Chiral recognition in aqueous solutions: On the role of urea in hydrophilic and hydrophobic interactions of unsubstituted ?-amino acids

1996 ◽  
Vol 25 (9) ◽  
pp. 837-848 ◽  
Author(s):  
Salvatore Andini ◽  
Giuseppina Castronuovo ◽  
Vittorio Elia ◽  
Amelia Pignone ◽  
Filomena Velleca
Keyword(s):  
Amino Acids ◽  
Aqueous Solutions ◽  
Chiral Recognition ◽  
Hydrophobic Interactions

Chiral recognition in solution. Interactions of α-amino acids in concentrated aqueous solutions of urea or ethanol

1999 ◽  
Vol 77 (7) ◽  
pp. 1218-1224 ◽  
Author(s):  
Giuseppina Castronuovo ◽  
Vittorio Elia ◽  
Anna Pierro ◽  
Filomena Velleca
Keyword(s):  
Amino Acids ◽  
Aqueous Solutions ◽  
Chiral Recognition ◽  
Hydrophobic Interactions ◽  
Configuration Model ◽  
Excess Functions ◽  
Interaction Coefficients ◽  
Experimental Conditions ◽  
Concentrated Aqueous Solutions ◽  
The Difference

Enthalpies of dilution of the L and D forms of glutamine, citrulline, and phenylalanine in concentrated aqueous solutions of urea or ethanol were measured calorimetrically at 298 K. Glycine, urea, formamide, and phenol were also studied under the same experimental conditions, to get information about the behaviour of the zwitterion and of the functional group in the side chain of the cited amino acids when the concentration of the cosolvent changes. The derived pairwise enthalpic interaction coefficients for the three amino acids were rationalized according to the preferential configuration model. Indications are that, in concentrated urea, the coefficients for citrulline and glutamine are determined mainly by the interactions between the cosolvent and the hydrophilic groups in the molecule of the amino acids. For phenylalanine, coefficients are less positive than in water, because the presence of urea, which solvates preferentially the zwitterions, attenuates hydrophobic interactions between the benzene rings. In ethanol, coefficients for the three amino acid become negative or more negative than in water, because in this medium hydrophilic interactions are enhanced. Chiral recognition, namely the difference in the values of homo- and heterochiral interaction coefficients, was detected only for phenylalanine in urea. Hence, the nature of the cosolvent, influencing differently hydrophilic and hydrophobic interactions, can lead to the detection of chiral recognition also for those systems that, as phenylalanine, do not present this effect in pure water.Key words: α-amino acids, excess functions, molecular interactions, preferential configuration.

Chiral recognition in aqueous solutions at 25 °C. A calorimetric study of the interaction between enantiomeric α-amino acids of different alkyl chain length

1991 ◽  
Vol 69 (5) ◽  
pp. 794-797 ◽  
Author(s):  
Giuseppina Castronuovo ◽  
Vittorio Elia ◽  
Michela Magliulo
Keyword(s):  
Amino Acids ◽  
Aqueous Solutions ◽  
Chiral Recognition ◽  
Excess Enthalpy ◽  
Alkyl Chain ◽  
Alkyl Chain Length ◽  
Calorimetric Study ◽  
Experimental Uncertainty ◽  
Enthalpies Of Dilution

Cross-homo- and cross-heterotactic enthalpic coefficients, [Formula: see text] respectively, were determined at 25 °C, measuring the enthalpies of dilution of ternary aqueous solutions containing two different α-amino acids of the same or different chirality. Differences of about 200–300 J mol−2 kg between cross-homo- and cross-heterotactic coefficients were found, well beyond the experimental uncertainty. The role of the zwitterionic interaction, already proposed to explain the nature of chiral recognition, was strengthened. Key words: α-amino acids, excess enthalpy, chiral recognition.

Role of functional groups in determining interactions in ternary aqueous solutions of enantiomeric α-amino acids: a calorimetric study at 298 K

1999 ◽  
Vol 1 (24) ◽  
pp. 5653-5657 ◽  
Author(s):  
Giuseppina Castronuovo ◽  
Vittorio Elia ◽  
Marcella Niccoli ◽  
Daniela Strollo ◽  
Filomena Velleca
Keyword(s):  
Amino Acids ◽  
Aqueous Solutions ◽  
Functional Groups ◽  
Calorimetric Study

scholarly journals Characterization of the interaction between α2-macroglobulin and fibroblast growth factor-2: the role of hydrophobic interactions

2003 ◽  
Vol 374 (1) ◽  
pp. 123-129 ◽  
Author(s):  
Smitha MATHEW ◽  
Sanja ARANDJELOVIC ◽  
Wayne F. BEYER ◽  
Steven L. GONIAS ◽  
Salvatore V. PIZZO
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Hydrophobic Interactions ◽  
Heparan Sulphate ◽  
Fibroblast Growth ◽  
Amino Acid Peptide ◽  
Α2 Macroglobulin

Basic fibroblast growth factor (FGF-2) is important in development, wound healing and angiogenesis. The human plasma proteinase inhibitor α2-macroglobulin (α2M) binds to and regulates the biological activity of various growth factors, including FGF-2. FGF-2 binds specifically and saturably to native α2M and conformationally modified α2M (α2M∗); however, the KD for FGF-2 binding to α2M∗ is 10-fold lower. This study investigates the biochemical nature of the interaction between FGF-2 and α2M∗ and localizes a possible FGF-2 binding site in the α2M subunit. FGF-2 binding to α2M∗ was not affected by shifts in pH between 6.5 and 10; however, increasing temperature decreased the KD for this interaction. The binding affinity of FGF-2 for α2M∗ also increased with increasing ionic strength. These results are consistent with the hypothesis that hydrophobic interactions predominate in promoting FGF-2 association with α2M∗. Consistent with this hypothesis, FGF-2 bound to a glutathione S-transferase fusion protein containing amino acids 591–774 of the α2M subunit (FP3) and to a hydrophobic 16-amino-acid peptide (amino acids 718–733) within FP3. Specific binding of FGF-2 to the 16-amino-acid peptide was inhibited by excess transforming growth factor-β1. When the 16-amino-acid peptide was chemically modified to neutralize the only two charged amino acids, FGF-2-binding activity was unaffected, supporting the predominant role of hydrophobic interactions. FGF-2 presentation to signalling receptors is influenced by growth factor binding to heparan sulphate proteoglycans (HSPGs), which is electrostatic in nature. Our results demonstrate that the interactions of FGF-2 with α2M∗ and HSPGs are biochemically distinct, suggesting that different FGF-2 sequences are involved.

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