2
0
2017
rod
est
0
journal
Original
Rodrigo, M. M.
Esteso, M. A.
Barros, M. F.
Verissimo, L. M. P.
Romero, C. M.
Suarez, A. F.
Ramos, M. L.
Valente, A. J. M.
Burrows, H. D.
Ribeiro, A. C. F.
J. Chem. Thermodyn.
2017
2020-09-29
The structure and diffusion behaviour of the neurotransmitter gamma-aminobutyric acid (GABA) in neutral aqueous solutions
GABA (gamma-aminobutyric acid) is a non-protein amino acid with important physiological properties, and with considerable relevance to the food and pharmaceutical industries. Particular interest has focused on its role as an inhibitory neurotransmitter in the mammalian cerebral cortex. In this paper, we report density and mutual diffusion coefficients of GABA in non-buffered aqueous solutions (0.001-0.100) mol dm-3 at 298.15 K. Under these conditions, 1H and 13C NMR spectroscopy and pH measurements show that it is present predominantly as a monomeric zwitterionic species. Diffusion coefficients have been computed assuming that this behaves as the binary system GABA/water. From density and intermolecular diffusion coefficients measurements, the molar volume, hydrodynamic radii, Rh, diffusion coefficients at infinitesimal concentration, D0, activity coefficients and the thermodynamic factors, FT, have been estimated. Within experimental error, the hydrodynamic volume calculated from this is identical to the molar volume obtained from density measurements. From the NMR spectra and literature data, it is suggested that this amino acid diffuses in aqueous solution as a curved, coil-like hydrated zwitterionic entity.
Diffusion coefficient
Density
Activity coefficient
gamma-Aminobutyric acid
Solutions
Taylor dispersion NMR
10.1016/j.jct.2016.09.014
104
110-117
1
InChI=1S/C4H9NO2/c5-3-1-2-4(6)7/h1-3,5H2,(H,6,7)
BTCSSZJGUNDROE-UHFFFAOYSA-N
4-aminobutanoic acid
.gamma.-aminobutyric acid
.omega.-aminobutyric acid
3-carboxypropylamine
4-aminobutanoic acid [GABA]
4-aminobutyric acid
Aminalon
Gamarex
Gammalon
piperidic acid
piperidinic acid
C4H9NO2
1
Commercial source
1
99
2
Stated by supplier
2
InChI=1S/H2O/h1H2
XLYOFNOQVPJJNP-UHFFFAOYSA-N
water
H2O
1
Commercial source
1
99.8
3
Estimated by the compiler
1
2
1
Principal objective of the work
AB
TRC
4/5/2017
1
Mass density, kg/m3
Vibrating tube method
Liquid
Direct value, X
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Liquid
1
Temperature, K
Liquid
2
Pressure, kPa
Liquid
1
298.15
5
2
101.3
4
1
997.046
6
1
0.31
2
1
1
2
1
Principal objective of the work
AB
TRC
4/5/2017
1
Mass density, kg/m3
Vibrating tube method
Liquid
Direct value, X
2
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Liquid
1
Temperature, K
Liquid
298.15
5
2
Pressure, kPa
Liquid
101.3
4
1
Molality, mol/kg
1
Liquid
1
0.10165
5
1
1000.097
7
1
0.311
1
0.07297
4
1
999.113
6
1
0.309
1
0.06297
4
1
998.944
6
1
0.306
1
0.05427
4
1
998.687
6
1
0.311
1
0.03823
4
1
998.069
6
1
0.309
1
0.01968
4
1
997.658
6
1
0.307
1
0.01088
4
1
997.389
6
1
0.309
1
0.00833
3
1
997.308
6
1
0.31
1
0.00517
3
1
997.203
6
1
0.31
1
0.00467
3
1
997.199
6
1
0.31
1
0.00258
3
1
997.127
6
1
0.31
1
0.00106
3
1
997.083
6
1
0.31
1
0
1
1
997.046
6
1
0.31
3
1
1
2
1
Principal objective of the work
AB
TRC
4/5/2017
1
Binary diffusion coefficient, m2/s
Taylor dispersion method
Liquid
Direct value, X
2
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Liquid
1
Temperature, K
Liquid
298.15
5
2
Pressure, kPa
Liquid
101.3
4
1
Molality, mol/kg
1
Liquid
1
0.001003
4
1
7.8e-10
3
1
0.031
1
0.005016
4
1
7.79e-10
3
1
0.048
1
0.01004
4
1
7.78e-10
3
1
0.057
1
0.02009
4
1
7.77e-10
3
1
0.02
1
0.03015
4
1
7.76e-10
3
1
0.02
1
0.05033
4
1
7.72e-10
3
1
0.039
1
0.101
4
1
7.65e-10
3
1
0.02