Tetramethylpiperidine-1-oxyl Research Articles

Novel assay for measuring serum conjugated bilirubin and its clinical relevance

We have developed a new enzymatic assay for the determination of conjugated bilirubin (Bc) using stable liquid reagents. In this assay, only Bc is selectively oxidized by bilirubin oxidase at pH 5.0 in the presence of nitrilotris (methylenephosphonic acid) trisodium salt, ethylenediaminetetraacetic acid disodium manganese (II) salt, and 4-hydroxy-2,2,6,6,-tetramethylpiperidine 1-oxyl. Bc is quantitatively determined from a decrease in the absorbance at 450 nm caused by Bc oxidization. The reagent solutions of the assay were developed so that they could be stably stored for one year together with bilirubin oxidase, in order to eliminate the need to prepare working solutions every time they are required. The assay has good reactivity, differentiability, measurability, and precision. Neither ascorbic acid nor hemoglobin interfered with the measurement. Bc values determined by the assay reflected more clearly the pathophysiological condition of hepatobiliary disease patients with jaundice than the values of total bilirubin or direct bilirubin determined by conventional methods. From these observations, we concluded that this Bc assay is valuable for the evaluation of jaundice. J. Clin. Lab. Anal. 14:27–31, 2000. © 2000 Wiley-Liss, Inc.

Novel assay for measuring serum conjugated bilirubin and its clinical relevance

We have developed a new enzymatic assay for the determination of conjugated bilirubin (Bc) using stable liquid reagents. In this assay, only Bc is selectively oxidized by bilirubin oxidase at pH 5. 0 in the presence of nitrilotris (methylenephosphonic acid) trisodium salt, ethylenediaminetetraacetic acid disodium manganese (II) salt, and 4-hydroxy-2,2,6,6,-tetramethylpiperidine 1-oxyl. Bc is quantitatively determined from a decrease in the absorbance at 450 nm caused by Bc oxidization. The reagent solutions of the assay were developed so that they could be stably stored for one year together with bilirubin oxidase, in order to eliminate the need to prepare working solutions every time they are required. The assay has good reactivity, differentiability, measurability, and precision. Neither ascorbic acid nor hemoglobin interfered with the measurement. Bc values determined by the assay reflected more clearly the pathophysiological condition of hepatobiliary disease patients with jaundice than the values of total bilirubin or direct bilirubin determined by conventional methods. From these observations, we concluded that this Bc assay is valuable for the evaluation of jaundice.

ChemInform Abstract: Recent Advances in the Catalytic Oxidation of Alcohols with 2,2,6,6‐ Tetramethylpiperidine‐1‐oxyl (TEMPO) and Its Application to Organic Synthesis

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Study of phase separation in polyurethane using paramagnetic labels. Effect of soft segment molecular weight, structure, and thermal history

AbstractThe morphology of segmented polyurethane (PU) elastomers was studied by means of ESR at various temperatures ranging from 100K‐450K. The PU's were based on 4,4'‐diphenylmethane diisocyanate (MDI), poly (oxytetramethylene) glycols (PTMO) and hydroxyl‐terminated random compolymers of tetrahydrofuran and 3‐methyl‐tetrahydrofuran (THF/Me‐THF). Purified 1,4‐butanediol (BD) was used as a chain extender. The nitroxide probe, 4‐hydroxy‐2‐2',6‐6'‐tetramethylpiperidine‐1‐oxyl (TEMPOL), was used to label the polyurethanes by reaction with an NCO group of MDI. Analysis of the electron spin resonance (ESR) spectra suggested that the label situates at heterogeneous sites, which means that a two‐phase domain is present. The morphologies at 300K and 400K were compared. It was found from ESR spectra that polyurethanes made from soft segments having higher MW exhibited greater phase separation at 300K than their corresponding elastomers made from lower MW soft segments. However, at 400K the more isotropic ESR spectra for the PUs containing higher MW soft segments suggested that the PUs were more mobile than their analogs having lower MW soft segments. The introduction of 3‐methyl side groups decreased the phase mixing at 400K due to steric hindrance.

Single crystal ESR studies of a nitroxide spin label. I. Determination of the G and A tensors

Experimental results are reported for the G tensor and the nitrogen hyperfine A tensor of a stable nitroxide radical 4-hydroxi-2,2,6,6- tetramethyl-piperidine-1-oxyl (TANOL), introduced as impurity in a matrix of known structure, 4-hydroxi-2,2,6,6-tetramethyl-piperidine, gxx=2.0099, gyy=2.0061, gzz=2.0024, Axx=5.3 G, Ayy=7.0 G, Azz=35.0 G. Due to the perturbation in to the crystal structure introduced by TANOL it was not possible to determine the orientation of the tensors relative to the molecular bonds but only relative the crystal axes. The presence of hydrogen bonds as well as the crystal packing both strongly influence the orientation of the G and A tensor. The value of the nitrogen hyperfine tensor was determined for the first time for this nitroxide and correlates well with the hydrogen bonding of the NO fragment.

Synthesis and properties of nicotinic acid derivatives containing a 2,2,6,6- tetramethylpiperidine 1-oxyl residue

N1-(Nicotinoyl)-N2-4-(2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl)hydraxine was obtained by condensation of nicotinoyl hydrazide with 2,2,6,6-tetramethyl-4-oxopiperidine 1-oxyl. Acylation of 2,2,6,6-tetramethyl-4-hydroxypiperidine 1-oxyl with nicotinoyl chloride gives nicotinic acid 2,2,6,6-tetramethyl-1-oxyl 4-piperidyl ester. A spin-labeled analog of nicotinamide was obtained by condensation of nicotinoyl azide with 4-amino-2,2,6,6-tetramethylpiperidine 1-oxyl. The synthesis of 1-N-(Β-D-ribofuranoside)-3'-N[4-(2,2,6,6-tetramethylpiperidine-1-oxyl)pyridinecarboxamide from 2,2,6,6-tetramethyl-4-nicotinoylaminopiperidine 1-oxyl and 2,3,5-tri-O-benzoyl-Β-D-ribofuranosyl bromide proceeds without damage to the iminoxyl radical. The preparation of the corresponding spin-labeled nucleotide is hindered by destruction of the iminoxyl radical during ion-exchange chromatography.