Ureido-derivatized polymers based on both poly(allylurea) and poly(L-citrulline) exhibit UCST-type phase transition behavior under physiologically relevant conditions.

There are few examples of polymers that exhibit upper critical solution temperature (UCST) behavior under physiological conditions of temperature, pH, and ionic strength. In this study, we demonstrated that polymers with ureido groups undergo UCST-type phase transitions under physiologically relevant conditions. Poly(allylurea) copolymers showed UCST behavior at pH 7.

RNA-mediated electron transfer: double exponential distance dependence.

We describe the long-range excess electron transfer through RNA duplexes consisting of a pyrene electron donor and a nitrobenzene electron acceptor that shows double exponential distance dependence.

Fluorescence quenching properties of multiple pyrene-modified RNAs.

RNA molecules with multiple pyrenylmethyl substituents on the 2'-O-sugar residues can form duplexes with complementary RNA sequences without losing thermal stability. In the RNA duplexes, covalently incorporated pyrenes can assemble in a helical manner along the minor grooves of the duplex. These helically assembled pyrene arrays exhibit intense excimer emissions that are efficiently quenched with methyl viologen.

Efficient quenching of the excimer fluorescence derived from pyrene arrays on RNA duplexes.

We studied the RNA oligomers having pyrenylmethyl substituents at the 2'-O-sugar residues. It has been shown that the pyrene-modified RNAs can form duplexes with complementary RNA sequences without loss of thermal stability. Absorption, fluorescence, and circular dichroism spectra revealed that the multiply incorporated pyrenes are projected toward the outside of RNA duplexes and assembled in helical aromatic arrays along the minor grooves of the RNA duplexes.

Photocurrent responses from pyrene-modified RNA duplexes on gold surface.

The self-assembled monolayers (SAMs) of RNA duplex containing pyrenylmethyl group(s) at the 2'-O-position(s) were prepared. Photo-irradiation of the pyrene-RNA SAMs in the presence of methyl viologen as an electron carrier efficiently generated cathodic photocurrent.

Conformational changes of DNA by photoirradiation of DNA-bis(Zn(II)-cyclen)-azobenzene complex.

Bis(Zn(II)-cyclen)-azobenzene derivative, which has two Zn(II)-macrocyclic tetraamine complexes connected through azobenzene spacer, has been synthesized as a cross-linking agent fordoublestranded DNA in aqueous solution. The Zn(II)-cyclen derivative selectively binds to A-T base pairs producing complexes between the Zn(II)-cyclen moiety and the imide-deprotonated thymine with breaking A-T base pairs. The azobenzene spacer undergoes cis/trans photoisomerization in the complex between the Zn(II)-cyclen derivative and the DNA duplex.