Toward the Atomic-Level Mass Analysis of Biomolecules 337


Figure 1. Mass spectrum of valine.


Figure 3. Mass spectra of glutamine (above) and glutamic acid (below).


ions in the detection sequence. When the SWCNT zone is analyzed, most detected ions are singly and doubly charged carbon ions (Nishikawa et al., 2009). In the molecule zone, the number of the carbon ions is small and the number of other ions increases. Leucine and methionine are successfully mass analyzed, revealing stable clusters such as COOH and HCNH2 (Nishikawa et al., 2009). Example of mass spectra of valine and proline are shown


Figure 2. Mass spectrum of prolone.


hydrochloric acid (HCl) and 62mg of Lys-Lys (a-L-Lysyl- L-Lysine) was dissolved in 50mL of 0.1N HCl. A small ball (~10–20 µm in diameter) of tangled long


SWCNTs was attached to aWtip with silver paste. Then, the tip was dipped in the solution of sample molecules.


RESULTS


SAP analysis proceeds by field evaporating SWCNTs and molecules from the surface layers. Although the SWCNT and molecule zones are randomly mixed, the SWCNT zone can be separated from the molecules zone by plotting the


Table 1. The ratios of the number of atoms detected by analyzing valine and proline.


HC N


Valine Ratio of atoms


Proline Ratio of atoms


11 0 5 1 2


Ratio of counted number of atoms 9.08 4.98 1 2.74 9


5 1 2 Ratio of counted number of atoms 9.35 5.11 1 2.03


Ghitamine Ratio of atoms


in Figures 1 and 2. Clusters of strongly bound carboxy, HCNH2, and HCNH groups are detected. No ions corre- sponding to pyrrolidine were detected. The number of atoms forming all mass peaks are


counted and listed in Table 1. The ratios of the counted number of H, C, N, and O atoms are very close to the ratios of the atoms forming the molecules. This indicates that the SAP analysis is not only qualitative, but also quantitative. The structures of glutamine (NH2–CO–CH2–


CH2–CHNH2–COOH) and glutamic acid (HO–CO–CH2– CH2–CHNH2–COOH) are very similar. The only differences are the amino group of glutamine and the OH group of glutamic acid. The mass difference of them is 1 amu. Figure 3 shows the mass spectra of glutamine and glutamic acid, the mass peaks were very similar. An unexpected finding was that the carboxy group had an extra hydrogen atom. Only difference between the two mass spectra was an extra


Table 2. The ratios of the number of atoms detected by analyzing glutamine and glutamic acid.


HC N 10 9 O 5 2 3


Ratio of counted number of atoms 9.07 4.98 2 3.76 Glutamic acid Ratio of atoms


5 1 4 Ratio of counted number of atoms 9.13 5.06 1 3.54


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164  |  Page 165  |  Page 166  |  Page 167  |  Page 168  |  Page 169  |  Page 170  |  Page 171  |  Page 172  |  Page 173  |  Page 174  |  Page 175  |  Page 176  |  Page 177  |  Page 178  |  Page 179  |  Page 180  |  Page 181  |  Page 182  |  Page 183  |  Page 184  |  Page 185  |  Page 186  |  Page 187  |  Page 188  |  Page 189  |  Page 190  |  Page 191  |  Page 192  |  Page 193  |  Page 194  |  Page 195  |  Page 196  |  Page 197  |  Page 198  |  Page 199  |  Page 200  |  Page 201  |  Page 202  |  Page 203  |  Page 204  |  Page 205  |  Page 206  |  Page 207  |  Page 208  |  Page 209  |  Page 210  |  Page 211  |  Page 212  |  Page 213  |  Page 214  |  Page 215  |  Page 216  |  Page 217  |  Page 218  |  Page 219  |  Page 220  |  Page 221  |  Page 222  |  Page 223  |  Page 224  |  Page 225  |  Page 226  |  Page 227  |  Page 228  |  Page 229  |  Page 230  |  Page 231  |  Page 232  |  Page 233  |  Page 234  |  Page 235  |  Page 236  |  Page 237  |  Page 238  |  Page 239  |  Page 240  |  Page 241  |  Page 242  |  Page 243  |  Page 244  |  Page 245  |  Page 246  |  Page 247  |  Page 248  |  Page 249  |  Page 250  |  Page 251  |  Page 252  |  Page 253  |  Page 254  |  Page 255  |  Page 256  |  Page 257  |  Page 258  |  Page 259  |  Page 260  |  Page 261  |  Page 262  |  Page 263  |  Page 264  |  Page 265  |  Page 266  |  Page 267  |  Page 268  |  Page 269  |  Page 270  |  Page 271  |  Page 272  |  Page 273  |  Page 274  |  Page 275  |  Page 276  |  Page 277  |  Page 278  |  Page 279  |  Page 280  |  Page 281  |  Page 282  |  Page 283  |  Page 284