Reversible circularization of an anthracene-modified DNA conjugate through bimolecular triplex formation and its analytical application.

We prepared an oligodeoxyribonucleotide conjugate (5-3ant(2)18) carrying two anthracenes, each of which was tethered to both ends of the conjugate through hexamethylene linker chains. The conjugate has a mirror repeat of two heptamer sequences, such that it forms a bimolecular triplex with the single stranded target, forming a two-fold U-shaped conformation. The conformation of the conjugate in its triplex structure could be frozen instantaneously by circularization through photodimerization of the anthracenes. Compared with the duplex formation of linear probes with relevant sequences, bimolecular triplex formation of 5-3ant(2)18 shows a unique feature in its target recognition; it binds the target tightly, yet still retains high sequence selectivity. Circularization of 5-3ant(2)18 by UV photoirradiation was verified as the probe reaction for a DNA assay. The probe reaction could be performed in a few seconds over a wide range of temperatures, at least between 0 and 25 °C. In addition, the reaction could be regarded as a reversible method for the preparation of circular DNA that shows higher affinity for the target.

Electrochemical Molecular Beacon for Nucleic Acid Sensing in a Homogeneous Solution.

Ferrocene (Fc) and ß-cyclodextrin (ßCyD) were modified at each end of stem-loop structured DNA as an electrochemical signal generator and its quencher, respectively, to give an electrochemical molecular beacon (eMB). A relatively high efficiency of signal quenching was achieved by an inclusion complex (ßCyD ⊃ Fc) formation that was induced on the stem structure of the closed form (= stem-loop structure) of eMB. With the addition of target DNA, the structure of eMB opened to form a linear duplex, where the Fc dissociated from the ßCyD to restore its intrinsic electrochemical signal. The signal contrast of the electric current for this off/on-type sensor was high, ca. 95. This technique did not require any modification of the electrode surface, and it realized the detection of the target nucleic acids in a homogeneous solution with a high sensitivity using high-performance liquid chromatography (HPLC) equipped with electrochemical detector.

The effect of local structural disruption on the yield of photochemical ligation between anthracene-oligonucleotide conjugates.

The techniques of chemical ligation have attracted great attention as an alternative to enzymatic joining of DNA ends. Here we introduce the photoligation of anthracene-modified ODN conjugates through anthracene cyclodimer formation. The effect of the positions and the kinds of single base mismatch on the template was evaluated using eight templates with one-base displacements. We found out that the yield of the ligation was affected by mispairing in a position-dependent manner. Such results would be attributed to the disruption of the local structure at the ligation site.

Ergonomics and design for sustainability in healthcare: ambient assisted living and the social-environmental impact of patients lifestyle.

This work presents considerations on Ergonomics and Design for Sustainability in the healthcare field based on research experiences of the Technology and Design for Healthcare (TeDH) research group of INDACO (Industrial design, communication, arts and fashion) department of Politecnico di Milano. In order to develop a multidisciplinary approach to design able to answer to specific user needs such as elderly in an environmental sustainable way (1) this paper shows the results we achieved concerning ergonomics and environmental impact in product development (2), the extension of this approach to interior and home design and the advantage of the application of Information Communication Technologies (ICT). ICT can help people with special needs to make their everyday life easier and more safe, at the same time, ICT can make social-environmental impact of everyday behavior evident and can be applied to manage sustainability. The specific theme is thus to integrate ergonomics and sustainability competences in the development of Ambient Assisted Living through a Product- Service System approach. The concept of product service system has the potential to improve product performances and services, establish new relations and networks with different actors in order to satisfy user needs and apply a systems approach considering environmental, social and economic factors in the users' environment.

Electrochemical signal modulation in homogeneous solutions using the formation of an inclusion complex between ferrocene and ß-cyclodextrin on a DNA scaffold.

Two DNA conjugates modified with ferrocene and ß-cyclodextrin were prepared as a pair of probes that work cooperatively for DNA sensing, in which the electrochemical signal of ferrocene on one probe was significantly "quenched" by the formation of an inclusion complex with ß-cyclodextrin of the other probe on the DNA templates.

Circular DNA formation on the bimolecular triplex of anthracene-modified oligonucleotide conjugate.

DNA is usually found in nature as a double stranded helix but there are many other structural forms that it can adopt. Triple helical DNA structures are one of these arrangements that DNA can form through some folding interactions. These structures have attracted great interest in the field of DNA recognition due to their higher affinity and selectivity. Here we introduced a bimolecular triplex structure formed by a anthracene-DNA conjugate through a well characterized photodimerization reaction in the presence of complementary target and evaluated the system for the target discrimination by using a mismatch target. Results indicated that the system could provide moderate discrimination.

Effect of local structural disruption on the photochemical ligation between anthracene-modified DNA conjugates.

DNA templated ligation reactions has attracted great interest in the field of DNA probing and medical diagnosis. To date some research groups reported a variety of chemical ligations, in which two DNAs with reactive groups that bound adjacently on the complementary strand were connected covalently to form a corresponding longer product. Here we introduced the photoligation of anthracene modified ODN conjugates through anthracene cyclodimer formation. The effect of the position of single base mismatch on the template was evaluated using six sequences with one-base displacements. The yield of the ligation was affected by mispairing in position-dependent manner. It would be due to the disruption of the local structure around the two anthracenes of both reaction partners.

Detection of one base mismatch using photochemical ligation.

We attached anthracene molecules covalently to one end of oligodeoxyribonucleotides to form three pairs of anthracene-ODN conjugates. The sequences of each pair of the conjugates were designed to bind adjacent sequences of the template with the anthracene units directed such that they stacked each other. The conjugates dimerized only in the presence of the template by light irradiation. We found that the ligation yields largely depended on the substituted position of anthracene groups. Sequence selectivity in the dimerization yield was preserved even in the system with highest reactivity. SNP bases could be discriminated rapidly by combining the techniques of MS spectroscopy.