Critical Use UVvis Spectrophotometer

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This funding request is for the replacement and upgrade of obsolete instrumentation that is well beyond its serviceable lifetime. The Hudson group has used a Varian Cary 300 Bio since 1999 which suffered a catastrophic failure of the Peltier device (3 years ago) after a litany of other serious problems (motherboard and optical train) which were serviced in recent years at no small expense, but is no longer able to be repaired.  As such, we no longer have adequate access to instrumentation to pursue our research. The current instrument has been critical to our research mission for the past 22 years. The requested instrument will primarily service the Hudson group (average group: 4 graduate, 2 UG); Konermann group (average group: 8 graduate, 2 undergraduate) and the Workentin group (average group: 6 graduate, 2 UG). As with our previous instrument, we expect and welcome regular use from the Wisner group (2-3 students, for characterization of photo-switchable molecules), the Luyt group (7-8 students, for quantum yield calculation in conjugation with our PTI spectrofluorimeter) and occasional use from groups. As well, the new instrument with extended red-range useful for gold-nanoclusters and organic and inorganic fluorophores (Gilroy group, 11 students).  The Varian Cary 300 instrument has been superseded by the Agilent Cary 3500 which possesses significantly improved design, by replacement of the error-prone mechanical transport by a fixed eight-position sample chamber that is temperature controlled by a Peltier-device and a multi-beam design. Additionally, the re-designed instrument uses a xenon lamp instead of the dual deuterium/visible lamp design of the Cary 300 which is more robust, economical and is capable of fast data collection for use in studying the kinetics of binding interactions. The instrument also features an air-cooled Peltier heating/cooling block eliminating the need for an external bath, which is also a point of failure eliminated. The instrument has the sensitivity and photometric stability suitable for the long experiments typically needed to study melts and renaturation curves. Additionally, rapid temperature ramping, with in-cell temperature monitoring, is available - this feature will be exploited to develop improved methodologies for determining nucleic acid analog thermal stabilities in a more time-economical fashion.