Naslov
The Structure and Acidity of 20 alpha-Amino Acids

Autori
Vianello, Robert

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
2nd Central European Conference - Chemistry Towards Biology / - Seggau, 2004

Skup
2nd Central European Conference - Chemistry Towards Biology

Mjesto i datum
Leibnitz, Austrija, 26.09.2004. - 29.09.2004

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
acidity; amino acids; gas phase; triadic analysis

Sažetak
The deprotonation enthalpies (DPEs) of 20 alpha-amino acids are calculated by the MP2(fc)/6-311+G(d, p)//MP2(fc)/6-31+G(d) theoretical model. Comparison with available experimental data reveals an excellent agreement between the calculated and measured values as evidenced by absolute standard deviation of only 1.0 kcal/mol. It is shown that the most favorable site of deprotonation is the alpha-COOH group in all cases as intuitively expected with one notable exception - cysteine (C), where the deprotonation at SH group of side chain is more profitable by 2.0 kcal/mol. It appears that the aspartic acid (D) is the most acidic alpha-amino acid with estimated DPE value of 321.8 kcal/mol. The origin of its pronounced acidity is ascribed to the very strong hydrogen bonding taking place in the conjugate base. The trend of changes of acidity will be discussed in terms of a triadic analysis introduced recently. Since amino acids are conformationally very flexible molecules and possess many local minima, the equilibrium structures for all neutral alpha-amino acids as well as their deprotonated forms will be briefly commented upon.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA