So we have Alamine, we have arginine, we have phenylalanine, we have glycine, we have aspartate, and we have glycine. So this is the beginning and this is our end. So if this nitrogen is not charged, then the phenol isotherthionate will react with this and bind to it, and this will label it. So the reaction basically forms this product, as shown. Now, if you want to know what the reaction mechanism is in this particular reaction, I'll link you above and you can check that reaction mechanism out. So what's the entire point of step one?