The altered acidities of amino acid residues in folded proteins can be used as a good indication for the diverse functions, stabilities as well as folding-unfolding states of the proteins. Previously, our group has investigated the gas phase acidities of a series of cysteine containing peptides of four residues and longer. The results showed that the helix macrodipole might have a significant influence on the acidities of these peptides. In this work, the gas phase acidities of isomeric small cysteine containing di- and tri-peptides were investigated experimentally and computationally.
The gas phase acidities (ΔacidG) and related thermochemical quantities (ΔacidH and ΔacidS) were determined by using the extended Cooks kinetic method. A triple-quadruple mass spectrometer interfaced with an electrospray ionization source was employed for the study. The gas phase acidities of the N-terminal cysteine peptides (CysAla1,2NH2 and CysGly1,2NH2) were determined to be in the range of 321-323 kcal/mol, and the acidities of the C-terminal cysteine peptides (Ala1,2CysNH2 and Gly1,2CysNH2) were around 327- 331 kcal/mol. The results showed that theN-cysteine peptides were more acidic than the corresponding C-cysteine peptides, tri-peptides were stronger acids than di-peptides, and the acidities of cysteine-polyglycine peptides were close to those of the cysteine-polyalanine analogues.
Computational studies were performed through conformer search, geometry optimization, and energy calculations using the Spartan and the Gaussian suite of programs. The results showed that the low energy conformations of all deprotonated peptides were coils. The greater acidities of the N-cysteine peptides were likely due to the stronger hydrogen-bonding interactions in the deprotonated N-cysteine peptides, which efficiently stabilized the thiolate anions. The theoretically predicted acidities were in good agreements with the experimental results.
","abstract_html":"<p>The altered acidities of amino acid residues in folded proteins can be used as a good indication for the diverse functions, stabilities as well as folding-unfolding states of the proteins. Previously, our group has investigated the gas phase acidities of a series of cysteine containing peptides of four residues and longer. The results showed that the helix macrodipole might have a significant influence on the acidities of these peptides. In this work, the gas phase acidities of isomeric small cysteine containing di- and tri-peptides were investigated experimentally and computationally.</p><p> The gas phase acidities (Δ<sub>acid</sub>G) and related thermochemical quantities (Δ<sub>acid</sub>H and Δ<sub>acid</sub>S) were determined by using the extended Cooks kinetic method. A triple-quadruple mass spectrometer interfaced with an electrospray ionization source was employed for the study. The gas phase acidities of the N-terminal cysteine peptides (CysAla<sub>1,2</sub>NH<sub>2</sub> and CysGly<sub>1,2</sub>NH<sub>2</sub>) were determined to be in the range of 321-323 kcal/mol, and the acidities of the C-terminal cysteine peptides (Ala<sub>1,2</sub>CysNH<sub>2</sub> and Gly<sub>1,2</sub>CysNH<sub>2</sub>) were around 327- 331 kcal/mol. The results showed that theN-cysteine peptides were more acidic than the corresponding C-cysteine peptides, tri-peptides were stronger acids than di-peptides, and the acidities of cysteine-polyglycine peptides were close to those of the cysteine-polyalanine analogues.</p><p>Computational studies were performed through conformer search, geometry optimization, and energy calculations using the Spartan and the Gaussian suite of programs. The results showed that the low energy conformations of all deprotonated peptides were coils. The greater acidities of the N-cysteine peptides were likely due to the stronger hydrogen-bonding interactions in the deprotonated N-cysteine peptides, which efficiently stabilized the thiolate anions. The theoretically predicted acidities were in good agreements with the experimental results.</p>","abstract_has_math":false,"creators":["Shen, Jialin"],"institution":null,"degree_name":"Master of Science (M.S.)","degree_level":"Thesis - Pacific Access Restricted","degree_discipline":"Chemistry","degree_department":null,"school":null,"contributors":["Jianhua Ren"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-01-01T08:00:00Z","date_published":"2011-01-01T08:00:00Z","updated_at":"2026-07-24T05:36:46Z","subjects":["Acid-base chemistry","Oligopeptides","Physical Sciences and Mathematics"],"languages":[],"rights":[],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[]},"links":{"outbound_url":"https://scholarlycommons.pacific.edu/uop_etds/791","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Jianhua Ren"]},{"key":"dc:creator","label":"Author","values":["Shen, Jialin"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2018-06-29T09:08:39Z"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis - Pacific Access Restricted"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (M.S.)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Acid-base chemistry","Oligopeptides","Physical Sciences and Mathematics"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarlycommons.pacific.edu/uop_etds/791"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The altered acidities of amino acid residues in folded proteins can be used as a good indication for the diverse functions, stabilities as well as folding-unfolding states of the proteins. Previously, our group has investigated the gas phase acidities of a series of cysteine containing peptides of four residues and longer. The results showed that the helix macrodipole might have a significant influence on the acidities of these peptides. In this work, the gas phase acidities of isomeric small cysteine containing di- and tri-peptides were investigated experimentally and computationally.
The gas phase acidities (ΔacidG) and related thermochemical quantities (ΔacidH and ΔacidS) were determined by using the extended Cooks kinetic method. A triple-quadruple mass spectrometer interfaced with an electrospray ionization source was employed for the study. The gas phase acidities of the N-terminal cysteine peptides (CysAla1,2NH2 and CysGly1,2NH2) were determined to be in the range of 321-323 kcal/mol, and the acidities of the C-terminal cysteine peptides (Ala1,2CysNH2 and Gly1,2CysNH2) were around 327- 331 kcal/mol. The results showed that theN-cysteine peptides were more acidic than the corresponding C-cysteine peptides, tri-peptides were stronger acids than di-peptides, and the acidities of cysteine-polyglycine peptides were close to those of the cysteine-polyalanine analogues.
Computational studies were performed through conformer search, geometry optimization, and energy calculations using the Spartan and the Gaussian suite of programs. The results showed that the low energy conformations of all deprotonated peptides were coils. The greater acidities of the N-cysteine peptides were likely due to the stronger hydrogen-bonding interactions in the deprotonated N-cysteine peptides, which efficiently stabilized the thiolate anions. The theoretically predicted acidities were in good agreements with the experimental results.
"]},{"key":"dc:source","label":"Dc Source","values":["123"]},{"key":"dc:title","label":"Title","values":["The variation of the gas phase acidity of a cysteine residue in oligopeptides"]}]}],"canonical_facts":{"dc:contributor":["Jianhua Ren"],"dc:creator":["Shen, Jialin"],"dc:date.available":["2018-06-29T09:08:39Z"],"dc:description.abstract":["The altered acidities of amino acid residues in folded proteins can be used as a good indication for the diverse functions, stabilities as well as folding-unfolding states of the proteins. Previously, our group has investigated the gas phase acidities of a series of cysteine containing peptides of four residues and longer. The results showed that the helix macrodipole might have a significant influence on the acidities of these peptides. In this work, the gas phase acidities of isomeric small cysteine containing di- and tri-peptides were investigated experimentally and computationally.
The gas phase acidities (ΔacidG) and related thermochemical quantities (ΔacidH and ΔacidS) were determined by using the extended Cooks kinetic method. A triple-quadruple mass spectrometer interfaced with an electrospray ionization source was employed for the study. The gas phase acidities of the N-terminal cysteine peptides (CysAla1,2NH2 and CysGly1,2NH2) were determined to be in the range of 321-323 kcal/mol, and the acidities of the C-terminal cysteine peptides (Ala1,2CysNH2 and Gly1,2CysNH2) were around 327- 331 kcal/mol. The results showed that theN-cysteine peptides were more acidic than the corresponding C-cysteine peptides, tri-peptides were stronger acids than di-peptides, and the acidities of cysteine-polyglycine peptides were close to those of the cysteine-polyalanine analogues.
Computational studies were performed through conformer search, geometry optimization, and energy calculations using the Spartan and the Gaussian suite of programs. The results showed that the low energy conformations of all deprotonated peptides were coils. The greater acidities of the N-cysteine peptides were likely due to the stronger hydrogen-bonding interactions in the deprotonated N-cysteine peptides, which efficiently stabilized the thiolate anions. The theoretically predicted acidities were in good agreements with the experimental results.
"],"dc:identifier":["https://scholarlycommons.pacific.edu/uop_etds/791"],"dc:rights":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:source":["123"],"dc:subject":["Acid-base chemistry","Oligopeptides","Physical Sciences and Mathematics"],"dc:title":["The variation of the gas phase acidity of a cysteine residue in oligopeptides"],"thesis:degree_discipline":["Chemistry"],"thesis:degree_level":["Thesis - Pacific Access Restricted"],"thesis:degree_name":["Master of Science (M.S.)"]},"updated_at":"2026-07-24T05:36:46Z"}