Biomedical subjects

E M Rachlin

Publications and source records attributed to E M Rachlin.

6 recordsLinked to original sources

PubMed2001

Characterization of hydantoin products from one-electron oxidation of 8-oxo-7,8-dihydroguanosine in a nucleoside model.

Use of one-electron oxidants such as Na(2)IrCl(6) to oxidize 8-oxo-7,8-dihydro-2'-deoxyguanosine (OG) residues in oligodeoxynucleotides was previously shown to lead to predominant formation of a base lesion of mass M - 10 compared to starting material [Duarte et al. (1999) Nucleic Acids Res. 27, 596-502]. To thoroughly characterize the structure of this lesion, the oxidation of the nucleoside 9-N-(2',3',5'-tri-O-acetyl-beta-D-erythro-pentanosyl)-8-oxo-7,8-dihydroguanine with one-electron oxidants at pH 2-4 was used as a model for duplex DNA oxidation of OG residues. (1)H NMR and H,H COSY NMR studies in CD(3)OD along with LC-ESI-MS/MS fragmentation analysis are consistent with the assignment of the M - 10 species as a mixture of two pH-dependent equilibrating isomers, a guanidinohydantoin (Gh) and an iminoallantoin (Ia) nucleoside, both present as mixtures of epimers at the C5 position of the hydantoin ring, i.e., four total isomers are formed. The Gh/Ia mixture is formed from hydration and decarboxylation of the initially formed intermediate 5-hydroxy-8-oxo-7,8-dihydroguanosine, a species that is also produced by four-electron oxidation (e.g., singlet oxygen) of guanosine. The product mixture can be further oxidized to a species designated Ia(ox), a hydrolytically unstable material at pH 7 that has been characterized by ESI-MS and (1)H NMR. Competition studies with 8-oxo-7,8-dihydroadenosine placed the redox potential of Gh/Ia at about 1.0 V vs NHE. These studies provide important information concerning the structures of lesions obtained when OG, a "hot spot" for oxidative damage, serves as a "hole trap" in long-range electron-transfer studies.

Allantoin↗

PubMed2000

Characterization of spiroiminodihydantoin as a product of one-electron oxidation of 8-Oxo-7,8-dihydroguanosine.

[reaction: see text] Further oxidation of the common DNA lesion 8-oxo-7,8-dihydroguanosine by one-electron oxidants such as IrCl6(2-), Fe(CN)6(3-), or SO4-* leads to two major products, depending upon reaction conditions. In nucleosides at pH 7, 22 degrees C, the principal product is shown herein to be a spiroiminodihydantoin nucleoside, as a diastereomeric mixture, that can be characterized by NMR, ESI-MS/MS, and independent synthesis.

Crystallography, X-Ray↗

PubMed1988

Nitric oxide: a cytotoxic activated macrophage effector molecule.

The experiments reported here identify nitric oxide as a molecular effector of activated macrophage induced cytotoxicity. Cytotoxic activated macrophages synthesize nitric oxide from a terminal guanidino nitrogen atom of L-arginine which is converted to L-citrulline without loss of the guanidino carbon atom. In addition, authentic nitric oxide gas causes the same pattern of cytotoxicity in L10 hepatoma cells as is induced by cytotoxic activated macrophages (iron loss as well as inhibition of DNA synthesis, mitochondrial respiration, and aconitase activity). The results suggest that nitric oxide is the precursor of nitrite/nitrate synthesized by cytotoxic activated macrophages and, via formation of iron-nitric oxide complexes and subsequent degradation of iron-sulfur prosthetic groups, an effector molecule.

Animals↗

PubMed1987

Differential DNA methylation during the vegetative life cycle of Neurospora crassa.

Isotope dilution gas chromatography-mass spectrometry analysis of genomic DNAs isolated from the different growth phases of Neurospora crassa revealed significant differences in the amounts of 5-methylcytosine; the mol % of 5-methylcytosine was 0.36 in conidia (asexual spores), 0.40 in conidial germlings cultured for 3 h, 0.24 in mycelial cells that had grown exponentially for 6 and 12 h, and 0.40 in stationary-phase mycelial cells. These results indicate an approximate inverse correlation between the level of C methylation in the DNA and the presumed level of developmentally related transcriptional activity.

5-Methylcytosine↗

PubMed1987

Different levels of DNA methylation in yeast and mycelial forms of Candida albicans.

Isotope dilution gas chromatography-mass spectrometry analysis of genomic DNAs isolated from three Candida albicans isolates showed significant differences in the amounts of 5-methyldeoxycytidine (m5Cyt) in DNA from yeast-form and from mycelial-form cells; the moles percent m5Cyt were 0.11, 0.11, and 0.097 for yeast-form DNA and 0.045, 0.053, and 0.047 for mycelial-form DNA for the three isolates Sh8, 9938, and B311, respectively. The lower m5Cyt values for mycelial-form cells suggest that those cells may exhibit significantly greater gene activity than yeast-form cells.

Candida albicans↗

PubMed1983

Ion-sensitive electrode potentiometry of organic anions: application to quantitative structure-activity relationships.

Ion-sensitive electrode potentiometry is proposed for determination of substituent constants for structural modifications of organic acids. A liquid membrane anion-sensitive electrode responds reproducibly to a wide range of carboxylate and sulfonate ions. Fragment constants for the addition of a methylene group to aromatic and aliphatic acids are -2.4 and -3.3 +/- 0.15 kJ/mol, respectively. Agreement is observed between these constants and those determined by other techniques, including partitioning studies in biphasic systems, suggesting the use of potentiometry for quantitative structure-activity relationship studies. Furthermore, the electrode measurements correlate with biological effects resulting from hydrophobic interactions.

Anions↗