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Advanced Condenser Systems: Abbe Condensers

Para-Aminobenzoic Acid (PABA)

The digital images presented below were recorded with a QX3 microscope body and an Abbe substage condenser equipped for transmitted Rheinberg illumination. These photomicrographs are unretouched and were captured with the QX3 interactive software.

Recrystallized PABA
PABA Crystals at 200x Magnification
(Green Central and Red/Yellow Annular Gels)

PABA Crystals at 200x Magnification
(Green Central and Red/Yellow Annular Gels)

PABA Crystals at 200x Magnification
(Green Central and Red/Yellow Annular Gels)

Para-aminobenzoic acid (PABA), a component of pteroylglutamate, was once considered a vitamin and named vitamin B-x because it serves as a provitamin for some bacteria. Later studies in humans demonstrated that it does not have vitamin activity because humans lack the ability to synthesize folate from PABA. This biochemical is very useful in other ways and has been extensively utilized as a sunscreen in topical lotions to protect the skin from harmful ultraviolet radiation upon exposure to the sun. It is also effective in the treatment of vitiligo, a condition that causes discoloration of the skin. Natural sources of PABA include bran, kidney, liver, molasses, wheat germ, and yogurt. There are no reported symptoms arising from a dietary deficiency of PABA.

Semi-transparent specimens are difficult to image using unaided brightfield optical microscopy. The images above were recorded using the Intel Play QX3 microscope in transmitted brightfield mode with the assistance of Rheinberg illumination. Dyed acetate gel filters were strategically placed below the aperture diaphragm of an aftermarket Abbe-style condenser to generate the Rheinberg effect. A 15-millimeter central filter was surrounded by a larger annular filter to combine the effects of oblique specimen illumination by light filtered through the annular filter superimposed over a background of light filtered through the central filter.

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