Hadamard transform photothermal deflection densitometry of electrophoretically blotted proteins

Hadamard transform spatial multiplexing techniques are applied to laser densitometry in order to prevent the photo-induced degradation of sensitive materials. Photochemical and thermal degradations can often occur in point focused scanning laser densitometry. In spatial multiplexing, the excitation source is defocused and efficiently distributed throughout the sample, reducing local power density. In this paper, we describe the application of Hadamard transform spatial multiplexing to transverse photothermal deflection spectroscopy (PDS). Proteins western blotted on nitrocellulose membrane are line imaged using the Hadamard transform PDS densitometer. For comparison, the blots are imaged with a high-dynamic-range video densitometer.