DNA-Mediated Electron Transfer in Naphthalene-Modified Oligonucleotides

Naphthalene-modified oligonucleotides have been synthesized and characterized with respect to electron transfer chemistry. Using the Sonogashira coupling reaction, naphthalene can be covalently anchored onto a modified uridine through an ethynyl linkage. This tethering allows for effective electronic coupling with the DNA bases, resulting in a significant red shift of the absorption bands of the naphthalenic chromophore. Modification with this chromophore does not appear to affect the overall stability and structure of the DNA. Upon selective irradiation of the naphthalene moiety at 340 nm, photoreduction of a distal electron trap, 5-bromouridine, embedded in the DNA base stack occurs. This DNA-mediated reduction from a distance was found to be significantly more efficient with substitution of 5-bromouridine toward the 5′-end than toward the 3′-end. These results support a general preference for electron transfer through DNA toward the 5′-end, irrespective of the donor. In addition, differences in efficiency of photoreduction through intrastrand and interstrand pathways are observed. For DNA-mediated reduction, as with DNA-mediated oxidation, significant differences in the charge transfer reaction are apparent that depend upon subtle differences in coupling into the DNA base stack

Stability on minimal submanifolds in symmetric spaces

We determine the stability of totally geodesic submanifolds in a compact symmetric space, which are called polars and meridians (see 2.1). These subspeces were introducued by Chen and Nagano ([CN-1]) and we have many intersting results after that ..

ANTIPODAL SETS OF SYMMETRIC R-SPACES

We show that antipodal sets of symmetric R-spaces have the following properties. Any antipodal set is included in a great antipodal set and any two great antipodal sets are congruent

Attenuation of guanine oxidation via DNA-mediated electron transfer in a crowded environment using small cosolutes

Guanine oxidation induced by photoirradiation on a pyrene-modified oligonucleotide was investigated under molecular crowding using small cosolutes such as glycerol. The efficiency of guanine photooxidation was suppressed in accordance with the increase in the concentration of glycerol. The results of photooxidation experiments using fully matched and mismatched DNA showed that guanine decomposition was mainly caused by DNA-mediated electron transfer (ET) in glycerol mixed solutions, as well as in diluted aqueous buffer solutions. Multiple factors can contribute to the suppression of guanine oxidation in crowded environments. However, our experimental results indicated that the attenuation of the DNA-mediated ET process suppressed guanine oxidation. On the other hand, experiments using ethylene glycol showed that guanine decomposition efficiency varies depending on the surrounding solvent. These results suggested that changes in the characteristics of the surrounding medium affect the DNA fluctuation, dominating DNA-mediated ET

Kanda University pre-service teacher training program for teaching English to children : curriculum design and evaluation

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