This is in regards to the correspondence listed below about DiOC staining of ER.

There are two dyes being talked about:  DiOC18 and DiOC.  They both have
the same cyclic structure that produces fluorescence, but they differ in
the length of the alkyl chains that are connected to them.  DiOC18
(actually DiOC18(3)) has two 18 carbon chains, and thus is insoluble in
water and doesn't cross membranes.  "DiOC" probably refers to DiOC6(3) has
two 6 carbon chains, and is soluble in water and crosses membranes.

I am surprised to hear that DiOC18 labeled the ER.  In my experience, if
the DiOC18 was applied from the outside to a living cell, it labels only
the plasma membrane, and then gradually starts appearing in intracellular
vesicles by endocytosis.  It is possible for DiOC18 to label the ER, but it
should be introduced directly into the inside of the cell, for instance by
dissolving it in oil and injecting it.  When "DiOC" is applied to the
outside of a cell, it crosses the plasma membrane and produces a ER
staining pattern.   In fact, there is a good chance it labels all
intracellular membranes, and that the ER pattern is only the most obvious.
For certain, the mitochondria are also stained.  At low doses of DiOC, only
the mitochondria are stained because of accumulation of the dye by the
mitochondrial membrane potential.

However, it is always possible that a dye will behave differently for
certain organisms or under special conditions...

Mark Terasaki
Dept Physiology
University Connecticut Health Center
Farmington, CT

>>        Another non-related question: I have just used DiOC18 to stain
>>membranes. Since it has a long alkyl chain, I was expecting it to stain well
>>the plasma membrane and may be, to some extent, intracellular membrane
>>systems like endoplasmic reticulum. However, the latter was amazingly well
>>stained. I am not disappointed by this at all, because it turned out to be a
>>beautiful prep, but it was not what I had expected. Any explanations for
>>this? Could anyone tell me his favorite way to use the dye? (it could be a
>>preparation problem).
>
>
>DiOC is an ER stain, it's not a problem of preparation I think. I'm not sure
>if there is known anything new about the mode of DIOC staining. Some time
>ago it has been under debate. (Anybody knows something?)
>DIOC also stains the Dictyosomes of some organisms. I've no references here,
>but one could search e.g. for Quader, H. or Schnepf, E. to find some
>references about DIOC staining of plant ER.
>Arthur
>
>Dr. Arthur Schuessler
>University of Heidelberg
>Zellenlehre
>Im Neuenheimer Feld 230
>D-69120 Heidelberg
>Germany
>E-mail: [log in to unmask]
>FAX: 06221 / 54 49 13