tautomeric transfer of the 4 beta-proton to the 6 beta-position with Tyr-14 as a general acid and Asp-38 as a general base [Kuliopulos, A., Mildvan, A. S., Shortle, D., & Talalay, P. (1989) Biochemistry 28, 149-159].
(13) The results are consistent with evidence for the formation of the first tetrahydropterin intermediate by a tautomerization without any requirement for NADPH.
(14) Its function is probably to maintain the orientation and tautomeric state of the imidazole ring of histidine-159.
(15) This suggests that a stable AP:C base mispair via two hydrogen bonds can be formed with the imino tautomer of C. These results stress the importance of the imino form of C in AP-induced mutagenesis and support the 'trigger mechanism', in which formation of one hydrogen bond between AP and C is considered to stimulate the tautomeric shift of AP or C. The calculated relative stabilities of various base pairs and mispairs were in good agreement with experimental findings.
(16) Whereas O6-MeGua did not form hydrogen bonds with cytosine (via usual, wobble, or unusual tautomeric structures), it did form a 1:1 hydrogen-bonded complex with protonated cytosine.
(17) Amide-imide tautomerism enables a cleanup of the extract.
(18) Ultraviolet and infrared spectrophotometric techniques have been utilized to demonstrate that the monoanionic form of 2-thiouracil in aqueous medium consists of an equilibrium mixture of two tautomeric monoanions, one due to dissociation of the N1 proton, the other to dissociation of the N3 proton, in the approximate ratio 1:1.
(19) Combined use of mass spectroscopy and 1H- and 13C-NMR spectroscopy established that it is the 4,8-anhydro derivative of N-acetylneuraminic acid and that in solutions it exists in two tautomeric forms.
(20) As a result of a concerted proton (tautomeric) shift in the linked residues of the hydrogen-bond chain, which includes the bound molecule, a charge separation occurs.