The Development of the Virtual Notebook, a Wiki-Based Ready Reference Technology

Traditionally, library professionals have used a variety of ready reference technologies to assist in providing reference and user services. Technologies such as card files, vertical files, and reference notebooks are frequent components of library service desks. Ready reference technologies serve many purposes, most notably, helping staff to answer frequently asked questions and facilitating the sharing of information between library staff. This paper traces the development of the Virtual Notebook, a wiki-based ready reference technology, at Purdue University. The tool is placed within the historical context of ready reference technologies within the library profession and at Purdue. The authors present preliminary results from the implementation of the Virtual Notebook and discuss the tool’s future. The manuscript is an outgrowth of a presentation at the 2008 Brick and Click Symposium at Northwest Missouri State University

Editorial Board Thoughts

Editorial Board Thought

DNA as supramolecular scaffold for porphyrin arrays on the nanometer scale

Tetraphenyl porphyrin substituted deoxyuridine was used as a building block to create discrete multiporphyrin arrays via site specific incorporation into DNA. The successful covalent attachment of up to 11 tetraphenyl porphyrins in a row onto DNA shows that there is virtually no limitation in the amount of substituents, and the porphyrin arrays thus obtained reach the nanometer scale (~10 nm). The porphyrin substituents are located in the major groove of the dsDNA and destabilize the duplex by Tm 5-7 °C per porphyrin modification. Force-field structure minimization shows that the porphyrins are either in-line with the groove in isolated modifications or aligned parallel to the nucleobases in adjacent modifications. The CD signals of the porphyrins are dominated by a negative peak arising from the intrinsic properties of the building block. In the single strands, the porphyrins induce stabilization of a secondary helical structure which is confined to the porphyrin modified part. This arrangement can be reproduced by force-field minimization and reveals an elongated helical arrangement compared to the double helix of the porphyrin-DNA. This secondary structure is disrupted above ~55 °C (Tp) which is shown by various melting experiments. Both absorption and emission spectroscopy disclose electronic interactions between the porphyrin units upon stacking along the outer rim of the DNA leading to a broadening of the absorbance and a quenching of the emission. The single-stranded and double-stranded form show different spectroscopic properties due to the different arrangement of the porphyrins. Above Tp the electronic properties (absorption and emission) of the porphyrins change compared to room temperature measurements due to the disruption of the porphyrin stacking at high temperature. The covalent attachment of porphyrins to DNA is therefore a suitable way of creating helical stacks of porphyrins on the nanometer scale