Monday, August 30, 2004

mechanisms of cell staining

The specific mechanisms for cell staining using various dyes is still poorly understood and largely empirical. Nevertheless, we do know a few things:

Methylene blue stains the nucleus. The + charge on the N acts on -ly charged O on the phosphate esters of DNA, which is located in nucleus.

Eosin stains the cytoplasm pink. Its two - charges per molecule, hence a dianion, bind electrostatically with the + charges on +ly charged protein groups such as arginyls, histidyl and lysyls [hey, cool! a voweless word!]. Hence it stains protein-rich regions such as the cytoplasm.

PAS (periodic acid Schiff), a mixture between periodic acid (HIO4) and Basic fuchsin, stains carbohydrates pink. Thus it also stains glycoproteins (proteins containing carbohydrates). The acid breaks glucose at the C-2 and C-3 bond forming 2 aldehydes and IO3-. The NH2+ in basic fushcin then reacts with the aldehyde thereby linking the dye and the carbohydrate.

Cool. I've actually used these compounds at some point in the lab before. It's nice to finally know how these things work.

My Schaum's review books arrived today. I'm torn between being excited about finally starting my Biochem review and ... well, not being excited. I read the first few pages before I lost interest and resumed reading William Gibson's Neuromancer instead. "Oh well," I tell myself, "I still have a lot of time to review. Besides, I have to study/practice for the TOEFL exam on the 11th. And, I do better when I cram anyway." Heh.

now playing: Anekdoten - Vemod

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