Specific interaction of piperidine derivatives with human serum albumin

When the series of 4-substituted derivatives of 2,2,6,6-tetramethyl piperidine-I-oxide (TMPO) interacts with human serum albumin (HSA) in 0.01 M Na-acetate buffer, pH 5.6 in differential spectra there appears the intensive maximum at 232-235 nm characteristic of protein denaturation. It is suggested that specifics of nitroxyl binding with HSA is mainly determined by the conformational state of TMPO (twist or chair), since corresponding 4-nitro piperidines having other conformation result in the appearance of the band at 232.5 nm with a much lower intensity. It is recommended to take into account possible significant structural changes of albumins when studied by the spin label method using TMPO or its derivatives.