Particulates in a reconstituted solution: identifying the likely source

Posting this under the heading it deserves: Particulates in a reconstituted solution: identifying the likely source Everything below is what sits behind that.

Something about particulates does not reconcile and I would like a second pair of eyes before I decide which half is wrong.

Two sources, both reputable, giving figures that cannot both be right unless they are measuring different quantities. My suspicion is that they are, and I cannot see how.

The opening post and I disagree about the size of the effect, not about the direction.

Peptide impurities that differ by a single residue are the hardest to resolve and the most likely to be biologically relevant, which is an unfortunate combination.

The opening post answers the question as asked. The question underneath it is different.

Speaking only to particulates 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.

A request rather than an answer: could whoever has the primary source for particulates post it? I have seen the claim three times this month and each version had lost a qualifier.

Oxidation at methionine and tryptophan: adds 16 per oxygen. Usually elutes earlier. Oxidation is common in storage, especially if the solution is exposed to light or if antioxidants are not present.

Noting that the question and the thing people usually mean by it are different.

I keep a log for particulates specifically because my memory of it turned out to be systematically wrong in one direction. Six weeks of notes cost nothing and settled it.

Following this. I have the same question and no better information than the first post.

Everything in post #6 holds. The case it does not cover is the one I have.

Particulates is one of those subjects where the general answer and the answer for a specific case diverge, and the thread will go in circles until someone says which one is being asked for.

Post #8 is the version of this I will quote in future. One addition.

Deamidation at asparagine and glutamine: adds 1 approximately. Frequently appears as a close-eluting pair. It is a chemical modification that occurs during storage.

On balance I think that is right, and I would not bet much on it.

On particulates, the part that usually goes wrong is that the question is asked as though it has one answer. It has a range, and the width of the range is the interesting bit.

If you can post the two or three numbers you are working from, several people here will check the arithmetic rather than argue about the conclusion.

Truncation products: fragments from incomplete synthesis or from degradation. They elute quite differently from the intact peptide because they are much smaller and have different hydrophobicity. They are usually well separated.

I would not lead a decision with this, but I would not ignore it either.

Building on post #9 rather than restating it.

Having read the whole particulates thread before replying: the question in the first post has not actually been answered yet, and three of us have answered a nearby one instead.

Helpful, and short, which on this subject is harder than long.

Truncation products are substantially lower in mass and usually well separated chromatographically, which makes them the easiest class to see and the least likely to be missed.