Freeze-thaw is not advisable. So better is lyophilization, however the lyophilized powder needs to be dissolved at alkaline pH conditions (for example, at high molar concentrations of NaOH) and then slowly pH might be brought down.
Oligomer formation cant be avoided so easily. The attached paper (J Biol Chem. 2011 April 22; 286(16): 13827–13833) describes about "Amyloid-β Monomer and the Monomer-Oligomer Equilibrium" in detail.
From my experience, the only way to keep the amyloid samples is to lyophilize them.
As stated above the best way is purify with SEC prior to use.
Also, once you have the peptide in solution you can slow down oligomer formation (dramatically) by keeping the samples on ice until use.
I personally find flash-Freezing in separate aliquots as the best way to store amyloids once they have formed the fibrillar structures. As others have already mentioned, repeated thawing is not good at all. I am particularily apprehensive about lypholization for it causes a change in the size distribution of he structures. On most ocassions, I have found that simply storing the aqueous preparation of amyloids at RT/4C/ice is good enough, provided you use them within a couple of days. Beware of fungal/bacterial contamination...they can put you into deep trouble.
To the best of our knowledge, no one compared the stabilities of betaamyloid with freezing/lyophilized method.
Only few studies concluded that AB42 and tau remained stable in CSF when stored >6 months at -70 or -80 °C. The storage stability of CSF Aβ42 at −80◦C was assessed through an internal quality control sample which was analyzed on a weekly basis during a time period of 26 months. The coefficient of variation (CV) on 214 different runs was 7.5%, which is less than the inter assay CV (7.7%) reported by the manufacturer and consequently signify the storage stability of Aβ42 during the accounted time period.
Therefore, it is recommendable to store CSF samples at −80◦C as a precaution to possible future analyses. AB42 and tau are very stable in CSF and that samples can be stored for a very long period at -80 °C. AB42 in CSF samples stored at 4, 18, and 37 °C decreased by ~20% during the first 2 days compared with the baseline value (-80 °C). Preferably, CSF samples should be shipped on dry ice when stored frozen.
Please refer following two articles for more information
1. Bjerke M et al., (2010) Confounding Factors Influencing Amyloid Beta Concentration in Cerebrospinal Fluid
2. Schoonenboom NSM et al., (2005) Effects of Processing and Storage Conditions on Amyloid(1– 42) and Tau Concentrations in Cerebrospinal Fluid: Implications for Use in Clinical Practice
If you have got any updated information about lyophilized betaamyloid and its stability, please share the same.
Many people have lyophilized the samples and used NH4OH and a fluorinated alcohol as well. Check out some papers by Dr. Mi Hee Lim from the University of Michigan or Dr. Katherine Franz from Duke University. Both are in the departments of chemistry.
It depends whether you want the monomeric or oligomeric form, and whether you are workind with Abeta40 or 42, Synthetic 42 can be converted into the monomeric form by treating with TFA , blowing off withh nitrogen, evacuating, then taking up with trifluoroethanol, blowing off and evacuating again, Repeating this three times, finally dissolve in the TFA and aliquot into required amounts for use later and evacuate again, store all the samples, which are now monomeric, at -80, then take up in PBS; incubate at 37 to convert into oligomers. ill post references later
I've started a project on this site to share protocols and methodological details on amyloids. For now, it would be located on this site and be open to anyone who wants to join (don't put proprietary information in there that you do not want seen by others). Message me back if you want to join.
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