The nitrite reductase (Nir) isolated from Pseudomonas chlororaphis DSM 50135 is a blue enzyme, with type 1 and type 2 copper centers, as in all copper‐containing Nirs described so far. For the first time, a direct determination of the reduction potentials of both copper centers in a Cu‐Nir was performed: type 2 copper (T2Cu), 172 mV and type 1 copper (T1Cu), 298 mV at pH 7.6. Although the obtained values seem to be inconsistent with the established electron‐transfer mechanism, EPR data indicate that the binding of nitrite to the T2Cu center increases its potential, favoring the electron‐transfer process. Analysis of the EPR spectrum of the turnover form of the enzyme also suggests that the electron‐transfer process between T1Cu and T2Cu is the fastest of the three redox processes involved in the catalysis: (a) reduction of T1Cu; (b) oxidation of T1Cu by T2Cu; and (c) reoxidation of T2Cu by NO₂^–. Electrochemical experiments show that azurin from the same organism can donate electrons to this enzyme.

Drug administration to experimental rodents is often invasive and stressful, thus reducing animal welfare and potentially confounding experimental results. Methods of oral drug delivery in which rodents cooperate voluntarily minimize stress, pain and morbidity. We herein describe a method for oral administration through voluntary intake of strawberry jam, developed for C57BL/6J mice. During a 3-day habituation period, animals were placed in individual cages once daily and presented with a drop of jam. Five days later, the jam was again offered with admixed drug. Mice ingested it in less than 5 min, with latency times below 1 min, confirming the suitability of the administration method.