Abstract
In order to characterize the thermodynamic property of cryoimmunoglobulin which is related to the temperature-dependent solubility change in aqueous solution, the fluorescence polarization measurement of 1-dimethylaminonaphthalene-5-sulfonyl (DNS) conjugated cryoimmunoglobulin (Jir) and monoclonal immunoglobulins in various solvent conditions were comparatively carried out using the steady state excitation method by altering temperatures from nearly 10 to 40℃, and the rotational relaxation times (Ph,) for these molecules were calculated according to the Perrin-Weber's equation using the values of polarization (P). The results indicated that the Ph value of DNS-Jir (170 nsec) was almost twice that obtained by myeloma protein (90 nsec) belonging to the same subclass with Jir, but was considerably shorter than that obtained by a soluble immune complex with a molecular weight equivalent to Jir dimer. These results suggested that the molecular structure of Jir protein was thermodynamically less-flexible than that of the myeloma proteins, and that the restricted intra-molecular flexibility might be responsible for the unusual property of cryoimmunoglobulin.
