Title

D-Cysteine Induced Acidity and Conformational Change in Cysteine-Polyalanine Peptides

Poster Number

16a

Lead Author Affiliation

Physical and Bioanalytical Chemistry

Lead Author Status

Doctoral Student

Second Author Affiliation

Chemistry

Second Author Status

Faculty

Introduction

It has been long-believed that there are only L- amino acids in human, until the astonishing observation of D-amino acid (DAA) as neuro transmitters in human central nervous system. Studies have shown that their presence is essential for human central nervous system to function correctly. Despite that the specific functions of individual DAAs are far from being understood, DAA containing peptides often displays biological activity higher than its all L-residue analogue. On the other hand, the presence of DAAs is associated with a variety of physical disorders. Understanding the functions of DAAs is essential for new therapeutic strategies. Characterizations at the fundamental molecular level are important to fully understand the functionality of DAAs.

Purpose

To characterize the effect of D-amino acids on the conformation and the gas-phase acidity of peptides.

Method

Using mass spectrometers, gas phase acidity of the peptides was measured. Using computational programs, such as Spartan and Gaussian, molecular modeling was carried out to determine the conformations and energies of the peptides. The resulting energies were used to calculate the theoretical gas-phase acidity and to find out the effect of D-cysteine on the peptide property.

Results

A series of tetrapeptides have been synthesized and studied. The gas-phase acidities have been determined experimentally and computationally. With the cysteine in the C-terminus, subtle acidity difference was found between AAAC-NH2 and AAAdC-NH2. With the cysteine on the N-terminus, CAAA-NH2 was determined to be more acidic than dCAAA-NH2.Structural analysis shows that the deprotonated CAAA-NH2 adopts a helical structure, while the deprotonated dCAAA-NH2 exists in an “ice cream cone” like structure.

Significance

The functionality of cysteine residues primarily depends on the acidity of the sidechain thiol group. The findings from our research help to understand how a D-cysteine can alter the acidity of a peptide via conformational change. The knowledge can be used as a guide to manipulate the functionality of designed peptides to achieve desired properties.

Location

DeRosa University Center

Format

Poster Presentation

Poster Session

Afternoon 1pm-3pm

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Apr 28th, 1:00 PM Apr 28th, 3:00 PM

D-Cysteine Induced Acidity and Conformational Change in Cysteine-Polyalanine Peptides

DeRosa University Center

It has been long-believed that there are only L- amino acids in human, until the astonishing observation of D-amino acid (DAA) as neuro transmitters in human central nervous system. Studies have shown that their presence is essential for human central nervous system to function correctly. Despite that the specific functions of individual DAAs are far from being understood, DAA containing peptides often displays biological activity higher than its all L-residue analogue. On the other hand, the presence of DAAs is associated with a variety of physical disorders. Understanding the functions of DAAs is essential for new therapeutic strategies. Characterizations at the fundamental molecular level are important to fully understand the functionality of DAAs.