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L J Arnold

Publications and source records attributed to L J Arnold.

27 records · Page 2Linked to original sources
PubMed1976

Determination of the hydride transfer stereospecificity of nicotinamide adenine dinucleotide linked oxidoreductases by proton magnetic resonance.

A facile proton magnetic resonance technique is described for the determination of the coenzyme stereospecificity during hydride transfer reactions catalyzed by pyridine nucleotide dependent oxidoreductases. The reliability of this technique was demonstrated by examining the coenzyme stereospecificity of lactate, malate, and 3-phosphoglycerate dehydrogenases, which are known to be A-stereospecific enzymes, as well as triosephosphate and octopine dehydrogenases, which are known to be B-stereospecific enzymes. Furthermore, by applying this technique, it was shown that the previously unstudied enzymes D-beta-hydroxybutyrate and 4-aminobutanal dehydrogenases are B- and A-stereospecific enzymes, respectively. In addition, the nicotinamide adenine dinucleotide linked reaction of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides was found to be B stereospecific, like the reaction of the nicotinamide adenine dinucleotide phosphate linked yeast enzyme.

Alcohol Oxidoreductases↗
PubMed1971

A structure of pyridine nucleotides in solution.

Re-examination of the structure of pyridine coenzymes in solution by use of the 220-MHz high-frequency nuclear magnetic resonance spectrometer indicates that there is primarily one folded structure that is in rapid equilibrium with an open form. Reduced DPN(+) and reduced analogs of DPN(+) exist predominantly with the B side of the dihydropyridine ring folded against the adenine moiety. (The oxidized coenzymes appear to exist in the same folded structure.) Furthermore, the ribose protons undergo very little conformational change upon reduction of the pyridine ring; this observation strongly suggests a considerable similarity between the folded forms of the oxidized and reduced coenzymes. A model of the folded structure is presented.

Chemical Phenomena↗
PubMedDate not supplied

Nucleophilic addition to the 9 position of 9-phenylcarboxylate-10-methylacridinium protects against hydrolysis of the ester.

The chemiluminescent reaction of an acridinium ester (AE) requires addition of peroxide to the 9 position of the acridinium ring. The addition of a hydroxide ion to the 9 position of an acridinium ester to form the carbinol adduct has also been well documented. We have observed a similar addition of other nucleophiles to the acridinium ring to form an acridan adduct. The adduct formed with bisulphite has been particularly well-characterized for rate of formation, rate of reversion, and reaction equilibrium. The formation of an adduct (other than H2O2) has been demonstrated to decrease significantly the reactivity of the adjacent ester bond to alkaline hydrolysis. The resulting, more stable adduct is very useful when the acridinium ester is used as a label in DNA probe-based assays. The adduct is highly resistant to hydrolysis under the conditions often desired for DNA probe-based assays (high temperature, elevated pH, extended storage).

Acridines↗
PubMedDate not supplied

A non-nucleotide-based linking method for the preparation of psoralen-derivatized methylphosphonate oligonucleotides.

A method is reported for conjugating an analog of 4'-(aminomethyl)-4,5',8- trimethylpsoralen to methylphophonate oligonucleotides. This method enables the psoralen moiety to be coupled to the phosphonate backbone between any two desired bases in a sequence. When hybridized to a target mRNA, the psoralen moiety can be directed toward a uridine base and, in turn, can undergo a photo-addition reaction with the target under UV irradiation at 365 nm. Several different non-nucleotide-based amino-linker reagents have been prepared for incorporation into methylphosphonate oligonucleotides by standard phosphonamidite chemistry. In addition, an N-hydroxysuccinimide activated ester analog of 4'-[(3-carboxypropionamido)methyl]-4,5',8- trimethylpsoralen has been synthesized for conjugation to the amino-linker moieties. Using this approach, we have prepared a number of psoralen-methylphosphonate-oligonucleotide conjugates which are complementary to the chimeric bcr/abl mRNA associated with chronic myelogenous leukemia. Solution hybridization studies with a 440-base subfragment of the bcr/abl RNA have shown that the psoralen moiety does not adversely affect duplex stability. Polyacrylamide gel electrophoresis analyses have demonstrated that the psoralen-oligonucleotide conjugates undergo photo-addition to the RNA in a sequence-specific manner. Optimal photo-addition occurs when the psoralen moiety is inserted adjacent to one or more adenine residues in the oligonucleotide sequence, particularly between adenine and thymine (5'-3'). This internal labeling approach greatly increases the number of potential target sites available for photo-cross-linking experiments.

Base Sequence↗