Addition of CH2O to arginine--a theoretical study by ab initio method

Arginine is an acid possessing a guanidine side group which is protonated at all biological pHs, R-NH-C(=NH2+)-NH2. We have performed computations on the neutral species by the ab initio method using MINI and 6-31G(d) basis sets. Geometry optimization at the HF SCF level has also been carried out using the 6-31 G(d) basis set. We investigated the addition of formaldehyde to both the NH2- and H-N=C sites of the guanidine side group. The calculated exothermicities of the reactions with formaldehyde were found different for the above structures. We are planning to determine the energy barriers for these reactions in the near future.