[The effect of low concentrations of urea on immunoglobulin conformation from the data of differential spectrophotometry]. / Vliianie mocheviny nizkoi kontsentratsii na konformatsiiu immunoglobulinov po dannym differentsial'noi spektrofotometrii.

A reversible noncooperative conformational transition takes place in IgG molecule at 1 divided by 3 M urea solutions in the temperature interval 10 divided by 40 degrees C. This transition is registered as an increase of chromophores exposure and preceeds denaturation which happens at the same temperatures and with higher urea concentration.

[Complement fixation activity of immunoglobulin G in ethylene glycol solutions]. / Komplementfiksiruiushchaia aktivnost' immunoglobulina G v rastvorakh étilenglikolia.

Affinity of IgG to the first complement factor C1q was found out to increase in 10-30% glycol solutions. Analytical ultracentrifugation and turbidity data showed that IgG molecules do not aggregate at such concentrations of glycol. The complement-binding effect may be caused by a conformational transition in the IgG molecules.

[Effect of dehydration on interdomain interactions in immunoglobulin G and its fragments]. / Vliianie degidratatsii na mezhdomennye vzaimodeistviia v immunoglobuline G i ego fragmentakh.

Influence of urea on the structure of human IgG and isolated Fab and Fc-fragments was investigated by temperature-perturbation difference spectroscopy and circular dichroism. It was shown that 2M urea caused non-denaturational changes of IgG quaternary structure, localized in Fab-fragments. The same changes occur in solutions with ethylene glycol and glycerine as well. Apparently the main cause of these changes is dehydration. It is possible that the investigated effects model the conformational changes which appear in immunoglobulins after antigen binding.