AAA | A | M.W. | H f | T peak | H peak | ΔM | QMS-17 | QMS-18 | QMS-44 | M gas | ΔM - M gas | H res |
|---|
| | | Da | kJ/mol | °C | kJ/mol | Da | mol/mol | mol/mol | mol/mol | Da | Da | kJ/mol |
|---|
Gly | G | 75 | −529 | 250 | 64 | 35 | 0,44 ± 0,01 | 1,27 ± 0,04 | 0,07 ± 0,00 | 34 | 1 | −172 |
Cys | C | 121 | −534 | 245 | 94 | 98 | 0,54 ± 0,05 | 0,37 ± 0,05 | 0,99 ± 0,07 | 59 | 39 | −27 |
Asp | D | 133 | −973 | 256 | 121 | 39 | 0,55 ± 0,04 | 1,92 ± 0,15 | 0,03 ± 0,00 | 45 | −6 | −473 |
Asn | N | 132 | −789 | 225 | 118 | 35 | 0,97 ± 0,03 | 1,11 ± 0,05 | 0,06 ± 0,00 | 39 | −4 | −451 |
Glu | E | 147 | −1010 | 201 | 89 | 20 | 0,25 ± 0,02 | 0,90 ± 0,08 | 0,00 ± 0,00 | 21 | −1 | −779 |
Gln | Q | 146 | −826 | 185 | 77 | 22 | 0,50 ± 0,02 | 0,53 ± 0,12 | 0,00 ± 0,00 | 18 | 4 | −675 |
Arg | R | 174 | −624 | 236 | 54 | 47 | 1,09 ± 0,04 | 0,87 ± 0,02 | 0,07 ± 0,01 | 37 | 9 | −334 |
His | H | 155 | −467 | 280 | 82 | 27 | 0,30 ± 0,01 | 1,01 ± 0,04 | 0,10 ± 0,00 | 28 | −1 | −169 |
- The three letter codes, and one letter codes, of the amino acids are listed in the first two columns. Their molecular weight is given in units of Dalton [Da] in the third column, the literature values [8] of their heat of formation, H f in [kJ/mol] in the fourth. Columns five and six refer to our experimental calorimetric data: the temperature where the maxima of the peaks occur, T peak, in centigrades, and the areas of the endothermic peaks, H peak in [kJ/mol]. The mass spectrometric data follow in columns seven to ten: ΔM in Dalton [Da] is the total weight loss in each peak, measured by TGA. QMS-17, given in units [mol/mol], is the mass found in the channel with molecular weight 17 Da, in all likelihood NH3. The unit is amount of mols in channel 17-Da per mol amino acid. The column QMS-18 lists the same parameter for the channel with molecular weight 18 Da, in all likelihood H2O. The column QMS-44 the same for the channel with molecular weight 44 Da, in all likelihood CO2. For example, the value 0.44 in the first line means that 0.44 mol NH3 per mol Gly passed through the mass spectrometer. The next column, titled M gas, is the calculated sum of the molecular weights found in the 17 Da, plus 18 Da, plus 44 Da channels, i.e. in the first line 34 Da=0.44×17+1.27×18+0.07×44 [Da]. Generally, if there are a, b and c mols of NH3, H2O and CO2, respectively, M gas= 17a + 18b + 44c. The penultimate column, ΔM-M gas, lists the difference of weight loss, ΔM measured by DTA and the total mass M gas, found as NH3, H2O and CO2. The smallness of ΔM-M gas assures that, within error limits, volatile products were only NH3, H2O and CO2. The notable exception is Cystein, which gives off another gas, see “Cysteine” subsections in “Raw data” and “Data analysis, amino acid by amino acid” sections of the text. The last column is the enthalpy of formation of the solid residue, which is the heat of formation H f(s) of the solid amino acid [8] minus the heats of formation used to form NH3, H2O and CO2. It is calculated as H res = H f−45a −242b −396c
