Picosecond fluorescence microscopy for measuring chlorophyll and porphyrin components in conifers and cultured cells.

Abstract

A synchroscan streak camera was adapted to a microscopic system for fluorescence lifetime measurements. By using this device together with a synchronously pumped dye laser system, a time resolution of 40 ps was attained. Recent applications of this technique include the fluorometric detection of chlorophyll from microscopic parts of spruce needles to measure defects within the photosynthetic system after exposition to environmental pollutants or their photooxidants and fungal infection. It was found that after a combination of continuously high ozone concentration and infection by Rhizosphaera Kalkhoffii, the relative fluorescence intensity of a chlorophyll component with a decay time of 550 ps decreased significantly, whereas a component decaying with 110 ps remained almost constant. This indicates a selective inhibition within the photosystem II. In addition, fluoresence lifetimes of hematoporphyrin derivative - a tumor-selective photosensitizer used for diagnosis and photodynamic therapy of cancer - were measured in the picosecond time range. In comparison with previous nanosecond measurements, a new fluorescent component withh a lifetime of 90 ps was detected from Hpd solutions. This component may be attributed to a dimeric or aggregated species which is monomerized when taken up by malignant or non-malignant cells