Transient absorption microscopy (TAM) provides imaging contrast from absorptive pigments such as hemeproteins and melanin, based on femtosecond to picosecond-timescale relaxation dynamics. TAM operates by exciting the sample with a short pump pulse, then measuring the time-dependent change in optical absorption, after excitation, with a probe pulse. Here we show that a 520nm pump and 620nm probe provides label-free imaging contrast for hemoglobin, myoglobin, and respiratory chain hemes of mitochondria with sensitivity to redox. We also introduce a simple convolutional neural network for analysis of TAM stacks. Finally, we will discuss future clinical applications to mitochondrial disease.
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