This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Post #58 answers the question as asked. The question underneath it is different.
Freeze-thaw: some peptide solutions tolerate freezing poorly because ice crystals damage protein structure. Whether your specific solution tolerates it depends on the formulation and is not something to test empirically. The conservative position is not to freeze.
That is the version I would defend. It is not the version I started with.
I read post #60 twice before replying, because I had assumed the opposite.
Peptide is a question about a distribution, not about a value, and treating it as a value is what produces the confident wrong answers.
Useful. I had the fact and not the reason, which turns out to be the important half.
One more thing on peptide that took me far too long to see: the two figures people quote are not measuring the same quantity. Once you notice that, the apparent contradiction disappears.
Everything in post #64 holds. The case it does not cover is the one I have.
Summarising the peptide thread so far, since it is long and the answer is buried: the first reply has the method, the fourth has the correction to it, and the rest is people agreeing at length.
Agreed on peptide, with one qualification that I think matters. The reasoning holds for the case as described. Change the starting assumption and it does not, and the starting assumption is the part nobody states.
Speaking only to peptide as I have actually seen it, rather than as it is usually described: the effect is real, it is smaller than the thread suggests, and the variance between people is larger than the effect.
Visible particulate is a strong signal in the other direction: it is a reason to stop and ask rather than to filter and proceed.
What would change my mind on peptide is a second dataset collected by someone with no stake in the first. Until then I hold it loosely and I would rather say so than pretend to more.
Taking post #71 at face value and following it one step further.
Clarity is a weak test. A solution can lose a significant fraction of its active content to degradation or adsorption while remaining perfectly clear.
This is the sort of thing that ought to be settled and apparently is not.
Practical note on peptide: write down what you expect before you look. The number of times I have found what I went looking for is higher than chance would allow.
Sensible. I would want the same detail before I acted on it either.
Post #75 put the caveat in the right place and I want to underline it.
Visible particulate is a strong signal in the other direction: it is a reason to stop and ask rather than to filter and proceed.
Posted with less confidence than the sentence structure implies.
Clarity is a weak test. A solution can lose a significant fraction of its active content to degradation or adsorption while remaining perfectly clear.
Post #79 is right about the mechanism and I think understates the practical bit.
A note on scope: what I am saying about peptide applies to the case in the first post and I would not extend it further without checking.
Narrowing post #80, because the general version has more than one answer.
Where I would push back on the peptide consensus is the confidence, not the direction. The direction looks right. The confidence is borrowed.
Visible particulate is a strong signal in the other direction: it is a reason to stop and ask rather than to filter and proceed.
Clarity is a weak test. A solution can lose a significant fraction of its active content to degradation or adsorption while remaining perfectly clear.
The literature is thinner on this than the confidence in the thread implies.
Trying to state the peptide position in a way that someone who disagrees would recognise as fair, because I do not think the version in this thread passes that test.
Freezing a reconstituted peptide solution is not automatically protective. Freeze-thaw cycling is one of the harsher things you can do to a protein in solution, and a single freeze is different from repeated ones.
It took me longer than it should have to see that.
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