Hiromu Kashida

Mimicking the masters: An artificial nucleic acid, serinol nucleic acid (SNA), formed oligomers in which natural nucleobases were tethered through its 2-amino-1,3-propanediol (serinol) scaffold. These SNA oligomers have two unique properties: their chirality is controllable by sequence design and can be inverted by reversing the sequence (see picture), and they can cross-hybridize with DNA and RNA with sufficient thermal stability.

The growing field of DNA technology requires new modified DNAs that can perform advanced functions. No matter how we optimize the length and sequence of DNA using only the four naturally occurring nucleotides, potential performance is limited. In this review, we describe a facile and effective method of rationally designing new functional DNA by focusing on acyclic scaffolds, especially threoninols, which are utilized to incorporate functional molecules into DNA. Wedge-type insertion of a functi

Reversible photo-cross-linking of a DNA duplex through the [2+2] photocycloaddition of styrylpyrene is reported. Styrylpyrene moieties on d-threoninol linkers were introduced into complementary positions on DNA strands. Irradiation of the styrylpyrene pair in the duplex with visible light at λ=455 nm induced a [2+2] photocycloaddition between styrylpyrenes that cross-linked the two strands of the duplex. Two diastereomers were formed after [2+2] photocycloaddition as a result of rotation of the

In this study, we report a photo-cross-linking reaction between p-stilbazole moieties. p-Stilbazoles were introduced into base-paring positions of complementary DNA strands. The [2 + 2] photocycloaddition reaction occurred rapidly upon light irradiation at 340 nm. Consequently, duplex was cross-linked and highly stabilized after 3 min irradiation. The CD spectrum of the cross-linked duplex indicated that the B-form double-helical structure was not severely distorted. NMR analysis revealed only o

Seeing red: Aggregates in which methyl red and naphthyl red moieties are stacked alternately in a DNA duplex have been prepared by hybridization of two DNA–dye conjugates (see picture). A sharp absorption band appears at 478 nm, which is different from that of the individual dyes. A strong CD effect is also induced by the interstrand heterostacking of the dyes. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2004/z460870_s.pdf or fro

Off means off: An in-stem molecular beacon in which D-threoninol units tether perylene and anthraquinone in the stem region effectively detected target sequences and was able to discriminate a one-base-deletion mutant from the wild-type (full-match) sequence without background emission (see picture). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted b

By using perylene and pyrene as fluorophores, we have designed various fluorophore assemblies that mimic inorganic quantum dots in showing a high emission intensity, a large Stokes’ shift, and a modulated emission maximum. For this purpose, we utilized two kinds of duplex motifs with d-threoninols as scaffolds: cluster and interstrand-wedged motifs. In the cluster motif, fluorophores are introduced into both strands to produce tentative pseudo-“base-pairs”, in which the dyes strongly interact wi

For the detection of deletion polymorphisms, two pyrene moieties are tethered to an oligodeoxyribonucleotide (ODN) on both sides of the intervening base; one- and two-base deletions can be selectively detected by the strength of the excimer emission.

An ordered dye cluster of Methyl Reds was formed in double-stranded DNA by hybridizing two complementary DNA-dye conjugates, each involving a Methyl Red moiety on a threoninol linker and a 1,3-propanediol spacer arranged alternately in the middle of the DNA sequence. In the duplex, Methyl Reds from each strand were axially stacked antiparallel to each other, as determined from NMR analysis. This clustering of Methyl Reds induced distinct changes in both UV/Vis and CD spectra. Single-stranded DNA

Functional molecules such as dyes (Methyl Red, azobenzene, and Naphthyl Red) were tethered on D-threoninol as base surrogates (threoninol-nucleotide), which were consecutively incorporated at the center of natural oligodeoxyribonucleotides (ODNs). Hybridization of two ODNs involving threoninol-nucleotides allowed interstrand clustering of the dyes on D-threoninol and greatly stabilized the duplex. When two complementary ODNs, both of which had tethered Methyl Reds on consecutive D-threoninols, w

To increase the apparent Stokes' shift of perylene, pyrene (donor) and perylene (acceptor) were assembled in a DNA duplex to achieve the efficient fluorescence resonance energy transfer (FRET) from pyrene to perylene. Multiple donors were introduced in the vicinity of acceptors through D-threoninol and natural base pairs were inserted between the dyes. Accordingly, donors and acceptors could be accumulated inside the DNA without forming an undesired excimer/exciplex. When two pyrene moieties wer

A DNA duplex was used as a scaffold to evaluate the intrinsic reactivity of [2 + 2] photodimerization between stilbene derivatives; the duplex pre-organizes the substrates avoiding the need for an association step. Unmodified stilbenes were first introduced at base-pairing positions on complementary DNA strands. The duplex was then irradiated with 340 nm UV light. HPLC analyses revealed that [2 + 2] photodimerization proceeded rapidly without side reactions. Thus, it was confirmed that the DNA d

Fluorescence imaging techniques have contributed to our understanding of various biological phenomenon; however, fluorescence spectral overlap significantly restricts multiplexing capability. Several strategies have been reported to overcome this limitation by utilizing the superior programmability of DNA technologies and nanostructures, but in practice, it remains challenging to achieve broad adoption of these multiplexed detection methods due to the complexities of these DNA designs. Here we r

Organization of supramolecular assemblies of chromophores with precisely-controlled orientation and sequence remains challenging. Nucleic acids with complementary base sequences spontaneously form double-helical structures. Therefore, covalent attachment of chromophores to DNA or RNA can be used to control assembly and orientation of chromophores. In this perspective, we first review our recent work on the assemblies of fluorophores (pyrene and perylene) by using natural base pairs. The interact

Herein we report the construction of efficient light-harvesting antennae by hybridization of DNA oligonucleotides containing high densities of fluorophores into DNA junctions through d-threoninol. Six pyrene donors could be incorporated into each arm without self-quenching. A perylene acceptor was located at the center of the junction. Antenna effects of a duplex and three- to eight-way junctions were systematically compared. Six- and eight-way junctions had the highest antenna effects, and thei