The dissociation of some 111In chelates in the presence of transferrin and haemoglobin studied by PAC.
The interaction of [111In]Tris-chelates with protein molecules in aqueous solution at room temperature has been studied using time-integral and time-differential PAC. Increasing amounts of apo-transferrin were added to solutions of [111In]tropolonate, -acetylacetonate, -oxinate and -oxine sulphate, and of haemoglobin to [111In]tropolonate. The transfer of 111In from chelate to protein was monitored by time-integral PAC measurements. Analysis of these data in erms of stability constants showed that with added transferrin complete dissociation of each 111In chelate occurred with increasing protein concentration, the radiolabel being sequestered by the protein molecules. Confirmation of this was provided by time-differential PAC measurements at four tropolone:transferrin relative concentrations, and in the pure systems. A value for the first stability constant of transferrin is presented. Analysis of time-integral PAC data showed that added haemoglobin did not cause complete dissociation of [111In]tropolonate, a [111In]tropolone-haemoglobin complex being formed. Time-differential PAC studies of the [111In]tropolonate:haemoglobin and [111In]haemoglobin systems at 77 K and 295 K supported this conclusion, revealing quadrupole frequencies of 14.0 +/- 0.6 MHz in [111In]haemoglobin and 9.1 +/- 1.1 MHz in the mixed system.
D004355:Drug Stability; D006454:Hemoglobins; D007204:Indium; D009942:Organometallic Compounds; D015125:Oxyquinoline / Q000031:analogs & derivatives; D010422:Pentanones; D011868:Radioisotopes; D014168:Transferrin; D014334:Tropolone
D006454:Hemoglobins; D009942:Organometallic Compounds; D010422:Pentanones; D011868:Radioisotopes; D014168:Transferrin; D007204:Indium; C032950:indium oxine; C008790:acetylacetone; D015125:Oxyquinoline; D014334:Tropolone