The distribution of this quantity is inferred from the shape of a type IV isotherm in the Barrett-Joyner-Halenda method. Materials with a “controlled” value of this quantity serve as solid supports for oligo·nucleotide synthesis. When expressed in a non-SI unit, a series of 3 materials with a “type A” structure have values of this quantity equal to 3, 4, or 5, depending on whether they have potassium, sodium, or calcium ions. In a typical SI unit, whether this quantity is less than 2, between 2 and 50, or greater than 50 determines if the material is described with the prefix (*) “micro,” “macro,” or “meso.” Beads with a fixed, small value of this quantity are used to separate proteins in size-exclusion chromatography. For 10 points, zeolite-based molecular sieves have values as low as 3 Angstroms for what quantity which characterizes the holes in a material? ■END■
ANSWER: pore size [or pore diameter; accept pore volume before “equal to 3”, prompt on hole size or hole diameter by asking “What’s the technical term for the holes?”; prompt on size or radius or diameter by asking “The size/radius/diameter of what features?” reject “porosity”] (The third sentence refers to 3 Angstrom, 4 Angstrom, and 5 Angstrom molecular sieves, while the fourth sentence refers to the classification of materials as microporous, mesoporous, or macroporous.)
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= Average correct buzz position