Nitration of angiotensin II by .NO2 radicals and peroxynitrite. .NO protects against .NO2 radical reaction.

To react with peptides, nitric oxide.NO has to be activated by oxidation, or by coupling with superoxide (O.-2) thereby producing peroxynitrite. In the course of.NO oxidation,.NO2 free radicals and N2O3 may be formed. Using gamma-irradiation methods, we characterized the products formed by these nitrogen oxides with angiotensin II. Angiotensin II is specifically nitrated at its tyrosinyl residue by.NO2 or peroxynitrite. Equimolecular amounts of each reagent in K+/Pi solutions at pH 7.4 led to 56% and 5% nitration yields, respectively. Nitrogen oxides produced by autoxidation of.NO, as well as.NO2 under.NO, reacted only with the arginine residue, giving a mixture of peptides containing citrulline, a N-(hydroxylamino-cyanamido-) instead of guanido group, and a conjugated diene derived from an arginine side-chain. However, nitrosation reactions by N2O3 occurred only when the initial concentration of.NO2 was 10 times that able to react with angiotensin II. Thus, in this case.NO appears to protect against.NO2 action.     

Plantlet Regeneration from Leaf Protoplast cultures of Japanese Butterbur

Protoplasts were isolated by enzyme digestion from leaf of Japanese butterbur (Petasites japonicus). The enzyme incubation mixture consisted of 4% (W/V)cellulase RS, 2% (W/V) hemicellulase, 1% (W/V) pectinase-dissolved Y-23 and polygalacturonase in a solution of 0. 5 mol/L mannitol at pH 5.7 . In the basic medium of 1/4 MS inorganic salts and 1/2 MS vitamins supplemented with 2 mg/L NAA, 0. 2–0. 5 mg/L BA, 0. 5 mol/L mannitol and 10 g/L sucrose, the cells divided luxuriantly. Regenerated plantlets were formed from callus after bud induction and root initiation.