The project could demonstrate the coupling of a flow-flash experiment with IR step-scan measurements for the first time. This widens the applicability of the step-scan technique to monitor slow cyclic reactions such as the reaction of the retinal protein with light or even to the reaction of cytochrome c oxidanse with oxygen.
The method is particularly interesting for samples which are only available in small quantities, such as biological samples, due to its small sample consumption.
In this work we present our latest developments for step scan FTIR measurements to widen its applicability to noncyclic reactions. With our approach the reaction between two chemicals can be monitored as well with a time resolution in the µs time range. We use a micro mixing device to pump the sample solution through the measurement spot of a specially designed focusing unit. The reaction in the mixer is triggered by a laser flash and the spectrometer starts measuring the respective timeslice shortly before the laser flash hits the sample. While the measurement takes place the sample is continously towling. The flow rate is set in such a way that only a small portion of the sample volume is exchanged during the measurement. After the measurement of the timeslice the whole volume is purged and the next laser pulse is fired onto a completley fresh sample in order to measure the next timeslice. A typical step-scan experiment consumes only a few 10 µI of a mM sample solution, rendering it useful especially for biological sampIes. We applied our technique to the photodissociation of the CO-myoglobin complex and followed the rebinding of CO including changes in the protein.