(n.) The state, quality, or relation, of two or more isomeric substances.
Example Sentences:
(1) Structure assignment of the isomeric immonium ions 5 and 6, generated via FAB from N-isobutyl glycine and N-methyl valine, can be achieved by their collision induced dissociation characteristics.
(2) This is interpreted to mean that the release of fructose from the central complex is faster than the isomerization of the E-NADH complex.
(3) The optical and oxygen binding properties of the reconstituted myoglobins containing two isomeric monoformyl-monovinylhemins were found to be different.
(4) Line broadening detected in several of the high-field nuclear magnetic resonance spectra was attributed to cis-trans isomerization.
(5) Two new isomeric delta-lactones 2 and 3 have been isolated from the marine fungus Helicascus kanaloanus (ATCC 18591).
(6) Two isomeric hydrolysis products of this compound with only three 3(R)-hydroxymyristic acid moieties attached to the disaccharide-1-phosphate were also identified.
(7) Studies on the metabolism of nicotine by rabbit liver microsomal fractions in the presence of 0.01 M sodium cyanide have led to the characterization of two isomeric cyanonicotine compounds.
(8) Kinetic methods are outlined for the distinction between two pathways of substrate binding, which include an isomerization either of the free enzyme or of the enzyme-substrate complex.
(9) In the case of H101S, a mutant protein with measurable isomerizing activity, substrate binding with novel fluorescent properties was observed, possibly the bound pyranose form of xylose under steady-state conditions.
(10) There were consistent isomeric preferences for the R(-) configuration of both DA analogs in stimulating adenylate cyclase (D-1 sites) and in competing for high affinity binding of 3H-spiroperidol (D-2 sites) and of 3H-ADTN (DA agonist binding sites) in striatal tissue, with lesser isomeric differences in the limbic tissue.
(11) Oligosaccharides 3 and 4 and oligosaccharides 5 and 6 were isolated as unresolved isomeric mixtures in fractions B3a and B4a, respectively.
(12) Subsequent fractionation of the original compound into its two isomeric forms resulted in the identification of the isomer primarily responsible for this convulsive activity.
(13) However, the 1500 K simulation produced higher energy structures, even after minimization; in addition, this highest temperature run had many cis-trans peptide isomerizations.
(14) From model compound data, it is shown that the expected rate for isomerism is in satisfactory agreement with the rates actually observed for protein folding.
(15) Re-analysis of PCP and PCP-Na samples with high PCDD contents on a high-resolution glass capillary column showed the presence of 3 hexa- and the 2 heptachlorodibenzo-p-dioxins with nearly constant isomeric ratios.
(16) Such a genomic structure does not appear to have been reported amongst the herpesviruses--all the genomes that do not isomerize either have repeat structures only at the termini, or if present internally, have only direct repeats.
(17) The isomeric N,N-dimethyl-4,5-diphenyl-1H-pyrazole-1-propanamine was completely inactive in the primary antidepressant screens.
(18) Correspondingly, in the case of the histidine-peptides examined only mixtures of the cyclic isomeric compounds were isolated and structurally characterized by 1H-NMR analysis.
(19) In contrast to the biphasic unfolding of the wild-type nuclease, the unfolding of the mutant is represented by a single-phase reaction, indicating that the biphasic unfolding for the wild-type protein is caused by cis-trans isomerization about the prolyl peptide bond in the native state.
(20) In order to prepare a completely light-stable rhodopsin, we have synthesized an analog, II, of 11-cis retinal in which isomerization at the C11-C12 cis-double bond is blocked by formation of a cyclohexene ring from the C10 to C13-methyl.
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.