Reduced Acid Dissociation of Amino-Acids at the Surface of Water.
We use surface-specific intensity vibrational sum-frequency generation and attenuated total reflection spectroscopy to probe the ionization state of the amino-acids l-alanine and l-proline at the air/water surface and in the bulk. The ionization state is determined by probing the vibrational signatures of the carboxylic acid group, representing the nondissociated acid form, and the carboxylate anion group, representing the dissociated form, over a wide range of pH values. We find that the carboxylic acid group deprotonates at a significantly higher pH at the surface than in the bulk.
Amolf , Science Park 102, Amsterdam 1098XG, The Netherlands.
Simona
0000-0003-0007-5507
S
Strazdaite
Amolf , Science Park 102, Amsterdam 1098XG, The Netherlands.
Konrad
0000-0002-6853-6325
K
Meister
Amolf , Science Park 102, Amsterdam 1098XG, The Netherlands.
Huib J
HJ
Bakker
D000388:Air; D000596:Amino Acids / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D013499:Surface Properties; D014732:Vibration; D014867:Water / Q000737:chemistry*
D000596:Amino Acids; D002264:Carboxylic Acids; D014867:Water