Olympus UApo N 340 40X Water Immersion Microscope Objective (NA 1.15, Infinity, UV Optimized)

The Olympus UAPO N 340 40x Water Immersion Objective (N2709300) is a specialized biological objective designed for Fura-2 calcium imaging and other UV-excitable fluorescence applications. This objective is distinguished by its high UV transmission down to 340nm, enabling ratiometric calcium imaging with Fura-2—one of the most widely used calcium indicators in cell biology and neuroscience.

The 40× magnification and ~1.15 numerical aperture provide high resolution and excellent light collection, critical for detecting the relatively weak fluorescence signals from calcium indicators. The high NA ensures efficient excitation and emission light collection, improving signal-to-noise ratio in fluorescence imaging.

Fura-2 calcium imaging is a ratiometric technique that measures intracellular calcium concentration by exciting the dye at two wavelengths (340nm and 380nm) and measuring the ratio of emission intensities. This approach provides quantitative calcium measurements that are independent of dye concentration, photobleaching, and cell thickness. The 340nm UV transmission of this objective is essential for exciting Fura-2 at its calcium-bound excitation peak, enabling accurate ratiometric measurements.

Standard microscope objectives typically have poor transmission below 400nm due to absorption by optical glass and cement. This objective employs specialized UV-transmitting glass and optical coatings that maintain high transmission at 340nm, enabling efficient Fura-2 excitation. This UV transmission also makes the objective suitable for other UV-excitable fluorophores including DAPI, Hoechst dyes, and Indo-1.

The Apochromat (UAPO) optical design provides superior chromatic aberration correction across a broad wavelength range from UV to visible. This correction is essential for ratiometric imaging where precise registration between different wavelength channels is critical for accurate ratio calculations.

The ~0.25mm working distance is short but typical for high-NA water immersion objectives. This working distance is optimized for imaging cells on coverslips or in thin chambers.

Water immersion is ideal for live-cell calcium imaging as water is non-toxic to cells and maintains physiological conditions during long-term experiments.

The infinity-corrected optical design with RMS thread mount is compatible with Olympus BX, CX, and IX series microscopes.