## 4 Solubilized COS Acting in Solution
### AATC (Alfa-Amino Acid Thiocarbamate)  
It has been suggested by [PERSON] et al. (2007, 2010, 2011) that alfa-amino acids might be such substances that would make it possible to restore the catalytic activity of COS in a liquid phase by forming an alfa-amino acid S-thiocarbamate, AATC, see Figure 4. In Figures 4-6, the formula representing AATC is marked with red-colored atoms:  
Figure 4: The N-H stretching vibration borrows energy from the COS molecule, resulting in a transfer of one H atom from the NH\({}_{2}\) group to the S atom. This invokes a bending of the previously linear OCS molecule.  
Figure 5: The decomposition of AATC to hydrogen sulfide and NCA.  
Figure 6: _Cont._The abovementioned authors [29], however, regarded the essential catalyst to be a decomposition product of the AATC. In that substance (NCA = N-carboxynhydride), however, the sulfur was completely lost, see Figure 5. Hence, the immense catalytic power stored in COS is gone, not supporting the interpretation of using NCA as the prime catalyst (intermediate).  
In order to judge the possibilities of an alfa-amino acid to take part in such a scheme, we report, in Table 5, some data from a recent paper on the subject [30].  
In the following, we consider a reaction between an alfa-amino acid and a molecule of carbonyl sulfide according to Figure 4: In this combination of species, we regard COS to be a reaction partner as well as a catalyst. Then, calculating the ratio between \(\gamma\) NH\({}_{2}\) of the amino acid (3189 \(\pm\) 69 cm\({}^{-1}\)) and \(\gamma_{3}\) of the COS molecule (2079 cm\({}^{-1}\), [2]), we obtain 3189/2079 = 1.534 \(\pm\) 0.033.  
This means a ratio = 3.2, indicating that three vibrational quanta from the COS source (catalyst) are needed to activate the N-H vibration with two quanta of the NH\({}_{2}\) vibration. Considering the relatively large experimental error in Table 5, we can state that Reaction (1)  
Figure 6: (**a**) Indicates the reaction between the H- atom of the SH- group of the AATC with the OH-group of the first amino acid, liberating a molecule of H\({}_{2}\)O; (**b**) shows that the remains of COS, now clad in the multi-atom product of reaction 4, uses what is left of its catalytic power to excite the N-H bonds in the second amino acid.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Amino Acid** & **Empirical Data** & **Calculated Ab Initio** & **Mean Value V\({}_{\text{NH2}}\)** \\ \hline l-Alanine & 3094 & 3310 & 3205 \\ \hline l-Phenyl-alanine & 3436 & 3187 & 3312 \\ \hline l-Aspartic acidid & 3141 & 3189 & 3165 \\ \hline l-Glutamic acid & 3020 & 3130 & 3075 \\ \hline Mean value & 3174 \(\pm\) 131 & 3204 \(\pm\) 53 & 3189 \(\pm\) 69 \\ \hline \end{tabular}
\end{table}
Table 5: NH\({}_{2}\) vibrations from [PERSON] and [PERSON] [31]. All data are in cm\({}^{-1}\). Only a selection of the calculations by the authors is used here.  
follows the conditions of SET: When 2 (or 4 or 6) \(\
u\) NH\({}_{2}\) quanta are activated, the molecule might react.  
In a similar way, the other reactant (bending of COS, \(\
u\) 2 = 527 cm\({}^{-1}\), [24]) might be activated by quanta from the catalyst, its sister molecule (COS). Here, the relevant ratio is 2079/527 = 3.945, with an error of 0.055, corresponding to 1.4%. Although the two frequency values of COS used here are supposed to be \"correct\" [19], the difference is of the order of the errors quoted for the amino acids. Thus, we can conclude that one quantum of the 2079 cm\({}^{-1}\) vibration corresponds to four quanta of the bending vibration of COS.  
Furthermore, there might be a slight change of size between quantum nr 1 and quantum nr 4 of the COS bending vibration. Hence, we can be allowed to infer that Reaction (1) is following the basic principles of SET.