= J. A. Frier
{c}
\b[<J. A. Frier>] coauthored the 1977 study of human fetal <deoxyhemoglobin> with <Max Perutz>. The primary structure record 1FDH reports a human alpha/gamma tetramer examined by <X-ray diffraction> at $2.50\,\mathrm{\mathring A}$ resolution.<Structure of human foetal deoxyhaemoglobin by J. A. Frier and M. F. Perutz>[Primary citation, Biological Assembly, Macromolecules and Experimental Data]{ref} This is a verified structural-biology contribution; the published initials are retained without inferring an expanded identity from a deposition-name variant.
Comparing fetal and adult <hemoglobin> structures tests how changes in subunit composition alter local interactions. The paper's indexed abstract discusses differences at the binding region for <2,3-Bisphosphoglycerate>.<Structure of human foetal deoxyhaemoglobin by J. A. Frier and M. F. Perutz>[Indexed primary publisher abstract]{ref} Such a comparison can suggest why an effector binds differently. It does not make a static crystal structure a direct measurement of all physiological response rates or affinities.
An original coordinate example distinguishes <spatial resolution> from uncertainty in a derived distance. Suppose two modeled positions along one axis differ by $3.0\,\mathrm{\mathring A}$, with independent standard uncertainties $0.2\,\mathrm{\mathring A}$ each. The uncertainty of their signed separation is
$$
u_d=\sqrt{0.2^2+0.2^2}\,\mathrm{\mathring A}\approx0.283\,\mathrm{\mathring A}.
$$
If the coordinate errors have covariance $c$, the variance becomes $0.2^2+0.2^2-2c$. Shared model errors can therefore change the uncertainty of a relative separation. These are illustrative assumptions, not coordinate uncertainties reported for 1FDH.
A quoted diffraction resolution alone should not be substituted for either number in this example. It describes the experimental detail available to the model, while coordinate uncertainty also depends on data, occupancy, disorder and refinement. Frier and Perutz's structural result is valuable because it offers a molecular arrangement against which those broader mechanistic questions can be tested.
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