Hemoglobin function in the developing goat and sheep

Comparative studies of the blood of newly born goats and sheep have indicated a number of mechanisms which are responsible for a decreasing affinity for molecular oxygen in these developing animals during the first 40 to 60 days after birth.
The concentration of 2,3-DPG in the red cells of young goats increases four to sixfold during the first 3 to 4 days of life, and this increase is associated with a marked decrease in the cellular pH; 2,3-DPG does not bind to hemoglobins of goats and the decreased affinity for oxygen of goat blood at this period is apparently due to the lowered pH produced by the large increase of intracellular anions. Similar changes occur in young lambs.
After 15 to 20 days the changes of the dissociation curve are related more to structural differences between adult and fetal hemoglobins; cellular pH moves closer to the values of adult red cells. In goats of this age the predominate hemoglobins are those with β chains and these have dissociation curves shifted further to the right than other adult hemoglobins.
In young lambs Hb-C is found only in association with Hb-A but the amount present seldom exceeds 5 to 10%. The oxygen affinities of sheep Hb-A and Hb-C are identical but higher than that of sheep Hb-B.     

Conformational heterogeneity in polypeptide cardiac stimulants from sea anemones

High-resolution 1H NMR spectra at 300 MHz of the polypeptide cardiac stimulants anthopleurin-A and Anemonia sulcata toxin II reveal conformational heterogeneity in both molecules. The two conformations, manifest in a number of split 1H resonances, are in slow exchange over a wide range of pH and temperature. Heterogeneity affects a region of these molecules containing the structurally and functionally important Asp residues. By comparison with a homologous polypeptide Anemonia sulcata toxin I, which does not show this type of heterogeneity, it is suggested that the heterogeneity may originate in cis-trans isomerism of the Gly-40 to Pro-41 peptide bond.