Kinetic Characterisation of the R and R2 Quaternary Structures of Oxyhemoglobins Arising from Different Effects of Inositol Hexakisphosphate on Their Reactions with Ellman's Reagent.

In a previously reported equilibrium study of the reaction of 5,5'-dithiobis(2-nitrobenzoate), DTNB, with various carbonmonoxyhemoglobins over the pH range 5.6 to 9, we obtained contradictory results on the influence of the allosteric effector inositol hexakisphosphate (inositol-P) on the DTNB reaction. For this reason, we replaced the carbonmonoxyhemoglobins with oxyhemoglobins and investigated the effect of inositol-P on the equilibrium and of their reactions with DTNB over the same pH range.

Electrochemical and Photoelectrochemical Immunosensors for the Detection of Ovarian Cancer Biomarkers.

Photoelectrochemical (PEC) sensing is an emerging technological innovation for monitoring small substances/molecules in biological or non-biological systems. In particular, there has been a surge of interest in developing PEC devices for determining molecules of clinical significance. This is especially the case for molecules that are markers for serious and deadly medical conditions.

R and R2 quaternary structures of carbonmonoxyhemoglobins: Differential effect of inositol hexakisphosphate on their affinity for Ellman's reagent.

The reaction of 5,5'-dithiobis(2-nitrobenzoate), DTNB, with hemoglobin sulfhydryl groups is linked to three negatively contributing Bohr effect groups: His2β is present in all avian hemoglobins but absent in some mammalian hemoglobins; His77β and His143β are absent in avian but present in nearly all mammalian hemoglobins. To probe the consequences of these differences, we determined the influence of inositol hexakisphosphate (inositol-P) on the DTNB affinities of avian and mammalian carbonmonoxyhemoglobins. Inositol-Pdecreases by two orders of magnitude the DTNB affinity of guinea pig hemoglobin, which has His2β and the R2 quaternary structure.

Bohr effect of human hemoglobin A: magnitude of negative contributions determined by the equilibrium between two tertiary structures.

We have measured the affinity of the CysF9[93]β sulfhydryl group of human deoxyhemoglobin and oxyhemoglobin for 5,5'-dithiobis(2-nitrobenzoate), DTNB, between pH ≈5.6 and 9 in order to understand the basis of the reported reduction of the Bohr effect induced by chemical modification of the sulfhydryl. We analyzed the results quantitatively on the basis of published data indicating that the sulfhydryl exists in two conformations that are coupled to the transition between two tertiary structures of hemoglobin in dynamic equilibrium.