Three Wells Is Not Three Experiments
Three wells from one dilution are three measurements of one thing. Why counting them as the sample size inflates confidence, and what actually counts as independent.
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How research peptide identity and purity are verified, and how to read the supporting analytical documentation.
Three wells from one dilution are three measurements of one thing. Why counting them as the sample size inflates confidence, and what actually counts as independent.
How MS/MS fragments a selected peptide ion into b and y series, how a sequence is read from the gaps between them, and the three things the spectrum cannot distinguish.
What size exclusion separates, why apparent molecular weight is not a mass measurement, and which aggregates it detects that a reversed-phase purity trace destroys.
Why 98.7% and 98.70% are different claims, where rounding belongs in a calculation, and how a rounding convention decides whether a borderline lot passes.
Right sequence, wrong mass. The increments that identify which side chain kept its group — and why arginine is the recurring offender.
A specification is an attribute, a method and an acceptance criterion. Where the criterion comes from, why the method must be capable of it, and what it leaves unconstrained.
How a protease digest confirms residue order, what sequence coverage means, and why a peptide map localises a modification that an intact mass cannot.
Weighing measures the vial. Absorbance measures the peptide. What the extinction coefficient is built from, a worked example, and the sequences where it simply does not work.
Peptides bind to glass, plastic, tips and filters. Why the proportion lost depends on concentration, why selective loss changes a measured purity, and what reduces it.
A p-value is a statement about data given a hypothesis, not the reverse. The four misreadings, why effect size is the number that matters, and the multiplicity problem.
An assignable cause independent of the value is the only defensible basis. Why statistical tests do not settle it, and why deciding in advance is the whole discipline.
Why a failing result cannot be replaced by a passing one, what an out-of-specification investigation is for, and the three things a retest is not.
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