Synthesis and Molecular Modeling of Cysteine- Polyalanine Peptides
Format
Oral Presentation
Abstract/Artist Statement
In connection with the investigations of the chemical properties of Thioredoxin family of enzymes, we studied a series of Cysteine-polyalanine peptides, Cys-Ala(3-7)-NH2. The peptides were synthesized through Solid Phase Peptide Synthesis (SPPS) using Rink Amide Resin. Coupling each amino acid was performed through DIC (Diisopropylcarbodiimide)/HOBt (1- Hydroxybenzotriazole) chemistry and deprotected using diethylamine/DMF. Each step-wise elongation cycle required a deprotection and coupling step. The peptides are cleaved from the Rink Amide Resin using Trifluoroacetic acid and purified using cold ether precipitation. The identity of the peptides is verified using the Varian 1200L triple-quadrupole mass spectrometer via Collision Induced Dissociation (CID). The results indicate that these peptides were produced in sufficient yields and purity for further mass spectrometry studies. Molecular Modeling was performed using the Gaussian 03 computational program. Molecular Modeling involves geometry optimization, calculation of the energetic properties, and prediction of the theoretical acidities of the peptide through isodesmic reactions. These calculations were performed using density functional theory (DFT) and AM1 semi-empirical methods. DFT was used for the single point energy calculations, and AM1 was used for optimization and enthalpy corrections. Molecular modeling results show that the helical conformations exist in both the neutral and the deprotonated peptides. Molecular Modeling also shows a trend of increasing the gas phase acidity as the peptide elongates for the Cys-Ala(3-7)-NH2 series. These results agree well with previous experimental gas phase acidity determinations on shorter cysteine-polyalanine peptides (Cys-Ala(3,4)-NH2).
Location
University of the Pacific, Classroom Building
Start Date
5-5-2007 9:00 AM
End Date
5-5-2007 12:30 PM
Synthesis and Molecular Modeling of Cysteine- Polyalanine Peptides
University of the Pacific, Classroom Building
In connection with the investigations of the chemical properties of Thioredoxin family of enzymes, we studied a series of Cysteine-polyalanine peptides, Cys-Ala(3-7)-NH2. The peptides were synthesized through Solid Phase Peptide Synthesis (SPPS) using Rink Amide Resin. Coupling each amino acid was performed through DIC (Diisopropylcarbodiimide)/HOBt (1- Hydroxybenzotriazole) chemistry and deprotected using diethylamine/DMF. Each step-wise elongation cycle required a deprotection and coupling step. The peptides are cleaved from the Rink Amide Resin using Trifluoroacetic acid and purified using cold ether precipitation. The identity of the peptides is verified using the Varian 1200L triple-quadrupole mass spectrometer via Collision Induced Dissociation (CID). The results indicate that these peptides were produced in sufficient yields and purity for further mass spectrometry studies. Molecular Modeling was performed using the Gaussian 03 computational program. Molecular Modeling involves geometry optimization, calculation of the energetic properties, and prediction of the theoretical acidities of the peptide through isodesmic reactions. These calculations were performed using density functional theory (DFT) and AM1 semi-empirical methods. DFT was used for the single point energy calculations, and AM1 was used for optimization and enthalpy corrections. Molecular modeling results show that the helical conformations exist in both the neutral and the deprotonated peptides. Molecular Modeling also shows a trend of increasing the gas phase acidity as the peptide elongates for the Cys-Ala(3-7)-NH2 series. These results agree well with previous experimental gas phase acidity determinations on shorter cysteine-polyalanine peptides (Cys-Ala(3,4)-NH2).