It is said that dodecyl-trimethylammonium chloride (DTA) is used to dissolve hyaluronic acid (HA) in an organic solvent such as DMF.
If the experiment is conducted using the method below, will HA (ex. 4.7 kDa) and DTA react in a 1:1 ratio? Or is there an excess of the two?
I want to save HA as much as possible.
[method]
A 7.0% (w/v) solution of dodecyltrimethylammonium chloride in 1.6 ml of deionized water was added dropwise to 1.6 ml of HA 10% (w/v). This reaction formed a white precipitate. The precipitate was then separated from the supernatant by centrifugation. Once lyophilized overnight, the final product was obtained, HA-DTA powder.
This works because the DTA salt of HA is insoluble in water but soluble in organica. HA has 1 carboxylic acid group for every two saccharide units. When these are ionized with Na cations - soluble. When the DTA Cl is added, when DTA cations replace the Na the solubility decreases.
does the precipitate have all Na replaced with DTA? You can imagine that insolubility might occur at less than 100% replacement!
the easiest way to tell is to wash it thoroughly, dissolve in an organic solvent and analyze for Na. If you can quantitate Na you can determine how
much cation replacement has occurred.
James E Hanson
In the above [method], DTA has Mw 263.89 and HA is 4.7kDa.
When I calculated, it showed that 0.42mmol of DTA and 0.034mmol of HA were used. Is this calculation correct?
If yes, was excess DTA used for ion exchange of HA?
the repeat unit for HA is C14H21O11N if I am counting the H's right. That is MW ~380 Per unit
use this value to calculate - not the overall MW of HA. so the mass ratio of DTA to HA should be 1:1 per repeat unit: ~264:380
James E Hanson I completely understood. Thank you for kindly answering my a little embarrassing question :)
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